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EXPERIMENTAL  PSYCHOLOGY 


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lENTAL  PSYCHOLOGY 

A  Manual  of  Laboratory  Practice 

BY 

EDWARD   BRADFORD  TITCHENER 

VOLUME  I 

QUALITATIVE   EXPERIMENTS 
PART  IL     INSTRUCTOR'S   MANUAL 

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V. 


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Sobaid  man  einmal  die  SeeU  ah  tin  Naturphanomtn  und 
du  SteUnUhre  als  eine  NtUurwusenscha/i  auffasst^  muss 
mmck  die  experimentelU  Metkode  auf  dies*  Wissenschaft  ihre 
voOe  Awwemdun^finden  kontun.  —  Wundt. 


THE    MACMILLAN    COMPANY 

LONDON:    MACMILLAN    k   CO^   LTa 
I918 

AU  rtgklt  rt$tr*t^ 


Copyright,  1901, 
By  the  MACMILLAN   COMPANY. 


Set  up  and  clectrotyped.     Published  March,  1901.     Reprinted 
September,  1910, 


Nortoooli  ^Pnss 

J.  8.  OnshiBg  Co.  —  Berwick  <Sc  Smith  Co. 

Norwood,  Mass.,  U.S.A. 


€o  iHu  JFrirntJS 

FRANK  ANGELL,  MAX  von  FREY,  AUGUST  KIRSCHMANN, 
OSWALD   KULPE  and  ERNST   MEUMANN 


PREFACE 

general  purpose  with  which  this  book  has  been  written 
is  sufficiently  indicated  by  its  title.  I  have  selected  a  number 
of  the  '  classical  *  experinients  of  Experimental  Psychology,  and 
have  tried  to  present  them  in  such  a  way  that  their  perform- 
ance shall  have  a  real  disciplinary  value  for  the  undergraduate 
student.  Within  this  general  purpose,  my  aim  has  been  two- 
fold. I  have  sought  to  show,  in  the  first  place,  that  psychol- 
ogy is  above  the  laboratory :  that  we  employ  our  instruments 
of  precision  not  for  their  own  sake,  but  solely  because  they 
help  us  to  a  refined  and  more  accurate  introspection.  And 
secondly,  just  as  in  my  Out  line  of  Psychology  and  Primer  of 
Psychology  I  gave  the  results  of  exj>erimentation  a  prominent 
place  in  the  psychological  system,  so  here  I  have  treated  the 
selected  experiments  not  as  separate  exercises,  but  as  points 
of  departure  for  systematic  discussion.  I  hope  that  the  book 
may  find  its  sphere  of  usefulness.  I  sorely  felt  the  need  of 
some  such  guide  when  I  entered  the  Leipzig  laboratory,  and 
I  have  felt  it  as  sorely  throughout  my  teaching  experience.  It 
is  needless  to  add  that,  although  eight  years  have  gone  to  its 
making,  the  Manual  falls  lamentably  short  of  its  ideal.  A  book 
in  conception  is  a  perfect  piece  of  workmanship :  the  book  that 
leaves  the  author's  hands  is  but  a  rough  approximation  to  the 
first  design. 

My  greatest  debt,  here  as  elsewhere,  is  to  Wundt.  I  was 
impelled  towards  experimental  psychology  by  dissatisfaction 
with  the  logical  constructions  of  the  English  school;  and  it 
was  Wundt  who  taught  me  the  essential  lesson  of  systematic 
introspection.  If  my  recent  writing  has  seemed  rather  to  be 
directed  against  Wundtian  doctrines,  that  is  but  the   natural 


viii  .    Preface 

reaction  of  a  pupil  who  cannot  swear  to  the  literal  teaching  of 
the  Master.  Next  to  Wundt  I  have  gained  most  from  the  work 
of  Hering  and  Stumpf. 

It  is  a  pleasant  duty  to  acknowledge  the  assistance  that  I 
have  received  in  the  preparation  of  the  Manual.  My  wife  has 
shared  the  labour  of  the  book  from  its  beginning.  I  am  in- 
debted to  my  sister,  Miss  L,  C.  Bedlow,  for  drawing  most  of 
the  Figures  of  Part  I.  My  colleagues,  Dr.  I.  M.  Bentley  and 
Dr.  G.  M.  Whipple,  have  given  freely  of  their  time  and  counsel. 
For  help  upon  many  special  points  I  have  further  to  thank 
Professors  B.  G.  Wilder  and  S.  H.  Gage,  of  Cornell  University, 
Professor  E.  C.  Sanford  and  Mr.  L.  N.  Wilson,  of  Clark  Uni- 
versity, Professor  J.  McK.  Cattell,  of  Columbia  University,  Pro- 
fessor W.  B.  Pillsbury,  of  the  University  of  Michigan,  and  Dr. 
E.  A.  McC.  Gamble,  of  Wellesley  College.^  Last,  not  least,  I 
must  set  here  the  name  of  John  Winslow,  —  good  man,  true 
friend  and  wise  physician,  —  to  whose  scientific  comradeship 
during  the  past  eight  years  I  owe  more  than  I  can  well  express, 
and  whose  recent  death  has  brought  to  me,  as  it  has  brought  to 
many  others,  a  sense  of  irreparable  loss. 

Cornell  Heights,  Ithaca,  N.V., 
November  i,  1900. 

1  The  Manual  is  a  product  of  the  laboratory,  and  embodies  the  work  of  a  long 
roll  of  students.  I  can  mention  but  a  few  names  here.  But  I  cannot  omit  a  word 
of  thanks  to  Miss  L.  Aldrich,  late  Scholar  in  Philosophy;  to  Dr.  W.  C.  Bagley,  of 
the  Department  of  Psychology;  to  Dr.  E.  I.  Conant,  of  the  New  York  Normal 
College;  to  Mr.  I.  MacKay,  Fellow  in  Philosophy;  to  Miss  M.  E.  Schallenberger, 
of  the  San  Francisco  State  Normal  School;  and  to  Dr.  T.  L.  Smith,  late  Honorary 
Fellow  in  Psychology. 


TABLE   OF   CONTENTS 


INTRODUCTION 

HINTS  TO    TUB  tXSTRrCTOR 

§  I.  Conduct  of  the  Course  in  General 

I  2.   QualtUtive  Work 

§  3.  The  Preparation  of  the  Instructor 
§  4.   The  Preparation  of  the  Student    . 

(  5.   Special  Directions 

§  6.   Published  Courses  in  Experimental  Psychology 


rACK 

xix 


xxiu 
xxiv 
xxix 
xxxi 


PART   I 

SENSATION,  AFFECTION,  ATTENTION  AND  ACTION 

CHAPTER   I.     VISUAL   SENSATION 


§  7.   Sensation 

§  8.   Visual  Sensation 

$  9.   Colour  Mixing 


Experiment  I 
Experiment  II 


§  10.   Campimetry 17 

f  1 1 .    Related  Experiments 26 

Experiment  III 

§  12.   Visual  Contrast 3° 

Experiment  IV 

§  13.   V^isual  After-images 37 


CHAPTER   II.     AUDITORY    SENSATION 

§  14.  Auditory  Sensation 

Experiment  V 
$15.   The  Phenomena  of  Interference  :  BeaU 


51 


55 


X  Table  of  Contents 

Experiment  VI 

§  1 6.   The  Pitch-difference  of  the  Two  Ears '^6* 

§  17.   Related  Experiments 65 

Experiment  VII 
§  18.   Combination-tones 66 

Experiment  VIII 
§  19.   Clang-tint 73 

Experiment  IX 
§  20.   Clang  Analysis  :  Overtones 75 

CHAPTER   III.     CUTANEOUS   SENSATION 

§  21.   Cutaneous  Sensation 81 

Experiment  X 
§  22.  Temperature  Spots 82 

Experiment  XI 
§  23.   Temperature  Sensitivity :  Area!  Stimulation         ,        .        ,        .      Z^ 

Experiment  XII 
§  24.   Pressure  Spots 92 

Experiment  XIII 
§  25.   Pain  Spots 94 

CHAPTER  IV.  GUSTATORY  SENSATION 

§  26.   Gustatory  Sensation 99 

Experiment  XIV 
§  27.    Distribution  of  Taste  Sensitivity  over  the  Tongue      ...       99 

Experiment  XV 
§  28.   The  Number  of  Taste  Qualities 105 

Experiment  XVI 
§  29.   Taste  Contrasts 106 


TadU  of  Contents  xi 

CHAPTER   V.     OLFACTORY   SENSATION 

rA(.K 

I  50.  Olftctory  Sensation 1 1  j 

EXPRRIMRNT  XVII 
S31.  The  Field  of  Smell 114 

Experiment  XVIII 
§32.   The  Olfactory  Qualities :  Method  of  Exhaustion  .        .119 

Experiment  XIX 
i  33.   The  Olfactory  Qualities :  Compensations*  Mixtures,  Contrasts  131 

CHAPTER   VI.     ORGANIC   SENSATION 
§  34.   Organic  Sensation 143 

Experiment  XX 
§35.   The  Sensation  of  Muscular  Contraction 143 

CHAPTER   VII.     THE   AFFECTIVE   QUALITIES 
§  36.    AflPection ,     149 

Experiment  XXI 
I  37.   The  Affective  Qualities :  Method  of  Impression    .        .         .         •     151 
I  38.   Alternative  Experiment 154 

Experiment  XXII 
§39.   The  Affective  Qualities:  Method  of  Expression,      (i)  Involun- 
tary Movement 158 

Experiment  XXIII 
I  40.   The  Affective   Qualities :     .Method   of  Expression.       (2)  Dyna- 

mometry 162 

§41.   Alternative  Experiment 167 

Experiment  XXIV 
§  42.  The  Affective  Qualities :  Method  of  Expression.     (3)  The  Ple- 

thysmograph 171 


xii  Table  of  Contents 

CHAPTER   VIII.     ATTENTION   AND   ACTION 
Experiment  XXV 

PACE 

§  43.  Attention 186 

Experiment  XXVI 
§  44.  The  Simple  Reaction •        •        •        .212 


PART   II 

PERCEPTION,  IDEA  AND    THE  ASSOCIATION  OF  IDEAS 

CHAPTER   IX.     VISUAL   SPACE   PERCEPTION 

§  45.   Perception 228 

§  46.   Visual  Space  Perception :  Preliminary  Exercises  ....    232 

Experiment  XXVII 
§  47.   Stereoscopy 257 

Experiment  XXVIII 
§  48.   The  Pseudoscope 295 

Experiment  XXIX 

§  49.   The  Geometrical  Optical  Illusions 303 

§50.   Explanations  of  the  MUller-Lyer  Illusion 321 

CHAPTER  X.     AUDITORY   PERCEPTION 

Experiment  XXX 
§51.  The  Degrees  of  Tonal  Fusion 329 

Experiment  XXXI 
§  52.   Rhythm 337 

Experiment  XXXII 
§  53.   The  Localisation  of  Sounds 356 


Tabu  of  Contents  xiii 

CHAPTER  XI.     TACTUAL  SPACE   PERCEPTION 

Experiment  XXXIII 
§54.  The  Localisation  of  a  Single  Point  upon  the  Skin  .     373 

Experiment  XXXIV 
§  55.  The  Discrimination  of  Two  Points  upon  the  Skin  -375 

Experiment  XXXV 
f  56.   Localisation  with  Changed  Position  of  the  Parts  Stimulated         .     383 

CHAPTER  XII.     IDEATIONAL  TYPE  AND  THE  ASSOCIATION 

OF   IDEAS 

Experiment  XXXVI 
f  57.   Ideational  Types 387 

Experiment  XXXVll 
f  58.   The  Association  of  Ideas 402 

APPENDICES 

L    Examination  Questions 421 

II.    Books  and  Periodicals 43° 

III.    Firms  recommended  for  the  Supply  op  Psychological 

Instruments 434 

List  op  Materials 437 

Index  of  Names 441 

Index  of  Subjects 44$ 


INDEX   OF   FIGURES 


FAOS 

7 
20 


67 
69 
71 
77 
83 
84 
88 
88 
93 


1.  Hering^s  Apparatus  for  testing  Colour  Blindness 

2.  Hering's  Indirect-vision  Colour  Mixer 

3.  Aubert  Diaphragm 

First  Difference-tones  within  the  Octave  f*-^ 

Second  Difference-tones  within  the  Octave  c^-(^ 

First  Difference- tones  for  the  Intervals  i :  2  to  i :  4  (f'-^) 

4.  Koenig  Resonator 

5.  Apparatus  for  keeping  Water  at  a  Constant  Temperature 

6.  Blix*  Apparatus  for  the  Investigation  of  the  Temperature  Sense 

7.  Practice  Maps  of  Temperature  Sensitivity :  Areal  Stimulation 

8.  Final  Map  of  Temperature  Sensitivity :  Areal  Stimulation 

9.  Hall's  Kinesimeter,  New  Model 

ID.   Maps  of  Hairs  and  Pressure  Spots;   Cold  Spots;   Warm  Spots; 

Pain  Spots 96,  97 

11.  Arrangement    of    Inductorium    for    Ordinary    Repeated    Shocks 

(Waller) 98 

12.  Normal  Breathing  Spots  (Zwaardemaker) 115 

13.  Map  of  the  Field  of  Smell  .116 

14.  Map  of  the  Field  of  Smell  117 

15.  The  Fluid-Mantle  Olfactometer  (Zwaardemaker)  .142 

16.  Arrangement  of  I  nductorium  for  Single  Unmodified  Shocks  (Waller)     144 

17.  Arm-rest  for  Kinesimeter  •     145 

18.  Curve  of  Affective  Reaction  to  Colours  •     » 53 

19.  Curve  of  Affective  Reaction  to  Colours 155 

20.  Records  of  Involuntary  Movement 160 

21.  Tridimensional  Movement  Analyser  (Sommer)  .161 

22.  Dynamometer  Records :  Normal 164 

23.  D)'namometer  Record :  Pleasant 1  ''-4 

24.  Dynamometer  Record :  Blank  Experiment 1  ^3 

25.  Dynamometer  Record :  Unpleasant 165 

XV 


xvi  Index  of  Figures 

no.  PAGH 

26.  Hand  Dynamometer  (Collin) 167 

27.  Mosso's  Ergograph 170 

28.  Catteirs  Ergograph 170 

29.  The  Ludwig-Baltzar  Kymograph 173 

30.  Universal  Smoking  Stand  (Zimmermann) 174 

31.  Stand  for  Spare  Drum 174 

32.  Varnishing  Tray  and  Drying  Rack 176 

33.  Marey  Tambour,  Writing-lever  and  Air-cock 177 

34.  Jacquet  Chronometer 178 

35.  Adjustment  of  Writing-point  to  Drum  Surface  (Langendorff)          ,  180 
36  Plethysmographic  Record :  Normal 181 

37.  Plethysmographic  Record :  Unpleasant 182 

38.  Mosso's  Sphygmomanometer 182 

39.  Lombard-Pillsbury  Finger  Plethysmograph 183 

40.  Von  Frey  Sphygmograph 183 

41.  Pneumograph  (Verdin) 184 

42.  Pneumograph  (Sumner) 184 

43.  The  Three  Faces  in  the  Moon 190 

44.  The  Apparatus  of  Goldscheider  and  Miiller 201 

45.  Arrangement  of  Experiment  for  Sanson's  Images  (Helmholtz)        »  235 

46.  Sanson's  Images  :  Candle  Images  (Helmholtz)        ....  236 

47.  Phacoscope  (Helmholtz) 236 

48.  Sanson's  Images :  Phacoscopic  Images  (Helmholtz)        .         .         .  237 

49.  Diagram  in  Explanation  of  Scheiner's  Experiment  (Helmholtz)      .  238 

50.  Von  Bezold's  Rings  (Helmholtz) 240 

51.  Astigmatism  Test  (Helmholtz) 241 

52.  Mouth  Board  and  Sighting  Mark  (Helmholtz)         ....  245 

53.  Projection  Screen  for  Experiment  on  Listing's  Law          .        .         .  248 

54.  Diagram  illustrating  False  Torsion  (Hering) 249 

55.  Double  Images 253 

56.  Double  Images 253 

57.  Early  Stereoscopes  (Wheatstone) 261 

58-60.   Diagrams  illustrating  Stereoscopic  Vision  (Ruete)  •  .         .         .  263 

61, 62.   The  Wheatstone  Stereoscope :  First  Model       ....  264 

63.  The  Optical  Principles  of  the  Wheatstone  Stereoscope  (Ruete)       .  264 

64.  The  Wheatstone  Stereoscope :  Final  Model 265 

65.  Slide  for  Wheatstone  Stereoscope  (Stevens)  .        ....  267 


!nd€X  of  Fibres  xvii 

na  rACB 

66.  The  Optical  Principles  of  the  Brewster  Stereoscope  (Ruete)  .        .  368 

67-69.   Stereoscopic  Dences  (Brewster) 271 

70.  Tdestereosoope  (Helmholtx) 272 

71.  Telestereoscope :  Later  Model 272 

72.  Tropostereoscope  (Ludwig) 273 

Stereoscopic  Slides :  Slide  i.  (Wheatstone) 274 

SUde  ii.  (Ruete) 275 

Slide  iii.  (Wheatstone) 275 

Slide  iv.  (Wheatstone) 275 

Slide  V.  (Martius-Matzdorff) 275 

Slide  vi.  (Martius-MatzdoHf) 275 

Slide  vii.  (Martius-Matzdorff ) 275 

Slide  viii.  (Martius-Matzdorff) 276 

Slide  ix.  (Martius-Matzdorff) 276 

Slide  X.  (Martius-Matzdorff) 276 

Slide  xi.  (Martius-Matzdorff) 277 

Slide  xii.  (Martius-Matzdorff) 277 

Slide  xiii.  (Martius-Matzdorff) 277 

Slide  xiv.  (Le  Conte) 277 

Slide  xviii.  (Hering) 278 

Slide  xix.  (Hering) 278 

Slide  XX.  (Hering) 278 

73.  Wheatstone^s  Figure 278 

Slide  xxi.  (Helmholtz) 279 

Slide  xxii.  (Wheatstone) 279 

Slide  xxiii.  (Martius-Matzdorff) 280 

Slide  xxiv.  (Wundt) 280 

Slide  XXV.  (Helmholtz) 281 

Slide  xxvi.  (Wheatstone) 281 

Slide  xxvu.  (Helmholtz) 281 

Slide  xxvui.  (Hering) 282 

SUde  xxU.  (Helmholtz) 282 

SUde  XXX.  (Helmholtz) 282 

Slide  xxxi.  (Martius-Matzdorif )      ...                ...  283 

74»  75-   Wundt's  Mirror  ExperimenU 285 

SUde  xxxii.  (Martius-Matzdorif) 287 

Slide  xxxui.  (Wundt) 288 


xviii  Index  of  Figures 

FIG  FAGB 

Slide  xxxiv.  (Wundt) 288 

Slide  XXXV.  (Wundt) 288 

Slide  xxxvi.  (Wundt) 288 

76.  Hering's  Binocular  Colour  Mixer 291 

77.  Pseudoscope  (Wheatstone) 295 

78.  Converting  Stereoscope  (Dove) 295 

79.  The  Optical    Principles    of   the    Total    Reflexion    Pseudoscope 

(Ruete) 296 

80.  Ewald's  Mirror  Pseudoscope 297 

81.  Stratton's  Mirror  Pseudoscope 297 

82.  Jastrow's  Perspectoscope 298 

83.  Wood's  Lenticular  Pseudoscope 299 

84.  The  Muller-Lyer  Illusion:  Delboeuf's  Figures  .  .  .  .321 
85-89.  The  MUller-Lyer  Illusion :  Brentano's  Figures  .  .  321,322 
90.  The  Muller-Lyer  Illusion :  Auerbach's  Figure  ....  322 
91-94.   The  Miiller-Lyer  Illusion  :  Brunot's  Figures     ....  323 

95.  The  Miiller-Lyer  Illusion  :•  Wundt's  Figure 324 

96.  The  Miiller-Lyer  Illusion  :  Einthoven's  Figures     ....  325 

97.  The  Miiller-Lyer  Illusion  :  Jastrow's  Figure 328 

98.  The  Curve  of  Fusion  Degrees  (Stumpf) 334 

99.  Rhythm  Apparatus 349 

100.  Double  Telephone  Arrangement  for  Sound  Localisation  (Matsu- 

moto) 371 

101.  Griesbach's  yEsthesiometer 382 

Schema  of  Train  of  Ideas 415 


INTRODUCTION:    HINTS   TO   THE 
INSTRUCTOR 

§  I.  Condact  of  the  Conne  in  General  —  This  Course  aims  at 
two  things:  first,  and  more  especially,  to  teach  the  student  to 
psychologist  and  secondly  to  acquaint  him  with  the  most  reliable 
methods  and  most  securely  established  results  of  experimental 
psychologfy.  Information  concerning  methods  and  results  can 
be  obtained,  without  much  trouble,  from  the  text-books.  But 
introspection  cannot  be  learned  from  books.  If  one  is  a  bom 
psychologist,  it  may  be  learned  from  the  experience  of  ordinary 
life  ;  and  learned  the  more  quickly,  if  this  experience  is  supple- 
mented by  reading  and  by  listening  to  lectures.  As  a  general 
rule,  however,  and  to  the  average  student,  an  understanding  of 
the  introspective  method  either  comes  by  way  of  the  laboratory 
or  does  not  come  at  all.  It  is  apt  to  come  somewhat  suddenly, 
after  a  longer  or  shorter  period  of  blind  work.  It  comes  under 
all  sorts  of  circumstances :  an  experiment  that  is  routine  drudg- 
ery to  one  man  may  be  illuminating  to  another,  just  as  a  cer- 
tain form  of  words  in  an  argument  or  proof  may  leave  one  hearer 
untouched  while  it  carries  conviction  to  another.^  Once  gained, 
it  is  never  lost :  one  can  no  more  forget  how  to  introspect  than 
one  can  forget  how  to  walk  or  swim. 

On  the  other  hand,  there  is  no  guarantee  that  introspection 
shall  be  learned  in  a  course  of  laboratory  practice.  Rules  may 
be  applied  and  definitions  memorised ;  examinations  may  be 
passed  and,  for  that  matter,  investigations  made;  while  the  stu- 
dent is  still  wholly  innocent  of  the  introspective  attitude.  Nor 
is  there  any  guarantee  that,  when  learned,  it  shall  always  be 
used  aright.  We  may  introspect  inadequately,  as  we  may  swim 
snatchily  or  walk  slouchingly.     It  is,  then,  of  the  very  greatest 

1  E.  Hering,  Zeits.  f.  Psytk.,  u,  1890,  19. 


XX  Introduction:  Hints  to  the  Instructor 

importance  that  the  Instructor  shall  teach  from  introspective 
knowledge,  and  not  from  book  knowledge  only.  No  one  denies 
that  acquaintance  with  the  methods  and  results  embodied  in  the 
monographic  literature  of  the  science  is  essential  for  the  psy- 
chologist, whether  he  be  teacher,  investigator  or  student.  But 
for  the  conduct  of  an  experimental  drill-course,  introspective 
familiarity  with  the  processes  which  are  to  be  examined  is  the 
one  condition  of  good  work.  If  time  allows,  therefore,  each 
experiment  should  be  performed  by  the  Instructor,  both  as  E 
and  as  O^  before  it  is  performed  by  the  members  of  his  class. 
In  any  case,  however,  the  experiment  should  be  gone  through 
in  shorthand,  —  all  the  manipulations  made,  and  the  method 
followed  out  briefly  in  all  its  turns  and  through  all  its  stages, 
—  and  enough  introspections  taken  to  furnish  a  control  of  the 
statements  of  the  text.  The  Instructor  should  know,  by  expe- 
rience, just  how  accurate  a  colour  equation  can  be,  and  just  how 
the  sensation  from  a  warm  spot  on  the  skin  'feels' :  he  should 
not  seek  to  acquire  this  knowledge  during  class  hours. 

On  the  other  hand,  it  is  probably  safe  to  say  that  no  single 
psychological  experiment  has  as  yet  been  worked  through  to 
the  bitter  end.  The  science  is  young :  Wundt's  laboratory  at 
Leipzig,  the  oldest  foundation  of  its  kind,  is  on  the  eve  of  its 
twenty-first  birthday  as  the  author  pens  these  lines.  And  the 
problems  are  so  numerous  and  so  patent  that  investigators  have 
been  tempted  to  range  widely  rather  than  to  concentrate  their 
energies  upon  single  issues.  An  intelligent  student  will  ask 
many  questions  in  the  course  of  the  year  to  which  experi- 
mental psychology  has  no  answer  ready.  Some  of  these  ques- 
tions will  take  the  form  of  minor  problems  which,  in  certain 
cases,  may  with  advantage  replace  the  set  experiments  of  the 
text. 

§  2.  Qualitative  Work.  —  The  experiments  of  this  Volume  are 
termed  '  qualitative,*  and  emphasis  is  laid  throughout  upon  *  quali- 
tative *  as  distinct  from  *  quantitative '  work.  It  is  important 
that  the  Instructor  accurately  understand  the  meaning  of  this 
distinction.  It  does  not  mean,  in  the  first  place,  that  the  experi- 
ments are  rough  and  inexact,  mere  approximations  to  the  'quanti- 
tative *  ideal,  indefinite  preliminary  tests  which  further  work  shall 


§  2.    Qualitative   Work  xxi 

make  definite.  Nor  does  it  mean  that  the  methods  employed 
are  rough  and  inexact,  incapable  of  formulation  in  numerical 
terms.  There  are.  it  is  true,  cases  in  which  the  experiments  of 
the  text  are  less  exact  than  could  be  wished,  and  in  which  the 
methods  arc  incompletely  worked  out :  these  defects  are,  how- 
ever,  due  to  exigencies  of  materials  or  time,  and  are  in  no  way 
inherent  in  the  qualitative  procedure.  What  the  distinction 
implies  is  rather  this :  that  the  student's  attention  is  directed 
not  to  the  *  How  much  ? '  or  the  *  How  well  ?  *  of  mental  func- 
tion, but  to  the  *  How  ? '  of  mental  structure.  The  problems  : 
How  quickly  can  one  idea  call  up  another }  how  many  impres- 
sions can  be  attended  to  at  once.'  how  small  a  difference  of 
colour-tone  can  be  perceived  ?  are  quantitative  problems.  The 
questions :  How  does  one  idea  call  up  another }  what  is  going 
on  in  the  calling-up  consciousness  }  —  What  happens  when  I  am 
attending-to  a  number  of  impressions  at  once }  how  do  the 
impressions  thus  attended-to  differ  from  other  impressions? 
what  are  the  characteristic  processes  of  the  attentive  conscious- 
ness ?  —  What  does  *  to  perceive  as  different '  mean  }  what  is  the 
process  of  comparison,  of  the  judgment  of  difference }  what 
are  the  contents  of  the  *just  different'  consciousness.' — these 
are  qualitative  questions. 

*  It  is,  however,  clear  that  in  experimental  psychology  the  terms 
'qualitative'  and  *  quantitative  '  are  not  mutually  exclusive.  If 
the  work  is  qualitative,  it  still  must  be  accurate ;  and  accuracy 
will  mean  the  introduction  of  measurement,  of  quantitative  for- 
mulation, at  various  stages  of  the  experiment.  The  qualitative 
course  of  an  after-image  is  not  fully  described  unless  the  series 
of  time-values  run  alongside  of  the  colour  changes.  We  cannot 
map  our  field  of  smell  aright  unless  we  set  a  time-limit  to  the 
stimulation.  We  cannot  turn  our  introspective  data  to  account 
for  the  '  How  ? '  of  sound  localisation  unless  we  have  the  errors 
and  the  directions  of  error  expressed  in  numerical  terms.  On 
the  other  hand,  if  the  work  is  quantitative,  it  must  still  be  sup- 
plemented by  qualitative  introspection,  or  the  figures  and  for- 
mulae are  barren.  Reaction  times  are  worth  very  little  without 
the  accompanying  analyses  of  the  action-consciousness ;  know- 
ledge of  the  range  or  limits  of  an  optical  illusion  is  worth  very 


xxii  Introduction :  Hints  to  the  Instructor 

little  without  a  qualitative  analysis  of  the  factors  upon  which  the 
illusion  depends.     And  so  on. 

We  may,  then,  modify  our  former  statement  a  little.  In 
qualitative  work,  we  may  say,  the  student's  attention  is  directed 
primarily  upon  the  *How.?',  and  the  *  How  much.?'  comes 
into  account  only  when  and  in  so  far  as  it  helps  towards  a  more 
exact  characterisation  of  the  *  How.'  In  quantitative  work,  the 
student's  attention  is  directed  primarily  upon  the  *  How  much  ? ', 
and  the* How.?* — though  it  must  be  taken  constant  account 
of  —  is  regarded  only  in  so  far  as  it  throws  light  upon  the 
answer  returned  by  consciousness  to  the  *  How  much  .? '.  The 
difference  will  work  out,  in  the  concrete,  to  mean  that  in  quali- 
tative work  the  methods  most  generally  followed  are  those  of 
exploration,  the  mapping  of  a  sense  field,  and  of  analysis  and 
synthesis,  the  tearing-apart  of  a  complex  into  its  constituent 
elements,  and  the  putting-together  of  the  elements  to  form  a 
known  complex ;  whereas,  in  quantitative  work,  the  methods 
most  generally  followed  are  the  'psychophysical  measurement 
methods'  (gradation  and  error)  and  the  chronometric  methods. 
Again,  however,  the  line  of  division  is  relative  only ;  the  author 
has  introduced  the  simple  reaction  into  this  part  of  the  Course, 
as  a  qualitative  experiment,  and  has  employed,  e.g.y  a  simple 
form  of  the  method  of  minimal  changes  in  an  experiment  upon 
tactual  localisation. 

There  can  be  no  doubt  that  the  atmosphere  and  spirit  of  the  psychological 
laboratories  have  changed  very  greatly  during  the  last  ten  years.  Oae  has 
only  to  compare,  e.g.,  the  work  of  E.  Meumann  on  the  time  consciousness 
with  the  earlier  work  proceeding  from  the  same  laboratory  and  published  in 
the  same  journal,  to  see  how  radical  this  change  of  aim  and  emphasis  has 
been.  The  old  quantitative  standpoint  is  now  almost  forsaken,  and  quali- 
tative analysis  not  only  has  a  literature  of  its  own,  but  is  coming  to  play 
a  larger  and  larger  part  in  the  investigations  described  above  as  quantita- 
tive. 

The  change  has  been  general,  as  movements  of  tendency  in  science  are 
likely  to  be,  and  all  the  leading  laboratories  have  done  their  share  towards 
bringing  it  about.  If,  however,  we  are  to  indicate  a  single  man,  as  representa- 
tive of  the  qualitative  point  of  view,  we  cannot  hesitate  to  name  G.  E.  MUller. 
In  all  Muller's  work  we  find,  alongside  of  a  consummate  mastery  of  quantita- 
tive method,  a  strenuous  insistence  upon  qualitative  analysis :  cf..,  e.g.,  the 
recent   monograph  by  L.   J.  Martin  and  G.   E.  MUller,   Zur  Analyse  der 


I  3.   Preparation  of  the  Instructor  xxiii 

UmitrukioiMtMpfmdlkkkHt :  txptrimumitiU  Beitragt.     Leipzig,  Barth,  1899. 

Mk.  7.50. 

The  author  may  add  that  he  insisted  on  the  importance  of  a  *  qualitative 
attitude*  to  the  studenU  who  took  this  Course  for  the  tirst  time  in  1892,  and 
that  experience  has  simply  ctinfimud  tlu-  vii-ws  which  he  thm  Inhl. 

§  3.  Tkt  Pnparation  01  tne  instructor.  —  The  iorcy;oing  Sec- 
tion raises  a  question  that  has  been  much  debated  among 
teachers  of  psychology :  the  question  whether  psychology  can 
be  taught  and  learned  without  a  pretty  thorough  previous  prepa- 
ration in  physics,  mathematics  and  physiology. 

It  stands  to  reason  that  the  director  of  a  laboratory  (or  his 
assistant  or  mechanician)  must  be  familiar  with  physics,  or  at 
least  with  certain  parts  of  physics,  if  the  work  of  the  laboratory  is 
to  go  on  at  all.  Tuning-forks  and  pendulums  and  induction  coils 
are,  in  the  first  place,  physical  instruments,  and  must  be  under- 
stood as  physical  instruments  if  they  are  to  be  used  in  the  teach- 
ing of  psychology.  If  the  laboratory  is  not  only  a  *  teaching  * 
but  also  a  *  research  *  laboratory,  a  good  knowledge  of  physics 
on  the  part  of  its  director  becomes  imperative. 

With  regard  to  mathematics  the  case  is  a  little  different. 
Two  statements  by  J.  McK.  Cattell,  made  in  the  course  of  the 
same  year,  are  interesting.  "Perhaps  we  [men  of  science] 
should  all  know  how  to  use  a  tool  as  fine  as  the  calculus" 
(Scuncc,  Feb.  4,  1898,  N.  S.,  vii.,  153):  and  "The  calculus  may 
ultimately  become  important  in  psychology,  but  as  yet  no  one 
has  accomplished  much  by  its  application "  {Psych.  Rev.,  v., 
1898,  658).  Except  that  he  would  make  the  second  sentence 
somewhat  more  hopeful,  the  author  fully  endorses  these  two 
remarks.  Knowledge  of  elementary  mathematics  is  part  of  a 
roan's  general  scientific  outfit :  but  one  may  work  a  lifetime, 
and  with  success,  in  psychology,  without  needing  the  knowledge.^ 

A  general  knowledge  of  the  architecture  of  the  brain  and  of 
the  functions  of  the  nervous  system,  and  a  somewhat  more 

*  It  IS,  of  course,  —  and  the  remark  it  so  obvious  that  the  author  would  hardly 
▼entnre  to  make  it,  were  it  not  justified  by  certain  recent  publications,  —  nothing  less 
tiHM  tenons  to  pretend  to  a  knowledge  of  mathematics  if  one  does  not  possess  such 
kaowledge  ;  to  introduce  into  one's  work  symbols  and  equations  which  are  not  a 
|Mft  of  one's  ordinary  mental  furniture. 


xxiv  Introduction:  Hints  to  the  Instructor 

special  knowledge  of  the  structure  and  functions  of  the  sense 
organs,  are  essential ;  while,  for  certain  kinds  of  research,  a  very 
thorough  knowledge  of  physiology  is  required.  We  have,  for- 
tunately, two  good  outlines  of  those  portions  of  physiology  which 
the  psychologist  must  know  in  Wundt's  Phys.  Psychologic  and 
Ebbinghaus'  Psychologic ;  James'  treatment  of  the  subject,  in 
the  Principles  of  Psychology ^  covers  only  a  part  of  the  ground. 
At  the  same  time,  the  student  must  be  led  clearly  to  understand 
that  nerve  physiology  is  not  psychology.  As  Hofler  says  : 
"  There  is  no  road  that  leads  to  psychology  from  metaphysics. 
But  neither  is  there  any  road  to  psychology  from  physiology." 
Where  it  is  necessary,  in  a  psychological  laboratory  course,  to 
take  time  for  physiological  matters, — as  will  probably  be  the 
case,  e.g.^  in  the  study  of  visual  space  perception,  —  the  Instructor 
should  sharply  distinguish  between  the  physiological  prelimina- 
ries and  the  psychological  problem. 

Students  who  enter  the  psychological  laboratory  with  little  or  no  physio- 
logical training  are  very  likely  to  manufacture  a  physiology  when  called  upon 
to  explain  a  psychological  fact.  "  You  say  that  1  touched  you  on  the  back  of 
the  hand.  How  do  you  know  that  I  touched.you  there  ?  ''  —  "  Why,  I  suppose 
there  is  one  set  of  nerves  for  the  back  of  the  hand  that  is  different  from  the 
other  sets  of  nerves."  This  sort  of  physiological  '  supposing '  m  psychological 
work  is  familiar  to  all  teachers  of  experimental  psychology.  It  must  be 
promptly  and  finally  suppressed. 

We  conclude,  then,  that  it  is  the  business  of  the  Instructor 
to  know  something  of  physics  and  physiology,  —  not  to  teach 
them,  by  any  means,  but  to  have  his  psychological  teaching 
infused  with  them.  If  he  know  something  of  mathematics,  so 
much  the  better ;  and  if  he  know  something  of  history,  and  lit- 
erature, and  general  biology,  so  much  the  better.  Always,  how- 
ever, he  must  be  careful  to  make  it  clear  to  the  student  where 
these  other  sciences  end  and  the  science  of  psychology  begins. 

§  4.  The  Preparation  of  the  Student.  —  The  present  Course 
implies  a  preliminary  course  of  lectures  on  general  psychology, 
such  a  course,  eg.,  as  is  laid  down  in  the  author's  Outline  of 
Psychology.  Alongside  of  this  preliminary  course  should  run 
courses  in  general  physics  and  general  physiology  (with  labora- 
tory work),  and  in  French  and  German.     Special  work  in  nerve 


§  4-   PripamtioH  of  thi  Student  xxv 

physiology  and  in  physics  (light,  sound  and  electricity)  should 
be  taken  concomitantly  with  this  Course.     The  author  has  found 
it  advisable,  in  this  second  year  of  work,  to  give  a  short  reading- 
course  in  French  and  German  psychology,  a  technical  supple- 
nent  to  the  general  language  courses.     Finally,  the  laboratory 
:rill  should  be  followed  by  a  year's  lecture  course  in  Systematic 
i'sychology,  during  which  the  student  works  over  for  himself, 
X  first  hand,  certain  portions   of   the  monographic  literature. 
Laboratory  work  —  practice  or  the  investigation  of   questions 
arising  in  the  course  of  practice  —  is  still  continued.      After 
::iese  three  years  of  training  come  the  work  of  the  Seminary, 
and  research  proper. 

The  qualities  that  make  a  successful  student  have  been  enu- 
merated in  the  text.  It  is  part  of  the  Instructor's  business  to 
cultivate  these  qualities  in  natures  that  already  possess  them, 
and  to  induce  them  —  so  far  as  they  can  be  induced  by  training 
—  upon  temperaments  to  which  they  are  naturally  foreign. 
And  this  means  that  the  Instructor  must  make  a  study  of  men- 
tal types.     A  few  words  may  be  said  upon  the  topic  here. 

The  students  that  enter  the  laboratory  may  be  classified 
roughly  as  *  objective '  and  *  subjective  *  in  type.  L.  W.  Stem 
I  L'cber  Psychologic  dcr  individucllcn  Diffcrcnzcn,  Leipzig,  1 900, 
•>)  ff.)  gives  the  following  description  of  the  two  natures.  The 
objectively-minded  observer  "  yields  himself  as  passively  as  pos- 
sible to  the  impression,  is  of  a  contemplative  turn,  follows  with 
great  exactness  the  variations  of  the  external  stimulus ;  he 
delays  his  reaction  until  he  has  arrived  at  a  confident  judgment." 
The  subjectively-minded,  on  the  contrary,  "is  constantly  expect- 
ing something,  is  easily  led  to  react,  by  prepossession  or  impa- 
tience, before  he  has  attained  to  full  certainty  by  means  of 
perception  pure  and  simple  ;  he  has  in  general  a  strong  ten- 
dency to  motor  discharge ;  the  moment  of  perception  is  deter- 
mined not  so  much  by  the  nature  of  what  is  perceived  as  by  a 
subjective  periodicity  (rise  and  fall)  of  psychical  activity."  T.  L. 
Bolton  (Amer.  Jotim.  of  Psych.,  vi.,  1893,  208  ff.)  gives  a  classi- 
fication which,  by  a  little  rearrangement,  may  be  squared  with 
this.     The  objectively-minded  students,  he  say.n,  "take  a  mod- 


xxvi  Introduction :  Hints  to  the  Instructor 

erately  critical  attitude.  They  are  concerned  in  others*  opinions 
in  so  far  only  as  other  opinions  suggest  different  points  of  view. 
They  give  their  own  opinions  when  they  have  considered  all  the 
phases  of  the  experiment  that  are  suggested  to  them.  They  are 
unconcerned  about  the  outcome  of  the  experiment.  They  are  not 
dogmatic ;  they  might  have  a  different  opinion  under  different 
circumstances  or  with  further  consideration.  In  the  light  of  the 
evidence  before  them,  they  hold  to  a  certain  view."  The  sub- 
jectively-minded fall  into  two  groups.  "  The  first  includes  those 
persons  who  yield  immediately  to  any  suggestion  that  is  offered. 
This  attitude  results,  then,  from  a  social  practice.  In  society, 
people  do  not  wish  to  antagonise  others.  They  instinctively 
give  assent  to  any  opinion.  In  an  experimental  investigation, 
if  the  operator  will  just  give  the  slightest  hint  of  his  theory  or 
preference,  they  will  add  the  weight  of  their  opinions.  If  the 
operator  leads  them  into  giving  an  opinion  which  is  opposed  to 
his  theory,  *  consistency  becomes  a  jewel ' ;  they  stick  to  their 
opinion  stoutly.  If  the  experiment  shows  plainly  that  they  are 
wrong  and  it  is  preposterous  to  hold  such  a  view,  they  make  a 
compromise  with  their  former  position,  and  try  to  excuse  them- 
selves for  having  been  led  astray.  They  remain  respectfully 
silent  afterward  and  avoid,  if  possible,  giving  an  opinion.  If 
they  are  forced  to  make  a  judgment,  they  do  it  tentatively ; 
they  are  not  sure.  Of  a  number  of  possible  views  they  cannot 
make  up  their  minds  which  is  the  correct  one.  They  generally 
hair-split  until  they  find  out  some  one's  opinion,  and  then  agree 
with  that."  The  second  "class  includes  those  persons  who  are 
excessively  critical.  They  incline  always  to  an  opposite  view. 
The  experiment  is  not  conducted  properly  to  suit  them ;  they 
are  not  in  their  best  mood  for  judgment.  They  are  sure  to  take 
ground  against  some  one's  opinion.  If  they  cannot  get  any 
clue  to  others'  opinion^  they  are  doggedly  silent  or  quibble,  and 
refuse  to  answer  except  they  qualify  their  answers  to  such  an 
extent  that  the  answer  means  nothing.  This  class  of  subjects 
is  intellectually  dishonest.  If  they  are  compelled  to  answer, 
they  indulge  in  hair-splitting  differences  between  their  opinions 
and  those  of  some  others." 

Bolton,  writing  as  investigator  and  not   as   teacher,  passes 


{  4-  Pnp€trutioH  of  tki  Studtnt  xxvii 

severe  judgment  upon  the  subjective  type.  And  it  is  true  that 
there  are  persons  who,  from  laziness,  from  some  form  of  inca- 
pacity, or  from  ingrained  prepossession,  are  unfitted  for  psycho- 
logical  work.  If  such  persons  find  their  way  into  the  laboratory, 
however,  they  find  their  way  out  again,  in  the  course  of  the 
first  fortnight.  On  the  other  hand,  we  rarely,  if  ever,  meet  with 
a  pure  type  ;  the  rule  is  that  the  objective  or  the  subjective  atti- 
ide  is  dominant  in  the  total  character.  Most  natures  are  suffi- 
ently  objective  to  afford  a  foothold  to  training ;  and  for  the 
^tudent  who  is  willing  to  see  the  matter  through,  training  will 
accomplish  wonders.  Set  a  man  to  work  for  a  year :  hold  him 
strictly  to  the  work,  insist  that  he  be  thorough  :  show  him  his 
faults  unflinchingly,  in  all  their  glaringness  ;  at  the  same  time, 
work  with  him,  sympathetically,  as  ready  to  encourage  as  to 
blame :  fit  your  praise  and  blame  alike  to  his  character  and  dis- 
position :  and,  though  you  have  not  changed  his  nature,  you  will 
have  wrought  a  very  considerable  change  in  his  methods  and 
attitudes.  Few,  if  any,  of  the  students  who  take  this  Course  in 
a  given  year  will  become  psychologists.  But  the  Instructor  can 
cflFect  this  much,  —  that  all,  when  they  leave  the  laboratory  at 
the  end  of  the  year,  carry  away  with  them,  besides  some  little 
knowledge  of  experimental  psychology,  the  habit  of  concentrated 
and  continuous  work. 

No  means  must  be  neglected  that  will  assist  towards  this  end. 
Cautions  and  injunctions  in  plenty  are  given  in  the  text.  But 
cautions  and  injunctions,  even  if  understood,  are  not  necessarily 
efifective.  It  may  be  taken  for  granted  that  the  student  who 
comes  into  the  laboratory  for  the  first  time,  whatever  his  prepa- 
ration may  have  been,  does  not  realise  how  much  he  has  to 
unlearn,  how  g^eat  is  the  gulf  that  divides  popular  from  scien- 
tific psychology.  Moreover,  the  student  of  psychology,  as  we 
have  him,  has  too  often  had  no  laboratory  training  of  any  sort. 
The  author  has,  therefore,  been  accustomed  to  supplement  the 
directions  of  the  text  by  painting  the  reverse  of  the  picture. 
No  ofifence  will  be  given  (and  the  giving  of  offence  would  defeat 
the  whole  object  of  the  Instructor)  if  the  situation  is  handled 
tactfully  and  good-naturedly ;  and  a  great  deal  may  be  accom- 


xxviii  Introduction:  Hints  to  the  Instructor 

plished,  at  one  stroke,  that  could  otherwise  have  been  attained 
only  slowly  and  with  difficulty. 

Haw  to  fail  in  Laboratory  Work 

(i)  Assent  readity,  and  with  an  air  of  complete  intelligence,  to  all  that  the 
Instructor  says.  Make  no  effort  to  understand  his  explanations  yourself,  but 
trust  to  your  partner  for  the  conduct  of  the  experiment. 

(2)  Do  not  accept  any  general  explanation,  under  any  circumstances. 
Cherish  the  belief  that  your  mind  is  different,  in  its  ways  of  working,  from  all 
other  minds,  and  that  you  must  be  individually  treated. 

(3)  See  yourself  in  everything.  If  the  Instructor  begin  an  explanation, 
interrupt  him  with  a  story  of  your  childhood  which  seems  to  illustrate  the 
point  that  he  is  making.  If  he  is  formulating  a  law,  interrupt  him  with  an 
account  of  some  exception  that  has  occurred  within  your  own  or  your  friends' 
experience.  Go  into  the  minutest  detail.  If  the  Instructor  incline  to  reject 
your  anecdotes,  argue  the  matter  out  with  him  in  full. 

(4)  Call  upon  the  Instructor  at  the  slightest  provocation.  If  he  is  busy, 
stroll  about  the  laboratory  until  he  can  attend  to  you.  Do  not  hesitate  to 
offer  advice  to  other  students,  who  are  already  at  work. 

(5)  Look  very  critically  at 'the  instruments  that  are  put  into  your  hands. 
Point  out  their  defects  to  the  Instructor,  and  suggest  improvements.  Offer  to 
spend  the  next  few  laboratory  hours  in  the  workshop,  getting  out  a  better 
appliance. 

(6)  Never  lose  sight  of  the  greater  questions  of  the  science  in  the  petty 
routine  of  experimentation.  If,  e.g.^  the  Instructor  is  explaining  the  use  of 
the  campimeter,  ask  him  whether  experimental  psychology  is  not  materialistic 
in  tendency,  or  if  he  thinks  that  the  results  of  experimental  psychology  are  of 
value  for  education. 

(7)  If  you  are  balked  by  an  introspective  problem  that  your  partner  has 
solved,  either  say  that  of  course  you  had  thought  of  that,  but  that  it  seemed  too 
trivial  to  mention,  or  fall  back  upon  the  uniqueness  of  your  mental  constitu- 
tion. Tell  the  Instructor  that  the  science  is  very  young,  and  that  what  holds 
of  one  mind  does  not  necessarily  hold  of  another.  Support  your  statement 
by  anecdotes. 

(8)  Work  as  noisily  as  possible.  Converse  with  your  partner,  in  the  pauses 
of  the  experiment,  upou  current  politics  or  athletic  records.  Get  thoroughly 
roused  up  and  excited  before  you  proceed  with  your  work. 

(9)  Do  not  take  the  work  seriously.  Explain  frankly,  when  you  enter  the 
laboratory,  that  you  have  no  belief  in  the  methods  and  results  of  experi- 
mental psychology,  but  that  you  like  to  know  what  is  going  on  in  the  various 
departments. 

Or,  as  an  alternative  rule :  Explain,  when  you  enter  the  laboratory,  that 
you  have  long  been  interested  in  experimental  psychology,  and  that  you  are 
overjoyed  to  have  found  the  present  opportunity  of  studying  it.      Describe 


§  5-    Spiciai  Dirfctions  xxix 

the  telepathic  experiences  or  aooounu  that  arouMd  ]roar  interett;  atk  the 
Instructor  if  he  hat  read  io-and-90*i  recent  paper  in  to-and-to,  and  expreM 
disappointed  surprise  when  he  replies  (as  he  will)  that  he  has  not. 

(lo)  Make  it  a  rule  always  to  be  a  quarter  of  an  hour  late  for  the  labora- 
^>r]r  exerdaes.  In  this  way  you  throw  the  drudger>-  of  preliminar)*  work  upon 
>  our  partner,  while  you  can  still  take  credit  to  yourself  for  the  regularity  of 
your  dass  attendance. 

The  author  has  never  found  the  paragon  who  obeyed  all  these 
precepts.  Diligent  attention  even  to  one  or  two  of  them  will, 
however,  be  enough  to  secure  the  failure  required. 

§  5.    SpaeUl  Direotioiu.  —  A  word  may  be  added  upon  some 
special  points,    (i)  The  Instructor  should  be  careful  not  to  sug- 
gest, by  word  or  manner,  that  a  certain  result  is  expected  from 
a  certain  experiment.     Students  in  the  early  stages  of  training 
are  exceedingly  suggestible.     The  Questions  appended  to  the 
experiments  of  Part  I  have  been  chosen  with  this  fact  in  mind. 
They  may,  however,  have  a  suggestive  influence.     If  the  In- 
structor has  any  suspicions  on  the  matter,  he  should  find  an 
occasion  to  insist  to  the  student  that  the  Questions  are  wholly 
objective  and  neutral  in  character,  and  that  a  negative  answer  is 
as  likely  to  be  right  as  a  positive,     (ii)  The  "  Related  Experi- 
ments," briefly  outlined  below,  should  be  worked  out  (if  they 
are  to  be  performed  at  all)  as  carefully  and  under  as  strict  con- 
ditions as  the  regular  experiments  of   the  Course,      (iii)  The 
Instructor  should  see  that  the  note-books  are  'written  up'  at 
frequent  intervals.     It  is  not  only  that  the  work  soon  accumu- 
lates.    A  student  is  compelled,  if   he  is  writing  a  week  after 
the  event,  to  think  himself  back  into  the  conditions  of  the 
experiment ;  he  has  lost  the  freshness  and  reality  of  the  expe- 
rience ;  and  his  record  suffers  in  consequence,    (iv)  The  author 
has  said  in  the  text  that  introspections  should  be  definitely 
and  concretely  worded.      A  sharp  distinction  must  be  drawn 
between  concrete  phrasing  and  picturesque  or  pictorial  phrasing. 
The  more  concrete  the  report,  the  more  closely  does  it  tally 
with  the  experience.     But  a  picturesque  report  —  a  report  which 
may  seem,  at  first  reading,  to  reproduce  the  warmth  and  inti- 
macy of  the  experience  as  no  other  form  of  words  could  do  — 
will  generally  be  found,  on  deeper  study,  to  rest  upon  some 


XXX  Introdtiction :  Hints  to  the  Instructor 

superficial  analogy,  and  to  contain  no  more  of  real  introspection 
than  the  most  arid  and  abstract  sentence.  Impressionism  is  as 
bad  as  formalism  ;  what  is  wanted  is  photography,  (v)  It  is  not 
advisable,  even  if  the  resources  of  the  laboratory  permit,  to  set 
the  whole  class  to  work  upon  the  same  problem.  The  student 
should  be  given  his  choice  of  a  beginning  upon  sight,  sounds 
smell,  taste  or  touch.  If  he  has  no  choice,  the  initial  experi- 
ments should  be  distributed  as  evenly  as  possible  over  these 
five  departments.  The  work  of  the  Instructor  is  thus  made 
more  varied  and  less  monotonous ;  the  students  are  impressed 
with  the  fact  that  competition  plays  no  part  in  the  psycho- 
logical laboratory ;  and  interest  is  aroused  and  kept  alive  by  the 
exchange  of  experiences  outside  of  the  laboratory. 

The  apparatus  figured  in  the  text  are  the  cheapest  and  sim- 
plest pieces  that  the  author  has  found  reliable.  They  are  not 
necessarily  the  best ;  but  they  are  the  best  to  be  obtained  at 
small  cost,  and  they  are  adequate  to  the  experiments.  The  prices 
affixed  are  approximate  only  ;  the  cost  of  a  particular  piece  may 
vary  from  year  to  year  with  the  demand,  the  cost  of  materials, 
the  addition  of  improvements,  the  simplification  of  parts,  etc. 

The  apparatus  figured  in  this  Part  are,  in  general,  either  his- 
torical pieces,  which  have  played  a  definite  part  in  the  develop- 
ment of  the  science,  or  standard  pieces,  the  best  of  those  that 
can  be  ordered  ready-made  from  the  instrument-makers.  Many 
of  the  latter  class  have  their  defects.  All  alike,  however,  are 
instruments  with  the  structure  and  working  of  which  the  stu- 
dent should  be  familiar.  The  author  would  therefore  advise 
that  large  wall-diagrams  (or  lantern  slides),  properly  lettered, 
be  prepared  from  the  cuts,  and  the  use  of  the  apparatus  explained 
in  lecture  at  the  conclusion  of  the  experiments  in  which  their 
simpler  counterparts  have  been  employed.  Other  diagrams 
may  be  prepared  from  the  cuts  in  instrument-makers'  catalogues, 
in  the  technical  journals,  and  in  the  illustrated  Psychologies. 
The  author  has  sought  to  give,  in  every  case,  a  reference  to  the 
book  or  paper  in  which  the  instrument  is  described. 

The  Results  quoted  are  copied  from  actual  laboratory  records. 
They  show  what  may  be  done  by  a  student  of  good  average 


§  6,    Courses  in  Experimental  Psychology  xxxi 

ability  who  takes  his  work  seriously.  They  arc  not  to  be  com- 
pared, in  any  sense,  with  the  results  of  investigations  published 
in  the  psychological  journals.  The  author  prints  them  for  the 
reason  that  (with  the  very  few  exceptions  mentioned  below) 
here  is  nothing  in  the  literature  to  set  the  standard  of  attain- 
ment in  experiments  of  this  kind. 

The  literary  references  are  very  incomplete,  —  although  both 
Instructor  and  student  may  object  to  their  range  and  number. 
The  author  has  never  quoted  for  the  sake  of  quoting ;  there  is 
something  of  value  for  the  experiment  in  every  one  of  the  mono- 
graphs cited.  The  books  required  for  answers  to  Questions  are 
all  readily  accessible. 

All  the  experiments  of  this  Volume  offer  opportunities  for  the 
discussion  of  points  in  systematic  psychology.  The  author  has 
introduced  some  such  discussions,  approximately  in  the  same 
measure  and  with  the  same  fulness  that  he  has  found  practicable 
in  actual  laboratory  work.  The  body  of  the  Course  is,  however, 
neither  dependent  upon  nor  necessarily  connected  with  any  par- 
ticular system.  The  materials  here  given  may  be  utilised  for 
lectures  or  for  informal  laboratory  conversations ;  the  author's 
views  may  be  accepted  or  simply  made  the  basis  of  criticism ; 
the  references  may  be  looked  up  by  the  student  for  himself  or 
by  the  Instructor  for  him  ;  systematic  matters  may  be  given 
more  attention  than  the  author  has  given  them  or  may  be 
entirely  ignored.  Such  things  lie,  of  course,  in  the  discretion 
of  the  Instructor. 

Finally,  it  may  be  said  that  this  first  Volume  is  intended  to 
represent  a  half-year's  work  for  third  year  students,  the  second 
half  of  the  year  being  devoted  to  the  quantitative  work  of 
Vol.  II. 

§  6.  Courses  in  Experimental  Psychology.  —  There  are  at  the 
present  time  three  published  Courses  (or  part-courses)  in  labo- 
ratory psychology. 

The  most  complete  Course  is  the  Psychologische  Schulversuche, 
mit  Angabe  der  Apparate,  by  A.  Hofler  and  S.  Witasek  (Leip- 
zig. Barth,  19CX);  pp.  viii.,  30).  This  little  book  outlines  seventy- 
five  tests  or  experiments  for  use  in  the  Austrian  Gymnasien, 


xxxii  Introduction:  Hints  to  the  Instructor 

In  choice  and  arrangement  of  material  it  follows  Hofler's  Psy- 
chologie.  An  especially  good  feature  is  the  first-hand  reference 
to  authorities  (Fechner,  Stumpf,  Hering).  On  the  other  hand, 
as  the  dimensions  of  the  work  attest,  practically  nothing  is  said 
of  the  conduct  of  the  experiments,  of  sources  of  error,  etc. 

An  Elementary  Course  in  Psychological  Measurements,  by 
E.  W.  Scripture  (Studies  from  the  Yale  Psychological  Labo- 
ratory, iv.,  1896,  89-139),  describes  seventeen  of  the  thirty 
experiments  which  constitute  the  elementary  course  in  the 
Yale  laboratory.  In  most  cases,  specimen  records  are  given. 
Emphasis  is  laid  upon  manipulation  and  computation,  while 
introspection  is  practically  ignored. 

More  akin  to  the  present  Course  is  E.  C.  Sanford's  A  Course 
in  Experimental  Psychology :  Part  I.,  Sensation  and  Perception 
(Boston,  Heath,  1898;  pp.  viii.,  449.  The  first  six  of  the  nine 
chapters  of  the  work  were  issued  as  'advance  sheets'  in  1894). 
This  book  outlines  no  less  than  239  experiments,  qualitative  and 
quantitative,  upon  the  subjects  mentioned  in  its  title.  It  has  a 
high  historical  importance,  as  the  first  manual  of  experimental 
psychology ;  it  has  exerted,  and  still  exerts,  a  wide  influence,  as 
the  gateway  through  which  American  students  are  introduced 
to  laboratory  work ;  and  it  is  a  monument  of  accurate  eru- 
dition. 

The  author's  indebtedness  to  Sanford  is  very  great,  both  on  positive  and 
on  negative  grounds.  The  investigator  who  goes  over  the  literature  of  the 
science  for  the  first  time  is  undertaking  a  labour  which,  if  conscientiously  per- 
formed, is  in  large  measure  spared  to  later  workers  in  the  same  field  :  and 
Sanford's  *  Course'  is  alike  remarkable  for  range  of  knowledge,  impartiality 
and  judgment  in  selection.  But  a  pioneer  work  must  pay  the  penalty  of  its 
originality.  And,  from  the  educational  point  of  view,  the  *  Course '  appears  to 
the  author  to  have  three  defects,  (i)  The  brevity  of  its  directions  is  likely 
to  give  the  student  an  idea  that  the  psychological  experiment  is  intrinsically 
easy,  and  capable  of  very  rapid  performance.  (2)  Its  neglect  of  introspection 
tends  to  obscure  the  essential  difference  between  the  psychological  experiment 
and  the  experiments  of  the  natural  sciences.  (3)  It  throws  too  great  a  bur- 
den upon  the  Instructor.  As  a  catalogue  raisonne  in  the  hands  of  one  thor- 
oughly familiar  with  its  subject-matter,  the  book  is  admirable  ;  if  this  familiarity 
be  lacking,  the  Instructor  may  be  led  into  the  same  error  to  which  the  student 
is  liable.  There  is,  indeed,  some  evidence  that  Sanford  has  himself  become 
sensible  of  these  defects  as  his  work  proceeded ;  for  not  only  are  the  later 


§  6.    Courses  in  Experimental  Psychology  xxxiii 

•ectkm  written  in  much  greater  detail  than  the  earlier,  but  the  latest  of  all 
GO!  -trative  records  of  results. 

should  be  made  here  of  H.  MUnsterberg^s  Puudopiks  (Milton 
Bradley  Co^  Springfield,  Mass. ;  $5.00),  a  set  of  portfolios  containing  mate- 
rials for  a  good  number  of.  experiments  in  visual  sensation  and  perception. 

The  experiments  of  the  text  have  been  chosen  from  the  much 
greater  number  that  have  been  worked  out  in  the  Cornell  labo- 
rator)'.  The  author  does  not  regard  their  selection  as  final, 
even  for  his  own  purposes.  In  some  cases,  as  in  the  spheres  of 
visual  and  cutaneous  sensation,  the  choice  of  problems  presents 
no  difficulty ;  in  others,  as  in  auditory  sensation,  it  is  far  from 
easy.  Moreover,  it  is  true  in  general,  as  Sanford  says,  that 
"what  a  good  laboratory  course  ought  to  include  is  not  yet 
wholly  clear."     At  the  same  time,  the  range  of  experiments  that 

tord  training  in  laboratory  arts,  that  give  opportunity  for  intro- 
spection in  the  various  fields  of  mind,  and  that  can  be  performed 
with  some  sort  of  thoroughness  in  the  brief  time  at  the  stu- 
dent's disposal,  is  not  so  wide  as  at  first  thought  it  might  appear. 
Thus,  experiments  upon  the  more  complex  processes  or  con- 
sciousnesses (memory,  imagination,  reasoning,  emotion  and  the 
like)  are,  for  the  most  part,  ruled  out  of  a  Manual  by  the  time 
limit ;  they  require  systematic  work,  preceded  by  a  term  of  prac- 
tice, and  so  take  on  the  form  of  investigations  rather  than  of 
single  experiments. 


PART   I 

SENSATION,  AFFECTION  ATTENTION  AND 
ACTION 


CHAPTER   I 
Visual  Sensation 

§  7.  Scniatioii.  —  There  has  been  a  good  deal  of  discussion, 
of  recent  years,  as  to  the  right  way  to  teach  psychology.  Ought 
one  to  begin  with  the  '  real '  mind,  and  work  down  from  that  to 
sensation,  travelling  in  this  way  from  the  better  known  to  the 
less  known  ?  Or  ought  one  to  begin  with  the  simplest,  and 
Work  up  to  the  most  complex,  —  to  begin  with  sensation,  and 
end  with  mind  ? 

Psychology  is  too  young  a  science,  —  nay,  for  that  matter, 
natural  science  itself  is  perhaps  too  young,  —  to  permit  of  our 
hoping  for  any  final  settlement  of  the  issue.  Moreover,  it  is 
worth  while  to  remind  ourselves  explicitly  that  its  settlement  is 
not  a  life-and-death  affair.  If  the  teacher  knows  his  subject, 
and  is  in  love  with  it,  it  will  in  large  measure  teach  itself :  what- 
ever the  formal  setting  of  the  teaching,  the  student  will  imbibe 
the  scientific  spirit,  and  learn  to  think  in  scientific  terms.  How- 
ever, since  a  choice  must  be  made,  and  has  been  made  in  this 
book,  we  may  dwell  for  a  moment  upon  the  practical  reasons 
for  choosing. 

In  a  course  of  general  and  elementary  lectures,  such  as  a 
Manual  like  the  present  presupposes,  it  is,  no  doubt,  necessary 
to  begin  with  the  'real'  mind.  One  cannot  start  a  train  of 
thought  without  having  a  starting-point.  And  it  is  well,  in 
such  a  course,  to  give  illustrations  of  the  analytic  procedure. 
The  steps  in  the  procedure  itself  will  hardly  be  understood :  if 


2  Visual  Sensation 

for  no  other  reason,  because  it  would  take  the  lecturer  too  long 
to  explain  just  why  the  investigator  did  this  and  did  that ;  the 
experiment  implies  the  science.  Still,  the  hearer  will  have  a 
general  idea  of  the  first  problem  of  psychology.  Even  here, 
however,  the  influence  of  popular  psychology  is  so  strongly 
antagonistic  to  clean  psychological  thinking,  and  the  hearer's 
furniture  of  ideas  is  such  a  mixed  medley  of  psychological  tradi- 
tion, logical  construction,  and  ethical  appreciation,  that  it  be- 
comes imperative,  from  time  to  time,  to  break  away  from  the 
starting-point :  to  work  from  the  known  to  the  unknown,  not  by 
gradually  educing  the  implications  of  the  known,  but  by  con- 
fronting it  point  blank  with  a  statement  of  the  unknown. 

If  this  holds  of  an  introductory  lecture  course,  it  holds  still 
more  of  laboratory  work.  The  student  who  enters  the  psycho- 
logical laboratory  is  burdened  with  a  mass  of  misconceptions. 
The  physics  and  physiology  of  the  *  average  man,'  crude  and 
foolish  as  they  are,  come  much  nearer  to  fact  than  his  psychology 
does.  Scientific  psychology  is  hardly  older  than  he  is  himself, 
whereas  the  race  has  been  speculating  upon  mental  things  for 
more  than  two  thousand  years,  and  the  transmitted  speculation 
has  become  dogma.  Hence  it  seems  pedagogically  desirable 
that  the  student  should  be  asked,  from  the  first,  to  put  himself 
in  a  new  attitude  to  mind ;  to  hold  his  opinions  as  to  mental 
function  and  faculty  in  abeyance,  until  he  has  become  familiar 
with  the  results  of  scientific  analysis,  and  has  seen  mind 
take  scientific  form  from  the  synthesis  of  the  elements.  And 
it  then  becomes  a  matter  of  method,  of  time-saving,  that  he 
should  begin  with  the  simple  and  be  gradually  led  on  to  the 
complex. 

Further:  it  must  not  be  supposed  that  this  direction  of  work 
holds  the  student  to  a  rut,  aside  from  the  wider  issues  of  general 
psychology.  The  facts  of  sense  psychology  are  not  blind  ob- 
servations, made  and  done  with.  Laboratory  work,  intelligently 
conducted,  cannot  fail  to  raise  the  main  questions  of  the  psycho- 
logical system  :  only  it  raises  them  locally,  so  to  say,  and  in 
concrete  form,  instead  of  generically,  in  conceptual  phrasing. 
When,  therefore,  the  student  comes  to  the  historical  and  sys- 
tematic work  which  should  follow  the  laboratory  drill,  he  finds 


§  7-    Scnsittwn  3 

that  his  old  opinions  have  been  insensibly  modified :  the  prob- 
lems of  mind  have  received  a  new  formulation,  in  which  they 
show  clear  of  any  logical  or  ethical  colour:  a  critical  judgment 
—  weak  at  first,  perhaps,  but  still  critical  —  is  brought  to  bear 
upon  the  inherited  axioms  and  facile  generalisations  of  popular 
psychology. 

And  this  result  could  not  have  been  obtained,  if  we  had 
worked  from  the  *  real '  mind  downwards  ?  Certainly,  it  could : 
that  we  have  admitted.  But  it  could  have  been  obtained  only 
under  disadvantages,  and  with  waste  of  time.  Under  disad- 
vantages, —  for  there  has  been  no  resolute  effort  to  substitute 
the  scientific  for  the  naive  view  of  mind,  and  so  the  start  is  bad : 
with  waste  of  time,  —  because  your  analysis  of  any  complex 
process,  undertaken  for  the  first  time,  will  leave  you  with  loose 
ends  of  process,  unaccounted  for,  which  may  be  elemental  or 
may  not :  you  cannot  tell,  until  you  have  analysed  other  com- 
plexes, and  then  repeated  your  analysis  of  this  :  and  even  so,  you 
are  bound  to  test  the  validity  of  your  work  by  doing  precisely 
what  the  opposite  method  does,  working  from  below  upwards, 
from  your  professed  simples  to  the  actual  compound.  Unless, 
then,  there  is  training,  otherwise  unobtainable,  in  work  done  by 
this  method,  the  method  would  seem  to  be  pedagogically  in- 
ferior; and  it  is  argued  in  the  text  that  no  such  training  is 
afforded.* 

The  following  points  in  the  psychology  of  sensation  should  be 
laid  clearly  before  the  student  from  the  outset. 

(i)  The  sensation  is  strictly  subject-matter  for  psychology.  This  point 
can  be  \*ariously  brought  out.  Thus,  physics  deals  with  light,  ether  waves ; 
I^ysiology  with  the  working  of  the  eye ;  psychology  with  colour  and  bright- 
Or  a^n :  the  world  of  natural  science  is  colourless  and  soundless,  — 


>Tbe  above  discnation  has  taken  the  proposal  to  begin  psychology  with  the  '  real ' 
Bund  at  its  own  estimate :  in  other  words,  has  accepted  the  possibility  of  tuch  a  be- 
ginning. It  does  not  require  much  thought,  however,  to  see  that  no  sort  of  psychol- 
ogy can  begin  with  the  '  real  *  mind.  Science  cannot  deal  with  the  individual,  but 
only  with  the  abstract,  the  generally  valid.  Whether  we  begin  our  psychology  with 
'seaaation'  or  with  a  case  of '  association  of  ideas,'  we  are  always  beginning  with  an 
abstnction.  The  difference  between  the  two  methods  of  teaching  is  a  difference  in 
degree,  not  in  any  sense  a  difference  in  kind. 


4  Visual  Sensation 

not  in  the  sense  that  it  is  dark  and  silent,  but  in  the  sense  that  any  word 
connected  with  seeing  and  hearing  is  foreign  to  it,  makes  nonsense  with  it,  as 
it  would  be  nonsense  to  talk  of  a  benevolent  carpet. 

(2)  The  sensation  is  not  'simple'  in  the  sense  that  it  is  characterisable  by 
a  single  adjective.  It  is  an  ultimate  process  of  structural  analysis,  as  the  cell 
is  in  morphology  or  the  'element'  in  chemistry.  But  cells  have  a  highly 
composite  structure,  while  they  differ  largely  as  regards  shape,  size,  length  of 
life,  etc. ;  and  the  chemical  elements,  though  irreducible  as  '  gold '  or  '  iron,' 
still  show  differences  of  physical  attributes.  The  sensation  gives  no  indica- 
tion of  constituent  parts,  as  the  cell  does ;  but  it  has  various  aspects  or  prop- 
erties,—  of  which  only  'quality'  is  to  be  dealt  with  here. 

(3)  This  sensation,  which  is  a  structural  unit  of  the  adult  mind,  is  not  the 
genetic  unit  of  mind  at  large.  Mind  has  not  grown  by  aggregation  of  sensa- 
tions, by  the  simple  addition  of  our  '  blue '  and  '  yellow '  to  a  given  '  black ' 
and  '  white '  that  are  also  like  ours,  and  by  the  further  addition,  still  later,  of 
a  ready-made  'red'  and  'green.'  Even  granted  that  we  could  analyse  the 
primitive  mind  into  sensations,  still  its  '  black '  and  '  white '  would  be  so  dif- 
ferent from  our  own  as  to  be  hardly  recognisable.  At  the  time  when  the 
heart  begins  to  pulsate,  there  are  no  muscle  fibrillae  in  the  myocardium ;  we 
have  the  sight  of  purely  protoplasmic,  undifferentiated  cells  making  strong 
rhythmical  contractions.  If,  now,  the  structural  elements  of  the  primitive 
mind  are  '  sensations,'  they  are  sensations  only  in  the  sense  that  these  primi- 
tive heart-cells  are  '  muscle '  cells. 

(4)  Nor  is  this  sensation  a  functional  unit  of  mind.  It  is  not  the  tiniest 
bit  of  mind  that  can  give  us  knowledge,  not  the  simplest  form  of  knowing. 
Knowing,  i.e.,  does  not  come,  any  more  than  does  mind,  from  the  addition  of 
sensation  to  sensation.  The  sensation  'blue '  does  not  tell  us  of  a  blue  object, 
does  not  even  tell  us  that  it  comes  from  the  eye.  It  simply  presents  itself,  as 
a  mental  irreducible ;  and  we  have  to  examine  it  for  its  own  sake,  —  to  watch 
its  behaviour  under  varying  conditions,  and  to  trace  it  in  all  the  compounds 
into  which  it  enters.  If  the  student  insist,  as  at  first  he  may,  that  he  cannot 
possibly  think  of  a  '  blue '  that  is  not  a  '  blue  something,'  the  answer  is  two- 
fold. He  is  not  to  'think  of  a  blue  at  all,  but  to  be  a  blue  ;  his  conscious- 
ness is  to  be  a  blue-consciousness,  not  a  consciousness  made  up  of  ideas 
associated  to  blueness  in  the  course  of  his  experience.  And  the  reason  for 
his  difficulty  is  simply  that  he  has  not  pushed  his  introspection  far  enough  ; 
he  has  not  stripped  the  sensation  '  blue '  of  all  the  overlay  of  associated  (more 
especially  organic)  processes  that  make  '  blue '  mean  '  the  blueness  of  some- 
thing' in  everyday  life. 

(5)  The  sensations  which  we  begin  with,  in  our  work,  are  precisely  the 
same  as  the  sensations  that  we  speak  of  as  entering  into  perceptions,  associa- 
tions, etc.  Thus  the  '  pressure  sensation '  of  the  pressure  spot  is  the  same 
sensation  as  the  'pressure'  that  we  deal  with  when  we  are  attacking  the 
problem  of  cutaneous  localisation.  There  is  no  gap,  and  therefore  no  need 
of  a  bridge,  between  sense  psychology  and  the  psychology  beyond  sense. 


{  8.    Visual  Sensatiim  5 

K  ..^  ..v>t  to  be  supposed  that  these  points  will  all  be  gasped, 
^  r  their  significance  realised,  in  a  week  or  a  month  or  even  a 
term.  But  opportunities  for  insisting  upon  them  will  be  con- 
stantly arising  in  the  course  of  experimental  work,  and  every 
such  opportunity  should  be  seized. 

§  8.    Viiual  Sensation. —  On  visual  sensation  in  general  see: 

H.  Aubert,  Grundzuge  d.  phy'siol.  Optik,  1876,  479. 

H.  Ebbinghaus,  GnindzUge  d.  Ps>xhol.,  i.,  1897,  180. 

A.  Pick,  in  Hermann's  Handbuch  d.  Physiologie,  iii.,  i,  1879,  139* 

H.  L.  F.  von  Hclmholtz,  Handbuch  d.  physiol.  Optik,  1896,  231. 

E.  Hering,  Zur  Lehre  vom  Lichtsinnef  1878. 

J.  von  Kries,  Die  GesichtsempfinduDgeQ  u.  ihre  Analyse,  1882. 

G.  E.  MUller,  Zeits.  f.  Psychol.,  x.,  1896,  i,  321. 

£.  C.  Sanford,  Course,  exps.  113  fT.,  122  ff.,  135  ff. 

W.  Wundt,  Philos.  Studien,  iv.,  1888,  311. 

Cf.  also  C.  L.  Franklin,  Mind,  N.  S.,  ii.,  1893,  473;  M.  Foster,  A  Text- 
book of  Physiology,  iv.,  1891,  1222;  G.  F.  Stout,  A  Manual  of  Psycholog>', 
1899,  141 ;  Titchener,  An  Outline  of  Psych.,  1899,  52;  O.  KUlpe,  Outlines 
of  Psych.,  1895,  112 ;  Wundt,  Phys.  Psych.,  i.,  1893,  482. 

On  the  colour  pyramid  see : 

Ebbinghaus,  184;  Titchener,  Primer  of  Psychol.,  1899,  41;  K.  Zindler, 
Zeits.  f.  Psych.,  xx.,  1899,  225 ;  Wundt,  Phys.  Psych.,  i.,  1893,  504. 

It  is  important  that  the  student  thoroughly  understand  the 
colour  pyramid,  and  that  he  shall  think  of  it  always  as  a  purely 
psychological  (not  physical  or  physiological)  construction. 

Question  { i )  The  surface  of  the  figure  contains  the  relatively 
most  saturated  colour-tones.  Round  the  base  we  have  the 
'pure*  colours,  red,  etc.;  towards  white,  we  have  the  pinks, 
straw  yellows,  sky  blues,  pale  greens;  towards  black,  the 
Bordeaux  reds,  chocolate  browns,  indigo  blues,  dark  greens. 
All  these  tones  are  the  most  saturated  possible,  the  most  col- 
oured colours  of  their  kind.  Each  of  them  lies  upon  the  straight 
line  which  connects  their  parent  spectral  colour  with  white  or 
black,  and  at  the  height  of  the  grey  (black-white  series)  to  which 
their  brightness  corresponds. 

If  we  peel  the  figure,  leaving  the  black  and  white  poles  un- 
touched, we  get  precisely  what  we  had  before,  save  that  all  the 
colour-tones  are  less  saturated,  lie  so  much  nearer  to  the  neutral 


6  Visual  Sensation 

tones  of  the  axis.  It  is  clear,  further,  that  if  we  pare  the  figure 
with  a  knife  that  cuts  parallel  to  the  axis  and  at  a  definite  dis- 
tance from  it,  we  have  upon  the  cut  surface  colour-tones  which 
are  all  of  the  same  degree  of  saturation. 

The  cross-section  shows  us  all  the  colours  that  exist,  which 
are  of  the  same  brightness  as  the  grey  of  the  plane  of  section. 

The  longitudinal  section  shows  us  {a')  the  neutral  axis,  and 
{b)  all  possible  nuances  of  two  colour-tones,  the  tones  of  the 
points  of  section  upon  the  base. 

(2)  The  first  part  of  this  question  is  best  answered  after  the 
performance  of  the  Preliminary  Exercise. 

Y  is  the  colour  that  stands  nearest  to  white,  in  introspection. 
As  we  have  assumed  that  our  base  lies  in  a  single  plane,  the 
complementary  B  must  sink  correspondingly  towards  black.  B 
is  undoubtedly  the  colour  that  stands  nearest  to  black ;  but  how 
far  down  it  should  be  placed  we  do  not  know. 

(3)  The  length  of  RY,  etc.,  depends  upon  the  number  of 
colour-tones  that  can  be  distinguished,  under  similar  conditions, 
between  the  end-points  of  the  lines.  The  angles  are  determined 
by  the  number  of  just  noticeable  differences  of  sensation  that 
separate  the  opposite  points  RG  and  YB^  when  we  pass  from 
point  to  point,  not  through  saturated  colours,  but  by  the  shortest 
possible  road,  i.c.^  through  the  black-white  axis.  As  neither  of 
these  determinations  has  been  accurately  made,  the  distances  in 
the  Figure  are  conventional,  and  the  angles  have  been  rounded. 

(4)  See  Hering,  Lichtsinn,  89 ;  and  p.  44  below. 

(5)  This  question  need  not  be  answered  at  once,  but  may  be 
assigned  as  an  additional  exercise  later  in  the  course.  The 
fullest  and  most  impartial  account  that  we  have  at  second  hand 
is  that  given  by  Ebbinghaus. 

(6)  Ebbinghaus,  183,  187,  247,  253.  It  is  important  that  the 
physical,  physiological  and  psychological  uses  of  the  terms  be 
distinguished. 

(7)  We  have  {a)  the  problems  of  indirect  vision  and  of  colour 
blindness,  and  {b)  the  problems  of  the  relation  of  sensation  to 
stimulus.  These  are  five  in  number:  (i)  the  dependence  of 
sensation  upon  the  wave-length  of  the  stimulus ;  (ii)  its  depend- 
ence upon  the  intensity  of  stimulus  :  the  Purkinje  phenomenon; 


§  8.    yisuai  StHsation 


\n\)  Its  dependence  upon  the  composition  of  stimulus:  colour 

mixture;  (iv)  its  dependence  upon  the  spatial  distribution  of 

stimulus :  contrast ;  and 

(v)  its  dependence  upon 

the  temporal  relations  of 

stimulus :  adaptation  and 

after-images. 

See  Ebbinghaus,  3oa  We 
deil  with  {b)  (i)  in  the  fol- 
lowing preliminar)*  exercise; 
ind  with  the  first  part  of  (a), 
and  with  {b)  (iii).  (iv),  (V), 
in  special  Experiments.  On 
the  Purkinje  phenomenon,  see 
Ebbinghaus,  203.  It  can 
be  demonstrated  as  follows. 
Lay  a  stick  of  red  sealing 
wax  upon  an  ultramarine-blue 
ground  that  in  daylight  is  dis- 
tinctly darker  than  the  red. 
Decrease  the  illumination. 
Presently  the  red  becomes  a 
dead  black,  while  the  dark 
bhie  shows  a  bright  bluish-grey  shimmer. 
in  Experimental  Psychology,  1898,  142 


Fig.  I. —  Hering't  app«rmtut  for  testing  colour 
blindneM.  R.  Rothe,  Mk.  100.  See  E.  Her- 
ing,  Arch.  f.  Ophthalm.,  xxxvL,  i,  1890,  217. 


Cf.  E.  C.  Sanford,  A  Course 
On  colour  blindness,  see  Ebbing- 
haus,  194,  and  the  bibliography  in  Helmholtz,  Phys.  Optik,  1179.  For  test- 
ing, use  the  Hering  apparatus.  Fig.  i. 


Preliminary  Exercise.  —  The  spectrum  chart  may  be  pur- 
chased of  the  Prang  Educational  Co.,  Boston,  Mass.,  for  ^i.oo. 

The  following  points  may  be  noticed.  ( i )  The  spectral  band 
represents  a  large  number  of  sensation  qualities,  each  of  which 
passes  over  into  its  neighbour  through  intermediate  qualities. 
(2)  The  change  of  quality  is  sharply  emphasised  at  certain 
places  in  the  series.  Thus  we  have  continuity  from  Red  to 
Yellow.  Then  we  seem,  as  it  were,  to  turn  a  comer,  and  travel 
continuously  from  Yellow  to  Green.  Again  we  turn  a  comer, 
and  get  from  Green  to  Blue.  Here  we  turn,  for  the  last  time, 
and  can  pass  without  break  from  Blue,  through  Violet,  back  to 
our  starting-point,  Red.  (3)  This  last  fact  brings  out  another: 
the  fact,  namely,  that  the  spectrum  has  at  its  extreme  ends  the 


8  Visual  Sensation 

two  colours  which  are  most  nearly  alike.  Red  is  more  like 
Violet  than  it  is  even  like  Orange.  (4)  And  with  this  goes  the 
further  fact,  that  the  spectrum  does  not  show  us  the  full  total 
of  colour  qualities.  By  mixing  Violet  with  Red  we  obtain  a 
series  of  intermediate  Purples.  If  we  think  of  the  Red  of  the 
spectrum  as  prolonged,  on  our  left,  through  purplish  red  to 
Purple,  and  of  the  Violet  as  prolonged,  on  our  right,  through 
violet-purple  to  Purple,  we  have  a  series  beginning  and  ending 
with  the  same  colour,  which  does  represent  the  complete  tale  of 
colour  qualities  (see  the  base  of  the  colour  pyramid).  (5)  The 
spectrum,  again,  shows  us  none  of  the  pure  brightness  qualities ; 
none  of  the  blacks,  whites  and  greys.  (6)  It  does  show  us  its 
colours  intermixed  with  different  brightnesses.  Thus,  Yellow  is 
by  far  the  brightest  colour  of  the  spectrum  ;  Violet  is  the  darkest. 
It  is  a  good  exercise  to  arrange  the  spectral  colours  in  the  order 
of  brightness,  from  light  to  dark,  within  these  limits.  (7)  There 
is  a  psychological  unfairness,  so  to  speak,  in  the  spatial  distribu- 
tion of  the  spectral  qualities.  Different  sensations  are  crowded 
together,  e.g.,  in  the  yellow-green  region,  while  there  are  great 
bands  of  red  and  violet  that  look  almost  the  same  throughout. 

(8)  Probably,  in  staring  at  the  chart,  certain  after-image 
phenomena    will    arise    and    attract    the    observers*   attention. 

(9)  The  varying  degrees  of  saturation  of  the  qualities  may  be 
remarked.  Not  only  is  yellow  the  brightest  colour ;  it  is  the 
least  coloured  colour,  the  colour  most  nearly  approximating  to  a 
pure  brightness.  The  red  will,  probably,  seem  to  be  the  most 
saturated  colour  of  the  series  ;  after  it  come  the  blue,  green  and 
violet.  Violet,  i.e.,  though  very  dark,  is  well  saturated.  (10)  If 
the  chart  has  been  observed  with  steady  fixation  (Hering's 
local  adaptation),  a  phenomenon  will  be  observed  which  is  the 
direct  opposite  of  contrast :  each  patch  of  colour  will  seem  to 
spread  itself  out  over  the  neighbouring  portions  of  the  colour 
series  (Hering's  simultaneous  light  induction).  The  result  is, 
that  brightnesses  tend  all  towards  a  neutral  grey,  and  colours 
all  towards  diminished  saturation,  and  hence,  ultimately,  also 
towards  neutral  grey. 

It  should  be  impressed,   again,   upon  the  student   that  the 
'psychological'  spectrum  is  quite  a  different  matter  from  the 


§  9*    Colour  MixiMir  9 

'physical'  spectrum.  The  purpic-cxtcnsions  of  the  two  ends  of 
the  spectrum  have,  of  course,  nothing  at  all  to  do  with  the 
infra-red  and  the  ultra-violet  of  the  physicist.  We  make  use  of 
the  spectrum  simply  because  it  is  a  well-known  and  easily  pro- 
curable  band  of  colours,  which  presents  all  the  colour  qualities 
(with  the  exception  of  the  purples)  at  their  highest  saturation : 
we  are  not  concerned  with  its  physical  significance. 

BXPBRIMBNT  I 

§  9.  Colonr  Mixing.  —  It  will  probably  be  found  advantageous, 
in  these  experiments,  to  let  each  student  combine  the  functions 
of  O  and  E,  —  to  let  each  manage  his  own  mi.xer,  and  take  his 
own  introspective  records.  Much  time  is  saved  by  such  an 
arrangement ;  and  there  is  no  need  of  any  questioning  of  O  by 
E^  since  the  verdict  of  introspection  is  read  off  directly  from  the 
discs.  For  quantitative  work,  it  would  be  better  to  entrust  the 
changing  of  the  discs  and  starting  of  the  mixer  to  E,  and  to 
direct  O  to  turn  his  eyes  upon  some  indifferently  tinted  surface, 
of  the  average  brightness  of  his  surroundings,  during  the  inter- 
vals between  experiment  and  experiment.  As  it  is,  the  student 
should  be  instructed  to  look  at  the  discs  for  as  short  a  time  as 
possible,  compatibly  with  accurate  matching ;  and  to  look  off 
towards  the  grey  screen,  after  the  adjustment  of  discs  for  a  new 
experiment,  in  order  to  satisfy  himself  that  he  has  no  coloured 
after-image.  If  such  an  image  appears,  he  must  wait  till  it  has 
passed  away,  before  making  his  determination. 

It  should  be  noted  that  mixture  experiments  with  coloured 
papers  are  not,  as  a  rule,  *pure  *  experiments.  Yellow  and  blue, 
when  mixed,  give  grey.  But  the  standard  yellow  of  a  coloured 
paper  series  generally  contains  a  certain  amount  of  orange  and 
red ;  and  the  standard  blue  generally  contains  a  certain  amount 
of  green  and  violet.  Hence,  in  mixing  'yellow'  and  *bluc,'  we 
are  really  mixing  all  the  colours  of  the  spectrum  ;  our  grey  is,  like 
daylight,  the  result  of  a  general  mixture.  The  mixed  nature  of 
the  coloured-paper  colours  can  be  seen  by  pasting  small  squares 
of  the  papers  upon  pieces  of  black  card,  and  looking  at  them 
through  a  prism.  Not  a  single  colour  is  seen,  but  a  fringe  of 
colours.  —  Nevertheless,  the  results  obtained  from  mixtures  of 


lO  Visual  Sensation 

these  colours  are  just  the  same  as  those  which  would  be  obtained 
from  mixtures  of  pure  colours  of  the  same  appearance ;  so  that 
there  is  nothing  in  the  experiments  to  mislead  the  student,  when 
once  the  fact  of  impurity  has  been  explained  to  him. 

It  should  be  noted,  further,  that  different  authors  and  different 
sciences  use  colour  names  in  different  meanings.  The  *pure* 
red  of  psychological  optics,  Hering's  Urroth,  is  (as  we  have 
remarked  above)  a  carmine,  a  red  with  a  distinctly  purplish 
tinge ;  not  a  vermilion,  an  orange-red.  The  *  pure '  green, 
Hering's  Urgriin^  is  a  bluish  green,  the  complementary  of 
carmine.  In  the  list  of  complementaries  in  the  text,  the  usual 
names  applied  to  the  spectral  colours  and  their  mixtures  are 
employed.  The  reason  is,  again,  merely  one  of  convenience. 
These  are  the  colour  names  in  ordinary  use,  and  the  coloured 
papers  most  readily  procurable  aim  rather  at  reproducing  spec- 
tral colours  than  at  showing  the  psychological  primaries. 

(i)  First  Laiv. — The  following  equations  were  obtained,  in 
diffuse  daylight,  by  mixture  of  the  Wundt  papers  (supplied  by 
E.  Zimmermann).  The  series  consists  of  R,  O^  (light),  O^ 
(dark),  Y,  YG  (very  light),  G,  GB,  BG,  B^  (light),  B2  (dark), 
V  and  P  (reddish) 

1 .  Carmine  and  bluish  green.     (Carmine  =  R  +  B^ ;  bluish  green  =  B^  +  G.) 

I25°R  +  79°Bi  +  I56°G  =  92°W  +  268°Bk. 

2.  Red  and  verdigris.     (Verdigris  =  G  +  BG.) 

io8°R  +  4o^G  +212°  BG  =  82°W  +  278°  Bk. 

3.  Orange  and  greenish  blue.     (Greenish  blue  =  G +GB.) 

1 13°  01  +  I7°G  +  230°  GB  =  123°  W  +  237°  Bk. 
108°  02  +  83°G  +  169°  GB  =  97°  W  +  263°  Bk. 

4.  Yellow  and  blue. 

i62°Y  +  i98°Bi  =  i8o°W  +  i8o^Bk. 

5.  Yellowish  green  and  violet.     (Yellowish  green  =  G  +  Y  or  YG  +  R.) 

(1)  266°V  +  4o°G  + 54° Y  =  73° W  + 287° Bk. 

(2)  177°  V  +  134°  YG  +  49°  R  =  1 1 1°  W  +  249°  Bk. 

6.  Green  and  purple.     (Purple  =  P  +  B*.) 

234°  P  +  42°  B2  +  84°  G  =  33°  W  +  327°  Bk. 


§  9-    Colour  Mixing  1 1 

(2)  Stcomd Law.  — The  'intermediate*  colours,  resulting  from 
the  mixture  of  colours  that  are  not  complementary,  are  just  as 
much  sensation  qualities,  f>.,  just  as  little  analysable  in  intro- 
spection, as  are  the  original  colours  of  the  mixture.  The  stu- 
dent is  apt  to  think  that  the  result  of  mixture  in  this  case  is  a 
qualitative  perception,  and  not  a  sensation  quality,  —  partly 
because  he  knows  that  two  colours  go  to  produce  it,  and  partly 
because  he  has  in  many  cases  only  a  double  name  (yellowish 
green)  or  a  descriptive  name  (orange)  for  it.  He  should,  there- 
fore, be  told  that,  if  the  real  spectrum  were  worked  through, 
line  by  line,  for  purposes  of  discrimination,  every  discriminable 
line  would  represent  a  sensation,  qualitatively  different  from  all 
the  other  lines  distinguished  before  or  after  it.  Orange  is  no 
more  a  mixture  of  red  and  yellow,  in  introspection,  than  white 
is  a  mixture  of  all  the  spectral  colours. 

The  following  equations  were  obtained,  with  the  Wundt 
papers,  in  diffuse  daylight. 

(1)  Y+G  =  YG.       Large:  ajs^^G+is-^V  +  iio" W=.S«a//.-  36o°YG. 

(2)  Y+R=a  -  75°Y  +  285^R=      "       297*»0»+2i»W 

+42*  Bk. 

(3)  B+G=BG.  «  l52*B«+2o8*G=      "       xi   W  +  349°BG. 

I3/»B»+223°G=      "       rw+352''BG. 

(4)  G+V=B.  -  4i*'G+3i9*V=     "       I33*'B«+I7°W 

+  210°  Bk  (dark  blue). 

(5)  R+B=V.  "      37*R  +  i6o<»B«+i63<'Bk=      "       360^'. 

(6)  R+B=P.  "        i3°B«+93''R+254*'Bk=      •«       360*^ P. 

*        ♦*  "         9*'B»+96''R  +  255°Bk=     "      360T. 

(7)  P+B=V.  «  I24^B»  +  236''P=      **       349°V+ii«»W. 

u        u  u     i30«>B«+io5='P+i25*Bk=     «      360°  V. 

(3)  Third  Law,  —  The  reason  for  the  condition  of  constant 
illumination  is  given  with  the  occurrence  of  the  Purkinje  phe- 
nomenon:  see  p.  7  above,  and  Ebbinghaus,  214.  The  law  is 
valid  over  a  fairly  wide  range  of  moderate  intensities. 

The  following  results  were  obtained  with  the  Wundt  papers, 
in  diffuse  daylight. 

/  X       if--j— J-  <  EG  212*)      ^      a*o     '«,o /-     >  Greenish  blue, 
(a)       Verdigris  ^P       ^^f  _W      82*       85    G    S 

R.H  t%\~^^    ^78'       98^  0«    ...  Orange. 


12  Visual  Sensation 


Then:  ,,    ^.    .     ( BG  io6°>k 


Verdigris]^  20^ 

Red 54' 


Greenish  blue  <  ^ 


(GB       8i' 

42.5' 
Orange  ...  O*  49' 
Black 7-5" 

W  +  32o°Bk 
Green 


_  either  the  first  or  the  third 
~  term  of  the  above  equation. 


(*)  Purple  I 


Yellowish  green  165 


244°  P) 

32°  Bn  =40= 

.  .  84°) 


Violet  |.^°Vh=.44°W+2i6»Bk. 

Then:  (122°?  + i6°B2)  +  42°G+82.5YG  + (57.5 V+4o'>R)=92'"W  +  268''Bk. 

^   ^       (W      30° 
Either  is  matched  by:  185.25  R  +  84.75  G  +  39°  O^  +  43.5  Bk  +  7.5°W. 

Corollaries. — (i)  Three  colours,  properly  chosen  and  pro- 
portioned, will  give  grey  when  mixed.  The  conditions  are  ful- 
filled when  the  three  can  be  split  up  into  four,  which  represent 
two  pairs  of  complementaries.  Thus  R,  G  and  V  can  be  split 
up  into  R,  YG,  BG,  V  (second  law).  Here  are  two  pairs  of 
complementaries ;  grey  results  from  a  rightly  proportioned 
mixture  (first  law). 

So  with  R,  Y  and  GB.  These  colours  are  equivalent  to  R,  Y, 
BG,  B  (second  law).  The  Y  and  the  B  cancel ;  the  R  cancels 
the  BG  (verdigris).      Grey  results  (first  law). 

The  following  results  were  obtained  with  the  Wundt  papers, 
in  diffuse  daylight. 

80°  R  +  123°  G  +  157°  V  =  65°  W  +  295°  Bk. 
74°  R  +  72°  Y  +  214°  GB  =  II9°W  +  241°  Bk. 

Let  the  student  work  out  similar  sets  of  three  for  himself, 
from  the  spectral  colours  and  purple. 

(2)  These  sets  of  three,  rightly  proportioned,  will  give  any 
colour,  as  well  as  grey ;  the  whole  spectral  series,  rightly  mixed, 
will  give  any  colour,  or  grey ;  all  the  spectral  colours,  with 
purple,  will  give  any  colour,  or  grey. 


§  9-    Colour  Mixing  13 

Take.  €,g,,  R.  G.  V.  These  are  equal  to  R,  YG.  BG,  V. 
Adjust  them  to  give  a  grey.  Now  (a)  make  up  a  disc  of  270® 
of  this  grey  mixture,  and  fill  in  the  remaining  90*  with  R. 
You  get  an  R.  {b)  Repeat,  but  fill  in  the  90**  with  G.  You  get 
a  G.  (f)  Repeat,  with  the  90**  of  V.  You  get  a  V.  {a)  Split 
up  the  colours  still  further.  YG  is  equal  to  Y  and  G.  G  is 
equal  to  YG  and  BG.  You  now  have,  then,  R,  Y,  YG.  BG,  BG 
again,  V.  If  the  R  cancels  the  two  BG,  and  the  V  the  YG.  the 
Y  must  emerge. 

(e)  Get  B  in  the  same  way.  Split  up  the  four  colours  into  R, 
YG,  B,  G,  V.  This  is  equal  to  R,  YG,  B.  YG,  BG,  V.  With 
enough  R  to  cancel  the  BG,  and  enough  V  to  cancel  the  two 
YG,  B  emerges.     Illustration  : 

8o«R  +  i23*»G  +  iS7*»V=65°W  +  295^Bk. 
(a)    (6o*R+92.25«G  +  ii7.75*'V)+90°R  =  (48.75°W  +  22i.2s'»Bk)+90*'R. 
{h)     (60°  R+92.25''G  + 117.75°  V)  +  9o°G  =  (48.75*'W  +  22i.25*Bk)+9o^G. 
(0     (60°  R  +  92.25*»G  + 117.75°  V) +90°  V  =  (48.7S*»W-f  221.25°  Bk)  +  9o'»V. 
(</)  i6i°R+i93°G-p6°V  =  35°W  +  24i°Bk4  84°Y. 

(0  30°R  +  85°G  +  245°V  =  39°W  +  26i°Bk  +  6o°B. 

Let  the  student  work  out  other  examples  for  himself. 

(3)  A  third  corollary,  which  may  be  regarded  as  the  obverse 
of  the  second,  is  as  follows :  any  unsaturated  colour  may  be 
matched  by  the  mixture  of  the  corresponding  saturated  colour 
and  white.  For  white  —  a  white  of  general  validity  —  may  be 
produced,  by  the  third  law,  through  the  mixture  of  saturated 
complementaries  in  the  right  proportions.  Let  the  colour  in 
question  be  supposed  to  be  one  of  these  complementaries.  If  it 
be  present  in  such  quantity  that  white  cannot  result  from  its 
mixture  with  the  complementary,  then  the  result  of  the  mixture 
(by  the  first  law)  is  an  unsaturated  colour  of  the  prevailing  tone. 
But  this  is  the  result  which  the  corollary  calls  for. 

The  student  has  already  matched  complementary  greys  with 
black-white  greys.  Let  him  now  take  two  discs,  composed  of 
270®  of  two  such  matched  greys  and  90**  of  one  or  other  of  the 
colours  employed  to  produce  the  complementary  grey.  The  two 
mixtures  will  match. 


14  Visual  Sensation 

Questions.  — (i)  The  characteristics  are  :  (i)  purity,  i.e.,  that 
the  red  be  not  a  red  that  is  half  orange,  the  green  not  a  yellow- 
ish green,  etc. ;  (ii)  a  high  degree  of  saturation  of  all  colours ; 
(iii)  as  nearly  an  equality  of  brightness  throughout  the  series  as 
is  compatible  with  good  saturation  of  the  colours  ;  (iv)  a  dead, 
dull  surface,  —  no  shininess  or  glazing ;  (v)  a  closely-woven, 
stringy  or  parchment-like  texture,  —  so  that  the  papers  do  not 
fray  at  the  edges,  or  wear  away  at  the  centre  (the  latter  fault  is 
common  to  very  many  of  the  papers  on  the  market,  and  is 
extremely  annoying);  (vi)  full  representation  of  the  scale  of 
colour  qualities,  and  a  selection  of  qualities  on  a  psychological 
basis,  —  so  that  the  step  from  colour  to  colour  is  a  psychologi- 
cally, not  a  physically,  equal  (or  roughly  equal)  step  in  each 
case.  —  See  above,  p.  lo. 

(2)  Contrast  (see  Exp.  III.).  If,  e.g.,  the  large  discs  were  too 
red,  the  margin  of  the  smaller  discs  would  look  greenish. 

(3)  See  above,  p.  12. 

(4)  There  are  various  ways,  (i)  Superposition  of  parts  of 
two  spectra.  This  is  the  best  and  only  entirely  reliable  method, 
(ii)  Irradiation  :  juxtaposition  of  small,  variously  coloured  sur- 
faces. This  is  used  in  oil  painting,  tapestry  weaving,  etc. ;  it  is 
of  little  value  in  the  laboratory,  although  the  following  short 
experiment  may  be  given.  Cut  narrow  strips,  of  equal  width, 
from  two  coloured  papers.  Weave  them  together  into  a  square, 
like  a  kindergarten  mat.  Set  them  up  behind  a  window  cut  in 
a  neutral  grey  cardboard,  and  walk  away  from  this  until  the 
lines  disappear,  and  the  colour  surface  is  uniform.  Compare  its 
impression  with  the  impression  made  by  a  compound  disc  (180° 
of  each  colour)  rotating  before  a  similar  background  at  the  same 
distance.  —  The  experiment  will  familiarise  the  student  with  the 
meaning  of  'irradiation,'  'dispersion  circles,'  etc.  (iii)  Reflec- 
tion. Lay  two  5  cm.  squares  of  coloured  paper,  14  cm.  apart,  on 
a  background  of  black  velvet  or  cardboard,  50  by  25  cm.  Seat 
yourself  at  a  table,  with  the  narrow  edge  of  this  background 
close  in  towards  your  chest.  Lay  your  elbows  on  the  table,  and 
hold  up,  midway  between  the  paper  squares,  a  piece  of  clear 
glass  30  cm.  high  and  25  cm.  broad.  Lean  your  head  down,  and 
incline  the  glass  towards  you,  so  that  your  forehead  may  rest 


$  9-    Colour  Mixing  Ij 

upon  the  edge  of  the  glass.  You  now  see  the  further  square  by 
transmitted  light  and  the  nearer  square  by  reflected  light.  If 
the  squares  are  rightly  placed,  their  colours  overlap  and  a  true 
mixture  results.  —  To  get  the  colours  at  equal  intensities,  you 
may  move  the  squares  nearer  to  or  farther  from  the  glass,  or  tilt 
the  glass  itself  to  different  angles.  The  nearer  the  squares  to 
the  glass,  and  the  less  nearly  the  angle  of  glass  with  background 
forms  a  right  angle,  the  more  intensive  is  the  reflected  colour  as 
compared  with  the  transmitted.  —  Mix  two  coloured  papers  in 
this  way,  and  then  assure  yourself,  by  comparison,  that  the 
result  of  their  mixture  is  the  same  with  that  obtained  from  rota- 
tion of  the  same  papers.  This  method  is  intrinsically  good,  but 
lacks  many  of  the  advantages  of  the  method  of  rotation.  It  was 
devised  by  J.  H.  Lambert :  Photometria,  sive  de  mensura  et 
gradibus  luminis,  colorum  et  umbrae,  1760,  p.  527.  (iv)  Double 
refraction.  Look  through  an  achromatic,  doubly  refracting 
prism  of  quartz  or  Iceland  spar,  at  two  coloured  squares  laid  side 
by  side.  The  fields  of  colour  will  partially  overlap ;  and  where 
they  do  so,  there  is  mixture  as  there  is  in  Lambert's  experi- 
I  :.t  Only,  the  brightness  of  each  of  the  overlapped  portions 
is  considerably  reduced.  —  This  method  has  been  used  by 
Hering  to  demonstrate  the  third  law  of  mixture,  (v)  We  may 
use  the  method  of  rotation  with  transmitted,  in  place  of  reflected 
light.  Cut  'skeleton  *  discs  of  a  not  too  heavy  black  card, — discs, 
i.e.,  20  cm.  in  diameter,  having  a  rim  i  cm.  wide,  a  solid  centre 
piece  of  6  cm.  diameter,  and  four  sectors  of  10°  each ;  all  the 
rest  is  cut  away.  Between  two  of  these  skeleton  discs  lay  discs 
cut  from  sheets  of  transparent  coloured  gelatine.  Mount  on  the 
mixer,  as  for  the  ordinary  paper  discs.  Place  O  in  the  dark 
room,  and  show  him  the  colours  by  transmitted  (day  or  artificial) 
light.  The  method  has  the  advantages  that  the  gelatine  mix- 
tures can  be  tested  directly  with  the  spectroscope,  and  their 
spectral  values  thus  determined,  and  that  certain  mixtures  give 
pure  spectral  colours.  It  has  the  disadvantages  of  being  more 
tedious  even  than  the  regular  method,  with  reflected  light ;  of 
requiring  more  elaborate  arrangements;  and  of  presenting 
greater  difficulties  to  judgment,  e.g.,  in  the  case  of  comple- 
mentarism. 


1 6  Visual  Sensation 

It  is  not  likely  that  any  student  will  recommend  mixture  of 
pigments.  Should  this  method  be  mentioned,  however,  its 
radical  difference  from  all  the  above-named  procedures  must  be 
fully  explained. 

The  method  of  mixture  by  rotating  discs  appears  to  originate 
with  P.  van  Musschenbroek  (Introductio  ad  philosophiam,  1768, 
ii.,  §  1820).  It  was  employed  later  by  J.  Plateau  (Poggen- 
dorff's  Annalen,  Ixxxviii.,  1853,  p.  172),  and  perfected  by 
J.  Clerk  Maxwell  (Trans.  R.  S.  Edin.,  xxi.,  1857,  p.  275).  Its 
advantages  are :  that  the  magnitude  of  any  given  sector  can  be 
readily  changed  and  accurately  measured,  and  that  brightness 
matches  and  colour  equations  of  all  kinds  can  be  easily  obtained 
and  verified. 

Additional  Questions.  —  (i)  See  Helmholtz,  Physiol.  Optik, 
2d  ed.,  pp.  311  ff .  ;  Hering,  Zur  Lehre  vom  Lichtsinne,  v., 
vi.,  1878  (reprint  of  work  published  1872-4);  Ueber  Newton's 
Gesetz  der  Farbenmischung,  1887  (off-print  from  Lotos,  N.  F., 
vii. :  often  found  bound  up  with  the  foregoing) ;  Eine  Vorricht- 
ung  zur  Farbenmischung,  etc.,  Pfliiger's  Archiv,  xlii.,  1888, 
pp.  1 19  ff.  See  also  A.  Tschermak,  Ueber  die  Bedeutung  der 
Lichtstarke  und  des  Zustandes  des  Sehorganes  fiir  farblose 
optische  Gleichungen,  Pfiuger's  Archiv,  Ixx.,  1898,  pp.  297  ff. 
—  A  good  popular  account  of  the  two  theories  is  given  by 
Ebbinghaus,  Psychologic,  i.,  pp.  209-217,  245-263. 

(2)  Hering,  Zur  Lehre  vom  Lichtsinne,  iii.,  v. ;  Ueber  die 
von  V.  Kries  wider  die  Theorie  der  Gegenfarben  erhobenen 
Einwande,  Pfiuger's  Archiv,  xlii.,  pp.  488  ff. ;  xliii.,  pp.  264  ff., 
329  fif.  ;  Ebbinghaus,  Psychologic,  i.,  pp.  230  ff. 

(3)  Sir  I.  Newton  works  out  the  first  two  laws,  in  his 
Opticks,  Bk.  I.,  Part  ii.,  prop,  iv-vi,  Opera,  edition  of  1782,  iv., 
pp.  85-100.  The  third  law  was  formulated  by  H.  Grassmann, 
Zur  Theorie  der  Farbenmischung,  Poggendorff's  Annalen, 
Ixxxix.,  1853,  pp.  69-84;  Philos.  Mag.,  (4)  vii.,  1853,  pp. 
254-264. 

Instruments.  —  Helmholtz*  Spectrophotometer  is  described 
in  his  Physiol.  Optik,  2d  ed.,  pp.  355  ff.     For  a  cut  of  Hering's 


J  10.    Camptmctry  ly 

indirect-vision  colour  mixer,  see  p.  20  below.  K.  Marbe's 
colour  mixer  (with  change  of  sectors  during  rotation)  is  described 
in  the  Ann^  Psych.,  ii.,  1896,  752 ;  v.,  1899,  391  :  Zimmer- 
mann,  Mk.  100  or  140,  without  motor ;  Mk.  240,  with  motor. 

BXPERIMENT  n 

§  10.  Campimetry.  Cautions  not  noted  in  the  Text. — The 
distance  of  the  campiroeter  from  the  observing  eye  may  be  reg- 
ulated by  d7's  convenience.  It  must  neither  be  so  small  as  to 
bring  the  white  fixation-point  this  side  of  the  limit  of  clear  vision, 
nor  so  large  that  the  limits  of  the  zones  cannot  be  marked  upon 
the  various  meridians. 

Care  must  be  taken  that  O  can  balance  himself  in  an  easy 
and  steady  attitude.  A  very  slight  amount  of  bodily  discomfort 
will  distract  the  attention  in  these  experiments.  If  the  table  is 
too  low,  the  whole  apparatus,  colour  mixer  included,  may  be  raised 
upon  boards,  clamped  to  the  edges  of  the  table. — The  eye-rest 
must  be  accurately  adjusted  by  E,  so  that  the  centre  of  the  cir- 
cular opening  lies  directly  over  against  the  'yellow  spot,'  or 
*  spot  of  clearest  vision,*  when  the  eye  is  looking  straight  down- 
wards. —  The  illumination  should  be  so  regulated  that  no  shadow 
falls  upon  any  part  of  campimeter  or  stimulus  disc. 

When  black  is  added  to  the  brighter-looking  (or  white  to  the 
darker-looking)  colour,  in  exp.  (3),  the  proportion  of  the  coloured 
sectors  in  any  compound  disc  must,  of  course,  remain  unchanged. 
If  we  have  a  disc  of  278°  R  and  82°  B,  and  we  wish  to  add  in 
20°  VV,  our  resultant  disc  consists  of  262.5°  I^»  77-5**  B,  and  20® 
W.     The  ratio  R  :  B  remains  unchanged. 

If  a  mechanical  colour  mixer  is  employed,  three  students 
must  be  assigned  to  these  experiments :  an  (9,  an  E  who  shall 
move  the  fixation-mark,  etc.,  and  an  E  who  shall  rotate  the  discs. 
If  an  electric  motor  mixer  be  used,  one  E  is  sufficient. 

Where  the  mm.  scale  is  not  printed  on  the  campimeter,  the 
procedure  must  be  modified  a  little.  O  must  never  be  allowed 
to  see  the  white  strip.  In  exp.  (i),  a  pencil  line  ruled  on  the 
cardboard  may  serve  as  track  for  the  fixation-point,  and  a  pencil 
dot  may  mark  the  zone  boundaries.     Or,  if  the  *  step '  method  be 


1 8  Visual  Sensation 

employed  (see  below,  pp.  i8  f.)  the  .5  cm.  or  i  cm.  steps  may  be 
marked  beforehand  by  pencil  dots,  and  so  on. 

Since  the  retina  is  not  a  plane  surface,  but  a  portion  of  the 
inner  surface  of  a  hollow  sphere,  the  linear  values  obtained  for 
the  zones  on  the  different  meridians  should  be  translated  into 
degrees  and  minutes.  Two  distances  are  known  :  the  distance 
of  the  observing  eye  from  the  centre  of  the  circular  opening 
which  lies  directly  beneath  it,  and  the  distance  from  this  centre 
to  the  limit  of  the  zone  in  question.  The  ratio  of  this  latter 
distance  to  the  former  is  the  tangent  of  the  angle  enclosed  by 
the  line  of  regard  and  the  line  drawn  from  the  centre  of  the  cir- 
cular opening  to  the  eye.  Knowing  the  tangent,  we  know  the 
arc  subtended  by  the  angle.  The  value  of  this  arc  should  re- 
place the  linear  value  in  £''s  Tables.  This  is,  of  course,  a  purely 
mathematical,  not  a  psychological  exercise.  If  the  student  is  at 
all  pressed  for  time,  he  may  be  excused  from  performing  it.  The 
linear  determinations,  and  the  maps  draughted  from  them,  give 
all  the  necessary  psychological  facts.  If  the  calculation  is  made, 
it  is  desirable  to  have  the  maps  drawn  upon  the  printed  perimeter 
charts  sold  by  opticians. 

Experiment  (i).  —  Some  observers  find  it  more  natural  and 
less  fatiguing  to  move  the  eye  down  than  to  move  it  to  the  right. 
In  their  case  the  experiment  should  begin  not  with  the  right 
horizontal  meridian  (temporal  half  of  retina)  but  with  the  lower 
vertical  (lower  half  of  retina).  It  may  be  said,  in  general,  that 
downward  movement  of  the  eye  is  easier  than  upward,  and  out- 
ward movement  easier  than  inward.  The  left  horizontal  (nasal) 
meridian  is  the  most  difficult  of  all ;  partly,  no  doubt,  because 
the  blind-spot  causes  a  total  disappearance  of  the  opening  and 
colour  at  a  certain  point  upon  the  scale  (4  to  5  cm.,  in  the  ex- 
periments quoted  below). 

Again :  for  some  observers  it  is  almost  impossible  to  find  a 
rate  of  movement  of  the  fixation-point  which  shall  satisfy  the 
conditions  of  the  experiment  and  yet  not  allow  of  the  formation 
of  after-images.  Under  these  circumstances  it  is  better  to  move 
the  fixation-mark  by  definite  steps  (5  mm.  or  i  cm.),  and  to  make 
a  separate  experiment  at  each  step.     O  stands  with  his  closed 


§  lO,    Campimetry  19 

eye  settled  in  the  eye-rest ;  at  ^s  "  Now  ! "  he  opens  the  observ- 
ing eye,  and  turns  it  sharply  to  the  fixation-mark.  As  soon  as 
he  has  made  his  observation,  —  and  this  should  be  done  almost 
instantaneously,  —  he  turns  his  eye  back  to  its  original  position, 
and  closes  it.  The  observation  is  recorded ;  the  mark  quickly 
moved  out  one  step  farther ;  and  the  '•  Now !  **  at  once  repeated. 
A  series  of  experiments  performed  by  this  method  will,  of  course, 
require  more  time,  however  deftly  it  be  carried  out,  than  an  experi- 
ment performed  with  continuous  movement  of  the  fixation-point. 
The  following  are  records  of  actual  experiments.  All  measure- 
ments are  made  from  the  centre  of  the  campimeter  opening. 

Disc :  Hering's  *  red '  paper.     Height  of  eye-rest  above  screen,  14.3  cm. 

Left  Horizontal  Meridian.    (Nasal  retina.) 
Outgoing  mark  (from    1  cm.)  :  red  sensed  as  yellow  at    8  cm. 

4.  .4  it  I  U  «i  4<  U  ii  <i  Q        (( 

Incoming      "  -     11    "         «        "       "      red    «     7  « 

«<  u  ..      11      ((  u  u         t<  a       u      ^    u 

Outgoing      **  «      5    «         «        «       «    black  "  16  " 

u  a  u         q     44  u  «         «  u        u    1^    it 

Incoming     «  **     17    «         "        "       "  yellow"  13   ♦* 

Right  Horizontal  Meridian.     (Temporal  retina.) 
Outgoing  mark  (from     i  cm.)  :  red  sensed  as  yellow  at    5  cm. 

U  U  44  I         44  4(  it  M  U  U         ^     U 

Incoming      «  "     10    **  u        u       ..      red    «     4  " 

44  U  U,        iQ      U  ti  U  ..  4i        ^      it 

Outgoing      "  «      5    ii         i'  black  **   14  " 

.4  li         w     u  a  •'  "        «    I^    « 

Incoming      "  «     16    "         "        "       "  yellow"  13  " 

u  u  "16"  "  ««  u       u    12    ** 

Upper  Vertical  Meridian.    (Upper  retina.) 

Out£Oinfi[   mark  ^<V*«m      i  mi."^  :    red  sensed  as  vellow  at     T,  cm. 


u 

ti 

Incoming 

4i 

U 

44 

^     *^ 

4i 

t4 

il 

Outgoing 

4i 

u 
u 

^    black  -   12   " 

ti            u        *<     1 1     ^ 

Incoming 

u 
u 

u 
u 

13  " 

11      " 

ii 
a 

u 

"  yellow"  II   " 

u          u       u    12    ** 

20 


Visual  Sensation 


Lower  Vertical  Meridian.     (Lower  retina.) 
Outgoing  mark  (from     i  cm.)  :  red  sensed  as  yellow  at 


Incoming 

u 

Outgoing 

u 

Incoming 


u 

I 

« 

ii 

u 

4 

ii 

u 

4 

u 

u 

3 

« 

ii 

3 

« 

ii 

lO 

u 

as 

yellow  at 

2  cm 

<4 

U          ii 

2    « 

ti 

red    " 

I     " 

ti 

((       a 

2    " 

ii 

black  ** 

8   " 

i( 

ii       a 

8  " 

« 

yellow  « 

8   « 

10 


Fig.  2.  — The  Hering  indirect -vision 
colour  mixer.  Rothe,  Mk.  147. 
See  E.  Hering,  Arch.  f.  Ophthalm., 
XXXV.,  4,  1889,  63. 


Experiment  (2).  —  The  psycho- 
logical red  for  the  observer  A.  B. 
was  determined  as  Red  306°  + 
Blue  54°  (Hering's  papers).  Right 
eye  employed. 

(i)  Date  :  7/5/99.  3  P.M.^  Uniformly 
cloudy  sky. 

E:  X.  Y. 

O:  A.  B.     Condition  normal. 

Materials  :  Hering  indirect-vision  col- 
our mixer.  Red  and  blue  discs  (Hering's 
papers).  Grey  screen ^  no.  2.  White 
fixation-mark  on  black  straw.  Mm.  paper 
scale. 

Method:  Movement  of  fixation-point  by 
I  cm.  steps.  Measurements  taken  from 
centre  of  stimulus  circle  (centre  of  circle 
stamped  from  grey  screen).  Height  of 
eye-rest  above  screen  14.3  cm. 


Results:  Left  Horizontal  Meridian.     (Nasal  retina.) 

Outgoing  mark  (from    i  cm.)  :  red  sensed  as  black  at  15  cm.  (44°  43')* 
Incoming     "  "     20   "  «        <•'        "  red      "   14  "     (42°  50') 

Outgoing     "  «       I    «  «        "        "black"  15   «     (44^43') 

Incoming     "  «     20   «  "        "        «  red      "   15    "     (44°  43')' 

1  Good  results  can  be  obtained,  at  this  season  of  the  year,  in  the  early  morning : 
say,  from  5  to  7.30  a.m. 

*  Four  screens  are  given  with  the  Hering  mixer:  no.  i,  light  grey;  no.  2,  neutral 
grey;   no.  3,  dark  grey;   no.  4,  very  dark  grey. 

*  In  the  calculation  of  these  angular  values,  the  distance  of  the  campimeter  surface 
from  the  nodal  point  of  the  observing  eye  was  taken  as  15.  i  cm.  From  campimeter 
to  under  surface  of  eye-rest  was  14.3  cm.;  from  corneal  surface  to  nodal  point  is  ap- 


§  lO.    Campimetry  21 

(2)  Dait:  7/$/^.    Conditions  as  before. 

Right  Horizontal  Meridian.    (Temporal  retina.) 

Outgoing  marie  (from    i  cm.)  :  red  sensed  as  grey  at    9  cm.  (30**  48') 
Incoming    **  »•     15  **  *♦        ♦*       *♦  red    "    9  "     (30°  48') 

Outgoing      '*  .4         ,     a  u  u  H  grey   ««      9    a      (30**  48') 

Incoming    «*  **     15  "  «*        "       "  red    **    8  "    (27°  53') 

(3)  Doit:  7/5/99.    Conditions  as  before. 

Upper  Vertical  Meridian.    (Upper  retina.) 

Outgoing  mark  (from     i  cm.)  :  red  sensed  as  black  at  8  cm.  (2/*  53') 

'    i       '  7    "     (24^51') 

black  ••   8    **     (27^  53') 

"        «       «  red      *•  8   *<    (27"  53') 

(4)  ZW/;  7/5/99.    Conditions  as  before. 

Lower  Vertical  Meridian*.     (Lower  retina.) 
Outgoing  mark  (from    i  cm.)  :  red  sensed  as  black  at  6  cm.  (21°  40') 


Incoming    *• 

"     II 

Outgoing     « 

I 

Incoming    " 

«     II 

Incoming     " 

..       ,2     a 

u 

u 

u  red      "  7    "     (24°  51') 

Outgoing     " 

I     « 

u 

M 

"  black  "  6   «     (21°  40') 

Incoming    ^ 

"       12    " 

u 

M 

**  red      "  7    "     (24°  51') 

The  psychological  green  for  the  same  O  was  determined  as 
Green  230*"  4-  Blue  130°  (Hering's  papers).     Right  eye. 

(I)  Da£€:  11/5/99.     3  P.M.     Qoudy  sky. 

E:  X.  Y.  O:  A.  B.     Condition  normal. 

Materials:  As  before.     Green  and  blue  discs  (Hering's  papers). 
Method:  As  before.     Height  of  eye-rest  above  screen  14.3  cm. 

Results:  Left  Horizontal  Meridian.     (Nasal  retina.) 
Outgoing  mark  (from    i  cm.)  :  green  sensed  as  whitish  grey  at  16  cm.  (46°  24*) 
Incoming    "  **     20  **  "  «       "  green  *'  15   "     (44^43') 

Outgoing     "         a       ,    «  a         u       u  whitish  grey "  16  "     (46^24') 

Incoming    "         «     20  "  "         "       "  green  -14    *     (42^50') 

proximately  6  mm.;  and  the  corneal  surface  lay,  by  rough  measurement,  about  2  mm. 
above  the  under  surface  of  the  eye-rest.  —  The  blind  spot  falls,  as  we  saw  just  now, 
at  4  to  5  cm.  from  the  centre  of  the  campimeter  opening.  Thu  gives  an  angle  of 
18"  ao'  to  14°  48';  values  which  square  well  with  those  observed  by  Helmholtz  for 
<be  wkith  of  the  spot,  — 18"*  55'  to  12'  25'  (PhysioL  Optik,  2d  cd.,  p.  253). 


33  Visual  Sensation 

(2)  Date:  1 1/5/99.    Conditions  as  before. 

Right  Horizontal  Meridian.     (Temporal  retina.) 
Outgoing  mark  (from    i  cm.)  :  green  sensed  as  white  at  8  cm.  (27°  53') 


Incoming 

it 

ti 

18  " 

u 

a 

"  green-  7   "     (24°  S^') 

Outgoing 

it 

it 

I  " 

it 

tt 

"  white  "  8  «     (27°  S3') 

Incoming 

n 

tt 

18  " 

tt 

tt 

«  green  "  7  "     (24°  51') 

(3)  Date:  1 1/5/99.    Conditions  as  before. 

Upper  Vertical  Meridian.     (Upper  retina.) 

Outgoing  mark  (from    i  cm.)  :  green  sensed  as  white  at  9  cm.  (30°  48') 
Incoming    "         "11    "  "  "       "  green  "  7   "     (24°  51') 

Outgoing     «         "        I    «  "  «       "  white  "  8   "     (27=^  53') 

Incoming    «  "11    "  "  "       "  green  "  7   "     (24°  51') 

(4)  Date:  1 1/5/99.     Conditions  as  before. 

Lower  Vertical  Meridian.     (Lower  retina.) 

Outgoing  mark  (from    i  cm.)  :  green  sensed  as  white  at  7  cm.  (24°  51') 
Incoming     "  «      11    "  "         "       "  green  "  6  "     (21°  40') 

Outgoing     "  "        I    "  "  "       "  white  "  6   "     (21°  40') 

Incoming    «  «      11    "  "  "       "  green  "  5   "     (18°  20') 

Experiment  (3). — The  brightness-equation  of  the  primary 
red  and  the  primary  green,  for  the  observer  A.  B.,  right  eye,  was 
as  follows. 

(i)   Date :  T.'j / 1 / ^.     3  P.M.     Dull  grey  sky. 

£■;  X.  Y.  (9:  A.  B.     Condition  normal. 

Materials:   Two  colour  mixers.     Red,  blue,  green,  black  discs  (Her- 

ing's  papers). 
Red  306°  +  Blue  54°  =  Green  172°  +  Blue  98°  +  Black  90°. 

(2)  Conditions  as  before. 

Materials:  Hering's  indirect-vision  colour  mixer,  etc. 

Method:  As  in  previous  experiments.     Height  of  eye-rest,  14.3  cm. 

Right  Horizontal  Meridian.     (Temporal  retina.) 
Red.  Green. 

Outgoing :  sensed  black  at    9  cm.  (30°  48')   Sensed  black  at    8  cm.  (27°  53') 
Incoming:        "      red      "     8   "     (27^53')        "       green"     8   "     (27°  53') 

(3)  Left  Horizontal  Meridian.     (Nasal  retina.) 

Outgoing:  sensed  black  at  14  cm.  (42°  50')  Sensed  black  at  13  cm.  (40°  42') 
Incoming:       "      red      "   13   "     (40*^42')        "       green"  13   "     (40°  42') 


{  la    Campimehy  33 

(4)  Upper  Vbrtical  Mkridian.    (Upper  retina.) 
Outgoing:  sensed  black  at  10  cm.  (33"  31')  Sensed  black  at  10  cm.  (33**  31') 
Incoming:       ♦*      red     •*    8  «     (27*53')       **      green  »•    9  -    (30' 48') 

(5)  Lower  Vertical  Meridian.    (Lower  retina.) 
Outgoing:  sensed  black  at    7  cm.  (24*  51')  Sensed  black  at    8  cm.  (27*  53') 
Incoming:       •*      red     ♦*     7  *•     (24*^51')        »*      green*'    7  "     (24"*  51') 

An  experiment  made  upon  the  same  O,  under  similar  condi- 
tions, with  blue  and  yellow,  gave  the  following  results. 

(1)  Z\ilr:  24/5/99.     9  A.M.     Dull  sky. 
Blue  360'  =  Yellow  60*  +  Black  300*. 

(2)  Right  Horizontal  Meridian.  (Temporal  retina.)  Eye-rest  14.3  cm. 
Yellow :  out,  14  cm. ;  in,  13  cm.    Blue :  out,  14  cm. ;  in,  14  cm. 

(3)  Left  Horizontal  Meridian.    (Nasal  retina.) 
Yellow:  out,  11  cm. ;  in,  11  cm.    Blue:  out,  12  cm. ;  in,  10  cm. 

(4)  Lower  Vertical  Meridian.    (Lower  retina.) 
Yellow :  out,  9  cm. ;  in,  8  cm.    Blue :  out,  9  cm. ;  in,  8  cm. 

(5)  Upper  Vertical  Meridian.    (Upper  retina.) 

The  limit  of  the  colour-zone  in  this  experiment  lay  beyond  the  limits  of  the 
camptmeter.*     Approximate  values  were : 

Yellow :  in  and  out,  13  cm.     Blue :  in  and  out,  13  cm. 

Equations  employed  on  other  occasions  were : 

Yellow  254°  -f  Black  106"*  =  Blue  255°  -h  White  105*; 
185**+     "       175°=     •'     290**+      "        70°. 

It  will  be  noticed  that  the  blue  and  yellow  of  the  Hering  papers 
gave,  in  these  experiments,  the  primary  psychological  blue  and 
yellow,  whereas  the  red  and  green  of  the  papers  both  demanded 
an  intermixture  of  blue.  The  *  black '  of  the  experiments  is  the 
velvet-black,  not  the  black  tissue-paper,  of  the  Hering  series. 

Questions.  — (i)  The  reason  is.  that  the  extent  of  the  zones, 
though  constant  for  a  stimulus  of  given  extent  and  intensity, 

*  The  Hering  screens  are  69.6  cm.  long  by  33.3  cm.  wide.  The  circular  opening 
(1.4  on.  in  diameter)  b  to  placed  that  the  longitudinal  distances  on  either  tide  are 
27.9  and  4a3  cm.,  and  the  vertical  1 1.1  and  loJi  cm.,  retpectirely. 


24  Visual  Sensation 

shown  under  constant  illumination,  varies  with  variation  of  the 
extent  or  intensity  of  stimulus.  With  the  form  of  campimeter 
employed,  the  extent  of  the  stimulus  is  kept  constant.  But  we 
cannot  equalise  the  brightness-values  and  saturation-values  of 
the  coloured  papers.  The  red  disc  is  a  good  deal  brighter  than 
the  disc  composed  of  red  and  blue  (primary  red) :  hence  the 
red  zone,  as  marked  out  by  it,  is  wider  than  in  the  second  set  of 
experiments.  The  matter  is  further  complicated,  however,  by 
the  variability  of  the  general  illumination  of  the  stimuli.  The 
darker  the  day,  the  less  intensive  is  the  stimulus;  and,  conse- 
quently, the  smaller  are  the  colour-zones.  Hence  the  two  deter- 
minations may  approximate,  if  the  red  disc  is  given  on  a  dull 
day,  and  the  red-blue  (primary  red)  disc  on  a  bright  day.  The 
experiments  should  always  be  performed  in  diffuse  daylight,  and 
care  should  be  taken  to  have  the  conditions  of  illumination  as 
constant  as  possible.  —  Cf.  exp.  (3). 

(2)  The  advantages  are  two.  {a)  The  extent  of  the  coloured 
stimulus  remains  constant.  If  it  were  moved,  it  would  grow 
smaller  (subtend  a  smaller  angle  on  the  retina)  as  it  travelled 
out,  and  grow  larger  (subtend  a  wider  angle)  as  it  came  inwards. 
But,  as  we  have  seen,  the  extent  of  the  zones  varies  with  vary- 
ing extent  of  stimulus.  If  a  red  stimulus  were  employed,  then, 
the  boundary  of  the  blue-yellow  zone,  the  point  at  which  the  red 
turned  to  yellow,  would  be  brought  nearer  the  boundary  of  the 
innermost  efficient  zone  than  it  should  be  :  the  stimulus  at 
the  border  of  the  first  and  second  (efficient  and  blue-yellow) 
zones  would  be  more  extensive  than  at  the  border  of  the  second 
and  third  (blue-yellow  and  black-white)  zones,  {b)  If  we  keep 
the  coloured  stimulus  stationary,  we  can  use  the  colour  mixer, 
and  so  obtain  the  Urfarben.  If  the  stimulus  discs  could  not  be 
rotated,  we  should  be  obliged  to  content  ourselves  with  single 
pieces  of  coloured  paper :  and  it  would  be  only  by  the  merest 
chance  that  we  found  a  coloured  paper  which  gave  an  Urfarbe. 
A  campimeter  could,  certainly,  be  made,  which  should  allow  of 
movement  of  the  colour  mixer  along  its  meridians  ;  but  it  would 
be  a  costly  and  elaborate  instrument. 

The  disadvantage  is,  that  (9's  eye  soon  becomes  fatigued  by 
the  unusually  extensive  movements  which  it  is  called  upon  to 


§  la   Campinutry  25 

make.  The  experiment  consequently  requires  a  considerable 
amount  of  time  for  its  performance. 

(3)  Na  Objects  seen  in  indirect  vision,  under  the  conditions 
of  the  rough  test  proposed,  are  seen  in  their  normal  colours. 

The  explanation  of  this  fact  belongs  to  the  psychology  of 
perception,  not  to  that  of  sensation.  It  may  be  stated  as  fol- 
lows.—  All  the  objects  to  which  we  turn  our  attention  in  indi- 
rect vision  (to  which  we  attend  though  we  are  looking  else- 
where) are  localised,  i>.,  arc  seen  as  situated  at  different  places, 
lying  in  different  positions.  The  group  of  sensations  composing 
an  'object'  has  attached  to  it  a  Mocal  mark'  or  Mocal  sign.' 
The  local  sign  is,  in  all  probability,  derived  from  two  sources. 
(a)  The  eye  is  a  moving  org^n,  and  turns  naturally  to  the  object 
of  attention.  If  it  is  held  fixed,  there  is  still  a  tendency  to  turn 
it  towards  the  object  of  attention.  The  tendency,  if  it  were 
itself  made  the  subject-matter  of  introspection,  would  reveal 
itself  as  a  memory-image  of  the  organic  sensations  set  up  round 
about  the  eyeball  by  actual  movement,  by  the  actual  turn  of  the 
eye  towards  the  object  of  attention.  The  organic  sensations 
evidently  differ  in  extent  and  intensity,  according  to  the  locality 
of  the  object  towards  which  the  eye  is  turned ;  and  their  mem- 
ory-images diflFer  in  a  similar  manner,  {b)  The  retina,  as  this 
experiment  has  shown  us,  yields  different  colour  sensations 
according  as  the  coloured  object  mirrors  itself  upon  the  inner- 
most, middle,  or  outer  retinal  zone.  —  These  two  things,  the 
special  memory-image  of  a  special  movement  and  the  special 
colour-tint  of  a  special  zone,  apparently  fuse  or  weld  together  to 
constitute  the  local  sign  in  each  particular  case.  Neither  mem- 
ory-image nor  colour-tint  is  experienced  singly,  as  itself;  the 
fusion  of  the  two  is  experienced  as  a  conscious  *thereness.' 
We  do  not  note  the  colour  differences,  then,  in  the  sense  that 
we  do  not  see  objects  in  zones  of  colour  corresponding  to  the 
retinal  zones  :  we  eb  note  them,  if  the  theory  here  outlined  is 
correct,  in  the  sense  that  we  perceive  the  objects  about  us  as 
placed  in  different  positions.  The  colour  differences  are  lost  to 
the  psychology  of  sensation  :  we  can  remark  them  as  such  only 
under  artificial,  experimental  conditions :  they  reappear,  in  an- 
other guise,  in  the  psychology  of  visual  space  perception.    This 


26  Visual  Sensation 

is  one  of  the  chief  problems  of  experimental  psychology,  —  to 
unearth  the  elementary  processes  buried  in  perception  and  idea ; 
to  identify  them,  in  spite  of  all  the  changes  of  function  that 
they  evince  when  connected  with  other  elementary  processes  to 
form  a  single  complex. 

(4)  The  arrangement  suggests  that  black-white-grey  vision  is 
the  earliest  form  of  visual  sensation  ;.that  blue  and  yellow  were 
next  developed ;  and  that  red  and  green  are  the  latest  colours 
that  vision  has  acquired. 

We  know  that  ordinary  partial  colour-blindness  is  red-green 
blindness :  red  and  green  are  the  first  colours  to  be  lost.  This 
is  natural,  if  they  are  the  last  to  be  gained.  Again :  a  number 
of  cases  of  total  colour-blindness  have  been  described ;  cases  in 
which  nothing  is  seen  but  the  black-white-grey  series.  Again  : 
if  one  is  blind  to  black-white-grey,  one  is  wholly  blind  :  no 
cases  exist  of  black-white-grey  blindness  with  retention  of  colour 
vision.  All  this  is  direct  evidence  in  favour  of  the  theory  sug- 
gested, and  there  is  much  indirect  evidence  besides. 

On  the  other  hand,  the  theory  would  require  modification  if  it 
could  be  proved  that  certain  people  are  blue-yellow,  but  not  red- 
green  blind.  Statements  to  this  effect  are  sometimes  made ; 
but  no  demonstrative  proof  has  been  brought  forward.  We 
must  therefore  suspend  our  judgments,  until  further  investiga- 
tions have  been  carried  out.  In  the  meantime,  however,  we 
have  the  full  right  to  say  that  the  trend  of  all  valid  testimony, 
so  far,  is  in  favour  of  our  theory. 

Literature.  —  Ebbinghaus,  Psych.,  i.,  191  ;  Helmholtz, 
Physiol.  Optik,  2d  ed.,  372-374 ;  E.  Hering,  Ueber  die  Hypoth- 
esen  fur  Erklarung  der  peripheren  Farbenblindheit,  Arch.  f.  Oph- 
thalmologic, xxxv.,  4,  1889,  63  ff.  ;  xxxvi.,  i,  1890,  264;  C.  Hess, 
Ueber  den  Farbensinn  bei  indirektem  Sehen,  Arch.  f.  Ophthal- 
mologic, xxxv.,  4,  1889,  I  ff. ;  A.  Kirschmann,  Philos.  Studien, 
viii.,  1893,  592  ;  Wundt,  Phys.  Psych.,  i.,  505. 

Instruments.  —  Wundt's  large  perimeter  for  rotating  discs 
(made  by  Zimmermann,  Mk.  350)  is  figured  in  the  Philos.  Stu- 
dien, XV.,  1900,  526. 

§  II.  Belated  Experiments. — (i)  Since  our  work  upon  the 
nasal  horizontal  meridian  has  reminded  us  of  the  existence  of 


$  II.    Tke  Blind  Spot  27 

the  blind  spot,  it  may  be  worth  while  to  make  it  the  subject  of 
experiment. 

\d)  M€^ping  the  Blind  Spot  —  O  sits  at  a  distance  of  about 
2  m.  from  a  wall  or  screen,  his  chin  supported  in  a  head-rest, 
and  his  right  eye  closely  (but  not  too  tightly)  bandaged.  On 
the  wall  is  spread  a  sheet  of  heavy  white  paper,  i  m.  by  55  cm. 
In  the  right  hand  upper  comer,  20  cm.  from  the  upper  and  10 
cm.  from  the  outer  edge  of  the  sheet,  is  drawn  a  heavy  black 
cross,  with  3  cm.  arms.     This  is  the  fixation-mark. 

On  the  left  hand  part  of  the  sheet  a  point  is  lightly  marked 
in  pencil,  27.5  cm.  from  the  upper,  and  30  cm.  from  the  outer 
edge.  Through  this  as  centre  are  ruled  four  diameters  of  a 
circle  of  25  cm.  radius :  vertical,  horizontal,  and  two  oblique. 

E  has  a  light  rod  or  bit  of  stiff  card,  covered  with  paper  of 
the  same  kind  as  the  sheet  and  carrying  at  its  tip  a  disc  of 
black  paper,  2  cm.  in  diameter. 

For  the  experiment,  O  sits  with  his  open  eye  directly  opposite 
the  fixation-mark.  E  slowly  passes  the  black  disc  along  one  of 
the  ruled  lines  (direction  indifferent).  O  calls  out  at  the  mo- 
ment that  the  black  disc  enters  the  blind  spot  (disappears),  and 
again  at  the  moment  that  it  emerges  from  the  spot  (reappears). 
E  makes  light  pencil  marks  upon  the  sheet  at  these  points  ;  it  is 
best  to  put  a  figure,  showing  the  number  of  the  test,  and  a 
small  arrow,  showing  the  direction  of  movement. 

This  procedure  is  repeated  until  each  of  the  meridians  has 
been  worked  over  twice  (once  in  each  direction).  The  two 
marks  (ingoing  and  outcoming)  at  any  given  point  will  not,  of 
course,  exactly  coincide.  If  there  were  nothing  else  to  prevent, 
there  would  still  be  the  width  of  the  disc :  for  O  does  not  call 
out  till  the  disc  has  wholly  disappeared,  whereas  he  will  call  out 
as  soon  as  ever  a  margin  of  it  reappears.  The  outline  of  the 
projection  of  the  spot  must,  therefore,  pass  through  points  lying 
midway  between  these  two.  If,  however,  two  determinations  at 
any  point  show  very  considerable  divergence,  the  tests  along 
the  meridian  in  question  should  be  repeated. 

The  number  of  meridians  may  be  increased,  if  increased 
accuracy  of  outline  be  desired.  If  the  student  wish,  e.g,,  to 
trace  the  great  vessels  that  enter  the  eye  with  the  nerve,  he 


28  Visual  Sensation 

must  work  very  carefully  over  the  part  of  the  spot  that  lies 
above  the  fixation-mark,  and  over  the  lower  portion  of  its  inner 
(right  hand)  boundary  line. 

Figures  of  the  blind  spot  are  given  in  Helmholtz,  Physiol. 
Optik,  2d  ed.,  252  ;  Titchener,  Outline  of  Psychology,  1899,  176. 

{b)  The  Filling-out  of  the  Blind  Spot.  —  In  ordinary  binocu- 
lar vision,  the  area  that  is  blind  in  the  one  eye  is  able  to  see  in 
the  other ;  so  that  the  existence  of  the  blind  spot  need  not  be 
remarked.  In  ordinary  monocular  vision,  the  eye  moves  so 
much  as  a  matter  of  course,  and  the  blind  spot  lies  so  far  later- 
ally from  the  spot  of  clearest  vision  (covering  the  space  from 
about  12°  to  18°  nasal  wards  from  the  centre  of  the  macula 
lutea),  that  again  its  existence  need  not  be  remarked.  But  when 
we  are  under  experimental  conditions,  and  have  mapped  the 
spot,  we  may  go  on  to  ask  whether  (and  if  so,  with  what)  the 
blind  spot  is  filled  out. 

(i)  If  the  blind  spot  were  not  filled  out,  its  edges  would  come 
together,  and  there  would  be  a  shrinking  of  space-values  over 
this  area  of  the  retina.  Although  such  a  shrinking  has  in  fact 
been  reported  by  some  observers,  it  seems  to  be  due  rather  to  a 
•  suggestion '  from  the  blind  spot  itself  than  to  actual  observa- 
tion.    The  following  tests  may  be  made.^ 

a.  Paste  on  a  card  nine  large  letters,  as  follows : 

ABC 
D  E  F 
G     H     I 

Set  up  the  card  at  such  a  distance  that  E  falls  upon  the  blind  spot,  while  all 
the  other  letters  are  visible.  Notice  that  the  letters  ABCFI HGD  form  a  square ; 
that  there  is  no  bending  inwards  of  the  boundary  lines  of  the  whole  figure. 

b.  Paste  on  a  card  a  horizontal  line  of  three  wafers,  1.5  cm.  in  diameter, 
the  middle  one  blue  and  the  two  others  red.  Set  up  the  card  at  such  a  dis- 
tance that  the  blue  wafer  disappears,  while  the  reds  are  seen.     Notice  that 

1  White  cards,  15  by  10  cm.,  upon  which  the  letters,  circles,  etc.,  can  be  pasted, 
are  convenient  for  these  experiments.  The  distance  from  the  centre  of  the  fixation- 
cross  to  the  near  edge  of  the  figure  intended  to  fall  upon  the  blind  spot  may  be  taken 
at  about  8.5  cm.  —  A  set  of  four  such  cards,  designed  by  E.  W.  Scripture,  is  sold  for 
15^  by  E.  G.  Willyoung,  82-84  Fulton  Street,  New  York.  Unfortunately,  the  fixation- 
marks  on  these  cards  are  printed  too  low. 


§  II.    The  Blind  Spot  29 

the  instance  between  the  two  reds  does  not  seem  to  shrink;  the  wafers  do 
not  run  together. 

r.  Paste  upon  a  card  50  cm.  long  a  central  fixation-mark,  and  on  either  side 
uf  it,  rather  lower  down  and  at  a  distance  of  9  cm.,  a  coloured  ring  large 
enough  to  surround  the  blind  spot.  Set  up  the  card  at  such  a  distance  that 
the  blind  spot  does  as  a  matter  of  fact  fall  entirely  within  one  of  the  circles. 
Notice  that  this  circle  (nasal  retina)  docs  not  appear  smaller  than  the  other 
(temporal  retina). 

These  experiments  can  be  varied  at  will.  In  a^  t.g.y  a  single  line  may  be 
drawn  through  the  blind  spot.  Is  it  shortened?  Or  parallels  may  pass 
through  it.  Do  they  converge  on  entering  and  diverge  on  leaving  the  spot? 
Or  a  square  of  small  letters  may  be  used,  and  two  of  these,  on  either  side  of 
the  spot,  made  the  objects  of  special  attention.  Are  they  drawn  together?  — 
In  ^,  the  colours  of  the  wafers  may  be  varied,  or  their  number,  size,  shape, 
etc.     The  student  should  make  a  series  of  these  cards  for  himself. 

(ii)  The  blind  spot,  then,  has  the  same  spatial  value  as  the 
irrounding  portion  of  the  retina.     How  is  it  filled  out  ?    When 

It  falls  upon  an  uniform  ground,  it  is  filled  out  by  the  quality  of 

that  ground  :  here  all  observers  agree. 

a.  Paste  on  a  card  a  coloured  ring,  large  enough  to  contain  the  blind  spot 
within  its  outer,  but  so  wide  as  not  to  allow  the  spot  to  fall  entirely  within  its 
inner  ciromiference.  Notice  that  the  whole  surface  appears  in  the  colour  of 
the  ring. 

The  same  thing  occurs  with  only  partially  uniform  surfaces. 

b.  Substitute  for  the  coloured  ring  a  ring  cut  from  a  newspaper.  Notice 
that,  at  any  rate  until  practice  has  advanced  a  considerable  disUnce,  the  whole 
surface  seems  to  be  filled  out  with  printed  letters. 

On  the  other  hand,  our  judgment  in  the  case  of  surfaces  that 
are  widely  different  seems  to  be  a  function  of  our  skill  and 
practice  in  indirect  vision. 

c.  Cover  a  card  over  9  cm.  of  its  length  with  a  neutral  grey  paper.  Over 
this  lay  a  rectangular  cross,  of  9  cm.  arms ;  let  the  vertical  arm  be  white  and  the 
horizontal  black.     Where  the  arms  cross,  they  must  be  mitred ;  not  left  square. 

Prepare  similar  cards  with  the  horizontal  arm  white  and  the  vertical  black, 
and  with  the  two  arms  of  different  colours. 

Prepare  two  sets  of  cards,  in  the  one  of  which  the  length  of  the  total  hori- 
zontal arm  decreases  by  i  cm.  at  each  step,  and  in  the  other  of  which  the 
vertical  decreases  in  the  same  ratio,  —  until  only  the  triangle  of  the  mitre  is 
left  in  each  case. 


30  Visual  Sensation 

Set  the  cards  up  at  such  a  distance  that  the  centre  of  the  cross  falls  within 
the  area  of  the  blind  spot.    What  is  seen? 

Unpractised  observers  generally  assert  that  they  see  one  of  the  arms  going 
right  across  the  other,  and  (for  the  most  part)  the  horizontal,  —  perhaps 
because  the  horizontal  diameter  of  the  spot  is  less  than  the  vertical.  As  the 
two  arms  are  decreased,  this  judgment  varies,  until  (with  sufficient  shortening) 
the  smaller  arm  is  entirely  merged  in  the  greater.  Highly  practised  observers, 
on  the  other  hand,  declare  that  they  are  unable  to  decide  how  the  centre  of 
the  figure  is  filled  out ;  they  cannot  see  the  crossing-point  at  all. 

We  cannot  here  enter  upon  the  theory  of  these  phenomena. 
See  Helmholtz,  Physiol.  Optik,  2d  ed.,  717-727;  Aubert,  Physi- 
ologie  der  Netzhaut,  257  f.  ;  Wundt,  Physiol.  Psychol.,  4th  ed., 
ii.,  103  f.  ;  Hering,  in  Hermann's  Hdbch.,  iii.,  i,  374. 

(2)  The  Determination  of  the  Macula  Ltitea.  —  The  pigmenta- 
tion of  the  yellow  spot  may  exert  an  effect  upon  colour  vision. 
This  is  why  E  was  told,  in  the  campimetrical  experiments,  to 
start  his  fixation-mark,  not  from  the  centre  of  the  opening,  but 
from  a  point  lying  about  i  cm.  from  its  centre. 

There  are  various  ways  of  bringing  the  yellow  spot  to  vision, 
but  the  following  are  best  adapted  to  showing  its  colour  values. 

Make  a  saturated  solution  of  chrome  alum.  Filter.  Dilute 
until  the  liquid  is  a  pale  slate  blue.  Pour  into  a  fiat-sided  medi- 
cine bottle.  Hold  the  bottle  close  before  the  eye,  and  look  at  a 
brightly  illuminated  window.  The  macula  lutea  appears  as  a 
small  rose-coloured  spot  in  the  midst  of  the  blue.  The  size  of 
the  spot  depends  upon  the  distance  to  which  it  is  'projected.' 
To  the  author,  and  to  most  of  the  6^'s  whom  he  has  tested,  it  is 
about  as  large  as  a  pea;  other  6^'s  declare  that  it  is  as  large  as  a 
quarter-dollar. 

The  same  experiment  may  be  performed  with  purple  gelatine 
sheets.  —  See  Helmholtz,  Physiol.  Optik,  567  ff.  ;  Hering, 
Pfliiger's  Arch.,  liv.,  1893,  277;  Sanford,  Course,  100,  105. 

EXPERIMENT  IH 

§  1 2.  Visual  Contrast.  Cautions  not  noted  in  the  Text.  —  Two 
things  are  necessary  in  these  experiments :  a  power  of  steady 
fixation,  and  an  ability  to  match  the  brightness  of  a  colour  and 
a  grey.     Experiment  (i)  gives  good  training  in  the  former,  if  O 


§  II.    Vtstta/  Contrast  31 

is  not  sufficiently  trained  by  the  foregoing  campimetrical  experi- 
lents.  The  matching  of  greys  and  colours  is  not  altogether 
easy  (cf,  the  matching  of  colours  for  brightness,  in  Exp.  II.), 
though  it  is  not  either  so  difficult,  after  practice,  as  it  may 
appear  at  first  trial.  Experiment  (2)  should  afford  sufficient 
practice,  even  if  Exp.  II.  has  not  yet  been  performed.  And  the 
matching  needed  for  our  experiments  is  not  of  a  very  exact  kind. 
Throughout  the  experiments,  O  must  be  constantly  on  his 
guard  against  after-images.  His  decisions  must  be  prompt ;  and 
a  time  of  at  least  3  min.  should  be  left  between  judgment  and 
judgment.  It  is  well  to  agree  on  a  pause  of  this  duration  be- 
forehand, that  E  may  not  become  flurried  while  adjusting  the 
second  disc  to  match  the  contrast  colour. 

All  the  colour-mixer  experiments  of  this  section  are  open  to  the  charge  that 
successive  contrast  is  not  excluded :  cf.  the  theoretical  objection  to  coloured 
papers  in  Exp.  I.  In  practice,  with  a  careful  O,  this  source  of  error  may  be 
neglected. 

Experiment  ( I ).  —  As  soon  as  the  white  card  appears  trom 
beneath  the  '  black  *  strip,  this  strip  suddenly  darkens.  O,  keep- 
ing his  fixation  constant,  is  thus  able  to  compare  the  brightness 
of  the  same  'black'  upon  a  white  and  a  black  ground.  The 
effect  is  very  striking.  —  The  experiment  is  described  by  Hering, 
Zur  Lehre  vom  Lichtsinne,  23  f. 

It  is,  of  course,  possible  to  measure  contrast-effects  of  this  kind.  And  we 
could  get  matches  for  ttiduced  brightnesses  as,  in  the  later  part  of  this  Elxperi- 
ment,  we  get  matches  for  induced  colours.  But  it  is  better  to  postpone  this 
experiment  until  vol.  ii.,  where  it  can  be  worked  out  methodically,  and  with 
the  aid  of  pbotometrical  formulae. 

(2)  Every  grey  is  tinged  with  the  complementary  colour.  We 
use  the  tissue  paper  to  eliminate  contours.  The  experiment  is 
described  by  H.  Meyer,  Poggendorff*8  Annalen,  xcv.,  1855,  170 
f. ;  Phil.  Mag.,  ser.  4,  ix.,  547. 

It  is  commonly  supposed  that  the  chief  effect  of  the  tissue 
paper  in  this  experiment  is  to  lessen  the  saturation  of  the  induc- 
ing ground ;  and  that,  consequently,  we  get  better  contrasts  from 
less  saturated  than  we  do  from  more  saturated  colours.  This 
proposition  is  negatived  by  exp.  (4);. but  we  can  disprove  it 


32  Visual  Sensation 

here  by  a  very  simple  variation  of  Meyer's  experiment.  Lay 
the  grey  over  the  coloured  paper,  without  using  the  tissue  :  note 
the  degree  of  contrast.  Now  lay  the  tissue  on  the  coloured 
paper,  and  the  grey  on  the  tissue.  The  degree  of  contrast  is 
lessened.  —  All  that  the  tissue  laid  over  both  papers  can  do, 
then,  by  way  of  enhancing  contrast,  is  to  eliminate  contours. 

(3)  The  grey  papers  that  are  sold  as  grey  are  nearly  always 
slightly  tinged  with  brown  or  blue  ('stone  greys'  or  *  slate  greys '). 
And  it  may  not  be  possible  to  find  a  paper  that  is  not  noticeably 
lighter  or  darker  than  the  coloured  disc.  E  must  do  the  best 
he  can  with  his  materials,  noting  the  above  points  (if  they  are 
realised)  as  constant  errors  in  his  experimental  series. 

The  distance  of  O  from  the  discs  must  be  such  that  the  in- 
duced colour  shows  no  marginal  contrast.  This  distance  will,  if 
papers  like  those  of  Hering  are  used  and  the  work  is  done  in 
diffuse  daylight,  be  somewhere  about  2  m.  O  should  fixate  the 
centre  of  the  disc,  —  not  the  coloured  ring.  Not  only  should 
the  experiment  be  repeated  with  different  colours,  but  for  each 
single  colour  5  tests  should  be  made,  if  time  allow,  and  the 
amount  of  the  contrast-effect  averaged  from  the  separate  results. 

E  is  told  in  the  text  to  work  methodically.  It  will,  however, 
materially  shorten  the  experiment,  and  do  no  harm,  if  the  In- 
structor give  him  some  hint  as  to  the  composition  of  the  con- 
trast match.  When  he  has  made  the  general  match  roughly,  E 
should  first  work  for  an  exact  brightness  match,  and  only  when 
this  has  been  obtained  seek  to  match  the  colours  accurately.  It 
is  easier  to  vary  sectors  for  colour,  when  the  brightness  is  fairly 
good,  than  to  vary  them  for  brightness,  after  the  colour  match 
has  been  achieved. 

The  following  results  were  obtained  with  the  Hering  discs : 

{a)  Green  induces  on  ring  of  120^  W  and  240°  B  a  Purple  of  40°  Blue,  55°  Red, 

70°  Band  195°  W. 
(^)   Red  induces  on  ring  of  125°  W  and  235°  B  a  Verdigris  of  60°  Green,  40° 

Blue,  80°  Band  180°  W. 
{c)   Blue  induces  on  ring  of  55°  W  and  305°  B  a  Yellow  of  31°  Red,  60°  Yellow, 

200°  B  and  69°  W. 
(</)  Yellow  induces  on  ring  of  270°  W  and  90°  B  a  Blue  of  24°  Green,  71°  Blue, 

50°B  and  2i5°W. 


§  la.    yifsua/  Contrast 


33 


These  figures  will  serve  as  a  rough  guide  to  the  composition  of 
the  contrast  matches,  and  to  the  brightness  values  of  the  coloured 
papers. 

(4)  The  following  Table  of  results  ^Hcrmg  papers)  furnishes 
all  the  necessary  comment  upon  this  experiment : 


(«)  GMn 

<#)9oePG.    sc^W.  4o>Bk 

(r)a«c/>G,    41^  W,  8o»Bk 

(#)  iad<>G.    I^W.  ifiaPBk 

CO  hiPG,  toePW,  tatfiVk 


RlM 


iM»W.  M</>Bk 
(  ttfOW,  «0»  Bk)  •»- 100°  W.  MK/>Bk 
(  4(PW,  loOBk)-)-  80PW.  t6«/>Bk 
(  <aPW.  iMOBk)-!-  6o»W,  ili^Bk 
(  loPW,  i6(/>Bk)-t>  4o3W,  S(/>Bk 
(too»  W.  KioP  Bk)  •*-  »/>W,  4oPBk 
(iioaW.«»oBk)4.   loOW.     aoPBk 


«o^B,550R.  yoPBk.i95«W 
y^B.  4«»R.  71^  Bk.  ttgOW 
•3*'  B,  330  R,  710  Bk.  1330  W 
mP  B.  ago  R,  7*0  Bk.  #39°  W 
170  B.  ifO  R.  7*0  Bk.  u^"  W 
lao  B.  mo  R.  730  Bk.  »S3''  W 
««>  B.  i$<>  R.  7s«  Bk.  »64*  W 


irW.  4aOBk 

]6»  W,  84<>  Bk 

S40W,  is^Bk 

y«oW.  i6rBk 

90<>W.  >ioOBk 

99»W.  t3tOBk 


(  trW,  4tOBk) 
(  36«W.  84°  Bk) 
(  S4''  W.  ta6'>  Bk) 
(  7^  W.  i6B'>  Bk) 
(  9«^W..K/>Bk) 
(  99''W..3iOBk) 


170OW,  9c^Bk 

«$*'W.  7s«>Bk 

liffiW,  toPBk 

135°  W,  ♦jOBk 

90^  W.  jo^Bk 

45OW.  isOBk 

ns^W,  7.50Bk 


t4®G,  71®  B,  5«/>Bk,  115OW 
•aPG,  560B,  56°  Bk,  m6«W 
i«oG.  47°  B,  59°  Bk.  «36o  W 
13"  G.  yPB.  63°Bk.  154°  W 
i|OC.  a30B.  es^Bk.  a6i«W 
r>G.  »oPB.  66°  Bk,  •66'' W 
50G.  ii">B,  670Bk,  t770W 


It  is  evident  that  the  saturation  of  the  induced  colour  varies 
directly  with  that  of  the  inducing. 

(5)  This  experiment  is  a  good  deal  more  difficult  than  any  of 
the  preceding.  Despite  the  high  degree  of  saturation  of  the 
marginal  contrast  colour,  many  observers  are  unable,  without 
practice,  to  keep  the  attention  upon  the  coloured  line  steadily 
enough  to  compare  it  with  the  other  disc.  Complementary 
after-images  may  be  exceedingly  troublesome  here :  the  O  of  the 
results  quoted  below  referred  to  them  as  'satanic*  It  is  well  to 
give  O  a  head-rest,  and  to  insist  very  strongly  that  fixation  is  not 
to  wander  from  the  centre  of  the  smaller  disc.  Prompt  judgment 
is  indispensable. 

Under  such  circumstances  it  is  advisable  to  repeat  each  test 
some  6  times  over,  and  to  average  the  results.  With  a  good 
observer,  however,  the  variation  from  test  to  test  is  but 
slight. 

The  following  Table  shows  some  marginal  contrasts,  obtained 
with  Hering  discs,  and  compares  them  with  the  diffused  con- 
trasts obtained  with  the  same  discs  in  experiment  (3): 


34 


Visual  Sensation 


(tf)  Green.      Brightness  match  :  I20°W,  24o°Bk. 


40°  B,  55°  R,    70°  Bk,  195°  W. 
Bk,  177"  W. 


(i)  Diffused  purple  induced : 

(2)  Marginal     "  "  47°  B,  80°  R,    56° 

(b)  Yellow.     Brightness  match :  270°  W,    90°  Bk. 

( 1 )  Diffused  blue  induced :  24°  G,  7 1  °  B,    50^*  Bk,  2 1 5°  W. 

(2)  Marginal  «  •'  30°  G,  90''  B,    40°  Bk,  200°  W. 
(0  Red.         Brightness  match :  125°  W,  235°  Bk. 

(1)  Diffused  verdigris  induced  :     60°  G,  40°  B,    80°  Bk,  180°  W. 

(2)  Marginal      "  "  74°G,  40°B,    8o°Bk,  i66°W. 
(^)  Blue.         Brightness  match  :     55°W,  305°Bk. 

(1)  Diffused  yellow  induced :         31°  R,  60°  Y,  200°  Bk,    69°  W. 

(2)  Marginal     "  "  35°  R,  80°  Y,  198°  Bk,    47°  W. 

(6)  There  is  little  difficulty  in  this  experiment,  beyond  the 
difficulty  of  manipulating  the  discs.  It  is  well  to  have  several 
sets  ready,  with  the  various  rings  pasted  on  beforehand. 

The  following  results  are  characteristic  : 

Inducing  colour :  Green 


Ring 


Induced  colour 


{a)  I20°W,  240°Bk 
{b)  90°  W,  270°  Bk 
{c)  60°  W,  300°  Bk 
{d)    30°W,  330°Bk 


4o°B,  55°R,  7o°Bk,  i95°W 
27^B,  37°R,  143°  Bk,  153°  W 
18°  B,  27°R,  250^Bk,  65°  W 
15°  B,  18°  R,  290°  Bk,    37°  W 


{a)  i5o°W,  2io°Bk 
lb)  180°  W,  180°  Bk 
(0  210°  W,  150^  Bk 
\d)  240°  W,  120°  Bk 
{e)  270°  W,  90°  B 
(/)  300°  W,  60"  Bk 
(g)  330^  W,    30^  Bk 


30°B,  5o°R,  62°Bk,  2|8^W 

20"  B,  45°  R,  56°  Bk,  239°  W 

I5°B,  42°R,  5o°Bk,  253°W 

io°B,  4i°R,  48°Bk,  26i°W 

8°  B,  38°  R,  46°  Bk,  268°  W 

6°B,35°R,  44°Bk,275°W 

4°B,  32°R,  4o^Bk,  284°W 


It  is  clear  that  the  contrast-effect  decreases  with  introduction  of 
brightness  contrast,  whichever  direction  this  may  take.  There 
is  good  reason,  then,  for  our  care  to  avoid  brightness  contrasts 
in  the  previous  colour  experiments. 

(7)  and  (8)  Neither  of  these  experiments  is  quite  easy.  O 
will  have  grown  so  used  to  the  rotating  discs,  thai  the  contrast- 
colour  of  the  stationary  disc  will  be  hard  to  estimate.     And  the 


§  12.    Visual  Contrast  35 

tissue-paper  front  of  the  discs  in  (8)  is  distracting  to  the  atten- 
tion. On  the  other  hand,  the  effects  are  very  striking,  when 
once  O  is  sufficiently  trained  to  observe  them.  The  tissue-cov- 
ered disc  seems  rather  to  be  transmitting  than  to  be  reflecting 
light ;  the  contrast  colour  seems  purer,  as  it  were  a  more  positive 
colour,  than  it  has  done  in  previous  experiments. 
The  following  results  are  characteristic  : 

{a)  Green,  without  tissue  paper,  induces  40"  B,  55°  R,    70**  Bk,  195®  W 

(*)       -  with  **  "  "48*'  B,  ys**  R,    45*'  Bk,  192^  W 

(c)   Red,  without  «  "  6o'»G,  40*'B»    8o°Bk,  iSo^W 

(«/)    «*  with  »*  a  u       8o°G,55"B,    5o°Bk,  I75*W 

(0    Blue,  without  **  "  *»       31**  R,  60"  Y,  200°  Bk,    69°  W 

(/)     **  with  u  u  **       35°  R,  78°  Y,  1 12°  Bk,  135^  W 

ig)  Yellow,  without  "  "  24°  G,  7 1  °  B,    50°  Bk,  2 1 5**  W 

{k)       "  with  "  27*G,92*'B,   4o''Bk,20i*»W 

It  will  be  seen  that  the  values  of  exp.  (8)  equal  or  exceed  the 
values  obtained  for  marginal  contrast  in  exp.  (5).  This  is  the 
rule,  — although  some  observers  give  relatively  higher  values  to 
the  marginal  contrasts  than  were  given  by  the  O  of  the  results 
cited. 

It  may  be  mentioned  here  that  all  the  results  of  this  Experi- 
ment  were  obtained  from  the  same  O^  under  (as  nearly  as  pos- 
sible) like  conditions  of  illumination.  The  conditions,  indeed, 
cannot  have  varied  much :  for  the  brightness  match  of  the 
standard  colours  was  tested  before  every  partial  experiment,  and 
(as  the  quotations  show)  remained  true  throughout. 

Questions. — (i)  Contrast  is  present  at  once,  as  soon  as  the 
discs  are  displayed.  If  a  contrast  disc  be  set  in  rotation,  covered 
by  a  screen,  and  then  suddenly  shown  to  a  person  who  is  ignorant 
of  its  actual  composition,  it  will  be  described,  without  hesitation, 
as  bicoloured. 

(2)  Precisely  the  same  laws  would  hold.  Each  colour  would 
modify  the  other  in  the  direction  of  its  own  antagonistic  col- 
our; the  contrast-effect  would  vary  with  saturation,  presence 
or  absence  of  brightness  contrast,  distance  of  the  contrasting 
surfaces,  contours. 

E  may,  if  time  allow,  make  up  some  contrast  discs  of  two 
colours,  instead  of  a  colour  and  a  grey,  and  show  them  to  O, 


36  Visual  Sensation 

0  will  describe  exactly  what  he  sees,  and  E  can  work  out  these 
introspective  results  in  the  light  of  the  five  laws  of  contrast. 

(3)  Coloured  shadows  fulfil  these  conditions.  The  principle 
of  the  experiment  is  as  follows.  Two  shadows  of  an  upright 
wand  are  thrown,  side  by  side,  upon  a  screen,  by  means  of  a 
light  and  a  mirror  placed  to  one  side  of  it.  Between  light  and 
wand  a  deeply  coloured  {e.g.j  red)  glass  is  set  up.  The  shadow 
due  to  the  reflected  light,  being  illuminated  by  the  red  rays,  shows 
an  intensive  red  colour:  the  other  shadow,  due  to  the  direct 
light,  shows  an  equally  intensive  blue-green.  The  common 
background  of  both  shadows  is  the  mixture  of  red  and  of  (com- 
paratively) white  light.  The  saturation  of  the  red  shadow  is 
thus  somewhat  diminished;  while  the  contrast  colour  is,  so  to 
say,  all  marginal  contrast  (and  therefore  intensive),  and  gains 
further  by  the  complete  merging  of  the  shadow  contour  in  the 
texture  of  the  screen. 

(4)  See  Helmholtz,  Physiologische  Optik,  2d  ed.,  542,  564; 
Hering,  Zur  Lehre  vom  Lichtsinne,  21  ff.  See  also  Hering, 
Ueber  die  Theorie  des  Simultankontrastes  von  Helmholtz, 
Pfluger's  Archiv,  xl.,  1887,  172  ;  xli.,  1887,  i,  358  ;  xliii.,  1888,  i. 
A  good  account  is  given  by  Ebbinghaus,  Psychologic,  i.,  224  ff. 

(5)  Hering,  as  above. 

Literature.  —  To  the  general  references  given  above  add 
Wundt,  Phys.  Psych.,  i.,  518.  For  work  upon  the  measurement 
of  the  contrast-effect,  see  H.  Ebbinghaus,  Sitzungsber.  d.  Berliner 
Akad.,  xlix.,  1887,  995  ;  C.  Hess  and  H.  Pretori,  Arch.  f.  Ophthal- 
mologic, xl.,  4,  1894,  I  ;  A.  Kirschmann,  Philos.  Stud.,  vi.,  1890, 
417;  A.  Lehmann,  Philos.  Stud.,  iii.,  1886,  497;  H.  Pretori  and 
M.  Sachs,  Pfluger's  Archiv,  Ix.,  1895,  71. 

Instruments. — The  most  beautiful  contrast-effects  with 
which  the  author  is  acquainted  are  given  by  the  Hering  window 
(Rothe,  Mk.  150).  A  large  black  screen,  having  two  oblong 
openings,  is  fixed  over  the  window  (or  let  into  the  wall)  of  the 
dark  room.  The  one  opening  is  filled  with  a  ground  glass ;  the 
other  with  a  red,  orange,  green  or  blue  glass.  The  openings  may 
be  narrowed  and  widened  at  pleasure.  The  two  shadows  of  a 
black  rod  are  thrown  upon  a  screen  of  milk  glass.  It  is  easy  so 
to  arrange  the  openings  that  O,  looking  at  the  screen  and  not  at 


§  '3-    l^fg^tiv4  Afttr-imagts  37 

the  window,  shall  declare  the  contrast-colour  to  be  the  richer, 
more  saturated  and  more  positive  colour  of  the  two. 

On  discs  for  the  demonstration  of  contrast,  see  Helmholtz, 
Phys.  Optik,  544  f. ;  Sanford,  Course,  158;  Aubert,  Phys.  Optik, 
497. 

Hering  (Pfliiger's  Arch.,  xlL,  1887,  358)  describes  an  instru- 
ment (Rothe,  Mk.  28)  for  experiments  upon  mirror  contrast 
(•  Ragona  Scini's  experiment :  *  see  D.  R.  Scinit.  Atti  dell*  Acad. 
Palcrniit,  iil,  1859;  Helmholtz,  Phys.  Optik,  557;  Wundt, 
Phys.  Psych.,  i.,  424;  Sanford,  Course,  155  f.).  Two  other  in- 
struments of  Hering's  for  the  demonstration  of  simultaneous 
contrast  are  sold  by  Rothe  at  Mk.  50  and  Mk.  30  respectively. 

SXPBRQfENT  IV 

{  13.  Viiual  After-images,  (i)  Negative. — This  experiment 
follows  Hering,  whose  Zur  Lehre  vom  Lichtsinne  should  be  read 
(or  lectured  upon)  alongside  of  the  laboratory  work.  The  alter- 
native theory  is  that  of  Fechner:  that  the  phenomena  of  negative 
after-images  are  explicable  in  terms  of  retinal  ia^\%\i^{vcnninderte 
Reiznnpfdnglichkeit\  This  hypothesis  is  adopted  by  Helmholtz, 
in  the  Physiol.  Optik ;  and  the  student  should  be  told  that 
Helmholtz  asserts,  in  his  2d  edition  :  "  I  have  so  far  been  unable 
to  discover  any  phenomenon  that  is  distinctly  irreconcilable  with 
Fechner's  principles  of  explanation."  A  strong  statement,  and 
a  statement  made  after  full  survey  of  "  dieses  ausserst  verwirrte 
Gebiet  der  mannigfaltigsten  Erscheinungen  "  !  Nevertheless, 
the  author  has  become  convinced  by  repeated  experiments  that 
Hering's  account  of  simultaneous  and  successive  contrast,  and 
simultaneous  and  successive  light-induction,  is  very  much  more 
adequate  to  the  phenomena,  taken  as  a  whole,  than  is  the  treat- 
ment in  the  Physiol.  Optik.  James  speaks  truly,  when  he  says 
of  the  book :  "  It  seems  to  me  that  Helmholtz's  genius  moves 
most  securely  when  it  keeps  close  to  particular  facts."  If,  then, 
the  student  is  to  theorise  his  facts  as  he  goes,  if  he  is  not  merely 
to  'observe*  the  after-images  and  have  done  with  them,  the 
Instructor  has,  in  the  author's  judgment,  no  choice  but  to  follow 
Hering. 


38  Visual  Sensation 

General  references  are:  G.  T.  Fechner,  Poggendorff's  Ann.,  xliv.,  1838, 
221,  513;  1.,  1840,  193,  427 ;  Helmholtz,  Phys.  Optik,  2d  ed.,  501  fF.,  537  ff. ; 
H.  Aubert,  Phys.  d.  Netzhaut,  364;  Wundt,  Phys.  Psych.,  4th  ed.,  i.,  512  flf. ; 
C.  Hess,  Arch.  f.  Ophthalmologie,  xxxvi.,  i,  1890,  i  ff . ;  O.  N.  Rood,  Students' 
Textbook  of  Colour,  1881,  235  ff . ;  Hering,  Zur  Lehre  vom  Lichtsinne,  1878; 
PflUger's  Arch.,  xlii.,  1888,  488;  xliii.,  1888,  264,  329;  Ebbinghaus,  Psych., 
i.,  230  ff. 

Preliminary  Exercises. — (i)  At  first  the  room  is  oppres- 
sively black ;  but  in  the  course  of  the  first  two  minutes  it  has 
considerably  lightened,  and  at  the  expiration  of  ten  minutes  or 
a  quarter  of  an  hour  is  a  steady  dull  grey.  The  observer  should 
note  the  various  *  subjective'  phenomena  produced:  flashes  or 
points  of  colour,  more  especially  of  yellowish  grey ;  bright  grey 
clouds  of  varying  form  and  extent,  etc.  —  Aubert,  Physiol,  d. 
Netzhaut,  1865,  27,  39.  (2)  At  first  one  is  dazzled  ;  it  is  painful 
to  keep  the  eyes  open ;  one  blinks,  and  instinctively  seeks  the 
shadowy  places  in  the  light  room.  In  the  course  of  a  minute 
the  eyes  have  become  accustomed  to  the  light.  (3)  The  colour 
is,  at  first,  distinctly  yellow  ;  but  we  soon  become  as  indifferent 
to  this  yellow  as  we  are  to  the  reddishness  of  ordinary  daylight. 
(4)  At  first  the  colour  of  the  glass  is  very  noticeable.  At  the 
end  of  the  five  minutes  there  will  be  hardly  a  trace  of  it  remain- 
ing. —  A  good  variation  of  the  experiment  is  to  have  spectacle- 
frames  (of  the  kind  supplied  with  side-pieces  or  temple-frames) 
filled  with  the  differently  coloured  glasses,  and  to  let  O  wear  the 
spectacles  for  an  hour  or  two.  Complete  adaptation  is  thus 
secured. 

(5)  This  is  Hering's  experiment,  Lichtsinn,  36.  For  the  first 
few  seconds,  the  adjoining  black  and  white  are  enhanced  by  con- 
trast. Very  soon,  however,  the  black  is  covered  by  a  grey  veil, 
which  gradually  lightens,  and  the  white  by  a  grey  shadow,  which 
gradually  darkens.  Both  veil  and  shadow  move  outwards  from 
the  line  of  junction  of  the  two  surfaces,  where  they  also  remain 
most  distinct  throughout  the  experiment.  From  time  to  time, 
owing  to  unsteadiness  of  fixation,  there  appears  along  the  line  of 
junction  a  streak  of  brilliant  white  or  of  deep  black,  the  white 
brighter,  and  the  black  more  intense,  than  the  white  and  black 
of  the  two  surfaces.     The  streaks  belong  to  the  negative  after- 


$  13-   Negative  After-images  39 

images  of  the  surfaces.  They  are  indifferent  to  the  course  of 
the  present  experiment,  except  that  the  black  streak  on  the 
black  surface  and  the  white  on  the  white  surface  serve,  by  con- 
trast, to  emphasise  the  greyness  to  which  the  two  brightnesses 
have  been  brought  by  'simultaneous  light-induction.' 

(6),  (7)  The  result  is  the  same,  mutatis  mutandis,  as  in  (5). 
The  general  law  of  adaptation  is  exemplified  in  each  case. 

(8)  The  general  effect  will  be  that  the  small  disc  *  goes  out,' 
is  merged  in  the  colour  or  grey  of  the  background.  The  partic- 
ular effect  —  the  colour  changes  which  the  disc  passes  through, 
the  quickness  with  which  it  disappears,  the  change  of  the  back- 
ground itself  in  the  neighbourhood  of  the  disc,  etc.  —  varies  with 
the  quality  and  intensity  of  the  disc  and  background,  with  the 
size  of  the  disc,  with  the  foregoing  adaptation  of  the  retina,  etc., 
and  seems,  besides,  to  evince  individual  variations  of  which  no 
explanation  can  at  present  be  offered.*  Ebbinghaus,  Psych.,  i., 
234;  G.  T.  Ladd,  Yale  Studies,  vi.,  1898,  i. 

On  adaptation,  see  Helmholtz,  Phys.  Optik,  508,  555  ff. ;  A.  Fick,  in  Her- 
mann's Handbuch  d.  Physiol.,  iii.,  i,  1879,  222  ff . ;  Aubert,  Physiol.  Optik, 
1876.  483  ff.,  and  op.  cit. ;  T.  Treitel,  Arch.  f.  Ophthalm.,  xxxiii.,  2, 1887,  73 ; 
A.  E.  Fick  and  A.  GUrbcr,  id/d.j  xxxvi.,  2,  1890,  245 ;  A.  E.  Fick,  t'dut.y  xxxviii., 

1,  1892,  118;  xxxviii.,  4,  1892,  300;  Hering, /^/i/.,  xxxvii.,  3,  1891,  i  ;  xxxviii., 

2,  1892,  252;  PflUger's  Arch.,  liv.,  1893,  277;  A.  Charpentier,  La  lumi^re  et 
les  couleurs  au  point  de  \'ue  physiologique,  1888, 154  ff.^  On  the  apparent  dif- 
ference between  the  shift  of  brightness  and  the  shift  of  colour,  see  Hering, 
Lichtsinn.  89. 

Materials.  —  A  skeleton  standing-desk  can  be  made  very 
cheaply,  and  is  of  great  service  in  the  laboratory.  Useful 
dimensions  are:  height,  front,  1.20  m.,  back,  1.35  m. ;  desk 
surface,  55  by  80  cm.  A  bw  edge  should  run  across  the 
front  of  the  desk ;  and  a  flat  shelf  may  be  nailed  to  the  back. 
It  is,  of  course,  better  to  have  the  desk  too  high  than  too 
low. 

*  Cf.,  howerer,  M.  F.  McCIare,  Amer.  Joum.  of  Ptjrcb.,  Jan.,  1901. 

*  The  litenUure  of  this  Section  is  very  voluminous.  The  following  list  of  names 
may  be  of  assistance  to  the  Instructor  for  further  reference :  S.  Bidwell,  H.  P.  lk>s.scha, 
H.  Ebbinghaus,  C.  Hess,  J.  von  Kries,  T.  Lipps,  J.  E.  Lough,  G.  Martius,  A.  Tscher- 
mak.  W.  UbUioff,  H.  Voeste.  W.  Wiztb. 


40  Visual  Sensation 

Experiment  (i).  —  In  this  and  the  following  experiments, 
where  no  specific  directions  as  to  illumination  are  given,  a 
moderate  diffuse  daylight  is  presupposed  :  strong  light  is  to  be 
avoided.  Both  eyes  are  used  for  fixation,  which  should  be  as 
steady  as  possible :  winking,  eye-movement,  etc.,  are  disturbing 
factors. 

O  will  probably  report  incidental  colour-effects,  oscillations  of 
brightness,  temporary  disappearances,  apparent  movements,  etc., 
in  the  after-image.  All  these  changes  should  be  noted  by  E, 
although  they  are  indifferent  to  the  present  experiment.  The 
constant  phenomena  are  {a)  a  darker  disc,  sharply  outlined 
against  the  dark  background  of  the  closed  eyes,  and  surrounded 
{b)  by  a  halo  of  light,  which  is  brightest  where  it  touches  the 
disc,  and  gradually  decreases  in  brightness  towards  the  periphery, 
till  it  is  lost  in  the  darkness  of  the  general  field.  The  halo  is  a 
phenomenon  of  successive  light-induction :  Hering,  Lichtsinn, 
5»  19- 

The  time  of  fixation  must  be  determined  in  preliminary  trials.  It  is  not 
necessary,  but  it  is  useful  as  practice  for  later  work,  that  E  should  have  a  stop- 
watch. He  starts  the  watch  at  a  "  Now  !"  which  is  the  signal  for  O's  fixation  ; 
at  the  end  of  the  20  or  30  sec.  he  gives  a  second  "  Now  ! "  which  is  the  signal 
for  O  to  close  his  eyes ;  and  as  O  reports  the  course  of  the  after-image,  he  jots 
down  the  time  at  which  the  various  phases  appear.  The  time-order  of  the 
phenomena,  as  thus  recorded,  has  no  great  scientific  value :  O  is  unpractised, 
and  the  adaptation  of  his  eyes  will  probably  vary  somewhat  from  experiment 
to  experiment.  But  the  record  will  accurately  represent  the  course  of  the 
image  as  an  individual  phenomenon,  and  (as  was  said  above)  E  will  gain  in 
practice. 

The  following  variation  of  the  experiment  brings  out  very  forcibly  the 
*  physiological '  character  of  the  halo.  Lay  on  the  velvet  two  i  cm.  squares  of 
white  paper,  4  mm.  apart.  Fixate  a  pin-head  or  other  small  object  set  in  the 
middle  of  the  black  strip.  Observe  the  after-image  of  the  squares  as  before. 
O  sees  {a)  two  deep  black  squares,  surrounded  {b)  by  their  halos  ;  but  —  and 
this  is  the  point  —  the  middle  strip,  where  the  two  halos  coincide  or  overlap, 
is  very  much  brighter  than  the  halo  round  the  remaining  three  sides  of  the 
squares. 

Hering,  Lichtsinn,  9;  Sanford,  Course,  161,  exp.  154. 

Experiment  (2).  —  O  will  probably  report  incidental  colour- 
effects,  narrow  and   variously  coloured    edges,    differences    of 


§  13-   Negative  After-images  41 

brightness  at  different  parts  of  the  image,  alternation  of  phase, 
etc.  The  constant  phenomena  are  {a)  the  intense  brightness  of 
the  after-image  strip,  and  (b)  the  absence  (or  very  vague  and 
weak  character)  of  the  dark  halo  which  the  analogy  of  the  fore- 
going experiment  has  suggested.  —  Hering,  Lichtsinn,  11  f. 

Experiment  (3)1  —  A  careful  O  will  see,  in  the  moment  after 
the  removal  of  the  white  disc,  a  positive  (weakly  grey)  after- 
image. This  immediately  makes  way  for  the  negative  effect : 
{a)  a  deeper  black  disc,  surrounded  (h)  by  a  lighter  fringe.  — 
Mering,  Lichtsinn,  98. 

Experiment  (4).  —  O  sees  {a)  a  white  strip,  much  more  intense 
than  the  white  background,  surrounded  (h)  by  a  dirty-white  or 
bright  grey  fringe,  the  *dark  halo.' — Hering,  Lichtsinn,  98  f. 

Experiment  (5).  —  The  after-image  is  a  dark  grey. 

In  the  alternative  experiment,  the  white  strip  grows  slowly  duller  during  fix- 
ation (simultaneous  light  induction).  When  the  black  pieces  are  removed,  the 
strip,  which  is  still  white,  turns  suddenly  to  a  dark  grey.     Hering,  Lichtsinn,  97. 

Experiment  (6). — The  after-image  is  whitish. 

In  the  alternative  experiment,  the  black  strip  is  at  first  very  dark,  and  grows 
gradually  lighter  (simultaneous  light  induction).  When  the  white  pieces  are 
removed,  it  appears  at  once  as  whitish  (successive  light  induction).  Hering, 
Lichtsinn,  97  f. 

Experiment  (7).  —  The  constant  phenomenon  is  a  coloured 
after-image  whose  colour  is  complementary  to  that  of  the 
stimulus  disc. 

The  duration  of  the  after-image  may  be  measured  as  before. 

A  control  experiment  may  be  performed  as  follows.  Use  for  the  coloured 
discs  papers  whose  complementaries  have  been  determined  in  Exp.  I.  Set  up 
the  complementary  discs  upon  the  colour  mixer,  in  front  of  a  grey  screen  of 
the  same  brightness  as  the  grey  background  of  the  wooden  frame.  Cover  the 
mixer  by  another  grey  screen  until  the  after-image  has  developed :  then  sud- 
denly expose  the  complementary  mixture,  and  let  O  compare,  by  a  quick 
glance,  the  tone  of  the  after-image  with  the  tone  of  the  revolving  discs. 
There  will  be  incidental  differences  (the  after-image  will  appear  limpid,  tha 
discs  *  thick  * ;  there  may  be  difference  of  saturation,  etc.) ;  but  if  the  experi- 
ment  has  been  carefully  performed,  the  colour-tones  will  give  a  fair  match. 
On  sources  of  error,  see  Hering,  Lichtsinn,  127  f. 


42  Visual  Sensation 

Experiment  (8).  —  The  result  here  is  precisely  the  same  as  in 
the  case  of  contrast.  The  complementary  colours  of  the  after- 
image mix  with  the  colour  of  the  *  reacting  surface '  according 
to  the  general  laws  of  colour  mixture,  and  the  resulting  image 
is  as  clear  as  is  the  image  on  a  neutral  ground.  —  Sanford,  154, 
exp.  151. 

Question  (i)  Whether  or  not  any  of  the  coloured  discs  of 
exps.  (7)  and  (8)  show  a  contrast-effect  will  depend  upon  cir- 
cumstances :  the  nature  of  the  papers  used,  the  general  illumi- 
nation, the  brightness  of  the  surrounding  grey  surface.  It  may 
be,  e.g.y  that  the  red  disc  gave  a  trace  of  the  contrast  green  when 
it  was  first  fixated.  As  fixation  continued,  the  green  disappeared, 
and  the  grey  in  the  near  neighbourhood  of  the  disc  took  on  a 
reddish  shimmer  (induction).  In  the  after-image,  however,  the 
complementary  green  disc  was  surrounded  by  a  clear  reddish 
halo.  This  proves  both  that  the  contrast-sensation  is  effective, 
and  that  the  contrast-effect  is  enhanced. 

Hering  gives  the  following  as  an  instance  of  the  after-image 
of  a  contrast  sensation.  Cut  two  strips  of  dead-finish  dark-grey 
(imperfectly  black)  paper,  4  cm.  long  and  .5  cm.  wide.  Prepare 
a  background,  half  white  and  half  black,  of  baryta  paper  and 
velvet  laid  side  by  side.  Place  the  strips  upon  the  background, 
the  one  upon  the  white  and  the  other  upon  the  black  surface, 
laying  them  parallel  to  the  line  of  junction  and  at  a  distance  of 
at  least  i  cm.  from  it.  Fixate  a  pin-head,  set  between  the  strips 
in  the  line  of  junction,  for  30  to  60  sec.  At  the  beginning  of 
the  experiment,  the  one  strip  looks  much  brighter  than  the 
other;  as  fixation  is  continued,  this  brightness-difference  gradu- 
ally diminishes. 

After  fixation,  close  the  eyes  and  cover  them  with  the  hands. 
The  bright,  portion  of  the  background  is  dark,  and  the  dark  por- 
tion light,  in  the  after-image.  Moreover,  the  strip  which  at  first 
looked  brighter  is  now  darker,  and  the  strip  which  looked  darker 
is  brighter,  although  the  objective  brightness  of  the  two  strips 
was  the  same.  The  contrast-effect  is,  then,  reflected  in  the 
after-image.  And,  in  general,  the  brightness-difference  of  the 
strips  in  the  image  is  very  considerably  greater  than  their  con- 
trast-difference in  the  stimulus. 


§  13-   Negative  After-images  43 

Notice  that,  when  the  after-image  has  so  far  faded  out  that 
the  brightness-difference  of  the  field  has  disappeared,  the  differ- 
ence between  the  strip-images  may  still  persist,  the  one  being 
brighter  and  the  other  darker  than  the  uniform  background.  — 
Lichtsinn,  24  f.,  27. 

(2)  This  question  has  been  answered  by  the  foregoing  experi- 
ments, and  also  by  the  alternative  experiments  (5) and  (6)  of  the 
text.  A  pretty  illustration  (Ebbinghaus)is  as  follows.  Lay  two 
moderately  large  sheets  of  saturated  green  paper  upon  a  grey 
ground,  leaving  a  horizontal  strip  of  .5  cm.  width  between  them. 
O  fixates  a  mark  in  the  centre  of  the  grey  strip.  After  30  sec. 
he  projects  the  after-image  upon  an  irregular  surface,  e.g.y  upon 
the  nearest  window-frame.  The  after-image  is  almost  invariably 
described  as  a  *  green  strip.*  The  red  after-image  of  the  field  is 
lost  in  the  irregularities  of  the  reacting  surface,  while  the  green 
*  heaped  up  *  over  the  grey  strip  in  stimulus  and  after-image  is 
sufficiently  strong  to  draw  the  attention  exclusively  to  itself.  — 
Tsych.,  i.,  239. 

(3)  No  extended  series  of  experiments  can  be  made  that  does 
not  furnish  evidence  of  the  periodicity  of  the  after-image.  It 
comes  and  goes ;  the  relative  brightness  of  its  parts  varies  from 
appearance  to  appearance ;  some  parts  persist  unchanged,  while 
others  merge  in  the  general  background.  Many  of  the  changes 
are,  doubtless,  due  to  movement  of  the  eyes,  unnoticed  changes 
in  the  illumination  of  the  reacting  surface,  wandering  of  the 
attention  :  Helmholtz  has  pointed  out  that  even  a  change  of 
breathing  may  affect  the  after-image.  But  over  and  above  these 
accidental  influences,  there  is  an  uniformity  in  the  phenomena 
which  points  distinctly  to  a  periodicity  grounded  in  the  nature 
of  the  after-image  itself. 

On  the  positive  side,  see  Hering,  Lichtsinn,  44 ;  Aubert,  Phys.  d.  Netzhaut, 
373  ff. ;  Phys.  Optik,  514.  On  the  negative,  Fechner,  Poggendorff's  Annalen, 
xliv.,  1838,  525;  Helmholtz,  Phys.  Optik,  510. 

Experiment  (9).  —  Although  this  experiment  is  quantitative 
in  character,  it  affords  an  excellent  means  of  studying  the  quali- 
tative course  of  the  image,  and  so  has  its  justification  in  the  pres- 


44  Visual  Sensation 

ent  volume.  The  apparatus  is  somewhat  cumbrous :  but  it  is 
not  expensive,  and  will  serve  a  number  of  purposes  in  later 
laboratory  work. 


The  words  *  relative '  and  '  absolute '  in  the  formulation  of  the  law  may  need 
explanation.  The  law  says  that  the  intensity  and  duration  of  the  image  depend 
(a)  upon  the  intensity  of  the  stimulus,  (d)  upon  the  intensity  of  the  stimulus 
as  compared  with  the  intensity  of  its  surroundings,  (c)  upon  the  duration  of 
the  stimulus,  (ii)  upon  the  intensity  of  the  light-surface  upon  which  the  image 
is  projected,  and  (e)  upon  the  intensity  of  this  reacting  light  as  compared  with 

the  intensity  of  the  primary  stimulus.  All  five 
factors  may  be  suitably  varied  with  the  described 
apparatus. 

The  apparatus  itself  may  be  modified  in  a 
great  variety  of  ways.  On  the  side  of  cheap- 
ness, we  may  substitute  oil-lamps  for  the  burn- 
ers, hand-screens  for  the  gas-cocks,  and  coloured 
glasses  for  the  gelatines.  On  the  other  side, 
we  may  have  an  Aubert  diaphragm  (Phys.  Op- 
tik,  547  ;  Phys.  d.  Netzhaut,  44),  in  place  of  the 
circular  opening  in  the  screen ;  and  may  use, 
instead  of  the  ordinary  gas-cocks,  the  cocks 
supplied  with  a  bar-handle  and  graduated  arc. 
The  limits  through  which  the  handle  is  to  be 
turned  in  the  manipulations  may  be  marked  by 
lumps  of  wax  squeezed  down  upon  the  arcs,  or 
pieces  of  electric  tape  wrapped  round  them. 
If  ordinary  cocks  are  employed,  the  limits 
may  be  set  by  wire  nails  driven  into  the  table. 
A  blackened  observation  tube  may  be  useful. 
It  may  be  mentioned,  as  a  point  of  method,  that  some  £'s  have  great  diffi- 
culty in  taking  notes  and  counting  the  metronome  strokes  at  the  same  time. 
If  the  difficulty  is  not  overcome  by  practice,  the  counting  may  be  done  by  O. 
As  the  image  changes,  O  calls  out  catch-words  which  Eputs  down ;  when  the 
image  has  disappeared,  E  reads  these  words  to  O,  who  amplifies  his  introspec- 
tions and  gives  the  times  at  which  the  changes  occurred. 

On  the  use  of  coloured  gelatines,  see  A.  Kirschmann,  Philos.  Studien,  vi., 
1891,  543.  For  another  apparatus,  see  S.  I.  Franz,  Psych.  Rev.  Monograph 
Suppl.  12,  1899 ;  for  apparatus  on  the  lines  of  that  here  recommended,  see  E. 
W.  Scripture,  Philos.  Studien,  vii.,  1892,  53  ;  E.  B.  Titchener,  t'did.y  viii.,  1893, 
247;  W.  B.  Pillsbury,  Amer.  Journ.  of  Psych.,  viii.,  1896-7,  343. 


Fig.  3.  —  Aubert  diaphragm. 


The  following  are  typical  results.     The  individual  character 
of  such  a  series  need  not  be  emphasised. 


5  13-   AV^//iJr  AfUr-imagts  45 

Stimulus :  red.    Left  eye.    Reacting  turfiux  moderately  bright.    3  min. 
intervals. 


10  « 

18     ^ 

IS   « 

23    ^ 

30    " 

25  « 

II 

5  sec     12  sec.     Green  disc,  with  violet  (at  first  merely  bright)  halo :  7  sec. 
Green.    Greenish  grey. 
Red  centre  (3  sec.),  green  disc,  red  halo:  7  sec     Green. 

Daric  greenish  grey. 
Violet  centre  (3  sec.),  green  disc,  reddish  violet  (later 

bright)  halo:  10  sec.    Green.    Greenish  grey. 
Bright  violet  centre  (3  sec.),  green  dbc,  violet  (3  sec. : 
later  bright  green)  halo.     Dark  green,  with  bright  green 
halo. 
25    "       30    **        Violet  disc.     Green  disc,  with  violet-red  (9  sec. :  later  bright 
green)  halo.     Dark  green. 

Where  a  positive  image  precedes  the  negative,  there  is  usually  an  intm-pn- 
ing  period,  perhaps  of  2  or  3  sec.,  during  which  no  image  is  seen. 

Question  (4)  See,  besides  Helmholtz  and  Hering,  opp.  citt., 
Ebbinghaus,  Psychologie,  i.,  248  f.,  251  f. 
(5)   Ebbinghaus,  Psychologie,  i.,  235,  258. 

Further  Experiments.  —  The  following  experiments  present 
points  of  interest. 

(i.)  Obscn^ation  of  the  Negative  After-image  with  Persistence 
of  the  Stimulus.  —  Arrange  the  apparatus  as  for  exp.  (9),  leaving 
aside  the  second  dark-box  and  burner.  Expose  a  stimulus  —  eg.^ 
red  —  for  the  usual  time.  Then  simply  turn  down  the  stimulus- 
burner  to  a  low  intensity  of  illumination,  so  that  the  red,  as  seen 
by  the  normal  eye,  would  appear  as  a  dark  reddish-brown.  The 
originally  red  disc  is  transformed,  for  (7*s  eyes,  into  a  comple- 
mentary green. 

The  experiment  may  be  performed  more  simply  as  follows. 
Set  up,  in  moderate  diffuse  daylight,  a  small  red  disc  on  a  yellow 
ground.  O  fixates  the  centre  of  the  red  disc  for  the  usual  time. 
Then  a  curtain  is  suddenly  drawn  across  the  illuminating  window, 
so  that  the  general  brightness  of  the  stimulus  is  considerably 
decreased.  O  sees  a  g^een  disc  on  a  blue  ground.  —  Ebbinghaus, 
238;  Sanford,  Course,  113,  cxp.  124;  C.  L.  Franklin,  Mind, 
N.  S.,  ii.,  1893,  485. 

(ii.)  Change  in  the  Apparent  Magnitude  of  the  After-image 
with  Distance  of  the  Reacting  Surface.  —  Secure  a  strong  nega- 


46  Vistial  Settsation 

tive  after-image  as  in  exp.  (7).  Project  it  successively  upon  a 
series  of  grey  backgrounds  set  up  at  different  distances  from 
the  eyes.  Note  that  the  after-image  enlarges  as  the  distance 
increases.  —  Aubert,  Phys.  d.  Netzhaut,  367. 

Project  the  after-image  also  upon  curved  or  bent  backgrounds, 
and  note  that  it  seems  itself  to  curve  or  bend  correspondingly : 
Sanf ord,  Course,  1 1 2,  exp.  1 24. 

(iii.)  Movement  of  the  After-image  with  Movement  of  the  Eye, 
—  Get  a  strong  negative  after-image  with  both  eyes,  and  note 
that  it  moves  to  all  parts  of  the  room  as  the  fixation-point 
changes.  When  the  eyes  are  steady  (when,  e.g.^  O  fixates  a 
pencil  point)  the  after-image  remains  stationary. 

Secure  a  monocular  after-image  a  little  to  one  side  of  the 
fovea :  i.e.^  fixate  monocularly  the  central  pin-hole  in  the  front 
screen  of  exp.  (7),  and  pin  a  coloured  disc  a  few  cm,  to  right  or 
left  of  it.  Open  both  eyes,  and  project  the  after-image  to  various 
parts  of  the  room.  Note  the  recurrence  of  the  effort  to  fixate  the 
image,  and  its  entire  fruitlessness. —  Helmholtz,  507;  Aubert,  367. 

Note  the  effect  upon  the  after-image  of  unsteady  fixation,  of 
incomplete  adaptation,  of  winking  and  eye-movement  during 
its  course,  of  winking  immediately  after  its  disappearance.  — 
Ebbinghaus,  240  f. 

(2)  Positive  After-images. — The  phenomena  of  the  positive 
after-image  are  not  yet  fully  understood,  and  the  recorded  obser- 
vations are  not  all  in  agreement.  Neither  of  the  two  dominant 
theories  of  visual  sensation  has  offered  any  satisfactory  principle 
of  explanation.  The  current  view,  that  the  positive  after-image 
represents  a  simple  persistence  of  stimulation,  is  certainly 
inadequate. 

References:  Aubert,  Phys.  d.  Netzhaut,  347;  Helmholtz,  Phys.  Optik, 
480,  503;  C.  Hess,  Pfliiger's  Arch.,  xlix.,  1891,  190;  S.  Bidwell,  Proc.  Roy. 
Soc,  Ixvi.,  no.  337,  1894,  132;  A.  Charpentier,  Arch,  de  physiol.,  sdr.  5,  iv., 
1892,  541,  629. 

Experiment  (10). — With  some  practice,  the  observer  is  able 
to  see  a  positive  after-image,  true  in  brightness  and  colour  to 
the  original.  The  details  of  the  scene  —  the  leaves  of  the 
shrubs,  the  string  and  tassel  of  the  window-shade,  etc.  —  come 
out  with  surprising  clearness. 


§  13.   Positive  After4wuigfs  47 

A  pretty  variation  of  the  experiment  may  be  made  with  arti- 
ficial light,  as  follows.  Seat  yourself  at  a  table  which  is  covered 
with  variously  coloured  objects  and  lighted  by  a  good  lamp. 
Proceed  as  in  the  previous  experiment  with  the  window.  When 
the  field  is  darkened,  for  the  projection  of  the  after-image,  the 
hands  seem  for  a  moment  to  be  actually  transparent,  so  vivid  is 
the  appearance  of  the  coloured  images.  Many  details  may  be 
observed  in  the  after-image  which  escaped  observation  during 
the  rapid  glance  at  the  real  objects. 

Note  that  the  darker  surfaces  disappear  first,  without  any 
considerable  change  of  colour.  The  brighter  surfaces  remain 
longest,  and  undergo  a  regular  series  of  colour  changes.  — 
Helmholtz,  Phys.  Optik,  504. 

Experiment  (ii).  —  Helmholtz,  as  before.  The  experiment 
may  be  varied  by  observing  the  light  through  variously  coloured 
glasses  or  gelatine-mixtures. 

Experiment  (12). — The  irregularly  shaped  after-image  is 
positive  upon  the  dark  field,  and  negative  upon  the  bright  field. 

The  look  at  the  sun  must  be  extremely  short.  After-image 
experiments  are  always  trying  to  the  eyes,  and  the  stimulation 
received  from  the  solar  disc  is,  of  course,  extraordinarily  intensive. 
Helmholtz  advises  that  only  a  few  after-image  experiments  be 
made  on  any  given  day,  and  that  the  experiments  be  discontinued  if 
the  observer  complains  of  pain  in  the  head  or  eyes,  or  experiences 
such  pain  when  looking  at  bright  or  vividly  coloured  surfaces,  or 
even  begins  to  have  unusually  persistent  and  vivid  after-images. 
Phys.  Optik,  502  f.;  cf.  Aubert,  Phys.  d.  Netzhaut,  371. 

Experiment  (13).  —  The  after-image  is  positive  on  the  dark, 
and  negative  on  the  white  field.  In  exp.  (12),  the  stimulus  is 
very  brief,  but  of  very  high  intensity ;  in  exp.  (13)  the  stimulus 
is  not  overbright,  but  is  continued  for  a  longer  time  than  suffices 
for  the  arousal  of  a  positive  image.  The  time  of  stimulation  in 
experiments  of  the  type  of  (10)  and  (11)  is  ordinarily  given  as 
0.3  sec.  Helmholtz,  503. 

Experiment  (14).  —  The  moving  red  point  is  continued  as  a 
red  streak,  due  to  the  slowness  with  which  the  primary  sensa- 
tion rings  off.  The  red  streak  ends  as  a  grey,  or  greyish  red, 
which  is  continued,  in  its  turn,  as  a  blue-g^een  streak,  showing 


48  Visual  Sensation 

bright  against  the  dark  background  (positive  and  complemen- 
tary after-image).  Some  observers  report  a  blank  interval  be- 
tween the  red  and  the  blue-green ;  the  red  then  ends  abruptly, 
without  becoming  grey.  After  this  blue-green  streak  would 
come,  if  the  full  series  of  phenomena  were  represented,  the  red 
positive  after-image  of  the  point ;  and  after  that,  again,  the 
(dark)  blue-green  negative  image.  Ebbinghaus,  Psych.,  i.,  244  ; 
Sanford,  Course,  114,  exp.  125;  first  described  by  J.  Purkinje, 
Beobachtungen  u.  Versuche  z.  Phys.  d.  Sinne,  ii.,  1825,  no. 

Experiment  (15). — This  experiment  shows,  in  a  striking 
way,  the  effects  of  practice.  The  report  of  a  wholly  unpractised 
observer  is  a  mere  chaos.  With  attention,  the  uniformity  of  the 
phenomena  soon  becomes  apparent ;  and  presently  the  observers 
who  at  first  gave  radically  different  accounts  of  the  after-image 
will  reach  agreement  upon  all  essential  points. 

With  an  unclouded  sky,  or  a  sky  thinly  covered  with  clouds 
and  presenting  an  even  white  surface,  the  flight  of  colours  is  as 
follows : 

{a)  A  momentary  positive  and  same-coloured  image. 

(^)  Interval  of  5  or  6  sec. 

{c)  Positive  image,  fluctuating  in  colour ;  sometimes  with  patches  of  red 
and  green.  After  i  or  2  sec,  the  image  settles  down  to  a  sky  d/ue,  the  verti- 
cal bar  remaining  dark. 

(^)  The  blue  passes,  with  or  without  interruption,  into  a  green.  The 
green  is  at  first  very  vivid ;  it  disappears  and  reappears  five  or  six  times,  grow- 
ing gradually  paler ;  at  last  it  is  almost  whitish.  —  These  initial  changes  show 
a  good  deal  of  individual  variation.     Some  (9's  now  see 

(^)  A  yellow  image.  This  (or  the  whitish  green  preceding)  is  regularly 
followed  by 

(/■)  A  deep  red  image.  The  black  bar  becomes  luminous  and  slightly 
greenish,  the  light  appearing  first  as  a  crack  in  its  length.  This  is  the  stage 
of  transition  from  the  positive  to  the  negative  image.  The  red  undergoes 
several  fluctuations.     Then  follows 

(^)  A  deep  blue  image,  with  yellowish  bright  bar,  more  lasting  than  any 
of  the  preceding  phases.  The  blue  darkens,  and  the  image  gradually  disap- 
pears, with  or  without  passing  into 

{h)  A  dark  ^reen  image.  —  Helmholtz,  Phys.  Optik,  524 ;  M.  F.  Wash- 
bum,  Mind,  N.  S.,  viii.,  1899,  25,  and  unpublished  experiments.  Note  the 
periodicity  of  stages  c  to  A: 

B  — G  — Y  — R  — B  — G 


§  13.   Positivt  A/Ur-imagiS  49 

Question  (6)  If  the  illumination  is  much  diminished,  the 
sky  dull  and  heavily  clouded,  stages  {c\  (</)  and  (<•)  are  lacking. 
The  first  image  is  a  reddish  white,  with  dark  bar.  The  red 
gradually  deepens,  and  the  negative  image  appears,  followed 
after  several  fluctuations  by  a  dark  blue  negative  image. 

(7)  After  a  certain  limit  has  been  passed,  the  duration  of  the 
stimulus  does  not  affect  the  course  of  the  image.  Try  with 
10  and  15  sec  exposures.  Helmholtz,  524. — With  very  brief 
stimulation,  the  sequence  is:  {a)  white,  passing  quickly  through 
(b)  greenish  blue  to  (c)  deep  blue,  and  then  into  {d )  violet  or 
rose.  Then  follows  (e)  a  dull  orange,  during  which  the  image 
may  change  from  positive  to  negative,  and  become  a  dirty  yel- 
low-green.    Helmholtz,  521  f. 

(8)  The  usual  explanation  (Plateau,  Fechner,  Helmholtz, 
Wundt)  is  that  "the  after-effect  of  the  excitation  is  dependent 
upon  the  wave-length  of  the  light."  The  white  light  of  the 
window  is  broken  up  into  its  physical  constituents,  and  the  tem- 
poral course  of  the  red,  green  and  violet  excitations  in  the  retina 
(or  the  visual  apparatus)  shows  characteristic  differences.  See, 
e.g.,  Helmholtz,  Phys.  Optik,  522;  Wundt,  Phys.  Psych.,  i.,  516. 
Hering  believes  that  there  is  always  some  colour,  however  weak, 
in  the  original  stimulus:  Lichtsinn,  85,  1 12,  125.  The  perio- 
dicity which  appears  in  exp.  (15)  and  in  the  answer  to  Question 
(7)  is  strongly  suggestive  of  Hering's  general  theory  of  colour 
vision. 

(3)  Binocular  After-images. — The  question  of  a  functional 
interconnection  of  the  two  retinas  (or  of  the  two  halves  of  the 
visual  apparatus)  is  as  old  as  Newton,  and  has  been  very  vari- 
ously answered.  The  latest  writer  on  the  subject,  Franz  (Psych. 
Rev.  Mon.  Suppl.  12,  1899,  44),  takes  a  negative  standpoint. 
The  author,  however,  regards  Franz*  criticism  as  inconclusive 
('suggestion/  e,g.t  may  work  as  well  against  as  for  the  binocular 
image);  and  finds  in  the  assumption  of  such  an  interconnection 
the  only  means  of  explaining  the  observed  facts. 

Experiment  (16).  —  As  soon  as  the  left  eye  is  opened,  C^sees 
upon  the  white  ground  a  faint  reddish  image,  fairly  clear  in  out- 
line. After  I  or  2  sec,  the  middle  portion  of  the  ground  sud- 
denly darkens,  and  (after  about  i  sec)  there  appears  upon  it  a 


50  Visual  Sensation 

complementary  (blue-green)  after-image.  Shade  and  image 
remain  for  some  little  time.  Then  the  ground  clears  again,  and, 
under  favourable  conditions  (no  eye-movement,  complete  adap- 
tation, moderate  illumination),  the  original  reddish  image  reap- 
pears as  a  shapeless  patch.  Very  soon  the  darkening  of  the 
field  and  the  complementary  image  recur.  —  The  author  has 
been  able  to  see  the  red  image  three  times,  and  the  complemen- 
tary image  on  the  dark  ground  five  times,  in  a  single  experiment. 
The  darkening  is  due  to  the  superposition  of  the  field  of  the 
closed  right  eye  upon  that  of  the  left.  The  complementary 
image  belongs  to  the  right  eye :  it  appears  only  upon  the  dark- 
ened field.  The  red  image  is  the  effect  of  the  indirect  stimula- 
tion of  the  left  eye  (or  left  half  of  the  visual  apparatus). 

S.  I.  Franz,  ^/.  cit.;  Sanford,  Course,  ii6,  exp.  127;  175,  exp.  169;  Titch- 
cner,  Philos.  Studien,  viii.,  1893,  244  ff.  The  author  regards  the  results  of 
the  a-method  in  this  paper  as  reliable ;  the  ^-method  he  now  considers 
untrustworthy. 

The  following  variation  of  the  experiment  (Franz)  is  instructive.  Fixate 
the  ink  dot  on  the  white  surface,  and  lay  a  small  disc  of  bright  orange  paper 
in  such  a  position  that  it  is  altogether  lost  in  the  blind-spot  area  of  the  right 
eye.  Secure  the  head  firmly  by  head-rest  and  mouth-board  (p.  245).  After 
adaptation,  open  the  left  eye,  and  fixate  the  ink  dot  for  5  sec.  Then  close 
the  left,  and  open  the  right  eye.  No  image  appears,  until  the  field  has  dark- 
ened (superposition  of  left  field),  when  a  dim  blue  disc  is  seen  in  indirect 
vision.  In  other  words,  the  left-eye  image  is  seen,  but  there  is  no  right-eye 
(transferred)  image.  This  result  points  toward  a  direct  functional  intercon- 
nection of  the  retinas :  for,  if  the  ^  binocular '  image  were  merely  a  matter  of 
central  excitation,  there  is  no  reason  why  it  should  not  be  seen  within  the 
blind  area  of  the  right  eye. 

The  experiment  must  be  checked  by  experiments  of  the  type  of  (16).  A 
valid  result  presupposes  a  high  degree  of  practice  on  the  part  of  O. 

Instruments.  —  Wundt's  after-image  apparatus  (Phys.  Psych., 
i.,  543  ;  Zimmermann,  Mk.  60)  is  excellent  for  demonstration 
purposes.  The  instrument  recommended  for  exp.  (7)  is  a  simple 
form  of  Hering's  apparatus  (Rothe,  Mk.  45). 


CHAPTER   II 
Auditory  Sensation 

§  14.  Auditory  Sensation.  —  On  simple  tone  and  simple  noise 
see: 

A.  Barth,  Zur  Lehre  von  den  Tonen  und  Gerauschen.  Zeits.  f.  Ohren- 
heilkunde,  x\ni.,  1887,  81. 

H.  Ebbinghaus,  Grundziige  d.  Psychologic,  i.,  1897,  276. 

H.  von  Helmholtz,  Sensations  of  Tone,  1895,  ^y  ^3*  '45>  'S^* 

A.  Hofler,  Psychologic,  1897,  95. 

E.  C.  Sanford,  Course,  exps.  63,  64,  65,  66,  69. 

C  Stumpf,  Ton  psychologic,  i.,  1883,  178,  189;  ii.,  1890,  257,  511. 

W.  Wundt,  Grundziige  d.  physiol.  Psychologic,  i.,  1893,  443. 

C/.  also  Foster,  Textbook  of  Physiol.,  iv.,  1891,  1361 ;  Stout,  Manual  of 
Psych.,  171;  Titchener,  Outline,  57;  KUlpe,  Outlines,  102;  V.  Hensen,  in 
Hermann*s  Handbuch  d.  Physiol.,  iii.,  2,  1880,  3. 

Sensations  of  tone  are,  perhaps,  of  all  sensations,  those  which 
the  average  student  approaches  with  the  greatest  diffidence  and 
the  least  interest.  It  has  often  been  said  that  the  Anglo-Saxon 
peoples  are  unmusical ;  and,  although  general  statements  of 
this  kind  should  not  be  lightly  accepted,  there  can,  at  least,  ,be 
no  doubt  that  the  world  of  tones  receives  but  a  minimal  atten- 
tion as  compared  with  the  world  of  colours.  We  are  always 
thinking  about  *  how  we  look  * ;  it  occurs,  apparently,  to  very 
few  to  think  how  they  sound.  But,  over  and  above  this  lack  of 
practice  in  the  apprehension  and  discrimination  of  tones,  there 
is  a  wide-spread  belief  that  tone  psychology  presupposes  musical 
gifts  and  musical  training.  "There  is  a  close  relation,"  says 
Kiilpe,  "between  tonal  fusion  and  the  tonal  connections  whose 
aesthetic  effect  is  displayed  in  music.  We  are  thus  in  the 
fortunate  position  of  having  the  results  of  centuries  of  artistic 
practice  to  compare  with  the  outcome  of  psychological  experi- 
mentation."    Now  while  this  is  true,  —  while  an  investigation 

5» 


52  Auditory  Sensation 

of  the  complex  formations,  melody,  consonance  and  dissonance, 
etc.,  does  demand  musical  knowledge,  and  would  not  be  under- 
taken by  students  who  did  not  possess  such  knowledge,  —  still 
there  is  no  need  of  musical  ability  for  the  fundamental  experi- 
ments in  tonal  sensation.  Even  in  such  a  matter  as  the  analysis 
of  clangs  into  their  partials,  "a  musically  trained  ear  will  not 
necessarily  hear  upper  partial  tones  with  greater  ease  and  cer- 
tainty than  an  untrained  ear.  Success  depends  rather  upon  a 
peculiar  power  of  mental  abstraction  or  a  peculiar  mastery  over 
attention,  than  upon  musical  training  "  (Helmholtz).  The  stu- 
dent should,  therefore,  be  encouraged  to  believe  that  he  can 
carry  the  following  experiments  to  a  successful  issue,  even  if  he 
has  had  no  musical  training.  The  experiments  themselves  may 
arouse  an  interest  in  music,  which  should  then  be  carefully  fos- 
tered by  the  Instructor.  The  psychologist  who  can  think  and 
imagine  and  remember  in  tones,  as  well  as  in  colours  and  in 
kinaesthetic  images,  has  a  very  great  advantage. 

The  experiments  have  been  so  chosen  and  arranged  as  to 
familiarise  the  student,  in  order,  with  the  essentials  of  qualita- 
tive work  upon  tone  sensation.  Nevertheless,  it  will  be  advisa- 
ble to  preface  the  laboratory  exercises  by  a  general  lecture,  in 
which  especial  attention  is  paid  to  the  correlation  of  sound  sen- 
sations with  sound  stimuli :  the  main  points  may  be  taken  from 
Helmholtz,  Pt.  i.  The  author  has  found  it  well  to  make  clear, 
at  the  outset,  such  matters  as  the  variability  of  pitch-numbers, 
the  difference  between  just  and  equal  temperament,  etc.  Wher- 
ever it  is  possible,  the  tones  and  intervals  referred  to  in  lecture 
should  be  played  upon  some  instrument.  For  purposes  of 
demonstration,  the  Ellis  Harmonical  (Helmholtz,  p.  17;  made 
by  Moore  and  Moore,  104  Bishopsgate  Street,  London,  for 
about  £i\d)  has  a  value  that  can  hardly  be  overestimated. 

Preliminary  Exercises. — (i)  This  experiment  can  be  per- 
formed more  elegantly  with  a  Savart  Wheel,  a  toothed  wheel  of 
wood  or  metal,  rotating  on  a  horizontal  axis,  and  striking  as  it 
rotates  against  a  piece  of  cardboard.  With  variation  of  speed 
of  rotation  the  struck  card  gives  a  series  of  noises,  a  low  tone 
(clang),  and  a  high  tone  (clang). 

(3)   The  determination  of  the  predominant  tone  can  be  tested 


§  14-   Auditory  Sensation  53 

by  releasing  the  loud  pedal,  carefully  pressing  down  the  key 
whose  tone  has  been  selected,  and  repeating  the  stimulus.  If 
the  determination  was  correct,  the  free  strings  will  ring  out 
loudly  in  the  resonance<hamber  of  the  instrument. 

(4)  The  introspective  characterisation  is  extremely  difficult, 
since  the  simple  tone  and  the  simple  noise  are  ultimate  sense-pro- 
cesses, and  ultimates  are  never  susceptible  of  exact  definition. 
One  cannot,  therefore,  expect  the  student  to  give  anything  but 
a  figurative  account.  Thus  he  may  say  that  the  tone  is  undis- 
turbed, uniform,  clear,  smooth,  restful,  mild,  suggestive  of  un- 
broken continuance,  whereas  the  noise  is  abrupt,  rough,  harsh, 
startling,  unsatisfying.*  Some  of  these  words  denote  the  nature 
of  the  sound  itself,  others  indicate  its  affective  value. 

There  can  be  no  doubt  that  noises  differ  in  quality  or  pitch. 
Compare  the  rattle  of  a  light  cart  and  the  rumble  of  a  heavy 
vragon  over  a  paved  road  ;  the  crack  of  a  pistol  and  the  boom  of 
a  cannon  ;  the  crash  of  near  and  the  growl  of  remote  thunder; 
the  tinkle  of  a  mountain  stream  and  the  pounding  of  a  cataract.  — 

These  exercises  may  be  extended  as  far  as  the  Instructor 
deems  advisable.  Thus  the  student  may  be  set  to  work  to 
classify  noises,  bringing  together  all  those  that  belong  to  the 
same  group,  and  arranging  them  in  the  order  of  intensity  and  of 
pitch,  —  noting  differences  of  duration,  of  frequency,  etc.,  in  the 
complex  noises.  Or  he  may  determine  the  tonal  element  in  the 
howling  of  the  wind,  the  buzz  of  a  swarm  of  insects,  the  sound 
of  conversation  in  a  crowded  room,  etc. 

Questions.  —  These  need  not  all  be  answered  at  the  outset, 
but  may  be  given  as  exercises  at  various  stages  of  the  work. 

'An  exercise  of  this  kind  should  be  approached  methodically  and  systematically. 
Tone  and  noise  have,  both  alike,  three  attributes  or  properties :  duration,  intensity, 
quality.    The  enquiry  should  begin  with  the  relative  attributes,  as  follows  : 

I.  (1)  Do  tones  and  noises  evince  a  constant  diflference  of  duration? 
(3)  Do  they  evince  a  constant  difference  of  intensity? 

When  these  questions  have  been  answered,  the  student  passes  to  the  absolute  attri« 
bote,  qnality : 

II.  Are  there  qualitative  or  modal  differences,  in  other  sense-departments,  analo- 
fooB  to  the  difference  between  tone  and  noise  in  audition  ? 

We  then  get  the  antitheses  clear,  opaque,  etc.  —  It  follows  that  Tolstoi's  fable  of 
''The  Blind  Man  and  the  Milk '  does  not  do  full  justice  to  psychological  method. 


54  Auditory  Sensation 

(i)  See  especially  Helmholtz,  23  £.,  56  f. ;  Ellis  in  Helmholtz, 
24  £.,  57.  The  author  prefers  the  term  *  clang'  to  *  compound 
tone,'  and  'clang-tint'  to  'timbre'  or  'quality.'  The  latter 
word  is,  indeed,  quite  inadmissible:  the  'quality'  of  tone,  in 
psychophysical  language,  is  its  pitch. 

(2)  Helmholtz,  310  if.;  Ellis  in  Helmholtz,  430  ff.,  466  ff., 
483  ff. 

(3)  Stumpf  (Tonpsych.,  ii.,  196  f.)  denies  the  intrinsic  like- 
ness of  the  fundamental  and  its  octave,  and  offers  as  test  ex- 
periments the  performance  of  a  quick  chromatic  run,  or  of  a 
glissando,  upon  the  piano ;  the  continuous  movement  of  the 
finger  down  a  bowed  string ;  the  continuous  change  of  the  tone 
of  a  stopped  pipe.  Ebbinghaus,  who  holds  the  opposite  view 
(Psych.,  i.,  279),  objects  that  in  these  experiments  the  attention 
is  so  strongly  drawn  to  the  pitch-difference  of  the  tones  that  the 
disappearance  (Zuriicktreten)  of  similarities  is  not  surprising. 
But  it  is  just  because  the  pitch-differences  are  clearly  brought 
out  that  the  experiments  are  valuable  :  the  objection  begs  the 
question.  Cf.  Stumpf's  discussion  in  Beitr.  z.  Akustik  u.  Musik- 
wiss.  i.,  1898,  45  ff. 

The  term  'likeness'  may  have  various  meanings,  (i)  Like- 
ness may  be  regarded  as  an  original  and  ultimate  attribute  or 
aspect,  or  as  an  'imminent  relation,'  of  simple  qualities.  Red 
and  orange  come  to  us  with  a  mark  of  'likeness '  upon  them,  — 
more  accurately,  within  them  ;  no  further  analysis  is  possible. 
(2)  Likeness  may  mean  'likeness  of  feeling-effect,'  as  in  the 
former  case  it  means  likeness  of  direct  sense-effect.  Green  and 
blue  would  then  be  like,  because  they  put  us  in  like  moods,  of 
restfulness  or  qiiiet.  (3)  Likeness  may  mean  nearness  in  the 
scale  of  sensible  discrimination.  A  given  blue  would  be  like 
the  just  noticeably  different  blue,  because  (or  in  the  sense  that) 
it  is  not  easily  distinguishable  from  this  other  blue.  (4)  Like- 
ness may  mean  partial  identity  ('  identity,'  in  psychology,  being 
equivalent  to  'indistinguishableness ');  two  colour  impressions 
would  be  like  which  were  identical,  e.g.y  in  all  their  attributes 
except  duration,  or  in  all  except  duration  and  extent,  etc.  (5) 
Two  simple  contents  may  be  like,  in  the  sense  that  they  stand 
in  the  same  relation  to  a  third  (simple  or  complex)  process. 


f  «5    Bmis  55 

Thus,  red  and  orange  arc  alike  for  spatial  reasons :  they  both 
belong  to  the  long-wave  end  of  the  spectrum  ;  red  and  blue  are 
alike,  because  they  are  both  'colours,*  etc.  —  It  is  plain  that  the 
term  *  likeness  *  is  very  ambiguous,  and  that  it  is  fatally  easy  to 
slip  from  some  one  of  its  meanings  to  some  other,  even  when  we 
are  discussing  the  same  process  or  set  of  processes.  The  ques- 
tion of  an  ultimate,  irreducible  likeness  has  been  keenly  dis- 
puted. Sec  Kiilpe,  Outlines,  192 ;  James,  Psych.,  i.,  490,  532 ; 
Mind.  N.  S.,  ii..  1893,  208;  F.  H.  Bradley,  Mind,  N.  S.,  ii.,  83; 
K.  Deffner,  Zeits.  f.  Psych.,  xviii.,  1898,  218;  Stumpf.  Tonpsych., 
L,  97.  >  1 1  ^-t  115.  42s  ;  "•.  272 ;  etc. 

The  diagram  referred  to  is  Drobisch's  spiral.  See  Ebbing- 
haus,  280;  A.  Hofler,  Psychol,  1897,  99;  W.  Volkmann  von 
Volkmar,  Lehrb.  d.  Psych.,  i.,  1884,  269,  274;  M.  W.  Drobisch, 
Abh.  d.  kgl.  sachs.  Ges.  d.  Wiss.,  math.-phys.  CI.  B.  II.,  1855,  35. 

(4)  Ebbinghaus,  296  f. ;  Helmholtz,  65  ff. 

(5)  See  esp.  Ebbinghaus,  283  ff. 

(6)  The  most  satisfactory  theory  is  that  of  Helmholtz  (as  it 
finally  took  shape  under  the  influence  of  Hensen,  Exner  and 
othersX  modified  by  Ebbinghaus.  —  See  Ebbinghaus,  313  fF. ; 
Helmholtz,  145  ff.,  150  f.,  158,  166;  Stumpf,  Tonpsych.,  ii.,  esp. 
255  f-.  450  f.,  497  (see  also  i.,  refs.  under  Schnecke  in  index);  cf, 
Beitr.,  L,  51  f. 

EXPERIMENT  V 

§  15.  The  Phenomena  of  Interference  :  Beats.  —  Materials.  — 
The  forks  required  for  this  experiment  are  such  as  can  be  pur- 
chased from  the  music-dealers  for  15^  and  20/.  In  selecting 
from  the  stock,  (i)  choose  forks  which  hold  their  tone  well,  do 
not  '  ring  off  *  quickly  (there  are  great  differences  among  cheap 
forks  in  this  regard),  and  (2)  be  sure  that  forks  which  bear  the 
same  pitch-mark  really  give  a  perfect  unison,  i.e.,  are  wholly  free 
from  beats,  when  you  sound  them  together.  Take  both  V-forks ' 
and  *tf-forks  * :  the  former  give  the  tone  c^y  the  latter  d^. 

Odd  piano-hammers,  of  all  sorts,  can  also  be  procured  from 
the  music-dealers. 

For  resonance-jars,  use  tall,  narrow  bottles  (salad-dressing 
bottles  or  tall  pickle-bottles  answer  well). 


56  Auditory  Sensation 

The  wax  should  not  be  ordinary  beeswax,  which  crumbles 
easily  and  is  difficult  to  manipulate,  but  a  mixture  of  beeswax 
and  Venice  turpentine,  in  the  proportions  of  3:1. 

To  prepare  this  wax,  melt  the  beeswax  and  mix  in  the  Venice  turpentine. 
Colour  (if  desired)  with  vermilion,  etc.  If  colouring  matter  is  used,  stir  the 
mixture  long  enough  to  prevent  its  sinking  to  the  bottom. 

Experiment  (i).  —  Most  observers  have  a  distinct  preference 
for  listening  with  a  particular  ear.  It  is  this  which  is  termed  '  the 
better  ear '  in  the  text,  and  which  should  be  turned  towards  the 
source  of  sound.     See  Stumpf,  Tonpsychologie,  i.,  1883,  364. 

(i),  (2)  For  this  experiment,  see  Helmholtz,  Sensations  of 
Tone,  1895,  161. 

(3)  The  counting  of  beats  is  one  of  the  fundamental  laboratory 
arts  mentioned  on  p.  xxxv.  The  amount  of  practice  necessary 
to  accurate  counting  differs  considerably  from  individual  to  indi- 
vidual. The  same  forks  and  loads  should  be  used  by  several 
students,  and  the  results  compared.  —  For  illustrations  of  actual 
counts,  see  Exp.  VI. 

If  the  forks  chance  to  be  struck  unevenly,  their  intensities  can 
be  roughly  equalised  by  holding  the  weaker  nearer  to,  and  the 
stronger  farther  from,  the  mouth  of  the  resonator.  But  E  should 
aim  at  equal  force  of  strokes. 

It  makes  no  appreciable  difference  whether  the  two  beating  forks  be  held 
over  a  single  resonator,  or  whether  each  be  held  over  a  bottle  of  its  own. 
Indifferent  tuning  also  answers  the  purposes  of  this  experiment  as  well  as 
exact,  though  tolerably  accurate  tuning  gives  a  clearer  and  sharper  beat. 

(sMS)- — "^^^  5-fold  repetition  and  the  lo-sec.  counting-time 
are  arbitrary  limits.  With  better  forks,  the  beats  may  with 
advantage  be  counted  {a)  as  singles,  for  10  sec,  {b)  in  pairs,  for 
20  sec,  and  (c)  in  fours,  for  40  sec.  Some  observers  have  a 
natural  tendency  to  count  by  two's,  three's  or  four's  :  see  Exp. 
XXXI. 

(6)  Beats  can  be  counted  accurately  between  the  limits  2  and 
5  in  the  i  sec,  and  most  easily  when  they  occur  3  or  4  times 
per  sec.  Below  2,  and  certainly  below  i,  they  are  too  slow  for 
exact  differentiation.     Beats  of  6  or  7  in  the  i  sec  may  be  fol- 


{  15-   Beats  57 

lowed  for  a  few  seconds  by  the  tapping  of  a  pencil  on  paper,  and 
the  dots  counted  ;  but  the  method  is  not  accurate. 

It  is  a  good  general  principle  that  forks  should  never  be 
touched  with  the  unprotected  hand :  a  warm  fork  flats.  The 
small  forks  used  in  these  experiments  do  not  retain  their  heat  long 
(see  Exp.  VI.);  but,  nevertheless,  they  should  be  held  in  sheaths 
of  chamois  leather  or  thick  brown  paper,  or  mounted  on  wooden 
handles.     To  test  the  efifect  of  temperature,  proceed  as  follows. 

Experiment.  —  Load  one  of  the  forks  with  a  piece  of  wax 
large  enough  to  induce  20  or  30  beats  in  the  10  sec.  Lay  the 
loaaed  fork  on  the  table,  by  the  resonator.  Hold  the  other, 
normal  fork  in  the  axilla  for  i  minute.  Now  let  the  two  forks 
beat.  The  total  number  of  beats  will  probably  have  been  re- 
duced by  2  or  3  in  the  10  sec.  count.  —  Repeat  5  times. 

A  stni  simpler  form  of  the  experiment  is  to  take  two  forks,  which  are  in 
anison  at  the  temperature  of  the  room ;  to  heat  one  of  them,  as  described ; 
and  then  to  let  them  beat  over  a  common  resonator. 

See  H.  Ebbinghaus,  Grundzuge  d.  Psychologic,  i.,  1897,  301  ; 
Helmholtz,  Sensations  of  Tone,  444  f. ;  Sanford,  Course,  66  f., 
cxps.  79,  80. 

The  question  as  to  the  pitch  of  the  beating  tone-complex  may 
be  divided  into  two  questions.  We  may  ask,  first,  as  to  the 
pitch  of  the  beats  themselves ;  and,  secondly,  to  which  of  the 
component  tones  of  the  complex  the  beats  are  attributed.  The 
answer  to  the  latter  question  is,  to  some  extent,  included  in  that 
to  the  former.  In  neither  case  is  the  answer  easy ;  and  in 
neither  case  must  the  Instructor  expect  too  close  an  approxima- 
tion to  the  norm,  on  the  part  of  unpractised  students. 

The  following  results  were  obtained  {A)  from  an  untrained 
observer,  who  was  wholly  'unmusical,*  and  {B)  from  a  trained 
observer,  who  was  fairly  musical.  Stumpf  s  results  are  given  for 
the  sake  of  comparison. 

Series  L  Forks  ^  and  ^,  of  480  and  512  vs.  respectively. 
"If  I  give  two  tones,  about  a  semitone  apart,  in  the  middle 
region  of  the  scale  {e.g.,  g^^  and  a^  on  the  violin),  I  hear  the  two 
primary  tones,  but  also,  over  and  above  these,  a  third  tone  which 


58 


Auditory  Sensation 


lies  between  them,  somewhat  nearer  the  lower  than  the  higher. 
This  third  tone  has  a  very  soft  colouring,  and  with  keen  atten- 
tion is  localised  within  the  ear ;  it  is  this  tone  that  beats,  while 
the  primary  tones  remain  constant.  The  two  primary  tones  are, 
in  my  judgment,  noticeably  weakened"  (Stumpf). 


(-4) 

1.  The  'fusion'  does  the  beating, 

but  the  primary  tones  are 
heard  intermittently. 

2.  The  *  fusion'  beats;    the   pitch 

seems  nearer  that  of  the  lower 
tone.  One  of  the  primaries  is 
heard ;  uncertain  as  to  the 
other. 

3.  Beating  tone  an  intermediate  low 

tone;  upper  primary  accom- 
panied it.  Presently  changed 
to  a  higher  beating  tone,  with 
lower  primary  as  accompani- 
ment. 

4-    As  3. 

5.  Beating  tone  low,  with  upper  pri- 
mary accompanying.  Do  not 
think  that  the  beating  tone  is 
identical  with  the  lower  pri- 
mary; lower? 
6,7.  As  3. 
8.  As  3,  except  that  the  pitch  of  the 
higher  beating  tone  in  the 
second  part  is  lower  than  the 
pitch  of  the  upper  primary. 

9.   A  low  beating  tone,  different  from 
the  primaries. 

10.  Middle    tone     beats ;     at    first 

seemed  near  lower,  then  rose 
to  nearer  upper  primary. 

11.  A  middle  tone,  near  lower  pri- 

mary, beats :  both  primaries 
heard  throughout. 

12.  As  3. 

13, 14, 15.  A  middle  tone,  nearer  lower 
primary,  beats  :  upper  primary 
beard. 


(.B) 


I.   As  ^. 


2.   As  Stumpf. 


3.        " 


4.  " 

5.  Heard  beating  tone  between  the 

two  primaries.     Also  heard  a 
difference-tone   (probably   the 
tone   which    A    took    for  the 
beating  tone) . 
6,7.  As  Stumpf. 
8.       « 


9.        " 

10.  As  A. 

11.  « 


12.  « 

13,  14,  15.   As  Stumpf. 


{  15.  Beats  59 

SerUs  II,  Attention  directed  to  lower  tone,  "  Without  analy- 
sis, the  beats  are  naturally  apprehended  as  a  peculiarity  of  the 
whole.  With  analysis,  they  are,  in  the  case  of  the  most  exact 
hearing  (Hinhbrcn)  and  of  adequate  practice,  attributed  to  the 
tones  to  which  they  really  belong :  and  therefore,  under  certain 
circumstances  [those  of  the  present  experiment],  to  neither  of 
the  two  primaries,  but  to  an  intermediate  tone.  With  less  exact 
hearing,  however,  they  are  ascribed  either  to  the  two  primaries 
or  to  that  one  of  them  to  which  the  attention  chances  to  be 
more  especially  directed.  The  attention  then  combines  into  a 
narrower  whole  the  two  moments  which  it  is  trying  to  grasp 
simultaneously,  this  primary  tone  and  the  beats.  Many  ob- 
servers think  that  they  actually  hear  (not  merely  note)  the  two 
tones  themselves  alternately,  confusing  the  alternation  of  in- 
tensity and  of  attention  with  alternation  of  tone ;  the  constant 
interruption  of  each  tone  renders  more  exact  observation  diffi- 
cult "  (Stumpf> 


{A)  (B) 

16.  Heard  middle  beating  tone,  near      16.   As  /4,  except  that  upper  primary 

lower  tone,  as  well  as  the  lower  was   heard    intermittently,  as 

tone  itself.  attention  fluctuated. 

17.  A  low  beating  tone  only.  17.   As  16. 

18.  Beating  tone,  apparently  lower  18.   As  16. 

than  lower  primar)' ;  upper  pri- 
mary heard  intermittently. 
19-21.  A  beating  tone;,  at  or  near  the      19-21.  As  i4. 
lower  primary:  upper  primary 
beard  intermittently. 


Series  III.    Attention  directed  to  higher  tone. 

22.   Low  beating  tone,  near  or  at  lower      22.  As  A, 
fork;  upper  primary  continu- 
ous. 

23-26.   Middle    beating    tone;    pri-      23-26.  " 
manes  heard  intermittently. 

27-30.   Beating   tone  seems   nearer     27-30.  ** 
higher  fork. 


6o  Auditory  Sensation 

The  series  show,  fairly  well,  how  near  one  may  expect  to  come 
to  Stumpf's  results.  In  recording,  the  student  should  distin- 
guish, so  far  as  possible,  the  irregularities  due  to  imperfect 
analysis  and  lack  of  practice  from  those  due  to  uneven  striking 
of  the  forks,  fatigue,  etc. 

Series  IV.  Forks  /^  and  g^,  341  and  384  vs.  "If  I  take 
tones  that  lie  farther  apart,  in  the  same  [the  middle]  region  of 
the  scale,  I  do  not  hear  any  middle  tone,  but  only  the  two 
primaries ;  and  these  two  seem  themselves  to  beat.  If,  how- 
ever, I  concentrate  the  attention  preponderantly  upon  the  one 
of  them,  this  always  seems  to  be  the  beating  tone  "  (Stumpf). 

(^)  (^) 

In  this  series,  A  always  heard  a  beat-  Invariably  as  Stumpf.     But  no  diffi 

ing  tone  which   lay  lower  in  the  culty  in  hearing  the  beating  of  the 

scale  than  the  lower  primary.    This  difference-tone, 
tone  could  be  verified  as  a  differ- 
ence-tone. 

Series  V.  "  If  I  take  two  tones  that  lie  much  nearer  together 
than  a  musical  semitone,  so  that  they  approximate  the  difference 
limen  for  simultaneous  tones,  I  get  one  tone,  and  that  beating. 
It  is  hard  to  say  whether  it  lies  between  the  primaries  "  (Stumpf). 

Two  forks,  (^  oi  528  vs.  The  one  fork  is  flatted,  by  means  of 
wax,  to  516  vs.     Results  for  {B),  as  Stumpf  ;  for  {A)y  as  follows. 

1.  Only  one  tone  heard,  nearer  lower  fork,  and  situated  in  space  nearer  th^ 

lower  fork. 

2.  Only  one  tone  heard,  nearer  lower  fork. 

3.  4.   As  2. 

5 .  Beating  tone  seemed  to  be  nearer  lower  primary ;  but  upper  primary  was 

faintly  distinguished. 

6.  Higher  tone  carried  the  beats. 

7.  As  6. 

8.  Only  one  tone  heard,  apparently  between  the  primaries. 

9.  As  8. 

10.  One  tone  beating ;  nearer  lower  primary. 

11.  As  10,  except  that  when  the  beats  grew  faint  the  higher  primary  seemed 

to  come  out  and  take  the  beats. 

12.  13.   As  8. 

14.  One  beating  tone,  near  lower  primary. 

15.  As  14. 


$  id    PUch-dijfertnee  of  tht  Ears  6i 

Sec  Stumpf,  Ton  psychologic,  ii.,  480  ff.,  490 ;  Sanford,  Course, 
68.  cxp.  81  ;  F.  Mclde,  Pflugcr's  Archiv,  Ix.,  1895,  623  (Melde's 
'resultant*  tones  are  not  to  be  confused  with  Tyndall's  're- 
sultant •  =  * combination •  tones);  F.  Kriiger,  Phil.  Studien,  xvi., 
1900,  307,  568. 

Alternative  Experiment. — The  author  has  recommended 
forks  for  this  experiment,  for  the  reason  that  forks  are  largely 
employed  in  method-work  and  in  research,  so  that  it  is  well  for 
the  student  to  accustom  himself  to  their  use.  Ellis,  following  a 
suggestion  of  Helmholtz  concerning  stopped  organ-pipes,  has 
devised  a  simple  and  effective  instrument  for  the  demonstration 
of  beats,  as  follows.  "A  cheap  apparatus  ...  is  made  with  two 
'pitch  pipes,'  each  consisting  of  an  extensible  stopped  pipe, 
which  has  the  compass  of  the  once-accented  octave  and  is  blown 
as  a  whistle,  the  two  being  connected  by  a  bent  tube  with  a 
single  mouthpiece.  By  carefully  adjusting  the  length  of  the 
pipes  "  it  is  possible,  first,  "  to  produce  complete  destruction  of 
the  tone  by  interference,  the  sound  returning  immediately  when 
the  mouth  of  one  whistle  is  stopped  by  the  finger.  Then,  on 
gradually  lengthening  one  of  the  pipes,  the  beats  begin  to  be 
heard  slowly,  and  increase  in  rapidity.  The  tone  being  nearly 
simple,  the  beats  are  well  heard."  —  Ellis'  Helmholtz,  167,  ttote. 

The  instrument  is  admirable  for  demonstration.  If  connected 
with  some  sort  of  air-supply,  it  can  be  used  for  the  counting- 
experiments  of  the  text. 

EXPERIMENT  VI 

§  16.  The  Pitch-difference  of  the  Two  Ears.  —  Materials.  — 
The  cheap  forks  of  Exp.  V.  suffice  for  this  experiment. 

The  <7-forks  will  probably  be  stamped  435.  This  figure  should 
be  tested,  preferably  by  the  graphic  method.  The  two  forks 
used  for  the  experiments  quoted  below  were  thus  tested  by  com- 
parison with  the  curve  of  a  standard  electrically-driven  tuning- 
fork  of  100  vibrations  in  the  i  sec.  The  results  of  five  counts 
were:  432,  432.3,  432.2,  432.3,  432:  average,  432.16  ±.128. 
The  g  below  this  is  a  tone  of  388.94. 

The  f-forks  will  probably  be  stamped  C.  The  c  above  the  a 
of  435  is  a  tone  of  512.     Musical  pitch  is,  however,  so  variable  a 


62  Auditory  Sensation 

matter  that  the  r-forks  may  very  possibly  belong  to  a  different 
scale  from  the  ^-forks.  Those  used  in  the  experiments  quoted 
below  proved,  on  comparison  with  the  loovibr.  fork,  to  have  a 
pitch  of  528.27  ±.07  (the  results  of  four  counts  were:  528.2, 
528.4,  528.3,  528.2).  That  is  to  say,  they  had  been  tuned  to  a  ^r 
of  528,  the  a  below  which  is  an  a  of  440.  — The  b  below  a  ^  of 
528.27  is  a  tone  of  495.25. 

Experiment.  —  It  is  usually  the  case  that  the  right  ear  is 
the  high-pitch,  the  left  the  low-pitch  ear.  The  pitch-difference 
varies  in  amount  in  normal  ears.  It  may  be  as  much  as  1/4 
of  a  musical  tone.  The  average  difference,  for  this  part  of  the 
musical  scale,  may  however  be  estimated  at  about  1/16  of  a 
tone. 

Much  time  may  be  saved  in  the  performance  of  the  experi- 
ment if  the  Instructor  prepare  beforehand  a  short  series  of  balls 
of  wax  whose  attachment  to  the  fork  produces  a  known  number 
of  beats.     An  illustration  will  make  the  method  clear. 

{a)  In  a  series  of  13  preliminary  experiments,  descending  (from 
right  fork  'too  sharp'  to  right  fork  'equal'),  made  with  the  ^- 
forks,  the  Instructor  found  that  the  pitch-difference  between  the 
right  (sharp)  and  left  (flat)  ears  was  a  fraction  over  4  vibrations. 
That  is,  the  pitch-difference  disappeared  when  the  right  fork  was 
loaded  with  a  bit  of  wax  large  enough  to  give  a  fraction  over  4 
beats  per  sec.  when  the  two  forks  were  sounded  together.  —  In 
a  series  of  7  experiments  ascending  (from  right  fork  '  too  flat '  to 
right  fork  'equal'),  made  with  the  same  forks,  the  pitch-difference 
found  was  again  a  fraction  over  4  vibrations. 

{b)  The  lump  of  wax  which  gave  4 -h  vibrations  in  the  first 
series  was  divided  as  accurately  as  possible  into  four  pieces. 
The  value  of  these  pieces  was  then  determined  by  the  beat- 
method.  A  bottle,  tuned  to  the  pitch  of  the  loaded  fork  by 
pouring  in  water,  served  as  resonator ;  the  beats  of  the  loaded 
and  normal  forks  were  counted  for  5  periods  of  10  sec.  each. 
The  results  were  as  follows  : 

Piece    I Beats  12    ,  12-f,  12 -f-,  12     ,  12 

Pieces  i,  2 "      20  +  ,  20-f ,  20  +  ,  20-I-,  20-I- 

"       1,2,3 "      30     ^30    .30    ,30    ,30 

"       i»2,  3,  4 «     40    ,40  +  ,  40  +  ,  40    ,40 


{  i6.   Pitch^iffcrence  of  the  Ears  63 

The  plus  of  lines  i  and  4  was  estimated  at  a  quarter-beat ;  that 
of  line  2  at  a  half-beat     The  averages  would  therefore  bi 
20.5.  30.  4a  I. 

For  the  ascending  series,  a  new  determination  was  made  of  the 
lump  which  had  given  44-  beats  in  the  second  trial  set,  and  3  ad- 
ditional pieces  were  prepared  : 

Piece    P  =  Pieces  I,  3,  3,  4  Beau  40    ,  40  +  ,  40+,  40  +  ,  40 

Pieces  P,  5         =     "      1,2,3,4,5  "     44+,  45    »44  +  ,45     » 45 

**      P,  5, 6     =     '*      1,2,3,4,5,6  "      50    ,50  +  ,  50    ,50-f,5o 

•*      P,  5»6,7=      *      1,2,3,4,5,6,7        "     60    ,60  +  ,  60    ,60+,  60  + 

The //wf  of  lines  i,  3  and  4  was  estimated  at  a  quarter-beat: 
that  of  line  2  at  a  half-beat  The  averages  would  therefore  be ; 
40.15,  44.8,  50.1,  60.15. 

(c)  The  half-tone  ^-^  covers,  as  we  have  seen,  528.27—495.25 
or  33  vibrations.  The  values  n  and  «'  are  both  a  fraction  over 
4  vibrations.  The  value  «-f  «'/i32  is  therefore  8-1-/ 132,  or 
approximately  1/16. 

(</)  A  similar  set  of  wax-pieces  was  prepared  for  the  a-forks : 

Piece  I  Beats  10  ,10    ,10  .10    .  10  Av.  lo. 

Pieces  I,  a  "  XS  .  »4+.  »5  .  '4+.  'S  "    14-8 

**  1. 3, 3  "  90  ,  ao    .  ao  .  ao    ,  ao  "    ao 

"  I,  a.  3,  4  "  a7+,  a8    ,  a8  ,  a/^-,  a8  "    37.8 

Pleee   P            —       -  x,  a.  3, 4  •  a8  ,  28    ,  a8  .  27-I-.  a8  "    37.9 

Pieces  P.  5         -       -  x,  a.  3. 4, 5  "  40  ,  40    ,  40  .  40    .  40  "40 

-  P.  5. 6     -       "  1.3.3.4.5.6  ••  50  ,49+.  49+.  50    .49+  "    49.7 

-  P.  5.  6.  7  -       "  I.  a.  3, 4,  5, 6,  7  60  ,  6o4-.  60  ,  60    ,  60-f-  "    6ai 

(r)  The  whole  tone  g^-a^  covers  432.16—388.94  or  43.2  vi- 
brations. The  values  n  and  «'  are  2.78  and  2.79  vibrations 
respectively.  The  fraction  n-{-n'/^.^  is  5.57/86.4  or  approxi- 
mately 1/16. 

(/)  It  is  well  to  work  out  an  experiment  accurately,  even  if 
the  result  is  to  be  merely  approximate.  But  the  Instructor  must 
carefully  distinguish,  on  the  student's  behalf,  the  relative  accuracy 
of  the  parts  of  an  experiment  like  the  preceding,  (i)  Granted 
that  the  standard  fork  is  accurate,  the  pitch-numbers  of  the  small 
forks  have  been  accurately  determined  within  the  limits  given 
(  ±  about  I  / 10  of  a  vibration).  A  longer  series  of  determinations 
would  have  reduced  the  limits  of  variation  ;  but  the  values  ob- 
tained are  fully  adequate  to  the  work  required  of  them.     (2)  The 


64  Auditory  Sensation 

critical  beat-values  (4.01,  4.015  ;  278,  2.79  per  sec.)  are  also  suf- 
ficiently accurate.  At  a  liberal  estimate,  and  with  all  sources  of 
error  taken  into  account,  the  limits  of  variation  could  not  have 
exceeded  1/2  a  beat  in  the  10  sec,  or  1/20  of  a  beat  in  the  i  sec. 
Our  values  are,  then,  at  the  worst,  4.01  ±  .05,  etc.  (3)  On  the 
other  hand,  the  final  determination  of  equality  of  pitch  is  only 
approximate.  A  given  pitch,  heard  by  the  one  ear,  corresponds 
not  to  a  single  (flatter  or  sharper)  pitch,  heard  by  the  other,  but 
to  a  small  zone  or  band  of  pitches.  Thus,  the  pitch  of  528,  heard 
by  the  left  ear,  corresponds  not  only  to  the  pitch  of  524,  heard  by 
the  right ;  but  to  a  number  of  flat  pitches,  —  perhaps  to  any 
between  the  limits  520  and  525.  Our  short-cut  experiment  with 
the  prepared  wax  balls  does  not  tell  us  whereabouts  in  this  zone 
our  final  determination  falls,  whether  in  the  middle,  or  towards 
the  top,  or  towards  the  bottom.  Hence  this  determination  is 
merely  approximate. 

The  above  sets  of  8  pieces  have  proved  sufficient  for  ordinary 
laboratory  work.  Their  beat-values  must,  of  course,  be  retested 
from  time  to  time,  —  once  a  week,  if  they  are  much  in  use,  since 
the  turpentine  evaporates  readily ;  and  E  should  always  verify 
the  beat-value  of  the  critical  load  (P,  or  i,  2,  3,  4).  There 
will  be  occasions  when  he  must  pare  off,  or  add  on,  small  bits 
of  wax. 

To  ensure  constancy  of  place  of  attachment  of  the  wax,  a  cross- 
line  may  be  scratched  on  the  fork,  about  5  mm.  from  the  extremity 
of  the  prong  to  be  loaded.  One  ball  is  laid  across  this  line,  one 
on  either  side,  and  a  fourth  is  squeezed  down  upon  the  three. 

It  is  well  to  use  holders  for  the  forks,  as  explained  in  Exp.  V. 
The  experiments  described  above  have,  however,  been  made 
several  times  over  without  such  holders,  and  in  no  instance  have 
the  inequalities  of  temperature  due  to  unequal  handling  of  the 
two  forks  been  large  enough  to  produce  any  appreciable  variation 
in  the  beat-values  of  the  loads. 

Literature.  —  Stumpf,  Tonpsychologie,  i.,  1883,  234!,  266; 
ii.,  1890,  320. 

Helmholtz,  Sensations  of  Tone,  1895,  445. 
Sanford,  Course,  1898,  62^  exp.  70  b. 


I 


§  17.    Pitch'tiiff'irimi'  in  Piniiitrai  Hearing  65 

§  17.  Related  EzperimenU.   ^i;  ///<  /  ^cc  in  Binaural 

Hearing.  —  Wo  have  seen  that  if  the      .  vs  arc  brought, 

successively,  to  the  two  ears,  the  right-ear  fork  seems  to  be 
higher  pitched  than  the  left-ear  fork.  But  if  the  two  forks  are 
held  simultaneously  before  the  two  ears,  no  pitch-difference  is 
remarked :  one  and  the  same  tone  appears  to  come  from  either 
fork.  Over  how  wide  a  range  of  pitches  does  this  equality  of 
simultaneous  sensations  extend  ? 

Flat  the  left-ear  fork  a  trifle,  by  sticking  on  a  small  bit  of  wax. 
Strike  it  and  the  right-ear  fork,  and  let  O  listen  to  them  simul- 
taneously. Strike  them  gently,  or  beats  will  arise,  and  distract 
(7's  attention  from  the  required  judgment  of  equality  or  inequality. 
—  O  still  hears  only  one  tone  from  the  two  stimuli.  Add  on  still 
more  wax ;  again,  the  same  result  is  obtained.  Continue  the 
addition,  until  the  tone  from  the  two  forks  is  distinctly  impure, 
r.,  until  there  is  a  distinct  pitch-difiference  in  simultaneous 
hearing.  Be  sure  that  this  is  a  sensed  difference,  and  not  a 
physical  difference  betrayed  by  beats ;  on  no  account  must  the 
forks  be  struck  loudly  enough  to  beat.  —  Now  pare  off  a  very 
small  piece  from  the  lump  of  wax ;  still,  perhaps,  the  pitch- 
diflFerence  remains.  Pare  off  another  morsel.  The  pitch-dififer- 
ence has  disappeared  again. 

When  this  point  of  disappearance  has  been  reached,  the  experi- 
ment is  so  far  concluded.  We  have  now  merely  to  determine 
the  pitch-number  of  the  loaded  fork.  ( i )  Let  the  two  forks,  the 
loaded  and  the  normal,  beat  over  the  bottle-resonator.  Can  the 
beats  be  counted  accurately }  Probably  they  are  too  quick.  You 
must  therefore  (2)  have  recourse  to  the  graphic  method.*  The 
iifiference  between  the  pitch-numbers  of  the  two  forks  will,  in  all 
probability,  amount  to  8-12  vibrations.  Not  more  than  5  beats 
per  sec.  can  be  counted  with  accuracy  (p.  56). 

We  know  already,  from  the  previous  experiment,  that  a  fork  of 
528  on  the  left  is  equal  to  a  fork  of  524  on  the  right.  We  must, 
therefore,  add  4  vibrations  to  the  8-12  vibrations  of  the  present 
determination.  Equality  of  simultaneous  sensations  extends, 
then,  over  a  range  of  12-16  vibrations ;  a  fork  of  528,  heard  by 

>  See  Exp.  XXIV. 


66  Auditory  Sensation 

the  left  ear,  is  indistinguishable  from  a  fork  of  512-516,  heard 
simultaneously  by  the  right. 

Literature.  —  Stumpf,  Tonpsychologie,  ii.,  1890,  320. 

(2)  The  Ear  as  Resonator.  —  {a)  The  cavity  of  the  external  ear 
serves  as  a  resonance-chamber  to  reinforce  the  intensity  of  tones 
lying  between  ^  and  g^. 

Sound  the  (open)  Quincke  tubes,^  g^  to  g^,  in  regular  order, 
at  as  even  an  intensity  as  possible.  O  will  say  that  one  or  two 
of  the  highest  tubes  give  a  peculiarly  cutting,  piercing,  screaming 
tone.  For  some  subjects,  the  tone  may  be  positively  painful.  — 
Repeat  the  experiment,  in  reverse  order  (from  g^  to  g^) ;  and, 
again,  in  random  order.  Note  that  the  piercing  tones  lie  always 
within  the  given  limits.  —  Now  place  in  the  ears  small  pieces  of 
glass  or  rubber  tubing,  to  project  about  i  cm.  beyond  the  opening 
of  the  external  meatus.  The  character  of  the  resonance-chamber 
has  been  changed,  and  the  tones  that  were  piercingly  loud  in  the 
previous  experiments  prove  to  be  as  soft  and  weak  as  the  rest  of 
the  octave. 

{b)  The  middle  ear  serves  as  resonance-chamber  in  the  ex- 
perience of  *  singing  in  the  ear.'  The  pitch  of  the  *  singing' 
tone  is  that  of  the  proper  tone  of  the  middle  ear.  It  may  be 
determined  on  the  piano,  lying  usually  within  the  limits  of /^j) 
and^3jf 

Literature.  —  Helmholtz,  Sensations  of  Tone,  1895,  116. 
Stumpf,  Tonpsychologie,  i.,  1883,  241  ;  ii.,  1890,  409,  443. 
Kiilpe,  Outlines,  1895,  108. 

EXPERIMENT  VH 

§  18.  Combination-tones.  —  A.  L  Materials. — The  pitch  of 
the  Quincke's  tubes  must  be  tested,  preferably  by  tuning-forks 
and  resonators,  to  avoid  the  octave-illusion.  The  author  has 
known  a  tube  to  be  reported  as  two  octaves  below  its  real  pitch, 
when  matched  on  the  piano,  and  the  mistake  of  a  single  octave 
is  not  at  all  uncommon  (Stumpf,  Tonpsychologie,  ii.,  407  f.).  The 
pitch  of  the  sets  of  tubes  that  are  on  the  market  seems  to  vary 
very  considerably.  Those  of  the  Cornell  laboratory  begin  with 
a  rather  sharp  g'^.     Another  set  is  said  to  range  from  ^  to  ^. 

1  See  Exp.  VII. 


§  l8.   Combinatiim'totus 


«7 


DwDMCB  09  Tnan  I>iws»> 


Triple  octmve  and  major  ^ 
Mrrenth  m 


Triple 


Double  octave  and 
uor  third 


Double  ocuvc 

Twelfth 

Major  eleventh— 

Ocuve 

Major  sixth 

Fifth 

Major  third  ■¥ 

Major  seooiid+ 

Unison 


c!='4» 


1 


▼n.-KAT10«  0 

IirnavAU 


15:16 

4:$ 

i<k        3-'4 

i      2:3 

r  s=s 


I*    "» 


68  Auditory  Sensation 

The  pitch  of  an  open  pipe  is  given,  approximately,  by  the  physical  formula : 

V 

2/+  .6w 

where  n  is  the  pitch  number,  v  the  velocity  of  sound  in  air  (340  m.  per  sec.)> 
/  the  length  and  w  the  width  of  the  pipe.  See  Rayleigh,  The  Theory  of 
Sound,  ii.,  1896,  202  f.,  219.  Recourse  should  be  had  to  this  formula  only 
after  the  student  has  determined  the  pitch  of  the  tubes  *  by  ear.' 

The  text  has  assumed  the  correctness  of  the  ordinary  rule  that  the  pitch  of 
an  open  pipe  is  the  same  as  that  of  a  stopped  pipe  of  half  its  length.  The  rule 
is  only  approximately  correct:  Rayleigh,  ii.,  61,201;  Helmholtz,  Sensations 
of  Tone,  88  (and  Translator's  note)  ff.  In  the  case  of  the  Quincke's  tubes, 
and  of  the  widest  intervals,  the  error  may  amount  to  a  semitone.  This  fact, 
as  well  as  the  errors  of  mistuning  (see  p.  72  below),  should  be  discovered  by 
a  careful  O.  Much  may  be  done  by  adjustment  of  the  blow-tubes  and  by 
regulation  of  the  force  of  breathing. 

Preliminaries.  —  E's  adjustment  of  the  tubes  should  be  care- 
fully performed  and  as  carefully  scrutinised.  An  unpractised 
subject  will  hardly  be  able  to  hear  a  difference-tone  unless  the 
generators  can  be  sounded  loudly  and  continuously  ;  and,  in  this 
field  of  observation,  practice  wears  off  so  quickly  that  all  subjects 
may  be  regarded  as  unpractised,  even  if  their  attention  has  been 
called  (in  earlier  psychological  Courses,  or  in  lectures  on  Physics) 
to  the  existence  of  combination-tones. 

O  should  note  down,  in  his  introspective  record,  all  the  char- 
acteristics of  the  difference-tones  heard.  Thus  he  should  remark 
their  relative  intensity,  as  compared  with  the  generators  ;  their 
relative  difficulty  of  identification ;  their  localisation,  etc.,  etc. 
Beating  of  the  generators  obscures  them  ;  and  those  that  lie  near 
the  pitch  of  the  lower  generator  (roughly,  those  of  the  upper  half 
of  the  octave)  are  difficult  to  hear.  They  are  localised,  not  at  the 
source  of  sound,  but  either  diffusely  in  space,  or  in  the  ear  (some- 
times, if  very  low,  in  the  head). 

Experiment.  — (i)  The  /^w^r  generating  tone  is  kept  sound- 
ing in  order  that  O  may  be  strongly  impressed  by  its  pitch,  and 
so  be  able  the  more  easily  to  recognise  the  (still  lower)  differ- 
ence-tone. 

(i)-(6)  The  full  tale  of  first  difference-tones,  within  the  octave 
{^-(^,  is  shown  in  the  preceding  diagram.  The  student  should 
prepare  a  similar  diagram,  for  the  octave  g^-g^. 


§  1 8.   CombimaiWH'Umgs 


69 


Minor  second  + 

Major  second  + 
Major  third 

Fourth 

Fifth 

.\iajor  si.xih  + 

OcUve 

Ocuve  and  major  third 

Octave  and  fifth 

Double  octave  and  ma- 
jor second 

Triple  ocUve 

[Tone  absent:  unison, 
I :  I,  gives  i] 


h 


ii 


^ 


VtB.-KATlOS  O 
iKTWIVALt 


15:16 

8:9 
5:6 


i^   3:4 

\T  32:45 

T3:S 
^  8:15 


70  Auditory  Sensation 

(4)  In  verifying  (9*s  introspections,  here  and  in  following  ex- 
periments, E  should  not  merely  sound  the  tube  that  gives  the 
difference-tone,  and  be  content  with  this  single  identification. 
When  O  has  said  that  the  tone  is  audible,  he  should  give,  in 
random  order,  the  right  tube,  that  of  next  higher,  and  that  of 
next  lower  pitch,  and  require  O  to  choose  among  them,  —  to  say 
which  of  the  three  proper  tones  comes  nearest  to  the  heard 
difference-tone. 

It  is  not  probable  that  many  of  the  difference-tones  of  this 
series  —  exp.  (4)  —  will  be  heard  at  all. 

II.  The  preceding  diagram  shows  the  second  difference-tones 
for  intervals  within  the  octave  ^-^.  The  student  should,  again, 
prepare  a  diagram  for  g^-g^. 

(9),  (10)  Probably,  only  the  difference-tones  of  the  intervals 
from  fifth  to  octave  will  be  audible. 

III.  The  harmonium  or  harmonical  is  recommended,  because 
its  clangs  are  so  constituted  as  to  give  especially  strong  sum- 
mation-tones, and  because  the  summation-tones  are  clearest  with 
low-pitched  generators  which  cannot  be  obtained  from  the  tubes. 
If  no  harmonium  is  available,  a  few  experiments  may  be  tried  with 
the  stopped  tubes  {g'^-g^\     They  will  probably  be  unsuccessful. 

B.  I.  The  following  diagram  shows  the  first  difference-tones 
for  the  intervals  i :  2  to  1:4  (c^-^).  Notice  that  the  difference- 
tone,  which  before  lay  always  below  the  lower  of  the  generating 
tones,  now  lies  between  the  two.  It  can  be  distinguished  only 
under  exceptionally  favourable  conditions. 

II.  and  III.  Within  the  range  of  intervals  1:2  to  1:3  (the 
second  and  third  difference-tones  for  which  are  given  in  the  text), 
the  second  difference-tone  will  probably  be  audible  over  the  first 
half,  the  third  over  the  upper  half.  We  found  above,  in  the  same 
way,  that  within  the  range  1:1  to  1:2,  the  first  difference-tone 
can  be  heard  over  the  first  half,  approximately,  and  the  second 
over  the  second.  It  follows  from  this  (and  the  inference  may 
be  tested,  if  time  allow)  that  within  the  range  1:3  to  1:4,  the 
second  difference-tone  will  again  be  heard  over  the  first,  the 
third  over  the  second  half ;  and  so  on. 

C.  The  details  of  this  final  experiment  must  be  arranged  to 
suit  the  resources  of  the  laboratory.     C?  should  (if  possible)  be 


$  1 8.    Combinatiothtoitts 


;i 


Dbtamcb  or  FtMT  Diwbii* 
imKiTOMB  AwnrB  Lowsa 


Major  second  + 
Mi^or  third 
Tritone  - 
rifth 

Major  sixth 
Major  seventh  — 
OcUve 

Minor  ninth  — 
Minor  tenth  — 
Major  tenth  + 
Octave  and  tritone— 
Twelfth 


VlS..RATIOf« 
IimUIYALS 


15:32 


72  Auditory  Sensation 

given  an  opportunity  of  hearing  the  combination-tones  on  violin, 
organ  and  harmonium.  The  piano  is  useful  for  testing  practice  : 
the  clangs  ring  off  quickly,  and  the  combination-tone  must  be 
heard  at  the  moment  the  hammers  strike  the  strings. 

(i)  Difference-tones  are  heard  best  with  high-pitched  genera- 
tors, on  account  of  their  own  depth  ;  summation-tones  with  low- 
pitched  generators.  Difference-tones  that  fall  below  the  octave 
€-<  are,  however,  intrinsically  so  weak  as  to  be  heard  with  diffi- 
culty.    They  are  plainest  within  the  limits  C-c^, 

(2)  As  a  general  rule,  generating  tones  (or  relatively  simple 
clangs)  give  better  difference-tones  than  generating  clangs  (or 
clangs  rich  in  overtones).  Tuning-forks  and  blown  bottles 
(stopped  organ-pipes,  tubes),  sounding  at  a  moderate  intensity, 
are  therefore  easier  to  work  with  than  string  or  reed  instruments. 
The  overtones  of  clangs  generate  difference-tones  of  their  own, 
which  serve  to  distract  attention  from  the  difference-tone  of  the 
fundamentals. 

In  certain  cases,  however,  the  secondary  difference-tones  may 
reinforce  the  primary  difference-tone.  This  happens  with  clangs 
of  shrill,  sharp,  thin  clang-tint.  Try  with  toy  trumpet,  double 
bicycle  whistle,  mouth  organ,  concertina. 

(3)  The  purer  the  interval  —  the  nearer,  i.e.,  the  generators 
approach  to  the  theoretical  vibration-ratio  —  the  more  distinct 
are  the  difference-tones.  It  must  be  remembered,  throughout 
this  experiment,  that  the  Quincke's  tubes  are  rough  and  cheap 
instruments,  and  that  perfect  tuning  is  not  to  be  looked  for 
in  them. 

Cognate  Experiment.  —  If  the  laboratory  possess  two  sets 
of  tubes,  the  beating  of  the  difference-tone  may  be  observed. 
Take,  e.g.,  the  three  stopped  tubes  i,  8  and  8.  If  the  8's  are  in 
unison,  slightly  fiat  one  of  them  by  pouring  in  water.  The 
beating  (first)  difference-tone  g^  will  be  heard. 

Literature.  —  Ebbinghaus,  Grundziige  der  Psychologic,  i., 
1897,  308  ff. 

Helmholtz,  Sensations  of  Tone,  1895,  152  ff.,  529  ff. 
L.  Hermann,  in  Pfiiiger's  Archiv,  xlix.,  1891,  499. 


$  19^    Clang-tini  73 

R.  Koenig,  Quelques  experiences  d'acoustique.  Pans,  27 
Quai  d'Anjou,  1882.     Pp.  87  ff. 

F.  Kriiger,  in  Philos.  Studien,  xvi.,  1900,  307,  568. 

M.  Meyer,  in  Zeits.  f.  Psych.,  xi.,  i89i5,  177. 

W.  Prcyer,  in  Wiedemann's  Annalen,  xxxviii.,  1889,  131 ; 
Sammlung  physiologischer  Abhandlungen,  Jena,  ii.,  1882,  17$. 

Sanford,  Course,  1898,  69,  exp.  82. 

Stumpf,  Tonpsychologie,  ii.,  1890,  243  ff. 


EXPERIMENT  Vm 

{  191  CUng-tint.  —  The  coloration  given  to  a  fundamental 
by  the  upper  partials  of  its  clang  is  known  as  clang-tint  in 
the  narrow  or  strict  sense.  The  other  characteristics  of  the 
clang  (constituents  of  clang-tint  in  the  wider  sense)  are  as 
follows 

( i)  Most  important  are  the  noises  which  accompany  the  tone- 
complex.  The  clangs  of  all  bowed  instruments  are  mixed  with 
a  very  noticeable  scraping  or  rubbing  noise.  The  hairs  of  the 
bow  are  irregular;  the  resin  is  unevenly  spread;  the  bowing 
arm  moves  and  presses  irregularly.  In  many  wind  instruments 
we  hear  the  whizzing  or  hissing  of  the  air  which  breaks  upon 
the  edges  of  the  mouth-piece.  The  pluck  of  the  harp  and  stroke 
of  the  mandolin  are  characteristic. 

(2)  The  manner  in  which  a  clang  begins,  and  the  rapidity 
with  which  it  elies  away,  differ  very  considerably  from  instru- 
ment to  instrument.  Some  clangs  are  dry,  short,  without  ring ; 
others  are  full,  durable.  Some  set  in  easily,  fluently  ;  others 
abruptly,  and  yet  with  a  certain  lumberingness  or  sluggishness 
(so  the  clangs  of  the  brass-wind). 

(3)  Pitch  (compass)  is  a  good  secondary  criterion.  A  shrill 
succession  of  notes  in  the  highest  musical  octave  must  come 
from  a  piccolo ;  the  tone  <?,  however  flutelike,  cannot  come  from 
the  flute. 

(4)  Intensity  is  a  similar  criterion.  The  loud  tones  of  the 
brass-wind  in  the  middle  region  of  the  scale  are  unmistakable. 

These  four  criteria  should  be  discovered  by  O  and  E,  in  the 
course  of  half  an  hour's  combined  introspection.     Others  are : 


74  Audi  to  fy  Sensation 

(5)  Variation  of  pitch  or  intensity  during  the  sounding  of 
the  clang.  —  The  tremolo  of  the  zither-string  affects  both  in- 
tensity and  quality  of  sensation  ;  the  oboe  is  characterised  by 
the  ease  and  wide  range  of  its  movement  over  the  intensive 
scale ;  the  organ  tone  within  a  given  register  is  incapable  of 
intensive  fluctuation,  etc.,  etc. 

(6)  A  good  many  instruments  have  characteristic  tasks 
(melodic,  rhythmical,  harmonic)  set  them,  whether  by  the  rules 
of  their  physical  construction  or  by  musical  tradition.  Flute 
and  piano  are  characterised  by  certain  trills  and  runs ;  the 
trumpet  by  a  certain  rhythmical  figure ;  the  violin  by  its  in- 
ability to  give  more  than  two  clangs  with  exact  simultaneity ; 
the  harp  by  its  arpeggio  chords,  etc.,  etc.  All  these  facts  assist 
us,  if  we  know  approximately  the  composition  of  an  orchestra, 
to  refer  the  various  clangs  to  their  respective  instruments. 

A  good  instance  of  the  value  of  the  secondary  constituents  in 
clang-tint  is  afforded  by  the  following  experiment.  Take  a 
stopped  organ-pipe  and  a  tuning-fork,  mounted  on  its  resonance- 
box,  of  the  same  pitch,  say,  c^.  O  shuts  his  eyes ;  E  sounds 
the  two  instruments,  as  evenly  as  possible,  the  fork  by  striking 
with  a  felt  hammer,  the  pipe  by  blowing.  So  long  as  O  is  near 
enough  to  E  to  hear  the  thud  of  the  hammer  and  the  push  of 
the  wind  in  the  pipe  (concomitant  noises),  and  to  note  the 
manner  in  which  the  two  sounds  arise  (temporal  differences),  he 
has  not  the  least  difficulty  in  ascribing  each  clang  to  its  right 
source.  If,  however,  he  moves  a  few  metres  away,  so  that  the 
secondary  criteria  fail  him,  he  readily  confuses  the  two  stimuli. 

Experiment.  —  li  O  was  impressed  by  the  fact  that  the  tubes 
of  Exp.  VII.  gave  the  chromatic  scale  from^^  to^*,  and  knows 
how  to  apply  his  table  of  vibration-rates  to  the  piano,  he  will 
hardly  be  able  to  perform  the  first  step  of  the  experiment  with- 
out prejudice.  In  such  a  case,  it  will  be  better  to  substitute 
some  other  instrument  {e.g.y  sonometer)  for  the  piano.  The 
piano  may  then  be  brought  in  under  (5).  Note  that  the  range 
of  the  flute  does  not  as  a  rule  extend  beyond  the  g^. 

Again:  if  O  finds  the  successive  comparisons  of  (2)  too 
difficult, — though  this  will  rarely  happen  with  observers  who 


{  20.    Clang  Analysis:  Overtones  75 

possess  even  a  moderately  good  'musical  ear,'  —  a  simultaneous 
procedure  may  be  substituted  for  them.  Tube  and  whistle  are 
sounded  together,  and  the  piston  of  the  whistle  pushed  back  and 
forth  until  the  difference-tone  is  clearly  heard.  Then  the  direc- 
tion in  which  the  difference-tone  deepens  is  determined,  and  the 
piston  moved  in  that  direction  until  unison  is  reached.  The 
successive  comparisons  should  always  be  attempted  before 
recourse  is  had  to  the  alternative  method. 

Literature.  —  Helmholtz,  Sensations  of  Tone,  1895,  19,  21, 
66  ff..  118  f.,  127. 

Sanford,  Course,  1898,  64,  exp.  74. 

Stumpf,  Tonpsychologie,  i.,  235,  240,  426;  ii.,  406,  516-520. 


EXPERIMENT  DC 

§  20.  Clang  Analysis  :  Overtones.  —  Cautions  not  noted  in  the 
Text.  —  As  a  rule,  the  odd-numbered  partials  are  easier  to  hear 
than  the  even-numbered.  These  latter  are  octaves,  either  of  the 
fundamental  or  of  some  one  of  the  upper  partials  that  lies  near 
it.  Thus  the  second,  fourth  and  eighth  partials  are  higher 
octaves  of  the  fundamental ;  and  the  sixth  is  the  octave  of  the 
third  partial.  The  third  partial  is  the  twelfth  (octave  -f  fifth)  of 
the  fundamental ;  the  fifth  partial  lies  two  octaves  and  a  major 
third  above  it ;  the  seventh  partial  is  the  sub-minor  seventh  of 
the  octave  which  contains  the  fifth. 

Musically  trained  observers  can  *  imagine '  the  sound  of  the 
partial  which  is  to  be  heard  from  the  whole  note.  Unmusical 
persons  do  not  know  what  to  listen  for ;  and  it  is,  therefore,  im- 
portant that  they  shall  hear  the  partial  by  itself  (as  a  clang  of 
the  same  tint  as  the  clang  which  is  to  be  analysed)  before  the 
full  note  is  sounded. 

As  special  factors,  influencing  the  discrimination  of  partials, 
Stumpf  mentions  the  following,  (i)  Observation  at  night-time, 
when  the  nervous  disposition  is  more  favourable.  (2)  Concen- 
tration of  attention  upon  a  single  ear.  (3)  Turning  of  the  head, 
alteration  of  the  general  bodily  position,  movement  towards  or 
away  from  the  source  of  sound :  influences  depending  upon  the 
complicated  form  of  the  pinna,  or  the  acoustic  properties  of  the 


76  Audi  to  fy  Sensation 

room  in  which  the  experiments  are  made.  (4)  Extension  of 
the  pinna  by  the  hollowed  hand.  (5)  Choice  of  tones  in  the 
four-accented  octave  :  see  p.  66  above.  —  Tonpsychologie,  ii.,  236. 

On  the  physics  of  a  sounding  string,  see  Helmholtz,  45  f.  A  physical 
demonstration  may  be  turned  to  psychological  account,  as  follows,  (i)  Pluck 
the  string  in  the  middle.  The  even-numbered  partials  are  suppressed,  or  at 
least  greatly  weakened,  while  the  odd-numbered  sound ;  the  clang  is  hollow 
and  nasal.  (2)  Pluck  the  string  at  one-third  of  its  length.  The  odd-num- 
bered partials  disappear,  and  the  even-numbered  remain ;  the  clang  is  still 
thin,  but  better  than  before.  (3)  Pluck  the  string  at  one-seventh  of  its  length. 
The  first  six  partials  are  present ;  the  clang  is  full  and  rich.  —  Helmholtz,  76  ft 

If  the  laboratory  does  not  possess  a  monochord,  recourse  may  be  had  to 
a  piano  or  harmonium.  Both  instruments  have  upper  partials  of  relatively 
high  intensity.  It  should  be  noted,  however,  that  the  seventh  and  ninth 
partials  are  for  the  most  part  very  weak,  or  absent,  in  modern  pianos. 

Materials.  —  The  wire  of  the  sonometer  should  be  thin  and 
not  too  tightly  stretched.  If  the  instrument  is  tuned  too  sharp, 
the  higher  partials  become  difficult  of  recognition. 

Results.  —  Six  observers,  chosen  without  reference  to  musical 
training,  heard  the  third  partial  within  twenty  minutes  from  the 
beginning  of  the  experiment,  and  thereafter  heard  all  the  partials 
up  to  and  including  the  seventh.  Two,  who  had  had  more 
practice  in  acoustical  work,  reached  the  tenth  partial  without 
difficulty.  In  no  case  did  an  observer  fully  recognise  any  other 
partial  than  that  to  which  the  attention  was  especially  directed 
in  the  experiment,  though  the  two  last  mentioned  *felt'  that 
others  were  present,  and  said  that  they  should  miss  them  if 
absent. 

Helmholtz,  using  thin  strings  with  loud  upper  partials,  was 
"able  to  recognise  the  partials  separately,  up  to  the  sixteenth.'* 
A  musically  trained  observer,  whose  ear  is  practised  in  the  dis- 
crimination of  partials,  can  hear  the  intervals  and  chords  formed 
by  the  lower  overtones  :  thus  it  is  not  very  difficult  to  hear  the 
two  tones  e^  —  ^b^y  when  the  string  is  sounding  the  C.  Stumpf, 
Tonpsychologie,  ii.,  314;  Kulpe,  Outlines  of  Psychology,  302; 
Ebbinghaus,  Psychologic,  i.,  296. 

Methods  of  Observing  Partial  Tones,  i.  Resonators.  —  A  reso- 
nator is  a  hollow  chamber  (sphere,  cylinder,  cone)  of  glass  or 


)  20,    Overtones  yj 

metal,  funnel-shaped  at  the  one  end  for  insertion  into  the  ear, 
and  open  at  the  other  to  the  surrounding  air.  The  mass  of  air 
in  the  resonator,  together  with  that  in  the  ear-passage  and  the 
tympanic  membrane  itself,  forms  an  elastic  system,  capable  of 
vibrating  in  a  peculiar  manner,  />.,  to  a  particular  pitch.  If, 
then,  the  tone  to  which  the  resonator  is  tuned  be  sounded,  the 
air  within  it  is  thrown  into  powerful  sympathetic  vibration,  and 
the  tone  *  brays '  into  the  ear  very  forcibly.  Other  tones,  pro- 
duced in  the  surrounding  air,  are  considerably  damped.  More- 
over, the  masses  of  air  in  resonators  have  generally  only  very 
high  upper  partials,  chiefly  inharmonic  with  the  fundamental 
tone,  and  not  capable  of  any  great  reinforcement  by  the  reso- 
nator :  so  that,  for  all  practical  purposes,  the  instrument  picks 
out  its  own  proper  tone,  and  that  alone,  from  a  given  mass  of 
sound. 

There  are  three  principal  forms  of  resonators  in  general  use.  These  are 
the  spherical  resonators  of  Helmholtz,  the  cylindrical  resonators  of  Koenig, 
both  made  of  brass,  and  the  conical  resonators  of  Appunn,  made  of  thin 
sheet  zinc.  The  last  mentioned  are  cheap,  and  useful  for 
roost  purposes;  but  they  reinforce  all  the  partials  of  their 
fundamental  at  the  same  time.  The  Koenig  resonators  are 
made  of  two  short  cylinders,  the  one  fitting  into  the  other : 
the  outer  cylinder  has  a  lid  pierced  with  a  circular  opening, 
the  inner  is  drawn  into  a  funnel-shaped  tube.  One  reso- 
nator will  serve  to  reinforce  several  tones,  since  the  inner  cyl- 
inder can  be  drawn  partly  out  of  the  other,  and  the  contained 
air-space  thus  increased.  The  fundamentals  to  which  each 
resonator  will  *  speak'  are  marked  upon  the  inner  cylinder, 
in  French  notation.  A  full  set  consists  of  14  resonators, 
ranging  between  the  limits  of  C7,  =  48  and  c*  -  1024  vs. 

(Aj/,  =  96  v.  s.  to  Ut^  -  2048  V.  8.).     The  ear-tube  of  each    y\q  T y^  Komiff 

resonator  should  be  made  to  fit  snugly  in  the  ear-passage  by         Resonator. 
means  of  a  piece  of  rubber  tubing  slipped  over  the  metal,  or 
a  coat  of  sealing-wax  which  is  pressed  into  the  ear  while  still  warm  and  soft. 
It  is  unnecessary  to  plug  the  unused  ear.  —  Helmholtz,  43,  372. 

Experiments  may  be  performed  as  follows,  (i)  Sound  on 
the  piano,  harmonium  or  harmonical,  the  tone  to  which  a  reso- 
nator is  tuned.  Note  the  reinforcement  of  the  tone  when  the 
resonator  is  inserted  in  the  ear.  Shift  the  outer  cylinder  (in 
the  Kcenig  resonator)  slightly  to  and  fro,  until  the  maximum  of 


^S  Auditory  Sensation 

such  reinforcement  is  obtained:  this  is  necessary,  since  the 
resonator  and  the  instrument  may  not  be  in  perfect  accord. 
Now  strike  the  notes  on  either  side  of  the  resonator-tone.  Note 
that  these  tones  are  not  reinforced.  (2)  Lay  out  the  reso- 
nators, in  order,  upon  a  table.  Sound  the  note  to  which  the 
largest  resonator  is  tuned.  Then  test  this  same  note  with  all 
the  remaining  resonators.  It  is  best  that  E  should  strike  the 
note,  and  hand  the  resonators  in  irregular  order  to  O,  who  is 
blindfolded.  O  applies  and  withdraws  the  resonator,  some  few 
times,  for  2  sec.  periods,  and  then  declares  whether  or  not  its 
proper  tone  has  been  heard.  This  procedure  is  necessary  in  the 
case  of  partials  which  are  very  weak  in  comparison  with  the 
tones  which  accompany  them,  and  should  therefore  be  followed 
through  the  whole  experiment.  The  resonators  which  '  speak ' 
will  be  found  to  represent  the  series  of  upper  partials  that 
attend  the  fundamental  on  the  given  instrument.  The  sonom- 
eter serves  well  for  this  experiment.  (3)  O  takes  a  single 
resonator,  e.g.,  that  for  the  c^.  E  plays  successively  a  number 
of  notes  that  are  lower  in  the  scale  than  the  c^,  and  O  declares 
whether  or  not  the  resonator  *  speaks  '  to  them.  The  resonator 
tone  will  be  heard  whenever  a  note  is  struck  which  contains  the 
c^  as  an  upper  partial :  it  will  be  heard,  e.g.,  from  the  c^,  /,  c, 
A\>,  F,  A  C. 

It  should  be  noted  that  the  hearing-out  of  overtones  by  means  of  reso- 
nators is  not  an  exercise  in  psychological  analysis  of  the  same  kind  as  their 
discrimination  by  the  unaided  ear.  The  tonal  material  under  investigation  is 
changed  by  the  introduction  of  the  resonator ;  some  one  of  the  partial  tones 
is  intensified,  while  the  remainder  are  damped.  Nevertheless,  work  with 
resonators  forms  good  preliminary  practice  for  the  experiment  of  the  text. 

ii.  Sympathetic  Vibrations  of  Strings. — (4)  Press  down  the 
^-key  of  the  piano,  slowly  and  gently,  so  that  the  hammer  does 
not  strike ;  and  hold  it  down,  so  that  the  ^-strings  are  free  to 
vibrate.  Now  strike  the  ^'-key ;  let  the  note  sound  out  loudly, 
and  after  2  sec.  damp  it  by  releasing  the  key.  The  c  is  dis- 
tinctly heard.  Repeat  the  experiment  with  a  number  of  keys 
chosen  between  the  C  and  the  c^.  The  g,  c^,  e^,  g^  and  c'^  may 
all  be  heard,  though  in  decreasing  intensity.  (5)  Press  down 
the  (T^-key,  as  the  c-key  was  pressed  in  the  previous  experi- 


§  2a     Ofrrfiittrs  79 

ment.  Play  in  succession  (and  immediately  damp)  the  notes 
r,  Ft  C  Afi,  Fy  Dy  C^ ;  <:*,  ^\  <^.  Note  that  the  t*  sounds  in 
every  case. 

On  the  mechanical  proof  of  sympathetic  vibration  of  the  piano  strings,  see 
Hehnholtz,  47. 

iii.  Beats. — (6)  This  experiment  is  best  performed  on  the 
harmonium  or  harmonica].  "  Keep  down  the  note  C  and  touch 
in  succession  the  notes  r,  ^,  r*,  r*,  £^\  etc. ;  but  in  touching  the 
latter  press  the  finger-key  such  a  little  way  down  that  the  note 
is  only  just  audible.  This  slightly  flattens  each  note,  and  slow 
beats  can  be  produced  "  (Ellis)  between  the  partial  contained 
in  the  C  and  the  flattened  note  of  the  reed  whose  fundamental 
is  the  partial  in  question.  Verify  by  sounding  other  notes  than 
those  of  the  upper  C-partials,  and  observing  that  the  beats  (when 
present)  are  much  quicker.  —  Helmholtz,  22. 

iv.  Direct  Analysis  by  the  Ear. — This  is  the  method  ex- 
plained in  the  text.  A  number  of  subsidiary  experiments  may 
be  added  here.  (7)  "To  the  objection  which  is  sometimes 
made  that  the  observer  only  imagines  he  hears  the  partial  tone 
in  the  compound,  because  he  has  just  heard  it  by  itself,"  it  may 
be  replied  "  that  if  c^  is  first  heard  as  a  partial  tone  of  ^  on  a 
good  piano,  tuned  in  equal  temperament,  and  then  ^  is  struck 
on  the  instrument  itself,  it  is  quite  easy  to  perceive  that  the  lat- 
ter is  a  little  sharper.  This  follows  from  the  method  of  tuning. 
[The  partials  are  not  only  heard  as  simple  tones ;  they  are 
also  heard  always  in  just  temperament.  The  ^  as  overtone  has 
a  pitch  number  of  660 ;  the  e^  of  the  piano  a  pitch  number  of 
665.3.]  But  if  there  is  a  difference  of  pitch  between  the  two 
tones,  one  is  certainly  not  a  continuation  of  the  mental  effect 
produced  by  the  other"  (Helmholtz,  50).  (8)  The  upper  par- 
tials contained  in  the  human  voice  may  be  heard  as  follows. 
"Let  a  powerful  bass  voice  sing  ^  to  the  vowel  O  in  sore; 
gently  touch  ^*b  on  the  piano,  .  .  .  and  let  its  sound  die  away 
while  you  are  listening  to  it  attentively.  The  note  b^  on  the 
piano  will  appear  really  not  to  die  away,  but  to  keep  on  sound- 
ing, even  when  the  string  is  damped  by  removing  the  finger 
from  the  digital,  because  the  ear  unconsciously  passes  from  the 


8o  Auditory  Sensation 

tone  of  the  piano  to  the  partial  tone  of  the  same  pitch  produced 
by  the  singer,  and  takes  the  latter  for  a  continuation  of  the 
former.  But  when  the  finger  is  removed  from  the  key,  and 
the  damper  has  fallen,  it  is  of  course  impossible  that  the  tone  of 
the  string  should  have  continued  sounding.  To  make  the  ex- 
periment for  ^^,  .  .  .  the  voice  should  sing  to  the  vowel  A  in 
father''  (Helmholtz,  51).  (9)  If  a  tuning-fork  tone  is  allowed 
to  die  away,  the  pitch  of  the  tone  seems  slowly  to  rise ;  the 
overtones  disappear  more  slowly  than  the  fundamental.  If  a 
low  note  on  the  piano  keyboard  is  struck,  and  the  key  held 
down  while  the  tone  dies  away,  the  upper  partials  ring  out,  in 
irregular  order,  as  the  tone  weakens.  Something  similar  may 
be  observed  on  the  sonometer,  and  on  the  harmonium,  if  a  low 
reed  is  sounded  and  the  air  allowed  gradually  to  escape  from  the 
bellows.  —  Stumpf,  i.,  242;  ii.,  237.  (10)  Clamp  down  a  low 
key  on  the  harmonical  keyboard,  and  keep  the  note  sounding 
for  some  time,  —  Mach  speaks  of  half  an  hour,  but  ten  minutes 
will  probably  suffice.  Different  partials  ring  out  successively 
from  the  mass  of  sound  (E.  Mach,  Grundlinien  der  Lehre  von 
den  Bewegungsempfindungen,  1875,  58  ;  Analyse  der  Empfin- 
dungen,  1886,   127). 

Literature.  —  Helmholtz,  Sensations  of  Tone,  36-65 ; 
Stumpf,  Ton  psychologic,  ii.,  231-243;  Sanford,  Course,  73  ff., 
Exps.  86-89. 

Acoustic  Instruments. — The  laboratory  should  possess  a 
set  of  Koenig  forks  (12  forks,  Fr.  485);  a  set  of  resonators 
(14,  Fr.  380) ;  an  Ellis  harmonical  (see  p.  52  above) ;  an  Appunn 
tonometer  (Mk.  350)  with  bellows  table  (Mk.  120) ;  and  a  Koenig 
sonometer  (Fr.  112). 


CHAPTER   III 

Cutaneous  Sensation 

§  21.  CntaneoTU  Sensation.  —  investigation  of  the  cutaneous 
sensations  has  moved  so  rapidly  during  the  past  five  years  that 
there  is  no  adequate  account  of  them  to  be  found  in  the  text- 
books. Kiilpe's  sections  (Outlines  of  Psychology,  1895,  87,  92) 
are  already  out  of  date.  The  experiments  that  follow  emphasise 
the  principal  points  in  the  sense  psychology  of  the  skin ;  but  they 
should  be  supplemented  by  lectures  on  the  basis  of  the  mono- 
graph literature. 

The  student  may  presently  be  asked  to  analyse  the  perceptions 
of  impact,  resistance,  etc.  See  Titchener,  Outline  of  Psych., 
1899,  64  f. ;  Helmholtz,  Sensations  of  Tone,  1895,  63. 

Preliminary  Exercises.  —  The  temperature  experiment  was 
suggested  by  John  Locke  (1632-1704).  See  An  Essay  concern- 
ing Human  Understanding,  Bk.  ii.,  ch.  8,  §  21. 

A  pretty  variation  of  the  pressure  experiment  is  this.  Get  a 
number  of  similar  corks,  and  cover  the  lower  surfaces  with  sub- 
stances of  varying  roughness :  plush,  velvet,  flannel,  buckram, 
perforated  tin  (overlaid  with  tissue  paper,  to  avoid  the  tempera- 
ture effect),  hard  and  soft  wood,  etc.,  etc.  Set  the  corks  down 
gently  and  evenly  upon  the  skin,  and  let  O  try  to  identify  or 
describe  the  pressing  surfaces.  The  experiment  brings  out  our 
extreme  dependence  upon  active  pressure  (touch),  as  well  as  the 
fact  of  adaptation. 

Questions. — (i)  See  Hering,  in  Hermann's  Hdbch.  d. 
Physiol.,  iil,  2,  1880,  419  ff . ;  Kiilpe,  Outlines,  95.  The 
materials  for  criticism  are  furnished  by  Exp.  X. 

(2)  In  all  probability,  the  free  nerve  endings  of  the  epidermis 
are  the  pain  organs ;  Krause's  end-bulbs,  the  organs  of  cold ; 
Ruffini's  cylinders,  the  organs  of  warmth ;  and  the  hair-bulbs  and 
Meissner's  corpuscles,  the  organs  of  pressure.  See  M.  von  Prey, 
Ber.  d.  kgl.  sachs.  Ges.  d.  Wiss.,  March  4,  1895,  180  ff. 
G  81 


82  Cutaneous  Sensation 

On  cutaneous  sensations,  see  Wundt,  Phys.  Psych.,  i.,  1893, 
410;  O.  Funke  and  E.  Hering,  in  Hermann's  Hdbch.  d.  Physiol, 
iil,  2,  1880,  289,  415;  Stout,  Manual,  186;  Titchener,  Outline, 
63,  73;  A.  Goldscheider,  Gesammelte  Abhandlungen,  i.,  1898; 
Foster,  Text-book  of  Physiol.,  iv.,  1891,  141 2.  The  experimental 
literature  begins  with  the  monograph  of  E.  H.  Weber,  Der  Tast- 
sinn  und  das  Gemeingefiihl,  published  in  R.  Wagner's  Hand- 
worterbuch  d.  Physiol,  iil,  2,  1846,  481. 

EXPERIMENT  X 

§  22.  Temperature  Spots.  Cautions  not  noted  in  the  Text.  — 
If  the  students  are  entirely  ignorant  of  the  nature  of  isolated 
temperature  sensations,  it  will  be  well  to  preface  the  experiment 
by  a  few  rough  trials.  A  blunt  pencil-point  drawn  slowly  over 
the  back  of  the  hand  will  give  rise  to  several  flashes  of  cold. 
The  warm  spots  are  more  difficult  of  identification  than  the  cold 
spots  :  trials  may  be  made  with  the  heated  cylinder  upon  the  eye- 
lids. Care  must  be  taken  that  there  is  no  scratching  of  the  skin 
by  the  point  of  the  cylinder.  Where  necessary,  the  point  should 
be  rubbed  gently  upon  fine  emery  paper  until  it  is  sufficiently 
rounded.  The  dyes  are  a  little  difficult  to  manage,  at  first.  The 
solution  soon  dries  on  the  brush,  and  a  blot  of  colour  may  be 
made  where  the  dot  is  wanted.  The  solution  must  be  kept  quite 
weak,  and  the  brushes  frequently  dipped  in  water.  Sometimes, 
again,  the  nitrate  of  silver  in  the  indelible  ink  sets  up  an  inflam- 
mation of  the  skin.  If  this  is  at  all  troublesome,  the  margins 
of  the  marked  area  may  be  left  unexplored.  If  the  skin  proves 
to  be  extremely  sensitive,  the  four  corners  of  the  area  may  be 
marked  by  dots,  and  the  side-lines  drawn  in  dye  (brown,  e.g.\ 
More  care  is  then  needed  to  ensure  accurate  localisation  of  the 
temperature  spots  in  the  two  maps. 

No  attempt  must  be  made,  during  a  single  sitting,  to  verify 
the  spots  once  found ;  fatigue  is  inevitable,  and  confusion  and 
self-distrust  result.  Errors  are  apt  to  be  made  in  localisation, 
by  the  fact  that  approach  to  a  cold  or  warm  spot  will  set  up  a 
weakly  cold  or  warm  sensation.  Even  after  repeated  cautions, 
a  student  is  likely  to  enter  this  approximation-sensation  in  his 
maps  rather  than  the  more  intensive  sensation  which  he  can 


{  22.    Temperature  Spots 


83 


obtain  by  moving  the  cylinder  a  little  farther,  until  it  lies  exactly 
over  the  temperature  spot.  The  Instructor  will  then  be  called 
upon  to  decide  whether  two  spots,  lying  close  together  in  the 
two  preliminary  maps,  are  to  be  entered  in  the  third,  final  map 
as  one  or  two.  The  question  can  generally  be  settled  by  notic- 
ing the  relative  positions  of  the  spots.  Thus,  when  the  area  has 
been  worked  over  in  the  RL  and  PC  directions,  the  spots,  if 
really  one.  will  lie  too  far  to  the  R  and  too  far  P,  respectively : 
should  the  PC  spot  lie  C  of  the  RL  spot,  or  the  RL  spot  lie  to 
the  L  of  the  PC  spot,  the  presumption  is  that  the  marks  belong 
to  two  distinct  sense-organs.  The  general  accuracy  of  the  stu- 
dent's work  must  also  be  taken  into  account.  In  cases  of  doubt, 
the  Instructor  himself,  not  E,  should  make  a  special  test  to  deter- 
mine the  matter.  The  best  rate  of  movement  and  degree  of 
pressure  vary  somewhat  from  individual  to  individual.  They 
must  be  learned  by  practice. 

Practice,  indeed,  on  the  part  both  of  E  and  of  Oy  is  the  chief 
condition  of  successful  work  in  this  experiment.  It  is  hardly 
possible,  in  a  drill  Course,  to  give  the  stu- 
dent time  enough  for  really  thorough  prac- 
tice. Hence  if,  say,  two-thirds  of  the  spots 
first  found  are  verified  at  the  second  sitting, 
and  if  this  sitting  leads  to  the  discovery  of 
a  fair  number  of  new  spots,  the  Instructor 
may  be  well  satisfied.  The  main  thing  is  to 
convince  the  student  that  the  spots  are  not 
artifacts,  products  of  imagination,  and  to 
afford  him  opportunity  for  introspection. 

For  the  temperatures  to  be  employed  if  this  experi- 
ment is  more  accurately  performed,  see  Pt.  i.,  p.  57. 
The  Instructor  will  find,  however,  that  all  the  intro- 
spective points  raised  in  the  text  can  be  brought  out 
by  the  rough  method  here  recommended.  Even  as  it 
is,  the  experiment  is  likely  to  run  to  undue  length ; 
and  work  with  constant  temperatures  demands  a  pro- 
portionately much  longer  time. 

Fig.  5  shows  a  device  for  keeping  water  at  a  con- 
stant warmth.    A  copper  vessel  is  fitted  with  a  Roux  regulator  and  thermom- 
eter, and  heated  by  Friedburg  burners  connected  with  the  gas  supply.    The 


Fig.  5. 


84 


Cutaneous  Sensation 


temperature  will  remain  constant  to  .1°,  within  the  limits  and  for  the  time 
required. 

A  good  instrument  of  the  Blix  pattern  (mixed  warm  and  cold  water  flowing 
in  a  pointed  tube)  is  made  after  J.  McK.  Cattell's  design  by  the  mechanician 
of  the  Columbia  Univ.  Laboratory.  Instruments  can  also  be  obtained  in  which 
a  platinum  point  is  warmed  by  electrical  means. 


Questions.  —  -£"(1)  The  cold  spots  are  the  more  numerous. 
The  type  of  arrangement  of  both  spots  is  the  same.  We  find 
(a)  groups  or  clusters  of  spots, — small  areas  of  temperature,  as  it 
were.  These  are  commoner  for  cold  spots  than  for  warm.  In 
the  case  of  cold,  though  never  in  that  of  warm,  these  areas  are 
sometimes  unanalysable  into  discrete  spots.  We  find  {b)  curves 
or  chains  of  spots.  These  are  sometimes  of  the  same  quality 
throughout,  sometimes  of  intermingled  cold  and  warm  spots. 
Often  they  enclose  small,  irregularly-shaped,  insensitive  areas. 
(c)  We  find  isolated  spots. 

The  dots  for  the  warm  spots  should  be  larger,  since  the  area 
of  radiation  is  sensibly  greater  in  the  case  of  the  warm  sensation 
than  it  is  in  that  of  the  cold. 

E  (2)  The  intensive.  —  Emphasise  the  fact  that  the  spots  are 
not  all  equally  sensitive,  but  are  'tuned'  or  adjusted  to  respond 

A  to  a  given  stimulation  by  sensations  of 

^^  varying  intensity.  Verify  it  by  experi- 
ments  made  at  known  spots,  if  there 
is  any  doubt  of  it  in  the  student's 
mind. 

6^  (3)  The  cold  sensation  is  localised 
more  superficially  than  the  warm.  The 
cold  is  more  restricted,  less  extended, 
than  the  warm.  The  cold  seems  to 
lance  down,  from  above;  the  warm 
seems,  oftentimes,  to  well  up,  from 
beneath.  The  cold  is  set  up  at  once,  in  a  moment;  the  warm 
comes  gradually  to  its  full  intensive  development.  The  cold 
is  continuous,  all  of  a  piece,  a  solid  point  of  cold;  the  warm 
is  at  times  discontinuous,  bubbly  or  fizzling,  a  number  of  spurts 
of  warmth. 

O  (4)   It  is  probable  that  pressure  was  involved  in  every  case. 


Fig.  6.  —  Blix'  apparatus  for 
the  investigation  of  the  tem- 
perature sense.  C  =  cold, 
W^=warm  water;  /*=  metal 
point. 


§  22.    Ttmptrature  Spots  85 

The  instrument  used  is  not  delicate  enough  to  allow  of  complete 
isolation  of  the  temperature  spots. 

E  and  O  (l)  It  would  be  well  to  determine  ( i )  the  nature  and 
number  of  the  spots  over  the  corresponding  area  of  the  right 
hand.  The  distribution  of  the  spots  might  also  (2)  be  tested  at 
different  parts  of  the  body.  Are  the  more  peripheral  parts,  e.g., 
more  or  less  richly  endowed  with  temperature  organs  than  the 
trunk .^  Do  dorsal  and  volar  surfaces  differ?  How  does  the 
median  line  of  the  body  compare  with  the  lateral  parts? 
These  and  similar  problems  may  be  worked  out  by  the  stu- 
dent, as  time  permits. 

Related  Experiments,  (i)  Mechanical  Stimulation  of 
Temperature  Spots.  —  Localise,  by  aid  of  one  of  the  preliminary 
maps,  an  intensive  cold  spot.  Pull  the  skin  taut  by  finger  and 
thumb.  Tap  it,  at  first  lightly  and  then  by  degrees  more  and 
more  strongly,  with  the  pressure  spot  apparatus  of  Exp.  XII. 
If  you  find  the  right  intensity  of  tapping,  the  sensation  of  cold 
will  flash  out,  as  it  does  in  response  to  the  cooled  cylinder.  — 
Perform  the  same  experiment  with  a  warm  spot.  The  same 
result  can  be  obtained,  though  with  greater  difficulty. 

(2)  Analgesia  of  the  Temperature  Spots.  —  Localise  an  inten- 
sive cold  spot.  Soften  the  skin  by  rubbing  it  with  soapy  water. 
Stretch  it  taut.  Thrust  the  point  of  a  very  fine  needle,  pre- 
viously warmed  between  finger  and  thumb,  down  into  the  spot. 
You  will  find,  probably  in  four  or  five  cases  out  of  ten,  that  you 
get  a  sensation  of  cold  entirely  free  from  the  pricking  pain  which 
the  stimulus  sets  up  at  neighbouring  parts  of  the  skin.  The  cold 
spots  are  analgesic  ;  but  as  often  as  not,  —  perhaps  rather  more 
often  than  not,  —  you  will  strike  a  pain  spot  at  the  same  time 
that  you  hit  the  temperature  spot.  Perform  the  same  experi- 
ment, with  a  cooled  needle,  at  a  well-defined  warm  spot. 

(3)  Inadequate  Thermal  Stimulation.  —  The  O  of  the  experi- 
.ment  described  in  the  text  may  have  noticed  (a)  that  sometimes, 
when  cold  spots  were  being  sought,  but  the  cooled  cylinder  had 
been  too  long  in  use,  had  been  inadvertently  held  in  the  warm 
fingers,  or  what  not,  a  warm  sensation  welled  up  under  its  touch ; 
(p)  that  sometimes,  when  warm  spots  were  being  sought,  and  the 


S6  Cutaneous  Sensation 

heated  cylinder  was  a  little  over-hot,  a  co/d  sensation  flashed  out  ; 
and  (c)  that  sometimes,  when  warm  spots  were  being  sought,  but 
the  heated  cylinder  had  been  too  long  in  use,  a  co/(/  sensation 
was  produced.  The  first  and  third  of  these  experiences  are  the 
result  of  carelessness.  The  second,  however,  is  extremely  inter- 
esting, and  raises  the  general  question  whether  we  can  make  a 
cold  spot  respond  by  cold  to  a  warm  stimulus,  and  a  warm  spot 
respond  by  warm  to  a  cold  stimulus. 

The  facts  seem  to  be  as  follows,  (a)  Normally,  the  warm 
spot  replies  only  to  the  warm  stimulus,  by  a  sensation  of  warmth ; 
the  cold  spot  replies  only  to  the  cold  stimulus,  by  a  sensation  of 
cold,  (d)  There  is,  however,  a  'paradoxical'  cold  sensation  (von 
Frey).  Localise  an  intensive  cold  spot,  and  stimulate  it  by  a 
metal  point  heated  to  4$°  C.  or  over.  It  responds  by  an  instan- 
taneous sharply  defined  cold  sensation.  At  certain  parts  of  the 
body,  parts  which  have  a  highly  developed  cold  sense  and  little 
sensitivity  to  warmth,  the  paradoxical  cold  sensations  form  a 
serious  obstacle  to  the  mapping  of  the  warm  spots.  Oftentimes 
the  sensation  is  obtained  most  clearly  not  from  the  skin  directly 
over  the  marked  spot,  but  from  points  lying  immediately  adja- 
cent to  the  mark.  No  explanation  is  at  present  possible.  C/., 
however,  the  momentary  chill  experienced  on  plunging  into  a 
hot  bath,  (c)  There  is  no  paradoxical  warm  sensation.  Or,  at 
least,  no  such  sensation  is  mentioned  in  the  literature;  and  the 
author,  in  a  very  large  number  of  experiments,  has  invariably 
failed  to  evoke  a  warm  sensation  from  a  warm  spot  by  the  appli- 
cation of  a  cold  point,  (d)  A  warm  spot  never  responds  to  the 
cold  cylinder  by  a  cold  sensation.  Kiesow  has  worked  with  tem- 
peratures as  low  as  — 6°  C,  with  this  result;  and  the  author's 
experiments  fully  bear  it  out.  (e)  A  cold  spot  never  responds 
to  the  heated  cylinder  by  warmth.  Kiesow's  statement  that  he 
has  hardly  ever  found  a  cold  spot  that  would  not  reply  to  stimu- 
lation of  47°-5o°  C.  by  a  sensation  of  warmth  is  a  misreading 
of  the  facts.  In  reality,  radiation  occurred,  and  the  process 
observed  was  not  that  of  warmth,  but  of  heat  (see  Exp.  XL, 
p.  90). 

Literature.  —  The  temperature  spots  were  discovered  inde- 
pendently by  M.  Blix  (Upsala  Lakareforenings  Forhandlingar, 


$  23.    Temperaiure:  Artal  Sensitivity  87 

1883;  Zeits.  f.  Biologic,  XX.,  1884,  140);  H.  H.  Donaldson  (Mind, 
O.  S.,  X.,  1885,  399);  and  A.  Goldscheider  (Arch.  f.  [Anat.  u.] 
Physiol.,  Suppl.,  1885).  Goldscheider*s  paper  is  the  longest  and 
most  systematic :  it  is  published  in  his  Gesammelte  Abhand- 
lungen,  i.,  1898,  107;  cf,  also  pp.  53,  94,  100,  275,  301. 

Reference  may  also  be  made  to  papers  by  F.  Kiesow  (Philos. 
Studien,  xi.,  1885,  135;  xiv.,  1898,  589)  and  J.  F.  Crawford 
(Psych.  Rev.,  v.,  1898,  63).  For  the  paradoxical  cold  sensation, 
see  M.  von  Frey,  Ber.  d.  math.-phys.  Classe  d.  kgl.  sachs.  Ges. 
d.  Wissensch.  zu  Leipzig,  March  4,  1895,  172. 

EXPERIMENT  XI 

$  23.  Temperature  Sensitiyity  :  Areal  Stimiilation.  Cautions  not 
noted  in  the  Text.  —  The  student  should  be  made  clearly  to 
understand  that  the  previous  experiment  aimed  to  determine  the 
number  and  nature  of  the  temperature  organs  lying  within  a 
given  area,  whereas  the  present  experiment  seeks  to  determine 
the  sensitivity  (manner  of  functioning)  of  the  temperature  sense 
over  a  given  area. 

It  will  be  well  to  have  a  few  preliminary  trials  made,  say,  on 
the  palm  of  the  hand,  in  order  to  accustom  the  student  to  the 
meaning  of  the  three  categories  'intensely  cold,*  'cold,'  'just 
cold/  etc.  '  Cold '  means  distinctly,  unmistakably,  definitely  cold ; 
'intensely  cold '  means  surprisingly,  unusually,  even  unpleasantly 
cold;  'just  cold*  means  'cold,  if  anything,'  'perhaps  a  little 
cool*  '  Warm '  means,  in  the  same  way,  unmistakably,  clearly 
warm  ;  'just  warm  *  means  '  warm,  if  anything,'  '  perhaps  a  little 
lukewarm  * ;  *  intensely  warm  '  means  glowingly,  impressively,  or 
surprisingly  warm.  Note  that  the  perception  of  heat  cannot 
be  obtained  from  a  stimulus  of  the  temperature  employed  {cf. 
Related  Exp.,  below).  A  very  little  practice  will  suffice  to 
render  introspection  accurate. 

If  possible,  the  experiment  should  be  performed  three  times 
over,  at  intervals  of  about  a  week.  The  results  of  the  first  per- 
formance are  likely  to  be  unreliable,  from  the  fact  that  the 
student  does  not  notice  differences  of  sensitivity  within  the  area 
of  the  stimulus,  until  his  attention  has  been  called  to  their  possi- 
bility by  questioning. 


88 


Cittaneous  Sensation 


3    j 

2 

(.^ 

4 

3 

1 

3  ^ 

CO 

(z 

3 

r  2  ^ 

C  ^ 

-7- 

CO 

( ^ 

3 

2 

3 

4 

2 

2 

CO 

C 1 

3 

:■ 

[2 

(  ® 

CO 

(3 

jTs 

Fig.  7. 


Specimen  of  Results,  —  Fig.  7  shows  two  *  cold  '  maps,  taken 

from  a  wholly  unpractised  but  attentive  (9,  at  an  interval  of  a 

week.  Four  degrees  of  cold  are 
here  recorded  :  4,  very  intensely 
cold  ;  3,  strongly  cold  ;  2,  mod- 
erately cold;  I,  weakly  or  just 
barely  cold.  It  will  be  seen  that 
only  in  one  case  is  there  any 
material  discrepancy  between 
the  introspections.  It  is,  how- 
ever, better  to  reduce  the  four 
degrees  to  three. 

Fig.  8  is  a  final  *  cold '  map. 

The  black  areas  are  those  of  very  intense  cold  ;   the  lined  areas 

those  of  strong  cold  ;  the  dotted  areas  those  of  moderate  cold  ; 

and  the  white  areas  those  of  weak  or 

just  noticeable  coolness.     The  value  of 

such  a  map  depends,  of  course,  upon 

the    constancy    with    which    the    areas 

reappear  in  subsequent  tests.     For  an 

attentive  and  honest  O,  this  constancy 

is  practically  absolute. 

Questions.  —  O  (i)  It  is  a  general 

rule  that  the  introspection  of  sensation 

intensities   is    more  difficult  than  that 

of  sensation  qualities.    The  former  is  a 

comparative  or  relative    introspection : 

the  intensity  is  always  a  *  stronger '  or 

a  *  weaker ' ;   the  latter  is  an  absolute 

introspection :  a  quality  is  a  *  this '  or 

a 'that.*     In  accordance  with  this  rule, 

the  present  experiment   should  be  the 

more  difficult.     More  especially  would  this  be  the  case,  if  O  had 

found  the  differences  within  the  stimulus  circle  referred  to  in 

Question  (3). 

On  the  other  hand,  the  degrees  of  intensity,  introspection  of 

which  is  here  called  for,  are  so  chosen  as  to  render  the  introspec- 
tion as  easy  as  possible.     Moreover,  the  student  is  not  accus- 


FiG.  8,  —  /*,  peripheral;  C, 
central;  U,  ulnar;  R,  ra- 
dial. 


§  23-    Tnmperature:  Area!  Sensitivity  89 

tomed  to  the  determination  of  punctiform  sensation  qualities ; 
and  so  may  have  found  the  preceding  experiment  difficult. 
Hence,  if  the  differences  of  Question  (3)  have  not  been  remarked, 
the  present  experiment  may  be  given  as  the  easier. 

The  'reasons  for  the  answer'  are,  obviously,  of  much  greater 
psychological  importance  than  the  answer  itself. 

E  {2)  Yes.  Sensitivity  to  cold  has  a  greater  range,  inten- 
sively and  extensively,  than  sensitivity  to  warmth.  Note  the 
fact  that  high  intensity  values  are  commoner  for  cold,  and  that 

sensitive  areas  occur  more  frequently  and  in  greater  extent 
hen  the  skin  is  being  tested  for  warmth.  Further:  if  the 
Ao  final  maps  be  laid  over  one  another,  or  viewed  in  a  stereo- 
scope, it  will  be  found  that  the  areas  sensitive  to  warmth  and 
cold  partially  overlap  {cf.  the  mixed  chains  of  the  last  experi- 
ment). And  certain  irregularly-shaped  areas  will  be  found  to 
show  insensitivity  to  both  forms  of  stimulus. 

O  (3)  Oftentimes  there  are  differences,  though  their  intro- 
spective demarcation  is  not  easy.  Occasionally,  however,  a  region 
of  best  sensitivity  borders  directly  upon  a  region  of  insensitivity. 

E  and  O  (4)  This  question  is  best  answered  by  the  counter- 
question  :  Is  the  skin,  under  the  conditions  of  stimulation  found 
in  ever)'day  life,  a  mosaic  of  sensitive  and  insensitive  parts }  Is 
it  not  rather  a  continuously  sensitive  organ  } 

It  is  true  that,  under  experimental  conditions  of  extreme  re- 
finement, two  adjacent  cold  or  warm  spots  will  give  rise,  when 
simultaneously  stimulated,  to  two  distinct  sensations.  But  in 
ordinary  life  the  sense  organs  do  not  receive  such  delicate  stim- 
ulation. For  the  most  part,  temperature  stimuli  come  from 
extended  surfaces.  Now  we  have  found,  in  our  own  experi- 
menting, that  there  is  an  'approximation  sensation '  of  tempera- 
♦ire  ;  the  neighbourhood  of  the  sensitive  spot  is  itself  sensitive  ; 
;ie  sensation  radiates  from  the  end-organ  over  a  certain  area  of 
the  surrounding  skin.  We  must  suppose,  then,  that  areal  stim- 
ulation really  calls  forth  an  area  (not  a  mosaic)  of  sensation. 
We  might,  perhaps,  expect  to  find  intensive  differences  within 
this  area,  since  the  approximation  sensation  is  weaker  than  the 
spot  sensation ;  but  the  cognition  of  small  intensive  differences 
is    difficult,  and    these    may  well  he  subliminal. — The    retinal 


90  Cutaneous  Sensation 

mosaic  of  rods  and  cones  would  thus  afford  a  good  analogy.  Cf. 
also  the  mosaic  of  pressure  spots. 

There  is  one  fact,  easily  verified  by  experiment,  that  calls  for 
special  explanation  in  this  connection.  It  is  this :  if  the  stimu- 
lated skin  area  have  a  very  few  intensive  spots  and  a  greater 
number  of  weakly  sensitive  spots  upon  it,  it  is  always  regarded 
by  O  as  an  area  of  intense  sensitivity  ;  the  few  good  spots  give 
a  character  to  the  whole  area.  We  must  suppose,  in  this  case, 
that  the  weak  sensations,  though  they  do  not  come  to  conscious- 
ness as  special  temperature  sensations,  nevertheless  form  the 
basis  of  O's  judgment  of  continuity.  They  give  the  attribute  of 
area  (unbroken  continuity)  to  the  total  temperature  sensation, 
just  as  the  few  intensive  sensations  give  the  total  sensation  its 
intensity.  — 

If  we  are  not  satisfied  with  this  '  summation '  theory,  we  may 
have  recourse  to  a  subsidiary  hypothesis.  We  may  suppose 
that  the  gaps  in  sensation  are  filled  out  by  association.  We  see, 
t.e.y  that  the  stimulus  presents  an  unbroken  surface ;  and  we 
carry  over  this  continuity,  by  visual  association,  to  the  skin. 
Cf.  the  filling-out  of  the  blind  spot  of  the  retina. 

Related  Experiments.  —  The  Perception  of  Heat. — We 
have  seen  that  the  cold  spots  respond  by  a  sensation  of  cold 
to  intensive  inadequate  thermal  stimulation  (stimulation  by  a 
warmed  point  of  45°-50^  C).  What  happens  when  the  skin  is 
subjected  to  areal  stimulation  of  a  temperature  of  45°  C.  or 
over,  —  i.e.,  when  the  warm  spots  of  the  area  give  warmth,  and 
the  cold  spots  cold,  in  sensation  }  How  do  the  two  tempera- 
ture qualities  mix  }  It  responds  by  a  new  temperature  quality  : 
the  quality  of  heat.  Heat  is  a  fusion  or  mixture  of  warm  and 
cold. 

The  student  must  first  assure  himself  of  the  existence  and 
nature  of  the  hot  perception.  It  can  be  obtained  from  the  skin 
of  the  arm  over  the  elbow  joint  (volar  surface),  at  a  temperature 
of  45°-48°  C. ;  on  the  forehead  (upper  portion,  centre),  at 
48^-50°  C.  ;  and  on  the  mamilla  at  as  low  a  temperature  as 
40°  or  41°  C.  It  must  be  carefully  distinguished,  in  introspec- 
tion, from  the  sensations  of  warmth  and  of  pain.  It  differs  from 
both  in  quality.     It  may  further  be  distinguished  from  warmth 


§  23.    Temperature:  Areal  Sensitivity  91 

by  the  facts  (i)  that  it  is  less  diffuse,  nv^r,»  r.^ncentrated,  and 
(2)  that  it  is  localised  more  deeply. 

To  prove  that  the  heat  perception  is  really  a  fusion  of  cold  and 
warm  sensations,  the  following  tests  may  be  made,  {a)  Find  a 
place  upon  the  skin  which  has  cold  but  not  warm  spots.  Here, 
nothing  but  cold  and  pain  are  obtainable  from  stimulation  with 
high  temperatures,  {b)  Find  a  patch  of  skin  that  has  warm  but 
not  cold  spots.  Here,  nothing  but  the  familiar,  diffuse  warmth 
can  be  obtained,  until  the  temperature  sensation  passes  over 
into  pain,  (c)  Stimulate  a  place  that  has  poor  warm  sense,  and 
good  cold  sense  {c.g.^  the  upper  portion  of  the  forehead,  in  the 
neighbourhood  of  the  median  line)  by  temperatures  ranging,  at 
half-degree  intervals,  from  40**-52®  C.  Up  to  about  48®  you  get 
merely  the  faint  warmth  that  comes  from  stimulation  of  the 
poorly  sensitive  warm-spots.  From  this  point,  />.,  from  the  point 
at  which  the  cold  spots  would  give  the  paradoxical  cold  sensa- 
tion, the  dull  warmth  changes  to  heat.  There  is  no  pain ;  nothing 
but  a  change  of  temperature  quality.  The  introspective  records 
will  probably  speak  of  a  *  spear  point '  of  heat,  or  of  a  '  throb  of 
heat  beneath  the  skin.' 

This  experiment  serves  to  emphasise  the  incongruity  between 
the  physical  (stimulus)  and  the  mental  (sensation)  in  the  sphere 
of  temperature.  We  are  apt  to  think  of  temperatures  physically, 
as  degrees  of  one  and  the  same  quality  (thermometer  scale). 
Warmth  and  cold  are,  psychologically,  qualities  of  different 
senses,  proceeding  from  different  sense-organs.  If  they  differed 
merely  in  degree,  they  would  cancel  each  other  when  mixed,  as 
positive  and  negative  numbers  cancel  each  other  when  summed  ; 
they  could  not  possibly  fuse  together,  to  produce  a  third  con- 
scious quality.  Heat  (warmth  x  cold)  may  be  compared, 
psychologically,  to  colour  (colour  proper  x  brightness),  or  taste 
(taste  proper  x  smell),  or  the  note  of  a  musical  instrument 
^  fusion  of  a  number  of  tones  and  noise).  All  alike  are  illustra- 
tions of  *  fusion.' 

Literature.  —  Goldscheider,  op.  cit, ;  for  the  quality  of  heat, 
S.  Alrutz(Up8ala  Lakareforenings  Forhandlingar,  1897  ;  Skand. 
Arch.  f.  Physiol.,  vii.,  1897,  321  ;  Mind,  N.  S.,  vi.,  1897,  445  ; 
vii.,  1898,  141). 


92  Cutaneous  Sensation 


EXPERIMENT  TEL 

§  24.  Pressure  Spots.  Cautiom  not  noted  in  the  Text,  —  It  is 
well  to  familiarise  the  student  beforehand  with  the  pressure 
quality.  Let  him  close  his  eyes ;  then  let  the  point  be  set  down 
several  times  on  the  back  of  his  hand,  in  the  near  neighbourhood 
of  an  isolated  hair.  If  the  point  is  set  down  at  all  intensively, 
there  will  probably  be  a  dull,  diffuse,  contentless  pressure  sensed 
at  every  application  :  this  is  due  to  the  extension  of  the  deforma- 
tion of  the  skin  to  neighbouring  pressure  spots,  and  their  con- 
sequent weak  stimulation.  At  one  place,  to  windward  of  the 
root  of  the  hair,  however,  the  true  pressure  quality  will  be  ob- 
tained :  a  distinct,  sharply  localised  sensation,  of  the  kind  that 
one  might  imagine  to  be  set  up  by  the  resistance  of  a  hard  seed 
embedded  in  the  cutis  and  now  forced  inwards  by  the  pressing 
point.  If  the  pressure  be  lighter,  the  pressure  quality  is  deli- 
cate, a  little  ticklish,  of  a  kind  to  hold  the  attention  very  easily. 

The  approximation-sensation  must  be  guarded  against :  cf. 
temperature.  Less  practice  is  required  for  the  identification  of 
pressure  spots  than  is  needed  in  temperature  work. 

Questions. — E  (i)  Practically  every  hair  has  its  pressure 
spot,  which  lies  to  windward  of  the  hair  itself.  If  the  hair  is 
dark,  so  that  its  course  can  be  followed  beneath  the  skin,  it 
will  be  seen  that  the  pressure  spot  lies  directly  above  the 
hair-bulb. 

Yes.  Movement  of  the  tip  of  the  hair  calls  forth  a  weak  press- 
ure sensation,  often  somewhat  ticklish  in  character. 

Yes.  A  good  way  to  prove  this  is  to  work  from  the  back 
(hairy)  of  one  of  the  finger  phalanges  down  over  the  side  (hair- 
less) of  the  finger.  The  pressure  spots  will  be  found  to  be 
about  equally  distributed  in  the  two  places. 

The  sensations  are  indistinguishable. 

E  {2)  The  intensive.  Emphasise  the  fact  of  'tuning,'  for 
the  pressure  spots,  as  before  for  the  temperature  spots.  An 
intensity  of  pressure  which  evokes  the  *  seed '  sensation  from 
one  spot  may  evoke  only  the  weak,  delicate  pressure  sensation 
from  a  neighbouring  spot. 

O  (3)  See  above,  under  *  Cautions.* 


§  24.   PrtssHTf  spots 


93 


O  (4)  Cold.  As  regards  both  time  and  space  attributes,  there 
is  more  likeness  between  pressure  and  cold. 

O  (5)  Probably  tickling  and  cold  (mechanical  stimulation  of 
cold  spot).  Such  sensations,  if  they  occurred,  should,  of  course, 
have  been  noted  by  O  in  the  course  of  the  experiments.  The 
question  is  given  here  merely  as  a  check  upon  d's  accuracy. 

E  and  O  (6)  It  would  be  worth  while  to  ascertain  the  distri- 
bution of  the  spots  at  various  parts  of  the  body  {cf.  the  finger 
tips  with  the  upper  arm,  e^.)\  to  ask  whether  there  is  any  func- 


Fic.  9.  —  Kinesimeter. 

tional  difference  between  the  hairy  and  the  hairless  parts  of  the 
skin,  —  whether  the  pressure  sensations  yielded  by  the  hair- 
organs  and  by  the  organs  scattered  over  the  hairless  parts  of 
the  skin  are  put  to  precisely  the  same  use  by  the  organism ;  to 
note,  and  enquire  into,  the  apparently  inverse  ratio  of  tempera- 
ture to  pressure  organs  (palm  of  hand,  used  for  grasping :  good 
pressure,  poor  temperature  sensitivity ;  back  of  hand :  better 
temperature,  worse  pressure  sensitivity);  to  experiment  upon 
areal  sensitivity  to  pressure ;  etc.  Here,  again,  a  whole  list  of 
problems  presents  itself,  to  be  worked  out  as  time  permits. 


94  Cutaneous  Sensation 

Literature.  —  A.  Goldscheider,  Arch.  f.  [Anat.  u.]  Physiol., 
Suppl.,  1885  (see  Gesam.  Abh.,  i.,  1898,  185,  etc.);  M.  von 
Frey,  Ber.,  etc.,  Dec.  3,  1894,  293  ;  Aug.  2,  1897,  462;  Abh.  d. 
math.-phys.  Classe  d.  kgl.  sachs.  Ges.  d.  Wissensch.,  xxiii.,  3, 
1896,  175  ;  M.  von  Frey  and  F.  Kiesow,  Zeits.  f.  Psych.,  xx., 
1899,  126. 

Instruments.  —  Fig.  9  shows  the  kinesimeter  of  G.  S.  Hall 
and  H.  H.  Donaldson  (Mind,  O.  S.,  x.,  1885,  403,  557),  in  im- 
proved form  (E.  W.  Scripture  and  E.  B.  Titchener,  Amer.  Jour- 
nal of  Psych.,  vi.,  1894,  425  ;  vii.,  1895,  150).     $100. 

EXPERIMENT  XUI 

§  25.  Pain  Spots.  —  The  two  20  sq.  mm.  areas  are  recom- 
mended, in  order  that  the  students  may  have  an  opportunity  of 
comparing  the  distribution  of  pain  spots  with  that  of  the  press- 
ure spots,  as  determined  in  Exp.  XII.  It  is  advisable,  if  the 
pain  spots  are  to  be  stimulated  in  complete  isolation  from  press- 
ure spots,  to  work  upon  a  portion  of  the  skin  which  is  hairy  (so 
that  the  pressure  spots  can  be  easily  identified),  but  shows  fairly 
large  hairless  interspaces.  Good  areas  can  be  found  upon  the 
outer  (dorsal)  surface  of  the  upper  arm  :  but  sleeves  render  it 
difficult  to  work  upon  this  part  of  the  body.  In  any  case,  the 
area  chosen  must  be  quite  small,  or  thorough  exploration  is 
impossible. 

The  method  given  in  the  text  is,  probably,  the  most  conven- 
ient. It  is  possible  to  work  with  dyes,  as  in  the  preceding  ex- 
periments, and  to  transfer  the  skin  map  to  architects'  paper. 
The  dye  is,  however,  apt  to  run  upon  the  moistened  epidermis ; 
and  even  if  the  area  is  subdivided,  and  the  one  half  kept  moist 
while  the  other  half  is  under  stimulation,  there  will  be  times 
when  the  wet  point  must  approach  a  marked  spot  so  closely  as 
to  set  a  fringe  of  dye  spreading  over  the  skin.  Moreover,  the 
dot  of  dye  will,  at  the  best,  be  too  large  for  the  pain  spot.  The 
author  has,  therefore,  given  up  this  method  for  that  of  mapping 
by  means  of  the  skin -furrows. 

The  horse-hairs  may  be  replaced  by  a  pointed  hog's  bristle, 
or  by  a  fine  sewing  needle,  sharpened  still  further  upon  an  oil- 


$  25.   Pain  Spots  95 

stone.  The  objection  to  the  former  is  that,  after  a  few  applica- 
tions, it  has  an  obstinate  tendency  to  bend,  and  that  it  blunts 
easily.  The  objection  to  the  latter  is  that  it  readily  pierces  the 
epidermis.  Horse  hairs  seem  to  wear  better  than  bristles, 
though  the  student  will  do  well  to  have  at  least  half-a-dozen, 
ready  pointed,  before  the  experiment  begins.  For  accurate 
work,  they  should  be  standardised  by  von  Frey's  procedure : 
Ber.,  etc.,  July  2.  1894,  185  ff. 

Questions. — (i)  Pressure,  though  pain  is  every  whit  as  dis- 
tinct from  pressure  as  pressure  is  from  cold  (p.  93  above). 

(2)  This  question  may  be  answered  by  extracts  from  a  labora- 
tory note-book.  "  Each  sensation  of  coid  was  as  clear  as  crystal. 
Each  was  so  distinctly  one-of-its-kind  as  to  allow  no  doubt  on 
the  part  of  (7  as  to  its  identity.  There  were,  however,  different 
degrees  in  the  sensations  of  cold.  .  .  .  The  sensations  of  zf^/wM 
are  harder  to  distinguish  at  first  than  those  of  cold.  But  with 
practice  one  readily  distinguishes  them.  The  feeling  is  just 
one  of  warmness  —  not  heat  —  and  not  at  all  lively.  .  .  .  The 
pressure  sensation  is  like  an  electric-battery  shock  reduced  to 
small  proportions.  It  was  very  lively.  It  was  quick  and  thrill- 
like, and  seemed  to  leave  an  after-image.  .  .  .  The  sensations 
oi pain  are  very  different  from  either  the  temperature  or  the 
pressure  sensations.  They  are  minutely  fine,  wirelike,  thin ; 
much  livelier  and  more  thrill-like  than  the  pressure  sensations. 
I  could  almost  posit  an  area  for  the  pressure  sensations,  but  the 
pain  sensations  seemed  to  have  no  bigness  at  all." 

(3)  The  pain  spots  are  more  numerous  than  any  of  the 
others.  There  is  no  outward  indication  of  their  existence. 
See  von  Frey,  Ber.,  etc.,  Dec.  3,  1894,  289. 

(4)  The  moistening  lowers  the  pain  limen.  Cf.  the  sensitive- 
ness of  the  scalp  when  the  hair  is  brushed  after  bathing. 

(5)  We  might  determine  the  number  and  distribution  of  the 
spots  over  the  corresponding  area  of  the  other  side  of  the  body ; 
compare  the  number  and  '  tuning '  of  the  spots  at  more  and  less 
exposed  parts  of  the  body ;  ascertain  whether  the  number  of 
pain  spots  in  a  given  area  varies  proportionately  or  inversely  as 
the  number  of  pressure  or  temperature  spots ;  experiment  upon 
areal  sensitivity  to  pain,  etc. 


96 


Cutaneous  Sensation 


Specimen  of  Results,  —  The  accompanying  five  maps  were 
made  from  a  circle  of  2.5  cm.  diameter  upon  the  dorsal  surface 
of  the  left  upper  arm.  Special  precautions  were  taken  to  keep 
the  circle  absolutely  constant  from  day  to  day.     No.  i.,  the  first 


Fig.  10,  —  Hairs  and  pressure  spots.     The  hair-crosses  do  not  correspond 
exactly,  owing  to  the  stretching  of  the  skin. 

map  drawn,  shows  the  hairs.  Nos.  ii.  and  iii.  show  the  cold  and 
warm  spots  respectively.  No.  iv.  gives  the  pressure  spots :  the 
crosses  here  and  in  i.  indicate  coincidences  of  hair  and  pressure 
spot.  Finally,  no.  v.  shows  the  pain  spots.  These  are,  with- 
out any  doubt,  too  few.     The  experiments  were  performed  with 


Fig.  10. — Cold  spots. 


Fig.   10,  —  Warm  spots. 


a  hog's  bristle,  which  does  not  allow  of  complete  isolation  of 
the  spots  (von  Frey,  Abh.,  etc.,  244);  and  it  was  necessary  to 
hurry  the  latter  part  of  the  investigation,  with  the  result  that 
the  area  became  somewhat  sore  and  irritable. 


§  2$.   Pain  Spots  97 

Further  Experiments. — (i)  Goidscktidet^ s  *  Secondary  Press- 
ure.'—  Take  the  shaft  of  a  pin  loosely  between  the  finger  and 
thumb  of  the  right  hand,  and  bring  the  point  down  sharply  but 
lightly  upon  the  skin  of  the  back 
of  the  left  hand,  or  upon  the  left  ^^^j_^^^ 

wrist.     You  get  —  if  not  at  once,  y^»  *•*•  *^^^ 

after   two  or   three  trials  —  two  /•*•'.  .*.V«* '.'#'. V\ 

sensations:     a    primary    pressure         /  .'..•*'.•*"*.,   ,\ 
sensation,  followed  at  an  interval    p_J    .*/.*:'•  •*.*•*'    ;r^ 
of  something  under  a  second  by  a        V^,  *.*.!*•/.  '    •••/./ 
sharper,  more  thrilling  sensation.  \  •  ;  / ;  /*.,*  •/ 

—  Goldscheider,  Archiv  f.  [Anat.  n.    *       *    ••Jx 

u.]  Physiol.,  1891,  168  f.  ;    Kiilpe,  — T^'"'^ 

Outlines,    91;     Sanford,    Course,  Fig.  10. -Pain .pots, 

exp.  1 1. 

To  determine  the  precise  nature  of  this  'secondary*  sensa- 
tion, proceed  as  follows,  {a)  Stimulate  a  pressure  spot  that  has 
no  pain  spot  in  its  neighbourhood.  The  secondary  sensation  is 
absent,  {b)  Stimulate  a  pain  spot  in  the  near  neighbourhood  of 
a  pressure  spot.  Goldscheider's  two  sensations  will  be  observed. 
ic)  Stimulate  a  pain  spot  that  is  well  isolated  from  pressure 
The  first  sensation  is  absent ;  the  second  sensation  will 
be  clearly  observed.  —  It  follows,  then,  that  the  primary  sensation 
is  pressure  proper,  and  the  secondary  sensation  a  sensation  of 
pain.     See  von  Frey,  Abh.,  etc.,  243. 

(2)  Electrical  Stimulation  of  the  Pressure  and  Pain  Spots.  — 
The  organs  of  pressure  and  of  pain  respond  very  differently  to 
stimulation  by  the  interrupted  current.  The  pain  spot  replies 
by  a  steady,  continuous  sensation  ;  the  pressure  spot  by  a  whirr- 
ing or  hammering,  as  if  a  tuning-fork  were  vibrating  upon  the 
stimulated  point. 

We  may  use  for  the  experiment  the  induction  coil  and  one  of 
the  cells  required  for  Exp.  XX.  The  arrangement  of  the  induc- 
torium  must,  of  course,  be  different :  cf.  the  diagram.  The 
large-neck  electrode  will  serve  here,  too,  as  indififerent  electrode : 
it  may  be  tied  upon  the  left  lower  arm.  For  the  active  elec- 
trode we  take  a  piece  of  thin,  soft-copper  wire,  10  cm.  in  length, 
bent  upon  itself  at  right  angles  near  the  end,  and  fused  at  the 


98 


Cutaneous  Sensation 


Fig.  II.  —  Shows  the  arrange- 
ment of  the  inductorium  for 
(ordinary)  repeated  shocks. 
See  A.  Waller,  An  Introduc- 
tion to  Human  Physiol,  189 1, 
315;  and  cf.  Fig.  16. 


tip  into  a  tiny  bulb.     This  electrode  is  made  the  negative  pole 
of  the  break-shock.      It  may  be  applied  to  the  hairy  part  of 

the  back  of  the  left  hand,  though  bet- 
ter results  will  be  obtained  from  the  leg, 
where  the  hairs  are  set  farther  apart. 
As  we  gradually  bring  the  secondary 
towards  the  primary  coil,  passing  the 
electrode  meanwhile  over  the  cutaneous 
surface,  we  get  here  and  there  a  distinct 
pain  sensation.  The  pain  increases,  as 
the  secondary  coil  comes  farther  in,  un- 
til it  reaches  the  intensity  of  a  feeling 
of  injury,  as  if  the  skin  were  being  torn 
with  a  needle.  The  intervening  skin 
spaces  give  no  sensation.  If  the  elec- 
trode travel  over  a  hair-bulb,  there  may 
be  a  sensation  of  pain,  though  as  a  rule  there  is  none.  When  the 
pain  has  reached  a  decidedly  unpleasant  intensity,  the  pressure 
spots  come  into  play.     Their  reaction  is  quite  unmistakable. 

A  pretty  comparative  experiment  may  be  performed  as  follows.  Deter- 
mine the  distance  between  the  coils  at  which  you  can  just  sense  the  pressure- 
hammering  when  the  active  electrode  is  placed  upon  the  tongue.  Now  lay 
the  electrode,  first,  upon  the  top  of  the  gum,  at  the  point  of  emergence  of  one 
of  the  incisor  teeth,  and  then  upon  the  upper  surface  of  the  tooth  itself.  In 
the  former  case  you  get  the  hammering  only ;  in  the  latter,  a  steady  pain. 

Note  that  upon  the  palm  of  the  hand,  where  the  epidermis  is  very  thick,  the 
first  sensation  to  appear  is  not  that  of  pain,  but  that  of  pressure. 

Von  Frey,  Ber.,  etc.,  Dec.  3,  1894,  290  fF. 

(3)  The  demonstration  of  Kiesow's  painless  cheek-area  is 
always  interesting  to  students.  See  Kiesow,  Philos.  Studien,  ix., 
1894,  512  ;  xiv.,  1898,  567;  von  Frey,  Ber.,  etc.,  Dec.  3,  1894,  293. 

Literature.  —  M.  von  Frey,  Berichte  d.  math.-phys.  Classe  d. 
kgl.  sachs.  Ges.  d.  Wiss.  zu  Leipzig,  July  2,  1894,  18$  ;  Dec.  3, 
1894,  283  ;  Abhandl.  d.  math.-phys.  Classe  d.  kgl.  sachs.  Ges.  d. 
Wiss.,  xxiii.,  3,  1896,  239,  251.  Von  Frey's  proof  that  the  pain 
organs  lie  more  superficially  than  the  organs  of  pressure  and 
temperature,  and  his  theory  of  pain  stimulation  {cf.  Titchener, 
Outline,  73),  should  be  fully  explained  in  a  lecture. 


CHAPTER   IV 
Gustatory  Sensation 

§  26.  Onitatory  Sensation.  —  F.  Kiesow  has  attempted  to  ar* 
range  the  taste  qualities  in  a  schema,  of  the  same  nature  as  the 
colour  circle  (Philos.  Studien,  xii.,  1896.  273).  The  taste  circle 
has  two  diameters,  a  vertical  and  a  horizontal.  Above  and 
below  stand  salt  and  sweet ;  to  left  and  right,  bitter  and  sour. 
Along  the  periphery  are  arranged  the  mixed  qualities  salt-sour, 
sour-sweet,  etc.  The  horizontal  diameter  represents  the  bitter- 
sours;  the  lower  half  of  the  vertical  diameter  represents  the 
salt-sweets,  the  upper  half  the  insipid  alkaline  mixtures.  Wundt 
has  adopted  this  schema  (Outlines  of  Psych.,  trans,  by  C.  H. 
Judd,  1897,  53),  together  with  the  underlying  idea  that  the  sen- 
sations of  taste  form  a  continuum  of  two  dimensions. 

The  author  doubts  whether,  in  the  present  state  of  our  know- 
ledge, this  idea  can  be  accepted.  He  doubts,  e.g.,,  whether  the 
sweet-sour  of  lemonade  stands  to  its  originals  as  blue-green 
stands  to  blue  and  green,  or  as  orange  to  red  and  yellow ;  and 
also  whether  bitter  should  lie  in  the  same  plane  with  the  other 
three  taste  qualities.  We  must  suspend  judgment :  in  the 
meantime,  Kiesow's  figure  provides  us  with  a  working  hypothesis. 

On  taste  sensations  in  general  see  Wundt,  Phys.  Psych.,  i., 
»^3»  438;  M.  von  Vintschgau,  Hermann's  Hdbch.  d.  Physiol., 
iii.,  2,  1880,  145;  Kiilpe,  Outlines,  96;  Titchener,  Outline,  62; 
Foster,  Text-book  of  Physiol.,  iv.,  1891,  1397. 

experiment  xiy 

§  27.  Biftribntion  of  Taste  Sensitivity  over  the  Ton^e.  Cau- 
tions not  noted  in  the  Text.  —  It  should  hardly  be  necessary  to 
impress  upon  the  student  the  need  of  cleanliness  in  taste-work. 
The  handkerchief  should  never  be  used  to  wipe  the  tongue,  or 
to  dry  a  brush  :  it  should  stay  in  the  pocket.     The  mouth  should 

99 


100  Gustatory  Sensation 

be  freed  from  all  food  particles ;  and  the  student  should  avoid 
the  taking  of  any  strong-smelling  food,  or  of  any  considerable 
quantity  of  strongly  tasting  food,  shortly  before  the  experiment : 
in  the  former  case,  he  becomes  disagreeable  to  E,  and  in  the 
latter  the  organ  may  be  partly  exhausted  before  work  begins. 
The  brushes  should  either  be  thrown  away  after  use,  or  (if  they 
must  be  used  again)  carefully  washed  and  disinfected. 

It  is  essential  that  these  experiments  be  performed  in  a  good 
light.  No  special  directions  need  be  given  about  the  lens ;  any 
large  'magnifying  glass,'  clamped  in  the  proper  supports,  will 
serve  the  required  purpose.  The  lens  used  in  the  Cornell  Labo- 
ratory is  one  of  12.5  cm.  diameter  and  25  cm.  focus.  If  O 
prefers  to  stimulate  his  own  tongue,  a  concave  (enlarging)  glass 
mirror  may  replace  the  lens.  The  filled  brushes  are  then  handed 
by  E  to  O,  who  applies  them  to  the  required  papilla,  under  the 
guidance  of  the  mirror  image. 

Kiesow  recommends  brushes  of  8  mm.  length,  and  a  mean 
diameter  (when  wetted)  of  i  mm. ;  Oehrwall,  brushes  of  2  cm. 
length  and  5  mm.  diameter.  We  have  obtained  the  best  results 
with  brushes  of  2.5  to  3  cm.  length,  and  5  mm.  diameter  at  the 
insertion  of  the  handle.  The  point  must  be  trimmed  with  the 
greatest  nicety.  When  the  brush  has  once  been  dampened, 
the  merest  trace  of  extra  liquid  is  sufficient  to  stimulate  the 
papilla. 

If  need  arise,  the  strength  of  the  solutions  may  be  varied. 
Sanford  recommends  (weak)  sugar,  5^;  (strong)  sugar,  40^; 
tartaric  acid,  5  ^.  A  few  preliminary  trials  will  decide  the  mat- 
ter. The  solutions  should,  in  summer,  be  kept  at  the  tempera- 
ture of  the  room  in  which  the  experiments  are  made  ;  in  winter, 
slightly  warmed. 

It  is  necessary  to  assure  oneself  (by  preliminary  trials)  that 
the  distilled  water  is  tasteless.  It  should  not  be  difficult  to 
procure  water  (distilled  or  other)  which  is  reported  as  without 
taste  ;  but  the  tastelessness  must  not  be  taken  for  granted.  A 
particular  O  may  sense  distilled  water  as  quite  noticeably  sweet 
or  sour  or  bitter ;  and  one  and  the  same  O  may  report  different 
tastes  at  different  parts  of  the  tongue.  The  author  has  never 
known  a  case  in  which  distilled  water  has  given  a  salt  taste. 


§  27-   Distribtition  of  Taste  Sensitivity  loi 

Since  both  sour  and  sweet  'contrast  *  with  salt  (see  Exp.  XVI.), 
a  trace  of  salt  may  neutralise  the  water  for  an  O  who  gets  the 
>our  or  sweet  sensation.  Bitter,  unfortunately,  does  not  con- 
t  with  any  other  taste,  and  hence  cannot  be  eliminated  by 
l>ensation.  It  remains,  then,  in  certain  rare  cases,  as  a  con- 
stant source  of  disturbance  in  the  experimental  series. 

Experiment.  —  E.xtreme  care  must  be  taken  that  the  drop 
held  in  the  brush  does  not  spread  to  other  papillae  than  that 
under  stimulation.  The  spreading  may  be  due  to  excess  of 
liquid,  or  to  the  presence  of  saliva  upon  the  surface  of  the  organ. 

The  tongue  might,  of  course,  be  dried  by  pressing  with  cotton 
wool  or  a  fine  cloth  immediately  upon  exposure  :  but  the  result 
is  usually  a  too  speedy  evaporation,  and  a  consequent  reduction 
of  the  sensitivity  of  the  papillae.  With  care,  the  squeeze 
against  the  roof  of  the  mouth  answers  well.  —  Individuals  differ 
greatly  in  their  power  to  hold  the  tongue  steady.  But  practice 
soon  gives  the  required  control. 

Notice  that  bitters  are  more  lasting  than  other  tastes.  Hence, 
whenever  a  bitter  comes  in  the  series,  a  longer  pause  than  the 
customary  2  to  3  min.  must  be  made. 

*  Imagination  *  and  *  suggestion  '  may  play  a  large  part  in  this 
experiment :  hence  the  necessity  of  keeping  O  in  ignorance  of 
the  nature  of  the  stimulus  and  the  results  obtained  with  previ- 
ous applications. 

Questions.  —  (i)  Yes;  although  the  evidence  is  not  easy  of 
quantitative  interpretation.  If  all  doubtful  cases  in  the  Table 
(all  .^-judgments)  are  omitted,  it  will  probably  be  found  that  cer- 
tain papillae  are  sensitive  only  to  sweet ;  possibly,  that  some 
are  sensitive  only  to  salt  or  acid :  it  is  not  likely,  at  any  rate  in 
this  area  of  the  tongue,  that  a  papilla  will  be  found  which  is 
exclusively  sensitive  to  bitter.  On  the  other  hand,  several  will 
probably  be  insensitive  to  bitter;  some,  perhaps,  to  salt  and 
acid  ;  and  the  whole  region  may  possibly  prove  to  be  insensitive 
to  sweet.  Other  combinations  of  sensitiveness  and  insensitive- 
ness  will  probably  be  found,  but  can  hardly  be  predicted.  It  is 
natural  that  differences  should  obtain,  seeing  that  the  papilla  is 
a  bunch  or  cluster  of  taste-cells,  and  that  in  these,  if  in  any  part 
of  the  peripheral  organ,  the  specific  taste  energies  would  reside. 


102  Gustatory  Sensation 

Question  (i)  may  be  extended,  as  follows.  Can  you  infer 
anything,  from  the  experimental  results,  as  to  the  function  and 
distribution  of  the  ultimate  end-organs  of  taste  (the  taste-cells 
in  the  beakers)  ? 

(2)  The  results  vary  considerably  (at  least  in  the  early  stages 
of  practice)  from  individual  to  individual.  It  is,  however,  prob- 
able that  salt  and  acid  will  be  readily  confused.  This  is  natural 
if,  as  has  recently  been  argued,  sweet  and  bitter  are  the  primi- 
tive taste  sensations.  Cf.  also  the  nature  of  their  concomitant 
sensations,  mentioned  under  (3). 

(3)  In  many  experiments  O  will  report  a  pressure,  tempera- 
ture (warm  or  cold)  or  pain  (stabbing,  biting,  burning)  sensa- 
tion. These  concomitant  sensations  will  be  characterised 
somewhat  as  follows,  (i)  Sour  is  at  first  astringent;  then,  as 
it  becomes  stronger,  burning;  finally,  purely  painful.  (2)  Salt 
is  attended  by  a  weak  burning,  not  rising  to  positive  pain.  (3) 
Sweet  brings  with  it  the  perception  of  smoothness  and  softness. 
At  high  intensities  of  stimulus,  it  pricks  or  gives  a  sharp  burn. 
(4)  Bitter  suggests  something  fatty.  At  high  intensities,  it 
may  burn. 

(4)  Bitter  is  set  up  noticeably  later  than  sweet  or  acid.  Since 
(9's  attention  in  this  experiment  is  directed  mainly  upon  the 
quality  of  the  aroused  sensation,  the  time-difference  may  escape 
him.  It  occasionally  happens,  however,  that  a  single  stimulus 
calls  forth  a  mixture  of  sensations.  In  such  cases,  the  simul- 
taneity or  succession  of  the  components  can  be  noted.  Thus 
acid  may  evoke  a  sour-salty  taste  (simultaneous) ;  a  bitter  may 
evoke  a  slight  sweet  followed  by  a  bitter.  The  reasons  for  the 
mixture  cannot  be  given  with  any  certainty.  But  associative 
processes,  central  or  peripheral  {cf.  above)  or  both,  are  always 
to  be  suspected. 

(5)  Associative  processes,  as  just  remarked.  Also  peripheral 
fatigue ;  especially  in  the  case  of  the  bitter  and  sweet  (strong) 
solutions. 

The  second  of  these  we  seek  to  rule  out  by  allowing  an  ade- 
quate time-interval  to  elapse  between  experiment  and  experi- 
ment. The  former  we  combat  by  the  introduction  of  the 
experiments    with    distilled    water  — '  blank '    experiments    or 


§  2/.   Distribution  of  Taste  Sensitivity  103 

'puzzle*  experiments,  as  they  are  called.  The  object  of  these 
experiments  is  to  hold  the  attention  of  O  rigorously  upon  the 
stimuli ;  a  habit  of  judgment,  formed  under  the  influence  of 
associations,  will  receive  a  rude  shock  when  there  is  absolutely 
no  sense-material  offered  around  which  the  associations  may 
group,  —  and  so  O  will  be  'waked  up*  to  a  more  objective  atti- 
tude. 

(6)  i.  The  Taste^ffects  of  Mecfianical  and  Electrical  Stimula- 
tion of  the  Papilla. — Meclianical  stimulation  may  easily  be 
tried,  by  help  of  the  pressure-point  of  Exp.  XII.  No  sensa- 
tions of  taste  will  be  obtained.  Notice,  however,  that  a  press- 
ure upon  the  base  of  the  tongue  gives  a  distinctly  bitter 
sensation.  This  may  be  a  mechanically  aroused,  peripheral 
sensation ;  or  may  be  an  associative  process,  attached  to  the 
choking  and  nausea  that  follow  from  the  application  of  stimulus. 
The  question  whether  electrical  stimulation  of  a  papilla  sets  up 
a  taste  sensation,  over  and  above  the  sensations  indirectly 
aroused  by  decomposition  of  the  saliva,  is  still  undecided,  and 
is  very  difficult  of  decision.  Unless  some  weeks  can  be  given  to 
the  repetition  of  the  principal  experiments  (see  References)  the 
problem  is  better  left  untouched. 

ii.  The  Taste-reactions  of  Other  Forms  of  PapillcB.  —  (a)  Fill 
a  brush  with  one  of  the  (weak  solution)  liquids,  and  paint  lightly 
over  an  area  of  the  circumvallate  papillae.  All  four  tastes  will 
be  obtained  The  fungiform  papillae  are,  in  fact,  only  less 
highly  developed  forms  of  these  circumvallate  papillae,  {b)  Set 
a  drop  of  liquid  (strong  solution)  upon  the  filiform  papillae,  tak- 
ing care  that  no  fungiform  papilla  is  afifected.     No  taste  results. 

iii.  Proof  of  the  Independence  of  the  Four  Taste-qualities  by 
Elimination  of  Each  singly. — (rt)  Find  a  papilla  which  is  ex- 
tremely sensitive  to  bitter.  Paint  it  a  few  times  over  with  a  10 
to  205b  solution  of  cocaine  hydrochlorate.  Notice  that,  while 
the  bitter  taste  is  entirely  abolished,  the  other  tastes  of  which 
the  papilla  is  capable  remain,  {b)  If  the  papilla  is  capable  of 
sweet  and  salt,  or  sweet  and  sour  sensations,  over  and  above  the 
bitter,  continue  the  painting.  Notice  that  the  salt  (or  sour) 
sensation  persists,  after  sweet  has  undergone  the  same  fate  as 
biitcr.    (c)  Find  a  papilla  which  is  extremely  sensitive  to  sweet. 


I04 


Gustatory  Sensation 


Paint  it  over  with  a  saturated  alcoholic  solution  of  gymnemic 
acid.  Notice  that  the  other  qualities  of  which  the  papilla  is 
capable  remain  after  the  abolition  of  the  sweet  sensation. 

Results. — The  following  results,  showing  the  sensations 
recorded  in  single  series  (ttot  averages)  from  four  papillae,  may 
be  taken  as  typical  for  an  unpractised  O : 


(0 

Weak  solutions : 

Papilla. 

Sugar. 

Salt. 

Acid. 

Quinine. 

Water. 

I       .      . 

.      .           + 

sour 

— 

+ 

— 

2      .      . 

.      .           ? 

? 

very 
faint 
bitter 

3    •    • 

.      .            ? 

sour 

salt 

—  (cold) 

— 

4     .     • 

.    .        +                +  (weak) 

slight 

— 

— 

salt 

(2) 

Strong  solutions 

: 

I     .     . 

.    .       + 

+ 

salt 

—  (sting) 

— 

2      .      . 

.    .       — 

-  (sting) 

— 

+  + 

— 

3    •    • 

.    .       + 

4- 

? 

+  + 

—  (cold) 

4    .     • 

.    .       + 

+ 

salt 

+  + 

— 

(3)   Weak  solutions,  with  spread  of  stimulus   owing  to  too 


large  brush 

2  .    .    .    . 

3  .    .    .    . 

4  .    .    .    . 

5  .    .    .    . 


+ 
+ 

+  + 


+  + 

+ 

+ 
+  + 


+ 
salty 
bitter 

+  + 

+ 


weak  sour 

? 


Literature.  —  H.  Oehrwall,  Untersuchungen  liber  den  Ge- 
schmackssinn.    In  the  Skand.  Archivfiir  Physiologic,  1890,  ii.,  i. 

F.  Kiesow,  Schmeckversuche  an  einzelnen  Papillen.  In 
Wundt's  Philosophische  Studien,  1898,  xiv.,  591. 

F.  Hofmann  and  R.  Bunzel,  Untersuchungen  iiber  den  elek- 
trischen  Geschmack.  In  Pfluger's  Archiv  fiir  die  gesammte 
Physiologic,  1897,  Ixvi.,  215. 


§  28.    Th€  Number  of  Taste  Qualities  105 

R.  von  Zcynek,  Uebcr  den  elektrischen  Geschmack.     In  the 
Centralblatt  fur  Physiologie,  10  Deer.,  1898,  xii.,  617. 
W.  Sternberg,  Zeits,  f.  Psych.,  xx.,  1899,  385. 

IXPBRIMENT  ZV 

{  28.  The  Number  of  Taite  Qualities.  Cautions  not  noted  in 
the  Text.  —  All  odorous  solutions  should  be  in  narrow-mouthed 
phials,  and  should  be  kept  carefully  corked  when  not  in  use,  to 
avoid  diffusion  of  their  odour,  and  the  consequent  possible  recog- 
nition by  O  in  inspiration.  They  should  be  of  the  temperature 
of  the  room,  in  summer ;  slightly  warmer,  in  winter.  The  phials 
should,  further,  be  covered  with  paper,  so  that  the  solutions 
cannot  be  distinguished  by  differences  of  colour.  The  following 
*  tastes '  are  easily  procurable  : 

Synip  of  Onmge.     15%  solution.  Clam  BouilloQ. 

Lime  Juice.     10%.  Milk. 

Tar  Water  (made  firom  5  %  Wine  of  Tar).  Tea. 

S}Tup  of  Sarsaparilla.     1 5  %.  Coffee. 

Solution  of  Powdered  Alum.     2%.  Vinegar. 

Elssence  of  Wintergreen.     5%.  Mushroom  Catsup. 

SjTup  of  Lemon.     15%.  Pineapple  Syrup.     15%. 

Syrup  of  Chert}'.     15%.  Essence  of  Peppermint.     2%. 

Essence  of  Sassafras.     5%.  Gum  Arabic. 

95%  Alcohol.     33%.  Chocolate. 

Peach  *  fruit  flavour.'     5%.  Lime  Water. 

Essence  of  Bitter  Almonds.     2%.  Lithia  Water. 

Essence  of  Anise.     5  %.  Tomato  Catsup. 

Epsom  Salts.     2  %  of  crystals.  Maple  syrup. 

Beef  Bouillon.  Toast  and  water. 

Questions. — (i)  No.  No  stimulus  is  recognised.  Nothing 
is  sensed  but  the  four  tastes,  with  pressure  (tingling,  pricking), 
temperature  (cold,  bum)  and  possibly  —  if  the  solutions  be  too 
strong  —  pain  accompaniments. 

(2)  Partly  to  avoid  peripheral  fatigue ;  partly  to  rule  out  all 
chances  of  associative  influence  upon  judgment ;  partly  to  coun- 
teract the  variable  errors  of  habituation  and  expectation. 


lo6  Gustatory  Sensation 

(3)  In  order  that  introspection  may  not  be  influenced  by  an 
odour  sensed  in  the  act  of  inspiration.  ^*s  nostrils  must  be  very 
tightly  plugged,  for  the  same  reason. 

(4)  Yes.  The  name  of  the  stimulus  would  bring  a  host  of 
associations  with  it,  and  a  pure  experiment  would  then  be 
impossible. 

Results.  —  The  following  results  may  be  taken  as  typical : 

Solution.  Taste  reactions  of  a  single  papilla,  on  different  days. 

Tar  (i)  Sharp,  salty  taste ;  (2)  Salty. 

Anise  (i)  Very  sharp;  (2)  Sour,  with  sharp  burn. 

Alcohol  (i)  Salt  and  bitter ;  (2)  Salt. 

Lemon  (i)  Burns:  sour  or  salt ;  (2)  Sharp  burn. 

Wintergreen  (i)  Sweet;  (2)  Sharp  taste. 

Alum  (i)  Very  slightly  salt ;  (2)  Nothing. 

Bitter  Almond  (i)  Bitter:  burns;  (2)  Bitter:  burns. 

Cherry  (i)  Sweet;  (2)  Sweet. 

Peach  (I)  ?  Cold;  (2)  Cold. 

Epsom  salts  (i)  Salty;  (2)  Burns. 

Orange  (i)  Sweet;  (2)  Nothing. 

Sarsaparilla  (i)  Sour,  and  slightly  bitter ;  (2)  Bitter. 

Pineapple  (i)  Sweet;  (2)  Sweet. 


Etc.,  etc. 


EXPERIMENT  XVI 


§  29.  Taste  Contrasts.  Cautions  not  noted  in  the  Text. — 
'Strong'  and  *weak,'  as  applied  to  taste  solutions,  are  doubly 
relative  terms,  (i)  Individuals  differ.  Thus,  if  the  30  %  sugar 
solution  give  no  sensation  beyond  a  *  sharp  burn,'  it  will  plainly 
be  necessary  to  reduce  the  strength  of  the  standard  sweet. 
(2)  Practice  makes  a  great  difference.  Thus,  in  the  early  stages 
of  taste-work,  a  salt  solution  of  2  %  sat.  sol.  may  be  subliminal.  — 
The  Instructor  must  not  expect,  then,  that  the  numerical  x^^vXts 
of  this  experiment  will  show  any  great  uniformity,  as  between 
different  students. 

O  knows  the  quality  of  the  standard  and  of  the  weaker  solu- 
tions, but  should  not  know  whether  one  of  the  weaker  solutions 
or  merely  water  is  to  be  expected  in  a  given  case. 


§  29-    Tast€  Contrasis  107 

Exact  simultaneity  in  the  application  of  the  two  stimuli  is  not 
necessary.  If  there  is  any  time  difference,  the  standard  solution 
must,  of  course,  be  applied  first. 

Results.  — The  following  results  may  be  taken  as  typical : 

Standard :  50%  sat  salt  sol. 

Dtst.  water  b  sensed  as :  nothing ;    bitter  with  suggestion  of 

sweet;  mere  suggestion  of  sweet; 
very  slightly  sweet. 

Sabl.  sqgar  sol.    **     "  suggestion    of  sweet ;    faint,  slight, 

weak  sweet;  good  sweet. 

Weak  sugar  sol.   **     **  sweet ;  good  sweet :  very  sweet. 

Standard :  30%  sat.  sugar  sol. 

Dist.  water  b  sensed  as :  nothing ;  faint  bitter ;  suggestion  of 

salt  in  moment  of  application,  then 
nothing;  slight  bitter-salty;  sugges- 
tion of  salt. 

Subl.  salt  sol.       **     **  weak,    faint    salt ;  good  salt ;    very 

salt. 

Weak  salt  sol.      "     **  decided  salt ;  very  salt. 

Questions.  — (i)  We  find  {a)  that  distilled  water,  previously 
tasteless,  becomes  faintly  salt  or  sweet,  as  contrast  requires. 
{b)  A  subliminal  solution  gives  a  clear,  and  at  times  a  strong, 
sensation,     (r)  The  weak  solutions  give  quite  strong  sensations. 

Now  it  is  doubtless  true  that  O,  in  spite  of  our  initial  caution, 
is  expecting  a  contrast-sensation.  But  O  does  not  know  when 
the  water  stimulus  is  coming ;  and  has  no  reason,  a  priori,  to 
suppose  that  water  will  be  sensed  by  taste  at  all.  Indeed,  the 
use  of  water  in  the  blank  experiments  of  Exps.  XIV.  and  XV. 
would  rather  suggest  that  water  will  not  be  tasted.  As  we  find 
that  water  sometimes  gives  *  nothing '  and  sometimes  something, 
—  expectation  remaining  the  same,  —  we  may  be  pretty  confi- 
dent that  a  real  contrast  is  present  when  a  taste  is  set  up. 
Again:  a  record  like  the  "  suggestion  of  salt  in  moment  of  appli- 
cation, then  nothing,"  given  above,  is  evidence  that  O  is  well  on 
his  guard,  and  able  to  distinguish  the  'suggested*  from  the 
peripheral  sensation.  The  expectation-taste,  so  to  call  it,  is 
negatived  by  introspection.     Moreover,  there  are  enough  dis- 


io8  Gustatory  Sensation 

turbing  factors  in  the  experiments  to  upset  any  hard-and-fast 
expectation.  Thus,  as  we  see  in  the  above  results,  both  sugar 
and  salt  may  make  distilled  water  taste  bitter.  The  phenome- 
non is  of  not  infrequent  occurrence,  and  is  very  difficult  to 
explain,  since  bitter  (as  we  shall  see  below)  does  not  contrast 
with  any  other  taste,  {a)  Possibly,  in  some  instances,  the  '  bit- 
ter' may  be  an  associative  process  due  to  verbal  suggestion: 
language  opposes  '  bitter '  to  '  sweet,'  quite  definitely,  {b)  In 
other  cases,  it  may  be  that  the  effort  of  holding  out  the  tongue 
involves  something  like  a  choking  or  incipient  vomiting  reflex, 
so  that  the  associative  bitter  of  the  base  of  the  tongue  comes 
into  play,  {c)  It  is  noteworthy,  too,  that  the  *  bitter  *  of  distilled 
water  is  often  designated  a  'smooth  bitter.'  It  may  be,  then, 
that  the  'smoothness*  of  the  water,  as  distinguished  from  the 
weak  burning  characteristic  of  salt  of  all  intensities,  and  the  sharp 
burn  characteristic  of  sugar  solutions  of  high  intensity,  suggests 
the  '  fatty '  concomitant  of  bitter  (see  p.  102),  and,  by  that  means, 
bitter  itself.  —  Further  (though  this  fact  does  not  appear  in 
our  Table),  the  standard  sugar  solution  will,  at  times,  induce 
not  salt  but  sweet,  its  own  quality.  In  view  of  these  irregulari- 
ties, we  may  safely  assume  that  an  obstinate  '  expectation '  of 
contrast  would  be  broken  up  in  the  course  of  the  experimental 
series,  and  that  the  contrast-effects,  when  obtained,  are  what 
they  profess  to  be.  —  We  shall  return  to  the  point  below. 

(2)  The  sweet  induced  by  the  salt  is,  at  least  for  most  i9's, 
stronger  and  clearer  than  the  salt  induced  by  the  sugar. 

(3)  The  following  experiments  suggest  themselves. 

{a)  We  have  used  a  strong  solution  as  the  inducing  taste :  as 
if  on  the  assumption  that,  in  taste  as  in  sight,  the  more  satu- 
rated quality  will  provoke  the  stronger  contrast-effect.  It  would 
be  well,  now,  to  try  the  inducing  power  of  weak,  just  supra- 
liminal, solutions.  If  these  are  able  to  colour  distilled  water 
with  the  contrast-taste,  and  to  raise  a  subliminal  taste  above  the 
limen,  our  belief  in  the  contrast-phenomenon  at  large  will  be 
increased :  for  one  would  hardly  *  expect '  so  definite  a  result 
from  so  weak  a  stimulus. 

It  may  be  said  that  all  the  contrasts  obtainable  from  strong 
are  also  obtainable  from  weak  solutions.     Indeed,  for  some  (9's, 


§  29-    Taste  Contrasts  109 

the  weak  solutions  induce  better  than  the  strong ;  for  the  effect 
of  the  strong  stimulus  is  to  draw  the  attention  to  itself,  and 
away  from  the  quality  of  the  weaker  (contrast)  sensation. 

(b)  It  would  be  well  to  test  other  taste  qualities,  with  a  view 
to  the  ascertainment  of  their  contrast  relations.  If  this  is  done, 
we  find : 

i.  that  salt  and  sour  contrast :  the  sour  induced  by  salt  being 
clearer  and  stronger  than  the  salt  induced  by  sour; 

ii.  that  sweet  and  sour  contrast :  the  sweet  induced  by  sour 
being  clearer  and  stronger  than  the  sour  induced  by  sweet ; 

iii.  that  bitter  shows  no  contrast  at  all :  subliminal  bitter,  if 
ipplied  simultaneously  with  sweet,  sour  or  salt,  is  always  sensed 
(when  it  is  sensed  at  all)  as  sweet ;  and  supraliminal  bitter  is 
from  the  very  first  strong  and  insistent. 

If  we  add  to  this  summary  the  result  of  the  foregoing  experi- 
ment : 

iv.  that  salt  and  sweet  contrast :  the  sweet  induced  by  salt 
being  clearer  and  stronger  than  the  salt  induced  by  sweet ;  we 
come  upon  the  general  rule  of  taste-contrasts,  that  the  order  of 
qualities,  as  regards  ease  of  induction,  is  sweet,  sour,  salt,  bitter. 

{c)  It  would  be  worth  while  to  test  the  simultaneous  by  the 
successive  method.  In  this,  E  drops  the  standard  solution  upon 
the  tip  (not  the  side)  of  O's  tongue.  The  liquid  is  left  in 
place  for  3  sec.  0  then  washes  out  his  mouth,  vigorously  and 
thoroughly,  with  distilled  water.  When  all  trace  of  the  former 
sensation  has  disappeared,  E  applies  the  second  (weaker)  stimu- 
lus to  the  same  part.  O's  judgments  of  this  second  stimulus 
are  recorded. 

The  experiment,  in  this  form,  should  be  tried  with  various 
intensities  of  inducing  stimulus,  and  with  all  the  taste  qualities. 
It  will  be  found  that  contrast  is  here  less  readily  set  up(/.r.,  that 
it  takes  a  stronger  inducing  stimulus  to  evoke  it)  than  in  the 
simultaneous  method.  The  pauses  between  experiments  must 
be  regulated  by  the  intensities  of  stimulus  employed ;  but  the 
mouth  should  be  rinsed  for  at  least  30  sec,  even  when  the 
inducing  taste  is  barely  supraliminal. 


no  Gustatory  Sensation 

The  results  of  the  previous  experiments  will  be  confirmed. 

{d)  It  should  be  possible,  by  aid  of  a  long  series  of  intensively 
graded  solutions  of  the  contrast-taste,  roughly  to  measure  the 
effect  of  the  inducing  solution.  Thus,  if  a  5  %  salt  sol.  has  been 
judged  (by  contrast)  as  *good  salt,'  the  mouth  could  be  violently 
rinsed,  and  then  this  same  intensity  'good  salt'  matched  (with- 
out contrast)  from  the  series  of  graded  salt  solutions.  —  The 
experiment  would,  however,  be  tedious,  and  its  results  not 
very  accurate.  Still,  it  might  be  assigned  as  a  problem  to  an 
interested  student. 

Related  Experiments. — (i)  We  spoke,  in  Exp.  XIV.,  of 
*  neutralising '  the  taste  of  distilled  water  by  adding  salt  to 
it,  —  as  if  the  sweet  or  sour  taste  could  actually  be  cancelled  by 
the  addition  of  a  stimulus  of  contrasting  quality.  The  experi- 
ment may  now  be  tried  for  its  own  sake.  A  20  %  sugar  solu- 
tion, e.g.,  may  be  taken,  and  changed  from  experiment  to 
experiment  by  the  intermixture  of  a  small  quantity  of  saturated 
salt  solution.  The  student  may  be  left  to  regulate  the  time- 
interval  between  test  and  test,  and  to  determine  the  amount  of 
salt  to  be  added  to  a  given  quantity  of  sweet.  Does  the  solu- 
tion reach  a  stage  of  complete  gustatory  indifference }  Does 
it  pass  at  a  jump  from  sweet  to  salt.^  Or  is  neither  of  these 
alternatives  realised,  but  a  new  taste  altogether  set  up  with 
intensive  equality  of  the  two  primary  tastes } 

These  questions  are  differently  answered  by  different  observ- 
ers. Taste  is  subject  to  enormous  individual  variation,  and  this 
particular  experiment  shows  the  variation  in  its  extremest  form. 
Some  observers  get  a  neutralisation  even  with  bitter  and  sweet, 
although  bitter,  for  the  same  observers,  shows  no  trace  of  con- 
trast-effect !  Others  get  nothing  more  than  the  (more  or  less 
abrupt)  change  of  primary  taste  qualities.  One  result,  however, 
comes  out  pretty  constantly  :  that  a  compensating  mixture  of 
sweet  and  salt  gives  rise  to  an  'insipid,'  'flat,'  alkaline  taste, 
entirely  distinct  from  that  of  the  two  components. 

(2)  This  result  suggests  a  further  experiment,  —  the  synthe- 
tising  of  the  two  mixed  tastes,  alkaline  and  metallic,  which  have 
played  so  large  a  part  in  the  discussions  concerning  the  number 
of  discriminate  taste  qualities.     The  alkaline  and  metallic  tastes 


§  29>    TasU  Contrasts  1 1 1 

contain  (<i)  the  taste  of  the  mixture  of  two  or  more  of  the  true 
taste  qualities,  and  {b)  a  certain  complex  of  pressure  and  other 
concomitant  sensations.  Acting  on  the  hint  that  sweet  and 
salt,  in  proper  proportion,  give  an  alkaline  flavour,  the  student 
may  set  to  work  accurately  to  synthetise  or  reconstruct  this  and 
the  metallic  taste.  His  first  step  is  a  careful  introspective 
analysis  of  certain  solutions  that  give  these  tastes.  Then  he 
begins  his  reconstruction  as  systematically  as  the  outcome  of 
introspection  and  the  facts  of  the  preceding  experiments  allow. 

Literature,  —  M.  von  Vintschgau,  Hermann's  Handbuch  d. 
Physiol.,  HI,  2,  2\()i.  A.  Goldscheider  and  H.  Schmidt,  Gold- 
scheider's  Ges.  Abh.,  i.,  1898,  382  (synthetises  the  alkaline  taste 
from  bitUr^  salt  and  'sensible  Erregung');  Wundt,  Outlines  of 
Psych.,  53  (suggests  that  alkaline  =  salt  and  sweet,  metallic  = 
salt  and  sour). 

Cf.,  also,  G.  T.  W.  Patrick,  Iowa  Studies  in  Psych.,  ii.,  1899, 
85 ;  R.  W.  Tallman  and  H.  Gale,  Gale's  Psych.  Studies,  L, 
1900,  118. 


CHAPTER   V 

OLFACTORY    SENSATION 

§  30.  Olfactory  Sensation.  —  Exercise  (  i  ).  —  This  test  need  not 
be  given  if  O  is  sufficiently  impressed  by  Exp.  XV.  As  a  rule, 
however,  there  is  still  some  scepticism  remaining,  after  the 
papilla  work,  which  can  be  dispelled  only  by  work  in  the  gross. 

Identification  is  quite  impossible  in  terms  of  taste  alone. 

(2)  Both  substances  'smell  sweet.*  So  strong  is  the  asso- 
ciation, that  the  realisation  of  the  actual  taste  comes  with  a  shock 
of  surprise  even  to  a  practised  observer. 

(3)  Zwaardemaker  distinguishes  nine  smell  classes  : 

(i)  Ethereal  scents.     All  fruit  odours. 

(2)  Aromatic  scents.     Camphor  and  spicy  smells  ;  anise,  lavender,  etc. 

(3)  Fragrant  scents.     Flower  odours ;  vanilla ;  gum  benzoin,  etc. 

(4)  Ambrosiac  scents.     Amber ;  musk. 

(5)  Alliaceous  scents.     Garlic,  asafoetida ;  bromine,  chlorine,  etc. 

(6)  Empyreumatic   scents.     Toast,  tobacco  smoke ;  naphtha,  etc. 

(7)  Hircine  scents.     Cheese,  sweat,  etc. 

(8)  Virulent  scents.     Opium,  cimicine,  etc. 

(9)  Nauseous  scents.     Decaying  animal  matter,  faeces,  etc. 

Not  all  of  these  can,  perhaps,  be  represented  in  the  laboratory 
(see  however,  p.  127  below).  The  following  list  will,  however,  be 
found  fairly  practicable.  The  letters  *e.  o.'  following  the  name 
of  the  substance  denote  *  essential  oil ' ;  L.  means  *  De  Laire 
specialty  *  (formula  unknown);  *t.'  means  'alcoholic  tincture'; 
and  *t.  a.,'  *  trade  article.*  Substances  grouped  by  Zwaarde- 
maker are  italicised.  The  others  have  been  classified  by  Dr. 
E.  A.  Gamble.  Disagreements  with  Zwaardemaker  are  indi- 
cated in  brackets. 

112 


§  30-    Otfactary  Sensation 


113 


maker's  Ust 


Aimo9utf  CO..    .     . 
AmdtTf  CO..     .     . 
Aminonium  sulphide 
Atme,  e.  o. 
Asafatida 
Aubcpinc  /-• 

BtMStMt       .      . 
BtHMMH       .... 

Bergamtoty  c  o.   .     • 
Birch,  e.  o.      .     ■ 
Butyric  ether      .     . 

Calamus,  c  o. 
Caraway,  c  o. 
Cardtm  disulphidt 

CaryopkyUitUj  L. 
Cassia,  e.  o.    .     . 
'^'t^esc,  stale  .     . 
mmamomy  c  o.  . 
Ci£ronella,  e.  o.  . 
Qematite,  L. 
CUn'es,  e.  o. 
Qymene,  / 
Cbcoa  buttt 
Coffee   . 
Cologne,  t.a. 
Coumarinej  L.     .     .     . 
Crab-apple  blossom,  t  a. 
Creosote     .... 

jbcbs,  e.  o.  .     . 
cummin,  e.  o.      .     . 
Cuir  de  Russie,  L.  . 
Ether,  sulphuric,  t.  a. 
Eucalyptus,  e.  o. 
Foul  alcohol  (poured 

specimen.*)      .     . 
Gar  III,  e.  o 

mm,  e-o. 

1  opine,  L 
Hemerocalle,  L 
J  acini  he,  L.    . 
Juniper,  c.o.  . 


off 


PlMIB 


(a)/. 
(4)«. 

(2)  Cy  a. 

(3)«- 
(6)^. 

(3)^. 
(2)  ^,  /9. 
(2)  ^,  iS- 

[(!)«?]. 

(2)  c,  p? 
(2)  <-,  a. 

[(9)^?]. 
(2)  dy  a. 

(2)  ^  )». 

(2)  d,  p. 
(2)  ^,  ^. 

(3)^- 

(2)  ^  a. 

(3)«. 
(2)^? 

(6)«. 
(3)^? 

(3)  ^,  /3. 
(6)^. 
(2)  b,  a, 
(2)  <:,  a. 

(4)^? 

(I)r. 

(2)«. 

(9). 7. 

(6)^. 

(2)  dy  a. 

(3)^- 

(3)  ^  *• 
(2)^,0? 


Lactic  add  .    . 
Laudamtmy  t. 
iMvender,  t.  o.  . 

Lemauy  e.  o. .     . 
Lilac,  t.  a.      . 
Methyl  alcohol  . 
Musky  t.  .     .     . 
Mustard,  e.  o.    . 
Nutmeg,  e.  o.     . 
Orange,  e.  o. 
Orris  ... 
Oxalic  ether .     . 
Parsley,  e.  o. 
Patchouliy  e.  o.  . 

Pennyroyal,  e.  o. 
Pepper,  e.  o. 
Peppermint,  e.  o. 
Pine  needles,  e.  o. 
Pyridine  .     .     . 
Quarantaine,  L. 
Rhubarb,  t.  .     . 
/^ose,  e.  o.     .     . 
Rosemary,  e.  o. . 
Rosewood,  e.  o.  . 
Rue,  CO. 
Sage,  c.  o.     .     . 
Sandalwood,  e.  o. 

Sassafras,  e.  o.  . 
Spearmint,  c  o. 
Syringa,  L.  .     . 
Tar     .     .     . 
Tea  . 

Thyme,  e.  o.  .     . 

Tobacco    . 
Valerian,  t 
lanillay  t.     . 
riolet,  t.  a.    .     . 
VVintergreen,  e.  o. 
VVych-hazel,  t  a. 
Yara  yara,  L.     . 


Plaotia 

ZwMRk- 

nuikcr't  Ust 
(pp.  933-*3i) 


(7)«. 
(8)  a. 
(2)r,  y; 
[(2)^?]. 
(2)  d,  p. 

(3)^. 
(6)^. 

(4)^. 
(2)^? 
(2)  b,  p. 

(2)  d,  p. 

(3)  ^  P- 
(i)c. 

(4)«. 
(2)  a; 

(2)  ^,  p. 
{2)b,a. 
{2)c,p. 
(2)  a. 
(6)  a. 

(8)^. 
(2)  d,  a. 
(2)  a. 
(2)  rf,  a. 
(2)  a? 
(4)^? 
(2)dyP; 
[(4)  ^?]. 

(2)     Cy    P? 

(2)  ^,  i8. 

(3)  ^.  )8. 
(6)^. 
(3)  ^  )8. 
(2)<r,  y; 
[(2)  «?]. 
(6)  a. 

(7)«. 

(3)  ^  P- 
(2)  O  )3. 

(2)«? 

(3)«? 


114  Olfactory  Sensation 

It  should  be  said  that  the  proposed  departures  from  Zwaarde- 
maker's  classification  are  based  upon  actual  confusions  found  in 
experimental  work.  Thus,  amber  and  patchouli  are  confused, 
as  are  thyme,  lavender,  pine  needles,  eucalyptus  and  rosemary, 
in  experiments  upon  smell  memory  and  recognition.  The  L, 
substances  are  usually  too  strong  for  work,  —  so  strong  as  to  be 
all  much  alike,  —  and  must  therefore  be  diluted. 

Literature.  —  On  olfactory  sensation  in  general,  see  Wundt, 
Phys.  Psych.,  i.,  1893,  441;  Kiilpe,  Outlines,  100;  M.  von 
Vintschgau,  Hermann's  Hdbch.  d.  Physiol.,  iii.,  2,  1880,  225  ; 
H.  Zwaardemaker,  Die  Physiol,  d.  Geruchs,  1895  ;  Titchener, 
Outline,  61  ;  Foster,  Textbook  of  Physiol.,  iv.,  1891,  1388. 


EXPERIMENT    XVH 

§  31.  The  Field  of  Smell.  —  It  may  be  said  at  once  that  the 
statement  in  the  text  "  It  [the  field  of  smell]  cannot  be  larger 
than  the  breathing  field,"  while  it  is  obviously  true,  may  not  be 
borne  out  by  the  results  of  this  experiment.  O  is  required  to 
smell  voluntarily,  />.,  to  sniff;  and  sniffing  expands  the  alae  of 
the  nostrils.  It  may  quite  well  be  the  case,  then,  that  the 
breadth  of  the  field  of  smell,  as  mapped  by  E^  is  slightly  greater 
than  the  breadth  of  the  field  of  breathing. 

An  objection  to  the  experiment  is  that  the  horizontal  arrange- 
ment of  tin  and  paper  offers  an  obstacle  to  free  inspiration,  while 
it  unduly  favours  the  taking-in  of  air  from  the  sides.  To  this 
Zwaardemaker  replies  (Physiol,  d.  Geruchs,  70)  —  and  the  author 
is  able  to  confirm  the  statement  —  that  the  fields  of  smell  are  not 
appreciably  larger  when  a  sheet  of  wide-meshed  gauze  replaces 
the  tin  or  paper.  Moreover,  inspiration  of  the  kind  required  is 
not  by  any  means  unnatural :  cf.  our  normal  smelling  of  a  flower, 
a  glass  of  wine,  or  a  plate  of  food  ;  or  a  dog's  following  of  a  trail. 

Preliminaries.  —  It  is  necessary  that  the  grip  of  the  teeth 
be  precisely  the  same  throughout  the  experiment.  The  paint 
line  may  be  marked  with  little  cross-lines,  indicating  the  posi- 
tion of  (9's  front  teeth  ;  or  the  tin  may  be  indented,  to  take  the 
teeth ;  or,  finally,  the  wax  may  be  left  in  place  from  one  experi- 
ment to  another.     Different  (9's  prefer  different  methods.     For 


Tkt  FUld  of  Smell  115 

paint,  use  'drop  black,'  a  dead-finish  paint  which  is  often  useful 
in  the  laboratory. 

Experiment  (i).  —  A  perfectly  normal  nose  is  rather  the  ex- 
ception than  the  rule.  E  must  not,  therefore,  be  surprised  at 
irregularities  in  the  outline  of  the  spots,  at  differences  of  size 
and  shape  as  between  the  right  and  left  areas,  at  the  occasional 
absence  of  the  oblique  cross-line,  etc.  Zwaardemaker  seems 
not  to  have  observed  this  last  anomaly  (p.  73):  it  has,  however, 
occurred  more  than  once  in  the  author's  experience.  Moreover, 
the  secondary  division  often  runs  down  and  out,  instead  of  down 
and  in.  Dr.  Gamble  writes  to  the  author:  "A  very  large  num- 
ber of  my  records  (and  I  have  now  examined  the  breathing  spots 
of  more  than  100  people),  though  not,  I  think,  the  majority, 
show  the  secondary  division  at  right  angles  to  the  normal." 

Experiment  (2).  —  The  need  of  strict  control  of  the  smell 
stimulus  cannot  be  too  strongly  impressed  upon  the  student. 
The  syringe  must  be  perfectly  oil-tight,  and  perfectly  free  from 
odour  when   the   point   of 
the  needle  is  closed.     Af- 
ter, say,  every  eight  tests, 
the  room  in  which  the  ex- 
periment is  performed  must 
be  thoroughly  aired.      On 
the  other  hand,  doors  and 
windows   must   be  tightly 

closed     during     the     tests.  Posterior 

since  even  a  slight  draught      Fig.  12.  -  Normal  breathing  »poU  (Zwaarde- 
•  11  •  J        ui        1  maker).     The  diagram  is  printed  upside- 

Will  very  considerably  de-        ^^^^  \^  ^^^  p^yfj^,  ^  ^^.^.h.,  p.  72; 
range   the   field   of  smell.        cf.  the  text  of  pp.  72  f. 
If  the   field   of   smell   ex- 
tends beyond  the  field  of  breathing  on  one  side,  or  runs  into 
the  intermediate   area  in  one  direction,   there   is   probably  a 
draught  at  work.      The  place  of  the  apparatus  in  the  room 
should  then  be  changed. 

It  may  be  necessary  to  make  a  series  of  preliminary  experi- 
ments, in  order  roughly  to  determine  the  liminal  stimulus,  i>., 
the  movement  of  the  syringe-piston  which  just  gives  rise  to  a 
sensation  of  determinate  quality,  in  the  middle  region  of  the 


Ii6 


Olfactory  Sensation 


smell  field,  during  the  2  sec.  limit.  This  movement  has  varied, 
in  the  author's  experiments,  between  2  and  7  mm.  The  rate  of 
pushing  the  piston  must  be  kept  as  constant  as  possible,  as  well 
as  the  distance  of  push  and  the  time  of  exposure  of  the  needle 
point. 

Note  that  the  ready-signal  is  to  be  given  after  the  needle  has 
pierced  the  paper.  Otherwise,  the  noise  of  the  prick  may  dis- 
tract (7's  attention  from  the  scent.  To  avoid  fatigue,  it  is  well 
to  take  only  eight  tests  in  a  series,  and  to  distribute  these,  four 
to  each  nostril,  in  irregular  order.  The  exploration  of  the 
breathing  field  must  also  be  entirely  irregular. 

Results.  —  The  following  diagrams,  imperfect  as  they  are, 
represent  the  average  result  attainable  in  the  limited  time  that 


can  be  given  to  the  experiment.  In  Fig.  13,  the  secondary  divi- 
sions are  at  right  angles  to  the  normal ;  in  Fig.  14  no  secondary 
division  could  be  found.  The  positive  errors  (sensations  where 
there  should  have  been  no  sensation)  were  in  nearly  every  case 
explicable  (after  the  event !)  by  draughts :  it  must  be  remem- 


§  3»-    Tk4  FUld  of  SmeU 


"7 


bered  that  any  considerable  movement,  say,  of  head  or  arm,  on 
the  part  of  E  or  of  O^  sets  up  air-currents  in  the  experimenting 
room.  The  negative  errors  can  be  explained  only  conjecturally. 
Questions. — (i)  Not.  at  any  rate,  for  all  (9*s.  There  are,  in 
very  many  cases,  patches  where  •  something  *  is  smelled,  which 
is  not  distinctly  oil  of  cloves.     This  change  of  quality  must 


Fia  14. 


apparently  be  attributed  to  a  change  in  local  sensitivity  of  the 
olfactory  mucous  membrane. 

(2)  The  field  of  smell  is  the  smaller  of  the  two.  In  a  per- 
fectly conducted  experiment,  it  would  correspond  to  the  antero- 
median portions  of  the  breathing  field.  The  possibly  greater 
breadth  of  the  field  of  smell  has  already  been  remarked  on  and 
explained  (p.  1 14). 


Ii8  Olfactory  Sensation 

Beyond  the  breathing  field  there  is  no  smell.  Nor  do  smell 
sensations  come  from  the  intermediate  strip  that  corresponds  to 
the  septum,  or  from  the  strips  that  divide  the  anteromedian 
from  the  posterolateral  portions  of  the  breathing  field. 

(3)  To  avoid  the  diffusion  error.  If,  e.g.,  the  needle  point  be 
held  for  some  little  time  close  to  the  lips  (a  point  from  which 
no  sensation  of  smell  can  properly  be  set  up),  the  oil  of  cloves 
volatilises,  and  the  vapour  in  ascending  strikes  the  breathing 
cone  at  an  angle.  The  olfactory  stimulus  is  thus  sucked  into 
the  inspiration-current,  and  will  presently  arouse  an  olfactory 
sensation. 

Zwaardemaker  (p.  69)  recommends  a  stimulus-time  of  i  sec. 
This  answers  with  practised  6>'s  ;  for  unpractised,  it  is  too  short. 

(4)  These  have  been  mentioned  above.  They  are :  diffusion 
of  the  stimulus  in  the  room,  whether  by  carelessness  on  the  part 
of  Ey  by  draughts,  by  an  overlong  working  without  change  of 
air,  or  by  overlong  exposure  in  a  single  experiment ;  unequal 
stimulation,  due  to  variation  in  the  rate  or  distance  of  push  of  the 
piston ;  fatigue  on  the  part  of  O ;  too  vigorous  sniffing ;  sugges- 
tion or  distraction  by  the  sound  of  the  needle-prick  in  the  paper. 

(5)  See  Zwaardemaker,  Physiol,  d.  Geruchs,  chs.  iii.,  iv.,  esp.  72  f. 

(6)  In  ordinary  life  we  move  the  head  in  all  directions,  and 
are  constantly  in  draughts,  or  are  creating  draughts  by  our 
movements.  Moreover,  the  cross-section  of  the  breathing  cones 
in  this  experiment  is  taken  very  near  their  vertices. 

Related  Experiment.  —  The  statement  that  the  field  of 
smell  "may  be  coincident  with  ...  or  may  be  smaller  than  the 
field  of  breathing  "  presupposes  (?'s  ignorance  of  a  simple  but 
striking  experiment  (Pick)  in  the  sphere  of  olfaction.  It  is  as 
follows.  Introduce  an  olfactory  stimulus  —  e.g.,  the  pointed  end 
of  a  paper  funnel  held  over  some  scented  object  —  into  the  pos- 
terior half  of  the  nostril,  and  you  smell  nothing  at  all ;  shift  the 
stimulus  to  the  anterior  half  of  the  nostril,  and  you  get  an  inten- 
sive smell  sensation.  It  follows  from  this  experiment  that  the 
field  of  smell  must  be  smaller  than  the  inspiration  field. 

Literature.  —  A.  Pick,  Anatomic  u.  Physiologic  d.  Sinnes- 
organe,  1864,  99;  H.  Zwaardemaker,  Die  Physiol,  d.  Geruchs, 
1895,  69  ff. 


$  33.   Smtii  Exkaustum  119 

BZpmMBHT  xym 

$  32.  Th0  OlfaetoryQiuaitiM:  Method  of  Bxhanition.  —  All  of 
the  foregoing  experiments  ought,  in  the  present  state  of  our 
knowledge,  to  be  carried  out  in  quantitative  terms ;  that  is  to 
say,  they  should  be  performed  with  the  Zwaardemaker  olfac- 
tometer, in  one  form  or  other,  with  standardised  stimuli  and  with 
known  intensities  of  the  stimuli  But  olfactometric  technique 
— again,  in  the  present  state  of  our  knowledge  —  is  so  circum- 
stantial and  time-taking  that  insistence  on  this  point  would 
imply  neglect  of  other  equally  important  experiments  in  other 
sense  departments.  It  has  therefore  seemed  best,  especially  as 
the  olfactometer  must  be  employed  in  the  following  Experiment, 
to  give  the  tests  in  rough  form.  The  following  hints  will  be 
enough  to  guide  the  Instructor,  in  case  any  student  shows  a 
special  aptitude  or  desire  for  olfactometric  work. 

Experiments.  —  {a)  Take  cylinders  of  beeswax  and  tolu  bal- 
sam, which  are  decidedly  exhausting,  and  of  grey  india  rubber 
and  tallow,  which  are  not  particularly  so,  and  work  out  the 
experiment  described  by  Zwaardemaker  on  p.  204  of  the  Physiolo- 
giedesGeruchs  (paragraph  beginning  "Bedienen  wir  uns  .  .  ."), 
platting  curves  like  those  on  p.  205.  Where  the  adhesion  error 
enters,  a  clean  inhaling  tube  should  be  used  for  each  determina- 
tion of  the  limen.  Two  clinical  olfactometers  and  a  supply  of 
tubes  must  therefore  be  on  hand. 

(b)  Secure  complete  exhaustion  with  different  intensities  of 
the  same  quality,  using  the  cylinder  on  the  instrument  during 
the  exhaustion  process.  Plat  curves,  with  the  durations  of  the 
odour  for  ordinates,  and  the  intensities  of  stimulus  for  ab- 
scissae. 

(c)  The  recuperation  experiment  could  be  made  on  the  olfac- 
tometer with  one  or  two  qualities,  and  one  or  two  intensities  of 
the  same  quality.  Curves  should  be  platted,  with  the  durations 
of  the  smells  for  ordinates,  and  the  numbers  of  the  exhaustions 
for.  abscissae. 

If  the  whole  cylinder  is  used  to  exhaust,  it  may  be  taken  off 
the  olfactometer.  When  only  a  part  of  the  cylinder  is  used,  — 
reduced  intensity  of  the  quality,  —  the  cylinder  should  be  slipped 


I20  Olfactory  Sensation 

over  a  clean  inhaling  tube  during  each  interval  of  rest,  to  avoid 
the  adhesion  error. 

(//)  The  main  experiment,  that  upon  the  determination  of  the 
elementary  qualities  by  the  exhaustion  method,  should  be  per- 
formed systematically  with  the  olfactometer,  —  Zwaardemaker's 
localisation  theory  (Physiol,  d.  Ger.,  p.  271)  being  taken  as  a 
working  hypothesis. 

But — the  caution  may  be  repeated  —  work  of  this  kind  requires 
more  time  than  can  usually  be  allowed  to  Smell  in  a  drill  course. 
We  have  here  nothing  that  cotresponds  in  ease  and  accuracy  of 
manipulation  to  the  rotating  discs  of  Optics. 

The  main  objective  source  of  error  in  the  experiments  of  the 
text  is  the  propagation  of  the  scents  by  diffusion.  The  phials 
must  always  be  carefully  stoppered,  except  when  in  use.  The 
scents  must  be  stored  in  a  room  or  closet  away  from  the  experi- 
menting room,  and  this  room  or  closet  must  be  ventilated  by  a 
through-draught.  Phials  should  be  brought  into  the  experiment- 
ing room  as  wanted,  not  all  together.  The  experimenting  room 
itself  should  be  well  ventilated.  All  smell  work  should,  by 
rights,  be  done  in  a  room  with  walls,  etc.,  of  glazed  tile ;  at  any 
rate,  the  walls  and  ceiling  should  be  covered  with  glazed  paper, 
and  the  floor  with  varnished  linoleum,  the  proper  smell  of  which 
has  worn  off.  If  these  conditions  cannot  be  realised,  recourse 
must  be  had  to  frequent  and  thorough  ventilating. 

If  the  students  are  entirely  unfamiliar  with  the  properties  of 
smell  stimuli,  a  few  preliminary  demonstrations  may  be  given 
without  waste  of  time. 

(^)  Leave  a  phial  of  oil  of  cloves  open  in  a  closed  room. 
After  two  minutes,  open  the  door  of  the  room,  and  let  the 
student,  standing  at  the  door,  take  two  breaths  of  the  diffused 
scent.  Now  close  the  room  for  another  three  minutes.  Repeat 
the  test.     Note  the  increased  intensity  of  the  odour. 

{b)  Compare  the  power  of  three  drops  of  oil  of  cloves  to  scent 
a  room,  (i)  when  they  are  at  the  bottom  of  a  phial,  and  (ii)  when 
they  are  smeared  upon  the  surface  of  a  plate. 

{c)  Note  the  difference  in  the  intensity  of  the  smell  of  bees- 
wax, or  of  the  pasteboard  or  leather  covers  of  books,  in  damp 


§  32.   Smgil  Exhaustion  121 

and  in  dry  weather,  or  in  the  moist  and  dry  atmosphere  of  a 
room. 

(1/)  Note  the  difference  in  the  intensity  of  the  smell  of  gum 
benzoin  in  a  warm  and  a  cold  room. 

(r)  The  fact  of  exhaustion  can  be  brought  out  very  prettily 
ms  follows.  Procure  two  flowers,  —  two  roses,  or  carnations,  or 
sprigs  of  heliotrope,  —  as  nearly  as  possible  of  the  same  size. 
Let  O  assure  himself,  by  a  single  sniff,  that  both  give  out  a 
strong  perfume.  Now  let  him  take  one  of  the  two  (by  prefer- 
ence the  smaller,  if  there  is  any  difference  of  size),  and  smell 
hard  at  it  for  a  few  inhalations.  Then  let  him  smell  at  the 
larger.  The  latter  will  give  forth  very  little,  if  any  scent.  The 
test  is  more  striking  in  the  performance  than  in  the  reading. 

Experiment  (i).  —  Some  little  practice  —  not  much  —  is 
needed  for  the  regulation  of  breathing  in  this  experiment ; 
rather  more,  for  the  determination  of  the  exact  time  at  which 
exhaustion  has  set  in.  The  following  are  typical  results  :  those 
in  brackets  are  taken  from  Aronsohn. 


1. 

Crab-apple  blossom 

2  min.  to  3  min. 

3. 

White  roM 

I  min.,  30  sec.  to  2  min. 

3- 

Heliotrope 

4  min.  to  6  min. 

4- 

Ammonium  sulphide 

6  min.  (4  to  5  min.) 

5 

Carbon  disulphide 

5  min.  to  5  min.,  30  sec. 

6. 

Asafoetida 

I  min.,  30  sec.  to  i  min.,  55  sec 

7. 

Stale  cheese 

7  min.,  45  sec.  to  8  min.,  30  sec 

8. 

Tincture  of  iodine 

1  min.,  30  sec  to  2  min.,  15  sec  (4  min.) 

9- 

Spirits  of  camphor 

I  min.,  45  sec.  to  2  min.,  45  sec. 

Other  results  will  be  found  in  Aronsohn,  p.  343.  —  In  one  test 
with  white  rose,  O  exhaled  partly  through  the  mouth,  but  partly 
also  through  the  plugged  nostril.  The  exhaustion  time  rose 
to  8  min.,  10  sec.  — Some  odours  are  very  irritating,  and  their 
irritation  persists  after  the  nose  is  exhausted  for  the  scent. 
This  is  the  case,  e.g.,  with  eau  de  Cologne,  and  with  the  helio- 
trope of  the  above  list.  The  limit  of  exhaustion  is,  in  such 
cases,  difficult  to  determine.  —  The  carbon  disulphide  produces 
a  drowsiness  or  dizziness,  which  is  not  at  all  unpleasant,  but 
again  makes  the  limit  of  exhaustion  difficult  to  settle.  —  Practice 


122  Olfactory  Sensation 

reduces  the  exhaustion  time.  The  first  two  determinations  for 
spirits  of  camphor  (lo  parts  camphor,  70  alcohol,  20  water)  were 
5  min.,  30  sec.  and  7  min.  These  values  resemble  those  of 
Aronsohn  (5  to  7  min.)  for  0.5  to  o. I  cc.  camphor  and  100  cc. 
of  0.6  %  salt  solution.  After  practice,  the  exhaustion  times 
remain  fairly  constant. 

Experiment  (2).  —  Good  scents  for  this  purpose  are  : 

(i)  Nitrobenzole  (nitrobenzene,  essence  of  mirbane).  This 
gives  a  momentary  whiff  of  heliotrope.  Then  follows  the  scent 
of  bitter  almonds.  After  four  or  five  breaths,  the  bitter-almond 
scent  has  altogether  disappeared,  and  a  scent  is  left  which  more 
or  less  resembles  that  of  grey  india-rubber  tubing  or  benzine. 

(ii)  Benzoyl  chloride.  A  very  small  quantity  of  this  suggests, 
for  the  first  few  seconds,  flower  fragrance.  The  associations 
with  the  smell  are  usually  indefinite :  the  smell  is  puzzling. 
Very  soon  there  emerges  simply  a  pronounced  scent  of  bitter 
almonds. 

(iii)  Propionic  acid.  The  scent  of  a  trace  of  this  liquid  is  a 
mixture  (entirely  unitary  at  first)  of  the  scents  of  acetic  acid 
and  butyric  acid.  After  a  few  breaths,  the  scent  of  acetic  acid 
disappears,  and  only  the  unpleasant  fatty-acid  smell  is  left. 

(iv)  Faded  violets.  The  scent  is,  again,  '  mixed '  at  first,  though 
quite  unitary :  it  is  a  mixture  of  the  scent  of  violets  (as  we  have 
that  scent  in  perfumes)  with  the  scent  of  faded  flowers.  After 
a  few  breaths  we  have  nothing  but  the  repellent  smell  of  faded 
flowers. 

(v)  Heliotropine.  Heliotrope  is  smelled  only  for  a  few  sec- 
onds ;  the  following  scent  is  that  of  bitter  almonds.  —  Helio- 
tropine probably  contains  nitrobenzole,  q.v.  A  solution  of 
heliotropine  in  odourless  paraflfin  gives  no  final  benzine  scent. 

(vi)  Oil  of  camphor.  For  the  first  whiff  or  two,  we  have  the 
scent  of  turpentine.     This  gives  way  to  a  nutmeg  odour. 

(vii)  Oil  of  mace  (solid)  smells  at  first  like  nutmeg,  and  then 
like  barn-yard  manure.  Cf.  the  peculiar  odour  of  putrefaction 
which  even  freshly  picked  lilac  blossoms  give  in  large  masses 
indoors. 

(viii)  Mutton  tallow,  if  persistently  smelled,  yields  an  onion- 
like scent. 


§  32.   SmtU  Exhaustion  123 

(ix)  In  practically  every  alcoholic  solution,  the  smell  of  the 
alcohol  comes  out»  at  the  expense  of  the  original  odour,  if  one 
smells  it  long.  E\'en  vanilla  ice-cream,  if  it  is  over-flavoured, 
seems  to  '  taste  of  whiskey.' 

The  following  Nidations  of  this  experiment  are  worth  making. 

(i)  Familiarise  O  with  the  smells  of  the  aqueous  solutions 
of  coumarine  and  vanilline.  —  Mix  the  solutions  in  such  propor- 
tions that  only  the  vanilline  can  be  smelled  by  O.  Now  let  him 
exhaust  his  nostril  for  the  pure  vanilline  solution.  This  done, 
let  him  smell  the  mixed  solution.  The  liquid,  which  originally 
smelled  only  of  vanilline,  now  smells  only  of  coumarine. 

(ii)  Mix  the  aqueous  solutions  of  coumarine,  naphthaline  and 
\*anilline,  in  such  proportions  that  at  first  smell  the  scent  of  the 
mixture  is  dififerent  from  that  of  any  one  of  the  primary  quali- 
ties. Let  O  smell  the  mixture  continuously.  Very  soon  an 
oscillation  of  qualities  arises:  some  one  of  the  components  is 
smelled  for  a  moment  by  itself,  and  then  disappears  to  make 
way  for  another.  Presently  either  naphthaline  or  coumarine 
goes  out  altogether,  i.e.,  ceases  to  appear  in  the  oscillations. 
Then  a  second  quality  (coumarine  or  naphthaline)  disappears, 
and  only  the  vanilline  is  left. 

The  certainty  and  regularity  of  results  in  work  of  this  kind 
are  greatly  increased  if  O  is  familiar,  beforehand,  with  the  scents 
which  he  is  to  smell  out  from  the  mixed  odour :  just  as  the 
hearing-out  of  an  overtone  from  a  clang  is  greatly  facilitated 
by  the  separate  sounding,  beforehand,  of  that  particular  tonal 
quality.  Hence  it  is  well,  after  the  first  experiment  has  been 
made,  to  encourage  O  to  identify,  name,  the  partial  scents  that 
he  has  smelled;  and  then  to  repeat  the  test  a  few  times  over, 
in  the  light  of  this  knowledge,  taking  the  mean  and  the  mean 
variation  of  the  times  of  change. 

If  such  identification  is  impossible,  —  and  it  is  for  some 
observers,  scents  being  such  intangible  and  elusive  things,  and 
things  so  little  operated  with  in  ordinary  ideation,  —  the  results 
of  the  experiment  may  be  checked  by  noting  (a)  that  the  times 
of  change  still  agree  roughly  for  different  observers,  and  {b)  that 
the  number  of  changes  is  constant,  from  one  fairly  practised 
observer  to  another. 


124 


Olfactory  Sensation 


Experiment  (3),  —  The  following  are  typical  series  : 


Tincture  or  Iodink. 

Sec. 

Exhaustion  time 115 

"          "    after  first  i  min.  rest 

.       60 

"          "       "     second  i  min.  rest  . 

.       50 

"          "       "     third  I  min.  rest     . 

.       38 

"          «       "     fourth  I  min.  rest  . 

•       29 

"          «       "     fifth  I  min.  rest      . 

•      37 

"          «       "     sixth  I  min.  rest     . 

•      37 

"          "       "     seventh  i  min.  rest 

•      33 

"          "       **     eighth  I  min.  rest  . 

•      30 

"           "       "     ninth  i  min.  rest    . 

21 

"          "       "     tenth  I  min.  rest    . 

.      19 

"          "       "     eleventh  i  min.  rest 

•       13 

"           "       "     twelfth  I  min.  rest  . 

•      13 

"          "       "     thirteenth  i  min.  rest 

8 

Spirits  of  Camphor.                                                                                             Sec. 

Exhaustion  time 105 

"          "    after  first  2  min.  rest 

69 

"           "       "     second  2  min.  rest . 

•      52 

"           "       "     third  2  min.  rest     . 

.      46 

"        ■  "       «     fourth  2  min.  rest  . 

.      38 

"          «       "     fifth  2  min.  rest      . 

46 

"          "       "     sixth  2  min.  rest      . 

32 

"          "       "     seventh  2  min.  rest 

34(?) 

"          "       "     eighth  2  min.  rest  . 

22 

"          "       "     ninth  2  min.  rest    . 

25 

"          "       "     tenth  2  min.  rest    . 

17 

«          "       «     eleventh  2  min.  rest 

24(?) 

"          "       "     twelfth  2  min.  rest . 

17 

"          «       "     thirteenth  2  min.  rest      . 

17 

"          «       "     fourteenth  2  min.  rest     . 

12 

"          "       "     fifteenth  2  min.  rest 

8 

Others  will  be  found  in  Aronsohn,  pp.  344-346. 


{  32.    Smeli  Exhaustion 


125 


Experiment  (4).  —  The  following  are  typical  results.  The  + 
indicates  a  positive  rejudg^ent  under  the  heading  of  its  column 

S»  strong,  WaB  weak,  Oano  8cent)i  The  asterisk  indicates 
Aronsohn's  results  with  the  same  stimuli  (p.  347):  where  the 

vlentity  of  the  stimulus  is  doubtful,  the  asterisk  is  enclosed  in 
brackets.  The  obelisk  indicates  a  few  results,  from  another  O, 
which  differed  from  those  of  the  proper  O  of  the  Table. 


EXMAUtnON  BY  lODINB. 

ExMAUmON  BY  CAMrMOB. 

StlMOLOS. 

S 

w 

0 

s 

w 

0 

CM.  petroselini 

•  + 





+ 

-t 



Coumarin 

— 

+ 

— 

— 

+ 

OL  terebinth 

+ 

•t 

— 

— 

-f 

-t 

01.  caryophyllonim     .... 

— 

•+ 

— 

+ 

— 

— 

01.  cajeputi  .     .     . 

•  + 

— 

— 

— 

+ 

— 

Flower  perf.  jasmin* 

+ 

— 

— 

— 

+ 

— 

01.  nita?   .     . 

• 

+ 

— 

— 

+ 

— 

01.  pinus  picca 

— 

+ 

— 

— 

+ 

— 

01.  la\*and.  gallic 

0  + 

— 

— 

— 

+ 

— 

01  bergamottx 

•+ 

— 

— 

+ 

— 

£au  de  Cologne 

— 

+ 

— 

— 

+ 

— 

01.  saK-ia      .     . 

+ 

• 

— 

+ 

— 

— 

01.  copaivac  .     . 

— 

+ 

♦ 

— 

+ 

— 

01.  juniperi  .     . 

— 

+ 

— 

— 

+ 

— 

01.  roaddis  . 

— 

*+ 

— 

+ 

— 

— 

01.  foeniculi  . 

•  + 

— 

— 

— 

+ 

— 

01.  dtri 

— 

•+ 

— 

— 

+ 

-— 

Musk  (natur.)    . 

— 

+ 

— 

+ 

— 

— 

Flower  perf.  neroli 

— 

+ 

— 

+ 

— 

— 

01.  aurant.  dulc.      . 

— 

— 

+ 

— 

+ 

— 

Heliot  rapine 

— 

— 

+ 

— 

— 

+ 

01.  anisi  stellati      .     . 

+ 

— 

— 

+ 

— 

Fl.  perf.  ylang  ylang  . 

— 

— 

+ 

— 

— 

01  carvi'.     .     .     . 

— 

+ 

— 

+ 

— 

— 

Fl.  perf.  hvadnth   . 

— 

+ 

— 

+ 

— 

•— 

Alcohol,  95% 

— 

— 

•+ 

— 

— 

+ 

01  mirrini    ... 

•  + 

— 

— 

+ 

— 

— 

01.  rosmarini  gallic 

(•)  + 

— 

— 

— 

+ 

— 

Ether 

•  + 

^^ 

~~ 

^~ 

+ 

"■" 

126 


Olfactory  Sensation 


The  following  Table  shows,  somewhat  more  fully,  the  results 
obtained  from  another  O. 


Stimulus. 


Previous  Tudg< 

ment  of  O 
•s  to  Intensity 
of  Stimulus. 


Exhaustion  by 


Iodine. 


W 


Camphor. 


W 


CI.  cajeputi 

Flower     perf. 

jasmine 
of.  rutae 
Ol.  pinus  picea 

Ol.  copaiTZ 

OI.  juniperi 

Ol.  macidis 

Ol.  foeniculi 

Ol.  citri 

Musk  (natur.) 

Flower    perf. 

neroli 
Ol.     aurant. 

dulc. 
Vanilline 
Ol.  succini 
Musk  (artif  ) 

01.   rosmarini 

gallic. 
Heliotropine 

Ol.  anisi  stel> 

lati 
Flower     perf. 

ylang  ylang 
Ol.  carvi 
Flower     perf. 

hyacinth 
Ol.  lavandulac 

gallic. 
Ol.  bergamot- 

t2 

Eau  de  Co- 
logne 
Ol.  salvias 
Alcohol  95  % 
Ol.  petroselini 
Ol.  terebinth. 
Ol.  caryophyl- 

lorum 
Ether 


Moderate 

Heavy  and 

strong 
Strong 
Weak 

Rather  strong 

Rather  strong 

Weak  and  pene- 
trating 
Rather  strong 

Moderate 

Strong  and 

heavy 
Rather  strong 

Moderate 

Moderate 

Strong 

Weak 

Strong 

Weak 

Rather  strong 

Moderate 

Moderate 
Strong 

Moderate 

Weak  and 

sweet 
Weak 

Strong 

Weak 

Moderate 

Strong 

Strong 


Strong 


*  Rather 
strong 


Same 

♦Same 
(*)  Same 


(♦)Same 

Same 
♦Weak 

Strong 


Faint 
Moderate 


Rather 
weak 

Rather 
weak 

Very 
weak 


'  Weaker 
Moderate 


Very 

weak 
Weak 

Very 
weak 


Very 

faint 
Rather 

faint 
Faint 


Moderate 


♦  Weaker 


♦Weak 
♦Weak 


Nothing 


Nothing 

Nothing 
♦  Nothing 


Strong 


Same 


Same 


Same 
Same 


Same 
Same 


Same 

Weak 

Quite 
strong 


Very 

faint 
Faint 

Moderate 
Very 

faint 
Very 

weak 
Very 

weak 


Weak 

Rather 

weak 
Still 
strong 


Weaker 


Moderate 
Very 
weak 


Weak 

Weaker 

Very 
weak 

Welk 

Not  so 
strong 


Nothing 


Nothing 


Nothing 


These  two  Tables  do  not  agree  in  every  instance,  but  they 
agree  in  the  great  majority  of  instances.     We  are  fortunately 


$  32-   Smttl  Exkaustian  127 

able  to  compare  16  of  the  results  of  each  Table  with  results  given 
by  Aronsohn.    The  outcome  i> ; 

Table    I.    AgreemcDts    12  DisagreemenU    4 

Tabic  II.  **  13  **  3 

It  is  noteworthy,  further,  (i)  that  the  disagreements  from 
Aronsohn  are  in  no  case  extreme,  f>.,  in  no  case  fall  outside 
of  a  neighbouring  category,  though  they  might  have  done  so 
twice  in  Table  I.  and  once  in  Table  II.;  and  (2)  that  all  three 
exceptions  of  Table  II.  are  confirmed  by  the  judgments  of  Table  I. 

The  outcome  of  the  experiment  is  that,  during  exhaustion  of 
the  organ  for  a  given  stimulus,  a  certain  number  of  stimuli  are 
still  smelled  at  full  intensity,  certain  others  arouse  a  sensation 
of  distinctly  less  intensity,  and  others  again  are  not  sensed  at  all. 

The  following  materials  (including  odours  from  all  Zwaarde- 
maker's  classes)  are  recommended  for  this  experiment 

I.   (a)  Confectioners'  *  pineapple  oU.^ 

(b)  Beeswax. 

(c)  Sulphuric  ether. 

n.  (a)  Rosemary,  e.  a 

(b)  o.  Qoves,  e.  o. 

fi.  Cinnamon,  e.  o. 

(c)  o.  Anise,  e.  o. 

p.   Peppermint,  e.  o. 

y,  Thj-me,  e.  o.  (according  to  Z). 

(d)  cu  Geranium,  e.  o. 
/3.   Bergamot,  e.  o. 

(e)  Almond,  e.  o. 

III.  (a)  a.  Ylangylang 

/9.  Orange  blossom 

(b)  a.   Jonquille 
p.  Violet 

(c)  Common  benzoin,  the  liquid. 

IV.  (a)  Oil  of  amber. 

(b)  Musk  (the  tincture  of  natural  animal  musk,  or  the  root). 

V.   (a)  Carbon  disulphide  (much  cheaper  than  allyl  sulphide)  or  asa- 
foetida. 

(b)  A  bit  of  strong  dried  fish,  crumbled. 

(c)  Dilute  bromine,  the  alcoholic  ( ?)  tincture. 


the  common  perfumes. 


128  Olfactory  Semation 

VI.    (a)  Creosote, 
(b)  Benzine. 

VII.    (a)  Caproic  acid  or  stale  cheese. 

(b)  Root  and  stem  of  barberry  or  black  currant 

VIII.    (a)  Laudanum. 

(b)  Olive  oil,  poured  off  from  bed-bugs  or  squash-bugs. 

IX.   (a)  Alcohol  from  half-decomposed  vertebrate  zoological  specimens 
(not  fish  !),  or  water  from   wilted  flower  stems.      Stapelia 
blossoms  (carrion  flowers)  can  also  be  used. 
(b)  Stinkhorns  (Phallus  impudicus)  ;  in  alcohol,  if  necessary. 

The  author  is  unable,  at  present,  to  give  the  concentrations 
proper  for  quantitative  work.  In  II.  (d)  a  rose  would  be  prefer- 
able to  geranium,  but  is  very  expensive.  Bergamot  is  less  like 
geranium  than  citronella,  and  has  a  more  marked  scent  than 
lemon.  As  for  III.,  it  seems  to  be  almost  impossible  to  procure 
in  the  American  market  a  scent  made  from  the  real  flowers;  the 
pomades  are  more  likely  than  the  perfumes  to  approximate  to  the 
real  flower  odour.  If  one  must  use  the  *  chemical '  compounds, 
there  seems  to  be  no  good  reason  against  taking  those  that  are 
cheap  and  easy  to  get.  On  the  one  hand,  if  the  common  per- 
fumes are  dropped  on  cotton  wool,  the  alcohol  smell  will  disap- 
pear, and  the  flower  odour  will  be  left  fairly  pure.  On  the  other, 
the  De  Laire  specialties  are  (as  was  remarked  above)  overpower- 
ingly  intensive,  and  the  proper  concentrations  are  hard  for  a 
novice  to  work  out.  Moreover,  their  scent  is  apt  to  *  get  all 
over*  the  laboratory. 

The  substances  mentioned  by  Zwaardemaker  under  V.  (b)  have 
various  drawbacks  :  some  are  poisonous,  some  very  inflammable, 
some  almost  impossible  to  procure.  For  (c)  bleaching  powder 
and  tincture  of  iodine  may  be  tried.  The  bleaching  powder  has 
the  advantage  of  eliminating  the  alcohol.  Bromine  seems,  upon 
the  whole,  to  be  the  least  irritating  of  the  three. 

Questions. — (i)  The  result  is,  that  the  organ  of  smell  can 
be  entirely  exhausted  by  an  adequate  stimulus,  within  the  space 
of  a  few  minutes ;  and  that  an  organ  thus  exhausted  requires  at 
least  a  minute  for  complete  recovery.  Both  propositions  hold 
for  us,  of  course,  only  within  the  limits  of  our  experiments. 


§  32.    Smeli  Exhaust WH  129 

The  fact  of  exhaustion  is  no  novelty.  We  find  it,  e.g.,  playing 
a  great  part  in  temperature  work  on  the  skin,  and  in  taste  ex- 
periments on  the  fungiform  papillae.  The  completeness  and  the 
permanency  of  smell  exhaustions  are  striking,  because  we  are 
attacking  the  organ,  as  we  think,  in  the  gross,  —  whereas  we 
arc  attacking  but  a  single  element  of  the  skin  or  of  the  tongue. 
Really,  however,  as  exp.  (4)  shows,  we  have  not  wearied  the 
whole  organ,  but  only  some  part  or  parts  of  it. 

The  reason  for,  or  explanation  of,  the  phenomena  seems  to 
be  that  they  are  not  phenomena  of  *  exhaustion  *  at  all,  but  phe- 
nomena of  adaptation.  Just  as  Hering's  theory  has  substituted 
the  concept  of  adaptation  for  that  of  retinal  fatigue  in  the  case 
of  after-images,  etc.,  so  here  it  seems  probable  that  we  are  in 
face  of  local  adaptations  of  the  organism  to  its  environment, 
rather  than  of  a  mere  giving-out  under  excessive  stimulation. 
The  teleological  significance  of  such  adaptation  is  obvious. 

If  we  cling  to  an  explanation  in  terms  of  exhaustion  proper,  we  must  reason 
that  it  is  not  the  greater  but  the  smaller  liability  to  exhaustion  of  the  sense- 
organs  that  has  to  be  accounted  for.  The  more  primitive  the  organ,  the  more 
exhaustible  would  it  be.  Smell,  taste  and  the  temperature  sense,  develop- 
ments from  the  *  chemical  ^  sense  of  the  lowest  forms  of  life,  still  show  phe- 
nomena of  exhaustion ;  sight  and  hearing  have  come  to  possess  a  greater 
endurance,  because  they  must  be  always  '  on  the  stretch '  for  the  avoidance 
of  enemies. 

If  it  be  objected  that  certain  animals  use  the  sense  of  smell  to  find  their  food 
and  their  mates  and  to  avoid  their  foes,  the  reply  is  that  we  do  not  know  that 
their  sense-organs  are  so  readily  exhausted  as  our  own.  The  human  organ 
may  have  regressed,  from  lack  of  use,  to  a  primitive  state  of  ready  exhaustion. 
Note  that  Zwaardemaker  denies  the  phylogenetic  value  of  smell  as  a  guardian 
of  respiration  (Phys.  d.  Gcr.,  10  t). 

(2)  The  mixed  smells  may  be  compared  (<i)  to  the  mixtures 

f  qualities   from  the  black-white  and  colour  series  in  vision 

:>inks,  browns,  etc.);  (b)  to  the  fusions  of  smell  and  taste  which 

'.  c  have  already  noted  ;  (c)  to  the  '  heat '  perception,  obtained  by 

the  fusion  of  warm  and  cold ;  {d)  to  taste  fusions,  such  as  *the 

taste  of  lemonade  '  (sweet  and  sour).     There  are  probably  other 

instances,  but  these  are  the  most  obvious.     It  should  be  noted 

that  the  sight  fusions  differ  from  the  rest,  in  that  we  cannot  get 

both  the  components  of  the  mixture  separately :  we  can  get  a 


I30  Olfactory  Sensation 

brightness  quality  without  colour-tone,  but  never  a  colour-tone 
without  brightness. 

Colligation,  a  mutual  enhancement  of  qualities  by  juxtaposi- 
tion in  space  or  time.  Cf,  contrast  phenomena,  rhythms,  etc. ; 
p.  419  below. 

(3)  The  law  is  :  that  the  end-organs  of  smell  are  possessed  of 
specific  energies,  akin  to  the  specific  energies  of  the  skin  or  the 
tongue,  —  but  that,  in  all  probability,  these  specific  energies  are 
not  sharply  differentiated  from  cell  to  cell,  but  distributed  in 
zones  of  varying  receptivity. 

The  first  proposition  is  proved  by  the  fact  that  complete  ex- 
haustion for  one  scent  will  leave  other  scents  entirely  unimpaired 
while  certain  others  are  as  entirely  obliterated.  The  second 
seems  to  be  proved  by  the  fact  that  many  scents  are  weakened, 
but  not  obliterated,  by  exhaustion  for  a  given  scent.  We  must 
suppose  that,  while  certain  cells  are,  perhaps,  quite  specifically 
attuned  to  a  single  small  quality,  others  are  tuned  to  respond 
both  to  this  specific  quality,  and,  more  weakly,  to  other  qualities 
as  well. 

There  is,  it  is  true,  an  alternative  view.  The  stimuli  which 
we  employ  are  in  the  great  majority  of  cases  complex,  not  simple. 
We  might  think,  then,  that  the  weakened  scents  are  those  which 
are  made  up  in  part  of  qualities  identical  with  the  qualities  of  the 
exhausting  scent  (these  would  not  be  smelled),  and  in  part  of 
different  qualities  (these  would  still  be  smelled).  Only,  in  such 
an  event,  the  scent  that  is  weakly  smelled  ought  to  have  changed, 
whereas  there  is  no  intrinsic  reason  for  its  being  weakened.  We 
ought  to  get,  not  the  original  odour,  but  certain  selected  com- 
ponents; and  these  might  be  strong.  Observations  on  the 
point  are  difficult,  and  further  work  is  needed.  —  See  Zwaarde- 
maker,  Physiol,  d.  Geruchs,  277 ;  Nagel,  Zeits.  f.  Psych., 
XV.,  86. 

Literature. — E.  Aronsohn,  Experimentelle  Untersuchungen 
zur  Physiologic  des  Geruchs,  Archiv  fiir  [Anatomic  und]  Physi- 
ologic, 1886,  321  ff. 

W.  A.  Nagel,  Ueber  Mischgeriiche  und  die  Componenten- 
gliederung  des  Geruchssinnes,  Zeits.  fiir  Psych,  u.  Physiol,  d. 
Sinnesorg.,  xv.,  1897,  82  ff. 


§  33-    Smtll  Compensations  131 

H.  Zwaardemaker,  Die  Physiologie  des  Genichs,  1895. 
On  the  preparation  of  materials  for  the  olfactometer,  see  the 
next  Experiment. 

EXPERniXVT  TEL 

$  33.  The  Olfactory  dualitiM.  (<i)  Compensations.  —  The  prin- 
ciple of  small  compensation  is  familiar  to  us  in  everyday  life. 
Most  perfumes  are  used  on  the  theory  that  they  counteract 
unpleasant  odours.  Tooth-powder  of  orris  root  (Iris  florentina) 
is  employed  to  *  purify  the  breath/  />.,  to  kill  the  foetor  ex  ore  ; 
and  *  mint  jujubes  *  appeal  to  smokers.  Those  who  have  lived 
in  a  house  with  a  cat  know  the  efficacy  of  burnt  brown  paper. 
Bridal  bouquets  often  have  gardenia  mixed  with  their  orange- 
blossoms,  the  aromatic  scent  weakening  the  too  powerful 
balsamic  odour.  In  medical  practice,  and  in  the  operating  room, 
recourse  is  had  to  the  same  principle. 

Materials. — The  cylinders  recommended  are: 

A  CMlarwood  (2)  dfi  K  India  rubber  (ordinary  red  india* 

rubber  tubing)  (5)  a 
b   i*um  benzoin  (3)  c  ** 

C  Paraifin   (the    white    wax    of  the 

histological  laboratory)  (7)  a  ** 

D  Beeswax  i^\)  b  « 

E  Tolu  balsam  (3)  c  *< 

E  Tolu  balsam  (3)  c  D  Beeswax  (i)  3 

D  Beeswax  (i)  *  C  Paraffin  (7)  a 

B  Gum  benzoin  (3)  c  F  Asafcetida  (5)  a 

G  Russian  leather  (tanned  with  san- 
dalwood, not  birch)  (i)  ^  K  India  rubber  (5)  a 
H  Rosewood  (2)  d^ 

The  numbers  are  those  of  Zwaardemaker's  classes  from  which 
the  scents  are  taken. 

Preliminaries.  —  For  the  construction  of  the  cylinders,  see 
E.  A.  McC  Gamble,  Amer.  Journal  of  Psychology,  x.,  1898, 
32  ff.  Begin  their  preparation  in  good  time :  they  cannot  be 
made  in  a  hurry,  and  failures  are  numerous  at  first,  however 
careful  the  operator.  Keep  every  cylinder  by  itself,  with  a 
record  of  its  use,  in  a  self-sealing  preserve  jar. 


132  Olfactory  Sensation 

The  idiosyncrasies  of  the  odorous  substances  must  be  learned 
by  practice.  The  following  account  of  india  rubber  may  be  help- 
ful as  an  illustration. 

(i)  Choose  a  length  of  new  rubber  tubing,  which  gives  a  pure 
india-rubber  smell.  Old  and  stiff  tubes  are  useless.  (2)  Be  sure 
that  the  tube  has  never  served  to  conduct  any  odorous  gas  or 
liquid.  India  rubber  takes  up  very  readily  the  scents  of  its  sur- 
roundings :  the  passage  of  illuminating  gas  through  a  tube,  for 
example,  even  for  a  few  seconds,  renders  the  tube  worthless. 
(3)  When  the  tube  is  not  in  use,  keep  a  glass  inhaling  tube  in  it : 
otherwise  the  rubber  will  take  up  the  scent  of  the  drawer  or  closet 
in  which  it  is  kept.  (4)  India  rubber  hardens  and  loses  its  scent 
if  exposed  to  the  air.  Hence  it  is  unnecessary  (though  it  is  well, 
on  principle)  to  put  a  paper  cap  on  the  cut  end  of  the  tubing. 
After  the  cylinder  has  been  used  a  few  times,  this  end  will  be 
quite  odourless.  (5)  India  rubber  has  the  advantage  that  it  can 
be  smelled  for  a  long  time  by  most  subjects  without  exhaustion 
of  the  organ.  (6)  The  adhesion  error  is  comparatively  small. 
(7)  If  it  is  kept  flexible,  and  free  from  contaminating  scents,  the 
tubing  will  retain  its  odour  with  undiminished  intensity  for  years 
together.  The  little  damage  done  to  the  superficial  layers  of 
the  substance  by  exposure  to  the  air  during  an  experiment  is 
made  up,  during  the  intervals  of  disuse,  by  diffusion  from  the 
deeper-lying  layers.  (8)  India  rubber  is  not  affected  by  changes 
of  temperature  between  the  limits  of  13°  and  30°  C.  (9)  Its 
odour,  though  not  very  strong,  is  very  positive,  —  an  odour  not 
easily  disguised  by  the  presence  of  other  smells.  Hence  it  is 
well  adapted  for  use  in  a  general  laboratory  room,  about  which 
smells  will  inevitably  hang,  in  spite  of  frequent  ventilation. 
However,  this  property  must  not  be  presumed  upon,  or  rule  (2) 
will  make  itself  felt. 

The  inhaling  tube  may  be  cleaned  in  various  ways.  The  nose-piece  should, 
of  course,  be  thoroughly  disinfected  for  each  experiment.  It  may  be  dipped 
in  a  carbolic  acid  solution,  or  simply  heated  in  the  flame  of  an  alcohol  lamp. 
For  washing  out  the  tube,  the  student  should  be  provided  with  a  small  funnel, 
two  tins  or  cups  for  pouring  and  receiving  water,  absorbent  cotton,  a  pliable 
brass  wire  for  pushing  the  wad  of  cotton  through  the  tube,  a  small  alcohol 
lamp  for  drying,  and  (though  this  is  not  strictly  necessary)  some  listerine. 
The  listerine  acts  both  as  deodoriser  and  disinfectant,  and  its  own  scent  is 


{  33-   ^tf^li  Compensations  133 

easily  washed  away.    See  Zwaardemaker,  Physiol,  d.  Genichs»  104;  Gamble, 
Amer.  Journ.  of  Psych.,  x..  36  f. 

The  tube  must  be  wiped  as  dry  as  possible  inside  and  out,  before  it  is  held 
ov-er  the  alcohol  flame;  else  it  will  break.  Indeed,  the  tubes  break  readily 
enough,  with  all  the  care  that  can  be  taken.  A  good  supply  must  always  be 
kept  on  hand. 

Question  ( i )  There  are  differences  of  opinion  here,  as  there 
ire  differences  of  opinion  regarding  taste  compensations  (see 
p.  1 10).  According  to  Zwaardemaker,  all  the  substances  rec- 
ommended for  this  experiment  arc  compensatory  substances^ 
(Physiol,  d.  Geruchs,  168,  268).  Aronsohn's  results,  in  spite  of 
Zwaardemaker's  interpretation  of  them,  leave  the  question  open 
(Physiol,  d.  Geruchs,  166,  267 ;  Aronsohn,  Arch.  f.  Physiol., 
1886,  353  ;  Nagel,  Zeits.  f.  Psych.,  xv.,  1897,  92).  Nagel  writes  : 
"I  have  never  observed  complete  compensation,  though,  in  say- 
ing this,  I  do  not  at  all  mean  to  dispute  its  possibility  "  (Zeits. 
f.  Psych.,  XV.,  ID  I). 

In  view  of  Zwaardemaker's  numerical  results,  of  the  recogni- 
tion of  the  principle  of  compensation  in  everyday  life  and  in 
medical  practice,  and  of  his  own  experience,  the  author  has  no 
hesitation  in  accepting  olfactory  antagonism  as  a  fact.  This 
does  not  mean  that  every  student  can  get  a  compensation  effect 
in  every  experiment.  We  know  that  some  of  the  well-meant 
attempts  at  the  removal  of  unpleasant  smells  in  ordinary  life 
result  in  a  mixture  that  is  far  worse  than  the  original  thing. 
The  obtaining  of  a  good  compensation  is  partly  a  matter  of 
luck,  —  of  moving  the  cylinder  at  the  right  rate,  catching  the 
stimulus  at  the  right  moment  of  inhalation,  etc. ;  and  partly  a 
matter  of  introspective  alertness,  —  of  pouncing  on  the  no-smell 
moment  with  a  confident  and  reliable  judgment.  If  the  observer 
is  unable,  after  a  fair  trial,  to  indicate  the  compensation  point 
on  the  scale,  the  experiment  resolves  itself  into  a  determination 
of  the  two  points,  (a)  at  which  the  first  smell  is  just  overcome 

>  We  cmn  bear  oat  this  statement  for  all  the  tubiUncet  but  RuMian  leather  {c/. 
also  the  result  of  the  contrast  experimenU,  p.  141 ).  The  discrepancy  docs  not  neces- 
sarily mean  that  Zwaardemaker  is  right,  and  that  we  are  wrong,  or  vice  versa.  When 
oae  works  in  the  rough,  and  not  with  chemically  pure  solutions,  there  is  always  a 
poinbility  of  divergent  results.  C/,  Zwaardemaker,  Arch.  f.  [Anat.  und.]  PbysioL, 
1900,429. 


134 


Olfactory  Sensation 


by  the  second,  and  {b)  at  which  the  second,  in  turn,  just  gives 
way  again  to  the  first.  Instead  of  saying,  e.g,,  that  cylinders  A 
and  AT  compensate  in  the  ratio  5.5  to  10,  we  should  have  to  say 

that 

6  cm.  A  and  10  cm.  A^give  the  ^-scent  alone,  and 
5  cm.  A  and  10  cm.  K  gwt  the  A'-scent  alone, — 

so  that  the  point  of  equality  must  lie  somewhere  between  these 
limits. 

The  following  are  the  compensation  ratios,  in  cm.,  as  given 
by  Zwaardemaker : 


5.5  A  =  lo/c 

3.5^=    " 
8.5  C  =    " 


7.0  Z?=  10  /C 
7.0  £•  =    " 


9.0  E=  10  D 
5.0  Z>  =  10  C 


The  following  are  typical  laboratory  results  from  two  observers 
(double  olfactometer) : 


1 0.0  cm.  A' compensates 

In  the  direction  ICto  A 

u  u  u  u 

"  «  ^  to  A' 

a  u  «  a 

Average 

10. o  cm.  A' compensates 

In  the  direction  KXo  B 

u  a  «  a 

Average 


6.4  cm.  A 

5.6    cm.  A 

6.2    "     " 

6.0     «     « 

5.0    «     " 

5.6     «     « 

4.4  "     " 

5.5  ±  0.8  cm. 

5.4     «     « 
5.65  ±  0.15  cm. 

3.4  cm.  B 

4.0    cm.  B 

4.0    "     " 

4.4     "    " 

37  ±  0.3  cm. 

4.2  ±  0.2  cm. 

In  these,  and  many  similar  cases,  true  compensations  were 
found.  That  is  to  say,  the  odour,  as  the  cylinder  was  moved  to 
and  fro  about  the  point  of  equivalence,  would  be  now  A,  now  if, 
or  what  not :  this  oscillation  would  continue  two  or  three  times  : 
and  then,  as  the  right  point  was  struck,  there  would  be  a  dis- 
tinct and  as.  it  were  positive  nothingness  of  smell-sensation  for 
an  instant.  The  nothingness  cannot  be  kept  for  more  than  an 
instant,  but  it  can  be  refound  without  difficulty  in  another  trial. 

It  will  be  noticed  that  the  absolute  values  in  cm.  accord  well 
with  those  of  Zwaardemaker;  this  is  not  always  the  case,  on 
account  of  the  complexity  and  variability  of  conditions. 


{  33.    Snuli  Compensations  135 

If  the  compensations  of  daily  life,  of  gardening  and  of  medical 
practice,  are  stable  and  permanent,  why  should  not  these  experi- 
mental compensations  be  the  same?  A  full  answer  to  this 
question  would  involve  reference  to  many  conditioning  factors : 
but  a  very  simple  consideration  helps  us  out  of  the  sort  of  diffi- 
culty which  it  raises  for  the  student.  The  stable  compensations 
are  not  nothingnesses,  but  partial  compensations  only.  We 
still  smell  the  orange-blossoms  of  the  bouquet,  but  we  smell 
them  weakly,  faintly.  The  point  of  exact  compensation  is  not 
reached  or,  indeed,  aimed  at.  Zwaardemaker  says,  e.g.,  that  in 
clinical  practice  "  4  gr.  iodoform  and  200  mgr.  Peruvian  balsam 
appear  almost  odourless";  and  that  the  surgeon  "by  spraying 
with  carbolic  acid  can  reduce,  indeed,  almost  completely  destroy, 
the  stench  of  pulmonary  gangrene"  (Physiol,  d.  Geruchs,  165). 
The  rough  result  is  what  is  here  wanted,  not  any  extreme 
accuracy  of  balance. 

{2)  Zwaardemaker  states  that  he  sometimes  obtained,  in  the 
near  neighbourhood  of  the  compensation  point,  a  weak,  inde- 
terminate, but  qualitatively  simple  impression,  —  a  scent  quite 
different  from  the  two  primary  scents,  and  discoverable  only  by 
extreme  attention  (Physiol,  d.  Geruchs,  167 ;  cf.  Nagel,  Zeits.  f. 
Psych.,  XV.,  90,  loi).  The  author  has  found  no  trace  of  this 
mixed  scent,  in  experiments  with  compensating  substances ;  and 
it  is  difficult  to  see  how  its  existence  is  reconcilable  with  the  fact 
of  compensation.  Any  case  in  which  it  is  reported  should  be 
thoroughly  investigated.  —  It  is  possible,  of  course,  that  this 
"schwache,  undefinirbare  Empfindung"  (Arch.  f.  [Anat.  u.] 
Physiol.,  1900,  429)  is  identical  with  our  "positive  nothingness." 

(3)  In  the  first  place,  the  inner  cylinder  may  be  contaminated  ; 
the  air-current  can  get  to  it  only  by  way  of  the  outer  cylinder, 
and  the  adhesion  error  comes  in,  in  a  new  way.  Secondly, 
the  criticism  is  always  possible  that  the  odorous  particles 
of  the  two  substances  combine,  in  some  unknown  physical  or 
chemical  way,  to  annul  each  others*  smell-producing  properties. 
We  do  not  know  enough  to  say,  in  physical  or  chemical  terms, 
whether  such  criticism  is  just  or  not.  The  results  of  the  second 
experiment  throw  it  out  of  court  as  an  argument  against  the  fact 
of  compensation. 


136  Olfactory  Sensation 

(4)  It  would  seem  that  olfactory  compensation  is  a  phenomenon 
of  frequent  occurrence  and  of  high  importance.  We  know  too 
little,  as  yet,  to  draw  any  definite  conclusions  from  the  facts  : 
besides  which,  the  facts  themselves,  as  we  have  seen,  are  by  no 
means  universally  admitted.  They  carry  with  them,  however, 
the  suggestion  that  the  ultimate  specific  energies  of  smell  must 
be  pretty  numerous  :  many  more  than  the  six  of  sight  or  the 
four  of  taste.  Zwaardemaker  meets  the  suggestion  by  assuming 
a  serial  differentiation  (a  skalenbildcnde  Schattierjmg)  of  scents 
within  each  of  the  specific-energy  groups  (Physiol,  d.  Geruchs, 
268).  More  recently,  viewing  the  facts  in  the  light  of  a  general 
theory  of  mental  inhibition,  he  says  that  "  compensations  are  to 
be  expected  in  all  cases  where  there  are  even  partial  differences 
of  quality,"  and  draws  a  parallel  between  intensive  odours  and 
unsaturated  colours  (Arch.  f.  [Anat.  u.]  Physiol,  1900,  432). 

(b)  Mixtures.  —  The  principle  of  smell  mixture  is,  also,  familiar 
to  us  outside  of  the  laboratory.  The  flower-scents  of  the  per- 
fume industry,  e.g.^  are  in  many  cases  quite  complicated  mixtures. 
Thus  the  scent  of  'heliotrope'  is  obtained  from  a  mixture  of 
vanilla,  rose,  orange-flower,  amber  and  almond. 

Materials.  —  The  series  of  scents  employed  should  contain 
members  drawn  from  each  of  Zwaardemaker's  classes  :  cf.  the 
list  recommended  on  p.  127.  The  results  quoted  below  (p.  137) 
were,  unfortunately,  not  gained  by  systematic  work  of  this  kind. 

Questions.  —  (i)  Again,  we  find  difference  of  opinion  in  the 
literature.  Nagel  writes  :  "  I  have  never  found  a  pair  of  odorous 
substances  that  did  not  give  a  mixed  scent  {i.e.,  a.  true  smell 
mixture]  when  compounded  at  the  right  relative  intensities  " 
(Zeits.  f.  Psych.,  xv.,  95).  Zwaardemaker  admits  the  fact  of 
mixture,  but  only  as  between  scents  of  the  same  or  of  closely 
related  classes  (Physiol,  d.  Geruchs,  280).  Aronsohn  finds 
mixture  in  some  cases,  rivalry  [alternation  of  the  two  original 
qualities]  in  others  ;  though  he  says  that,  if  more  than  two  com- 
ponents are  taken,  a  mixed  scent  is  always  produced  (Arch.  f. 
Physiol.,  1886,  353).  Valentin  declares  that  two  simultaneous 
smell-stimuli,  of  approximately  equal  intensity,  set  up,  for  him, 
two  simultaneous  but  distinct  sensations:  precisely  the  effect 


$  33-    Smeii  Mixtures  \  ;; 

which  Nagel  denies  (Lehrbuch  d.  Physiol,  d.  Menschen,  1844, 
ii.,  2,  292,  §  41 19).  What  is  wanted,  then,  is  systematic  work 
with  different  intensities  of  the  various  qualitative  stimuli. 

Those  who  obtained  the  compensation  result  in  the  foregoing 
experiment  will  require  no  arguments  to  prove 'that  certain 
scents  do  not  mix.  The  rule  with  the  compensative  scents  is : 
oscillation,  nothing.  Those,  on  the  other  hand,  who  failed  to 
secure  true  compensations  may  incline  to  agree  with  Nagel. 
Nevertheless,  direct  experiments  rarely  if  ever  fail  to  convince 
the  observer  that  there  are  some  scents  which  do  not  mix,  as 
well  as  very  many  which  do.  —  Criticism  of  these  experiments 
will  be  given  below,  under  (4).     The  following  are  typical  results  • 


Mixtures.  — 

Musk  (artif.)  and  Opium Qasscs  (4)  by 

(S)a. 

**                  Vanilline    .     . 

ii 

n 

(3)^. 

•*                  Listen  ne    .     . 

« 

i( 

(2) 

Musk  (nat)  and  Pyridine  .     .     . 

(i 

ii 

(6)  a. 

Caryophylline  and  OI.  cani   .     . 

« 

(2)^ 

(2)  CO. 

Iodine  and  Ylang  ylang     .     .     . 

U 

(5)^, 

(3)  <^ 

**             Camphor     .... 

u 

u 

(2)  a. 

Camphor  and  Ol.  aurant.  dale.    . 

a 

(2)  a, 

(2)  ^tp. 

♦*               01.  anisi        .     .     . 

a 

ii 

(2)  CO. 

«               Ylang  ylang     .     . 

n 

n 

(3)  ^a- 

"               Laudanum   .     .     . 

n 

a 

(S)a. 

*<               01.  terebinth.   .     . 

'• 

a 

(2)  a. 

**               01.  juniperi       .     . 

<. 

a 

(2)  ca. 

Laudanum  and  Ol.  juniperi     .     .     . 

ii 

(8)«, 

(2)  CO. 

Allyl  sulphide  .     . 

n 

M 

(5)^- 

Iodine  and  Ol.  succini 

ii 

(5)^, 

(4)^. 

Valerianic  add  and  Ol.  lavandulae 

ii 

(2)  cy, 

(2)  cy. 

•*                        01.  salviae   .    . 

u 

a 

(4)^. 

**                        Hyacinth     .     . 

u 

a 

(3)  da. 

Petroleum  and  Ol.  salviae      .    .    . 

u 

(6)*, 

(4)^. 

Noimxture. — 

Pyridine  and  Jasmine •          ** 

(6)  a, 

(3)aa. 

Hyacinth " 

Valerianic  acid  and  Heliotropine     ...          " 

(2)  ^y, 

(3)^- 

Opium  and  Ol.  salviae ** 

{S)a, 

(4)^- 

Neroli  and  Petroleum ^ 

(3)  «A 
(2)  a, 

A^^S^cl    MilB^I     A    VVfl\/SWUSIl          •••••■• 

Camphor  and  Allyl  sulphide 

"              Petroleum    .     . 

ii 

u 

(6)^. 

138  Olfactory  Sensation 

These  results  ( i )  speak  for  Nagel  and  against  Zwaardemaker,  on 
the  point  that  members  of  remote  classes  may  mix  as  readily  as 
members  of  nearly  related  classes  (Physiol,  d.  Geruchs,  283  f.  ; 
Zeits.  f.  Psych.,  xv.,  94);  while  (2)  they  speak  for  Zwaarde- 
maker and  a'gainst  Nagel,  on  the  point  that  there  are  certain 
scents  which  do  not  mix  at  all,  but  persist  side  by  side  in  olfac- 
tory rivalry. 

(2)  The  resultant  scents  differ  very  greatly  as  regards  per- 
manence. Some  are  quite  stable ;  others  as  fleeting  as  the 
nothingnesses  of  the  compensation  experiments.  The  'mix- 
tures' of  the  list  just  given  are  stable.  On  the  other  hand, 
instable  mixtures  were  found  as  follows  : 

Allyl  sulphide  and  Musk  (nat.) Classes  (5)  <z,  (4)  b. 

Heliotropine  and  Musk  (artif.) "       (3)  c,  (4)  b. 

Citral  and  01.  carvi «       (2)  ^/S,  (2)  ca. 

Camphor  and  01.  citri "       (2)  tz,  (2)  dfi. 

Iodine  and  01.  salviae "       (5)  c^  (4)  a. 

Valerianic  acid  and  Camphor "       (2)  ^y,  (2)  a. 

For  other  instances,  and  explanation,  see  Nagel,  Zeits.  f.  Psych., 
XV.,  95. 

(3)  Yes :  and  similar  evidence  was  afforded  by  the  compen- 
sation phenomena. 

(4)  The  experiments  above  quoted,  and  the  whole  Experiment 
as  described  in  the  text,  are  always  open  to  the  objection  that 
they  do  not  control  the  mtensities  of  the  stimuli  employed. 
Nagel  is  quite  right  in  demanding  "  the  right  ratio  of  intensities 
of  the  two  qualities  "  (p.  92) :  and  his  own  conclusion,  that  all 
odorous  substances  mix  for  sensation,  is  limited  by  the  phrase 
"bei  geeigneter  Intensitatsbemessung"  (p.  95).  We  ought, 
then,  if  we  are  to  settle  the  point,  (i)  to  employ  scents  from  all 
of  Zwaardemaker's  classes,  and  (2)  to  employ  them  in  the  form 
of  olfactometric  cylinders,  so  that  we  can  mix  all  intensities  (at 
least,  all  intensities  from  liminal  to  very  strong)  of  all  stimuli. 
The  student  may  be  left  to  devise  a  regular  method  of  procedure, 
on  the  lines  of  rules  already  laid  down. 


§  33-    Smell  Contrasts  139 

On  the  other  hand,  no  amount  of  control  of  intensities  can  do 
away  with  the  compensation  results  on  the  olfacto^neter ;  and 
the  fact  that  some  mixtures  are  stable,  and  others  curiously 
transient  and  elusive,  suggests  at  least  the  possibility  that  these 
latter  may  be  terms  in  a  series  which  ends  with  complete  refusal 
to  mix. 

The  experiment  may  be  continued,  if  the  Instructor  deem  it 
advisable,  with  more  than  two  stimuli.  Points  to  notice  are : 
(i)  that  increase  of  the  number  of  components  means,  as  a  gen- 
eral rule,  a  more  penetrating  and  permanent  smell  mixture ;  but 
(2)  that  the  intensity  of  the  resulting  mixture  is,  also  as  a  rule, 
noticeably  less  than  the  intensity  of  the  strongest  component.  — 
Nagel,  pp.  99t  loi  ;  Zwaardemaker,  Physiol,  d.  Geruchs,  167. 

{c)  Contrasts.  —  Very  little  is  said  of  smell  contrast  in  the 
literature.  Zwaardemaker  cites  Linnaeus  to  the  effect  that  the 
scent  of  musk  contrasts  with  faecal  smells ;  and  remarks  himself 
that  "cheese  and  Bordeaux,  high  game  and  Burgundy,  are  evi- 
dently opposed  odours  "  (Physiol,  d.  Geruchs,  251).  It  is  still 
uncertain  whether  taste  contrasts  are  comparable  to  visual 
contrasts,  and  the  antagonisms  in  taste  and  smell  to  the  three 
antagonisms  of  sight.  It  is  uncertain,  too,  whether  smell  mix- 
tures are  more  nearly  akin  to  mixed  colours  or  to  the  fusion  of 
tones  in  a  clang.  But  it  is  as  difficult  to  suppose  that  there  is 
no  contrast,  where  there  is  antagonism,  as  it  is  to  think  that 
antagonistic  processes  can  give  rise  to  a  mixed  sensation  (see 
p.  135).  And  the  argument  from  analogy  seems  to  be  fully 
borne  out  by  experiment. 

Materials.  —  The  cylinders  are : 

A  Cedarwood  (2)  dfi 

B  Gum  benzoin  (3)  c 

D  Beeswax  ( i )  ^ 

E  Tolu  balsam  (3)  c 

G  Russian  leather  (i)  ^ 

K  India  rubber  (5)  a 

L  Glycerine  soap  (i)  r  and  (7)  a 

M  Cocoa  butter  (2)  b  ?  and  (7)  a 


140  Olfactory  Sensation 

Weak  glycerine  soap  gives  a  pure  ethereal  smell ;  strong,  the 
ethereal  mixed  with  a  fatty  smell.  Very  weak  cocoa  butter  is 
merely  fatty;  stronger,  fatty  and  aromatic.  For  the  construc- 
tion and  properties  of  the  new  cylinders,  see  Amer.  Journ.  of 
Psych.,  X.,  32  ff. 

Preliminaries.  — The  meaning  of  the  'stimulus  limen  '  must 
be  explained  to  the  student.  See  Ktilpe,  Outlines  of  Psychology, 
34 ;  Titchener,  Outline,  78  ff. 

The  method  given  for  the  determination  of  the  limen  is  very 
incomplete.  Its  incompleteness  does  not,  however,  affect  the 
relative  value  of  the  experimental  results.  Kiilpe  gives  -the 
method  in  full  (Method  of  Just  Noticeable  Stimuli:  pp.  55  f.); 
and  it  may  be  explained  to  the  student,  and  the  method  of  the 
text  modified,  if  the  Instructor  wishes  (see  Question  2).  We 
shall  describe  the  complete  method  in  vol.  ii. 

There  may  arise,  with  some  (9's,  during  the  preliminary  work 
upon  the  K-limen,  a  tendency  to  determine  the  liminal  value  in 
terms  not  of  smell  but  of  hand-movement.  The  limen  gets  to 
be  thought  of,  unwittingly,  not  as  a  just  noticeable  smell,  but  as 
a  push-out  of  the  cylinder  just  so  far.  The  error  is  not  by  any 
means  general.  As  a  rule,  too,  both  E  and  O,  if  they  are  work- 
ing conscientiously,  will  discover  and  report  the  tendency.  But 
if  the  Instructor  suspect  the  error,  he  should  question  E  and  O 
(separately)  for  evidence  of  it,  and  in  further  work  let  E  move 
the  cylinder,  telling  O  that  it  will  not  be  moved  at  a  uniform 
rate. 

If  the  question  of  this  source  of  error  comes  up,  let  O  and  E 
face  it,  and  work  out  the  possible  influence  of  the  error  in  con- 
trast experiments. 

Experiment. — Great  care  must  be  taken  that  the  adhesion 
error  is  not  neglected. 

The  following  results  are  typical : 

0  {i)\  Limen  for  K^  10  experiments,  7.0  ±  0.6  mm. 
C>(2):       «  "      «  "  6.8  ±0.4  mm. 

1  The  K  of  these  results  is  black  (not  red)  rubber  tubing. 


$  33-    Smeii  Mixtures 


141 


Cyliadtn. 

LiMafbrO(i). 

LIbmb  Cm  0  (t). 

Scries  I 

A- 

6.0  mm. 

5.0  mm. 

A- after  ^ 

2.0 

3.0 

K 

6.0 

6.0 

A'after£' 

30 

3.0 

A- 

6.0 

6.0 

A' after  Z? 

4.0 

4.0 

K 

6.0 

5.0 

AT  after /I 

2.0 

2.0 

SeriesU. 

K 

75 

8.0 

A- after  Z> 

6.0 

6.0 

K 

1 0.0 

7.5 

K^XttB 

8.0 

5.0 

K 

0.0 

1 0.0 

/rafter  iE" 

6.0 

7.0 

K 

8.0 

1 0.0 

Kz.htrB 

6.0 

6.0 

Series  III. 

K 

50 

6.0 

KziXtx  L 

50 

6.0 

K 

6.0 

5.0 

K^iX^x  M 

8.0 

5.0 

K 

7.0 

7.0 

KziXtxG 

8.0 

8.0 

K 

6.0 

6.0 

KzhtxM 

7.0 

6.0 

K 

6.0 

6.0 

KtAxzx  L 

8.0 

7.0 

K 

6.0 

6.0 

AT  after  c; 

7.0 

7.0 

It  is  evident  that  there  is  always  a  slight  reduction  of  the  limen 
after  previous  stimulation  by  a  compensating  stimulus,  whereas 
stimulation  by  glycerine  soap,  Russian  leather  and  cocoa  butter 
either  leaves  the  limen  as  it  was  or  slightly  raises  it.  —  The 
three  different  series  were  taken  at  three  days*  intervals,  I. 
in  the  early  morning,  II.  and  III.  in  the  afternoon.  Neither 
O  knew  the  other's  results.  Both  were  well  trained  in  olfactory 
work. 

Questions.  —  ^^(i)  There  is  good  evidence  of  contrast,  in 
results  like  the  above.    This  evidence  tallies  with  the  results  of 


142 


Olfactory  Sensation 


the  compensation  experiments  :  cf,  the  Russian  leather  result, 

p.  133. 

E  and  O  (2)  The  students  should  be  encouraged  to  think  out 
a  method,  giving  the  reasons  for  every  step.  The  principle  of 
the  Method  of  Just  Noticeable  Stimuli  may  very  well  occur  to 
them. 

E  and  O  (3)  The  contrast-stimulus  might  be  given  to  the  one 
nostril,  and  the  following  K-stimulus  to  the  other.  The  follow- 
ing results  were  gained,  under  these  conditions,  by  the  two  (9's 
already  quoted : 


Cylinders. 

Limen  for  C>  (i). 

Limen  for  O  (2). 

K 

7.0  mm. 

6.0  mm. 

Kzh^xA 

4.0 

4.0 

K 

7.0 

6.0 

K^Si^rD 

5.0 

4.0 

K 

6.0 

5.0 

K^iitrB 

30 

3-0 

^ 


Instruments.  —  Fig.    15    shows   the    principle   of    Zwaarde- 

maker's  Fluid-Mantle  Ol- 
factometer :  tty  odorous 
liquid  ;  b,  kaolin  cylinder  ; 
Cy  screen ;  d,  inhaling 
tube.  A  double  fluid- 
mantle  olfactometer,  made 
entirely  of  metal,  is  fig- 
ured in  L'Ann^e  psycho- 
logique,  v.,  1899,  215;  it 
is  supplied  by  the  mech- 
anician of  the  Physiolog- 
ical Laboratory,  Utrecht, 
for  fl.  48.  A  single  fluid- 
mantle  olfactometer  costs 
fi.  32. 


Fig.  15.  —  See  L'Annde  psycho- 
logique,  v.,  1899,  223.  On 
p.  217  is  a  cut  of  the  old  model 
(wooden  stand)  double  olfac- 
tometer. 


CHAPTER  VI 

Organic  Sensation 

§34.  Orgmnio  Sensation. — On  organic  sensations,  see  A. 
Goldscheider,  Ges.  Abh.,  ii.,  1898;  Kiilpe,  Outlines,  140,  146; 
G.  E.  Miiller  and  F.  Schumann,  Pfluger's  Arch.,  xlv.,  1889, 
37;  E.  B.  Delabarre,  Ueber  Bewegungsempfindungen,  1891  ; 
E.  Kroner,  Das  korperliche  Gefiihl,  1887;  E.  Mach,  Grund- 
linien  d.  Lehre  von  d.  Bewegungsempfindungen,  1875  ;  Foster, 
Text-book  of  Physiol.,  iv.,  1891,  1433;  C.  Richet,  Recherches 
exp^rimentales  et  cliniques  sur  la  sensibility,  1877  ;  E.  H.  Weber, 
op.  cit\  Wundt,  Phys.  Psych.,  i.,  1893,  419  ;  Sanford,  Course,  25, 
cxps.  33-5 1  ;  O.  Funke,  op,  cit. ;  H.  Beaunis,  Les  sensations 
internes,  1889. 

The  literature  of  the  static  sense  is  large.  An  appreciation  of  theories, 
and  the  devising  of  an  inexpensive  instrument  for  ordinary  laboratory  work, 
might  be  assigned,  as  a  minor  problem,  to  an  interested  student. 

Preliminary  Exercises. — (i)  See  Kiilpe,  142;  Titchener, 
Outline,  68  f. 

(2)  Goldscheider,  323.  The  student  may  also  perform  the 
experiments  on  the  '  paradoxical '  sensations  of  resistance  and 
weight,  90  fif. 

Questions.  —  ( i )   Kulpe,  1 40. 

(2)  Titchener,  Outline,  50  f. 

(3)  The  points  to  be  emphasised  are  (a)  the  importance  of 
the  sensations  for  the  psychological  *  self,'  {b)  their  importance 
as  the  vehicle  of  the  sense-feelings  and  (c)  the  part  played  by 
them  in  recognition,  recollection,  etc. 

EXPERIMENT  XX 

§35.  The  Seniatioii  of  Muscular  ContraotioiL  —  The  term 
'  muscular  sense '  has  been  badly  abused  in  psychological  litera- 
ture.     It  has  come  to  mean   "I'ensemble  des  sensations  qui 

«43 


144 


Organic  Sensation 


nous  renseignent  sur  I'^tat  de  nos  organes  moteurs  "  (Henri), 
the  sense  of  vision  being  by  tacit  consent  excluded  from  the 
definition.  Henri,  who  gives  a  good  Revue  g^n^rale  sur  le  sens 
musculaire  (in  this  wider  signification)  in  the  Ann6e  psycholo- 
gique,  v.,  1899,  399  ff.,  admits  that  "le  terme  est  tr^s  mauvais," 
but  thinks  it  the  best  of  existing  titles  for  his  subject.  There 
seems,  as  a  matter  of  fact,  to  be  no  reason  whatever  for  con- 
tinuing a  usage  which  originated  in  a  false  theory  (the  theory 
that  muscular  sensations  proper  give  us  our  perceptions  of 
movement)  and  which  now  requires  a  prefatory  apology  from 
the  writer.  If  we  wish  to  group  together  the  sensations  in 
question,  to  emphasise  their  community  of  function,  we  may 
employ  Bastian's  phrase,  *kinaesthetic  sensations.'  If  we  are 
working  analytically,  it  is  best  —  indeed,  it  is  the  only  justifiable 
course  —  to  speak  of  *  muscular  sensation,*  'tendinous  sensa- 
tion,' *  articular  sensation,'  as  we  speak  of  sight,  hearing,  cuta- 
neous sensation,  etc.  The  sensation  which  we  isolate  in  the 
present  experiment  is  the  sensation  whose  peripheral  end-organ 
is  striped  muscle,  and  whose  stimulus  is  muscular  contraction  : 
just  as  a  visual  sensation  is  a  sensation  whose  peripheral  end- 
organ  is  the  retina,  and  which  is  set  up  by  the  action  of  light 
(or  some  inadequate  stimulus)  upon  the  retina. 

Materials. — The  student  should  famil- 
iarise himself  with  the  theory  and  use  of 
the  physiological  inductorium.  Good  ex- 
planatory diagrams  are  given  by  Waller, 
Human  Physiology,  315.  Fig.  16  shows 
the  connections  required  by  the  present 
experiment.  The  Helmholtz  side-wire  is 
removed,  and  the  Wagner  hammer  (inter- 
rupter) is  out  of  function. 

The  form  of  weight  employed,  key,  cells, 
arm-rest  and  electrodes  may  of  course  vary 
considerably,  without  variation  of  any  of  the 
essential  requirements  of  the  experiment. 
Preliminaries. — The  introspective  rec- 
ord (which  may  be  dictated  to  E,  or  written  by  O  with  his  right 
hand)  will  run  somewhat  as  follows. 


Fig.  16.  —  Arrangement 
of  inductorium  for 
single  (unmodified) 
shocks.  A.  Waller, 
An  Introduction  to 
Human  Physiology* 
1891,  315-  C/.  Fig. 
II. 


§  35      ^'  Sttuatiom  of  Muscular  Contraction  145 

Light  Pressure.  —  *  iYicking,  ticKiing  scnsaiions.  due  to  the 
roughness  of  the  chamois  skin.  Pressure  from  the  skin.  Shape 
and  relative  size  of  the  stimulus  clearly  perceived.  Tendency  to 
rub  or  scratch  the  arm  after  removal  of  stimulus.  No  sub- 
cutaneous sensations.' 

Heavy  Pressure.  —  'Tickling  much  less.  A  deeper  skin 
sensation,  as  if  from  the  under  part  of  the  skin.  The  rough- 
ness and  coolness  of  the  first  application  change  to  smoothness 
and  warmth.  Towards  the  end  of  the  time  of  stimulation,  very 
little  sensation  at  all ;  what  there  is,  is  definitely  localised  in  the 
skin/ 


Fig.  17.  —  Arm-rest,  designed  for  use  with  kinesimeter;   Fig.  9,  above. 

Experiment  (i). — A.  Goldscheider,  to  whom  we  owe  this 
experiment,  advises  (1888)  a  subcutaneous  cocaine  injection  for 
the  anaesthetising  of  skin,  subcutaneous  tissue  and  the  super- 
ficial layers  of  the  muscle  under  investigation.  Physicians  are 
now  strongly  of  the  opinion  that  cocaine  injections  should  be 
avoided,  unless  the  patient's  constitution  is  thoroughly  known, 
and  that  in  any  case  the  cocaine  should  be  injected  only  in  very 
small  quantities.  Ether  spraying  is  safe,  and  answers  every 
purpose.  If  long  continued,  it  anaesthetises  not  only  the  skin, 
but  the  subcutaneous  tissue  as  well. 

The  introspective  record  will  be,  in  brief,  somewhat  as  fol- 
lows. *  The  ether  must  be  applied  several  times  before  there  is 
any  loss  of  the  sensations  above  described.     Presently,  the  light, 


146  Organic  Sensation 

tickling,  pricking  sensations  become  indistinct,  and  a  dull,  diffuse 
sensation  takes  their  place.  This  is  not  localised  in  the  skin, 
but  just  beneath  it.  It  is  shallow  as  regards  the  muscle,  but 
decidedly  beneath  the  skin. 

*  After  further  etherisation,  the  cutaneous  sensations  disap- 
pear entirely.  Nothing  can  be  said  of  the  temperature,  pressure, 
size,  shape,  smoothness  or  roughness  of  the  stimulus.  The  dull 
sensation  has  gone  deeper  into  the  muscle,  and  is  more  vague 
and  indefinite  than  before.  There  seems  to  be  a  hard,  dead 
lump  in  the  muscle ;  and  at  times  it  is  as  if  the  muscle  fibres 
were  ground  or  rolled  against  each  other.  The  diffuse  and  in- 
definite, and  yet  definitely  "  inside  "  sensation  persists  from  now 
on ;  it  seems  to  be  quite  simple,  but  is  exceedingly  difficult  to 
describe. 

*  No  change  occurs,  as  the  spraying  is  continued,  except  that 
the  muscle  sensation  becomes  duller  and  more  indefinite,  and 
perhaps  deeper  seated.  It  is  like  the  feeling  of  a  tired,  over- 
worked limb.  In  general,  it  has  not  the  vigour  or  freshness  of 
cutaneous  sensations,  though  now  and  again  it  is  almost  a  pain. 

*  After  the  spraying  has  ceased,  the  sensations  come  back  by 
degrees,  in  the  order  from  within  outwards.  The  change  seems 
to  be  one  from  simplicity  to  complexity,  and  also  from  vague- 
ness to  distinctness  and  acuteness.' 

It  is  hardly  possible  to  get  nearer  to  the  specific  quality  of  the 
muscle  sensation  than  these  analogical  and  descriptive  phrases 
take  us.  Goldscheider's  words  are:  "eine  in  der  Tiefe  local- 
isirte  dumpfe  Empfindung  von  eigenthiimlichen  Charakter "  ; 
**das  Gefiihl  ist  in  der  Tiefe  localisirt  und  ist  diffuser 
Art " ;  "  diese  dumpfe,  ziehende  Sensation  in  dem  Gebiete  des 
Muskels  "  ;  "  man  kann  die  Muskelempfindung  bis  zum  Schmerz 
steigern "  :  expressions  that  tally  well  with  the  introspective 
records  just  quoted. 

Experiment  (2).  —  On  the  determination  of  the  *  motor 
point,'  see,  e.g.^  W.  Erb,  Handbook  of  Electrotherapeutics, 
trans,  by  L.  Putzel  [1883],   121  ff. 

Goldscheider  notes  that  currents  which  produce  a  slight, 
though  distinctly  visible  muscular  contraction,  give  no  muscular 
sensation  at  all ;  the  contraction  must  be  sharp  and  strong,  if 


§  35-    ^^  Sensation  of  Muscular  Contraction  147 

the  sensation  is  to  result.  The  student  will  be  able  to  verify 
this  observation  as  he  gradually  moves  the  secondary  in  towards 
the  primary  coil. 

The  result  of  electrical  stimulation  accords  with  that  of  the 
foregoing  experiment.  *  The  sensations  are  as  before,  only  not 
so  definite.  There  seems  to  be  a  difference  in  intensity,  but 
the  sensations  themselves  are  exactly  alike.  The  muscle  sensa- 
tion is  again  vague,  hard,  indefinite,  dull,  dead,  at  times  almost 
painful ;  it  seems  to  be  seated  deep  down  in  the  muscle.'  The 
difference  of  intensity  can  be  eliminated,  if  O  desires,  by  moving 
the  secondary  still  nearer  to  the  primary  coil. 

The  involuntary  contraction  of  the  finger  plays  but  a  very 
small  part  in  consciousness  during  the  experiment.  *  I  seemed 
to  be  helpless  to  prevent  the  twitch  ;  it  came  from  outside,  and 
was  something  that  I  was  not  concerned  with.  I  had  a  slight, 
sharp  sensation  in  the  finger  tip,  but  I  did  not  pay  enough 
attention  to  it  to  recall  anything  of  its  nature.' 

Experiment  (3). — The  same  dull,  diffuse,  hard  sensation 
can  readily  be  identified  as  the  mechanical  pressure  is  increased. 

Additional  Experiment.  —  Let  O  fatigue  his  arm  by  means 
of  the  finger  dynamometer  prescribed  for  Experiment  XXIII., 
and  attempt  to  analyse  out  from  the  fatigue  complex  the  peculiar 
quality  of  muscular  sensation  which  he  has  identified  in  the 
above  experiments. 

Questions.  — (i)  There  can  be  no  doubt  as  to  the  specificity 
of  the  muscular  sensation :  Goldscheider  says  unhesitatingly 
that  it  "sich  sehr  merklich  von  jeder  anderen  Empfindung 
unterscheidet."  It  has,  nevertheless,  a  decided  resemblance  to 
the  sensation  of  cutaneous  pressure ;  such  a  sensation,  e.g.^  as 
is  set  up  by  the  pressure  of  the  blunt  compass-points  in  aesthesio- 
metric  work  (see  Experiment  XXXIV.).  The  author  was  for  a 
long  time  inclined  to  regard  these  two  sensations  as  qualitatively 
indistinguishable,  and  to  refer  their  differences  of  diffusion,  dis- 
tinctness, etc.,  to  associated  processes.  Recent  work  has,  how- 
ever, assured  him  that  the 'dulness,* 'deadness,'  *  diff useness ' 
of  the  muscular  sensation  constitute  it  a  new  quality.  There 
is,  probably,  no  better  name  for  it  than  the  sensation  of  '  mus- 
cular pressure.' 


148  Organic  Sensation 

(2)  "  In  all  transformers,  the  electromotive  forces  generated 
in  the  secondary  circuit  are  to  those  employed  in  the  primary 
circuit  nearly  in  the  same  proportion  as  the  relative  numbers  of 
turns  in  the  two  coils.  For  example,  if  the  primary  coil  has  100 
turns,  and  the  secondary  has  2,500  turns,  the  electromotive 
force  in  the  secondary  circuit  will  be  nearly  25  times  as  great 
as  that  used  in  the  primary"  (S.  P.  Thompson,  Elementary 
Lessons  in  Electricity  and  Magnetism,  1895,  218).  This  is  the 
principle  of  the  inductorium.  The  primary  coil  has  compara- 
tively few  turns  of  thick  wire  :  the  pressure  (volts)  is  low,  the 
current  (amperes)  relatively  heavy.  The  secondary  coil  has  a 
great  many  turns  of  very  fine  wire :  the  pressure  is  enormously 
increased,  so  that  we  can  send  the  current  through  the  resistance 
offered  by  living  tissue ;  the  current  itself,  on  the  other  hand, 
is  so  light  as  to  be  entirely  innocuous.  —  The  student  should 
understand  the  difference  between  the  make  and  break  currents, 
and  the  reasons  for  the  greater  suddenness  and  sharpness  of  the 
latter. 

Literature.  —  See,  besides  the  passages  cited  from  Henri, 
Waller  and  Thompson,  A.  Goldscheider,  Gesammelte  Abhand- 
lungen,  ii.,  1898,  37  ff. ;  H.  C.  Bastian,  The  Brain  as  an  Organ 
of  Mind,  3d  ed.,  1885,  543;  W-  Erb,  Handbook  of  Electro- 
therapeutics  [1883],   15,   125. 


CHAPTER  VII 

The  Affective  Qualities 

$  36.  Affection. — The  unsettled  state  of  the  psychology  of 
the  affective  processes  is  something  of  a  scandal  to  experimental 
psychology,  although  excuses  for  it  are  not  far  to  seek,  (i)  The 
processes  themselves  are  notoriously  elusive,  disappearing  as  we 
try  to  attend  to  them,  and  translating  themselves  into  ideas  at 
the  slightest  possible  provocation.  (2)  We  get  no  direct  aid 
from  physiology.  There  is  no  peripheral  organ,  as  there  is  in 
the  case  of  sensation  ;  and  the  central  conditions  of  feeling  are 
simply  matters  of  speculation.  (3)  It  is  true  that  we  get  indirect 
aid  from  physiology,  in  the  form  of  the  '  method  of  expression.' 
The  curves  of  breathing  and  volume  and  pulse  doubtless  tally 
with  the  variations  and  trends  of  affective  consciousness.  But 
until  we  know  the  affective  consciousness  itself,  how  are  we  to 
be  sure  of  interpreting  our  curves  ?  One  has  not  to  go  far  into 
the  literature  to  find  what  one  is  tempted  to  call  ridiculously 
different  readings  of  the  same  curve.  (4)  As  for  psychological 
methods,  to  supplement  the  physiological,  we  have  only  (a)  the 
method  of  impression,  which  holds  out  no  promise  of  ever  set- 
tling the  question  of  the  number  of  affective  qualities,  and  (d)  the 
method  of  suggestive  disintegration,  which  attempts  to  analyse 
out  each  of  these  qualities  by  suggesting  the  others  away,  —  itself 
at  present  rather  a  crude  suggestion  of  method  than  a  practi- 
<:able  rule  of  working.  (5)  Corresponding  to  this  dearth  of 
settled  facts,  we  have  a  hypertrophy  of  theory  and  a  large  con- 
troversial literature.  Partly  because  the  theories  are  intrinsically 
interesting,  and  partly  because  of  the  sheer  bulk  of  the  litera- 
ture, the  fundamental  issues  of  affective  psychology  are  apt  to 
be  left  out  of  sight.  It  is  easier  and  more  exciting  to  criticise 
so-and-so's  theory  of  pleasure-pain,  than  to  face  the  problem  of 
the  affective  qualities  for  oneself ;  and,  indeed,  theory  has  had 

149 


I50  The  Affective  Qualities 

so  wide  a  range  that  one  can  hardly  turn  in  any  direction  without 
being  confronted  by  some  so-and-so's  speculations.  . 

The  author  has  taken  up  a  conservative  position  in  the  text, 
not  because  he  is  enamoured  of  it  as  a  position,  — James'  theory 
of  emotion  and  Wundt's  theory  of  the  affective  qualities  are  far 
more  picturesque,  —  but  because  he  believes  that  it  offers  the 
safest  ground  from  which  to  work  towards  a  better  affective 
psychology.  And  for  that  we  must  look  (i)  to  physiological 
advance,  to  increased  knowledge  of  what  Fechner  called  *  inter- 
nal psychophysics,*  and  to  increased  knowledge  of  the  physio- 
logical basis  of  our  curve  variations,  and  (2)  to  the  gradual 
emergence  of  an  introspective  consensus.  This  last  is  not 
entirely  hopeless,  seeing  that  introspection  is  constantly  sharpen- 
ing and  refining,  under  the  influence  of  the  experimental  method 
at  large. 

For  the  various  theories  mentioned  in  the  text,  the  following 
books  may  be  consulted  : 

(i)  {a)  Th.  Ziehen,  Introd.  to  Phys.  Psych,  (trans,  by  C.  C. 
van  Liew  and  O.  W.  Beyer),  1895,  130;  Leitfaden,  5th  ed., 
1900,  108. 

(b)  C.  Lange,  Ueber  Gemiithsbewegungen,  eine  psychophysio- 
logische  Studie,  1887,  J^. 

{c)  H.  Miinsterberg,  Beitr.,  iv.,  1892,  216.  The  James  theory 
of  emotion  (Psych.,  ii.,  449  ff.  ;  of.  articles  in  Mind,  Psych.  Rev., 
Phil.  Rev.,  Rev.  phil.,  etc.)  has  points  of  resemblance  both  to  the 
Lange  and  to  the  Miinsterberg  hypothesis. 

(2)  W.  Wundt,  Outlines  of  Psych.,  1897,  74;  Vorlesungen  iib. 
Menschen-  und  Thierseele,  3  Aufl.,  1897,  239;  Philos.  Studien, 
XV.,  1899,  149;  Volkerpsych.,  i.,  i,  1900,  37  ff. 

The  common  theoretical  basis  of  ( i )  is  the  reduction  of  mind 
to  sensation  elements.  The  theoretical  basis  of  (2)  seems  to  be 
the  thought  that,  because  every  emotive  attitude  is  *  unique,* 
therefore  the  simplest  characteristic  processes  of  all  emotions 
must  be  unique.  Now  the  major  premiss  in  this  argument  is, 
in  a  certain  sense,  true :  the  feeling  of  moral  obligation,  the 
pride  in  the  birth  of  your  first  baby,  the  satisfaction  in  a  new 
dining-room  carpet,  your  emotive  experience  under  the  Ninth 
Symphony,  these  are  all  *  unique '  consciousnesses,  each  specifi- 


S  37.   Afethod  of  Paired  Comparisons  151 

cally  different  from  all  the  rest,  none  reducible  to  any  one  of 
the  others.  But  (and  this  is  the  point)  is  it  because  they  are 
differently  put  together ;  because,  while  their  elements  are  the 
same,  the  elements  are  differently  selected,  proportioned,  ar- 
ranged ;  that  they  are  termed  unique  ?  Or  is  it  because  they 
contain  elements  ultimately  different  in  kind  ?  By  all  analogy, 
the  former  hypothesis  is  the  first  to  be  tested,  and  the  latter  is 
to  be  considered  only  if  the  first  utterly  breaks  down. 

For  the  theory  here  adopted,  see  KUlpe,  Outlines,  225  ff. ;  A.  Lehmann, 
Die  Hauptgesetxe  d.  menschl.  GefUhlslebens,  1892,  12  ff.,  75  ff. 

EXPERIMENT  XXI 

$  37.  The  Affective  Qualities:  Paired  Comparison.  Cantiotts 
not  noted  in  the  Text.  —  It  must  be  carefully  impressed  upon  the 
student  that  the  affective  values  of  the  curve  obtained  in  this 
experiment  are  relative  and  not  absolute.  A  colour  may  be 
judged  to  be  more  pleasant  than  26  other  colours;  and  yet  may 
be,  intrinsically,  very  weakly  pleasant.  The  point  may  be 
clinched  by  showing  O,  at  the  conclusion  of  the  tests,  that 
colour  which  has  been  most  often  preferred,  and  asking  him  to 
gauge  its  pleasantness  by  that  of  a  good  dinner,  or  a  brisk  walk, 
or  a  cool  drink  when  thirsty,  or  the  scent  of  a  flower.  In  com- 
parison with  these  and  many  other  sources  of  sense  pleasure, 
the  colour  patch  will  seem  practically  indifferent. 

If  O  promises  to  be  very  fertile  in  association,  a  short  pre- 
liminary series  of  comparisons  may  be  taken,  before  the  experi- 
mental series  begins.  The  associations  soon  lapse,  when  O 
finds  that  they  are  only  hindering  him,  and  when  the  experiment 
has  become  a  matter  of  routine.  —  On  no  account  must  O  sup- 
pose that  the  experiment  is  a  test  of  aesthetic  taste;  that  he 
*  ought  *  to  like  certain  colours  in  combination,  and  dislike  oth- 
ers. He  must  be  assured  that  every  judgment,  no  matter  what 
it  is,  is  on  precisely  the  same  level  of  value  with  every  other : 
it  is  the  judgment  that  is  recorded,  not  the  aesthetic  rightness 
or  wrongness  of  the  judgment.  The  more  passive  and,  so  to 
speak,  mechanical  he  can  be  in  face  of  the  stimuli,  the  better. 

The  required  passive  attention  to  the  colour  impressions,  and 
the  affective  reaction  upon  them,  are  incompatible  with  discur- 


152  The  Affective  Qualities 

sive  introspection.  Introspection  implies  an  active  attention  to 
a  sense  contents.  Although,  therefore,  O  may  be  questioned, 
after  the  experiment,  about  the  sense  factors  in  his  judgments 
(brightness,  saturation,  contrast,  effect  of  frame  and  contents 
as  a  Vhole  vs.  effect  of  separate  colour  squares,  influence  of 
succession  of  colours,  etc.),  and  although  any  remarks  of  the 
kind  that  he  may  volunteer  should  be  noted  down  by  Ey  yet  he 
should  by  no  means  be  encouraged  to  think  about  the  experi- 
mental conditions  or  appliances.  He  has  passively  to  live  the 
colour,  to  be  the  colour ;  and  then,  before  intellectual  processes 
have  time  to  start  up,  to  name  his  affective  response  to  it. 

Questions. — (i)  The  curve  will  certainly  show  a  preference, 
if  the  work  has  been  properly  done.  As  to  the  preference 
itself :  there  seem  to  be  two  types  of  O.  The  one  prefers  satu- 
rated colours,  — and  this  type  probably  constitutes  the  majority  ; 
the  other  as  definitely  prefers  unsaturated,  what  have  come  to 
be  called  in  the  popular  phrase  *  artistic '  colours.  The  two 
curves  printed  herewith  are  taken  from  (9's  of  the  first  type.  — 
No  rule  can  be  laid  down,  it  seems,  as  regards  preference  for 
individual  colours.  In  the  two  curves  here  given,  the  maxima 
and  minima  are  very  near  together,  as  indeed  the  whole  curves 
are  greatly  alike.  On  the  other  hand,  many  observers  of  this 
type  have  a  great  aversion  to  yellow,  which  here  stands  high. 
We  are,  genetically,  so  far  remote  from  an  intensive  affective 
reaction  to  simple  colour  patches,  that  such  differences  must  be 
expected. 

(2)  The  answer  to  this  Question  cannot  be  foreseen.  It  is, 
perhaps,  safe  to  say  that  as  a  rule  O  is  not  aware  of  his  prefer- 
ences. He  may  know  vaguely  that  he  likes  'rich '  colours  bet- 
ter than  *  poor  * ;  or  he  may  have  a  single  and  intense  liking  for 
a  certain  colour  as  seen  against  a  certain  background,  e.g.y  yellow 
upon  black,  or  blue  upon  grey :  but  it  is  doubtful  whether  he 
can,  even  approximately,  construct  his  curve  for  himself  by  in- 
trospection. Such,  at  least,  has  been  the  author's  experience. 
—  The  reason  would  be  the  same  as  the  reason  for  the  vagaries 
of  preference  just  noted,  under  (i). 

(3)  It  is,  again,  a  nice  point  whether  the  colours  have  any 
emotive  value,  apart  from   their  associations.     Is  R  an  angry 


154  The  Affective  Qualities 

colour,  and  G  a  hopeful  colour,  and  B  a  depressing  colour  ?  Or 
are  these  things  associations  merely,  —  blood  or  the  flushed  face, 
growing  vegetation,  the  steel-blue  of  a  lowering  sky  ?  It  is 
hardly  profitable  to  speculate.  It  is,  however,  worth  while  to 
note  whether  O  appears  (on  the  successive  experimental  days) 
to  judge  the  colours  according  to  his  mood,  or  to  have  a  mood 
impressed  upon  him  by  the  first  few  pairs  of  colours.  E  should 
note  down  all  indications.  In  the  author's  experience,  the 
former  alternative  is  realised. 

In  later  affective  work,  we  shall  see  reason  to  be  very  careful 
that  <9's  mood,  at  the  beginning  of  the  experiment,  is  indifferent. 
Here  indifference  is  not  required.  For  even  if  (7  be  in  a  mood 
to  dislike  everything,  he  will  still  dislike  some  things  less  than 
others  ;  and  if  he  does  that,  his  judgments  are  valid  for  our 
purpose.  Of  course,  a  mood  of  steady  indifference  is  favourable 
to  the  mechanising  of  the  whole  procedure,  which  we  said  above 
(p.  152)  was  desirable. 

(4)  Tastes  and  smells.  For  the  psychological  reasons,  see 
Outline  of  Psychology,  225  ff.  — Tastes  could  hardly  be  worked 
with,  as  there  are  so  few  taste  qualities.  Smells  have  enough 
variety,  but  are  extremely  and  insistently  associative.  However, 
it  would  be  well  worth  while  to  apply  the  method  of  paired  com- 
parisons to  them. 

Literature.  —  J.  Cohn,  Experimentelle  Untersuchungen  iiber 
die  Gefuhlsbetonung  der  Farben,  Helligkeiten  und  ihrer  Com- 
binationen.     Philos.  Stud.,  x.,  1894,  562  ff. 

§  38.  Alternative  Experiment.  —  We  may  employ  the  Method 
of  Impression  in  another  form,  substituting  'serial  judgments' 
for  'judgments  by  paired  comparison.' 

Materials.  —  Set  of  coloured  paper  squares,  7  by  7  cm. 
Piece  of  neutral  grey  (or  black,  or  white)  cardboard,  60  by  60 
cm.,  having  at  the  centre  a  window  6  cm.  square.  Cross-ruled 
paper. 

Preliminaries.  —  In  this  experiment,  the  colours  are  to  be 
presented  serially,  in  spectral  order  (or  reversed  spectral  order). 
They  must  therefore  be  numbered,  i  to  27,  in  that  order :  tint 
coming  after  tint,  and  shade  after  shade,  as  in  the  curves  of  the 
preceding  Experiment. 


II       I    I    I    1    I —  I    I   TT" - i— 

ZIZZ!I!r:s^ 


f  *■ 


156  The  Affective  Qualities 

O  is  now  called  upon  to  learn  and  standardise  a  scale  of  arbi- 
trary affective  values.     Seven  steps  can  readily  be  held  in  mind : 

1.  Very  pleasant.  5.  Just  unpleasant. 

2.  Moderately  pleasant.  6.  Moderately  unpleasant. 

3.  Just  pleasant.  7.  Very  unpleasant. 

4.  Indifferent. 

This  scale  must  be  memorised,  and  tested  in  preliminary  ex- 
periments. It  should  be  written  clearly,  e.g.^  on  a  blackboard, 
in  the  experimental  room,  in  order  that  O  may  refresh  his 
memory  of  it  at  the  beginning  of  each  series.  As  soon  as  he 
thoroughly  understands  in  what  sense  a  colour  may  be  called 
*very  pleasant,'  'moderately  unpleasant,*  etc., — and  he  must 
learn  this  by  actual  experience,  since  (as  was  said  above,  p.  i$i) 
the  affective  value  of  all  colours  is,  absolutely  taken,  very 
small,  —  he  will  find  no  difficulty  in  applying  the  scale,  and  his 
judgments  will  be  surprisingly  constant  from  series  to  series  and 
from  day  to  day.  He  must  not  assume  the  aesthetic,  but  the 
psychological  attitude;  he  must  wear  off  the  'feeling  of  unac- 
customedness '  that  arises  at  first,  when  he  is  set  down  to  find 
*  an  uninteresting  colour  patch  '  pleasant  or  unpleasant ;  and  he 
must  also  wear  off  the  feeling  that  in  such  an  experiment  every- 
thing is  uncertain  and  subjective,  and  that  the  results  must  of 
necessity  be  valueless.  Attentive  work  soon  overcomes  these 
difficulties  of  the  affective  judgment. 

Experiment.  —  The  grey  card  is  set  up  on  a  table,  at  a  con- 
venient distance  (perhaps  2  m.)  from  O.  O  sits  with  his  eyes 
closed.  E  places  one  of  the  coloured  squares,  chosen  at  ran- 
dom from  the  full  series,  behind  the  window  of  the  screen. 
The  upper  edge  of  the  paper  may  be  lightly  pasted,  or  a  pin 
may  project  through  the  card  and  the  paper  be  hung  upon  its 
point.  The  illumination  must  be  uniform  and  permanent.  At 
the  word  of  command,  O  opens  his  eyes,  and  looks  steadily  at 
the  colour.  After  2  sec.  the  colour  is  covered  or  removed,  and 
O  enters  his  judgment  (i,  or  2,  or  3,  etc.)  on  a  paper  at  his  side. 
He  may  write  out  any  introspective  observations  that  occur  to 
him ;  but  these  should  not  be  encouraged,  unless  they  refer  to 


{  ZS.    Sena/  Method  157 

sources  of  error.  He  then  closes  his  eyes.  After  the  lapse 
of  10  sec,  E,  who  has  placed  the  colour  next  in  spectral  order 
'to  right  or  left)  behind  the  screen,  gives  a  second  signal,  and 
liie  experiment  is  repeated.  In  this  way,  E  works  during  a 
single  sitting  straight  through  his  colour  series  to  the  end  (or 
beginning)  of  the  spectrum,  and  then  round  again  from  the 
beginning  (or  end)  of  the  spectrum  to  his  starting-point.  At 
iie  end  of  the  experiment,  he  has  materials  for  platting  a 
curve:  the  abscissae  are  the  colours,  in  spectral  order;  the 
zero-ordinate  is  the  affective  value  4,  indifference ;  and  the 
positive  and  negative  ordinates  are  the  values  1-3  and  5-7 
respectively. 

The  experiment  should,  however,  be  repeated  three  or  four 
times ;  each  time  from  a  different  starting-point  (absolute,  as 
red,  blue,  etc. ;  and  relative,  as  tint  or  shade),  and  each  time  in 
a  different  spectral  direction  (to  right  or  to  left).  The  curve 
values  must  then  be  averaged  from  the  combined  results.  If 
there  is  fluctuation  of  judgment  as  regards  any  particular  colour, 
the  mean  of  the  different  figures  must  be  taken  and  entered  in 
the  curve.  It  will  be  found,  as  was  said  just  now,  that  (when 
once  the  norm  has  been  established)  the  judgments  are  sur- 
prisingly  constant. 

Points  to  notice  are  the  following,  (i)  If  the  method  is  to 
be  valid,  O  must  keep  in  mind  the  serial  nature  of  the  impres- 
sions. There  is  no  difficulty  about  this  :  the  coming  colours  are 
expected  in  a  definite  order,  and  each  little  group  of  tints-colour- 
shades  is  apprehended  as  a  link  in  a  total  chain  of  colour. 
Still,  the  point  must  be  noticed.  Any  tendency  on  the  part  of 
O  to  judge  of  the  colours  as  isolated,  separate,  independent 
stimuli  would  be  disastrous  for  the  method.  (2)  The  affective 
curve  in  this  case  is  no  more  absolute  than  are  the  curves  of 
the  preceding  Experiment.  There  is  no  guarantee,  e.g.,  that  7 
is  as  far  below  4  as  i  is  above  it ;  the  size  of  the  steps  above 
and  below  the  abscissa  may  be,  absolutely,  very  different.  And 
again :  there  is  no  guarantee  that  the  figures  as  applied  to 
colours  mean  the  same  thing  as  they  would  if  applied,  e.g.,  to 
smells.  Indeed,  the  contrary  of  this  is  pretty  obvious  :  a  '  very 
pleasant  *  smell  is  a  great  deal  more  pleasant  than  a  '  very  pleas- 


158  The  Affective  Qualities 

ant  *  colour.  Within  its  limits  of  relativity,  however,  the  curve 
is  accurate  enough.  (3)  Careful  watch  must  be  kept  for  possi- 
ble errors  residing  in  memory  of  past  judgments  of  similar  im- 
pressions, fatigue  due  to  the  tedium  of  a  long  series  progressing 
in  a  known  direction,  influence  upon  present  judgment  of  the 
judgments  last  passed,  etc.  The  first  of  these  will  hardly  enter 
into  the  results  of  a  conscientious  observer ;  the  second  can  be 
guarded  against  by  observation  of  the  attitude  of  the  observers 
to  the  work ;  the  third  can  be  avoided  both  by  explicit  direc- 
tions to  Oy  and  by  instructing  him  to  fold  his  record  paper  down 
after  each  writing,  so  that  he  does  not  see  how  many  *  i  '  or  *  2,* 
etc.,  he  has  written  in  a  given  hour. 

Literature.  —  D.  R.  Major,  On  the  Affective  Tone  of  Sim- 
ple Sense  Impressions.     Amer.  Journ.  of  Psych.,  vii.,  1895,  57  ff. 

J.  Cohn,  Gefuhlston  und  Sattigung  der  Farben.  Philos. 
Stud.,  XV.,  1899,  279  ff. 

EXPERIMENT   XXU 

§  39.  The  Affective  Qualities:  Involuntary  Movement.  Cau- 
tions not  noted  in  the  Text.  —  Very  great  care  must  be  taken,  in 
this  experiment,  to  avoid  any  suggestion  to  the  students  as  to 
what  result  is  to  be  expected.  We  know,  from  various  '  spirit- 
ualistic '  tests  and  reports,  how  extremely  suggestible  the  plan- 
chette  is :  and  the  automatograph  is  merely  the  planchette, 
renamed  for  scientific  uses.  If  a  pair  of  students  chance  to  know, 
from  reading  or  lectures,  what  the  correlation  between  affective 
quality  and  involuntary  movement  is,  they  should  be  cautioned 
{a)  to  tell  no  one  else  in  the  laboratory  what  they  know,  and 
(b)  to  keep  themselves,  as  far  as  possible,  without  prejudice. 
There  will,  in  all  probability,  be  several  students  who  do  not 
know  the  correlation :  their  results  may  be  used  as  a  check  upon 
the  rest,  and  displayed  to  the  whole  class  at  the  conclusion  of 
the  experiment.  Those  who  do  know  will,  probably,  get  'too 
good '  tracings  at  first ;  then  they  will,  by  counter-suggestion, 
get  no  correlation  at  all;  but  finally,  if  they  are  serious  and 
painstaking,  they  will  be  able  to  show  records  of  precisely  the 
same  character  as  those  obtained  from  ignorant  subjects.  —  All 
this  shows  the  necessity  (mentioned  in  the  text)  of  preserving 


$  39*   Involuntary  Movement  159 

every  record,  together  with  its  introspective  label,  and  entering 
an  account  of  the  complete  experiment  through  all  its  stages  in 
the  laboratory  note-book.  If  the  correlation  is  not  realised, 
there  is  always  some  definite  reason  for  failure ;  and  the  obser- 
vation of  '  bad '  records,  alongside  of  the  introspective  account 
of  their  conditions,  may  be  as  instructive  as  that  of  a  page  of 
*  correct '  results. 

An  obvious  difficulty  in  the  way  of  this  experiment  is  that  E 
IS  observing  the  correlation,  which  it  is  the  object  of  the  experi- 
ment to  establish,  from  the  moment  that  he  begins  to  subject  O 
to  pleasant  or  unpleasant  stimuli.  It  can  partly  be  overcome 
by  instructing  E  not  to  compare  the  tracings  with  O's  introspec- 
tions until  he  himself  has  served  as  O.  He  is  simply  to  con- 
tinue the  experiment,  with  the  scent-series  at  his  command,  until 
O  says :  "  I  have  had  my  six  good  and  six  bad  smells."  The 
aflFective  value  of  the  stimuli  varies  so  largely  with  different  O's, 
that  ^s  conjectures  and  expectations  will  probably  be  much  at 
fault,  and  he  will  enter  upon  his  own  introspective  task  with  an 
open  mind.  If,  however,  the  experiment  chance  to  proceed  so 
smoothly  that  the  correlation  comes  out  from  the  first,  E  must 
be  treated  in  the  same  way  as  the  other  students  who  know 
beforehand  what  their  results  should  be. 

The  experimenting  room  should  be  as  free  from  foreign 
odours  and  from  draughts  of  air  as  possible. 

Materials. — There  is  another  form  of  automatograph  on 
the  market :  a  sheet  of  glass,  sliding  on  three  steel  balls  upon 
another  sheet,  on  which  in  turn  the  paper  is  placed.  The  upper 
glass  carries  the  subject's  arm  and  hand,  and  is  furnished  in 
front  with  a  projecting  piece  in  which  the  stylus  is  set.  This 
apparatus  is,  however,  much  more  expensive,  while  it  is  mechani- 

illy  less  satisfactory,  than  that  described  in  the  text. 

Tin  dishes  filled  with  odorous  material  are  recommended  be- 
cause they  offer  a  fairly  wide  surface  to  the  nostrils,  and  because 
they  can  easily  be  scalded,  for  cleaning,  without  fear  of  break- 
age. Glass  tubes,  widening  above,  the  cup-shaped  end  filled 
with  cotton-wool  soaked  in  the  required  liquid,  may  be  substi- 
tuted for  them  in  certain  cases:  but  the  results  are  less 
itisfactory. 


i6o  The  Affective  Qualities 

The  following  scents  may  be  recommended 


{a)  Pleasant. 

Crab-apple  blossom. 

White  rose. 

Oil  of  orange. 

Jockey  Club. 

Heliotrope. 

Oil  of  cinnamon. 


{b)  Unpleasant. 

Carbon  disulphide. 
Rancid  cheese. 
Wood  alcohol. 
Asafoetida. 
Castor  oil. 
Cod  liver  oil. 


2 


3 


The  above  will  be  found  pleasant  and  unpleasant,  as  described, 
by  most  observers.  Stimuli  that  vary  in  their  affective  value 
from  one  O  to  another,  but  usually  produce  marked  effect,  are : 
spirits  of  camphor,  oil  of  cloves,  oil  of  peppermint,  oil  of  anise, 
tar,  kerosene,  citronella  oil,  oil  of  cajeput.  Others  will  doubt- 
less suggest  themselves  in  the  course  of  the  experiments,  if  they 
are  required.  No  stimulus  should  be  employed  which  sets  up 
marked  pricking,  burning,  choking,  etc.,  sensations  in  addition 
to  the  smell  quality  proper. 

Experiment.  —  Care  must  be  taken  that  O  does  not  change 
his  manner  of  breathing  when  the  stimulus  is  applied.  There 
is  a  temptation  to  *take  long  breaths,'  which  should  be  resisted. 

The  normal  tremor 
with  this  apparatus  is 
a  pulsating  movement, 
—  travelling  laterally 
(from  left  to  right,  or 
from  right  to  left,  indif- 
ferently) over  a  space 
of  I  to  3  mm.  The 
line  will  often  return 
upon  itself,  so  that  its 
waves  are  obliterated, 
and  only  a  small  irreg- 
ular white  blotch  is 
left  on  the  paper.  The 
objective  tests  of  a  true  normal  are  (a)  small  excursion  of  the 
point,  and  {b)  inconstancy  of  direction.  To  these  the  subjective 
test  of  introspection  must  be  added. 


Fig.  20. —  Records  of  involuntary  movement,  i,  2,  3, 
normal  tremors;  4,  5,  'unpleasant'  tracings;  6,  7, 
*  pleasant '  tracings.  The  records  have  been  some- 
what simplified  in  transcription  from  the  smoked 
paper,  but  their  dimensions  are  accurately  shown. 


§  39-   IfitHfiumUay  Mavewuni 


i6i 


With  distinctly  pleasant  stimulation,  the  point  travels  laterally 
outward  (i./.,  in  the  experiment  described,  from  left  to  right); 
the  arm  is  extended.  The  pulsations  of  breathing  are  apparent. 
There  is  no  return  of  the  line  upon  itself,  and  (for  the  most 
part)  no  arrest  of  movement  at  any  point.  The  tracing  may 
reach  the  length  of  2  cm.,  while  the  movement  is  still  entirely 
involuntary,  i>.,  unknown  to  O. 

With  distinctly  unpleasant  stimulation,  the  point  travels  in- 
ward ;  the  arm  is  flexed.     The  line  is  usually  flatter  than  in  the 


Fig.  21. 


preceding  case ;  the  breathing  waves  are  less  apparent.  In  the 
case  of  an  odour  so  unpleasant  as  that  of  rancid  cheese,  the  trac- 
ing may  be  as  long  as  4  cm.,  and  still  give  no  evidence  of  itself 
to  introspection. 

Questions.  ( i )  Yes.  Pleasantness  is  correlated  with  move- 
ments of  extension  ;  unpleasantness  with  movements  of  flexion. 

(2)  Pleasant  things  are  'naturally*  the  things  that  we  reach 
out  after,  open  our  arms  to ;  unpleasant  things  are  those  that 
we  shrink  from, — things  that  make  us  *draw  ourselves  in  *  when 
we  meet  them.     Since,  in  the  main,  pleasant  things  are  biologi- 


1 62  The  Affective  Qualities 

cally  good  for  us,  and  unpleasant  things  bad,  the  biological  sanc- 
tion of  these  movements  is  evident. 

(3)  Probably,  the  unpleasants  are  the  stronger.  It  is  usually 
easier  to  find  a  scent  that  O  *  loathes '  than  to  find  one  that  he 
Moves.* 

(4)  The  idea  might  *  suggest '  an  imitative  movement  to  the 
planchette.  If  O  were  thinking,  e.g.y  of  a  horse,  or  person,  or 
name,  the  stylus  might  tend  to  trace  the  outline  of  the  horse  or 
person,  or  the  letters  of  the  name. 

Instruments.  —  The  automatograph  referred  to  above,  p.  1 59, 
is  that  of  J.  Jastrow  (Amer.  Journ.  of  Psych.,  iv.,  1892,  398 ;  v., 
1892,  223):  sold  by  the  Chicago  Lab.  Supply  Co.  for  $6.00.  A 
simpler  form  is  sold  for  $1.00.  Fig.  21  illustrates  the  tridimen- 
sional analyser  of  R.  Sommer  (Zeits.  f.  Psych.,  xvi.,  1898,  275): 
sold  by  Schmidt,  Mk.  85.  For  E.  B.  Delabarre's  finger-movement 
recorder,  see  L'Ann^e  psych.,  i.,  1895,  532  (Verdin,  Fr.  120). 

Literature.  —  H.  Miinsterberg,  Beitrage  zur  experiment. 
Psychologic,  iv.,  1892,  216;  G.  van  N.  Dearborn,  Psych.  Rev. 
Mon.  Suppl.  9,  1899,  33  ff.  (cf.  Psych.  Rev.,  iv.,  1897,  453). 

EXPERIMENT  XXIU 

§  40.  The  Affective  Qualities :  Dynamometry.  Cautions  not 
noted  in  the  Text.  —  The  difficulty  arises  here  that  arose  in 
Exp.  XXII. ;  Ey  even  if  he  were  ignorant  of  the  correlation 
before  the  experiment  began,  will  learn  it  in  the  course  of  his 
observation  of  (9's  pulls.  Fortunately,  the  *  suggestion  '  is  not 
serious.  The  movement  in  the  present  instance  is  voluntary ; 
the  pull  is  to  be  consciously  maximal.  Any  'suggested'  letting- 
up  of  pull,  on  unpleasant  stimulation,  and  any  similar  increase 
in  pull,  on  pleasant  stimulation,  will  reveal  themselves  in  intro- 
spection as  artificial.  One  cannot  honestly  deceive  oneself  as  to 
whether  one  is  pulling  one's  hardest  or  not.  E  will  therefore 
be  able,  by  attending  to  the  pointer  and  from  the  suggestion,  to 
give  clean  results. 

Some  (9's  declare  from  the  outset  that  they  cannot  make  a 
maximal  effort  without  pain.  Such  statements  can  always  be 
traced,  on  examination,  to  an  awkward  position  of  the  wrist  or 
an  insufficient  padding  of  the  hook. 


{  40.    Voiuniary  Movtment  163 

Since  the  experiment  requires  a  continuous  attention  for  i  to 
15  min.,  and  O  is,  by  hypothesis,  not  a  very  highly  trained 
observer,  there  will  almost  certainly  be  a  number  of  *bad' 
records  due  to  distraction  (see  below,  answer  to  Question  5). 
It  is  well  to  bear  this  in  mind,  —  both  because  the  fact  of  inat- 
tention may  help  to  explain  results  otherwise  inexplicable,  and 
because  it  prevents  the  Instructor  from  making  too  severe 
demands  upon  O. 

Plenty  of  time  for  rest  must  be  allowed  between  experiment 
and  experiment. 

Materials.  —  By  a  very  simple  arrangement  of  cord  (tied  to 
the  pointer  bar),  counter-weight  and  pulleys,  a  writing-point  can 
be  attached  to  the  dynamometer,  and  the  curves  traced  continu- 
ously (not  taken  merely  at  5  sec.  intervals)  on  the  smoked  paper 
of  the  kymograph.  The  details  of  the  effect  of  pleasant  and 
unpleasant  stimulation  then  come  out  more  clearly.  For  all 
practical  purposes,  however,  the  arrangement  described  in  the 
text  is  sufficient. 

Care  must  be  taken  not  to  overfill  the  bulbs  of  the  syringes. 
A  too  large  quantity  of  the  stimulus  solution  fails  of  its  effect ; 
the  vomiting  reflex  is  s.et  up,  and  O  spits  it  all  out.  —  Many 
other  devices  for  the  application  of  stimulus  have  been  tried. 
Cs  head  is  bent  down,  with  the  effort  of  pulling,  so  that  his 
mouth  is  hard  to  reach.  The  syringe,  carefully  used,  has  been 
found  preferable  to  burettes,  bent  spoons,  flexible  tube  and  bot- 
tle, etc. 

The  taste  solutions  cannot  be  prescribed,  as  there  are  great 
differences  of  individual  like  and  dislike.  The  following  will, 
however,  probably  be  found  useful :  castor  oil,  cod  liver  oil, 
quinine  (.002  to  i  %  solution  of  the  hydrochlorate),  strong  cof- 
fee, 33%  of  955fe  alcohol,  essence  of  wintergreen  (5%  solution), 
essence  of  peppermint  (5%),  essence  of  anise  (5%),  syrup  of 
orange(i5%),  tar  (wine  of  tar,  5%),  lime  juice  (10%),  syrup  of 
cherry  ( 1 5%  X  maple  syrup. 

Experiment. — (i)  The  normal  curve  in  this  Experiment 
approximates  very  closely  to  a  straight  line  ;  i.c^  the  strength 
of  pull  decreases  in  direct  proportion  to  the  time  of  pull.  After 
a  certain  time  has  elapsed  (60  to  90  sec,  as  mentioned  in  the 


1 64 


The  Affective  Qualities 


KQ. 

11.S 

10.8 
10.0 
•.B 

•.0 

•.s 

•.0 
7.B 

i 

\, 

1 

V 

/ 

u 

\ 

/ 

\ 

s 

"V 

V 

s 

s 

s 

I 

7.0 

0.B 

\ 

V 

2 

V 

\ 

L. 

e.0 

«.B 

s 

N 

•«^ 

/ 

\ 

\ 

\ 

B.0 
4.8 
4  0 

\ 

\ 

s 

\ 

•EC."c 

S    1 

0    1 

B    2 

fl   ? 

8     S 

10  . 

8    4 

0    ♦ 

b'b 

0  a 

0 

0    6 

5     7 

0    7 

8    8 

0    8 

8 

Fig.  22. — Two  'normal'  records  from  the  same  O -.  I 
the  first,  2  the  third  taken.  Shows  the  regularising 
effect  of  practice. 


text),  the  curve  runs  at  a  low  level  parallel  with  the  abscissae ; 

it  is  useless  to  continue  the  experiment  to  this  point,  as   O 

merely  becomes  ex- 
tremely fatigued, — 
and  thus  badly  dis- 
posed for  the  fol- 
lowing experiments. 
The  simple  charac- 
ter of  the  normal 
curve  makes  it  an 
easy  matter  to  de- 
termine the  affec- 
tive correlations  re- 
quired. 

(2)  Since  we  do 
not  ask  O  to  plug 
his  nostrils,  we  are 
stimulating  the  or- 
gans  both   of  taste 

and  smell ;  the  first  expiration,  after  the  injection  of  the  liquid 

into  the  mouth,  will  set    kg. 

up  a  smell  sensation.    ,0.8 

This  double  effect  in-    ^«>.o 

creases   the  affective 

value    of    the     stim- 
uli   employed.       But 

it   means,  of   course, 

that    care    must     be 

taken  to  prevent  any 

premature       recogni- 
tion of   the  stimulus 

by  O.     The  syringes 

must    be   filled    in 

different    room     from    Y\g.  23.  —  Typical  curve  for  high  degree  of  pleasantness. 

that     in    which     the 

experiments  are  performed,  and  their  tubes  kept  closed  until  the 

moment  for  use  arrives. 

The  reason  that  the  stimulus  is  applied  in  the  form  of  a  taste. 


a        8,8 
«•     8EC    0 


^ 

^ 

r 

\ 

s 

\ 

\ 

\ 

\ 

\. 

1 

\ 

^ 

1 

\ 

1 

\ 

\ 

\ 

\ 

4 

MA 

>LE 

8Y 

^UP 

\ 

^ 

\ 

\ 

\ 

8    10     16    20    26     30     35    40    46    60    58     60    86    70    76 


§  40-    y«fimtary  Mwtmtnt 


i6s 


11. • 

\ 

^ 

" 

"" 

^ 

■~ 

■" 

'~ 

\ 

h- 

\ 

••• 

s 

•if 

\ 

s 

S 

T  t 

\ 

k 

T.t 

^ 

t 

••• 

N 

•  A 

s 

^ 

nu 

<e 

waLi 

s 

-\ 

f'-^ 

s 

4.4 

s 

4.0 

—m 

s 

rather  than  in  that  of  a  smell,  is  that  O  is  more  likely  to  be  dis- 
tracted by  the  arrangements  for  giving  the  latter.     We  must 
remember  that  O  is  concentrate 
edly  attentive  to  the  visual  im- 
pression of  the  pointer.     When 
we  apply  our  stimulus,  we  must 
try  not  to  divert  his  attention 
from  this  impression.     Our  ob- 
ject is  to  bring  it  about  that, 
whereas  he  was  before  merely 
•attentive   to   the   pointer,*    he 
is  now  'attentive  influenced-by- 
castor-oil  [or  whatever  the  stim- 
ulus  may  be]   to  the  pointer.*  ________________ 

We  have  no  desire  to  make  him  M^'i  Mb  u  *  a  jfc  n  4*  4  «  u* 
inattentive  to  the  pointer,  and    Fic  24. -Typical  curve  of 'bUnk' ex- 

*  pcriment. 

attentive  to  the  castor  oil.     But 

the  preparations  for  olfactory  stimulation  prove,  in  practice,  to 
have  a  much  greater  distracting  eflfect  than  does  E's  putting 
out  of  the  hand  to  squeeze  the  bulb  of  the  taste-syringe. 

The  correlation,  as 
shown  both  by  these 
rough  5-second  curves 
and  by  the  continuous 
tracings  of  the  kymo- 
graph, is  as  follows. 
When  a  vety  pleasant 
stimulus  is  applied, 
the  curve  drops  a  lit- 
tle, and  then  quickly 
rises  again,  to  a  point 
above  the  level  of  the 
normal.  This  higher 
level,  relatively  to  the 
normal,  is  maintained 
till  the  end  of  the  experiment.  When  a  very  unpleasant  stimulus  is 
applied,the  curve  takes  a  decided  drop  ;  then  recovers  a  little ;  but 


11.« 

'si 

" 

" 

\ 

s 

a   A 

s 

s 

Ct 

^ 

^ 

\ 

a    a 

\ 

V 

s 

•  0 

s 

L 

N 

>^ 

^ 

~ 

if 

•  < 

on 

n 

> 

V 

> 

^ 

s 

2  g 

V 

ftS. 

1 

1  f 

•  1 

•  1 

•  1 

«  1 

•  1 

W   4 

«   4 

•  • 

»  • 

• 

W  4 

M   1 

■0    T 

•    1 

»  1 

N   M 

Fia  t$.  — Typical  cunrc  of  unpleaaantneM. 


1 66  The  Affective  Qualities 

remains  for  a  long  time  (if  not  till  the  end  of  the  experiment) 
relatively  lower  than  the  normal. 

Distilled  water,  and  other  indifferent  stimuli,  leave  the  normal 
curve  unaffected,  save  for  a  slight  drop  immediately  following 
the  injection. 

Questions. — (i)  Yes.  The  pleasant  stimulation  makes  us 
stronger,  the  unpleasant  makes  us  weaker. 

The  question  may  arise,  why  the  *  pleasant  *  curve  does  not 
rise  at  once,  on  the  introduction  of  the  stimulus,  instead  of 
dropping  and  then  rising.  The  answer  seems  to  be,  that  the 
drop  corresponds  to  a  momentary  distraction  of  attention  from 
the  work  in  hand,  —  a  dividing  or  confusing  of  consciousness, 
due  to  the  interruption  of  the  hitherto  undisturbed  effort.  The 
pointer  does  not  hold  its  place  at  the  focus  of  consciousness,  and 
consequently  does  not  hold  its  place  on  the  scale.  As  soon 
as  the  confusion  is  over,  and  consciousness  settles  down  to 
renewed  concentrated  attention,  the  effect  of  the  stimulus 
becomes  apparent.  As  was  noted  above,  the  drop  will  be  found 
in  the  *  blank  *  curves  as  well  as  in  the  pleasant  and  unpleasant 
records.  —  Cf.  Lehmann,  Hauptgesetze,  95. 

(2)  Things  that  are  biologically  good  for  us  (the  pleasant 
things)  would  'naturally'  make  us  stronger;  and  things  that  are 
biologically  bad  for  us  would  make  us  weaker. 

(3)  The  pleasant. 

(4)  Yes :  the  strengthening  of  pull  is  more  clearly  marked 
and  longer  continued,  in  most  cases,  than  the  weakening. 

(5)  The  distraction,  mentioned  above.  It  is  not  difficult,  in 
Exp.  XXII.,  to  see  what  is  meant  by  exchanging  an  'odourless 
dreamy  reverie'  for  an  *  apple-blossom  dreamy  reverie' ;  not  dif- 
ficult to  let  one's  thoughts  float  off  in  odour,  while  previously 
they  had  floated  away  uncoloured  by  smell  sensation.  On  the 
other  hand,  it  is  not  easy  here  for  O  to  grasp  what  is  required 
of  him,  and  not  easy  for  him,  at  any  rate  in  the  first  few  trials, 
to  act  out  what  he  has  understood.  He  is  far  more  likely  to 
attend  to  the  taste  impression  than  to  give  a  taste  attention  (in 
place  of  the  previous  tasteless  attention)  to  the  pointer.  Close 
introspection  enables  him  to  overcome  the  difficulty. 

Additional   Question.  —  We   have   spoken  in  the  text  of 


§  41*    T^^f  Hand  Dynamimtter  167 

*the  attention  being  concentrated  upon  the  pointer/  of  'the 
pointer  being  at  the  focus  of  consciousness/  etc.  Such  expres- 
sions are,  of  course,  very  imperfect  representations  of  the  reality. 
The  attentive  consciousness  of  the  experiment  consists  (i)  of 
the  visual  perception  of  the  pointer  and  the  tactual  perception 
of  the  'effort*  exerted,  (2)  of  various  peripheral  cues,  which 
taken  all  together  spell  'effort,'  —  tightening  of  the  scalp,  set- 
ting of  the  jaw,  frowning,  clenching  of  the  unemployed  hand, 
settling  of  the  head  down  upon  the  shoulders,  etc.,  and  (3)  of 
ideas,  clustering  round  and  reinforcing  the  two  primary  percep- 
tions, and  differing  in  source  and  composition  from  individual  to 
individual. 

If  O  is  sufficiently  advanced,  he  may  be  required  to  analyse, 
by  introspection,  his  own  attentive  consciousnesses  during  the 
experiment.  If  the  task  appears  too  difficult,  the  Instructor 
should  indicate  to  him,  in  general  outline,  the  processes  of  which 
these  consciousnesses  arc  composed. 

§  41.  Alternative  Experiment.  — This  experiment  may  be  per- 
formed, not  quite  so  easily,  as  follows. 

Materials.  —  Hand  dynamometer.  [This  consists  of  an 
oval  steel  frame,  about  12.5  cm.  long,  and  6  cm.  broad  at  its 
widest  part,  carrying  within  it  a 
gear  system  whereby  the  amount 
of  squeeze  in  kg.  is  indicated  by 
a  pointer  upon  a  scale.] 

Set  of  pleasant  and  unpleasant 
odours. 

Small  shallow  tin  dishes.  I^g.  a6.— Hand  dynamometer  (Zim- 

^  ,,,.  ,  mermann,  Mk.  27. co;    Collin,  Fr. 

Preliminaries.  —  The    dyna-      ^^,  ^^ji^^  p,.  l^y   ^rhe  instru- 

mometer  must  be  carefully  padded         ment  has  two  kg.  scales,  an  inner 

with    cotton   wool    and    soft    cloth,         »cale  for  «,ueeze.  and  an  outer  «:alc 

.         ,  .for  pull.  —  A  dynamograph  is  sold 

so  that  the  squeezing  is  not  pain-       byVerdin  for  Fr.130. 

ful.     O  must  practise  the  squeeze, 

taking  care  that  (a)  the  position  of  arm  and  hand,  and  (b)  the 

time  of  squeeze  remain  constant.      Thus,  the   squeezes   may 

always  be  taken  with  the  arm  held  down  straight  by  the  side 

of  the  chair ;  and  the  squeezing  may  be  done  in  time  with 

the  beats  of  a  metronome.     When  O  has  attained  to  a  fair 


1 68  The  Affective  Qualities 

degree  of  regularity  in  these  respects,  and  when  his  maximal 
squeezes  are  fairly  constant,  the  experiment  may  begin. 

Difficulties  will  almost  certainly  arise  in  regard  to  the  stimuli. 
The  odours  required  for  the  experiment  must  be  very  distinctly 
pleasant  and  unpleasant,  if  their  affective  correlation  is  to  come 
out  clearly.  It  is  well  {a)  to  find  out  from  O  beforehand  what 
smells  he  likes  and  what  he  dislikes,  and  to  choose  the  stimuli 
accordingly ;  and  {b)  to  record  the  affective  value  of  each  stimu- 
lus actually  employed  in  terms  of  an  arbitrary  scale.     Thus  : 

1  might  mean  *  indifferent,' 

2  "  "     *  moderately  pleasant '  or  *  unpleasant,'  and 

3  "  "     '  distinctly  pleasant '  or  '  unpleasant.' 

This  scale  is  explained  to  O  before  the  experiment  begins. 

Experiment.  —  (i)  We  first  find  our  normal.  O  sits  at  the 
table  with  closed  eyes.  The  dynamometer  is  put  into  his  hand. 
At  the  word  "  Now ! "  he  gives  a  maximal  squeeze.  O  then 
hands  the  instrument  to  £",  who  records  the  kg.  reading  of  the 
scale. 

(2)  O  sits  as  before.  E  puts  the  dynamometer  into  his  hand. 
At  the  word  "Ready!"  a  dish  of  smell  solution  is  held  under  his 
nostrils,  and  he  takes  three  full  breaths.  Then,  at  the  word 
**  Now ! "  he  squeezes  as  hard  as  he  can.  E  again  takes  the 
reading.  O  assigns  to  the  stimulus  the  value  i,  2  or  3,  as  the 
case  may  be. 

To  make  the  results  of  this  experiment  pure,  the  scents  should 
work  simply  and  solely  for  the  three  breaths,  and  for  no  longer. 
They  should  be  kept  in  a  different  room  from  that  in  which  O  is 
sitting,  and  should  be  carried  out  of  the  room  as  soon  as  they 
have  been  smelled.  Moreover,  the  room  should  be  thoroughly 
aired  out  between  test  and  test. 

Another  great  source  of  error  is  fatigue.  Not  more  than  six 
tests  should  be  taken  in  the  course  of  an  hour,  and  these  should 
be  so  arranged  that  the  effects  of  practice  and  fatigue  are  as 
nearly  as  possible  equalised.  It  is  not  well  that  O  and  E  should 
alternate,  test  and  test  about,  —  so  that  the  hour's  work  gives 
12  tests;  for  O  must  remain  passive  and  steadily  disposed 
throughout  the  sitting,  if  the  results  are  to  be  valid.     To  pre- 


§  41*    Tks  Hand  Dynamometer 


.69 


vent  tedium,  O  may  be  allowed  to  fill  in  the  time  with  some 
light  and  simple  occupation  :  sewing,  knitting,  etc,  magazine  or 
newspaper  reading,  easy  laboratory  tasks  such  as  the  cutting  of 
coloured  paper  discs,  have  proved  suitable.  Conversation  is  apt 
to  be  exciting,  and  to  spoil  the  results. 

The  following  are  typical  results  (O  a  woman).  —  Right  hand 
squeezes.     Unit  i  kg. 


Nocaui. 

23.0 
24^ 

26.5 
27.0 

(crab-apple  blossom) 
(white  rose) 

21.0 
22.0 

(carbon  disulphide) 
(wood  alcohol) 

25.0 

25.0 
26.0 

(oil  of  anise) 
(spirits  of  camphor) 

21.0 
22.5 

(stale  cheese) 
(burnt  hair) 

In  all  these  results  the  stimuli  had  the  affective  value  3 
assigned  to  them  by  O.  The  readings  are  to  the  nearest  half- 
kg.     Each  set  of  6  experiments  was  made  at  a  single  sitting. 

It  is  clear  that  the  *  pleasant '  squeeze  is  always  the  strongest, 
the  'unpleasant  *  the  weakest.    If  we  average  the  results,  we  get : 

Normal  23.7  ±  .7  Pleasant  26.1  ±  .6  Unpleasant  21.6  ±  .8. 

This  interrelation  remains  constant  from  day  to  day,  although 
the  normal  varies  somewhat  (even  after  practice)  with  variation 
in  d7's  general  condition,  and  the  relative  effect  of  pleasant  and 
unpleasant  stimulation  varies  also  with  (^'s  disposition  at  the 
time  of  the  experiment.  The  following  series,  from  the  same  O, 
was  taken  on  a  day  when  the  observer  was  feeling  unusually 
well. 


PLBASAVr. 


Unplsasaitt. 


27.0 
27.0 


27.5 
28.5 


(oil  of  cinnamon) 
(oil  of  anise) 


24.5 
21.5 


(stale  cheese) 
(rubber  cement) 


or,  averaged  : 

Normal  27.0  ±  o  Pleasant  28.0  ±  .5  Unpleasant  23.0  ±  1.5. 

Here  the  unpleasants  had  more  power  to  reduce  the  muscular 
strength  than  the  pleasants  had  to  increase  it. 


70 


The  Affective  Qualities 


In  the  results  quoted,  the  differences  are  all  too  great  to  be 
explained  by  chance.  But  were  they  smaller,  their  unbroken 
constancy  throughout  a  long  series  of  trials  would  be  strong 
evidence  in  favour  of  their  validity. 


Fig.  27 


Instruments.  —  Fig.    27   shows  A.   Mosso's  ergograph  and 
arm-rest  (Willyoung,  ^45;  Verdin,  Fr.  175);  Fig.  28,  J.  McK. 


Fig.  28. 


Cattell's  combined  spring  and  weight  ergograph  (Horstmann, 
Columbia  Univ.  Lab.,  $35).  Another  spring  ergograph  is 
figured  and  described  by  A.  Binet  and  N.  Vaschide,  L'Ann^e 


{  42.    TA/  PUtkyswMgmph  171 

psych.,  iv.,  1898,  305.  The  crgograph  may  replace  the  dyna- 
mometer  in  this  experiment  For  its  use,  see  A.  Mosso,  La 
fatigue,  1894,  53  fF. ;  A,  Binet  and  V.  Henri,  La  fatigue  intellec- 
tuelle,  1895,  175  ff- ;  A.  Binet  and  N.  Vaschide,  L'Ann^c  psych., 
iv.,  1895,  253. 

Literature.  —  On  the  general  correlations  brought  out  by 
this  and  the  following  experiment,  see  Kulpe,  Outlines,  245  f. ; 
A.  Lehmann,  Die  Hauptgesetze  d.  menschl.  Gefuhlslebens, 
1892,  82,  86,  89,  91,  112.  Cf,  also  A.  Binet  and  J.  Courtier, 
L*Ann^  psych.,  iii.,  1897,  65  ff. 

On  the  use  of  the  dynamometer,  see  Binet  and  Henri,  La 
fatigue  intellectuelle,  1895,  172;  A.  Binet  and  N.  Vaschide, 
L'Ann^  psych.,  iv.,  1898,  245. 


EXPERIMENT  XZIV 

$  42.  The  Affective  Qualities :  the  Plethysmographic  Method. 
Cautions  not  noted  in  the  Text,  —  The  difficulty  of  suggestion  to 
E  again  confronts  us.  But  both  O  and  E  should  now  know 
enough  about  afifective  work  to  realise  that  '  honesty  is  the  best 
policy.*  And  C7's  introspective  accounts  (of  which  more  presently) 
can  only  serve  to  confirm  E  in  his  resolve  to  resist  suggestion, 
and  let  the  experiment  take  care  of  itself. 

E  must  not  look  for  change  in  the  curve  at  the  precise  instant 
of  the  application  of  stimulus :  a  stimulus  takes  an  appreciable 
time  to  act.  Neither  must  he  assume  that  the  change  will  end 
at  the  precise  instant  of  the  removal  of  stimulus :  the  after- 
effect, as  will  be  seen  presently,  is  an  integral  part  of  the  phe- 
nomenon under  observation.  On  the  other  hand,  the  change 
must  always  be  definite,  clean-cut,  restricted  in  time.  If  this  is 
not  the  case,  there  are  sources  of  error,  physical  or  psychological, 
which  have  been  left  out  of  account. 

Materials. — The  two  kinds  of  stimulus  best  adapted  for 
this  experiment  seem  to  be  those  of  smeU  and  hearing.  Taste 
stimuli  can  hardly  be  administered  without  some  shaking  and 
jarring  of  the  immersed  arm,  while  for  light  stimuli  the  eyes 
must  be  opened,  —  and  it  is  best  on  all  accounts  to  keep  them 
dosed.     Touch  can  scarcely  be  appealed  to,  as  the  immersed 


1/2  The  Affective  Qualities 

arm  is  giving  clear  and  massive  sensations  of  pressure  and 
temperature.  On  the  other  hand,  agreeable  and  disagreeable 
smells  are  easily  found  and  easily  presented  :  O  must,  of  course, 
be  cautioned  to  take  them  passively,  and  not  consciously  to 
change  his  type  of  breathing  while  they  are  under  his  nostrils. 
Sound  stimuli  —  chords  and  discords  on  forks  or  piano,  musical 
phrases,  harsh  noises  —  are  still  cleaner,  but  less  strongly 
affective. 

However,  the  stimuli  must  be  chosen  to  suit  the  subject ; 
and  any  stimulus  should  be  unhesitatingly  taken  which  promises 
to  bring  out  a  well-marked  reaction.  It  may  be  necessary  to 
provide  a  second  Ey  to  give  the  affective  stimulus,  while  the 
original  E  attends  to  the  drum. 

The  kymograph  is  one  of  the  corner-stones  of  laboratory 
equipment.     We  may  therefore  describe  its  use  in  some  detail. 

The  Kymograph  and  Its  Use.  —  The  recording  apparatus 
and  accessories,  required  for  this  and  similar  experiments, 
are  as  follows. 

(i)  Clockwork  kymograph,  with  two  drums. 

(2)  Supply  of  kymograph  paper. 

(3)  Stand  to  take  revolving  drum  during  smoking. 

(4)  Lamp  for  smoking. 

(5)  Stand  to  take  spare  drum. 

(6)  Sharp  scalpel. 

(7)  Varnish,  varnishing  tray,  hangers. 

(8)  Marey  tambour  and  writing  point. 

(9)  Tubing  and  air-cock. 

(10)  Time-marker. 

(11)  Standards,  with  right-angle  clamps  and  spare  arms. 

(i)  The  kymograph  (Gk.  fcvfjLa,  wave,  and  'ypd(f)€Lv,  to  write)  is 
so  called  because  it  was  first  employed  for  the  recording  of 
curves  of  blood  pressure.  It  is,  however,  well  adapted  to  record 
any  process  whose  course  is  a  function  of  time  elapsed.  It  con- 
sists, in  essentials,  of  a  hollow  brass  cylinder,  the  drum,  which 
is  rotated  at  a  constant  rate  by  means  of  a  clockwork  (water 
motor,  weight,  electric  motor,  etc.).  The  rate  of  rotation  may 
be  varied,  within  fairly  wide  limits,  by  change  of  governor,  or 
some  similar  device. 


{  42,   Tk€  PUtkytmogn^h 


\7l 


As  the  drum  revolves,  it  presents  a  continuous  writing-sur- 
foce,  —  precisely  the  same  surface,  of  course,  that  would  be 
afforded  if  the  cylin- 
der were  slit  down  its 
length  and  spread  out 
flat ;  but  in  more  com- 
pendious form,  and 
under  better  control. 

(2)  Instrument-mak- 
ers supply  kymograph 
paper  with  their  ky- 
mographs. It  is  a 
fairly  tough,  glazed 
paper,  cut  in  strips 
whose  width  is  the 
height  of  the  drum 
and  whose  length  is 
about  5  mm.  more 
than  the  circumfer- 
ence. The  overlap- 
ping edge  is  gummed 
on  its  unglazed  side. 

The  cylinder  is  laid 
in  the  smoking  stand, 

no.  (3)  The  gummed  edge  of  a  strip  of  paper  is  moistened, 
and  the  paper  passed  under  the  drum,  glazed  side  outwards ; 
the  edges  are  brought  together  above  and  the  gummed  edge 
pressed  down  smoothly  and  snugly  over  the  other.  The  paper 
should  fit  the  drum  squarely,  and  should  show  no  crease  or 
other  unevenness. 

(3)  The  smoking  standi  in  its  simplest  form,  consists  of  two 
upright  strips  of  wood  on  a  wooden  base.  The  strips  are  cut 
out,  in  U-shape,  at  the  top,  so  that  the  axis  of  the  drum  may  rest 
upon  them :  their  distance  apart  must  be  regelated  by  the 
length  of  this  axis.  The  papered  drum  is  laid  on  the  stand, 
and  its  axis  revolved  by  the  fingers  of  the  left  hand. 

(4)  The  right  hand  holds  the  smoking  lamp,  a  small  petroleum- 
burning  lamp  with  broad  wick.      As  the  drum  is  turned,  the 


Fig.  39.  —  The  Lndwig-Baltzar  kymognph.  Zim* 
mennann,  PeUold,  etc. ;  with  accettoriet,  Mk.  900. 
See  Langendorfi,  Physiol.  Graphik,  1891,  19. 


174 


The  Affective  Qualities 


lamp-flame  is  held  close  up  under  it,  and  the  lamp  moved  fairly 
quickly  from  right  to  left  and  back  again,  so  that  the  smoke 
traces  broad  spirals  of  soot  upon  the  white  paper.  The  rate  of 
turning  must  be  learned  by  practice.  The  paper  should  be 
evenly,  but  not  too  thickly,  coated  with  the  brownish-black  soot. 
It  is,  upon  the  whole,  better  to  work  with  a  mere  grey  film  of 
soot  than  to  have  the  drum-surface  overloaded  ;  though  the 
right  amount  of  smoking  varies  greatly  with  the  nature  of  the 
writing-point. 


Fig.  30.  —  Universal  smoking  stand.     Zimmennann,  Mk.  50. 

The  smell  of  a  freshly  smoked  drum  is  very  intensive,  and 
for  some  (9's  very  disagreeable.  For  this  reason,  if  for  no  other, 
the  smoking  should  never  be  done  in  the  experimenting  room. 
For  the  same  reason,  the  drum  should  be  allowed  to  cool,  before 
it  is  put  on  the  instrument.  Here  is  one  of  the  advantages  of 
the  spare  drum  :  the  two  drums  can  be  smoked  together,  and  the 
empty  one  put  in  place  as  soon  as  ever  the  first  is  filled,  without 

long  interruption  of  the  experi- 
ment, and  without  the  prospect 
of  exposing  O  to  an  unpleasant 
smell  stimulus. 

(5)  The  stand  for  the  spare 
drum  may,  again,  be  very  .sim- 
ple :  just  two  uprights,  cut  into 
U-shape  above,  to  hold  the  sec- 
ond drum  while  it  is  waiting  for 
use,  or  the  first  drum  after  it 
has  been  filled.  A  small  deal 
packing-box  makes  a  very  good  stand  of  this  kind.  The  smok- 
ing stand  might  be  used;  but  it  is  much  more  convenient  to 
have  a  stand  in  each  room. 


Fig.  31.  —  Stand  for  spare  drum  (Ludwig- 
Baltzar  Kymograph). 


{  42.    The  KywMimpk  175 

(6)  To  remove  the  smoked  paper  from  a  drum,  proceed  as 
follows.  Take  the  axis  of  the  drum  in  your  left  hand,  resting 
your  thumb  upon  the  edge  of  the  drum  and  therefore  upon  the 
edge  of  the  paper.  Let  the  place  of  contact  be  the  seam  of  the 
paper.  Draw  the  scalpel  sharply  up,  along  the  scam,  cutting 
outwards  so  as  not  to  injure  the  drum.  When  the  cut  is  made, 
raise  your  thumb  partially,  so  that  the  side  of  the  paper  that  is 
farther  from  you  slips  down  from  the  drum.  While  this  is  hap. 
pening,  secure  the  other  end  of  the  hither  edge  by  a  clip,  or  by 
the  fingers  and  thumb  of  your  right  hand.  Lay  the  drum  on 
the  stand,  and  remove  the  paper  entirely.  Lay  it  out  flat 
on  a  table. 

Some  students  prefer  to  remove  the  paper  while  the  drum  is  on  the  stand. 
Two  couTMS  are  then  open,  (i)  Turn  the  drum  seam  upwards.  Pass  the 
fingers  of  your  left  hand  into  the  drum,  and  hold  the  paper  at  the  seam  with 
the  thumb.  Cut  the  seam.  Pick  up  the  hither  edge  of  the  paper  with  a  clip, 
and  draw  the  paper  all  sharply  upwards,  while  the  left  hand  gives  the  dmm  a 
quick  turn  out.  (2)  Place  the  drum  as  before.  Cut  the  seam,  but  leave  a 
narrow  strip  uncut  at  the  right-hand  end.  Turn  the  drum  down,  through  some 
170*,  and  take  the  nearer  edge  of  the  paper  in  a  dip.  Pull  sharply  on  the  clip, 
towards  yourself,  at  the  same  time  that  your  left  hand  gives  the  drum  a  quick 
turn  in      The  Strip  tears  away  evenly,  and  the  paper  comes  in  over  the  drum. 

(7)  ^Vlter  the  record  has  been  numbered,  dated,  etc.,  it  must 
be  varnished  for  permanent  keeping.  The  varnishing  outfit 
consists  of  (a)  a  flat  tray  or  shallow  dish  (a  baking  dish  of  agate 
ware  makes  a  good  tray),  at  one  end  of  which  a  hole  is  punched. 
A  cork  is  fitted  into  the  hole,  and  a  short  piece  of  glass  tubing 
passed  through  the  cork.  The  glass  tube  is  connected  (b)  by  a 
long  rubber  tube  to  the  varnish  bottle.  This  is  a  large  and  wide- 
mouthed  bottle,  corked  or  stoppered,  containing  (c)  the  varnish 
which  is  to  be  floated  over  the  record.  The  varnish  may  be 
made  up  on  various  recipes :  the  most  satisfactory  is,  perhaps,  a 
solution  of  10  parts  of  white  shellac  in  100  parts  of  90  Jib  alcohol. 
The  mode  of  varnishing  is  as  follows.  The  bottle  is  raised  to  a 
shelf  above  the  varnishing  tray.  The  bottom  of  the  tray  is  thus 
flooded  with  varnish.  The  record  is  taken  up  from  the  table  by 
two  clips  or  forceps,  one  in  each  hand,  and  drawn  slowly  and 
evenly  through  the  solution,  face  upwards.     All  parts  of  the 


176 


The  Affective  Qualities 


smoked  surface  must  be  covered  by  the  varnish.  One  of  the 
clips  is  then  released,  and  the  record  drawn  out  and  hung  up  to 
drain. 

The  ordinary  hanging  clips  sold  by  picture  dealers,  having  a 
spring  clip  below  and  a  curved  hook  above,  make  (df)  useful  clips 
for  holding  and  suspending  the  records.     Behind  the  varnishing 

tray  stands  an  upright 
wooden  frame,  carry- 
ing (r)  projecting  arms 
or  hangers.  The  hooks 
are  slipped  over  these 
arms,  and  the  records 
drip  into  the  tray  be- 
low. When  the  record 
has  been  hung  up,  the 
bottle  is  lowered  to  a 
shelf  below  the  tray, 
and  the  varnish  runs 
back.  The  cork  or 
stopper  must  be  re- 
moved while  the  bottle 
is  emptying  and  fill- 
ing, but  should  be  care- 
fully replaced  when  the 
work  is  concluded. 

As  soon  as  the  rec- 
ord is  dry,  it  should  be 
trimmed,  and  either  pasted  in  the  note-book,  with  its  accompany- 
ing introspective  record,  or  else  laid  without  folding  in  a  port- 
folio. In  the  latter  case  it  must  be  conspicuously  numbered, 
and  a  corresponding  number  placed  over  the  note-book  intro- 
spection. Curves  easily  '  get  mixed ' ;  and  nothing  is  more 
aggravating  than  to  possess  a  good  record  which  cannot  be 
certainly  identified. 

(8)  The  Marey  tambour  is,  in  principle,  a  small  metal  funnel, 
the  mouth  of  which  is  closed  by  a  piece  of  tightly  stretched  india- 
rubber  sheeting.  A  small  and  light  disc  of  metal,  cemented 
to  the  rubber,  carries  the  writing-point.     The  small  end  of  the 


Fig.  32.  —  Varnishing  tray  and  drying  rack.     $<,. 


{  43.    Tk4  Kymogrt^  177 

funnel  is  connected  by  rubber  tubing  to  the  plethysmograph, 
pneuroogpraph,  etc.  The  writing-lever  is  so  hung  that  an 
increased  pressure  of  air  in  the  rubber  tube  means  a  rise  of  the 
writing-point,  while  a  drop  in  air-prcssure  means  a  fall  of  the 
point.  The  point  thus  rises  and  falls  with  expansion  and  con- 
traction of  the  arm,  inhalation  and  expiration,  etc.    The  writing- 


^^^I^S 


^  y^  —  Marey  Umbour,  writing-lever  and  air-cock.      See  Langendorfi,  60;  and 
cf.  A.  Binet,  L'Ann6e  psych.,  ii.,  1896,  776. 

paint  consists  of  a  curved  point  of  parchment,  steel  spring, 
aluminium,  etc.,  attached  to  a  light  lever.  This  may  be  of 
bamboo,  straw,  reed,  etc. 

Fine  rubber  sheeting,  and  rubber  cement,  must  be  kept  on 
hand :  the  drum-head  of  a  tambour  is  always  liable  to  chafe  or 
crack. 

(9)  A  serviceable  rubber  tubing  for  air  transmission  is  the 
sort  described  as  'heavy  black  seamless,  of  pure  unvulcanised 
g^m  '  in  the  catalogues  of  chemical  supplies.  The  tubing  should 
be  thick-walled,  and  of  as  wide  a  lumen  as  accords  with  tight 
fitting  over  the  metal  tubules.  The  exact  length  of  the  pieces 
employed  is  immaterial,  though  there  are  obvious  reasons  for 
keeping  them  as  short  as  possible.  If  the  laboratory  has  only  a 
small  supply,  and  this  is  much  in  demand,  it  will  be  well  to  cut 
two-thirds  of  the  stock  into  50  cm.  pieces,  and  the  remaining 
third  into  metre  pieces.  Before  beginning  an  experiment,  see 
that  there  are  no  kinks  in  the  system,  and  no  doublings-under  at 
the  junction  of  metal  and  rubber ;  use  ligatures  of  thread,  or 
ease  the  junction  by  vaseline,  where  necessary. 

One  of  the  problems  of  the  laboratory  is  to  keep  rubber 
tubing,  and  rubber  materials  generally,  from  stiffening  and 
cracking.  There  seems  to  be  no  panacea ;  but  the  following 
rules  are  worth  observing. 


1/8 


The  Affective  Qualities 


a.  Buy  rubber  of  good  quality  and  of  high  flexibility. 

b.  Keep  it,  when  out  of  use,  in  hermetically  sealed  jars  (museum  jars,  or 
self-sealing  preserve  jars),  or  in  tightly  closing  drawers. 

c.  Keep  it  in  the  dark :  swathe  the  jars  in  black  wrappings,  or  put  them 
into  dark  closets. 

d.  Keep  it  plentifully  sprinkled  with  powdered  soapstone.  Shake  this 
off  before  using. 

e.  Do  not  be  tempted  to  use  'experimental '  rubber  tubing  for  other  labora- 
tory purposes  {e.g.^  gas  conduction)  :  keep  it  strictly  for  its  proper  purpose. 

y.   As  far  as  possible,  avoid  extremes  of  temperature. 

For  gas  and  water  conduction,  the  varnish  bottle,  etc.,  rubber 
tubing  of  the  sort  described  as  *  white  vulcanised '  will  answer 
every  purpose. 

T\i^  air-cock  consists,  first  of  all,  of  a  piece  of  metal  tubing,  some 
8  cm.  in  length,  bevelled  off  at  each  end  for  easy  insertion  into 
the  rubber  tubing.  The  wall  of  the  tube  is  pierced,  near  one 
end,  by  a  pin-hole.  Over  the  pin-hole  lies  the  head  of  a  small 
hammer-shaped  lever,  pivoted  to  the  outside  of  the  tube,  its  long 
axis  parallel  with  that  of  the  tube  itself.  The  hammer-head  is 
swathed  in  very  fine  rubber  sheeting,  and  a  delicate  but  strong 
india-rubber  band,  passed  over  hammer-shank  and  tube,  holds 
the  head  tightly  down  in  place.  The  efficiency  of  this  band 
must  be  carefully  tested  before  every  experiment. 

When  the  air-cock  is  left  undisturbed,  therefore,  there  is  no 
break  in  the  tube-system.  When  the  extremity  of  the  hammer- 
shank  is  depressed, 
the  pin-hole  opens 
communication  be- 
tween the  air  within 
the  system  and  the 
air  of  the  room, 
and  normal  press- 
ure within  the  sys- 
tem is  secured. 

(lo)  The  time- 
marker  furnishes 
the  abscissae  of  the  curve  of  volume,  breathing,  etc.  The  time 
line  may  be  obtained  in  various  ways  :  from  metronome,  tuning- 
fork,  interrupter-clock,  etc.     The  simplest  and  most  direct  time- 


FlG.  34. — Time-marker  (Jacquet's  recording  chronometer; 
marks  seconds  and  fifths  of  seconds).  Verdin,  Fr.  170. 
For  other  instruments,  see  Langendorff,  Physiol.  Graphik, 
1891,  121  flf. 


{  42.    Thi  Kjmogr^k  179 

marker,  for  such  experiments  as  are  here  in  question,  is  the 
Jacquet  chronometer.  This  is  a  watch,  housed  in  a  square  case, 
supplied  with  a  light  metal  lever,  whose  point  jerks  up  once  in 
every  second  or  once  in  every  fifth  of  a  second,  as  required. 
The  curved  point  of  the  lever  can  be  adjusted  to  write  upon  the 
drum  immediately  below  the  writing-point  of  the  tambour. 

(11)  For  kymographic  work,  a  good  set  of  standards^  tripod 
bases,  arms  and  right-angle  clamps  is  essential.  •  In  the  plethys- 
mographic  experiment  we  need :  {a)  a  standard  with  clamp  and 
arm,  over  which  the  rubber  tubing  that  leads  from  jar  to  tambour 
may  rest ;  (Jb)  a  standard  with  clamp,  to  take  the  tambour  itself; 
and  (r)  a  standard  with  clamp  and  arm  to  take  the  time-marker. 
Tambour  and  marker  may  be  put  upon  a  single  standard,  but 
adjustment  is  easier  if  the  two  are  kept  separate. 

(12)  Adjustments. — Care  must  be  taken,  in  laying  the  paper 
over  the  drum,  or  in  setting  the  drum  upon  the  instrument,  that 
the  direction  of  writing  be  from  the  double  thickness  of  paper 
to  the  seam,  and  not  vice  versa.  If  this  rule  is  not  followed,  the 
writing-point  will  hitch  over  the  seam,  when  the  drum  comes 
round  to  it :  the  point  may  be  deranged,  or  a  critical  portion  of 
the  curve  spoiled.  The  rule  is,  of  course,  unimportant  for  our 
particular  experiments,  which  do  not  extend  beyond  a  single 
revolution ;  but  it  is  exceedingly  important  when  the  tracing 
extends  over  several  revolutions,  and  is  a  cardinal  rule,  which 
cannot  be  learned  too  early,  of  kymographic  work  at  large. 

It  is  hardly  necessary  to  say  that  the  writing-points  go  *  with 
the  current,*  i.e.,  that  the  drum  moves  off  from  under  them,  and 
not  in  towards  them.  In  the  latter  case,  any  the  least  irregu- 
larity in  the  grain  of  the  paper,  or  what  not,  would  bend  up  the 
flexible  point,  spoil  the  curve,  and  perhaps  break  the  lever. 

When  the  drum  is  set  up,  swing  it  round  so  that  the  two 
writing-points  may  begin  their  records  as  near  the  seam  as 
possible.  Since  we  are  to  cut  the  paper  at  the  seam,  we  shall 
in  this  way  secure  the  full  extent  of  the  surface  for  our  curve. 
—  This  rule,  again,  does  not  hold  for  experiments  which  are  to 
continue  beyond  a  single  revolution.  The  seam-line  may  here 
coincide  with  a  critical  point  upon  the  curve. 

If  the  drum  is  well  turned,  the  paper  smooth,  and  the  soot 


l8o  The  Affective  Qualities 

coating  even  and  not  too  thick,  the  friction   between  writing. 

point  and   writing-surface  is  reduced  to  a  constant  minimum. 

Great  care  must  be  taken  that  the  writing-point  touch  the  sur- 

^^  face  only  at  one  point,  and  that 

,^^^     g  the  lever  move  in  a  plane  parallel 

,^ ™^-C^ .         to  the  plane  of  a  tangent  drawn 

f  \  through  the  point  of  contact. 

(l  jk     •  1 1  The     above     is     the     merest 

V  J  sketch    of    apparatus    and    pro- 

\^^_^^  cedure.      There    are    numerous 

Fig.  35.  — Illustrates  the  adjustment  of    types  of  the  former,  and  many 

the  writing-point  to  the  drum  surface,    variants  of  the  latter.     The  dif- 

k.  kymograph;    a,  rightly  adjusted,      r  .    •       .  .  1  ^  e 

K  wrongly  adjusted  writing-point;  ^^rent  mstrumcnts  and  modes  of 
/,  tangential  plane  through  the  point  transmission,  as  well  as  the  errors 
of  contact.  6/ Langendorff,  Physiol,    involved    in    tangential    writing, 

are  set  forth  by  O.  Langendorff, 
Physiologische  Graphik,  1891.  This  book  should  be  kept  for  ref- 
erence in  the  laboratory  library.  —  The  above  directions  are  not 
to  be  followed  blindly ;  they  may  be  modified  in  many  points  to 
suit  the  equipment  and  arrangement  of  the  individual  laboratory. 
Preliminaries.  —  Both  O  and  E  should  understand  the  plan 
of  the  apparatus.  Thus  :  the  rigid  metal  cap  is  to  prevent  bulg- 
ing of  the  rubber  cap  as  the  hand  increases  in  volume.  Any 
such  *give*  at  the  jar-end  of  the  system  would  naturally  nullify 
the  experiment.  The  expansion  in  the  glass  tube  greatly  reduces 
the  change  of  water  level  as  the  hand  swells  and  contracts ;  in- 
jurious pressure  effects  are  thus  avoided,  while  the  changes  are 
still  sufficient  to  evoke  prompt  and  well-marked  response  from 
the  writing  lever.  The  air-cock  saves  strain  upon  the  tambour 
when  the  plethysmograph  is  being  connected  to  it,  and  also 
guarantees  a  constant  air  pressure  within  the  rubber  tubes. 
The  bent  flexible  tip  of  the  writing-lever  ensures  the  recording 
of  the  whole  curve  :  without  it  the  point  would  fly  off  the  drum- 
surface  at  a  certain  height  above  the  abscissa.  —  Questions  of 
this  sort  must  be  asked  and  answered,  until  the  whole  scheme 
is  clear. 

Some  (9's  prefer  to  have  the  jar  slightly  tilted,  not  vertical. 
The  instrument  may  then  be  steadied  by  folded  cloths  or  towels. 


$  42.    Tki  PUtkysmogn^h 


[8i 


If  O  has  to  move  from  his  seat  during  the  ? 

experiment,  a  roller  towel  can  be  thrown  round  |  g.4 

his  neck,  and  the  jar  held  in  it  as  in  a  sling.  \  <  | 

The  rubber  sleeve  will  almost  certainly  tear  pl-o  ^ 

away  from  the  cap,  at  some  point  or  other,  ^  1^  | 

before  many  experiments  have   been   taken.  ^z\ 

Hence  E  should  be  provided  with  a  tube  of  i  ^  a* 

quick-setting  rubber  cement.  \     \ 

Experiment.  —  No  rule  can  be  laid  down  ^  c  J 

as  regards  a  signal  \o  O.      In  some  cases,  a  |  §  3 

signal  before  the  clock  starts  is  welcome,  as  '*  g  f 

helping  towards  general   steadiness  and  pas-  n^  ?-  •• 

sivity ;  in  others,  it  is  disturbing  and  flutter-  **  *•  J 

ing.     The  whirring  of  the  clockwork  is  itself  W\ 

a  signal  that  the  experiment  has  begun.    Some  Z\^ 

(X%  are  unmoved  by  it ;  others  are  thrown,  for  i^  i.  h 

the  first  few  trials,  into  a  state  of  dismay,  —  §  ^  S 

the  die  is  cast,  and  if  they  do  not  sit  still  now  §  S  2* 

and  think  of  nothing,  all   the  work  is  lost !  x  g-  ? 

E  must  adapt  his  procedure  to  his  subject :  "^  3  i. 
what  he  has  to  do  is  to  convince  O,  some-  §  2» 
how,  that  the  experiment  cannot  go  wrong  if  *  g* 
it  is  left  to  run  its  own  course.  ^.| 

It  is  probably  true  of  all  subjects,  even  the  •«  |- 
most  conscientious  and  experienced,  that  th^y  8  3 
feel  a  certain  timidity  and  reserve  when  called  S  o 
upon  to  give  an  introspective  account  of  the  ex-  g*  | 
periment.  The  kymograph  curve  seems  to  be  Si 
so  remote  and  out  of  reach  that  one  despairs  f  s* 
of  ever  matching  its  impassive  facts  by  one's  Z.\ 
scrappy  and  hesitating  sentences.  Hence  the  5.  ? 
exactness  of  this  match  —  the  precise  parallel,  "J 
breath  for  breath,  of  objective  and  subjective  ^g* 
repose  and  of  objective  and  subjective  disturb-  '5' I 
ance  —  comes  as  an  almost  startling  revelation.  When  once 
O  has  realised  that  the  curve  obeys  his  interpretation,  —  that 

it  honestly  reflects  the  turn  of  his  head  in  his  collar,  the  slight 
-shift  of  his  body  in  the  chair,  the  unpleasant  memory  that  forced 


l82 


The  Affective  Qualities 


itself  upon  him,  his  pleased  interest  in  the  after-image  of  the 
window  ;  while,  on  the  other  hand,  it  betrays  everything  that  he 
has  been  tempted,  half-consciously,  to  conceal,  —  the  play  of 
attention  upon  the  course  of  breathing,  his  half-voluntary  wish 
that  the  curve  may  be  a  good  one,  and  his  half-intention  to  try 
to  make  it  good ;  he  settles  down  resignedly  into  the  required 
passive  attitude,  and  lets  the  experiment  go  on  as  a  matter  of 
course.  Some  (^'s  see  the  trlith  at  once,  others  require  a  little 
time  :  and  E  must  shape  his  conduct  accordingly. 

». . .  ■ ». ■  1 1 . 1 ,  ■ ■  ■  .f 

Fig,  37.  —  A  typical  curve  of  unpleasantness.     The  crosses  indicate  the  times  of 
application  and  removal  of  stimulus.     Time  unit,  i  sec. ;  record  X  \. 


It  is  said  in  the  text  (p.  106)  that  after  O  and  E  have  changed 
places  for  the  second  time  O  is  not  to  be  told  which  of  the  two 
possible  experiments  will  be  taken  first.  It  is  evident  that  the 
affective  experiment  must  be  taken  first,  or  O  will  be  looking 
forward  to  it  with  certainty  after  the  recording  of  the  second 
normal.  In  all  probability,  however,  this  reflection  will  not 
occur  to  O  at  the  time ;  he  will  regard  the  alternative  of  the 

text  as  a  real  alterna- 
tive. If  he  does  not, 
he  must  be  told  that 
any  one  of  the  three 
possible  experiments 
—  another  normal, 
'another  unpleasant, 
or  a  pleasant  —  may 
be  taken. 

Questions.  —  (i) 
Yes.  If  a  pleasant 
stimulus  be  given,  the 
curve    drops     during 

Fig.  38. —  Mosso's  sphygmomanometer.      For  a  de-     the     application,     but 
scription,  see  Binet  and  Henri,  La  fatigue   intel-     .,  .  .  . 

lectuelle,   1898,   103;    A.  Binet  and  N.  Vaschide,     ^^^^  ^^^^^  ^^  once  10 

L'Annee  psych.,  iii.,  1897,  "9»  ^    higher    level    and 


§  4^    Thi  PUthysmograpk 


183 


maintains  this  level  for  some  time.     If  the  stimulus  be  unpleas- 
ant, the  curve  drops  during  application,  and  then  drops  still 


o 


<A 


Fla  59.  —  The  6nger  plethysmograph  of  Lombard  and  PilUbury. 
Cf.  Langendorff,  68. 

farther,  coming  back  slowly  to  its  normal  height.  —  Cf.  the 
curves  of  Exp.  XXIII.,  supra. 


Fta.  4a— Von  Frey'i  iphygmogrtph. 


1 84 


The  Affective  Qualities 


(2)  The  expansion  during  pleasure  may  be  compared  to  the 
involuntary  reaching-out  of    Exp.  XXII.,  and   the  contraction 
during  unpleasantness  to  the  shrinking- 
back  of  the  same  Exp. 

(3)  In  all  probability  there  will  be 
irregularities  in  the  curve  due  to  such 
objective  and  subjective  conditions  as 
were  enumerated  just  now  (pp.  181  ff.). 
In  all  cases,  the  curve  tells  an  absolutely 
truthful  story.  O  may,  indeed,  actually 
be  reminded  by  it  of  some  interruption 
which  he  had  honestly  overlooked  or 
forgotten. 

(4)  Experiments  should  be  tried  upon 
the  pulse-line,  for  itself,  and  the  respi- 
The  volume  curves  cannot  fail  to  suggest 

that  these  lines  would  vary  with  variation  of  the  affective  con- 
sciousness. 

Instruments.  —  Fig.  38  shows  A.  Mosso's  sphygmomano- 
meter (Verdin,  Fr.  190).  See  F.  Kiesow,  Philos.  Studien,  xi., 
1895,  41.  Fig.  39  shows  the  finger  plethysmograph  of  W.  P. 
Lombard  and  W.  B.  Pillsbury,  with  connections  (Amer.  Journ. 
of  Physiol.,  iii.,  1899,  186).  The  finger  tube  is  screwed  to  a 
swinging  arm-board.  Warm  water,  the  temperature  of  which  is 
regulated  by  a  thermometer,  courses  through  the  mantle  of  the 


Fia  41.— The  Verdin 
pneumograph. 

ration-line,  for  itself. 


Fig.  42. — The  Sumner  pneumograph. 


tube.  The  finger  tube  is  connected,  first  to  a  3-way  cock,  open 
to  the  air ;  and  thence  to  a  T-piece,  from  the  one  limb  of  which 
a  rubber  tube  runs  to  the  adjusting  piston-syringe,  while  from 


$  43.    The  PUthysmograph  185 

he  other  a  similar  tube  passes  to  the  piston-recorder  and  writing 
devices.  —  Michigan  Apparatus  Co.,  $16. 

Fig.  40  is  the  sphyginograph  of  M.  von  Frey  (Zimmermann, 
Mk.  200).  The  instrument  can  also  be  arranged  for  air  trans- 
mission. Fig.  41  is  the  Verdin  pneumograph  (Fr.  50),  and  Fig. 
42  the  Sumner  pneumograph  ($2.50). 

Literature.  —  On  the  use  of  the  plethysmograph,  see  Binet 
and  Henri,  La  fatigue  intellectuelle,  1898,  61  ff.  (the  authors 
figure  the  instruments  of  Fick,  Mosso,  Franck,  and  Hallion  and 
Comte);  and  Langendorff,  Physiol.  Graphik,  1891,  235  ff.  For 
the  sphygmograph,  see  Langendorff,  222  ff. ;  M.  von  Frey,  Die 
Untersuchung  des  Pulses  und  ihre  Ergebnisse  in  gesunden  und 
kranken  Zustanden :  Berlin,  1892.  For  the  pneumograph,  see 
Langendorff,  252  ;  Binet  and  Henri,  147  ff. 

The  literature  on  this  and  the  preceding  Experiment  has  been 
brought  together  by  J.  R.  Angell  and  H.  B.  Thompson,  Psych. 
Rev.,  vi.,  1899,  32  (Univ.  of  Chicago  Contrib.  to  Philos.,  ii.,  2, 
32).  To  these  references  add  Wundt,  Philos.  Studien,  xv.,  1899, 
149 ;  Volkerpsych.,  i.,  i,  1900,  40  ff. ;  W.  P.  Lombard  and  W.  B. 
Pillsbury,  Amer.  Joum.  of  Physiol.,  iii.,  1899,  186,  201  ;  A.  Leh- 
mann,  Die  korperlichen  Aeusserungen  psychischer  Zustande,  i. 
Plethysmographische  Untersuchungen.     Leipzig,  1899. 


CHAPTER   VIII 

Attention  and  Action 

experiment  xxv 

§  43.  Attention.  —  The  problem  of  attention  is  essentially  a 
modern  problem.  This  does  not  mean  that  the  facts  of  attention 
were  unobserved,  and  theories  of  attention  lacking,  until  modern 
times :  Braunschweiger  asserts  (Die  Lehre  von  der  Aufmerksam- 
keit  in  der  Psychologic  des  18.  Jahrhunderts,  Leipzig,  1899) 
that  '*  it  would  be  hard  to  find  a  single  idea  or  thought  that  can 
contribute  in  any  sort  of  way  to  the  solution  of  this  important 
problem,  which  does  not  appear  at  least  in  mice  during  the 
eighteenth  century."  It  means  simply  that,  at  the  turning-point 
of  modern  psychology,  —  i.e.,  with  Herbart,  —  the  problem  of 
attention  received  explicit  formulation,  as  a  problem  which  every 
system  of  psychology  has  to  face  ;  and  that  modern  psychologists 
since  Herbart  have  set  it  in  the  forefront  of  their  investigations, 
as  the  older  psychologists  did  not. 

**  The  description  and  explanation  of  the  facts  comprised  under 
the  familiar  term  *  attention '  constitute  one  of  the  most  formi- 
dable difficulties  which  the  psychologist  encounters  in  the  whole 
course  of  his  enquiry"  (Kiilpe).  It  is,  then,  not  surprising 
that  the  treatment  of  attention  differs  very  considerably  in  the 
different  systems  of  psychology.  At  the  same  time,  we  must  not 
exaggerate  this  divergence  of  opinion.  It  has  become  fashionable 
to  quote  the  phrase  "  quot  homines  tot  sententiae  "  in  regard  to 
theories  of  attention.  But  the  same  thing  might  be  said  of  a 
great  many  scientific  questions,  both  outside  and  inside  of 
psychology,  and  its  truth  is  not  incompatible  with  the  final 
accomplishment  of  a  good  deal  of  solid  work.  There  are  serious 
differences  of  opinion  concerning  the  nature  of  the  attentive 
consciousness :  but  much  of  the  disagreement  is  due  to  one- 

186 


§  43-    TJUarUs  of  Attention  187 

sidedness,  and  not  to  radical  opposition  of  standpoint.  Some 
theories  are  descriptive,  to  the  neglect  of  explanation ;  some 
emphasise  facilitation,  some  inhibition ;  some  lay  stress  on  the 
motor  phenomena,  some  on  the  affective ;  and  so  forth.  These 
views  need  not  be  mutually  exclusive. 

The  Instructor  should,  of  course,  be  fiunQiar  with  the  general  discussions 
in  Hofler  (Psych.,  §  42),  James  (Principles,  esp.  i.,  ch.  xi.),  KUlpe  (Outlines, 
S§  72-76)»  LipP*  (Grundtats.,  chs.  iv.,  vii.),  Stumpf  (Tonps.,  esp.  i.,  §  4,  i ; 
li.,  $  22,  I),  Volkmann  (Psych.,  ii.,  §  ii4),Wundt  (Phys.  Psych.,  esp.  ii.,  ch. 
XV.,  2).  Of  the  monographic  literature  the  following  will,  perhaps,  be  found 
the  most  useful  works :  G.  £.  MUller,  Zur  Theorie  der  sinnlichen  Aufmerksam- 
keit,  Leipxig,  1873;  1*-  Ribot,  La  psychologie  de  Tattention,  Pari.s.  1889; 
L.  L.  Uhl,  Attention:  a  Historical  Summary  of  the  Discussions  concerning 
the  Subject,  Baltimore,  1890 ;  A.  Pilzecker,  Die  Lehre  von  der  sinnlichen  Auf- 
merksamkeit,  Miinchen,  1889  (gives  MUller's  later  views);  H.  E.  Kohn,  Zur 
Theorie  der  Aufmerksamkeit,  Halle,  1894  (gives  Benno  Erdmann's  views: 
to  be  read  with  KUlpe's  criticism,  Zeits.  f.  Phil.  u.  phil.  Kritik,  ex.,  1896,  26) ; 
A.  J.  Hamlin,  Attention  and  Distraction,  Amer.  Jour,  of  Psych.,  viii.,  1896,  3 
(gives  a  classification  and  abstract  of  theories). 

Two  principal  classifications  of  attention  cross  and  recross  in  the  literature. 
The  one  di\*ides  attention  into  'sensible'  and  *  intellectual,*  the  other  into 
'vc^untary'  or  *  active'  and  *  involuntarj' '  or  *  passive.'  The  former  is  a  sub- 
division in  terms  of  the  contents  or  objects  given  in  the  attentive  state ;  the 
latter  a  subdivision  in  terms  of  the  conditions  of  attention,  passive  attention 
being  an  attention  that  is  determined  unequivocally,  by  a  single  stimulus  or 
incentive,  and  active  attention  an  attention  determined  equivocally,  by  a  plu- 
rality of  stimuli  or  incentives.  Neither  distinguishes  specific  kinds  or  distinct 
modes  of  attention  itself. 

On  the  question  oi  grades  or  degrees  of  consciousness,  see,  besides  the  text- 
books dted,  J.  Ward,  art.  Psycholog>',  Encyc.  Britannica,  9th  ed.,  xx.,  47 ; 
KUlpe,  <^.  r^r.,  32;  Helmholtz,  Sensations  of  Tone,  62.  Lipps'  discussion, 
GrundUtsachen  d.  Seelenlebens,  1883,  29  fT.,  is  especially  noteworthy  on  the 
negative  side. 

For  an  elementary  statement  of  the  view  of  attention  adopted  in  the  text, 
see  the  author's  Outline  of  Psych.,  1899,  134  ff- 

Question  (i)  This  and  the  following  Question  need  not  be 
exhaustively  answered. 

The  psychology  of  the  eighteenth  century  is  often  spoken  of 
as  the  *  faculty  psychology,*  for  the  reason  that  it  attempted  to 
explain  all  the  various  phenomena  of  mind  by  the  assumption  of 
different  mental  faculties.  It  postulated  one  or  more  fundamental 
forces  of  mind,  and  then  proceeded  to  deduce  therefrom  a  number 


1 88  Attention  and  Action 

of  special  powers  or  forces.  C.  Wolff  ( 1 679-1 754)  posited  a  single 
original  faculty,  the  vis  reprcBsentativa  ;  C.  Bonnet  (i  720-1 793) 
—  a  man  who  did  good  work  upon  the  problem  of  attention  — 
posited  two  ultimate  powers,  those  of  sense-perception  and 
reflection;  J.  N.  Tetens  (1736-1805)  believed  in  three  separate 
faculties,  ideation,  feeling  and  desire,  though  he  refers  them  all 
to  a  single  Sccienkraft. 

We  may  say  in  criticism :  (i)  that  the  faculty  names  are  merely 
classificatory  concepts  ;  and  that  the  subsumption  under  them  of 
the  ideas,  feelings,  impulses,  etc.,  which  are  really  given  in  intro- 
spection, does  not  help  us  in  the  least  degree  towards  an  under- 
standing of  these  processes.  A  faculty  psychology  must,  that  is 
to  say,  be  at  best  a  merely  descriptive  psychology,  and  can  never 
rise  to  the  level  of  explanation.  (2)  But,  further,  the  faculties, 
which  as  class-names  are  products  of  scientific  abstraction,  be- 
come changed  in  the  faculty-systems  into  actual  forces  or  powers, 
which  are  supposed  to  give  rise  to  the  separate  ideas,  feelings, 
etc.  In  other  words,  the  faculty  which,  rightly  defined,  is  in- 
capable of  affording  explanation,  is  substantialised,  and  so  made 
the  ground  of  a  wrong  explanation.  The  first  criticism  charges 
the  faculty  psychology  with  impotence;  the  second  charges  it 
with  seeking  by  false  pretences  to  conceal  its  impotence. 

Herbart  did  more  than  any  one  else  to  overthrow  the  doctrine 
of  faculties,  though  he  cannot  be  said  to  have  killed  it  {cf.  Lotze, 
Lipps,  Hofler). 

See  Braunschweiger,  op.  cit.^  17  ff. ;  Wundt,  Phys.  Psych.,  i,, 
1893,  II  ff.,  14  ff. ;  ii.,  482  ff. ;  G.  F.  Stout,  A  Manual  of  Psy- 
chology, 1899,  103  ff. 

(2)  There  are  four  uses  that  the  student  should  distinguish. 

{a)  Mind  itself,  as  a  *real  being'  or  'simple  substance,'  is 
endowed  with  self-activity  or  spontaneity.  This  usage  belongs 
to  metaphysics,  and  is  wholly  out  of  place  in  psychology,  which 
knows  nothing  of  real  beings.     Ebbinghaus,  Psych.,  i.,  1 1  ff. 

{b)  There  is  a  specific  process,  a  simple  and  elementary  ac- 
tivity-experience, to  be  found  in  certain  consciousnesses  along- 
side of  the  other  constituent  elements,  sensation  and  affection. 
Against  this,  see  the  author's  Outline  of  Psych.,  118  ff. 

{c)  There  is  to  be  found  in  certain  consciousnesses  {e.g.y  in  the 


f  43.   MtnUU  Activity  189 

attentive)  a  •  feeling  of  activity '  (including  the  feelings  of  activity 
proper  and  of  passivity  X  which  in  experience  is  sui  gtmris  and 
unanalysable,  but  in  structure  is  complex.  Cf.  Hamlin's  critique 
of  Wundt,  op.  cit.t  pp.  24  ff. 

(</)  "Mental  activity  exists  when  (and  so  far  as)  process  in 
consciousness  is  the  direct  outcome  of  previous  process  in  con- 
sciousness.*'    G.  F.  Stout,  Analytic  Psych.,  i.,  1896,  148. 

(3)  It  is  important  that  the  student  give  a  correct  answer  here, 
since  the  phrase  *  states  of  consciousness '  or  *  states  of  mind '  is 
still  current,  in  popular  parlance  and  in  certain  psychologies, 
as  the  equivalent  of  'consciousnesses'  or  'complex  conscious 
processes.*  The  word  *  state,'  as  employed  in  the  text,  is  the 
German  Zustand ;  it  designates  the  mode  or  form  of  existence 
which  —  if  we  may  use  the  metaphor  —  the  conscious  processes 
of  a  given  time  are  enjoying ;  their  relative  importance  or  relative 
obscurity  in  the  total  consciousness ;  their  fatness  or  leanness. 
We  speak  of  attention  as  a  *  state  of  consciousness  *  just  as  we 
speak  of  muddiness  as  a  *  state  of  the  roads,'  or  of  a  man's  afifairs 
as  'being  in  a  bad  state.'  The  'roads'  and  the  'affairs'  are, 
obviously,  different  from  the  muddiness  and  the  badness,  —  and 
that  is  the  difference  between  the  processes  attended-to  or 
attended-from,  and  attention  itself. 

A.  Attention  as  a  State  of  Consciousness.  — The  'clearness '  of  a 
process  is  a  synonym  for  its  *  best  state.'  Clearness  implies  (a)  a 
maximal  discriminability  or  separability  from  other  processes,  and 
(b)  a  maximal  reproductive  value  (value  for  memory,  association, 
imagination,  etc.)L  Hence  every  psychological  experiment  that 
aims  at  discrimination  presupposes  a  perfect  attention,  which  is 
also  the  precondition  of  effective  mental  work.  —  Kiilpe,  Out- 
lines, 37,  425. 

A  question  arises  here,  which  will  be  differently  answered  by  different 
theories.  **  The  processes  attended-from  are  rendered  less  clear  and  distinct." 
Less  dear  and  distinct  than  what?—  {a)  If  we  hold  that  the  essence  of  atten- 
tion is  inhibition,  the  repression  of  irrelevant  processes,  it  follows  that  the 
natural  or  normal  state  of  a  process,  —  say,  a  sensation,  —  is  its  attentive  state. 
In  that  event,  the  phrase  means :  less  clear  and  distinct  than  the  processes 
attended-to,  and  therefore  unnaturally  or  abnormally  obscure,  {b)  If  we  hold, 
00  the  other  hand,  that  the  essence  of  attention  is  a  positive  reinforcement  or 


190 


Attention  ami  Action 


facilitation,  then  the  natural  state  of  a  sensation  must  be  the  state  of  inatten* 
tion.  The  phrase  means,  in  this  case :  less  clear  than  the  processes  attended- 
to,  /.^.,  only  normally  dear,  {c)  If,  thirdly,  we  hold  that  attention  implies  both 
inhibition  and  facilitation,  the  natural  state  of  a  sensation  will,  again,  be  the 
state  of  inattention ;  but  this  state  will  lie  somewhere  between  the  extreme 
states,  of  elevation  and  depression,  that  characterise  the  contents  of  the 
attentive  consciousness.  The  phrase  will  now  mean  :  less  clear  and  distinct, 
not  only  than  the  processes  attended-to,  but  also  than  the  processes  given  in 
the  normal  state  of  inattention.  —  The  possibilities  should  be  weighed  from 
the  genetic  as  well  as  from  the  systematic  point  of  view. 

The  word  'rises'  in  law  (7)  is  used  technically,  as  the  equivalent  of  the 
German  Anklingen.  The  process  attended-to  *  comes  to  a  head,'  attains  its 
full  conscious  value,  more  quickly  than  the  others. 

Experiment  ( i ).  First  Law.  —  Puzzle  pictures  abound  in  the 
cheap  magazines,  though  they  are  as  a  rule  very  crude.  One  of 
the  best  of  those  known  to  the  author  is  a  purporting  diagram  of 
the  brain-convolutions  issued  by  the  Munich  art-journal  y//^^«^ 
at  the  time  of  the  Psychological  Congress  of  1896.  The  convolu- 
tions are  made  up  of  babies,  intertwined  in  all  sorts  of  postures. 
Some  observers,  if  no  suggestion  is  offered,  fail  to  find  the  babies 
at  all ;  others  find  them  only  after  an  appreciable  time.  When 
they  are  found,  the  diagram  becomes  fairly  alive  with  them,  and 
the  brain-perception  is  reduced  to  a  very  bare  and  vague  schema. 


Fig.  43. — The  three  faces  in  the  moon. 

Of  the  same  order  are  the  three  faces  —  the  coarse  full  face, 
the  foreshortened  three-quarter  face  and  the  profile  —  that  can 
be  found  on  the  disc  of  the  full  moon.  The  student  should  be 
asked  to  adduce  further  illustrations  of  the  law,  from  other 
sense-departments. 

Question  (4)  The  following  may  be  mentioned,  {a)  When 
an  overtone  is  heard-out  from  a  clang,  by  concentrated  atten- 


§  43*   AtUHtioM  as  Stat€  of  Co9uciousniss  191 

m,  the  tone  itself  becomes  clearer,  the  rest  of  the  clang  more 
indistincL  This  is  a  famous  and  much  discussed  instance  of  the 
*  efifect  *  of  attention,  {b)  Fechncr's  experiment :  two  forks  are 
held  to  the  two  ears,  and  the  resulting  tone  can  be  localised 
in  either  ear  by  direction  of  the  attention.  The  tone  on  the 
one  side  is  here  rendered  more  distinct,  the  tone  on  the  other 
side  depressed,  (r)  Helmholtz*  assertion  that  he  could  control 
the  phenomena  of  retinal  rivalry  by  attention  is  accepted  by 
Pilzecker  (pp.  33  f.);  cf,  Stumpf,  Tonps.,  i.,  244.  (</)  The  ob- 
taining of  the  plastic  effect  with  the  stereoscope  is  a  good  illus- 
tration. When  once  the  figures  have  fused,  we  lose  sight  of  the 
irregularities  and  flecks  and  roughnesses  that  bothered  us  at 
first,  and  wonder  that  we  could  have  failed  to  see  the  solid  form. 
More  striking  still  is  the  gradual  attainment  of  the  effect  by 
successive  instantaneous  illuminations  (electric  spark)  of  the 
stereoscopic  slide. 

Question  (5)  The  experiment  intended  is  the  familiar  one  of 
'bringing  out*  sensations  of  pressure,  warmth,  cold,  tickling, 
€tc.,  by  simple  concentration  of  the  attention  upon  some  portion 
of  the  skin.  It  is  best  to  choose  for  the  experiment  a  part  of 
the  body  that  is  under  stimulation  (ordinarily  unnoticed)  by 
clothing.  For  long-continued  attention  to,  e.g,^  the  finger  means 
vasomotor  changes  in  the  finger,  which  may  give  rise  to  tin- 
gling, pulsing,  or  what  not.  In  such  a  case  we  have,  not  an  en- 
hancement of  preexistent  sensations,  but  simply  the  observation 
of  sensations  which  are  due  to  the  same  conditions  that  have 
k  -cooperated  to  produce  the  attentive  state.  —  Pilzecker,  37  f. ;  D. 
Hack  Tuke,  Illustrations  of  the  Influence  of  the  Mind  upon  the 
Body,  etc.,  1884,  (2d  ed.)  i.,  33  f.;  H.  Maudsley,  The  Physi- 
ology of  Mind,  1876,  316  f.;  G.  A.  Tawney,  Philos.  Stud.,  xiii., 
1897,  203  f. 

Experiment  (2).  Second  Law.  — (a)  Not  only  is  the  selected 
component  intensified ;  it  is  possible,  by  successive  attentions, 
\  to  construct  a  melody  from  the  separate  tones,  while  the  whole 
chord  sounds  on  as  accompaniment.  Stumpf,  Tonps.,  ii.,  290. 
{b)  The  overtone  is  intensified ;  the  fundamental,  not.  An  at- 
tentive ninning-up  of  the  series  of  overtones  may  bring  out  a 
liigh  overtone  which,  with  discursive  attention,  remained  unob- 


192  Attention  and  Action 

served.    Melodies  may  be  constructed,  as  before  :  291  f.    {c)  No 
one  of  the  three  tones  is  intensified  :  293  f. 

This  intensification  must  be  very  carefully  distinguished  from  the  gain  in 
clearness  and  distinctness  which  falls  under  the  first  law.  It  occurs  only  in 
the  case  of  intrinsically  weak  sensations.  Stumpf  gives  the  following  in- 
stances, besides  those  selected  for  the  Experiment,  {d)  Singing  in  the  ear. 
"  While  the  subjective  tone  was  rising  or  disappearing,  it  could  be  unmistak- 
ably intensified  by  the  direction  of  attention  upon  it.  It  became  stronger,  not 
merely  clearer,  more  discriminable :  it  was  clear  and  readily  distinguished  in 
the  first  moment  of  remarking.  I  could  induce  the  intensification  not  only  by 
an  action  within  the  ear,  which  made  itself  known  by  a  muscle-sensation  and 
at  the  same  time  somewhat  raised  the  pitch  of  the  tone,  but  also  without  the 
action  and  the  rise  in  pitch.  This  latter  mode  of  intensification  was,  how- 
ever, possible  only  with  a  very  weak  intensity  of  the  tone"  (i.,  373  f.,  427). 
The  author  can  confirm  this  experience,  {e)  Noises  which  contain  tones, 
e.g.^  the  noise  of  the  train  as  heard  in  a  sleeping-car:  ii.,  292  f.  This  obser- 
vation is  easily  verified.  {/)  Difference-tones  :  ii.,  292,  354.  The  observa- 
tion requires  more  practice  than  the  preceding. 

It  seems  to  follow  that  the  positive  element  in  attention  (the  reinforcement 
or  facilitation)  is  the  condition  solely  of  the  increased  clearness  of  the  process 
attended-to ;  whereas  the  negative  element  (the  inhibition)  is  responsible  for 
an  intensification  of  weak  processes.  For  the  intensification  is  most  easily 
accounted  for  as  a  rise  of  the  weak  sensation,  by  the  removal  of  counter-influ- 
ences in  the  nervous  system,  to  the  full  (or  approximately  the  full)  intensity 
which  it  would  have  possessed  in  its  own  right  had  those  counter-influences 
been  absent  (Stumpf,  i.,  72,  374;  ii.,  293).  The  teleological  significance  of 
the  arrangement  is  evident ;  with  any  other,  a  reliable  series  of  judgments  of 
intensity  or  of  intensive  differences  would,  so  far  as  we  can  see,  have  been 
impossible.  A  maximal  degree  of  attention  is,  in  actual  fact,  the  sine  qua  non 
of  accurate  judgment.  But,  if  attention  exerted  an  intensifying  effect,  the 
weak  or  moderately  intensive  sound  would  be  strengthened  by  the  ver}'  act  of 
observation ;  the  attentive  following  of  a  diminuendo  would  be  impossible. 
The  facts  indicate,  further,  that  intensive  change  is  not  the  essential  feature 
of  the  attentive  state.  That  is  rather  to  be  sought  in  the  clearness  and  per- 
manence-for-judgment  of  the  objects  of  attention  (i.,  72  ;  ii.,  307  ;  cf.  ii.,  277  ff".). 

It  need  hardly  be  said  that  the  phenomena  of  attentive  intensification  are 
not  confined  to  the  sense  of  hearing.  They  can,  however,  be  there  observed 
in  exceptionally  pure  form. 

Cf.,  further,  G.  T.  Fechner,  In  Sachen  d.  Psychophysik,  1877,  85  f. ;  Re- 
vision d.  Hauptpuncte  d.  Psychophysik,  1882,  270  f. ;  and  ct.  MUnsterberg, 
Psych.  Rev.,  i.,  1894,  39  with  Hamlin,  op.  cit. 

Questions  (6),  (7)  These  Questions  may  be  similarly  an- 
swered.    A  process  is  intensified,  when  it  is  intrinsically  very 


§  43-   Intensity  and  Duration  in  Attention  193 

weak;  a  process  is  lengthened,  when  it  is  intrinsically  very 
short.  Instances  of  the  third  law  occur  in  all  experiments  with 
stimuli  of  brief  duration,  —  the  time-value  of  *  brief '  varying,  of 
course,  from  sense-department  to  sense-department. 

Nc«n8  proper,"*  says  Klilpc  (OutUnes,  432),  "  to  distinguish  between  a 
change  of  aensadons  and  sensation-attributes,  and  a  change  of  their  reproduc- 
tory  activity.  All  the  effects  of  attention  appear  to  fall  under  one  or  other  of 
these  rubrics."  Again  (429),  **  A  change  in  the  attributes  and  relations  of 
themselves  is  necessarily  confined  within  certain  narrow  limits, 
there  b  hardly  any  restriction  upon  change  of  judgment,  i.i.y  of  re- 
productioo.  At  the  same  time,  we  cannot  admit,  —  what  has  often  been  main- 
tained, —  that  a  change  of  the  former  kind  is  wholly  impossible.*"  And  (430), 
•*  In  any  case,  attention  produces  its  maximal  effect  in  the  reproductory  sphere." 

Except  that  he  inclines  to  coordinate  clearness  (a  direct  change  in  the  re- 
lations of  sensations)  with  pcrmanence-for-judgment  (a  reproductory  effect), 
the  author  can  subscribe  to  these  statements.  It  is  extremely  tempting  to 
assert,  off-hand,  that  attention  increases  both  the  intensity  and  the  duration 
of  the  process  attended-ta  But  we  have  seen  that  there  is  no  evidence  of  in- 
tensification in  the  case  of  intrinsically  strong  sensations ;  and  that  the  inten- 
sification of  weak  sensations  is  rather  a  coming  of  the  processes  to  their 
intensive  rights,  than  a  positive  reinforcement  of  their  intensities.  The  same 
thing  holds,  in  the  author's  judgment,  of  duration.  Attention  cannot  lengthen 
an  intrinsically  durable  process.  On  the  other  hand,  it  helps  intrinsically 
tranfient  processes  to  their  full  conscious  effect,  by  removing  counter-influ- 
ences that  would  tend  to  swamp  them ;  it  lengthens  brief  processes  in  pre- 
cisely the  same  way  that  it  strengthens  weak  processes.  The  teleology  of  this 
is.  again,  evident.  With  any  other  arrangement,  exact  judgments  of  durations 
or  of  temporal  differences  would  be  impossible. 

The  author  knows  of  no  very  satisfactory  way  to  demonstrate  directly  the 
truth  of  this  third  law.  M  0\%  subjected  to  a  slow  succession  of  brief  stimuli 
(noises  of  moderate  intensity,  or  brief  flashes  of  weak  light  from  a  pierced 
disc  revolving  before  a  window  in  the  wall  of  the  dark  room),  and  his  atten- 
tion diverted  from  these  stimuli  for  a  little  time  by  conversation  or  directions, 
it  is  often  possible  to  evoke  later  on  the  (attentive)  judgment :  "  They  seem, 
now  that  I  look  at  them  or  listen  to  them,  to  last  longer  than  they  did  just 
now,  when  you  were  talking  to  me."  If  thb  pronouncement  come  without 
suggestion,  it  may  be  accepted  as  evidence  of  the  law.  It  must,  of  course,  be 
nuuie  of  the  series  at  large,  and  not  of  particular  terms  in  the  series.  —  Indi- 
rect evidence  is  afforded  by  the  fulness  of  CTs  introspection,  the  number  of 
characteristics  that  he  has  remarked,  in  the  attentive  state,  as  compared  with 
its  poverty  in  the  state  of  inattention. 

This  attentive  lengthening  of  a  simple  impression  must  by  no  means  be 
cunfiised  either  with  the  permanence-for-judgment  (reproductory  permanence) 
referred  to  above,  or  with  what  is  called  the  '  inertia  of  attention  *  Q*  the  atten- 
o 


194  Attention  and  Action 

tion  holds  fast  to  something  already  given  more  easily  than  it  finds  something 
that  has  to  be  looked  for").  See  Stumpf, Tonps.,  i.,  244  f.,  386,  391  ;  ii.,  318, 
358  ;  Fechner,  Abh.  d.  kgl.  sachs.  Ges.  d.  Wiss.,  vii.,  395  ;  Revision  d.  Haupt- 
puncte  d.  Psychophysik,  1882,  283. 

Question  (8)  The  fourth  law  is  borne  out  by  the  verdict  of 
introspection  in  all  cases  of  attentive  observation.  When  one 
has  found  the  puzzle-figure  or  the  overtone,  and  is  attending-to 
it,  the  rest  of  the  puzzle-picture  and  the  rest  of  the  clang  do  not 
stand  out  in  a  middle  degree  of  clearness  above  the  sights, 
sounds,  etc.,  of  one's  surroundings ;  they  are  as  indistinct  and 
obscure  as  these  surroundings.  If  one  has  singled  out  two 
overtones,  by  the  attention,  these  two  tones  stand  with  equal 
clearness  in  the  foreground  of  consciousness :  one  cannot  hear 
the  one  more  clearly  than  the  other,  and  sense  both  more  clearly 
than  the  remaining  processes  in  consciousness.  Hold  the  two 
hands  to  the  ears,  and  rub  together  the  forefinger  and  thumb  of 
each  hand.  You  can  divide  the  attention  equally  (though  not 
for  any  length  of  time)  between  the  two  noises ;  you  cannot  dis- 
tribute it  more  to  the  one  than  to  the  other,  and  to  both  more 
than  to  what  is,  e.g.y  before  your  eyes.  The  rule  holds  in  every 
case :  while  "  we  are  compelled  by  certain  facts  of  the  mental 
life  to  speak  of  at  least  two  different  states  of  consciousness, 
which  may  vary  in  degree  "  (Kiilpe),  introspection  never  reveals 
to  us  more  than  two  states  in  a  given  consciousness,  no  matter 
what  the  degrees  of  clearness  or  obscurity  may  be.  Pass  be- 
yond the  second  state,  and  you  come  to  the  unconscious,  i.e.\ 
psychologically,  to  nothing. 

Great  care  must  be  taken,  in  observations  of  the  kind  here  described,  to 
avoid  an  oscillation  of  the  attention  from  contents  to  contents.  Such  oscilla- 
tion is,  as  we  shall  see  (in  the  meantime,  cf.  Stumpf,  ii.,  317),  characteristic 
of  attention  in  general ;  it  may  escape  an  untrained  introspection,  and  thus 
give  rise  to  the  illusion  of  three  grades  of  conscious  clearness. 

Experiment  (3).  fifth  Law.  —  In  its  classical  form  (Urbant- 
schitsch),  this  experiment  is  performed  with  the  ticking  of  a 
watch  as  stimulus.  O  is  seated  sidewise  to  the  length  of  a  cor- 
ridor or  large  room.  He  may,  if  he  desire,  plug  the  ear  which 
is  not  to  be  used  for  observation.  E  draws  a  chalk  line  upon 
the  floor,  from  a  point  immediately  below  (9's  ear  to  a  point 


§  43-    Fluctuations  off  Attention  195 

some  8  to  10  ra.  distant.  The  watch  is  moved  out,  along  this 
line  and  at  the  level  of  (/%  ear,  until  the  noise  of  its  ticking  is 
but  just  supraliminal :  if  the  tick  is  very  loud,  the  watch  should 
be  wrapped  in  a  cloth.  The  resulting  intemiittcnces  of  sound 
are  clear  and  very  striking. 

This  experiment  is  sufficient  to  prove  the  fact  of  fluctuation, 
and  may,  perhaps,  be  given  by  way  of  introduction  to  that  of 
the  text.  O  must,  in  any  case,  be  put  through  a  course  of  prac- 
tice, lasting  at  least  as  long  as  the  experiment  itself,  with  the 
Masson  disc :  the  kymograph  need  then  be  used  only  for  the 
experiment  proper.  Sustained  effort  of  observation,  and  a 
mechanisation  of  the  hand-movements,  are  essential  to  the 
obtaining  of  valid  results. 

pRELiMi.NARiEs.  —  THc  drum  should  be  set,  if  the  mechanism 
of  the  kymograph  permits,  for  revolution  once  in  60  to  100  sec. 
When  longer  times  are  taken,  O  (at  any  rate,  in  this  stage  of 
practice)  grows  inattentive,  and  the  results  are  therefore  un- 
trustworthy. 

Note  that,  in  the  arrangement  recommended  in  the  text,  the 
crests  of  the  curve  of  fluctuation  represent  disappearances,  and 
the  valleys  reappearances  of  the  grey  ring.  This  mode  of  re- 
action is,  for  most  (9's,  preferable  to  that  in  which  the  bulb  is 
pressed  at  reappearance  of  the  sensation. 

Lange  noted  the  points  of  maximal  sensation  intensity;  MUnsterberg  (85) 
insisU  that  the  moment  of  disappearance  is  more  certainly  remarked.  Eckener 
required  his  (7s  to  raise  the  finger  at  disappearance,  and  lower  it  at  reappear- 
ance (359)  ;  Pace  had  the  button  of  a  reaction-key  pressed  at  disappearance, 
and  released  at  reappearance  (391).  In  Lehmann's  investigation,  the  rubber 
bulb  was  preited  when  the  minimal  sensation  changed  (76). 

Question  (9)  The  length  of  the  attention  wave,  as  reg- 
istered in  these  experiments,  is  extremely  variable.  It  will 
probably  amount  to  6  or  8  sec,  though  it  may  rise  as  high  as 
18  or  20  sec  The  author  has  records  in  which  waves  of  2  and 
of  24  sec  duration  occur.  Such  extreme  times  are  suspicious  ; 
indeed,  in  the  great  majority  of  cases,  they  are  thrown  out  by 
the  introspective  account.     See  Questions  ( 1 1 X  ( 1 2). 

(10)  It  will  probably  be  found  that  the  time  of  disappearance 
is  considerably  shorter  than  the  time  of  appearance.     The  relap 


196  Attention  and  Action 

tion  varies  with  the  character  of  the  stimulus-difference.  The 
more  nearly  liminal  this  is,  —  the  more  nearly  the  grey  resembles 
the  white,  —  the  longer,  proportionately,  are  the  times  of  dis- 
appearance. The  clearer,  greyer,  the  grey,  the  shorter  are  the 
disappearances. 

The  relation  can  be  more  easily  traced  if  the  periods  in  question  are  sharply 
marked  upon  the  fluctuation  curve.  This  may  be  effected  by  substituting  for 
the  rubber  bulb  a  pneumatic  reaction -key.  O  holds  the  button  of  the  key 
down,  during  the  absence  of  the  grey,  and  lets  it  spring  up  again  when  the 
grey  returns.  The  curve  thus  runs  at  two  levels :  the  upper  lines  repre- 
sent the  periods  of  disappearance,  the  lower  the  periods  of  persistence  in 
consciousness. 

Minimal  stimuli  or  stimulus-differences  are  chosen  for  the 
reason  that  any  blurring  or  indistinctness  of  the  corresponding 
sensations  or  sensation-differences  will  mean  their  complete  dis- 
appearance. It  is  far  easier  to  say  that  we  do  or  do  not  hear  or 
see  something  than  it  is  to  be  sure  that  what  we  see  or  hear  has 
grown  more  or  less  clear.  Indeed,  the  attention  seems  to  be  no 
more  able  (if  we  may  use  the  expression)  to  induce  fluctuations 
upon  a  continuous  intensive  stimulus  than  it  is  to  lengthen  or 
strengthen  an  intensive  sensation. ^     Cf.  Marbe,  636. 

(11)  Objective  sources  of  error,  inherent  in  the  mode  of  reg- 
istration, may  be  neglected.  Important  are :  (a)  inattention, 
(J?)  distraction,  (c)  maladjustment  of  the  peripheral  organ.  O 
must  give  his  full  and  (though  the  phrase  is  really  a  contradic- 
tion in  terms)  his  continuous  attention  to  the  stimulus.  Other- 
wise, the  fluctuations  of  the  grey  ring  will  indicate,  not  crests 
and  valleys  of  the  attention  wave,  but  alternations  of  attention 
to  stimulus  and  attention  to  the  ideas  constituting  the  con- 
sciousness of  the  time.  Secondly,  disturbing  stimuli  must,  so  far 
as  possible,  be  ruled  out.  At  the  best,  however,  the  movements 
of  breathing,  the  rustling  of  clothes,  etc.,  remain  as  possibly 

^This  does  not  mean,  of  course,  that  we  can  hold  a  bright  light  or  a  strong  sound 
steadily  before  consciousness,  by  continuous  attention.  Attention  is  intrinsically  in- 
termittent. What  happens  is,  that  the  intensive  impression  remains  unchanged 
until  it  is  presently  relegated  to  the  background  of  consciousness  by  some  intruding 
(or  rather,  relieving)  impression  or  idea.  So  long  as  we  are  concentrating  our 
attention  upon  it,  it  does  not  show  the  oscillations  that  are  characteristic  of  minimal 
stimuli. 


§  43*    FluctnatioHS  of  AiUntiim  197 

distracting  stimuli.  Thirdly,  an  unsteady  fixation  or  a  change 
of  accommodation  may  bring  the  grey  ring  to  disappearance. 

Fortunately,  a  trained  O  is  able  by  introspection  to  discrimi- 
nate between  these  accidental  or  artificial  oscillations  and  the 
true  fluctuations  of  attention.  And  the  quantitative  procedure 
comes,  here  as  so  often,  to  the  aid  of  qualitative  analysis.  On 
the  one  hand,  by  direct  comparison  of  the  kymograph  curve 
with  d7s  written  record,  E  can  identify  the  *good'  and  the 
had  *  fluctuations ;  on  the  other,  this  record  is  made  more  care- 
iul  and  more  reliable  by  (7's  knowledge  that  the  curve  will  bear 
him  out  in  the  truth  and  detect  him  in  falsehood.  Cf.  what 
was  said  above  of  the  plethysmographic  curves,  p.  181. 

(12)  This  question  raises  the  whole  problem  of  the  fluctua- 
tions of  attention.  The  best  general  account  is  that  given  by 
Wundt,  Phys.  Psych.,  ii.,  295-301.  A  programme  for  investi- 
gation may  be  made  out  as  follows. 

{a)  Variation  of  Stimuli.  —  For  sight,  it  is  probably  best  to 
use  two  Masson  discs,  the  one  showing  grey  on  white  (black 
radius),  the  other  grey  on  black  (white  radius).  For  sound,  we 
may  take  the  ticking  of  a  watch,  or  the  continuous  hiss  of  the 
flame  of  a  Bunsen  burner :  if  the  experiments  are  performed 
cry  early  in  the  morning  or  late  at  night,  the  gas-pressure  will 
be  constant.  For  touch,  some  form  of  the  interrupted  current 
may  be  employed  (Lange,  401  ;  Lehmann,  •J^).  —  In  every  case, 
the  intensity  of  stimuli  and,  in  the  case  of  sight,  the  magnitude 
of  the  stimulus-difference  should  be  varied  (Marbe,  622,  624). 

{Jb)  Variation  of  Registration.  —  We  have  noted  two  modes 
of  registration :  a  continuous  following  of  the  course  of  atten- 
tion by  pressure  on  the  rubber  bulb,  and  a  sharp  demarcation 
of  periods  of  disappearance  from  periods  of  disappearance  by 
pressure  on  a  pneumatic  reaction-key.  To  these  may  be  added 
a  registration  of  maximal  appearances  only,  i.e.^  a  determination 
of  the  highest  point  on  the  crest  of  each  attention  wave.  The 
pneumatic  key  will  serve  here ;  or  recourse  may  be  had  to  an 
ordinary  key  and  an  electro-magnetic  marker. 

[N.  Lange,  who  was  the  first  systematically  to  investigate  the 
fluctuations  of  attention,  and  who  worked  by  the  last-named 
method,  found  that  the  attention  period  (the  time-interval  from 


198  Attention  and  Action 

maximum  to  maximum  of  sensation)  was  but  little  variable 
within  a  given  sense-department.  His  values  were ;  for  sight, 
3.4  sec,  for  sound,  3.8  sec,  and  for  electrical-cutaneous  im- 
pressions, 2.5  sec  In  view  of  the  results  of  later  observers, 
both  the  regularity  and  the  smallness  of  these  times  call  for 
explanation.  Wundt  (296)  accounts  for  them  partly  in  terms  of 
method  (the  attention  adjusts  itself  more  easily  and  regularly 
to  the  stimuli),  and  partly  in  terms  of  stimulus  intensity  (choice 
of  just  clearly  supraliminal  values):  cf.  Marbe,  622,  632.  Eck- 
erier  (375)  suggests  the  influence  of  a  preconceived  theory  ; 
Miinsterberg  (in),  the  rhythm  of  respiration.  Lehmann  (69) 
points  out  that  his  own  method  (that  of  the  text)  favours  a  con- 
tinuous attention-strain,  whereas  Lange's  method  favours  a  pulsa- 
tion of  attentions,  a  succession  of  tensions  and  relaxations.  The 
two  methods  are,  therefore,  directed  upon  different  phenomena. 
Lehmann  does  not  attempt  an  explanation  whether  of  the  extreme 
regularity  of  Lange's  times  or  of  the  times  themselves.] 

{c)  Regulation  of  Stimidus.  —  Helmholtz  remarked,  in  ex- 
periments with  a  Masson  disc,  that  the  just  noticeable  grey 
does  not  remain  constant ;  on  the  contrary,  as  the  experiment 
proceeds,  greys  become  visible  which  at  first  were  unnoticed 
(Phys.  Optik,  ist  ed.,  314  f . ;  2d  ed.,  391).  Pace  (391)  found 
that  the  fluctuations  of  attention,  with  a  constant  stimulus,  are 
abrupt  at  the  beginning  of  an  experimental  series,  gradual 
towards  its  close.  It  follows  from  these  observations  that  ex- 
periments should  be  made  during  which  the  stimulus  remains 
not  objectively  but  subjectively  constant.  The  conditions  are 
fulfilled  if  we  employ  a  Masson  disc  under  such  circumstances 
that  its  two  or  three  outermost  *  grey  rings  *  are  at  first  imper- 
ceptible, and  direct  O  to  shift  his  fixation-point  to  these  rings  as 
they  become  successively  visible. 

[Pace  (394),  working  in  this  way,  found  a  fluctuation  period 
of  3.5  sec,  with  a  small  m.  v.  Wundt  (296  f.)  notices  the  cor- 
respondence of  this  time  with  the  value  obtained  by  N.  Lange. 
The  agreement  is,  indeed,  most  striking ;  but  Lange's  results 
are  not  explained  by  it.] 

(<^)  Variation  of  State  of  the  Sense-organ.  —  Pace  (399  f.) 
found  that  paralysis  of  the  muscles  of  accommodation  by  a  i  % 


$  43-    Fluctuations  of  Attention  199 

solution  of  Homatropinum  hydrobromicum  left  the  fluctuations 
unaffected.  Urbantschitsch  and  Eckener  (360)  note  that  flue- 
tuations  are  observed  by  ears  lacking  a  tympanic  membrane. 

(r)  Simuitaneous  Registration  of  the  Breathing  Curve, — 
Lehman n  (j^^  79)  shows  that  there  is  a  close  connection  be- 
tween fluctuation  of  attention  and  breathing  rate  in  the  case  of 
cutaneous  stimuli.     Cf  Wundt,  297  f. 

(/)  Duplication  of  Stimulus.  —  Eckener  (368)  performed  ex- 
periments with  two  simultaneous  stimuli  from  the  same  sense- 
department  (e.g.,  watch-tick  and  Bunsen  burner);  Lange  (400) 
employed  two  disparate  stimuli  (watch-tick  and  Masson  disc). 
Cf  Wundt,  299  f. 

(g)  Obsen'otion  of  Mcfttory  Images.  —  Lange  (409  f.)  noticed 
a  fluctuation  of  memory  images,  as  well  as  of  peripheral  sensa- 
tion ;  and  regards  the  memory  image  as  the  essential  part  of  the 
mechanism  of  fluctuation.  Eckener  (370,  379)  further  investi- 
gated the  fluctuation  of  the  memory  image.  Cf  Fechner  on 
the  oscillation  of  the  memory  after-image :  Elemente  d.  Psy- 
chophysik,  1889,  ii.,  493 ;  and  see  p.  43  above,  on  the  oscillation 
of  after-images  proper. 

{h)  Introspection.  —  It  is  very  desirable  that  some  one  should 
do  for  these  fluctuations  what  Bolton  and  Meumann  have  done 
for  the  phenomena  of  subjective  accentuation  :  secure  and  pub- 
lish full  introspective  reports  of  the  course  of  consciousness 
during  the  experiment.  Miinsterberg  condemns  Lange's  results 
in  to/0  (82  f.);  Lehmann  (74  f.)  thinks  that  Eckener's  rarely 
occurring  'objective*  fluctuations  (361)  are  the  fluctuations  to 
be  observed,  and  that  his  'subjective'  fluctuations  are  simply 
matters  of  inattention;  Wundt  (301)  believes  that  Eckener's 
subjective  fluctuations  are  identical  with  those  that  Lehmann 
registered ;  and  the  author,  who  can  confirm  Eckener's  observa- 
tions, is  of  the  same  opinion.  In  view  of  the  acknowledged 
competency  of  introspection  in  this  field  (Wundt,  299;  Munster- 
berg,  86;  Eckener,  362;  Pace,  401  ;  Lehmann,  74),  and  of  the 
refinement  now  attained  by  the  method  of  registration,  it  would 
seem  advisable  to  make  a  systematic  appeal  to  introspection  for 
the  settlement  of  the  disputed  issues. 

Literature. — V.  Masson,  Comptes  rendus,  xviiL,  1844,  289; 


200  Attention  and  Action 

Ann.  de  Chimie  et  de  Physique,  3me  s6r.,  xiv.,  1845,  129; 
Fechner,  Helmholtz,  Wundt,  as  quoted ;  V.  Urbantschitsch, 
Centralblatt  f.  d.  medic.  Wiss.,  1875,  626;  Pfluger's  Arch.,  xxiv., 
1881,  574;  xxvii.,   1882,  440;    N.   Lange,   Philos.    Studien,   iv., 

1888,  390;  H.  Munsterberg,  Beitrage  z.  exp.  Psychologic,  ii., 

1889,  69;  H.  Eckener,  Philos.  Studien,  viii.,  1893,343;  E.  Pace, 
ibid.,  388  ;  K.  Marbe,  ibid.y  615  ;  A.  Lehmann,  ibid.,  ix.,  1894,  66) 
A.  Pilzecker,  op.  cit.,  55  ff.  W.  Heinrich  has  recently  asserted 
that  pure  tones  do  not  fluctuate :  see  H.  O.  Cook,  Amer.  Journ. 
of  Psych.,  xi.,  1899,  119,  436. 

(13)  This  question  must  be  answered  from  the  literature.  It 
falls  into  two  part  questions  :  (a)  Is  the  seat  of  the  fluctuations 
central  or  peripheral.?  and  (b):  In  the  former  event,  are  the 
fluctuations  attributable  to  the  mechanism  of  attention  or  to 
some  other  central  mechanism  ?  Munsterberg  and  Heinrich 
declare  for  a  peripheral  seat,  and  so  close  the  second  question. 
Marbe  and  Lehmann  declare  for  the  centre,  but  not  overtly  for 
the  attention.  Pace,  and  still  more  forcibly  Eckener,  refer  the 
phenomena  to  the  attention. 

See  W.  Heinrich,  Die  moderne  physiologische  Psychologie  in  Deutschland, 
2d  ed.,  Zurich,  1899. 

Experiment  (4).  Sixt/i  Law. — The  experiment  upon  the 
range  of  attention  is  best  performed  with  visual  stimuli,  "be- 
cause visual  impressions  can  most  easily  be  selected  with  a  view 
to  their  apprehension  as  independent  ideas  "  (Wundt,  Human 
and  Animal  Psych.,  241  ;  Phys.  Psych.,  ii.,  287).  Two  methods 
have  been  employed  for  the  determination.  The  first  is  that  of 
instantaneous  illumination  (Dove,  Zollner,  Helmholtz);  an  elec- 
tric spark  is  flashed  before  the  object-card,  in  a  dark  room,  and 
O  is  required  to  describe  what  he  has  seen  (Helmholtz,  Phys. 
Optik,  710).  This  method  has  fallen  into  disuse.  The  second 
method,  that  of  the  tachistoscope,  is  better  adapted  to  general 
laboratory  purposes.  The  tachistoscope  consists,  in  principle, 
of  a  falling  screen  or  shutter  which,  in  dropping  or  opening, 
exposes  the  object-card  for  a  brief  and  accurately  variable  time. 

The  name  *  tachistoscope '  was  suggested  by  A.  W.  Volkmann  (Sitzungs- 
ber.  d.  kgl.  sachs.  Ges.  d.  Wiss.,  1859,  90).    One  of  the  best  known  demon- 


§  43-   Riinge  of  Atttntum 


20I 


•tntkHiaJ  forms  of  the  instrument  is  Wundt's  fall-chronometer,  figured  in  the 
Phys.  Psych.,  ii.,  391 ;  H.  and  A.  Psych.,  242.  It  consisU  of  an  upright  back 
of  blackened  wood,  3  m.  high,  furnished  with  lateral  guides,  in  which  the 
screen  runs.  The  screen  is  held  up  by  a  spring  catch,  and  carries  a  white 
fixalion-mark  upon  iu  lower  surface.  When  the  spring  is  released,  the  screen 
drops,  and  in  blling  exposes  an  object <ard,  33  by  33  cm.,  upon  which  are  4 
rows  of  letters  or  figures,  about  6  by  4  cm.  The  card  is  completely  re-covered 
when  the  screen  comes  to  rest.  The  upper  line  of  letters  is  exposed  for 
about  ao9  sec.,  the  lowest  line  for  about  0.07  sec.,  and  the  middle  lines  for 
some  0.08  sec    The  observers  sit  at  a  disunce  of  2  to  3  m. 


Fig.  44.  —The  apparatus  of  Goldicheider  and  MQUer. 


A  smaller  and  more  exact  £dl-chronometer  is  described  by  J.  McK.  Cattail, 
Philos.  Stud.,  iii.,  1886,  97,  307 ;  Brain,  viii.,  1885,  295  ;  cf.  J.  Zeitler,  Philos. 
Stud.,  xvi.,  1900,  381.  A  pendulum  tachistoscope  is  figured  by  Wundt,  Phys. 
Psych.,  ii.,  334  (improved  form  in  Zimmermann's  caulogue,  1897,  8).  The 
arrangement  of  the  text,  in  which  the  rotating  disc  is  made  to  do  duty  as  a 
tachistoscope,  is  practically  that  of  A.  Goldscheider  and  R.  F.  Mliller,  Zeits.  f. 
klin.  Medizin,  xxiii.,  1893,  134.  This,  in  turn,  may  probably  be  regarded  as  a 
simplified  form  of  the  apparatus  devised  by  Helmholtz  (Phys.  Optik.  514),  and 
used  by  N.  Baxt  (PflUger's  Arch.,  iv.,  1871.  325)  and  S.  Exner  (Sitzungsber. 
d.  wien.  Akad.,  Ivili.,  2,  1868,  601).  It  is  clear  that  the  es-sential  parts  of  the 
rhythm  apparatus  (p.  349)  can  be  employed  for  the  experiment.  As  the  same 
parts  can  be  used  again,  later  on,  in  the  Association  experiment,  the  author 
has  recommended  the  disc  and  motor  in  preference  to  a  fall-chronometer.  A 
cheap  form  of  the  latter  is  described  in  his  Primer  of  Psych.,  92  f. 


202  Attention  and  Action 

Materials. — The  dimensions  given  in  the  text  are  those 
which  the  author  has  employed.  Length  of  tube,  size  of  disc, 
etc.,  may  be  varied  as  convenience  suggests. 

Since  the  disc  is  to  stand  vertically,  the  movable  sector  must 
be  cut  to  give  an  even  balance.  Let  the  central  circle,  to  which 
the  sector  is  attached,  have  a  radius  of  lo  cm.,  and  continue 
the  counter-sector  outwards,  on  the  opposite  side,  for  $  cm. 

If  the  experiment  is  to  be  carried  beyond  its  first  stage,  ob- 
ject-cards must  be  prepared  in  which  the  simple  figures  are 
replaced  by  numerals  and  letters  (sense  and  nonsense  arrange- 
ments). These  must,  in  some  cases,  be  arranged  upon  different 
lines :  short  words,  e.g,,  are  best  arranged  in  three  lines.  The 
simpler  figures  may  also  be  arranged  in  patterns,  which  occupy 
more  than  one  line  upon  the  card.  The  time  of  exposure  may 
then  be  correspondingly  increased  to  0.04,  0.06,  etc.,  sec. 

If  one  row  of  figures,  filling  the  field  vertically,  is  exposed,  the  time  of 
exposure,  Z",  is  twice  the  time  required  for  the  sector  to  pass  a  point :  i.e.y 

T—  2  R  ( —7-  \  where  R  is  the  rate  of  revolution,  and  S  is  the  angular  magni- 
tude of  the  sector.  Thus,  for  i  revolution  in  the  i  sec,  and  an  opening  in 
the  disc  of  3.6°,  we  have  T=i  f  ^^  J  =  .02  sec.     If  several  rows  of  figures  are 

shown,  this  proposition  does  not  hold.  Thus,  with  a  sector  of  10.8°  and  3 
lines  of  figures,  the  time  of  exposure  of  each  line  is  .04  sec. 

Let  /  be  the  time  required  for  the  sector  to  pass  a  point  —  t  —  R  f  -y-  J  —  and 

let  //i  and  h^  be  the  heights,  respectively,  of  the  total  exposure  field,  and  of  the 
portion  of  it  (figures  or  lines)  whose  time,  7\,  is  to  be  determined.^    Then 

7'i  =  /+[/-^^);  7\=/  +  -j^  =  / (  i+^j.     It  is  important  that  this  formula  be 

understood ;  cf.  the  instance  worked  out  by  Goldscheider  and  Muller,  1 54  f. 

Note  that,  in  any  case,  the  exposure  time  is  not  by  any  means 
coincident  with  the  excitation  time.  The  after-effect  of  stimu- 
lation in  the  visual  apparatus  is  of  considerable  duration.  See 
answer  to  Question  (2),  below. 

*  The  values  h\  and  hi  may  be  found  by  direct  measurement ;  h\  may  also  be 
obtained  by  the  following  geometrical  process.  The  apparatus  furnishes  two  similar 
triangles,  whose  common  vertex  is  the  observing  eye.  The  base  of  the  one  triangle 
is  the  width  of  the  open  sector  (taken  at  the  left  side  of  the  lumen  of  the  tube),  and 
that  of  the  other  triangle  is  h\.  Then  the  side  of  the  first  triangle  is  to  the  side  of 
the  second  triangle  as  the  sector  opening  is  to  h\. 


{  43*  R^ng€  of  Atutttion  a03 

For  words  and  letters,  the  type  known  as  grotesque  or  gothic 
(without  serifs  and  hair-lines)  should  be  employed.  Cf,  E.  C. 
Sanford,  Amer.  Joum.  of  Psych.,  i.,  1888,  424. 

Preliminaries.  —  G^  unused  eye  must  be  closed  as  in  the 
caropimetrical  experiments. 

Question  (14)  The  results  vary,  according  to  the  complex- 
ity, familiarity,  'meaning*  of  the  figures.  On  the  average,  it  is 
safe  to  put  the  maximal  range  of  attention  at  4  to  5  simple  im- 
pressions (lines,  letters,  numerals),  and  at  about  three  times  this 
number  of  word-elements  (2  or  3  short  monosyllabic  words).  See 
Cattell,  Philos.  Studien,  iii.,  1886,  I26f. ;  Wundt,  Phys.  Psych.,  ii., 
287  f.;  Philos.  Studien,  XV.,  1900,  311  ;  Goldscheider  and  Muller, 
csp.  135,  142  f.,  151  f.,  154;  B.  Erdmann  and  R.  Dodge,  Psy- 
chologische  Untersuchungen  iiber  das  Lesen,  auf  experimenteller 
Grundlage,  Halle,  1898,  137,  140;  Zeitler,  412. 

The  method  employed  in  the  experiment  is  the  most  favourable  possible  to 
a  wide  ranj^  of  attention.  The  number  of  figures  increases  regularly  from 
test  to  test ;  and  the  exposure  of  the  figures  is  repeated,  at  i  sec.  intervals, 
until  final  judgment  is  passed.  The  former  of  these  rules  means  that  O  enters 
upon  the  successive  experiments  with  a  definite  and  definitely  directed  expec- 
tation ;  the  second  means  that  his  *  mental  preparation '  for  the  impressions 
which  he  finally  apperceives  b  of  a  very  high  order.  ^ 

An  *  objective*  O  does  not  abuse  these  advantages.  If,  however,  E  has 
any  reason  to  suppose  that  the  suggestions  of  the  method  are  too  strong  for 
accuracy  of  result,  he  must  take  one  or  two  sets  of  cards  in  haphazard  order, 
and  so  check  the  *■  procedure  with  knowledge  *  by  a  procedure  '  without  know- 
ledge.'    Cf.  Zeitler's  criticism,  422  ff. 

(15)  This  question  is  answered  by  Wundt  as  follows. 

{a)  The  duration  of  stimulus  must  be  short  enough  to  pre- 
clude eye  movements. 

(b)  The  stimulus  must  be  of  so  limited  an  extent,  and  its 
position  so  accurately  defined  by  the  fixation-mark  which  is 
shown  before  exposure,  that  all  of  its  constituents  can  be  seen 
with  approximately  equal  distinctness,  i.e.,  that  the  total  image 
falls,  to  all  intents  and  purposes,  within  the  area  of  direct  vision. 

^  It  does  not  nean,  for  introspection,  that  a  roving  of  the  attention  occurs,  so  that  the 
varioQs  parts  of  the  field,  distinctly  seen  in  soccesshre  expotures,  presently  fit  themselves 
together.  O  is  clear  upon  the  point  that  the  final  judgment  is  a  judgment  of  simul- 
taneous apprebensKML    See  answer  to  Qaestion  17  (Ot  below;  and  cf.  Zeitler,  593  £ 


204  Attention  and  Action 

In  consideration  of  the  special  requirements  of  the  present 
experiment,  we  may  add  that  the  number  of  objects  thus  offered 
to  direct  vision  must  be  greater  than  the  number  that  can  be 
simultaneously  apperceived. 

(r)  The  time  of  exposure  must  begin  at  the  same  moment 
over  all  parts  of  the  exposed  field.  Or,  at  any  rate,  there  must 
be  n6  noticeable  time-differences  in  the  illumination  of  the  vari- 
ous regions. 

{a)  The  state  of  retinal  adaptation  must  be  as  favourable  as 
possible.  Especially  must  sudden  transitions  from  dark  to  light 
be  avoided. 

{e)  Persistent  after-images  of  the  exposed  stimuli  must  be 
ruled  out. 

(/)  The  time  of  exposure  must  be  short  enough  to  preclude  the 
roving  of  attention  from  one  part  to  another  of  the  exposed  field. 

{g)  Provision  must  be  made,  in  arrangmg  the  apparatus,  for 
the  giving  of  a  ready-signal  at  the  proper  interval  before  ex- 
posure.    Philos.  Stud.,  XV.,  289. 

(16)  One  of  the  requirements  of  a  good  instrument  is  that 
there  shall  be  no  noticeable  time-differences  in  the  illumination 
of  the  various  parts  of  the  field.  We  may  take  this  to  imply 
that  the  mode  of  exposure  is  indifferent,  provided  that  there  is 
no  introspective  evidence  of  roving  of  attention,  and  no  chance 
given  for  eye  movements.  And  this  is  Wundt's  view :  Philos. 
Studien,  xv.,  291  ff.,  303  ;  xvi.,  1900,  65.  Goldscheider  and 
Miiller  think  that,  if  there  is  a  subsequent  roving  of  attention, 
the  mode  of  exposure  determines  the  course  of  apperception,  even 
though  the  exposure  itself  were  regarded  as  instantaneous  ( 1 54  f.). 
Erdmann  and  Dodge,  on  the  other  hand,  emphasise  the  necessity 
of  a  simultaneous  exposure  (Ueber  das  Lesen,  94  ff. ;  Zeits.  f. 
Psych.,  xxii.,  1900,  243).  It  would  be  well  worth  while  to  re- 
investigate the  roving  of  attention  under  exact  conditions  :  cf. 
Zeitler,  404;  Dodge,  Psych.  Rev.,  viii.,  1901,  56;  Wundt,  Vol- 
kerpsych.,  L,  i,  1900,  540  ff. 

(17)  The  experiments  with  letters,  numerals  and  words  may 
suggest  themselves.  E  may  also  wish  to  compare  the  result  of 
successive  minimal  exposures  with  that  of  a  single  wider  expos- 
ure.    The   carrying-over   of   the  experiment  to  another  sense- 


§43-   ^  "^  205 

department,  r.g'.,  to  sound,  changes  the  character  of  the  en- 
quiry. Sec  Wundt,  Phys.  Psych.,  il,  288,  292,  on  the  question 
of  the  range  of  consciousness. 

Additional  Questions.  — (17  a)  Why  has  the  electric-spark 
method  been  abandoned .' 

The  disturbance  of  adaptation  (a)  impairs  the  objective  appre- 
hension of  the  stimuli,  and  {d)  hinders  introspection  of  the  per- 
ceptive process.     Wundt,  Philos.  Studien,  xv.,  301. 

(17  ^)  How  long  may  the  exposure  be  made,  consistently  with 
the  avoidance  of  eye  movement  ? 

At  least  .25  sec     Wundt,  307,  and  the  preceding  discussion. 

{17  r)  What  is  the  *  roving 'of  attention.^  Is  introspection 
able  to  detect  it } 

The  attention  may  travel  from  part  to  part  of  a  total  idea  or 
perception.  Suppose,  e.g^.,  that  the  figures  of  the  object-card  are 
retained  as  after-image  or  memory  after-image.  Then  the  atten- 
tion may  turn  successively  from  figure  to  figure,  although  the  time 
of  exposure  lay  well  within  the  eye  movement  limit.  Wundt, 
309  f.  —  Introspection  detects  the  roving.  Groups  of  5  or  6  nu- 
merals, e.g.,  are  apprehended  in  two  parts  or  halves ;  groups  of 
words  in  part-groups.  Cf.  M.  Friedrich,  Philos.  Stud.,  i.,  1883, 
66  f. ;  but  see  also  the  refs.  under  (16)  above. 

(17  d)  How  far  does  our  arrangement  satisfy  the  requirements 
of  a  good  tachistoscope }  —  Answer  from  Question  (15). 

Experiment  (5).  Seventh  Law.  —  Materials. — There  is,  of 
course,  no  guarantee  that  the  gearing  of  the  metronome  clock- 
work is  so  accurate  that  the  ring  and  its  stroke  are  precisely 
simultaneous.  The  author  is  accustomed  to  test  the  instrument 
as  follows,  (a)  Remove  the  floor  of  the  clock  chamber,  turn 
the  metronome  upside-down,  and  move  the  pendulum  very  slowly 
to  and  fro.  If  you  detect  any  discrepancy  between  the  ring  and 
the  stroke,  at  any  one  of  the  possible  settings  of  the  bell  adjust- 
ment, reject  the  instrument,  {b)  Having  selected  a  metronome, 
set  the  pendulum  vibrating  at  144  or  152  to  the  i  min.,  and  let 
two  practised  O's  (Instructors,  or  students  who  have  worked 
with  other  appliances)  listen  to  the  series  of  sounds,  the  one 
concentrating  his  attention  upon  the  succession  of  strokes,  and 
the  other  upon  the  succession  of  rings.     If  the  former  is  able  to 


2o6  Attention  and  Action 

hear  the  stroke  before  the  ring,  and  the  latter  to  hear  the  ring 
before  the  stroke,  the  instrument  may  be  considered  available. 

The  stroke  should  be  *  thinned '  for  the  experiment  by  remov- 
ing the  floor  of  the  clock  chamber  and  mounting  the  metronome 
on  a  layer  of  felt :  cf.  p.  175  of  the  text. 

Experiment.  — {a)  It  is  natural,  in  this  case,  that  the  attention 
follow  the  strokes,  as  the  more  frequent  and  insistent  impressions. 
Hence,  while  it  is  not  difficult  to  hear  ring  and  stroke  together, 
O  will  probably  say  (without  any  suggestion  or  direction  from  the 
Instructor)  that  the  ring  comes  later  than  the  stroke.  He  should 
then  try,  by  voluntary  effort,  to  realise  the  three  possibilities : 
simultaneity,  bell  earlier,  bell  later.  The  observation  *  bell  earlier ' 
will  be  occasional  and  intermittent,  if  it  occur  at  all.  {b)  In  this 
case,  the  rings  come  at  short  intervals,  so  that  they  form  as  obvi- 
ous and  distinct  a  series  as  the  strokes.  O  will  probably  declare 
for  simultaneity.  Purposed  direction  of  attention,  however,  will 
readily  change  his  judgment  to  *  bell  earlier '  or  *  bell  later.'  Note 
that,  in  the  former  event,  the  stroke  is  very  indistinct  ;  it  is 
swamped  in  the  'fall*  of  the  bell-tones;  and  that,  when  once 
the  attention  has  taken  a  definite  direction,  it  is  not  easy  to 
change  from  this  to  the  other  (' inertia'  of  attention). 

Question  (18)   The  seventh  law  is  valid. 

(19)  The  experiments  on  attentional  time-displacement  form 
one  of  the  most  interesting  and  most  difficult  chapters  of  experi- 
mental psychology.  They  are  intimately  connected  —  by  way  of 
the  eye-and-ear  observations  of  astronomy  —  with  the  simple  re- 
action experiment :  see  the  references  on  the  history  of  the  simple 
reaction,  p.  213. 

The  instrument  employed  in  the  classical  investigations  of  the 
subject  is  the  complication  pendulum.  The  earlier  and  cruder 
form  of  this  apparatus  (1861)  is  figured  by  Wundt,  Human  and 
Animal  Psych.,  270;  a  more  elaborate  form,  which  allows  of  the 
simultaneous  release  of  a  visual  impression,  a  bell-stroke,  a  cuta- 
neous pressure,  arid  one  or  more  cutaneous  electrical  stimuli,  is 
figured  in  the  Phys.  Psych.,  ii.,  405. 

On  the  complication  method,  see  Wundt,  Philos.  Studien.,  i.,  1881,  34  f . ; 
XV.,  1900,  579;  on  the  defects  of  the  current  instruments,  Mind,  N.  S.,  ix., 
1900,  287.     For  experimental  results,  see  W.  von  Tschisch,  Philos.  Studien, 


S  43.   DtUrminants  of  AtUnHom  ioy 

ti^  1885, 603 ;  C.  D.  Pflaum,  jilu^  xv.,  139.     For  modificattons  of  method,  see 

T    R.  Angell  and  A.  H.  Pierce.  Amer.  Jour,  of  Ps)xh..  iv.,  1892,  531  tf . ;  J. 

istrow,  «Im^.,  v.,  1892,  341  • 

An  iofcnkms  student  wtU  find  no  dit!iciUty  in  reproducing  Wundt's  first 

appwmtus,  or  in  adapting  the  vernier  chronoscope  to  the  present 


experiment  by  arranging  that,  r.^.,  an  electric  shock  be  given  simultaneously 
with  a  sound  or  light  stimulus.  Tne  instrument  devised  by  Angell  and  Pierce 
is  fairly  cnsy  of  construction ;  but  the  author  has  not  used  it.  Apparatus  of 
the  type  of  Sanford^  pendulum  circuit  breaker  (Amer.  jour,  of  Psych.,  vi., 
189$,  $81  ff.)  may  also  be  employed. 

Question  (20)  The  explanations  given  should  be  both  psycho- 
physical and  psychogenetic.  That  is  to  say,  we  must  account 
for  the  effect  of  the  stimulus  for  attention  both  in  terms  of  brain 
mechanics  and  in  terms  of  the  development  of  the  organism. 

The  principal  conditions  are  as  follows. 

(a)  //i^p*  Iniensity  of  Stimulus :  or  its  EqutvaUniy  Great  Extension.  — 
The  psychophysical  process  is  here  one  of  relatively  great  strength,  and  is  there- 
fore  not  easily  suppressed  by  counter-exciutions.  —  Pilzecker,  19 ;  KUlpe,  438. 

{b)  Suddenness  of  Stimulus.  —  This  has  two  psychophysical  reasons  :  the 
increased  excitability  of  the  ner\'ous  elements  affected,  due  to  their  previous 
rest  from  stimulation  of  this  especial  kind  ;  and  the  fact  that  exciutions  sud- 
denly set  up  are  not  so  much  weakened  as  other  excitations  are  by  having  part 
of  their  energy  drained  off  mto  secondary  nervous  channels.  —  Pilzecker,  20. 
Long  duration  of  stimulus,  on  the  other  hand,  means  a  constantly  increasing 
waste  of  energy  by  such  drainage :  MlUler,  125  ff. ;  Pilzecker,  20 ;  ct.  KUlpe,  438. 

(<)  Connection  of  the  Stimulus  with  the  Present  Contents  of  Consciousness. 
— The  more  nearly  the  excitation  correlated  with  a  given  stimulus  coincides  with 
an  excitation  now  in  progress  within  the  psychophysical  portion  of  the  nervous 
system,  the  more  easily  will  it  make  its  way  and  the  more  dominant  will  it  be. 

—  Pilzecker,  19.  This  condition  holds  not  only  when  the  like  excitation  is 
actually  in  progress,  but  also  when  the  excitation  correlated  with  the  stimulus 
coincides  with  a  form  of  excitation  habitual  to  the  sensorium  in  question. 

If  our  attention  is  directed  upon  an  auditory  stimulus,""  says  Pilzecker, 

-  auditory  stimuli  will  be  those  that  most  readily  come  to  consciousness."" 
To  which  we  may  add :  if  we  are  acousticians  or  aurists  by  profession,  auditory 
topics  will  at  all  times  have  a  ready  entry  to  our  consciousness. 

(</)  Novelty  of  Stimulus.  —  *  Novelty "  means,  psychologically,  •  non-asso- 
datednesB.*  The  novel  impression  is  the  impression  that  lacks  associative 
supplements  in  consciousness :  that  stands  alone,  in  isolation.  It  is  evident 
that  such  an  impression,  having  no  distracting  impressions  by  ito  side,  ^  can 
receive  a  measure  of  attention  which  is  altogether  impossible  when  it  is  accom- 
panied or  surrounded  by  a  numl>er  of  other  objects  of  perception""  (Kiilpe). 
This  sentence  is  easily  translated  into  psychophysical  terms.  ~  Here  belong 


2o8  Attention  and  Action 

also  the  influences  of  contours  and  of  simultaneous  contrast.  Pilzecker,  20 ; 
KUlpe,  438;  Lipps,  Suggestion  u.  Hypnose,  1898  (Sitzungsber.  d.  k.  bayer. 
Akad.  d.  Wiss.,  1897),  424. 

{e)  M(n>ement  of  Stimulus,  —  The  influence  of  movement  is  explained  by 
the  avoidance  or  reduction  of  fatigue  in  the  parts  of  the  organ  stimulated. 
Pilzecker,  20 ;  Stumpf,  Tonps.,  ii.,  337  ff. ;  KUlpe,  300  f. 

In  all  these  cases,  we  have  offered  a  proximate  explanation  of 
the  effect  of  the  condition.  Such  explanation  must  always  be 
attempted,  even  in  cases  where  (as  in  the  instance  of  Movement, 
above)  its  inadequacy  is  patent  from  the  outset.  We  may  believe 
with  Cattell  (Psych.  Rev.,  vii.,  1900,  343)  that  ** perceptions  are . .  . 
in  large  measure  the  result  of  experience  and  utility,"  ^  but  they 
must  still  have  a  psychophysical  substrate,  on  the  one  hand ; 
and,  on  the  other,  the  bare  reference  to  utility  does  not  explain 
them. 

When  we  enquire  into  the  psychogenetic  reasons  for  the  value 
of  the  conditions  named,  we  find  that  the  conditions  themselves 
fall  into  three  groups.  The  first  group  includes  intensity ;  ex- 
tension ('  voluminousness,*  in  James'  phraseology) ;  and  sudden- 
ness and  novelty,  in  so  far  as  they  are  also  reducible  to  intensity. 
Intensity  appeals  to  the  organism  as  organism  :  we  cannot  think 
of  an  organised  being  which  should  disregard  intensive  impres- 
sions in  its  environment,  and  yet  survive.  Even  civilised  man, 
with  all  his  powers  of  educated  self-restraint,  *  starts'  when  he 
hears  a  loud  sound,  and  has  his  eyes  drawn  irresistibly  to  a  brill- 
iant light.  *  Connection  with  the  present  contents  of  conscious- 
ness '  is  a  condition  of  a  different  order.  It  becomes  effective  at 
a  much  later  stage  of  mental  development  than  does  intensity  : 
at  a  stage  when  mind  has  passed  beyond  the  inconsequence  of 
sense-impression,  and  has  reached  the  level  of  more  or  less  con- 
tinuous imagery.  The  third  group  of  conditions  includes  move- 
ment, and  suddenness  and  novelty  in  so  far  as  these  exert  a 
specific  influence,  set  up  a  definite  affective  reaction.  The 
group  may  be  termed,  with  James,  the  group  of  *  instinctive  stim- 
uli.' The  "perception  is  one  which,  by  reason  of  its  nature 
rather  than  its  mere  force,  appeals  to  some  one  of  our  normal 
congenital  impulses,  and  has  a  directly  exciting  quality"  (i., 

1  Cf.  what  is  said  of  the  place  of  history  in  a  theory  of  perception,  p.  228  below. 


{  43-    7>/  Stnse-proctssts  in  Attrm/um  209 

41 7>  Of  the  •  why  *  of  this  appeal  we  can  say  only  that,  given 
the  course  of  development  as  we  know  it,  the  organism  must 
have  attended  to  movement,  etc.,  in  its  surroundings,  or  have 
paid  the  penalty  of  inattention  with  its  life.  The  moving,  the 
new  and  the  sudden  are  all  possible  —  even  probable  —  sources 
of  danger.     C/.  the  author's  Outline,  139,  275  ;  Primer,  191. 

B.  Tk€  Sense-processes  in  Attention.  —  Question  (21)  The 
IccHS  eiassicus  for  the  strain-sensations  in  attention  is  Fechncr, 
Elem.  d.  Psychophysik,  1889.  ii.,  475  (cf.  490  f.).  The  reader 
must,  of  course,  make  allowance  for  Fechner's  terminology,  and 
discount  his  identification  of  strain-sensation  with  strain  of  at- 
tention :  the  account  was  published  in  i860. 

<*  If  we  turn  our  attention  from  one  sense-department  to  another,  we  have  at 
the  nine  time  a  definite /r/'/zw^  of  the  change  of  direction.  The  feeling  is  in- 
describable, but  any  one  can  readily  reproduce  it  in  experience.  We  may  term 
it  the  feeling  of  a  change  of  localisation  of  tension.  We  feel  a  forward  direc- 
tion of  tension  in  the  eyes  or  a  lateral  direction  of  tension  in  the  ears,  —  a 
tension  that  increases  with  the  degree  of  attention,  —  according  as  we  are 
attentively  fixating  something  or  attentively  listening  to  something ;  so  that 
people  speak  commonly  of  a  *  strain  of  the  attention '  itself.  We  feel  the 
difference  most  clearly  if  we  shift  the  direction  of  attention  quickly  back  and 
forth  between  eye  and  ear.  We  get  the  same  feeling,  differently  localised 
about  the  different  sense-organs,  when  we  are  trying  to  taste,  smell  or  touch 
anything  with  discrimination. 

**  But  more :  I  have  a  feeling  of  tension,  precisely  analogous  to  that  which  I 
get  with  keen  concentration  of  sight  or  hearing,  when  I  am  trying  to  envisage 
as  clearly  as  possible  some  image  of  memory  or  of  fancy ;  and  this  precisely 
similar  feeling  is  very  differently  localised.  With  the  keenest  possible  con- 
centration upon  external  visual  objects  or  upon  after-images,  the  tension  has 
an  unmistakable  forward  direction ;  and  if  the  attention  is  turned  to  other 
sense-departments,  this  direction  changes,  according  to  the  position  of 
the  external  sense-organs :  but  the  rest  of  the  head  is  free  from  all  feeling 
of  strain.  When,  on  the  other  hand,  memory  or  imagination  is  actively  em- 
pk>yed,  the  feeling  of  tension  withdraws  altogether  from  the  external  sense- 
organs,  and  seems  rather  to  have  its  seat  in  that  portion  of  the  head  which 
contains  the  brain.  If  I  try  to  represent  some  scene  or  person  to  myself 
with  espedal  vividness,  the  vividness  of  the  representation  depends,  not 
upon  the  forward  strain  of  the  attention,  but  rather  (if  I  may  say  so)  upon  its 
retraction  inwards.^ 

A  hardly  less  well-known  passage  is  that  in  James'  Psychology, 
1890,  i..  3CO. 


2IO  Attention  and  Action 

"Whenever  my  introspective  glance  succeeds  in  turning  round  quickly 
enough  to  catch  one  of  these  manifestations  of  spontaneity  in  the  act,  all  it 
can  ever  feel  distinctly  is  some  bodily  process,  for  the  most  part  taking  place 
within  the  head.  .  .  . 

"In  the  first  place,  the  acts  of  attending,  assenting,  negating,  making  an 
effort,  are  all  felt  as  movements  of  something  in  the  head.  In  many  cases  it 
is  possible  to  describe  these  movements  quite  exactly.  In  attending  to  either 
an  idea  or  a  sensation  belonging  to  a  particular  sense-sphere,  the  movement  is 
the  adjustment  of  the  sense-organ,  felt  as  it  occurs.  I  cannot  think  in  visual 
terms,  for  example,  without  feeling  a  fluctuating  play  of  pressures,  convergences, 
divergences  and  accommodations  in  my  eyeballs.  The  direction  in  which  the 
object  is  conceived  to  lie  determines  the  character  of  these  movements,  the 
feeling  of  which  becomes,  for  my  consciousness,  identified  with  the  manner  in 
which  I  make  myself  ready  to  receive  the  visible  thing.  My  brain  appears  to 
me  as  if  all  shot  across  with  lines  of  direction,  of  which  I  have  become  conscious 
as  my  attention  has  shifted  from  one  sense-organ  to  another,  in  passing  to 
successive  outer  things,  or  in  following  trains  of  varying  sense-ideas. 

"When  I  try  to  remember  or  reflect,  the  movements  in  question,  instead  of 
being  directed  towards  the  periphery,  seem  to  come  from  the  periphery  in- 
wards and  feel  like  a  sort  of  withdrawal  from  the  outer  world.  As  far  as  I 
can  detect,  these  feelings  are  due  to  an  actual  rolling  outwards  and  upwards 
of  the  eyeballs,  such  as  I  believe  occurs  in  me  in  sleep,  and  is  the  exact 
opposite  of  their  action  in  fixating  a  physical  thing.  In  reasoning,  I  find 
that  I  am  apt  to  have  a  kind  of  vaguely  localised  diagram  in  my  mind, 
with  the  various  fractional  objects  of  the  thought  disposed  at  particular 
points  thereof;  and  the  oscillations  of  my  attention  from  one  of  them  to 
another  are  most  distinctly  felt  as  alternations  of  direction  in  movements 
occurring  inside  the  head." 

The  student  should  read  also  the  next  two  paragraphs  of  p. 
301,  and  the  remarks  on  pp.  435  f.  The  passage  quoted  is  a  fine 
piece  of  introspection,  marred  only  by  the  pictorial  reference  to 
the  'lines  of  direction  *  shooting  across  the  brain. 

Kohn  {op.  cit.,  48)  remarks  :  "  If  we  consider  the  proofs  that  James  adduces 
for  the  presence  of  these  feelings,  we  find  that  they  speak  not  for  such  presence 
at  all,  but  simply  for  the  possibility  of  discovering  these  feelings  by  the  direc- 
tion of  attention  upon  them."  "  If  the  feelings  were  present  while  the  attention 
is  directed  upon  some  other  object,  there  would  be  no  need  at  all  of  the 
*  turning  round '  or  the  *  introspective  glance.'  We  should  be  conscious  of 
them  without  this."  To  which  the  obvious  reply  is,  that  we  are  conscious  of 
them  <  without  this ' ;  otherwise  there  would  be  no  cue  for  introspection.  We 
do  not  attempt  to  introspect  the  non-existent.  But,  when  we  are  giving  a 
psychological  account  of  any  contents,  we  examine  it  in  the  state  of  attention. 


$  43-   AtUntioH  and  Afftctive  Process  211 

Hie  ttrain-scnsations  are  present  in  the  nurgin  of  conadonniess  while  we  tm 
attending  to  something  else ;  when  we  set  to  work  to  describe  these  sensations 
for  psychology,  we  attend  to  them. 

As  to  the  part  played  in  attention  by  these  strains  and 
tensions,  we  must  distinguish  between  the  strains  themselves 
and  the  sensations  arising  from  them.  Pilzecker  {op,  cit,,  40)  if 
probably  right  when  he  says:  "We  must  regard  these  motor 
phenomena  not  as  mere  accidental  concomitant  phenomena; 
they  are  rather  an  integral  part  of  the  mechanism  of  the  sen- 
sory attention,  and  help  to  constitute  and  to  maintain  it."  Cf, 
Wundt's  law  of  the  correspondence  of  apperception  and  fixation 
(Phys.  Psych.,  ii.,  108,  145)1  On  the  other  hand,  the  strain- 
sensations,  "  in  view  of  the  great  variety  of  sources  from  which 
they  are  derived,  must  be  regarded  not  as  constitutive,  but  only 
as  consecutive  characteristics  of  the  state  of  attention.  They 
stand  guard  over  attention,  so  to  speak,  to  prevent  its  too  per- 
sistent occupation  with  a  single  object ;  and  their  growing  un- 
pleasantness is  a  warning  signal  of  excess  of  function  in  some 
particular  part  of  the  nervous  system,  which  must  ultimately 
prove  harmful  to  the  organism  "  (Kiilpe,  Outlines,  436). 

(22)  Ct.  Helmholtz,  Phys.  Optik,  2d  ed.,  890  f.,  with  Hering, 
Hermann's  Hdbch.,  iii.,  i,  1879,  548. 

(23)  No.  Strain-sensations  are,  at  best,  a  measure  of  the 
effort  made  in  attending,  not  of  the  degree  of  attention  given. 
It  would  be  more  nearly  true,  perhaps,  to  say  that  the  intensity 
of  the  strain-sensations  would  afford  an  inverse  measure  of  the 
degree  of  attention,  since  it  is  when  we  attend  most  easily  that 
we  attend  best,  and  when  we  attend  with  the  greatest  effort  that 
we  attend  worst.  But  this  statement  also  requires  qualification. 
Ct.  the  author's  Outline,  146  ff.  with  Miinsterberg,  Beitrage,  IL, 
1889,  24  f 

C.  Attention  and  Affective  Process. — Question  (24)  Refer- 
ences must  suffice  here :  the  Instructor  will,  naturally,  answer 
the  general  question  in  terms  of  his  own  psychological  system. 

(a)  Tonps.,  i.,  68.  (h)  Phys.  Psych.,  i.,  588.  (c)  Principles, 
ii.,  344  f.  (d)  Outlines,  439.  {e)  Outline,  156.  (/)  Psy- 
chologic, 263,  266.     {g)  Phys.  Optik,  606. 


212  Attention  and  Action 


EXPERIMENT  XXVI 


§  44.  The  Simple  Reaction.  —  The  reaction  experiment  is  in- 
troduced here  solely  for  its  '  qualitative '  value.  It  gives  O  an 
opportunity  to  introspect  the  typical  *  motive'  —  the  impulse  — 
under  standard  conditions ;  it  trains  him  in  the  control  of  atten- 
tion ;  it  furnishes  an  introspective  foundation  upon  which  more 
complicated  experiments  may  later  be  based  ;  it  is  the  key  to  a 
large  and  very  important  section  of  psychophysical  literature. 
The  author  believes  that  this  view  of  the  experiment  is  justified 
by  its  results ;  and  believes,  further,  that  the  treatment  in  the 
text,  incomplete  though  it  is  (and  at  this  stage  must  be)  on  the 
psychological  as  well  as  on  the  technical  side,  is  in  principle 
the  right  treatment.  The  details  of  theory  and  of  method, 
passed  over  here  without  discussion,  will  be  supplied  in  vol.  ii. 
In  the  meantime,  the  Instructor  may,  of  course,  extend  the 
experiment  as  far  beyond  the  author's  limits  as  time  permits. 

Questions  (i),  (2),  (3).  —  These  questions  may  be  answered, 
most  simply  and  directly,  from  the  author's  Primer  of  Psychol- 
ogy. 1899,  ch.  ix. 

Materials.  —  The  vernier  chronoscope  is  described  by  its 
inventor,  E.  C.  Sanford,  in  the  Amer.  Journ.  of  Psych.,  ix., 
1898,  191,  and  by  the  author  in  his  Primer  of  Psychology,  182. 
It  is  cheap  ($5.00),  and  works  satisfactorily.  The  following  are 
points  not  noted  in  the  text. 

The  silk  is  ordinary  *  button-hole  twist.'  It  should  be  waxed  over  the 
length  that  is  threaded  through  the  bobs,  to  prevent  wear  by  friction.  The 
long  pendulum  should  be  slung  in  the  red,  and  the  short  in  the  white  silk : 
this  arrangement  makes  the  determinations  easier. 

The  rod  b  is  set  cornering,  that  the  threads  may  hang  from  an  edge.  The 
grooves  in  the  surface  of  b  prevent  the  threads  from  spreading,  and  thus  alter- 
ing the  pendulum  length. 

The  keys  are  set  upon  posts,  in  order  that  they  may  have  a  capacity  of  ver- 
tical adjustment,  and  so  be  brought  into  their  right  relation  to  the  pendulums. 
The  keys  must  be  so  set  as  to  release  the  bobs  with  as  little  independent  mo- 
tion as  possible.  The  threads  of  the  two  pendulums  should  lie  in  approxi- 
mately the  same  plane  when  the  face-hooks  are  caught  in  the  hooks  /. 

The  upper  bar  of  the  key  turns  on  the  screw  as  a  pivot.  The  screw  may 
be  tightened  or  loosened  as  the  working  of  the  bar  demands.  The  spring, 
which  acts  upon  the  downward  projecting  cam,  holds  the  key  either  closed  or 


§  44-    The  Vemur  Chronoscopy  213 

open.  A  alight  lift  of  the  spring  (z^.,  with  a  aoew-driver)  on  the  button-sid« 
of  the  cam  fKilitates  dosing ;  a  similar  lift  on  the  lips-side  faciliutes  opening. 

Step  {d)  may  be  omitted ;  and  San^ord  recommends  that  the  student  in 
every  case  proceed  at  once  from  (O  to  (/):  -the  short  pendulum  U  better 
regulated  by  the  long  one  than  directly  by  the  watch."  This  is  not  the 
author's  experience,  though  Sanford's  method  presents  no  especial  difficulty. 
In  counting  swings,  as  in  counting  beats  (p.  37  of  the  text),  one  must  either 
begin  with  *  nought,'  or  throw  off  one  at  the  end  of  the  count. 

In  most  cases,  the  chronoscope  can  be  set  up  during  a  single  laboratory 
period ;  the  required  length  of  the  pendulums  is  suggested  by  the  base  steps. 
If^  howe\'er,  the  Instructor  sees  that  time  is  likely  to  be  wasted  in  the  attempt 
to  make  the  units  exact,  he  may  advise  that  rough  determinations  be  accepted, 
and  an  arithmetical  correction  introduced  into  the  results.  '*  Suppose,  z^., 
that  the  long  pendulum  is  found  to  swing  148  times  in  2  min.,  and  that  coin- 
cidences occur  ever)'  37  swings.  This  will  mean  that  the  time  of  a  single  swing 
of  the  long  pendulum  b  0.81  sec,  and  that  the  short  pendulum  makes  38 
swings  to  37  of  the  long.  The  unit  of  the  instrument  is  then  0.0213  (o-^i  -^ 
38  =  0.0213),  instead  of  0.02,  as  it  would  be  if  exactly  adjusted.  In  this  case 
the  final  records  would  be  reduced  to  hundredths  of  a  second  by  multiplying 
by  2.13  instead  of  by  2*"  (Sanford). 

Some  CTs  have  a  tendency  to  count  short,  /.^.,  to  record  coincidence  before 
it  has  been  reached.  This  tendency  must  be  controlled  and  corrected  by  the 
Instructor.  It  is  better  for  inexperienced  (7s  in  general  to  count  too  far  (to 
one  or  two  beyond  coincidence) ;  the  point  of  coincidence  is  then  certainly 
attained,  and  the  extra  swings  can  easily  be  thrown  ofT.  In  cases  of  doubt 
between  two  swings,  the  mean  must  be  taken  {e.g.^  ^coincidence  at  both  10 
and  II '  must  be  recorded  as  •  coincidence  at  10.5').  Hut  exact  counting  is, 
in  reality,  a  much  easier  matter  than  these  directions  seem  to  make  it. 

The  numerical  results  should  always  be  stated  in  terms  of  the  i  sec.  Thus, 
a  reaction-time  of  8  swings,  or  8  fiftieths  of  a  second,  would  be  registered  as  .16. 

Literature.  —  The  vernier  was  first  applied  to  time  meas- 
urement by  the  Leyden  astronomer  F.  Kaiser  (1806- 1872),  who 
explains  the  principle  of  application  in  two  papers,  published  in 
1 85 1  and  1863. 

The  history  of  the  *  personal  equation '  is  extremely  interest- 
ing, and  should  (if  time  permits)  be  given  in  lecture.  A  popu- 
lar account  will  be  found  in  Wundt's  Human  and  Animal  Psy- 
chology, 1896,  Lect.  xviii.  For  a  more  technical  exposition,  see 
Sanford,  Amcr.  Joum.  of  Psych.,  ii.,  1888-9,  3»  271,  403-  The 
Instructor  should  also  be  familiar  with  Wundt's  Phys.  Psych., 
il,  305-362,  and  with  the  article  by  L.  Lange  (Philos.  Studien, 
iv.,  1888,  479)  in  which  the  difference  between  'sensorial'  and 


214  Attention  and  Action 

'muscular*  reactions  is  noted  and  explained.^  A  recent  paper 
by  N.  Alechsieff,  in  the  Philos.  Studien,  xvi.,  1900,  i  ff.,  con- 
tains a  sound  discussion  (pp.  17-21)  of  the  three  forms  of  simple 
reaction. 

It  should,  perhaps,  be  said,  even  in  so  elementary  a  treatment  as  the 
present,  that  there  is  some  divergence  of  opinion  as  to  the  value  and  univer- 
sality of  the  sensorial-muscular  distinction.  The  reader  who  wishes  to  form  a 
judgment  in  the  question  must  acquaint  himself  with  the  literature  of  the 
reaction  experiment  (especially  articles  in  Pfluger's  Arch.,  Philos.  Studien, 
Mind,  Psych.  Rev.,  Amer.  Journ.  of  Psych.),  and  with  the  doctrine  of  mental 
types  (fairly  complete  bibliography  in  L.  W.  Stern,  Ueber  Psych,  d.  individ- 
uellen  Differenzen,  1900).  The  controversies  seem  to  hinge  on  two  different 
conceptions  of  the  experiment.  Some  investigators  regard  the  reaction 
method  as  a  method  for  the  discovery  of  psychological  facts  and  laws  in  gen- 
eral ;  others  regard  the  reaction  experiment  as  an  end  in  itself,  as  offering  a 
certain  typical  consciousness  (or,  rather,  a  series  of  typical  consciousnesses) 
for  introspection.  It  is  clear  that  the  training  required  of  O,  and  the  direc- 
tions given  him  before  the  experiment,  will  differ  very  considerably  in  these 
two  cases.     It  is  the  second  interpretation  that  is  followed  here. 

A.    ( I )   The  *  Natural '  or  *  Central '  Reaction. 

Preliminaries.  —  It  is  very  important  that  (9's  and  -£"'3  ex- 
perimental records  shall  tally.  Simple  as  the  injunction  is,  that 
everything  vciwst  be  put  down,  it  is  an  injunction  which  inexpe- 
rienced students  are  continually  disobeying.  E  and  O  should 
therefore  prepare  blank  Tables,  with  lines  numbered  i  to  10,  and 
should  have  it  impressed  upon  them  that  if  there  is  nothing  to 
enter,  say,  under  8,  the  next  entry  must  nevertheless  be  made 
under  9.  It  is  most  annoying  (and,  without  these  precautions, 
it  is  very  common)  to  have  the  records  of  50  conscientiously 
performed  experiments  handed  in  by  E  and  O,  and  to  find  a  gap 
on  the  one  side  or  the  other  which  cannot  be  localised  by  mem- 
ory, and  which  therefore  prevents  the  intercomparison  of  times 
and  introspections. 

It  is  important,  again,  that  O  shall  not  centre  his  attention 
upon  the  length  of  the  reaction  experiment,  and  make  it  a  point 
to  '  react  as  quickly  as  possible.*     If  this  tendency  become  mani- 

1  Lange,  like  most  discoverers,  was  anticipated.  The  sensorial-muscular  difference 
was  remarked  by  S.  Orschansky,  in  an  article  published  in  the  Neurol.  Centralblatt, 
1887,  no.  12,  265. 


{  44-    T^^  Central  or  Natural  Rioctian  2\% 

fest,  he  should  be  assured  that  he  has  nothing  at  all  to  do  with 
the  duration  of  the  experiment :  the  time  values  are  E^  affair, 
and  come  into  account  for  O  only  in  so  far  as  they  serve  as  a 
check  upon  his  introspections.  If  O  gives  reaction  times  of  .6 
and  .2  sec,  and  yet  has  no  introspective  difference  to  record  as 
between  the  two  experiments,  it  is  clear  that  his  introspection 
is  inadequate :  a  .6  sec  consciousness  cannot  be  identical  with 
a  .2  sec  consciousness.  In  this  way,  the  times  are  useful ;  and 
they  are  useful,  further,  for  comparison  with  the  reaction  norms. 
So  many  thousands  of  simple  reaction  times  have  been  taken, 
and  the  times  differ  so  little  from  observer  to  observer,  and 
from  year  to  year  with  the  same  observer,  that  we  know  approxi- 
mately what  the  time  in  question  '  ought '  to  be.  But  O  is  not 
concerned  with  the  duration  of  reaction  in  any  more  direct  way. 
He  must  not,  by  any  means,  try  to  estimate  the  time  of  a 
•good*  reaction,  and  then  seek  to  reproduce  this  time  in  later 
experiments. 

This  second  difficulty  may  be  avoided,  if  O  is  free  from  prejudice  at  the  out- 
let, by  a  careful  choice  of  words  on  the  Instructor's  part.  The  phrase  *as 
soon  as'  should  never  be  employed.  O  is  to  move  his  finger  *on  hearing* 
or  » when  he  hears'  the  sound ;  not  *  as  soon  as  possible  after'  he  has  heard  it. 

Tfu  Central  or  Natural  Reaction,  —  It  will  be  noticed  that  no 
specific  directions  are  given  in  the  text  as  to  (9's  manner  of  re- 
acting in  this  experiment.  He  is  left  to  face  the  situation  in 
his  own  way,  to  react  *  naturally.'  Now  we  saw  above,  pp.  xxv. 
ff.,  that  the  observers  in  psychological  laboratories  fall  into  two 
great  classes,  as  subjective  and  objective.  We  shall,  therefore, 
expect  to  find  characteristic  differences  of  reaction  as  between 
different  (7's.  "One  man  is  accustomed  to  take  up  an  active 
attitude  to  everything  that  occurs  to  him  :  his  own  action  is  for 
him  the  constant  point  of  interest,  and  his  environment  is  of 
importance  only  in  so  far  as  it  affects  this  centre  of  reference ; 
he  therefore  keeps  his  personality,  his  *I,'  in  instant  readiness 
for  action.  Another  is  wont  to  submit  himself  passively  to  the 
operation  of  external  impressions ;  he  regards  them  from  the 
theoretical  point  of  view,  is  contemplative  in  disposition.  The 
former  is  inclined  to  make  himself  'ready  for  the  leap';  his 


2l6 


Attention  and  Action 


fingers  are  tense,  and  the  psyche  is  intent ;  he  merely  awaits  the 
signal  for  action.  The  latter  tends  as  naturally  to  a  sensorial 
direction  of  attention  :  if  we  force  him  to  think  of  himself,  and 
to  dispose  himself  for  the  coming  movement  before  the  occasion 
for  its  performance  has  arisen,  he  feels  confined  and  confused. 
The  former  is  expecting  his  own  outbreak,  the  latter  is  awaiting 
the  impression ;  the  stimulus  is  in  the  one  case  the  release,  in 
the  other  the  cause  of  movement"  (Stern,  op.  cit.y  io8).  The 
subjective  observer,  then,  has  a  leaning  towards  the  *  muscular' 
form  of  reaction  ;  the  objective  tends  of  his  own  accord  to  the 
*  sensorial.'  But  as  the  conditions  of  the  experiment  require  — 
or  will  seem  to  the  unpractised  O  to  require  —  a  division  of 
attention  between  expected  stimulus  and  subsequent  move- 
ment, the  *  natural  reaction  times,'  will  probably,  in  every 
case,  be  greater  than  the  practised  muscular  and  less  than 
the  practised  sensorial.  Hence  they  have  also  received  the 
name  'central.' 

The  types  described  by  Stern  are  extreme  types,  between  which  lie  many 
forms  of  mean.  The  purely  subjective  or  objective  O  is,  as  we  saw  (p.  xxvii.), 
rarely  met  with  ;  most  O^s  are  decidedly  mixed  in  type.  It  is  '  natural,'  under 
these  circumstances,  that  the  central  form  should  tend,  as  it  does,  somewhat 
definitely  towards  the  muscular  and  away  from  the  sensorial  value.  For  O, 
unless  he  is  unusually  objective  in  type,  can  hardly  avoid  the  self-suggestion, 
favoured  by  the  very  character  of  the  experiment,  that  his  movement  is  the 
most  important  feature  in  the  case. 

Results.  —  It  is  unnecessary  to  give  an  illustrative  *  natural  * 
series.  We  may,  however,  quote  in  this  place  the  various  reac- 
tion norms. 


Sensorial. 

Muscular. 

Natural. 

Sight 

.27 

.  -23 

'   .21 

.18 
.12 
.11 

.19-.22  sec. 

.I4-.I9    " 
.I2-.18     " 

Sound  

Touch 

The  numerical  results  may  be  treated  in  two  ways,     {a)  The 
average  of  the  series  may  be  taken,  and  its  m.  v.  calculated. 


§  44-    ^^  Reaction  Norms  21/ 

Let  A  be  the  average  time,  a,  b,  ,  ,  the  separate  times,  and  n 
the  number  of  experiments.     Then 

^  ^  _  (A-a)-^{A-b)^... 

Practice  is  not  complete  until  the  m.  v.  has  fallen  as  low  as  one- 
tenth  of  the  average  time,  (b)  A  'curve  of  frequency  *  may  be 
platted.  The  abscissae  are  hundredths  of  a  second ;  the  ordinates 
vary  in  height  with  the  number  of  times  that  the  values  of  the  cor- 
responding abscissx  have  occurred  in  the  experimental  series. 

If  the  Instnictor  desires  to  follow  the  course  of  practice,  the  average  and 
m.  x:  of  each  part-series  (to  experimeDts)  should  be  taken.  But  it  will  be 
better  to  postpone  this  enquiry  to  vol.  ii. 

It  is  unnecessary,  again,  to  give  illustrative  introspections. 
Unless  C7  be  of  a  pronounced  '  type,'  the  attention  will  vary  in 
direction  for  a  little  time,  and  then  divide  between  stimulus  and 
movement,  tending  rather  (as  we  have  seen)  towards  the  move- 
ment. The  composition  of  the  motive  will  vary  in  the  same 
way,  imtil  it  settles  down  to  a  mixture  of  the  sensorial  and  the 
motor,  with  the  latter  in  the  ascendant.  The  Instructor  must 
assure  himself,  from  series  to  series,  that  O  is  not  letting  the 
experiment  become  automatic,  i.^.,  decreasing  the  degree  of 
attention.  On  the  whole,  however,  the  less  the  Instructor  in- 
terferes with  the  course  of  the  experiment,  the  better  will  it  be. 

The  introspections  will,  naturally,  be  poor.  O  has  had  no 
practice  in  the  observation  of  the  action  consciousness  ;  and  the 
present  form  of  that  consciousness,  just  by  reason  of  the  natural- 
ness and  obviousness  of  the  mode  of  reaction,  and  the  consequent 
vacillation  of  attention  and  complexity  of  motive,  is  peculiarly 
difficult  of  analysis.  The  introspections  will  improve  in  the  next 
two  experiments  ;  and  if  the  natural  reaction  be  repeated  at  their 
conclusion,  O  will  have  a  much  greater  mastery  over  his  task. 

One  point  must  be  clear  from  the  first :  the  point  that  O  is 
responsible  for  the  results  of  the^ experiment.  E  is  to  average 
or  plat  the  results.  But  O  is  to  say  whether  this  or  that  result 
shall  be  included  in  the  average,  or  thrown  out  as  a  failure.  He 
must  decide,  of  course,  without  knowing  anything  of  the  actual 
times:  neither  E  nor  O  should  see  his  times  until  the  whole 


2i8  Attention  and  Action 

experiment,  in  all  three  forms  and  in  all  three  sense-departments, 
is  completed.  O  has  a  certain  thing  to  do,  —  a  certain  con- 
sciousness to  form,  —  in  a  series  of  tests ;  and  he  is  the  sole 
judge  as  to  whether  this  thing  has  been  done.  If  his  attention 
has  relaxed,  if  intruding  ideas  have  forced  themselves  upon  the 
attention,  if  there  have  been  objective  disturbances  in  the  room 
around  him,  he  must  note  the  departure  from  the  norm,  and 
throw  out  the  experiment.  E  is  to  sacrifice  unquestioningly  the 
results  that  he  is  told  to  sacrifice,  no  matter  if  (from  the  objective 
standpoint)  they  are  'perfectly  good  ' ;  while,  on  the  other  hand, 
he  is  to  let  results  stand  that  are  obviously  *  bad  *  results,  if  O 
declares  that  they  are  warranted  by  introspection. 

It  rests  in  the  discretion  of  the  Instructor,  here  as  in  the  case  of  degree  of 
attention,  to  interfere  or  not  to  interfere,  if  he  sees  O  going  astray.  A  good 
deal  depends  upon  the  character  of  the  mistakes,  and  upon  the  time  that  can 
be  allotted  to  the  total  experiment. 

It  need  hardly  be  said  that  if  E  makes  a  mistake,  —  does  not  strike  the  key 
fairly,  lengthens  or  curtails  the  signal  period,  —  he  must  throw  out  the  par- 
ticular experiment.  O  then  leaves  a  blank  on  his  record  sheet,  and  £"  proceeds 
to  the  next  number  in  the  experimental  series.  It  need  hardly  be  said,  again, 
that  all  experiments,  the  rejected  as  well  as  the  accepted,  are  to  be  entered  in 
the  note-book. 

When  the  reaction  experiment  is  performed  upon  a  more  elaborate  plan,  it 
is  advisable  :  {a)  to  take  a  good  number  of  practice  series,  the  results  of  which 
are  not  counted ;  {b)  to  throw  out  the  first  two  experiments  of  every  series, 
no  matter  how  'good'  they  are,  —  on  the  principle  that  O  must  become 
adapted  or  *  warmed  up '  to  his  work  after  an  intermission ;  {c)  to  reduce  the 
introspective  record  to  a  set  of  simple  symbols,  so  that  the  experiments  may 
be  taken  in  quick  succession,  and  6>'s  general  disposition  may  remain  constant 
throughout  a  series  ;  and  {d)  to  extend  the  series  to  20  experiments.  All  this 
is  upon  the  assumption  that  the  object  of  the  work  is  the  synthesis  of  the 
action  consciousness,  and  not  an  investigation  into  the  nature  of  practice, 
*  warming  up,'  variation  of  disposition,  etc.  —  In  the  present  case  we  have  no 
time  for  such  elaboration,  and  must  therefore  count  in  the  results  every  time 
that  O  approves,  from  the  beginning  of  the  experiment. 

(2)    The  *  Complete'  or  'Sensorial'  Reaction. 

We  now  come  to  forms  of  reaction  in  which  a  definite  direction 
of  attention  is  prescribed.  The  instructions  to  O,  in  the  sensorial 
reaction,  will  run  somewhat  as  follows.  "  You  are  now  to  attend 
to  the  sense  impression,  the  sound.     When  the  *  Now  ! '  comes, 


$  44*    ^^^  Cow^UU  or  Sensorial  Reaction  219 

you  are  to  think  of,  and  look  out  for,  the  sound.  Let  the  move- 
ment of  your  finger  take  care  of  itself ;  it  will  follow  all  right, 
when  you  have  heard  the  sound.  And  be  sure  that  you  think 
of  M/- sound;  get  it  impressed  on  your  memory,  so  that  you 
would  not  be  tempted  to  react  to  any  other  kind  of  sound.'*  The 
Instructor  can  afford  to  slur  the  movement  in  this  way,  since  its 
association  to  the  stimulus  has  already  become  ingrained  by  the 
previous  experiments.  He  must  be  on  his  guard  that  there  is 
no  misunderstanding  as  to  the  mode  in  which  the  sound  is  to  be 
identified :  O  is  not  to  wait,  and  think  about  it,  and  ask  himself 
if  it  is  the  right  sound,  but  to  be  so  thoroughly  prepared  for  it 
that  he  identifies  it  by  direct  apprehension. 

Different  (7s  will  caiT>'  out  these  instructions  in  different  ways,  according  to 
their  *idea  t)'pes.'  One  man  will  ideate  or  image  the  sound  itself;  another 
will  keep  a  verbal  description  of  it  in  the  forefront  of  consciousness ;  another 
will  see  the  rod  striking  the  button  of  the  key,  etc.,  etc.  The  most  constant 
£iictor  is  the  group  of  strain-sensations  characteristic  of  adaptation  of  the  sense- 
organ  (p.  209  above).  See  KUlpe,  Outlines,  408;  Wundt,  Phys.  Psych.,  ii., 
316,  note. 

^s  work  is  as  before,  except  that  he  is  to  introduce  an  occa- 
sional 'puzzle  stimulus'  into  the  course  of  a  regular  series.  He 
may,  e.g.^  strike  the  table  instead  of  the  key  with  his  wooden 
rod,  or  strike  the  key  with  the  handle  of  his  pocket-knife.  \i  O 
is  rightly  disposed,  he  will  make  no  movement  in  response  to 
these  puzzle  stimuli.  If  he  reacts,  it  is  because  there  is  still  a 
*  muscular  *  ingredient  in  his  preparation  for  the  experiment : 
further  practice  is  then  needed. 

Question  (4)  See  Primer  of  Psych.,  179  f . ;  Outline,  341. 
The  Instructor  must  be  careful  (as  one  of  the  author's  students 
said)  not  "  to  make  the  motive  too  conscious  " ;  i.e.,  not  to  ex- 
aggerate the  clearness  and  discriminability  of  its  constituent 
ideas.  When  once  O  has  laid  hold  of  the  motive,  the  task  of 
introspection  is  not  especially  difficult ;  but  the  preceding  verbal 
analysis  is  apt  to  suggest  (as  another  student  put  it)  that  ••  the 
ideas  are  a  good  deal  more  dignified  than  you  actually  find  them 
to  be."  It  is  true,  as  Stumpf  says  (Tonps.,  i.,  162).  that  "  vermit- 
telnde  Vorstellungen  kbnnen  weniger  lebhaft  und  doch  uncnt- 
behrlich  sein." 


220 


Attention  and  Action 


Results. — The  following  are  typical  series. 
(i)   First  series  taken  after  the  50  'central  ^  reactions. 


Exp. 


Time. 


Introspections. 


8 
9 

10 


.32  sec. 

.34  " 

.32  « 

.22  « 

.14  « 

.12  " 

.24  « 

.23  « 

.30  " 

.20  « 


Tried  to  attend  to  the  stimulus,  but  had  a  motor  image  of 
my  own  movement.  The  stimulus  came  later,  and  was  less 
decided,  than  I  had  expected.     This  disturbed  me.  —  Bad. 

Attention  entirely  on  the  stimulus.  Had  a  visual  image  of 
my  movement  after  reacting.  —  Good. 

Attention  distracted  a  little  by  a  picture  that  E  had  sug- 
gested to  me  just  before  the  experiment.  Visual  image  of  my 
movement ;  but  consciousness  was  filled  with  the  idea  that  I 
must  move  and  move  quickly.  —  Bad. 

Attention  wholly  upon  stimulus.  Visual  image  of  my  own 
movement,  coincident  with  the  pressure  of  actual  move- 
ment. —  Good. 

Attention  on  stimulus.  Visualised  my  own  movement,  as 
before.  —  Good. 

Tried  to  attend  to  stimulus,  but  had  a  sense  of  being  forced 
to  move,  and  to  move  quickly.  As  I  moved,  thought  that  I 
pressed  harder  than  was  necessary  to  release  the  pendulum.  — 
Bad. 

Seemed  to  be  getting  more  familiar  with  the  experiment, 
and  to  realise  what  the  three  ideas  [motive  ideas]  meant. 
Attention  on  stimulus.  —  Good. 

As  before.  — Good. 

Attention  on  stimulus,  but  with  some  innervation  of  hand 
and  arm.  —  Think  it  was  good. 

Attention  on  stimulus.  No  picture  of  movement  till  I  felt 
the  pressure  of  moving  ;  then  I  found  myself  trying  to  intro- 
spect.—  Good. 


In  almost  every  case,  there  was  a  visualisation  of  the  pendulums  after  the 
movement  of  reaction  had  been  made.  In  a  few  cases  there  were  shadowy 
ideas  of  result.     References  to  adaptation  of  the  sense-organ  have  been  omitted. 

Taking  the  *good '  times  of  the  above  list,  we  have  an  average 
of  .238  sec.,  with  an  m.  v.  of  .047  sec.  This  m.  v.  is  a  great  deal 
too  high.  Looking  at  the  introspections,  we  find  that  a  con- 
sciousness which  lasts  .34  sec.  is  equated  with  a  consciousness 
which  lasts  but  .14  sec.  ;  it  is  clear  that  introspection  is  not  yet 
adequate  to  its  work.     On  the  other  hand,  O  is  capable  and 


§  44*    ^^^  Srttsorin/  Reaction :  Results 


221 


honest  as  regards  his  *  muscular  *  tendencies,  and  shows  marked 
improvement  as  the  series  progpresses. 

(a)  Fifth 


loirotpactiiMU. 


K«P^ 

TiM. 

^sec 

ai   " 

.»   ** 

.26   " 

.20   " 

.20   " 

.24   " 

.30   " 

10     ,20 

II  .22 


Visual  idea  of  apparatus,  while  waiting  for  stimulus.  Idea 
of  result :  a  little  anxious  to  make  a  good  series.  Strain  in 
finger  just  as  it  pressed  the  key ;  none  before.  —  Good. 

Auditory  idea  of  stimulus ;  idea  of  result  visual,  experiment 
done;  mood  familiar  and  of-course;  no  effort  or  strain.— 
Good. 

Idea  of  sound  as  before ;  idea  of  result  just  comfortableness 
and  of-course  mood. — Good. 

False  stimulus ;  no  tendency  to  movement,  and  no  mental 
disturbance. 

Idea  as  before.  Perhaps  a  little  hesitancy  in  getting  the 
sound,  owing  to  false  stimulus :  of-course  changed  to  careful. 
Otherwise  good. 

Sound  clearly  imaged ;  mood  of-course ;  very  smooth  re- 
action.—  Good. 

Feeling  of  non-responsibility  and  certainty.  Idea  clear.  — 
Good. 

A  little  fuller;  idea  of  result  back  again.  Otherwise  as 
before.  —  Gockl. 

Everj-thing  seemed  very  clear;  this  was  the  best  experi- 
ment so  far  for  introspection.  —  Good. 

As  7.  —  Good. 

Same.  —  Good. 


The  average  here  is  .23  sec. ;  the  nt.  v.,  .028  sec.  It  is  the  merest 
accident  that  the  average  time  equals  the  norm.  Despite  the 
result  of  exp.  4,  O  has  not  yet  entirely  overcome  his  muscular 
tendency :  this  is  proved  partly  by  the  reference  to  '  smoothness ' 
and  *  certainty  *  in  the  introspections,  the  '  smoothness '  implying 
some  degree  of  motor  preparation  ;  and  partly  by  his  later  work.  — 
References  to  adaptation  of  the  sense-organ  are  omitted. 

(3)    The  *  Abbreviated^  or  'Muscular'  Reaction. 

The  instructions  to  O,  in  the  muscular  reaction,  will  run  as 
follows.  "  You  are,  in  this  series,  to  attend  to  the  latter  part  of 
the  experiment,  your  own  movement.     You  are  to  prepare  your- 


222 


Attention  and  Action 


self  for  movement,  just  as  in  the  last  series  you  prepared  yourself 
for  the  'direct  apprehension'  of  a  sense-impression.  When  the 
*  Now  !  *  comes,'  you  are  to  be  on  the  alert  to  move.  In  the  last 
series,  you  associated  a  movement  to  the  sense-impression  ;  in 
this  series,  the  sense-impression  gives  you  the  opportunity  to 
make  a  movement  that  you  have  been  wanting  to  make  ever 
since  you  heard  the  *  Now  ! '  " 

Different  O^s  will,  again,  carry  out  these  instructions  in  different  ways. 
Miiller  (in  Pilzecker,  op.  cit.,  65)  speaks  of  a  Bewegungsbild,  a  motor  image, 
which  is  of  the  same  character  as  the  stimulus  image  in  the  sensorial  form. 
Wundt  {loc.  cit.)  finds  no  motor  image  in  the  reaction  consciousness,  but 
emphasises  the  strain-sensations  in  the  reacting  muscles :  if  he  has  an  image, 
it  is  a  faint  (presumably  visual)  image  of  the  reacting  member.  The  differ- 
ences will  appear  in  the  introspections. 

Characteristic  of  the  muscular  mode  of  reaction  is  the  occur- 
rence of  premature  and  of  erroneous  reactions.  The  reaction  is 
termed  premature  when  O  moves  his  finger  before  the  stimulus 
has  been  given  hy  E\  it  is  termed  erroneous,  when  he  reacts 
not  to  the  tap  of  the  key  but  to  some  other  accidental  stimulus. 
On  the  subjective  side,  we  find  that  O  not  infrequently  regards 
the  stimulus  and  the  answering  movement  as  simultaneous. 

On  the  composition  of  the  motive,  see  Primer,  180;  Outline,  343. 

Results.  — The  following  series  (second  taken)  is  typical. 


Exp. 

Time. 

I 

.12  sec. 

2 

.12 

« 

3 

.12 

« 

4 

.12 

u 

5 
6 

.14 

a 

7 
8 

.14 
.12 

« 

9 
10 

.10 
.08 

u 

II 

.14 

u 

Introspections. 

Strain  in  finger;  attention  on  finger.  Stimulus  came  to 
consciousness  when  I  reacted  or  even  a  little  later. 

Finger  ready  ;  attention  on  it.  Time  between  *  Now ! '  and 
pressure  seemed  long.     Relief  to  move. 

Attention  all  on  finger.  Felt  strain  go  along  arm  from 
elbow  to  finger. 

Attention  on  finger ;  but  sense  of  strain  less  prominent. 
Effort  to  direct  strain. 

Strain  in  finger,  but  attention  not  strong. 

Reacted  to  the  '  Now  ! '  without  knowing  what  I  was  doing. 

Strain  in  finger,  but  not  much  attention  to  direct  the  effort. 

Better :  strain  again  from  elbow  to  finger. 

Whole  thing  very  easy ;  not  much  strain  in  finger. 

As  last  experiment. 

More  attention  ;  but  strain  in  finger  not  prominent. 


§  44-    ^^  AbbmriaUd  or  Muscular  Reaction  233 

All  the  experiments  were  *good.*  The  average  time  here  ii  .la  tec.»  and  the 
m,x'.y  .013  sec.  The  fiitigue  of  the  first  8  experiments  has  tempted  O  into  a 
lapse  of  attention ;  experiments  9  and  10  are  getting  towards  the  reflex.  O 
recovers  himself  again  inn. 

These  and  the  foregoing  results  are  typical^  not  excellent.  In 
some  cases  the  introspections  arc  fuller  and  more  accurate ;  in 
others  they  are  more  scanty.  The  three  scries  represent  the 
average  work  that  can  be  accomplished  in  the  time  allowed. 

B,  We  have  begun  with  the  description  of  reactions  to  sound, 
because  the  vernier  chronoscopc  lends  itself  most  easily  to  sound 
work.  E  will,  doubtless,  require  some  little  practice  before  he 
can  strike  the  button  of  the  stimulus  key  with  approximately 
equal  force  throughout  an  experimental  scries ;  but  the  training 
needed  is  minimal.  Pressure  reactions,  on  the  other  hand,  in- 
troduce a  complication  on  the  side  of  O^  and  visual  reactions  a 
complication  on  the  side  of  E.  Nevertheless,  there  is  no  intrin- 
sic reason  why  all  students  should  begin  with  sound.  If  several 
pairs  are  occupied  with  reaction  work  at  the  same  time,  it  will 
be  better  to  distribute  the  experiments  evenly  over  the  three 
sense-departments.  All  the  general  directions  given  above  in 
regard  to  sound  apply  with  equal  force  to  touch  and  vision. 

Preliminaries.  —  £"  must  practice  the  'flick*  of  the  finger 
that  releases  the  key.  It  is  not  difficult  to  get  the  knack  of  a 
pressure  that  shall  be  clean-cut  and  yet  not  intensive. 

Sanford  (196)  recommends  a  different  procedure.  "  Reactions  to  touch,  or 
more  exactly  to  pressure,  may  be  tried  by  having  the  subject  place  one  fore- 
finger under  that  of  the  operator  on  the  operator's  key.  He  will  thus  receive 
a  pressure  in  it  at  the  instant  that  the  operator's  pendulum  is  released,  and  can 
release  his  own  pendulum  with  the  other  finger.''  The  author  has  found  this 
arrangement  less  satbfactory  than  that  of  the  text,  especially  in  the  case  of 
muscular  reactions. 

If  cutaneous  reactions  are  the  first  to  be  tried,  300  experimenU  should  be 
taken,  as  recommended  above  for  sound. 

C.  Preliminaries.  —  A  diagram  of  the  arrangement  for 
deadening  the  noise  of  the  key  is  given  in  Primer  of  Psych., 
185.  The  screen  must  stand  in  a  good  light;  and  the  stimu- 
lus paper  in  the  clip  must  lie  as  close  as  possible  to  the  screen 
surface. 


224  Attention  and  Action. 

Visual  reactions  may  be  taken,  without  the  screen  and  side-wire,  as  follows. 
At  the  "  Now  ! ''  O  fixates  £"'8  finger,  which  lies  upon  the  stimulus  key.  The 
movement  of  E^^  finger  is  the  visual  stimulus  to  reaction.  —  These  experiments 
are,  however,  much  less  satisfactory  than  the  others. 

Related  Experiments.  — The  simple  reaction  may  be  varied 
by  changing,  e.g.y  the  quality  or  intensity  of  the  stimulus.  Thus 
it  is  easy  to  attach  a  small  bell-gong  to  the  stimulus  key,  and  to 
release  the  pendulum  by  the  stroke  which  sounds  it.  In  visual 
reactions,  different  colours  may  be  used,  as  well  as  black  and. 
white.  The  touch  reactions  may  be  modified,  similarly,  by  sub- 
stituting a  cooled  or  heated  cylinder  for  the  rap  of  E's  finger. 
As  for  intensity  :  two  forces  of  stroke  may  be  employed,  whether 
with  the  wooden  rod  or  with  the  gong.  In  visual  reactions,  a 
grey  card  of  the  same  brightness  as  the  screen  may  be  put  in 
the  clip,  and  the  position  of  the  opening  changed,  so  that  it  is 
exposed  and  not  filled  by  the  movement  of  the  stimulus  key. 
Then  a  flash  of  sunlight  or  electric  light,  reflected  through  the 
opening  from  a  plane  mirror,  may  serve  as  stimulus.  For  touch, 
two  intensities  of  pressure,  or  of  heat  and  cold,  can  be  applied. 
In  all  these  cases,  it  is  the  central  form  of  reaction  which  is 
most  interesting.  Very  weak  stimuli,  e.g.,  evoke  a  sensorial  reac- 
tion, even  in  the  absence  of  all  directions  to  O.  Very  intensive 
sounds  may,  according  to  circumstances,  call  forth  a  short  or  a 
long  reaction  :  short,  if  O  is  muscularly  disposed ;  long,  if  he 
tends  towards  the  sensorial  type.  In  the  former  case,  the  reac- 
tion is  carried  along  on  the  current  of  the  intensive  stimulus ; 
in  the  latter,  the  attention  is  arrested,  shocked,  by  the  loudness, 
and  the  movement  is  for  a  moment  inhibited.  —  Wundt,  ii.,  344  ff. 

Still  more  interesting  is  the  course  of  the  experimental  series 
when  the  ready-signal  is  sometimes  given  and  sometimes  omitted. 
In  such  a  series  the  word  "  Ready  !  "  tells  O  that  he  is  to  lay  his 
finger  on  the  key,  and  the  word  ''Now!"  given  a  few  seconds 
later  is  (as  always)  the  ready-signal  proper,  the  call  for  attention. 
This  "  Now  !  "  is  put  in  and  left  out,  irregularly.  At  the  end  of 
the  series,  the  results  and  introspections  '  with  signal  *  are  sepa- 
rated from  those  'without  signal,*  and  the  two  part-series  com- 
pared. All  three  forms  of  reaction,  natural,  complete  and 
abbreviated,  should  be  tried.  —  Wundt,  348  f. 


§  44*    ^^  SimpU  Reaction  225 

Thirdly,  a  scries  may  be  taken  with  irregular  alternation  of 
weak  and  loud  sounds;  Wundt,  351.  The  natural  form  ot 
reaction  should  be  adopted. 

Fourthly,  reactions  may  be  taken,  with  a  constant  intensity 
of  stimulus  (auditory,  visual  or  tactual^  but  with  a  concomi- 
tant  'distracting'  stimulus;  e.g.,  the  whir  of  the  kymograph 
clock.  All  three  forms  may  be  employed.  Wundt,  353  f. — 
The  results  of  these  additional  experiments  are  of  importance 
for  a  general  theory  of  action.  But  it  is  essential  that  the  work 
outlined  in  the  text  be  thoroughly  performed,  before  they  are 
attempted. 

Question  (5)  The  norms  have  been  given  above.  The 
average  difference  is  o.  i  sec.  For  the  explanation,  see  Kiilpe, 
407  f. ;  Pilzecker,  65  f. ;  Alechsieff,  19;  Wundt,  ii.,  309,  315  f. ; 
G.  Martius,  Philos.  Studien,  vi.,  1891,  191  ff . ;  L.  Lange,  ibid.f 

,  1888,  497  ff. ;  Titchener,  Mind,  N.  S.,  i.,  1892,  220. 

.^gainst  the  sensorial-muscular  difference,  see  especially  J.  M.  Baldwin  and 
W.  J.  Shaw,  Psych.  Rev.,  ii.,  1895,  259;  J.  M.  Baldwin,  Mind,  N.  S.,  v., 
1896.  81 ;  j.  McK.  Cattell,  Philos.  Studien,  viii.,  1893,  403;  j.  McK.  Cattell 
and  C  S.  DoUey,  Memoirs  of  the  Nat.  Acad,  of  Sciences,  vii.,  1896,  409  f. ; 
Psych.  Rev.,  i.,  1894,  165 ;  T.  Flournoy,  Arch,  des  sci.  phy.  et  nat.,  xxvii., 
1892,  575;  xxviii.,  1892,  319;  Observations  sur  quelques  types  de  reaction 
siiDple,  Geneva,  1896;  J.  R.  Angell  and  A.  W.  Moore,  Psych.  Rev.,  iii.,  1896, 
245  (Univ.  of  Chicago  Contr.  to  Philos.,  i.,  i) ;  J.  R.  Angell,  ibid.^  v.  1898, 
179  (Contr.,  ii.,  2,  179).  C/.  Titchener,  Mind,  N.  S.,  iv.,  1895,  74,  506; 
v.,  iSq6,  236;  Stem,  op.  cit.,  103. 

(o;  Smell  experiments  can  be  made  as  follows.  Connect  a 
glass  thistle-tube  by  rubber  tubing  to  a  small  rubber  bulb  which 
contains  a  few  drops  of  oil  of  cloves.  Pack  a  little  loose  cotton 
wool  at  the  bottom  of  the  thistle-cup.  At  the  "Ready!"  O 
places  his  finger  on  the  key,  and  takes  the  thistle-cup  in  his  left 
hand.  At  the  "  Now !  *'  he  holds  the  cup  to  his  nose.  See  that 
the  "  Now  !  •'  falls  at  the  beginning  of  an  expiration.  Lay  the 
bulb  on  the  bottom  of  the  stimulus  key,  and,  as  inspiration 
begins,  press  bulb  and  key,  thus  releasing  the  long  pendulum. 

For  taste  experiments,  E  may  use  the  rubber  syringes  of 
r-xp.  XXIII.  The  squeeze  of  the  bulb  and  the  pressure  of  the 
key  must  be  made  as  nearly  simultaneous  as  possible. 


226  Attention  and  Action 

Neither  of  these  procedures  is  at  all  exact ;  but  taste  and  smell  reactions 
are  never  very  satisfactory.     Wundt,  317  f. 

It  remains  to  suggest  a  method  for  taking  reactions  to  pain.  A  stout  flat 
spring  is  nailed  at  one  end  to  a  cap  of  wood,  which  fits  over  the  button  of  the 
stimulus  key.  At  the  other,  free  end  of  the  spring,  a  pin  or  small  brad  is 
driven  through  the  metal.  O's  left  hand  is  so  placed  that  the  pressure  on  the 
stimulus  key  which  releases  the  long  pendulum,  brings  the  pin  or  brad  point 
sharply  down  upon  the  skin  of  the  palm. 


(7)  Within  the  limits  of  the  theory  of  action,  we  have  the 
related  experiments  cited  above,  and  the  whole  series  of  com- 
pound reactions :  Wundt,  362  ff.  If  we  regard  the  reaction 
method  simply  as  a  psychophysical  method  for  the  study  of  mind 
at  large,  we  have  to  mention  {a)  the  association  reaction  (Out- 
line, 352  ff.);  {b)  the  fusion  reaction  (351);  {c)  the  intensity- 
quality  reaction  (351).  The  method  is  also  of  value  {d)  for  the 
investigation  of  the  course  of  practice,  habituation,  expectation, 
fatigue.  Finally,  travelling  outside  of  psychology,  we  must  note 
that  physiology  has  been  interested  in  the  simple  reaction,  as  a 
means  for  the  determination  of  the  velocity  of  nervous  impulses 
(cf.y  however,  Cattell  and  Dolley,  Mem.  Nat.  Acad,  of  Sci.,  vii., 
1896,  393  ff.);  and  that  astronomy  is  similarly  interested,  seeing 
that  a  reaction  is  involved  in  the  observation  of  stellar  transits 
(Alechsieff). 

(8)  This  question  must  be  answered  from  the  introspections. 
It  will  not  be  amiss,  when  the  whole  experiment  is  completed, 
to  let  each  student  enter  in  his  note-book  {a)  the  average  time 
and  m.v.  of  all  the  (9's  in  the  class,  and  {b)  the  corresponding 
analyses  of  motive.  The  striking  uniformity  of  time  values,  and 
the  equally  striking  divergence  of  introspective  results,  are  most 
instructive.  The  former  represent  the  reaction  as  a  fundamental 
function  of  mind,  practically  identical  in  all  (9's ;  the  latter  show 
how  various  the  processes  may  be  that  carry  a  given  function. 

(9)   Outline,  350  f.     Cf.  Bentley,  Amer.  Journ.  of  Psych.,  xi., 
1900,  412. 

(10)  Primer,  181  f.,  262. 

(11)  The  practised  consciousness  is  characterised  on  the 
functional  side  by  {a)  maximal  degree  and  constant  direction  of 
attention,   with   minimal    effort   (secondary  passive   attention); 


$  44     ^^  SimpU  Reactiom  227 

(^)  ease  of  discrimination  (delicacy  of  perception);  and  (r)  high 
degree  of  capacity  of  reproduction,  implying  great  readiness  and 
confidence  of  judgment.  —  KUlpe,  Outlines,  42  f.,  212,  302  f. 
On  the  physiological  basis  of  practice,  see  Wundt,  i.,  236,  279 ; 
ii.,  473, 

It  b  well  to  remind  ounelves,  in  these  days  of  Ughtless  and  soundless  re- 
action-rooms, that  one  of  the  most  direct  efTects  of  practice  is  a  narrowing  of 
attention  to  the  practised  subject-matter.  Practice  makes  us  '  mentally  deaf* 
and  *  mentally  blind'  to  distracting  stimuli,  much  more  effectively  than  does 
the  mechanical  remov-al  of  the  grosser  distractions.  Cf,  also  the  remarks  on 
distractkm,  p.  318  above. 

Instrumsnts.  —  Another  good  and  cheap  instrument  is  H. 
Obersteiner's  Psychodometer :  L'Ann^e  psych.,  v.,  1899,  394. 
Cf.  James,  Psych.,  i.,  1890,  87. 


PART  II 

PERCEPTION   IDEA   AND    THE  ASSOCIATION  OF 

IDEAS 


>>»:c 


CHAPTER  IX 
Visual  Space  Perception 

§45.  Perception.  —  The  sketch  of  the  psychology  of  percep- 
tion given  in  the  text  differs  in  many  points  from  the  treatment 
found  in  the  psychologies.  Perception  is  ordinarily  regarded  as 
the  simplest  cognitive  function  of  the  *  real '  mind  :  **  we  cannot 
perceive  without  perceiving  something"  (Stout,  Manual  of 
Psychology,  241).  But  this  is  a  question,  partly  of  terms,  and 
partly  of  standpoint.  Would  it  not  be  as  true  (or  as  untrue)  to 
say  :  we  cannot  sense  without  sensing  something }  It  all  de- 
pends (i)  upon  what  you  mean  by  'sensing'  and  'perceiving,' 
and  (2)  upon  the  point  of  view  from  which  you  wish  to  consider 
sensation  and  perception. 

We  are  concerned,  in  the  laboratory,  not  with  the  'objective 
reference'  of  perception,  not  with  perception  as  meaning  'the 
direct  cognition  of  present  objects,'  but  with  the  perception 
viewed  as  mental  stuff,  arranged  by  nature,  modified  in  the 
course  of  natural  evolution. ^  What  sense-material  have  we  in 
it }     Under  what  general  type  of  connection  may  the  plan  or 

^  It  is  a  pity  that  we  have  no  words  but  '  perception '  and  *  percept,'  words  sur- 
charged with  functional  meaning,  for  laboratory  use.  If  we  borrow  from  geometry 
the  term  *  connex '  ("  any  mixed  form  consisting  partly  of  points  and  partly  of  lines, 
or  of  other  diverse  elements  " :  Century  Diet.),  we  might  speak  of  '  sense  connexes ' 
in  place  of  *  perceptions.' 

228 


§  45-    T^^f  Problem  of  Pfraptum  229 

pattern   of   this   material   be  classified?     What   substitutions, 
reil  net  ions,  transpositions,  has  the  material  undergone  ? 

I  would  seem,  at  first  sight,  that  the  easiest  perceptions  to 
begin  with  are  those  technically  known  as  'qualitative  percep- 
tions * :  complexes  like  lemonade,  or  a  chord  in  music.  In 
them,  sensations  are  put  together  as  qualities,  not  as  intensities 
or  extents  or  durations,  so  that  qualitative  analysis  is,  so  to 
speak,  upon  its  own  ground.  Moreover,  such  perceptions  are 
far  less  liable  to  change  than  spatial  and  temporal  perceptions 
are.  Quality  is  the  absolute,  permanent  attribute  of  sensation  : 
intensity  and  extent  and  duration  are  relative,  constantly  chang- 
ing. Lemonade  and  the  common  chord  are  the  same  for  me, 
the  same  conscious  stuff,  as  they  are  for  a  child  of  two ;  but  my 
spatial  and  temporal  perceptions  are  different  from  the  child's. 

Nevertheless,  it  is  better,  in  the  present  state  of  psychology, 
to  begin  elsewhere.  One  qualitative  perception,  the  tonal  fusion, 
has  received  thorough  investigation  in  Stumpfs  Tonpsychologie 
'vol.  ii.,  1890).  Unfortunately,  however,  the  psychology  of  work 
;  this  subject  demands  a  good  deal  of  preliminary  physical 
knowledge,  and  accurate  and  expensive  instruments.  The  other 
qualitative  perceptions,  smell  and  taste  fusions  and  organic 
complexes,  are  as  yet  hardly  known  at  all  in  detail.  So  that, 
while  theoretically  the  qualitative  perception  is  the  easiest  to 
start  with,  it  is  not  the  easiest  to  begin  upon  in  laboratory 
practice. 

For  the  rest,  the  psychology  of  perception,  in  any  form,  is  a 
good  deal  more  difficult  for  O  than  the  psychology  of  sensation, 
and  would  be  more  difficult  for  £",  also,  were  we  to  leave  the 
beaten  track  of  experimentation.  Illustrations  are  not  far  to 
seek.  Although  ten  years  have  elapsed  since  the  publication  of 
Stumpfs  monograph,  in  which,  as  we  have  said,  *  tonal  fusion 
has  received  thorough  investigation,'  yet  there  is  still  wide 
difference  of  opinion  as  to  his  results,  as  to  choice  of  methods, 
and  as  to  the  relative  value  for  research  of  musical  and  un- 
musical persons,  while  there  is  scarcely  a  suggestion  of  a  true 
theory*  of  the  tonal  fusion,  i.e.,  a  definite  statement  of  the 
proximate  conditions  under  which  it  is  realised.  Space  theories 
have  ranged  between  almost  polar  opposites ;  and  we  are  only 


230  Visual  Space  Perception 

now  beginning  to  have  a  theory  of  the  time  perception.  All 
this  means  that  the  task  set  to  introspection  is  immensely  diffi- 
cult ;  and  actual  investigation  soon  reveals  the  fact  that  the 
difficulty  is  twofold,  intrinsic  and  genetic.  Sensations  that 
our  physical  environment  has  joined  together  are  hard  to  put 
asunder;  and  sensations  that  were  joined  together  in  times 
when  the  organism  was  still  plastic  are  hard  even  to  recognise. 

Let  us  look  at  some  instances. 

(i)  Wundt's  *  genetic'  theory  of  space  perception  holds  that 
"the  spatial  order  is  developed  from  the  connection  of  certain 
sensation  components,  which  taken  separately  have  no  spatial 
attributes  whatsoever "  (Outlines,  127;  Grundriss,  150).  Visual 
space  perception,  e.g.,  is  the  resultant  of  retinal  sensations  mul- 
tiplied into  (if  we  may  use  the  phrase)  the  sensations  set  up 
by  eye  movements.  "  The  attributes  of  mental  complexes  are 
never  limited  to  those  of  the  mental  elements  that  enter  into 
them  ;  new  attributes,  peculiar  to  the  complexes  as  such,  always 
arise  as  the  result  of  the  connection  of  the  elements.  Thus,  a 
visual  idea  has  not  only  the  attributes  of  the  visual  sensations, 
and  of  the  sensations  from  ocular  position  and  movement,  which 
are  contained  in  it,  but  also  that  of  the  spatial  arrangement  of 
the  sensations,  which  these  elements  as  such  do  not  possess  " 
(Outlines,  91  ;  Grundriss,  107).  The  equation,  in  principle, — 
narrowed  down  for  simplicity's  sake,  — is  : 

Visual  sensation  (varies  Articular  sensation  

in  intensity  and  quality)    ^    (varies  in  intensity)  ^ 

In   criticism   of   this   theory,   we   have   the   following   to   say. 

(a)  When  we  dissect  the  adult  space  consciousness,  we  find 
that  the  attribute  of  extent,  spread-outness,  cannot  be  divorced 
from  the  visual  and  cutaneous  sensations.  Extent,  the  logically 
simplest  spatial  determination,  is  given  directly  with  a  blue  or  a 
pressure.     We  cannot,  by  analysis,  go  behind  this  given  fact. 

(b)  But  the  logically  simplest  is  not  necessarily  the  earliest  in 
genesis.  An  amorphous  tissue,  in  the  animal  body,  may  be 
primitive,  but  it  may  also  be  the  final  product  of  a  long  series 
of  structural  changes.  Hence  we  may  not  argue  that  because 
extent  is  now  a  sensation  attribute,  it  has  been  a  given  charac- 


{  45-    ^^  ProbUm  of  Perciftion  231 

teristic  of  mental  process  from  the  very  beginning.  We  must 
keep  our  analysis  and  our  genesis  distinct,  (r)  Having  entered 
this  caveatt  we  are  bound  (so  it  seems  to  the  author)  to  accept 
the  equation.  We  must  take  our  two  sensation  series,  and  try  to 
find  out  precisely  under  what  conditions  of  connection  the  space 
perception  arises,  and  how  it  varies  with  variation  of  these  con- 
ditions. 7*his  is  the  second  part  of  our  space  problem,  as 
analysis  is  the  first.  (</)  We  must  not,  however,  put  an  imme- 
diate genetic  interpretation  upon  an  equation  whose  terms  are 
analytical.  The  'visual*  sensations  and  'articular' sensations 
whose  fusion  is  space  are  not  oiir  vi.sual  and  our  articular  sensa- 
tions, but  their  primitive  equivalents  or  representatives.  The 
reconstruction  of  these  is  the  third  part  of  the  space  problem. 

(2)  Stumpf  prefaces  his  theory  of  tonal  fusion  by  a  consider- 
ation of  all  the  possible  psychological  conditions.  Fusion  may 
be  the  expression  of  some  general  law  of  the  interaction  of 
ideas ;  it  may  depend  upon  the  similarity  of  the  fusing  sensa- 
tions ;  it  may  be  due  to  the  mixture  of  concomitant  feelings,  or 
to  the  degree  of  smoothness  (relative  freedom  from  beats)  of 
the  component  sensations  ;  it  may  result  from  the  frequency  of 
their  juxtaposition  in  consciousness  (Tonpsychologie,  ii.,  184- 
2II)l  All  these  possibilities  are  discussed,  and  found  wanting. 
Hence  the  condition  of  fusion  must  be  physiological ;  and  a 
further  examination  of  possibilities  leads  to  the  idea  of  specific 
synergies  of  the  cerebral  cortex.  A  specific  synergy  is  a 
"determinate  mode  of  cooperation  of  two  nervous  structures, 
having  its  ground  in  the  structure  of  the  brain,  of  such  a  kind 
that  whenever  the  two  structures  give  rise  to  their  correspond- 
ing sensations  there  arises  at  the  same  time  a  determinate  degree 
of  fusion  of  these  sensations"  (p.  214;  cf.  Beitr.,  i.,  50  ff.). 

Not  much  more  can  be  said  of  this  synergy.  But  though  we 
arc  to  prefer  "honest  poverty  to  suspicious  wealth,"  the  ques- 
tion of  tonal  fusion  cannot  be  left  here.  Stumpf  is  impelled  to 
write  a  further  paragraph  upon  the  "generic  development  of 
fusions."  The  physiological  mechanism  of  synergy,  connate 
with  the  individual,  may  have  been  acquired  in  the  course  of 
generations,  and  perhaps  the  influences  under  which  it  took 
shape  may  have  been  in  part  mental  influences.     Impressions 


232  Visual  Space  Perception 

that  affect  the  sense-organ  together,  with  relative  frequency, 
might  gradually  set  up  a  cortical  disposition  to  conscious  fusion; 
and  our  ancestors  might  be  led  by  pleasure,  by  some  purpose, 
by  one  mental  motive  or  another,  to  subject  themselves  to  im- 
pressions of  this  natural  frequency  of  coincidence.  The  fact  of 
fusion,  as  we  know  it  now,  would  thus  depend  indirectly  upon 
mental  influences  (p.  215).  Stumpf  even  proceeds  to  make  his 
ideas  concrete,  picturing,  e.g.,  primitive  man  and  woman  as 
uttering  signal-calls  at  different  pitches  (pp.  215  ff . ;  cf.  the 
parallel  thought,  as  regards  the  origin  of  our  feeling  for  the 
purity  of  musical  intervals,  in  the  Zeits.  f.  Psych.,  xviii.,  394). 

Stumpf  himself  calls  these  suggestions  **  vague  conjectures," 
hypotheses  that  contain  "too  many  part-hypotheses  which  we 
have  at  present  no  means  of  checking,"  rather  speculations 
than  even  hypotheses  (p.  218).  But  the  important  point  is 
that,  though  they  are  vague  suggestions,  and  though  we  have 
no  means  of  testing  them,  the  writer  still  feels  it  necessary  to 
venture  upon  them ;  his  psychology  of  fusion  would  not  be 
complete  if  they  were  Omitted.  The  instance  shows  with 
great  clearness  how  essential  the  third  part  of  our  perception 
problem  is  to  the  problem  of  perception  at  large. 

§  46.  Visual  Space  Perception :  Preliminary  Exercises.  —  It  is 
hardly  necessary  to  say  that  the  Questions  and  Exercises  of  this 
Section  may  be  extended  by  the  Instructor  to  far  greater  length. 
The  author  has  given  merely  the  essentials  of  the  subject : 
things  that  must  be  known,  and  the  knowing  of  which  implies 
a  general  familiarity  with  the  structure  and  function  of  the  eye 
as  a  'space  organ.' 

( i)  The  Reduced  Eye.  —  The  first  complete  reduction  is  given 
by  J.  B.  Listing  (i 808-1 882),  in  the  article  Dioptrik  des  Auges 
(Mathematische  Discussion  des  Ganges  der  Lichtstrahlen  im 
Auge),  printed  in  Wagner's  Handworterbuch  der  Physiologic, 
iv.,  1853,  451  ff.  (esp.  485-496).  Listing  proceeds  to  the  're- 
duced '  by  way  of  the  '  schematic '  eye,  a  system  with  six  cardi- 
nal points,  figured  on  p.  492.  The  student  should  consult  this 
article,  if  it  is  available. 

Consult  also :  Helmholtz,  Physiologische  Optik,  2d  edn.,  5, 
85  ff.  (esp.  89  f.),  140;  Aubert.  Physiol.  Optik,  441  f.  ;  Pick,  in 


{  4^    The  Reduced  Eye  and  the  Retinal  Image        233 

Hermann^s  Handbuch  dcr  Physiologic,  iii.,  1,61  ff. ;  Foster,  A 
Text-book  of  Physiology,  iv.,  1891,  1144-1148;  Waller,  An  In- 
troduction to  Human  Physiology,  411  f.,  424. 

Questions. — The  Questions  of  this  Section  arc  not  based 
upon  the  statements  of  the  text ;  they  are  rather  questions,  the 
answers  to  which  must  be  presupposed  if  the  text  is  to  be  fully 
understood.  The  student  should  read  the  text,  getting  what  he 
can  from  it,  —  the  amount  will  vary  with  his  knowledge  of 
physiology,  —  then  proceed  to  the  Questions,  and  then  reread 
the  text  in  the  light  of  his  answers.  The  Instructor  can  assist 
very  largely  by  means  of  lectures  and  prepared  diagrams. 

(i)  Remember  that  the  first  Table  must  include  distances 
along  the  optical  axis  of  the  system,  and  the  second  the  radius 
of  curvature  of  the  ideal  surface.  The  values  should  be  given 
accurately,  not  in  round  numbers  as  in  the  text. 

(2)  'Optic  axis*  here  means  the  optical  axis  of  the  eye:  the 
straight  line  drawn  through  the  centres  of  curvature  of  cornea 
and  lens,  and  prolonged  to  meet  the  retina  between  the  yellow 
spot  and  the  place  of  entry  of  the  optic  nerve. 

(2)  The  Formation  of  the  Retinal  Image.  —  There  may  be 
students  who  are  troubled  by  the  inversion  of  the  retinal  image. 
The  difficulty  is  imaginary,  and  should  be  somewhat  summarily 
dismissed.  Cf.  the  author's  Outline  of  Psychology,  177  f. ; 
VVundt,  Human  and  Animal  Psychology,  Lect.  x.,  §  5  ;  Foster, 
Physiology,  iv.,  1216  f. 

On  the  retinal  image  in  general  consult :  Helmholtz,  Physiol. 
Optik,  85  ff.,  109  f. ;  Wundt,  Physiol.  Psych.,  4th  ed.,  ii.,  98  f., 
106  f. ;  Foster,  Physiology,  1149  f. ;  Waller,  Human  Physiology, 
413  f.,  419  f. 

Questions.  — (3),  (4).     See  references  above. 

(5)  Optic  axis,  Helmholtz,  90  f.,  108  f. ;  line  of  vision,  Wundt, 
99;  of  regard,  99;  principal  sighting  line,  106. 

(6)  Helmholtz  gives  the  following  methods,  (a)  Cut  away 
the  sclerotic  and  choroid  coats  of  a  freshly  removed  eye,  leaving 
the  retina  intact.  Look  through  the  eye,  from  behind,  at  some 
bright  object.  The  image  is  "small,  bright,  distinct,  and  in- 
verted." (b)  Geriing's  method.  Remove  the  retinal  elements 
with  a  fine  brush,  and  insert  a  glass  or  mica  plate  in  the  opening. 


234  Visual  Space  Perception 

(c)  Remove  the  eye  of  a  white  rabbit,  and  observe  as  in  {a). 
[This  is  the  most  available  method  :  it  has  been  worked  out  by 
San  ford  (Lab.  Course,  exp.  104,  p.  89).  The  outer  coats  need 
not  be  cut  away.  The  eye  is  mounted  in  a  clay  ring,  for  con- 
venience of  handling.  Sanford  remarks  that  images  of  distant 
objects  are  clearer  than  those  of  near  objects :  the  dead  eye  is 
adjusted  for  distant  vision.  This  is  a  matter  of  accommodation  : 
cf.  Helmholtz,  Physiol.  Optik,  144.  He  recommends,  further, 
that  convex  and  concave  spectacle-glasses  be  brought  before  the 
rabbit's  eye  and  the  eye  of  the  observer,  and  the  similarity  of 
effect  in  the  two  cases  noted.]  {d)  Volkmann's  method.  Se- 
lect as  subject  a  blonde,  blue-eyed  individual,  with  somewhat 
projecting  eyes.  Seat  him  in  the  dark  room.  Let  him  turn  his 
eyes  as  far  as  possible  to  the  right,  so  that  the  cornea  of  the 
right  eye  occupies  the  outer  angle  of  the  eyelids.  The  normal 
eye  turns  readily  outward  through  an  angle  of  40°  ;  Helmholtz 
found  that  he  could  turn  with  effort  through  an  angle  of  50° 
(Physiol.  Optik,  615  ;  ^  Hering,  in  Hermann's  Hdbch.,  iii.,  i, 
442  f.).  Now  hold  a  lighted  candle  (or  set  some  other  source  of 
light)  on  the  subject's  right,  at  an  angle  of  80°  to  85°.  Stand- 
ing before  him,  you  see  the  inverted  retinal  image  of  the  flame, 
through  the  investing  coats  of  the  eyeball,  near  the  inner  angle 
of  the  right  eyelids,  {e)  Ophthalmoscopic  observation  of  the 
retina.  —  Physiol.  Optik,  85  f. 

(7)  When  we  take  into  account  the  range,  quickness  and 
accuracy  of  eye  movements,  we  must  consider  it  an  advan- 
tage, for  *  concentration  of  attention,*  that  all  parts  of  the 
field  of  vision  are  not  seen  by  the  resting  eye  with  equal 
distinctness.  Cf.  Wundt's  psychophysical  law  of  the  *  cor- 
respondence of  apperception  and  fixation,'  Phys.  Psych.,  ii., 
121  f. 

(3)  The  Mechanism  of  Accommodation.  —  For  detailed  treat- 
ment of  this  question,  see  Helmholtz,  Physiol.  Optik,  1 12-156; 
Foster,  Physiology,   1151-1158,  11 68-1 184. 

Questions.  —  (8)   See  Helmholtz,  134;  Foster,  11 70. 

(9)  The  images  of  reflection  on  the  anterior  and  posterior 
surfaces  of  the  lens  were  discovered  by  the  Austrian  physiolo- 
gist  J.   E.   Purkinje   (1787- 1869),  and  described    in  his  tract 


$  4^.    Tk€  Mechanism  of  Accommodation  23s 

De  examine  physiologico  organi  visus  et  systematis  cutanei, 
1823.  They  were  employed  for  diagnostic  purposes  by  the 
French  surgeon  L.  J.  Sanson  (i  790-1 841  ;  Lemons  sur  les 
maladies  des  yeux»  1837),  and  are  now  generally  known  by  his 
name. 

The  essentials  of  the  experiment  are  as  follows.  The  subject 
sits  in  a  dark  room,  from  which  all  light  but  that  of  the  experi- 
menter's candle  is  excluded.  One  eye  is  closed  by  a  bandage. 
A  far  and  a  near  fixation-point  are  marked  (say,  at  30  and  at  300 
cm.)  along  the  line  of  vision  of  the  open  eye.  In  front  of  this 
eye,  to  one  side  and  upon  the  same  level,  is  placed  the  candle 
flame ;  the  experimenter,  who  is  observing  the  eye,  sits  on  the 
other  side  of  the  subject,  in  such  a  position  that  the  angle  ESf 
b  approximately  equal  to  the  angle  CSf.  After  a  little  shifting 
of  the  eyes  to  and  fro  about  the  point  E,  the  experimenter  will 

a. 

N 
X 

' *~7^ 


Fte.45. — Helmholtz,  Phyt.  Optik,  1896,  132.     £",  experimenter;  .S*,  tttbject; 
C,  candle;  »,  near;  /  far. 


see  three  reflected  images  of  the  flame  in  the  eye  5.  The  first 
(nearest  the  light)  is  very  bright ;  it  is  an  erect,  virtual  image 
from  the  convex  surface  of  the  cornea.  The  middle  image  is 
that  reflected  from  the  less  convex  anterior  surface  of  the  lens  : 
an  erect,  virtual  image,  larger  than  the  corneal,  and  apparently 
situated  some  8  to  12  mm.  behind  the  centre  of  the  pupil.  This 
image  is  very  indistinct  ("more  like  a  light  cloud  than  an 
image,**  as  Sanford  remarks:  Lab.  Course,  94),  and  owing  to 
its  position  is  easily  lost  with  any  shift  of  C  or  E.  The  third 
image,  lying  on  the  nearer  edge  of  the  pupil,  at  an  apparent 
depth  of  I  mm.,  is  reflected  from  the  concave  posterior  surface 


236 


Visual  Space  Perception 


Fig.  46.  —  Sanson's  images 
(Helmholtz,  132).  rt,  cor- 
neal image;  <^,  image  of  an- 
terior lens-surface ;  r,  image 
of  posterior  lens-surface. 


of  the  lens ;  it  is  a  real,  inverted  image,  visible  as  a  small  spot 
of  brightish  light. 

When  the  subject  accommodates  for  the  near  point,  the  mid- 
dle image  becomes  smaller,  and  ap- 
proaches the  corneal  image ;  when  he 
accommodates  for  the  far  point,  it  grows 
larger  again,  and  retires  from  the  corneal 
image.  No  change  at  all  is  observable 
in  the  corneal  image  itself ;  and  none,  or 
hardly  any,  in  the  image  from  the  pos- 
terior surface  of  the  lens.  It  follows 
(from  the  laws  of  reflection  in  convex  mir- 
rors :  Helmholtz,  133)  that  the  essential 
thing  in  accommodation  is  the  change  in 
convexity  of  the  anterior  surface.  — 
This  is  the  experiment  in  the  rough.  The  observations  are 
easier  to  make,  and  more  striking,  if  two  images  are  reflected 
from  each  surface  ;  since  in  that 
case  the  two  middle  images  ap- 
proach each  other  at  the  same 
time  that  they  grow  smaller. 
We  may  employ  for  this  purpose 
a  vertical  screen  with  two  win- 
dows, behind  each  of  which 
stands  a  lamp  or  candle  (Helm- 
holtz, 132);  or  a  single  flame 
and  a  horizontal  mirror  {ibid.)\ 
or  Helmholtz'  phacoscope  (Gk. 
<t>aK6^,  lentil,  lens,  and  cr/coTrelv^ 
to  view).  The  arrangement  of 
the  experiment  should  be  left, 
as  far  as  possible,  to  the  in- 
genuity of  the  students.  Good 
diagrams  will  be  found  in  Au- 
bert,  Physiol.  Optik,  444;   cf. 

Sanf Ord,  94.  F^^-  47-  —  Phacoscope. 

(10)   Scheiner's  experiment  is  so  named  from  the  Jesuit  Rec- 
tor C.  Scheiner( 1 579-1650),  who  published  in  16 19  his  treatise  : 


5 


0 


{  46.    The  Mtchanism  of  Accammodatiam  237 

Oculus  sive  fundamentum  opticum,  in  quo  radius  visualis  erui- 
tur,  sivc  visionis  in  oculo  scdcs  cernitur  ct  anguli  visorii  ingeniura 
rcpcritur.  It  is  interesting  for  three  reasons.  It  brings  the 
mechanism  of  accommodation  into  direct  comparison  with  the 
action  of  the  lenses  and  screens  that  we  are  familiar  with  in 
optical  instruments;  it  illustrates  the  laws  of  double  images 
seen  by  a  single  eye ;  and  it  emphasises  in  an  instructive  way 
the  fact  of  the  inversion  of  the  retinal  image.  It  is  performed 
as  follows. 

Prick  in  a  card  two  fine,  smooth  holes,  i  mm.  (or  any  distance 
less  than  the  diameter  of  the  pupil)  apart.  Mount  two  white 
pins  on  corks. 

O  sits  with  his  back  to  a 
window ;  one  eye  is  band- 
aged. A  black  cloth  screen 
stands  on  the  table  before 
him,  some  75  cm.  away. 
The  card  is  held  up  close  to 
the  open  eye,  the  pin-holes 

horizontal.     The  white  pins 

,  ^1      !•  t      Fig.  48.  —  Phacotcopic  imaffct.    A,  far  fixa- 

are  set  up  along  the  hne  of       ^j^^.  ^ „^„ ^J^^  j^*^  ^^ „ i„  ^j^  ^^ 
vision,  at  distances  of  20  and        Hcimholtz,  133. 
50cm.  respectively.  If,  now, 

he  looks  at  either  pin,  it  is  seen  single  and  sharply  outlined.  But 
if  he  looks  at  the  nearer  pin,  the  farther  pin  is  indistinct  and 
double ;  and  if  he  looks  at  the  farther,  the  nearer  is  indistinct 
and  double.  Moreover :  if  one  of  the  pin-holes  be  covered  (by 
another  card,  or  by  a  finger)  while  either  pin  is  being  fixated, 
there  is  no  change  in  the  image  of  that  pin  :  the  whole  field  is 
simply  made  somewhat  darker.  There  is  a  change,  however,  in 
the  double  images  of  the  pin  which  is  not  fixated.  If  O  looks 
at  the  nearer  pin,  and  the  left  pin-hole  is  covered,  the  left-hand 
single  image  of  the  farther  pin  disappears.  The  double  images 
are  same-sided,  or  *  uncrossed.'  If,  on  the  other  hand,  he  looks 
at  the  farther  pin,  and  the  left  pin-hole  is  covered,  the  right-hand 
single  image  of  the  nearer  pin  disappears.  The  double  images 
in  this  case  are  different-sided,  or  '  crossed.* 

The  same  experiment  may  be  tried,  in  diffuse  light,  with  a 


A  B 

w  ft 

III  I          I          I 

.11  I                    I 


238 


Visual  Space  Perception 


white  screen  and  black  pins  (small  shawl  pins) ;  with  the  pins 
placed  horizontally,  and  the  pin-holes  vertical ;  and  with  three 
pin-holes  instead  of  two.  The  shifting  of  the  three  images, 
with  differences  of  arrangement  of  the  three  pin-holes,  should 
be  recorded  and  explained. 

The  results  of  the  experiment  are  explained  by  the  accom- 
panying diagram.  A  biconvex  lens  b  receives  from  the  luminous 
point  a  two  pencils  of  rays  which  pass  through  the  openings  e, 
f  of  an  opaque  screen.  The  rays  come  together  at  the  point  c 
of  the  screen  nn.  We  may,  now,  regard  the  lens  b  as  the  refrac- 
tive medium  of  the  reduced  eye,  the  anterior  screen  ef  as  the 
card  held  before  the  pupil,  and  the  posterior  screen  nn  as  the 
retina.     The  diagram  will  then  represent  Scheiner's  experiment 


Fig.  49.  —  Helmholtz,  1 1 7. 


with  the  eye  either  in  horizontal  or  in  vertical  section.  In  the 
former  case,  ^  is  a  transverse  section  of  the  vertical  pin,  and 
the  holes  ^,  f  are  horizontal ;  in  the  latter,  ^  is  a  transverse 
section  of  the  horizontal  pin,  and  the  holes  e^f  are  vertical.  If 
the  eye  is  accommodated  for  a,  the  needle  is  imaged  clearly  and 
singly  at  c.  If  it  is  accommodated  for  a  point  beyond  ^,  the 
retina  (so  to  speak)  moves  forward  to  some  such  plane  as  m7n. 
We  have  two  dispersion  images  of  a.  If,  finally,  it  is  accommo- 
dated for  a  nearer  point,  the  retina  moves  back  to  //;  and  we 
have  again  two  dispersion  images. 

There  is,  however,  an  apparent  discrepancy.  If  we  cover  the 
hole  e,  and  the  retina  is  at  mm  (far  fixation),  we  cut  off  in  the 
diagram  the  pencil  /,  whereas  we  cut  off  in  the  experiment 
the  opposite  single  image.     Conversely,  if   the  retina  is  at  // 


§  4^.    Errors  of  Optical  Systems  239 

(near  fixation),  we  cut  off  in  the  diagram  the  pencil  q,  whereas 

we  cut  off  in  the  experiment  the  same-sided  single  image.  The 
ontradiction  disappears  when  we  remember  that  the  retinal 
nage  is  inverted.  An  image  /  (above  or  to  the  right)  must 
ome  from  a  point  in  objective  space  /*,  below  or  to  the  left; 

and  so  with  q  and  Q.  —  See  Helmholtz,   1 1 7.     Good  diagrams 

are  in  Waller,  421  f . ;  Sanford,  91. 
(11)  The  following  errors  may  be  noted  : 


(a)  Faulty  Centiring.  —  The  lenses  of  the  instrument  may  be  of  good 
quality*  but  may  be  badly  centred,  so  that  the  refracting  surfaces  do  not  lie 
truly  about  the  optical  axis  of  the  system. 

Observation  of  Sanson's  images  shows  that  the  eye  has  thb  defect: 
Helmhoha,  108  f. ;  Fick.  60.  The  proof  is,  theoretically,  very  simple, 
and  may  well  occur  to  a  student  who  has  been  interested  in  Question  (9) 
above. 

{b)  Ckromatk  Aberration.  —  In  good  optical  instruments,  the  lenses  are 
*  achromatic' or  *apochromatic,'  />.,  have  been  corrected  for  chromatic  aberra- 
on.  This  is  not  the  case  with  the  eye.  The  violet  focus  lies  nearer  to  the 
lens  than  the  red. 

There  are  three  chief  reasons  why  we  do  not  notice  chromatic  aberration 
in  ordinary  vision.  The  refracting  medium  of  the  eye  is  water  [see  above, 
under  (i)],  not  glass :  in  the  light  by  which  the  eye  is  ordinarily  affected,  the 
red  and  violet  (least  and  most  refrangible)  rays  are  intrinsically  weak,  while 
at  the  same  time  their  light  is  distributed  over  larger  dispersion  circles ;  and 
the  iris  cuts  off  peripheral  rays.  To  these  may  be  added,  in  the  case  of  those 
who  wear  glasses,  the  long  focal  distance  of  spectacle  lenses.  We  can,  how- 
ever, easily  assure  ourselves  of  the  existence  of  this  defect  in  the  eye.  —  Helm- 
holtz, 157,  164;  Fick,  loi ;  Suter,  Handbook  of  Optics,  29. 

a.  The  classical  experiment  is  performed  as  follows.  Set  up  in  front  of  a 
lamp  flame  a  black  screen,  having  a  narrow  slit,  behind  which  is  lixed  a 
piece  of  cobalt-blue  glass.  Red  and  violet  rays  come  through  the  glass 
to  the  observing  eye.  Accommodate  for  a  point  behind  the  spot  of  light, 
and  yoo  see  a  red  spot  with  violet  halo;  accommodate  for  a  nearer  point, 
and  you  see  a  violet  spot  with  a  red  halo.  Find  the  point  at  which  the 
violet  rap  converge  as  far  before  the  retina  as  the  red  converge  behind 
it,  /./.,  the  point  at  which  the  spot  appears  uniform  in  colour.  —  Helmholtz, 
158  f. 

/?.  Paste  a  small  square  or  circle  of  white  paper  upon  a  ground  of  dead 
black  cardboard.  Accommodate  for  a  point  behind  the  figure,  and  the  margin 
:s  tinged  with  reddish-yellow;  accommodate  for  a  point  before  it,  and  the 
margin  is  tinged  with  blue.  Accommodate  for  the  margin,  and  there  is  no 
ooloarcd  fringe. 


240  Visual  Space  Perception 

With  the  eye  thus  accommodated,  bring  a  card  close  before  it,  to  cover 
about  half  the  pupil.  If  the  card  comes  from  the  black  side  of  the  margin^ 
there  is  a  yellow  fringe ;  if  it  comes  from  the  white  side,  a  blue  fringe.  — 
Helmholtz,  159  f. 

y.  The  phenomena  (mixed  with  those  of  irregular  astigmatism)  are  shown 
with  astonishing  vividness  by  the  accompanying  diagrams.  Walk  backwards 
from  the  larger  figure,  so  that  it  comes  to  lie  farther  and  farther  beyond  the 
range  of  exact  accommodation.  Bring  the  smaller  figure  in  towards  the  eye, 
until  it  is  too  close  for  exact  accommodation.  Give  a  precise  description  of 
the  colours  seen.  —  The  figures  were  devised  by  W.  von  Bezold,  professor 
of  physics  and  meteorology  at  Beriin  (b.  1837).  See  Arch.  f.  Ophthalmolo- 
gic, 1868;  Helmholtz,  162;  cf.  Sanford,  exp.  109. 

{c)  Spherical  Aberration:  Monochromatic  Aberration,  Astigfnatism . — a. 
In  good  optical  instruments,  the  lenses  are  *  aplanatic,'  i.e.,  have  been  corrected 
for  spherical  aberration.  This  is  not  the  case  in  the  eye.  Spherical  aberration 
could,  however,  play  but  little  part  in  vision :  partly,  because  the  iris  cuts  off 

peripheral  rays  ;  partly,  because  the 
lens  is  not  a  homogeneous  refract- 
ing medium,  but  is  composed  of 
layers  increasing  in  density,  and 
therefore  in  refracting  index  from 
outer  surface  to  centre,  —  a  com- 
plexity of  structure  which  cannot,  of 
course,  in  itself  be  regarded  other- 
wise than  as  a  defect  of  the  optical 
system  of  the  eye.  —  Suter,  28,  64. 


Fig.  50.  —  Helmholtz,  162. 

/S.  If,  however,  there  is  no  appreciable  spherical  aberration  in  the  eye, 
there  is  a  marked  degree  of  deviation  asymmetrical  to  the  optic  axis  (irregu- 
lar astigmatism),  which  would  not  be  found  in  a  well-made  optical  instrument. 
Prick  a  fine  pin-hole  in  a  black  cardboard  screen,  and  look  through  it  at  a 
bright  white  surface.  Set  the  pin-hole,  first,  beyond  the  point  of  distinct 
accommodation  (using  a  convex  spectacle-lens  if  necessary),  and,  secondly, 
at  a  point  nearer  than  that  for  which  the  eye  is  accommodated  (using  a  weak 
concave  lens  if  necessary) .  Draw  and  colour  the  dispersion  images  obtained 
in  the  two  eyes.  —  Helmholtz,  170. 

y.  There  is,  further,  a  very  grave  defect  which  is  found  in  some  measure  in 
almost  every  eye,  —  the  aberration  known  as  regular  astigmatism.     It  may  be 


{  4^    Errwrs  of  Optical  Systems 


241 


ooaakHied  cither  by  difference  of  the  dirvature  of  the  refracting  turiacet  in 
different  directions,  or  by  finulty  centering  of  spherical  sur&ces.  We  know 
thaithe  eye  is  badly  centred  ;  and  it  has  been  found,  also,  that  sections  of 
the  refracting  media  through  the  vertical  and  horiiontal  meridians  show  dif- 
ferent radii  of  curvature.  The  cornea,  especially,  b  apt  to  present  a  toric,  not 
a  spherical  surfiKe. 

The  commoner  case  b  that  the  curvature  of  the  vertical  meridian  of  the 
cornea  b  greater  than  that  of  the  horisontal.  In  thb  event,  accommodation 
for  a  horisontal  line  means  under-accommodation  for  a  vertical,  and  vice  7>frsa, 
Either  line  can  be  seen  distinctly  by  itself,  but  the  two  cannot  be  seen  dis- 
tinctly if  they  are  together  in  the  same 
pbne.  Test  by  fixating  the  centre  of 
the  diagram ;  and  find  by  Scheiner's  ex- 
periment the  near  point  of  accommo- 
dation for  a  vertical  and  horizontal  pin. 
—  Helmholtz,  175;  Fick,  108. 

S.  It  may  be  added  that  the  sub- 
«itance  of  cornea  and  lens  is  not  quite 
insparent.  If  a  bright  light  be  seen 
against  a  dark  background,  it  is  sur- 
rounded with  a  whitish  nimbus,  which 
b  brightest  in  the  immediate  neighbour- 
hood of  the  flame.  Cover  the  light  by 
a  screen  brought  before  the  eye,  and 
*he    nimbus    disappears.  —  Helmholtz, 

:8- 

(</)  Imperfections  of  Accommodation^  Errors  of  Refraction.  —  Here 
belong  the  optical  defects  known  as  myopia  (short  sight)  and  hypermetropia 
(long  sight).  The  myopic  eye  b  too  long  for  the  lens,  or  the  lens  too  thick 
for  the  length  of  the  eye.  A  dbpersive  (biconcave)  lens  is  needed  to  remedy 
the  fault.  The  hypermetropic  eye  b  too  short  for  the  lens,  the  lens  not  thick 
enough  for  the  focussing  of  near  objects  on  the  retina :  the  remedy  b  a  col- 
lecting (biconvex)  lens.  —  Suter,  96  f. 

(^)    Imperfections  of  the  Refracting  Afedia^  Entoptic  Phinomena.  —  We 

have  seen  that  the  lack  of  transparency  of  cornea  and  lens  leads  to  a  form 

!   monochromatic  aberration.    There  are  various  other  disturbances  and 

nperfections  of  the  optical  system,  temporary  or  permanent,  which  show 

icmselves  in  the  field  of  vbion.    These  appearances  are  grouped  together 

under  the  general  title  of  'entoptic'  phenomena.     The  chief  of  them  are 

as  follows. 

a.  Drops  of  mobture  running  down  over  the  corneal  surface,  and  specks 
of  dust  or  mucus  caught  in  the  corneal  film,  appear  as  bright  cloudy  streaks 
and  bright-centred  circles  respectively.    They  disappear  with  winking. 

/?.  Crinkling  of  the  corneal  surface  by '  rubbing  the  eyes  ^  gives  rise  to  sys- 
tems of  wavy  or  criss-cross  lines,  or  speckled  patches. 


Fig.  51.  —  Helmhultz,  175, 


242  Visual  Space  Perception 

y.  Impurities  in  the  lens  or  its  capsule  are  seen  as  pearly  drops,  dark  specks, 
and  bright,  irregularly  stellate  forms.  Sometimes  a  dark  radiate  figure  comes 
up,  corresponding  to  the  structure  of  the  lens. 

8.  Impurities  in  the  vitreous  humour  produce  the  well-known  muscae  voli' 
tantes.  They  appear  as  large,  separate  circles  ;  strings  of  pearls ;  clusters  of 
bright  and  dark  circles,  of  various  sizes ;  bright  ribands  with  dark  borders, 
etc. 

€.  Retinal  circulation.  Look  steadily  (with  the  naked  eye  or,  preferably, 
through  a  blue  glass)  at  a  bright  cloud,  or  a  misty  summer  sky.  You  see 
numbers  of  bright  yellowish  points  moving  quickly  across  the  field,  appar- 
ently at  random.  Longer  observation  shows  that  the  tracks  are  permanent. 
The  phenomenon  is  due  to  the  temporary  clogging  of  the  retinal  capillaries 
by  large  blood  corpuscles. 

For  these  and  kindred  phenomena,  and  the  shadow-method  of  observa- 
tion, see  Helmholtz,  184  ff. ;  Sanford,  exps.  110-112 ;  Foster,  1189  ff. 


(4)  Eye  Movements. — The  best  account  of  eye  movements, 
from  the  psychological  side,  is  that  given  by  Wundt,  Phys. 
Psych.,  4th  ed.,  ii.,  109-124,  164-173.  It  owes  much  to  Her- 
ing's  Die  Lehre  vom  binocularen  Sehen  (1868).  This  book, 
the  same  author's  later  exposition  in  Hermann's  Handbuch  der 
Physiologic,  iii.,  i,  1879,  437  ff->  ^"^  Helmholtz'  section  (Physiol. 
Optik,  613-669),  should  be  read  by  all  advanced  students  :  they 
are  too  elaborate  and  technical  to  be  given  as  general  class  ref- 
erences. See  also  (especially  for  diagrams)  Foster,  1277-1291  ; 
Waller,  429-434. 

Questions. — (12),  (13)  See  references  above.  A  clear  no- 
tion of  false  torsion  may  be  obtained  from  Waller,  430  f.  The 
*  orientation  *  of  the  eye  is  its  determination  to  the  points  of 
the  compass  ;  more  specifically,  its  position  with  regard  to  ob- 
jects in  the  field  of  vision. 

(14)  The  tendency  (Sanford,  120)  is  that  "to  move  in  such  a 
way  as  to  bring  any  bright  image  lying  on  a  peripheral  part  of 
the  retina  .  .  .  into  the  area  of  clearest  vision."  See  Wundt, 
ii.,  171,  who  brings  the  reflex  tendency  into  relation  with  the 
laws  of  innervation  of  the  double  eye ;  cf.  Hering,  Bin.  Sehen, 
23  ff. 

(15)  See  Wundt,  166;  Hering,  Bin.  Sehen,  3;  Hermann's 
Hdbch.,  520. 

(16)  The  laws  of  F.  C.  Bonders  (a  Dutch  oculist,  1818-1889) 


$  4^   Ey€  Mevememis  243 

and  of  Listing  (p.  232  above)  are  differently  estimated  and  dif- 
lerently  placed  in  the  different  systematic  discussions  of  eye 
movement.  Wundt  recognises,  besides  the  psychophysical  law 
of  the  correspondence  of  apperception  and  fixation  (p.  234 
above),  three  physiological  laws  of  movement :  the  law  of  pref- 
erence of  the  primary  position,  the  law  of  simplest  innervation, 
and  the  law  of  constant  orientation.  The  last-named  is  the  law 
of  Donders.  All  three  may  be  subsumed  under  the  general 
principle  of  'movement  with  the  least  expenditure  of  muscular 
effort  * ;  and  Listing's  law  thus  becomes  merely  a  mechanical 
consequence  of  the  law  of  simplest  innervation.  —  Phys.  Psych., 
ii.,  1 16,  120  f.  ;  Helmholtz,  669. 

Helmholtz  and  Hering(Beitr,  z.  Physiol.,  iv.,  2,  260  t.)  incline 
to  admit  the  factual  validity  of  Wundt's  general  principle,  though 
they  do  not  consider  it  fundamental.  Donders'  law  is,  for  Helm- 
holtz, the  principle  of  easiest  orientation  for  resting  positions  of 
the  eye ;  and  Listing's  law  is  the  first  logical  step  beyond,  the 
solution  of  the  first  specific  problem  falling  under,  this  principle. 
Hering  names  Donders'  law  'the  law  of  same  retinal  position 
with  same  position  of  regard,'  and  brings  Listing's  law  into  im- 
mediate connection  with  it  under  the  title  Maw  of  orientation 
with  parallel  lines  of  vision.' — Phys.  Optik,  619  fF. ;  Bin.  Sehen, 
56,63. 

It  is  well  that  the  student  should  understand  the  two  laws  in 
relation,  and  we  shall  therefore  follow  Helmholtz  and  Hering  in 
our  order  of  treatment. 

Both  laws  are  laws  of  eye  movement ;  both  presuppose  a 
parallel  position  of  the  lines  of  regard  ;  and  both  are  formu- 
lated in  terms  of  torsion.  The  difficulty  of  stating  them  — 
as,  indeed,  the  wider  difficulty  of  their  systematic  treat- 
ment—  lies  very  largely  in  the  fact  that  neither  was  fully 
vorked  out  by  its  author  (Hering,  in  Hermann's  Hdbch., 
474;  Helmholtz,  669>  We  may  phrase  (i)  Donders'  law  as 
follows.  'Given  the  position  of  the  line  of  regard  in  rela- 
tion  to  the  head,  and  you  have  given  with  it  a  definite  and 
invariable  torsion  value'  (Helmholtz);  or  'The  orientation 
of  the  eyes  is  an  univocal  function  of  the  position  of  regard  * 
(Hering);  or  'The  orientation  of  the  eye  for  any  position  of 


244  Visual  Space  Perception 

the  line  of  vision  is  constant,  no  matter  by  what  path  the 
line  of  vision  may  have  been  brought  to  this  position  *  (Wundt). 
That  is  to  say :  if  you  set  out  with  the  lines  of  regard  par- 
allel, you  may  move  from  any  position  you  like  to  any  other 
position  that  you  like  in  the  field  of  regard,  and  the  orienta- 
tion of  the  eye  in  this  second  position  will  always  be  the 
same,  whether  you  travel  to  it  by  a  straight  road  or  by  a  road 
the  most  devious  and  complicated  possible.  You  might  con- 
ceivably have  any  number  of  changes  in  orientation,  corre- 
sponding to  different  degrees  of  torsion  (Wundt,  120);  so  that 
your  orientation  might  never  be  precisely  the  same  from  one 
movement  to  another.  Or  you  might,  of  course,  have  deter- 
minate torsions  correlated  with  certain  general  directions  of  the 
lines  traced  by  the  point  of  regard  (cf.  Helmholtz,  637).  As  a 
matter  of  fact,  orientation  is  constant :  as  you  were  when  you 
got  to  the  new  fixation-point  the  first  time,  so  will  you  be  when 
you  get  to  it  the  hundredth  time,  and  you  may  choose  your  own 
road. 

(2)  Listing's  law  implies  not  only  a  parallel  position  of  the 
lines  of  regard,  but  also  the  primary  position  of  the  eyes.  It 
may  be  phrased  as  follows.  '  If  the  line  of  regard  travel  from 
the  primary  to  any  other  position,  the  torsion  of  the  eyeball 
in  this  second  position  is  the  same  as  if  the  eye  had  turned 
about  a  fixed  axis  at  right  angles  to  the  first  and  second  direc- 
tions of  the  line  of  regard  *  (Helmholtz) ;  or  *  In  movement 
from  the  primary  position,  the  line  of  vision  can  describe 
a  plane  path,  or  the  regard  travel  along  a  straight  line,  in 
any  direction  whatsoever,  without  there  being  any  torsion  of 
the  eye  at  all  about  the  line  of  vision  :  in  other  words,  the 
eye  can  be  turned  in  all  directions  about  a  fixed  axis,  at  right 
angles  to  the  line  of  vision'  (Hering);  or  'All  movements 
from  the  primary  position  take  place  about  fixed  axes,  each 
of  which  cuts  the  plane,  described  by  the  line  of  vision  in 
turning,  at  right  angles  in  the  point  of  rotation,  and  all  of 
which  lie  in  a  single  plane,  cutting  the  primary  position  of 
the  line  of  vision  at  right  angles  in  the  point  of  rotation ' 
(Wundt).  That  is  to  say  :  if  you  set  out  with  the  lines  of  regard 
parallel  in  the  primary  position,  you  may  move  to  any  point  of 


§  4^   Ey€  Mavtwunts  245 

the  field  of  regard  that  you  like,  in  the  vertical,  horizontal  or 
oblique  direction,  and  your  eye  will  undergo  no  torsion  at  all. 
Not  only  is  the  orientation  constant :  not  only,  i.e.^  may  you  pre- 
suppose a  definite  and  invariable  torsion  value :  the  torsion  value 
is  zera 

We  now  proceed  to  put  these  laws  to  the  test  of  experi- 
ment 

Materials.  —  Head-rest,  with  mouth  board  and  sighting 
mark.  [The  latter  is  figured  by  Helmholtz,  657.  The  board  A 
is  43  by  4  cm.  The  semicircular  cut  is 
smeared  with  hot  sealing  wax ;  O  bites  into 
this,  before  it  is  cold,  the  impression  of  his 
teeth,  enabling  him  always  to  take  up  pre- 
cisely the  same  position  in  the  head-rest. 
^  is  a  wooden  upright,  and  C  a  strip  of 
card  or  stifif  paper,  stuck  to  B  by  wax. 
The  length  of  C  must   be   made   equal   to  ^*  T57.* 

the  interocular  distance  (the  distance  be- 
tween the  points  of  rotation  of  the  eyes).  This  distance  is 
determined  as  follows.  Fixate  a  point  upon  the  remote  hori- 
zon. The  paper  strip  appears  in  double  images.  The  strip 
must  be  so  adjusted,  and  its  ends  so  clipped,  that  the  inner 
edges  of  the  two  images  just  touch  in  the  same  straight  line. 
The  length  of  the  strip  then  corresponds  to  the  interocular 
distance.] 

Large  g^ey  or  white  screen,  ruled  in  black  at  equal  distances 
with  vertical  and  horizontal  lines.  Two  strips  of  red  cardboard, 
with  pins  for  fastening.  [As  to  the  dimensions  of  the  screen, 
one  can  only  say  —  since  parallel  lines  of  regard  are  required  — 
'the  larger  the  better.*  The  end-wall  of  a  large  lecture  room 
may  be  utilised,  by  hanging  strips  of  black  tape,  weighted  at 
their  lower  ends,  from  the  picture-moulding,  and  tacking  other 
strips  horizontally  and  diagonally,  as  the  experiment  calls  for 
them.  To  set  a  lower  limit :  a  screen  of  2  m.  square  can  proba- 
bly be  accommodated  in  the  smallest  lecture  room,  and  with  an 
ordinary  head-rest  will  answer  the  purpose  of  the  experiment 
fairly  well.  It  should  consist  of  white  cotton  cloth,  stretched 
over  a  light  wooden  frame ;  the  lines  arc  made  as  required  by 


246  Visual  Space  Perception 

pinning-on  lengths  of   black   tape.     The  coloured   strips   ma)> 
then  be  cut  15  by  1.5  cm.] 

Sanford  recommends  (Lab.  Course,  122)  the  use  of  a  quarter-screen  (left- 
hand  upper  quarter),  containing  a  vertical,  a  horizontal,  and  a  prolonged 
oblique  radius.  The  author  has  had  this  screen  made  of  white  holland,  and 
mounted  on  a  10  cm.  spring  roller,  like  a  heavy  window  shade.  The  screen  is 
3.5  by  2.6  m. ;  the  vertical,  horizontal  and  oblique  lines,  and  their  fixation 
points,  are  painted  on  the  cloth  (vertical  and  horizontal  radii,  2.15  m.,  oblique 
line,  about  3  m.).  A  light  green  disc  of  30  cm.  diameter,  carrying  a  cross  of 
deep  red  lines,  2  cm.  wide,  can  be  turned  in  a  brass  eye  placed  at  the  point 
of  intersection  of  the  three  lines.  The  observer  is  stationed  at  a  distance 
of  some  8  m.  This  apparatus  works  satisfactorily,  is  very  compact,  and  can 
be  installed  for  $15.00.  The  classical  form  of  the  experiment,  with  the  com- 
plete (not  quarter)  screen,  is,  however,  preferable. 


Experiment  (i).  —  Bonders'  Law.  O  stands  as  far  as  possi- 
ble away  from  the  ruled  screen,  and  secures  his  head  in  the 
head-rest  by  biting  into  the  mouth  board  (the  wooden  upright 
and  paper  strip  are  removed).  E  places  the  red  cardboard  strips 
at  right  angles  to  each  other  over  the  point  of  intersection  of  a 
vertical  and  horizontal  line  upon  the  screen.  O  fixates  the  centre 
of  the  red  cross,  steadily,  until  a  clear  after-image  is  set  up.  He 
then  projects  the  after-image  to  some  point  upon  the  screen,  and 
carefully  observes  its  appearance  and  position  with  regard  to 
the  nearest  lines.  If  necessary,  E  marks  the  outline  of  the 
after-image  upon  the  screen,  O  indicating  its  position  to  him  by 
finger  movements  agreed  upon  beforehand. 

This  done,  O  returns  to  the  red  cross,  and  again  waits  for 
the  formation  of  a  clear  after-image.  Having  obtained  it, 
he  moves  his  eyes  at  random,  over  side-walls,  ceiling,  etc., 
and  only  after  such  excursion  brings  the  after-image  to  rest  at 
the  place  upon  the  screen  chosen  in  the  first  part  of  the  experi- 
ment. The  new  after-image  may  'hesitate'  for  a  couple  of 
seconds,  but  almost  immediately  takes  up  the  precise  position 
occupied  by  its  predecessor  (Helmholtz,  623  f. ;  Hering,  Bin. 
Sehen,  58). 

Hering's  experiment  with  the  rotated  stereoscopic  half-picture  may  well  be 
performed  here :  Bin.  Sehen,  57. 


§  4^.   DofuUrs*  and  Listing* s  Laws  247 

(2)  Determination  of  the  Primary  Position.  This  position  (as 
stated  by  Listing  and  confirmed  by  Helmholtz)  varies  but  little 
for  the  emmetropic  eye  from  that  in  which  the  head  is  held 
upright  in  its  normal  attitude,  and  the  eyes  are  fixed  upon  a 
remote  point  at  their  own  level  above  the  horizon ;  so  that 
the  lines  of  regard  are  parallel  and  directed  straight  for- 
wards in  the  horizontal  plane.  It  differs  somewhat,  however, 
for  different  observers,  and  even  for  the  same  observer  at 
different  times.  And,  as  a  rule,  the  plane  of  regard  is  slightly 
depressed  below  the  horizontal  plane.  —  Aubert,  608,  654  f. ; 
Hering,  Bin.  Sehen,  44,  64;  Hermann's  Hdbch.,  471  ;  Helm- 
holtz, 626;  Wundt,  114. 

O  sits  at  the  far  end  of  the  room,  his  eyes  directly  opposite 
the  point  of  intersection  of  the  vertical  and  horizontal  lines 
at  the  centre  of  the  screen.  The  position  of  his  head  is  fixed 
by  the  head-rest  and  mouth  board,  which  latter  now  carries  the 
sighting  mark.  E  places  a  red  strip  horizontally  at  the  centre 
of  the  screen.  O  closes  one  eye,  and  looks  with  the  other,  past 
the  corresponding  end  of  the  sighting  mark,  towards  the  red 
strip.  When  an  after-image  has  developed,  he  moves  it  straight 
up  and  down,  and  straight  in  and  out,  and  observes  whether  it 
coincides  with  the  horizontal  lines  of  the  screen.  If  it  does,  the 
primary  position  is  found.  If  it  does  not,  the  position  of  the 
sighting  mark  must  be  corrected.  Suppose  that,  as  O  looks  up, 
the  left  end  of  the  after-image  is  the  higher ;  and,  as  he  looks 
down,  the  left  end  is  the  lower :  then  the  paper  strip  C  must  be 
pushed  to  the  left.  If  the  image  has  the  opposite  inclinations, 
the  strip  must  go  to  the  right.  Suppose  that,  as  he  looks  to  the 
left,  the  left  end  is  the  lower ;  and  as  he  looks  to  the  right,  the 
right  end :  the  strip  must  be  pushed  up.  In  the  opposite  case, 
it  must  go  down. 

Repeat  the  experiment  with  the  other  eye,  and  then  with  both 
eyes  open.  —  Helmholtz,  658  ;  Aubert,  654 ;  Hering,  Bin.  Sehen, 
74  ff. ;  Hermann's  Hdbch.,  471  ff.  Notice  Hering's  caution  that 
"  the  more  carelessly  one  works,  the  prettier  is  the  [apparent] 
agreement  with  the  law." 

(3)  Listing's  Law.  O  puts  his  eyes  in  the  primary  position. 
E  fixes  the  two  red  strips  upon  the  vertical  and  horizontal  lines 


248 


Visual  Space  Perception 


■+ 


-7^ 


^ 


intersecting  ai  the  centre  of  the  screen.  0  obtains  an  after- 
image of  the  rectangular  cross,  and  projects  it  straight  up  and 
down,  and  straight  in  and  out,  from  the  primary  position.  The 
vertical  limb  of  the  image  coincides  with  the  central  vertical 
line  of  the  screen  ;  its  horizontal  limb  coincides  with  the  central 
horizontal  line.     There  is,  therefore,  no  torsion. 

The  horizontal  and  vertical  tapes  of  the  screen  are  now  un- 
pinned and  pulled  aside,  and  two  diagonals  stretched.  [If  the 
small  screen  is  used,  it  is  turned  up  on  end,  through  45°.]  The 
red  cross  is  placed  upon  the  diagonals,  so  that  its  limbs  lie 
obliquely.      O  gets   an   after-image,  and   projects  it  along  the 

diagonals.  The  oblique  lines  of 
the  image  coincide  with  the  black 
lines  of  the  screen.  Again,  then, 
in  these  oblique  movements  from 
the  primary  position,  there  is  no 
torsion. 

The  screen  is  restored  to  its 
previous  form,  with  the  cross 
placed  rectangularly.  O  gets  an 
after-image,  and  projects  it  ob- 
liquely, say,  to  the  upper  right- 
hand  point  of  intersection  of  a 
vertical  and  a  horizontal  line 
upon  the  screen.  The  after-image  does  not  appear  as  a  rec- 
tangular cross,  but  assumes  the  appearance  and  position  shown 
2X  a  in  the  diagram.  The  change  cannot  be  due  to  torsion; 
oblique  movements  from  the  primary  position  have  just  been 
shown  not  to  produce  torsion.  Moreover,  no  amount  of  torsion 
could  produce  this  particular  change ;  for  the  vertical  limb  is 
turned  outy  while  the  horizontal  is  turned  in;  and  torsion 
would  have  turned  both  in  the  same  sense.  To  what,  then, 
is  it  due  } 

Is  it  due  to  what  is  called  a  false  torsion,  or  torsion  of  projec- 
tion. If  the  line  of  sight  is  directed  to  the  point  a  of  the  figure, 
the  vertical  and  horizontal  lines  that  intersect  at  this  point  are 
projected  on  the  retina  in  the  directions  of  the  lines  hh  and  vv 
in  Fig.  54  A,  while  the  after-image  remains  rectangular,  as  the 


^r 


Fig.  53.  —  Hering,  Bin.  Sehen,  67. 


§  4^.   Listing* s  Law 


249 


\' 


cross  in  the  same  Fig.  shows.  But  we  still  see  the  lines  of  the 
screen  as  rectangular,  f./.,  we  see  all  the  angles  vah  as  right 
angles,  because  we  refer  their  dis- 
torted retinal  image  not  to  a  field 
of  vision  that  cuts  the  direction  of 
regard  at  right  angles,  but  to  a  field 
that  lies  parallel  to  the  frontal  plane. 
It  follows,  then,  that  we  must  see 
the  really  rectangular  after-image  of 
the  cross  in  the  position  indicated  in 
Fig.  54  B,  The  apparent  distortion 
of  the  after-image,  its  *  false  torsion,* 
is  due  to  the  fact  that  we  persist 
in  seeing  the  vertical  and  horizontal 
screen-lines  as  vertical  and  horizon- 
tal, despite  their  oblique  projection 
on  the  retina. —  Hering,  Bin.  Sehen, 
68;  Hermann's  Hdbch.,486;  Wundt, 
118;  Aubert,  656;  Helmholtz,  622, 
658. 

This  whole  experiment  must  be 
performed  with  each  eye  singly. 
For  there  is,  plainly,  a  possibility 
that  compensatory  torsions  of  the 
two  eyes  occur,  in  which  case  ordi- 
nary observation  would  take  the  after-image  to  be  coincident  with 
the  vertical  and  horizontal  screen-lines,  and  only  a  very  keen  and 
accurate  discrimination  would  discover  the  double  images  and 
their  intersection  at  a  small  acute  angle  (Hering,  in  Her- 
mann's Hdbch.,  474).  It  may  then  be  performed  with  both 
eyes  open. 


Fic.  54.  —  Hering,  Bin.  Sehen,  68. 


It  is  an  evident  corollary  to  the  law  and  its  experimental  verification  as  given 
above,  that  if  the  line  of  vision  is  to  describe  a  plane  path,  not  from  the  primary 
but  from  some  secondary  position,  the  eye  cannot  turn  about  a  fixed  axis  at 
right  angles  to  the  line  of  vision,  /./.,  cannot  turn  without  torsion,  save  in  the 
single  case  that  the  plane  in  which  the  line  of  vision  moves  is  a  plane  passing 
through  the  primary  position.  Suppose,  e.g.y  that  the  head  is  inclined  straight 
downwards  from  the  primary  position,  and  the  after-image  of  the  horizontal 


250  Visual  Space  Perception 

strip  is  obtained  with  the  eyes  raised.  Projection  of  the  image  on  the  hori- 
zontal meridian  of  the  screen,  to  right  or  left,  shows  an  increasing  torsion  as 
the  line  of  regard  travels  from  the  original  fixation-point.  Suppose,  now,  that 
the  after-image  of  the  vertical  strip  is  got  with  the  same  position  of  eyes  and 
head.  This  time,  the  after-image,  as  the  eyes  carry  it  up  or  down,  remains  in 
the  vertical  screen-line :  the  line  of  regard  is  moving  in  a  plane  which  con- 
tains the  primary  position  (plane  of  the  primary  vertical  meridian :  Hering, 
Bin.  Sehen,  66).  If,  on  the  other  hand,  the  image  is  carried  along  the  hori- 
zontal meridian,  it  does  not  remain  perpendicular  to  it,  but  shows  traces  of 
torsion.  —  Repeat  these  observations,  with  the  head  turned  to  right  or  left, 
and  down  upon  the  right  or  left  shoulder. 

We  need  not,  however,  move  the  head,  in  order  to  obtain  a  secondary  posi- 
tion :  it  is  sufficient  to  move  the  eyes.  Think  of  our  screen  as  divided  into 
six  vertical  columns  of  equal  width  by  seven  vertical  tapes.  Let  a  red  strip  be 
fixed  vertically  at  the  centre  of  the  middle  line ;  and  let  the  eyes  be  set  over 
against  the  centre  of  the  strip  in  the  primary  position.  If  we  move  the  after- 
image straight  up  or  down,  and  straight  in  and  out,  there  is  no  torsion.  But 
if  we  move  it  a  step  out,  and  then  up ;  two  steps  out,  and  then  down ;  and 
so  on,  then  we  get  a  torsion.  By  moving  always  only  in  the  horizontal 
and  vertical  directions  we  avoid  the  false  torsion  of  projection,  and  get  a 
true  picture  from  the  after-image  of  the  direction  of  torsion  (Hering,  Bin. 
Sehen.  70). 

There  are  two  important  geometrical  corollaries  to  the  law,  which  may  be 
worked  out  by  students  if  time  permit :  see  Question  (24)  below.  They  are 
as  follows,  (i)  All  the  axes  about  which  the  eye  can  begin  to  turn  from  the 
primary  position  lie  in  a  single  plane.  The  same  thing  holds  of  movement 
from  any  secondary  position,  only  that  in  such  cases  the  axial  plane  has  a 
differ etit  position  to  the  line  of  vision.  (2)  The  eye  can  turn  about  a  fixed 
axis  from  any  given  secondary  position  to  any  other  secondary  position.  If 
the  fixed  axis  is  one  of  the  primary  axes,  so  that  the  line  of  vision  must  pass 
through  the  primary  position,  the  path  described  is  a  plane  path.  If  the  posi- 
tions passed  through  are  all  secondary  positions^  the  line  of  vision  describes  a 
curved path^  in  general,  a  path  upon  the  surface  of  a  cone. 

For  deviations  from  the  laws  of  Bonders  and  Listing,  with  convergent  lines 
of  regard,  see  Hering,  Bin.  Sehen,  58,  92  ff. ;  Hermann's  Hdbch.,  496  ff. ; 
Helmholtz,  625  ff.,  659,  664 ;  Aubert,  658  ff. 

Sanford  has  constructed  a  model  of  the  hemispherical  field  of  regard,  pro- 
jection within  which  avoids  the  false  torsion  of  the  plane  field.  Since,  how- 
ever, the  hemisphere  is  so  small  that  the  vertical  meridians  are  not  parallel  for 
vision,  but  converge  sensibly  above  and  below,  a  new  (though  smaller)  false 
torsion  is  introduced  (Lab.  Course,  423).  When  the  hemispherical  is  con- 
verted into  a  plane  field,  by  gnomonic  projection  upon  a  plane  tangential  to  it 
at  the  middle  point  of  the  central  cross,  this  new  false  torsion  is,  of  course, 
superadded  to  the  false  torsion  of  plane  projection  which  we  have  been  discuss- 


§  4^.   Danders^  attd  Lisfwg's  Laws  351 

log  (lAui.y  425  f.).  Notice  that  Sanford  uses  the  phrase  *  rotation  of  the  eye 
about  the  line  of  regard'  for  what  is  here  termed  *  torsion/  and  the  word 
'torsion'  in  the  sense  of  HelmkoUt'^Khi Raddrtkung  (Aubert,  657)  for  what 
we  have  called  *  £alse  torsion.* 

For  methods  and  apparatus  more  accurate  than  those  given  in  the  text,  see 
Helmholtx,  659 ;  Hering,  Bin.  Sehem  78.  For  the  Hering  method  of  substi- 
tution, see  Bin.  Sehen,  83  ff. :  Hermann's  Hdbch.,  480  if. ;  Helmholtz,  662  f. ; 
Aubert,  647,  649- 


\Vhat,  now,  is  the  good  of  these  laws  ?  What  is  their  optical 
significance.^  The  question  will,  as  we  said  at  the  outset,  be 
differently  answered,  according  to  the  stress  laid  upon  the  one 
or  the  other  law  in  an  author's  systematic  treatment  of  binocular 
eye  movement.  Helmholtz  looks  upon  Donders*  law  as  a  guaran- 
tee that  resting  objects  in  the  field  of  vision  are  recognised  as 
such,  !>.,  are  seen  to  be  resting  objects,  when  the  eye  itself  has 
been  moved  (638).  "The  observance  of  this  law  must  contrib- 
ute essentially  to  the  ease  and  certainty  with  which  we  solve 
the  problem  of  recognising  unmoved  objects  on  the  retina  as 
unmoved,  despite  the  movements  of  the  eyes  and  despite  the 
displacements  of  the  retinal  images  "  (637 ;  cf.  638,  footnote). 
Listing's  law  is  then  shown  to  be  the  most  advantageous  law  of 
eye  movement,  so  far  as  orientation  is  concerned,  first  of  all  for 
monocular  vision  and  a  circular  field  of  regard,  and  then  for  the 
binocular  field  with  parallel  lines  of  vision  (642  f.).  Hering 
estimates  Listing's  law  as  follows.  "  It  brings  the  space  per- 
ception [localisation]  of  the  moved  eye  into  the  greatest  possi- 
ble unison  with  the  perceptions  [localisations]  of  the  resting 
eye,"  so  that  "the  displacements  of  the  retinal  images  harmonise 
with  the  intended  movements  of  regard  "  (principle  of  avoidance 
of  torsion,  or  of  'apparent  movement'  of  objects  in  the  visual 
field) ;  while  it  also  assures  in  far  vision  **  the  most  perfect  pos- 
sible correspondence  of  the  retinal  images  of  the  double  eye  " 
(principle  of  the  greatest  horopter):  Bin.  Sehen,  106  f . ;  Her- 
mann's Hdbch.,  539,  cf.  503.  He  brings  Bonders'  law  under 
his  *  principle  of  simplest  innervation '  in  eye  movements  :  Bin. 
Schcn,  56,  cf.  32  flf. ;  and  see  esp.  Beitrage  z.  Physiol.,  iv.,  2, 
1864,  248  ff.  The  reconciliation  of  these  three  principles  in 
practice  is  discussed  in  the  Beitr.,  loc.  cit,  269  ff.     Wundt,  as 


252  Visual  Space  Perception 

we  saw  above  (p.  243),  subsumes  all  the  laws  of  eye  movement  to 
the  principle  of  least  expenditure  of  muscular  effort ;  A.  Fick, 
in  articles  published  in  1854  and  1858,  did  the  same  thing.  Le 
Conte  (Sight,  1881,  164  ff.)  accepts  Listing's  law  as  the  law  of 
parallel  movements,  but  declares  that  in  convergence  "the  law 
of  Listing  is  wholly  abrogated,  or  else  overcome,  and  another 
law  [that  of  outward  rotation]  reigns  in  its  place."  Cf.  Aubert, 
669  f. 

(5)  Corresponding  Points  and  Double  Images.  —  See  Helm- 
holtz,  841  fF. ;  Wundt,  ii.,  173  ff. ;  Hering,  in  Hermann's  Hdbch., 
iii.,  I,  343  ff. ;  Beitr.  z.  Physiol.,  esp.  i.,  1861,  22  ff . ;  iii.,  1863, 
184  ff.;  Foster,  1275-1277,  1291  f. 

Questions. — (17)  The  terminology  of  the  'points'  is  from 
Wundt,  q.  v.  It  is  not  necessary  that  the  student,  at  this  stage, 
should  know  more  of  the  horopter  than  is  given  in  Waller,  426 
f.,  or  Foster,  1291  f. 

(18)  There  are  several  methods  for  this  determination.  The 
most  satisfactory  is,  perhaps,  that  finally  recommended  by 
Helmholtz,  which  may  be  given  in  his  own  words.  It  presup- 
poses practice  in  'parallel  vision.' 

"A  sheet  of  black  paper  is  stretched  upon  a  vertical  wooden  board.  Upon 
the  paper  are  fastened,  side  by  side,  («)  a  strip  of  red  paper,  3  mm.  wide  and 
bounded  by  two  straight  parallel  edges,  and  {b)  a  blue  thread.  Strip  and 
thread  are  set  almost  vertically,  diverging  a  little  from  below  upwards.  The 
distance  between  them,  at  the  height  of  the  eyes  of  the  observer,  is  equal  to 
the  distance  between  his  two  eyes.  The  strip  is  fastened  at  both  ends,  the 
thread  only  at  the  upper  end ;  it  is  kept  taut  by  a  small  weight  attached  to  its 
lower  end.  The  observer  pushes  the  lower  end  of  the  thread  sidewards  with 
a  pin,  as  far  as  is  necessary,  and  finally  sticks  the  pin  in  the  board  when  the 
thread  has  come  to  the  right  position.  He  looks  at  strip  and  thread  with 
parallel  lines  of  regard,  so  that  the  blue  thread  appears  in  the  middle  of  the 
red  strip,  and  moves  the  thread  until  it  seems  to  lie  along  its  whole  length 
precisely  in  the  middle  of  the  strip.  Then  he  sticks  the  pin  in  the  board.  By 
measuring  the  distance  of  the  thread  from  the  strip  at  its  upper  and  lower 
ends,  and  the  vertical  distance  between  these  two  points,  he  can  easily  deter- 
mine the  angle  required."  —  Phys.  Optik,  851  ;  cf.  687  f. 

See  Hering,  Beitrage,  iii.,  1863,  175  ff. ;  Hermann's  Hdbch.,  iii.,  2,  355  ff., 
368  f. ;  Wundt,  Phys.  Psych.,  ii.,  140  ff . ;  Aubert,  Phys.  Optik,  608  f.  San- 
ford  gives  a  simple  and  pretty  experiment  (Lab.  Course,  268  f.)  by  a  method 
which  appears  to  have  been  suggested  by  Meissner,  and  was  later  modified  by 
Volkmann,  Helmholtz  and  Hering. 


§  4^.   Double  Images 


253 


{19)  The  two  fingers,  held  out  on  the  same  line  of  vision,  or 
two  pegs  on  a  metre  stick,  answer  very  well.  The  diagrams  for 
double  images  of  this  kind  are  given  in  Figs.  55,  56.  In  the 
former,  the  fixation-point  is  constant,  and  the  object  varies  its 
position ;  in  the  latter,  the  object  is  constant  and  the  fixation- 


FiG.  55. 


Fig.  56. 


point  varies.  Students  who  do  not  carry  these  diagrams  *in 
their  heads'  by  visual  memory  are  apt  to  be  confused  by  the 
occurrence  in  books  now  of  the  one  and  now  of  the  other  figure. 
They  may  be  helped  by  the  mnemotechnic  lines : 

Remote  regard  reverses ; 
Nearer  notice,  not. 

Remember  that  other  diagrams  are  to  be  drawn,  in  which  the 
non-corresponding  points  fall,  not  upon  the  two  nasal  or  two 
temporal  retinas,  but  upon  the  nasal  side  of  the  one  and  the 
temporal  side  of  the  other. 

It  was  a  dogma  of  the  older  literature  of  physiological  optics 
that  double  images  are  always  seen  in  the  plane  of  the  fixation- 
point.  Hering  has  insisted,  and  Helmholtz  agrees,  that  double 
images  are  seen  for  the  most  part  fairly  accurately,  i.e.,  in  a 
plane  not  far  removed  from  that  of  the  object  which  gives  rise 


254  Visual  Space  Perception 

to  them.  This  plane  is  somewhat  variable ;  it  lies  always  be- 
tween the  planes  of  object  and  fixation-point.  With  continued 
steady  fixation,  and  in  the  absence  of  all  empirical  criteria,  it 
practically  coincides  with  the  latter.  —  Wundt,  178;  Helmholtz, 
Z6Z\  Hering,  Beitr.  z.  Physiol.,  v.,  1864,  335;  cf.  ii.,  1862,  142 
ff. ;  Hermann's  Hdbch.,  427. 

In  Scheiner's  experiment,  we  made  two  images  of  a  single 
object  fall  on  different  parts  of  the  same  retina ;  here  we  make 
two  images  of  a  single  object  fall  on  non-corresponding  parts  of 
the  two  retinas.  The  principle  of  crossed  and  uncrossed  images 
is  the  same  in  both  cases. 

(20)  This  (imaginary)  statement  is  given  as  typical  of  the 
statements  which  the  student  is  likely  to  meet  in  text-book  or 
other  brief  expositions  of  the  theory  of  binocular  vision.  It 
may  be  so  interpreted  as  to  be  correct ;  as  it  stands,  it  is  very 
misleading.  Fifty  years  ago,  facile  reference  to  *  experience' 
and  *  empirical  motives '  was  permissible.  The  factors  that 
enter  into  *  experience '  had  not  been  analysed  out.  Nowadays, 
we  have  to  deal,  not  with  *  experience '  in  the  large,  but  with  a 
number  of  special  facts  (facts  of  organism  and  facts  of  environ- 
ment), which  take  on  a  different  colouring  and  a  different  rela- 
tive importance  according  to  the  general  theory  in  which  they 
find  a  setting.  Hence  the  student,  after  doing  what  he  can  to 
estimate  the  statement  quoted,  should  be  referred  to  Wundt's 
elaborate  argument  on  pp.  179-184,  to  Helmholtz'  chain  of 
deduction  on  pp.  948  f.,  or  to  Hering's  masterly  summary  in 
Hermann's  Hdbch.,  424  ff.  The  lesson  to  be  learned  is,  that  if 
one  talks  of  *  experience '  one  must  have  a  very  clear  and  very 
detailed  notion  of  what '  experience '  means.  It  is  no  more  *  sci- 
entific '  to  *  explain '  a  given  phenomenon  by  referring  it  to  an 
indefinite  experience,  than  it  is  to  *  explain'  it  by  reference  to 
an  unconditioned  and  indeterminable  faculty  of  will.  —  Limits 
of  space  forbid  the  working-out  of  an  illustration.  Some  one  of 
the  above  instances,  however,  or  a  similar  instance  chosen  by 
the  Instructor,  should  by  all  means  be  worked  out  by  the 
student. 

Additional  Questions. — (21)  "  Not  only  the  more  general 
movements  of  the  eye  which  obey  Listing's  law,  but  also  those 


§  46.    SMmmary  of  PrelimtHarUs  255 

which  form  an  exception  to  it,  appear  to  be  carried  out  in  the 
interests  of  binocular  vision  "  (Foster).  Work  out  the  cases  in 
which  torsion  occurs,  and  test  this  statement. 

(22)  Make  three  pin-holes  .*.  in  a  card,  within  a  space  smaller 
than  the  extent  of  the  pupil.  Bring  the  card  close  up  to  the 
pupil.  Some  2  or  3  cm.  before  it  hold  another  card,  pierced 
with  a  single  pin-hole.     The  triangle  appears  as  *.  * . 

Hold  the  second  card  some  3  or  4  cm.  before  the  pupil. 
Bring  up  the  head  of  a  pin,  close  to  the  pupil.  You  see  a  large, 
shadowy  inverted  pin  in  the  circle  of  light. 

Explain  these  two  results. 

(C3)  Seat  yourself  at  about  50  cm.  distance  from  a  window 
commanding  a  wide  prospect.  Secure  the  head  in  a  head-rest. 
Close  the  right  eye.  Select  with  the  left  eye  some  prominent 
object  in  the  field  (a  tree,  c.g.\  lying  a  little  to  your  right. 
Make  an  ink-mark  on  the  window  pane,  covering  the  centre  of 
the  tree  as  seen  by  the  left  eye.  Now  close  the  left  and  open 
the  right  eye.  Notice  what  object  in  the  field  (a  chimney,  eg,) 
is  partially  covered  by  the  ink-mark.  Finally,  open  both  eyes, 
and  fixate  the  ink-mark.  Directly  behind  it,  and  partly  covered 
by  it,  you  see  both  tree  and  chimney;  in  other  words,  mark, 
tree  and  chimney  lie  in  the  same  direction.  —  Explain  this 
result  See  Hering,  Hermann's  Hdbch.,  iii.,  i,  386  fif. ;  Hofler, 
Psychologic,  291  fif. 

(24)  Define:  circles  of  direction  (right  circles),  occipital  point, 
atropic  line.  —  Sanford,  424  ;  Helmholtz,  651,  6^%  ;  Hering,  Bin. 
Sehen,  73  ;  Hermann's  Hdbch.,  490  ff. 

We  have  now,  at  least  in  essentials,  fulfilled  Brewster's 
requirements  of  those  who  enter  upon  the  study  of  stereoscopic 
vision.  And  the  Instructor,  so  far  from  extending  the  exercises 
to  greater  length  (p.  232),  may  very  well  object  that  work  of  this 
sort  is  physiological,  or  at  best  psychophysical ;  not  psychologi- 
cal at  alL  Could  we  not  get  on,  in  psychology,  without  it?  Do 
we  ever  really  make  use  of  this  cumbrous  terminology  ?  Is  it 
worth  while  to  take  the  student  back  to  the  times  when  contro- 
versy raged  about  the  horopter  and  the  projection  theory  and 
the  doctrine  of  identity  ? 


256  Visual  Space  Perception 

The  answer  is  the  same,  whether  we  appeal  to  authority  or  to 
experimental  work.  None  of  the  men  who  have  erected  '  theo- 
ries *  of  space  perception  have  failed  to  go  through  the  mill ;  all 
the  expositions  of  such  theories  take  the  reader  through  it, 
before  the  psychology  is  reached.  The  same  thing  holds  of 
experimentation  ;  you  cannot  set  a  student  to  work  upon  the 
stereoscope,  with  any  hope  of  intelligent  results,  unless  the  pre- 
liminary matters  which  we  have  been  discussing  are  as  familiar 
to  him  as  the  alphabet.  The  author  wrote  out  Exp.  XXVII. 
before  he  wrote  the  present  Section,  and  jotted  down  as  he  went 
the  points  that  called  for  a  preceding  explanation.  No  single 
topic  has  been  introduced  here  that  was  not  directly  suggested 
by  the  course  of  the  Experiment ;  no  single  test  has  been  given 
merely  *for  the  sake  of  completeness.'  As  for  the  direct  bear- 
ing of  the  preliminaries  upon  psychology  proper,  upon  space 
theory,  it  will  perhaps  be  enough  if  the  student,  at  this  stage, 
realises  how  great  is  the  complexity  of  the  problem,  how  im- 
mense the  collection  of  observed  facts,  and  how  imperative  the 
need  of  accuracy.  He  need  not  attempt  to  form  an  opinion 
of  his  own  until  he  comes  to  systematic  work,  at  the  conclusion 
of  this  Course.  It  is  very  much  better  that  he  should  acquire 
knowledge  and  suspend  judgment. 

Even  for  the  mature  psychologist,  judgment  is  sufficiently 
difficult.  We  find  Hering  declaring  that  the  eye-movement 
theory  of  the  depth  perception  *  turns  things  upside  down,'  and 
Aubert  and  Bonders  saying  that  one  of  the  essential  proposi- 
tions in  Hering's  own  theory  is  *  only  a  periphrasis  of  the  facts, 
but  no  explanation.'  Wundt  asserts  that  Hering  gives  *  forced 
explanations  '  and  comes  into  '  conflict  with  observation ' ;  Her- 
ing is  no  less  emphatic  on  the  point  that  Wundt  has  '  two  views, 
which  are  without  any  question  mutually  exclusive,  but  which 
are  none  the  less  represented  at  one  and  the  same  time.* 
Wundt,  again,  finds  that  Helmholtz  and  Bain  fail  to  overcome 
the  difficulty  inherent  in  all  '  empiristic '  theories,  the  difficulty 
that  perception,  the  basis  of  experience,  cannot  itself  rest  upon 
experience.  Hering,  too,  is  very  decidedly  opposed  to  Helm- 
holtz' doctrine  of  the  empirical  coordination  of  the  two  eyes  for 
purposes  of  space  perception.     Helmholtz,  on  his  side,  appeals 


§  47-    Stenoscofy  257 

confidently  to  experiments  which  show  that  Hering's  hypothesis 
contradicts  the  facts,  and  regards  Hering*s  '  Tiefengefiihle/  in 
particular,  as  valueless. 

All  this  means,  simply,  that  (as  Helmholtz  says)  "the  ques- 
tions here  discussed  are  not  yet  fully  ripe  for  discussion."  It 
does  not  mean  (and  the  Instructor  should  see  that  the  student 
does  not  fall  into  any  such  mistake)  that  the  psychology  of 
visual  space  perception  is  nothing  but  controversy,  "  gossip  and 
wrangle  about  opinions."  The  facts  are  given :  the  difficulty 
lies  in  coordinating  and  unifying  the  facts.  Every  *  theory '  sur- 
mounts this  difficulty  for  a  certain  proportion  of  the  given  mate- 
rial, or  perhaps  for  all  the  material  as  considered  under  certain 
aspects.  On  the  objective  side,  therefore,  a  theory  serves  as  the 
point  of  departure  for  new  investigations ;  and  in  this  way  the 
clash  of  theories  is  of  extreme  importance  for  the  progress  of 
science.  On  the  subjective  side,  the  theory  furnishes  an  aid  to 
memory,  acts  as  a  net  to  hold  the  facts  together,  while  it  also 
provides  a  working  hypothesis,  a  code  of  provisional  beliefs. 
The  author  has  known  students  to  be  discouraged  and  disheart- 
ened by  the  divergence  of  expert  opinion.  *  If  Helmholtz  and 
Hering  and  Wundt,  who  have  done  so  much,  cannot  agree,*  they 
say,  *  how  can  we  hope  to  do  anything }  *  But  every  one  of  us 
has  the  right  to  theorise,  when  he  knows  the  facts  ;  every  one  is 
assisted  to  such  knowledge,  meantime,  by  the  existing  theories ; 
and  every  one  may  hope  that,  as  the  opposing  theories  grate 
and  grind  in  his  thought,  they  will  at  least  strike  out  a  few 
illuminating  sparks,  if  they  are  not  worn  and  rounded  to  a  valid 
compromise. 

BZPERIMENT    XXVU 

§47.  Stcreoscopy.  Cautions  not  noted  in  the  Text. — The 
language  of  this  Experiment  has  been  made  as  simple  and  as 
little  technical  as  possible,  in  order  to  test  the  student's  assimi- 
lation of  the  terms  and  definitions  of  the  preceding  Section. 
If  these  have  been  thoroughly  mastered,  the  Experiment  will 
fall  into  its  technical  setting  of  itself ;  if  they  have  not,  there 
will  be  hitches  and  difficulties  in  the  work,  which  can  be  over- 
come only  by  a  retracing  of  the  path  too  hurriedly  traversed. 


258  Visual  Space  Perception 

This  is  the  student's  best  introduction  to  the  synthetic  experi- 
ment, the  nature  of  which  should  be  made  clear  to  him.  Roughly 
defined,  a  synthetic  experiment  is  one  in  which  the  products  of 
mental  analysis  are  artificially  brought  together,  and  the  result 
of  this  recombination  observed,  in  order  that  the  exhaustive- 
ness  of  the  analysis  may  thereby  be  proved  or  disproved.  By 
analysis  we  have  reduced  a  tangle  of  processes  to  Uy  b,  c\  we 
now  put  tty  b  and  c  together,  in  the  laboratory,  and  see  if  the 
original  tangle  results.  If  it  does,  the  analysis  was  good ;  if  it 
does  not,  the  analysis  was  defective.  The  most  satisfactory 
syntheses  are,  evidently,  those  in  which  the  terms  ^,  b^  c  are 
sensations,  well  known  and  strictly  defined  in  other  contexts : 
I.  M.  Bentley's  reconstruction  of  the  perception  of  liquidity,  from 
elements  that  are  not  *wet,*  is  an  instance  in  point  (Amer. 
Journ.  of  Psychology,  xi.,  405  ff.).  The  synthesis  that  has  been 
most  discussed  in  the  literature  of  experimental  psychology  is, 
perhaps,  that  of  the  action  consciousness  in  the  *  reaction*  ex- 
periment. In  the  present  case,  of  the  synthesis  of  relief  by 
the  stereoscope,  we  are,  unfortunately,  not  able  to  get  back  to 
ultimate  components  :  our  terms  are  the  plane  pictures,  spatially 
ordered,  on  the  one  hand,  and  the  two  retinas,  connected  with  all 
the  motor  apparatus  of  the  eyeball,  on  the  other.  Neither  term 
is  elemental.  The  pictures  are  obviously  themselves  perceptions, 
mental  formations ;  and  though  we  may  exclude  eye  movement 
(movements  of  the  eyeball  as  a  whole,  and  movements  of  accom- 
modation within  the  eyeball)  by  illuminating  the  stereoscopic 
slide  momentarily,  with  an  electric  spark,  yet  we  cannot  rule  out 
the  motor  dispositions  of  the  eye  which  (on  the  eye-movement 
theory)  may  take  the  place  of  movements  actually  performed. 
The  synthetic  principle  is,  however,  clearly  brought  out. 

Experiment  (  i  ).  —  The  importance  of  practice  in  *  free  ' 
stereoscopy,  such  as  this  experiment  demands,  is  unquestionable. 
The  experimental  psychologist  should  have  his  eyes  so  far  under 
control  that  he  can  fixate  steadily  (not  so  easy  a  matter  as  it 
may  seem  to  be  at  first  thought !),  hold  the  lines  of  vision  par- 
allel in  the  absence  of  a  remote  fixation-point  and  despite  the 
attraction  of  near  objects  in  the  visual  field,  and  keep  the  eye- 
balls in  any  required  *  squinting '  position.      All  three  acquire- 


$  47-    ^^  SjmtfuHc  Experiment  259 

ments  demand  time  and  patience.  It  is  noteworthy  that  (as 
I  icring  says :  Bin.  Sehen,  27)  the  setting  of  the  eyes  for  near  and 
far  fixation  need  not  be  motived  by  any  spatial  idea.  When  one 
wishes  to  squint,  one  need  only  call  to  mind  the  *  peculiar  feeling  * 
of  the  inward-turning  eyeballs,  and  the  squint  is  realised.  When 
ov\e  wishes  to  fixate  an  infinitely  distant  point,  one  need  only 
'  let  the  eyes  go,*  give  up  the  effort  after  clear  vision,  and  *  push 
npnrt '  the  crossed  double  images.  There  is  no  necessity  to 
very  near  object  in  the  first  case,  or  a  very  remote 
object  in  the  second,  natural  as  such  spatial  reference  may  seem. 
Glasses  should  be  dispensed  with,  if  possible.  Sometimes  — 
as  in  the  not  rare  cases  in  which  the  one  eye  is  distinctly  my- 
opic, while  the  other  is  emmetropic  or  slightly  hypermetropic  — 
they  must  be  worn.  O  must  then  see  to  it  that  they  are  cor- 
rectly adjusted,  i.r.,  properly  centred  and  parallel  with  the  fron- 

.1  plane. 
It  is  probably  true,  at  least  of  the  students  that  one  finds  in 

iboratories,  that  convergent  squinting  is  easier  than  the  parallel 
position  of  the  lines  of  regard  (Hering),  though  in  a  mixed 
company  preferences  will  be  found  on  both  sides.  If  the  figures 
of  the  truncated  cone,  drawn  as  directed  in  this  experiment,  are 
handed  round  the  class  room,  the  reports  as  to  the  relief  or 
hollowness  of  the  combined  image  will  differ  with  different 
individuals :  all  have  taken  the  easiest  path  to  combination,  but 
for  some  this  has  meant  far  and  for  others  near  fixation  (Ruete). 
There  can  be  no  doubt  that  near  fixation  gives  the  better  effect 
(Le  Conte);  accommodation  tends  to  follow  fixation,  so  that  the 
outlines  of  the  combined  image  with  parallel  lines  of  regard  are 
blurred  and  indistinct. 

In  view  of  the  importance  of  the  experiment,  and  of  the  ex- 
istence of  these  individual  differences,  it  is  well  to  have  a  num- 
ber of  methods  available.  Hence  we  may  cite  some  of  the 
suggestions  made  by  other  authors,  which  the  Instructor  will 
T^crhaps  prefer  to  the  arrangement  recommended  in  the  text. 

Ve  are  thus  anticipating  the  answer  to  Question  (4).  —  (i)  A 
piece  of  card  or  stiff  paper,  cut  to  fit  the  profile,  and  extending 
out  about  25  cm.  from  the  face  to  meet  the  card,  will  cut  off  the 
lateral  single  images  in  far  fixation,  and  by  confining  each  eye 


26o  Visual  Space  Perception 

to  its  own  field  of  regard  will  assist  O  to  obtain  and  maintain 
the  required  position  of  the  lines  of  regard.  Notice  that,  if  the 
lines  of  regard  are  set  in  the  parallel  position  beforehand,  and 
the  stereograms  then  interposed  between  the  eyes  and  the  re- 
mote fixation-point  (this  is  the  method  usually  adopted  by  begin- 
ners), fusion  is  easier  when  the  card  is  brought  down  from  above 
than  when  it  is  brought  up  from  below  the  eyes.  In  near  fixa- 
tion, two  small  side  screens,  held  upon  a  cross  wire  on  which 
the  near  fixation-mark  is  fastened,  replace  the  profile  paper. 
(2)  For  distant  fixation,  the  figures  may  be  drawn  upon  glass 
or  (more  easily)  upon  celluloid,  instead  of  card.  The  observer 
is  thus  able  actually  to  look  through  the  figures  at  the  remoter 
point.  Martius-Matzdorff  (Stereoskopie,  8)  advises  the  begin- 
ner to  paste  the  figures  on  a  window  pane,  and  look  through 
them  at  some  fixed  object  in  the  street.  Sanford  (Lab.  Course, 
277)  recommends  a  glass  slide,  with  gummed  kindergarten  rings 
and  dots  laid  on.  Care  must  of  course  be  taken  that  the  dis- 
tance between  the  centres  of  the  figures  does  not  exceed  the 
interocular  distance  (Wundt,  Phys.  Psych.,  ii.,  206  f.).  (3) 
Helmholtz  suggests  the  use  of  blackened  tubes,  and  of  simple 
stereoscopic  drawings,  whose  centres  are  separated  by  less  than 
the  interocular  distance  (Optik,  784).  Take  two  tubes  of  black 
cardboard,  20  cm.  in  length  and  3  cm.  in  diameter.  Make  two 
cardboard  rings,  i  cm.  in  width,  to  slide  snugly  over  these  tubes. 
Draw  the  two  figures  of  the  slide  on  a  reduced  scale  (outer  cir- 
cle 2  cm.  in  diameter)  upon  architects'  paper,  and  paste  them 
over  the  rings.  Fit  the  rings,  or  caps  as  they  now  are,  over  the 
ends  of  the  tubes,  with  the  figures  in  their  appropriate  positions, 
and  hold  the  open  ends  of  the  tubes  to  the  eyes.  Bring  the 
figure-ends  of  the  tubes  together,  till  the  drawings  fuse.  Evi- 
dently, if  a  number  of  rings  and  figures  be  prepared,  these  and 
the  tubes  constitute  a  form  of  stereoscope.  Its  chief  limitation 
is  the  small  size  of  the  pictures  that  can  be  combined.  Miin- 
sterberg's  Pseudoptics  (p.  xxxiii.  above)  contains  two  tubes  and 
a  set  of  caps. 

The  Figure  shows  two  early  devices  of  Wheatstone's  (Phil.  Trans.  Royal 
Soc.  London,  1838,  373),  for  far  and  near  fixation  respectively.  The  latter 
maybe  compared  with  Elliot's  box  stereoscope  (described  1839:  see  Brew- 


§  47     /  '"*  SUreoscopy  261 

ster.  Stereoscope) ;  a  needle  is  supposed  to  stand  at  the  point  of  intersection 
of  the  lines  R.  L. 

Le  Conte  (Sight.  139)  recommends  a  skeleton  truncated  cone  of  wire,  in 
place  of  the  cardboard  cone  prescribed  in  the  text.    This  is  so  fiur  good  that 
the  lines  to  be  drawn  are  all  made  directly  visible  to  the  student ;  but  it  is  a 
question  whether  the  gain  in  simplifi- 
cation b  not  more  than  balanced  by  11      k 
the  resulting  mechanical  nature  of  the 
drawing.     The  student  is  not  called 
upon  to  see  critically. 


Questions.  — ( i )  Each  of  the 
two  figures  is  seen  by  both  eyes, 
so  that  there  are  four  single  im- 
ages before  combination,  and  two  yvi,  57. 
single  images  and  a  total  (com- 
bined) image  after  combination.  Let  us  number  the  single 
images  i,  2,  3,  4  from  left  to  right.  Then,  in  far  fixation, 
I  and  3  belong  to  the  right,  2  and  4  to  the  left  eye;  in 
near  fixation,  i  and  3  belong  to  the  left,  2  and  4  to  the 
right  eye.  Nos.  2  and  3  combine ;  nos.  i  and  4  are  therefore 
left  outstanding. 

(2)  The  difference  of  size  will,  in  all  probability,  be  remarked 
by  all  students  in  the  one  case  or  the  other,  though  not  with 
equal  ease  in  both  cases,  and  perhaps  not  at  all  in  one  of  them. 
Wherever  it  is  remarked,  the  combined  image  and  the  lateral 
single  images  do  not  lie  in  the  same  plane.  In  far  fixation,  the 
combined  image  seems  to  be  farther  off  than  the  other  two. 
There  is  a  temptation  to  say,  at  the  moment  of  fusing,  that  the 
frustum  of  the  cone  has  leapt  towards  you  from  the  plane  of 
the  card.  This  is  not  accurate :  for  the  base  of  the  cone  has 
also  left  the  plane  of  the  card,  and  the  solid  figure  stretches 
away  from  you.  In  near  fixation,  the  central  image  approaches 
the  observer.  There  is  a  temptation  to  say  that  the  base  of  the 
cone  has  shot  back ;  in  reality,  the  whole  solid  figure  has  come 
in  towards  you.  In  other  words,  the  combined  image  has  tended, 
in  both  cases,  towards  the  point  of  fixation.  This  may  be  seen 
very  prettily  if  the  card  be  moved  out,  after  the  eyes  have  been 
permanently  set  for  near  fixation.  The  hollow  cone  lies  sus- 
pended in  mid-air  between  ^s  eyes  and  hand. 


262  Visual  Space  Perception 

Now,  if  an  object  occupies  the  same  amount  of  space  as  an- 
other object,  and  yet  is  farther  off  than  this  other,  it  must  be 
the  larger  of  the  two.  This  is  our  first  case.  If,  on  the  other 
hand,  an  object  occupies  the  same  amount  of  space  as  another 
object,  and  yet  is  nearer  to  us  than  this  other,  it  must  be  the 
smaller  of  the  two.  This  is  our  second  case.  All  three  images 
subtend  the  same  visual  angle,  in  both  instances ;  but  they  sub- 
tend this  angle  at  different  distances  from  the  eye,  and  appear 
of  correspondingly  different  sizes.  —  G.  T.  Ruete,  Das  Stereo- 
skop,  2te  Aufi.,  67  f.     Cf.  Wundt,  ii.,  201  ;  Aubert,  628. 

On  the  localisation  of  the  combined  image  at  the  distance  of  the  apparent 
point  of  regard,  see  Sanford,  Lab.  Course,  exps.  2\\  a,  212  b.  A  striking 
experiment  (Hermann  Meyer)  may  be  performed  with  an  ordinary  open-work 
cane-bottomed  chair.  Hold  up  the  chair,  the  cane  bottom  parallel  with  the 
frontal  plane,  at  about  the  distance  of  the  near  point  of  accommodation. 
Combine  the  octagons  of  the  mesh-work  by  fixating,  first,  a  remote  object, 
and  then  an  imaginary  nearer  object.  In  the  former  case,  the  somewhat  in- 
distinctly seen  screen  lies  beyond  the  chair,  —  not,  certainly,  so  far  away  as 
the  distant  tree  or  whatever  it  may  be  that  forms  the  object  of  fixation,  but 
still  a  great  deal  farther  off  than  12  cm. ;  in  the  second  case,  the  screen  comes 
out  from  the  circular  wooden  rim,  so  that  the  chair  bottom  appears  to  be 
highly  convex,  its  convexity  towards  the  eyes.  The  comparative  nearness  of 
the  screen  with  remote  fixation  is  due  to  the  counter  action  of  secondary  cri- 
teria.    See  Brewster,  Stereoscope,  90  ff. ;  Aubert,  614;  Helmholtz,  798  f. 

(3)  So  far  as  the  relation  of  the  double  images  to  their  re- 
spective eyes  is  concerned,  the  drawings  should  present  no  diffi- 
culty. —  In  the  three  figures  here  given  the  combined  image  is 
placed  always  at  the  fixation-point.  Fig.  58  shows  that,  if  the 
point  of  fixation  lie  behind  the  two  stereoscopic  drawings,  the 
corresponding  points  give  a  more  remote  combined  image, 
the  farther  apart  they  are  in  the  plane  of  the  card  :  i.e.,  what 
is  drawn  raised  is  seen  raised,  and  what  is  drawn  depressed  is 
seen  depressed.  Fig.  59  shows,  conversely,  that  if  the  point  of 
fixation  lie  before  the  slide,  the  corresponding  points  give  a  more 
remote  combined  image,  the  nearer  together  they  are  in  the 
plane  of  the  card :  i.e,y  what  is  drawn  raised  is  seen  depressed, 
and  what  is  drawn  depressed  is  seen  raised.  The  same  result 
could,  evidently,  have  been  obtained  if  we  had  cut  the  slide  of 
Fig.  58  in  halves,  interchanged  the  halves,  and  fixated  a  remote 


§  47'    Wktatsttme^s  SUreoscope  263 

point.  Or,  we  may  bring  the  slide  of  Fig.  59  back  again  to 
normal  depth  values  by  cutting  it  in  halves,  interchanging  the 
halves,  and  maintaining  the  near  fixation-point.  We  then  have 
Fig.  6a     See  Ruete,  Das  Stereoskop,  65  ff. 


Fia  58.  Fig.  59.  Fia  60. 

(4)  The  answer  to  this  question  has  been  given  above,  pp.  259 
f .  The  student  may  very  well  think  of  ( i )  screens  and  artificial 
fixation-points ;  (2)  transparent  slides ;  (3)  tubes.  Another, 
much  less  obvious  device,  is  Miinsterberg's  stroboscopic  stereo- 
scope, figured  and  described  in  the  Psychol.  Review,  i.,  1894, 
56  ff. 

The  Stereoscope.  — The  student  must  be  familiar  with  Wheat- 
stone's  reflecting  stereoscope,  as  well  as  with  Brewster's  refract- 
ing stereoscope.  We  will  begin  with  the  former,  which  also  has 
priority  in  date  of  invention. 

The  first  mention  of  Sir  Charles  Wheatstone's  (i 802-1 875) 
discovery  occurs  in  1833,  in  the  third  edition  (p.  288)  of  the 
Outlines  of  Human  Physiology  by  H.  Mayo,  a  colleague  of 
Wheatstone's  at  King's  College,  London.  Wheatstone's  own 
description  of  the  reflecting  stereoscope  is  to  be  found  in  the 
Phil.  Trans,  for  1838,  p.  375  ;  Figs.  61  and  62  represent  a  front 
view  and  a  plan  of  the  instrument.  The  account  runs  in  sub- 
stance as  follows.  *  Two  plane  mirrors,  about  10  cm.  square,  are 
framed,  and  so  adjusted  that  their  backs  form  an  angle  of  90°. 
They  are  fixed  by  their  common  edge  to  a  vertical  board,  cut  away 
to  allow  the  placing  of  the  eyes  before  the  two  mirrors.  The  base 
consists  of  two  sliding  boards,  each  of  which  carries  an  upright 


264 


Visual  Space  Perception 


side-piece ;  these  side-pieces  may  thus  be  removed  to  different  dis- 
tances from  the  mirrors.    To  secure  equal  amounts  of  movement,  a 

right  and  left  handed  wooden 
.ff     13,  ^^-^  screw  is  passed  through  the 

lower  parts  of  the  side-pieces. 
The  side-pieces  further  carry 
panels,  to  which  the  diagrams 
may  be  affixed  in  such  a 
way  that  their  corresponding 
horizontal  lines  are  on  the 
same  level ;  the  panels  slide 
backwards  and  forwards  in 
grooves  on  the  side-pieces.' 
The  optical  principle  of  the 
instrument  is  clear  from  Fig. 
63.  .^.^  are  the  two  mirrors; 
BB  the  two  panels ;  ccc  and 
c'c'c'  the  two  diagrams.  The 
Figs.  61,  62.  ^^Y^  ^^^^  upon  the  eyes  DD^ 

as  if  they  came  from  EE'.  In 
other  words,  we  see  at  EE'  the  combined  (virtual)  image  of  the 
two  figures.     Ruete,  Das  Stereoskop,  71  f. 


Fig.  63. 


§  47'    Wheatstone* s  Sttreoscop^ 


a65 


Figure  64  shows  the  later  form  of  Wheatstone's  reflecting  stere- 
oscope (Phil.  Trans.,  1852.  3).  The  sliding  base-boards  are  here 
replaced  by  wooden  arms  moving  round  a  common  centre  below 
the  line  of  junction  of  the  mirrors.  The  panels  are  run  in  and 
out  on  slides ;  the  side-pieces  are  thus  done  away  with.  The 
diagram  cards  slip  back  and  forth  in  grooves  in  the  panels.  "  By 
the  arrangement  described,  the  reflected  pictures  are  always  per- 
pendicular to  the  optic  axes,  and  the  corresponding  points  of  the 
pictures,  when  they  are  exactly  similar,  fall  upon  corresponding 
points  of  the  retinae.     The  instrument  has  an  adjustment  for 


Fig.  64. 

otherwise  inclining  them  if  it  be  required."  Since  the  mirrors 
are  fixed,  this  statement  must  mean  that  the  panels  can  be  ro- 
tated about  vertical  axes,  as  in  modem  forms  of  the  instrument. 

Sanford  (Lab.  Course,  408  ff.)  gives  specifications  for  the  construction  of 
a  combined  Wheatstone  stereoscope  and  Helmholtz  telestereoscope.  The 
author  has  had  this  instrument  built,  and  it  works  satisfactorily ;  though  some 
of  the  moving  parts  might  with  advantage  be  made  heavier.  The  cost  is  about 
$15.00.  The  design  embodies  Hering's  improvement  upon  Wheatstone's 
model,  that  the  lateral  arms  turn,  not  about  a  common  centre,  but  about 
centres  lying  in  the  same  vertical  lines  as  the  centres  of  rotation  of  the  eyes 
(Hermann's  Hdbch.,  393). 

Ad  admirable  instrument,  of  Hering's  devising  (built  by  R.  Rothe),  b 
figured  and  described  by  F.  Hillebrand  in  the  Zeits.  f.  Psychol.,  v.,  1893,  38 
and  Plate  i. 

The  Wheatstone  stereoscope  should  always  be  so  constructed  that  the  panels 
are  replaceable  by  stands  to  take  wire-modeb  instead  of  cardboard  slides.  The 
binocular  image  of  two  similar  models  will  show  relief,  converted  relief,  or  a 
plane  picture,  according  to  the  position  of  the  objects :  Wheatstone,  1838, 378. 
For  a  device  to  throw  the  mirror  images  of  a  plane  picture  into  relief,  see 
Wheatstone,  1838,  378  and  Fig.  21. 

Let  US  see,  now,  how  the  apparatus  works.  The  two  diagrams 
to  be  combined  are  slid  into  the  panels.     The  arms  are  set  in 


266  Visual  Space  Perception 

the  same  straight  line,  and  the  panels  at  an  angle  of  45°  to  the 
mirrors. 

Push  the  slides  well  out  upon  the  arms,  at  equal  distances  from 
the  mirrors.  Move  the  arms  gradually  outwards,  away  from  you, 
till  the  images  combine.  The  position  recommended  by  Wheat- 
stone  as  starting-point  is  that  in  which  the  binocular  image 
appears  of  its  natural  size,  i.c.y  of  the  size  of  the  diagrams. 
Any  position  will  do,  in  which  the  eyes  combine  the  diagrams 
easily  and  without  strain. 

Move  the  arms  still  farther  out.  The  magnitude  of  the  retinal 
images  remains  constant,  but  an  increasing  convergence  is  re- 
quired if  combination  is  to  be  maintained.  Notice  that  the 
binocular  image  seems  to  grow  smaller.  Move  the  arms  in 
again,  towards  you.  Convergence  is  lessened,  until  (when  the 
arms  are  in  the  same  straight  line)  the  lines  of  regard  are 
parallel.  There  is  still  no  change  in  the  size  of  the  retinal 
images.  Notice,  however,  that  the  binocular  image  seems  to 
grow  larger. 

Set  the  instrument  again  for  easy  combination.  Move  the 
slides  steadily  in  towards  the  mirrors.  Convergence  remains 
constant ;  the  size  of  the  retinal  images  is  increased.  Notice 
that  the  binocular  image  seems  to  have  come  nearer.  Move  the 
slides  outwards.  Convergence  is  still  constant ;  the  size  of  the 
retinal  images  is  decreased.  Notice  that  the  binocular  image 
seems  to  have  travelled  farther  away. 

These  two  experiments  are  evidently  of  high  theoretical  im- 
portance. In  the  former,  we  have  constancy  of  retinal  image, 
constancy  of  accommodation,  change  of  convergence.  The  ap- 
parent distance  of  the  binocular  image  remains  constant  for 
ordinary  observation,  though  careful  examination  may  show  that 
it  has  changed.  At  any  rate,  the  principal  and  obvious  result  is 
that  the  binocular  image  varies  in  magnitude.  In  the  latter 
experiment,  we  have  constancy  of  convergence,  change  of  retinal 
image,  change  of  accommodation.  The  apparent  size  of  the 
binocular  image  remains  constant  for  ordinary  observation, 
though  it  is  not  difficult  to  perceive  the  changes  in  size  as  such. 
The  principal  and  obvious  result,  however,  is  that  the  binocular 
image  varies  in  distance.     What,  then,  are  the  criteria  that  make 


{  47*    Wkeaiston/s  SUrtoscapt  267 

against  apparent  change  of  distance  in  the  first,  and  make  for  it 
in  the  second  experiment? — Wheatstone,  Phil.  Trans.,  1852,  3  f. ; 
Helmholtz,  795  (a  summary  and  not  very  exact  account  of  the 
experiments) ;  Sanford,  Lab.  Course,  285,  exp.  2 1 7. 

Combination  with  divergent  lines  of  regard  may  be  secured  by  bringing 
the  arms  in,  very  slowly  and  steadily,  beyond  the  position  of  parallel  vision. 
HelmholtSy  using  a  series  of  similar  figures  the  distance  between  whose  centres 
was  gradually  increased,  found  himself  able  to  combine  divergently  points  93 
mm.  apart,  while  his  interocular  distance  was  68  mm.  (800) .  Cf.  Hering,  Her- 
mann^ Hdbch.,  507 ;  Sanford,  Lab.  Course,  389,  exp.  219  <i.  We  cannot  here 
enter  upon  the  special  problem  of  divergent  stereoscopic  vision.  It  may  be 
remarked,  howe\*er.  that  the  distance  between  conjugate  points  of  the  pictures 
in  stereoscopic  slides  (Brewster's  instrument)  is  often  or  even  usually  greater 
than  the  interocular  distance.  This  fact  has  been  interpreted  to  mean  that  the 
lines  of  regard  must  be  strongly  converged  (crossed  on  the  hither  side  of  the 
stereograms)  as  we  look  into  the  instrument :  cf.  Ruete,  Das  Stereoskop,  66, 
and  the  diagram  on  p.  69.  The  interpretation  is,  doubtless,  correct  as  regards 
the  majority  of  instruments  and  slides  used  in  laboratories  for  scientific  pur- 
poses. W.  LeC.  Stevens  has,  however,  recently  shown,  by  measurements  of 
the  foreground  inter\als  in  commercial  slides  and  the  deviating  power  of  the 
lenticular  prisms  in  commercial  instruments,  that  cases  are  not  uncommon  in 
which  the  rays  from  conjugate  stereogram  points  are  not  quite  parallel  after 
emergence  from  the  prisms,  so  that  the  eyes  must  diverge  somewhat  to  receive 
them.  Positions  of  divergence  are  especially  to  be  looked  for  **  among  young 
persons  whose  interocular  distance  is  small,  whose  eyes  are  normal,  and  whose 
power  of  accommodation,  both  focal  and  axial, 
is  thus  large ""  (Amer.  Joum.  of  Science,  3  Series, 
jorii.,  1881,  360,  444). 

We  have  not  yet  availed  ourselves  of  the  rota- 
tion of  the  panels  about  vertical  axes.  The  fol- 
k>wing  experiment  (LeC.  Stevens)  is  instructive. 
Set  the  stereoscope  for  easy  combination.  Place 
in  the  panels  two  exactly  similar  slides,  drawn  as 
in  Fig.  65.  Turn  the  panels  in  such  a  way  that 
they  form  a  dihedral  angle,  opening  towards  the 
observer.    The  binocular  image  of  the  central  pjQ^  5e. 

drdes  is  that  of  a  convex  surface ;  that  of  the 

two  upper  circles,  an  ellipse  whose  upper  vertex  is  farther  from  and  its  lower 
vertex  nearer  to  the  eyes ;  and  that  of  the  lower  two  circles,  an  ellipse  of  reversed 
obliquity.  Turn  the  panels,  now,  in  such  a  way  that  their  angle  narrows  towards 
the  observer.  The  convex  becomes  a  concave  surface,  and  the  inclination 
of  the  ellipses  is  the  opposite  of  that  in  the  former  experiment.  For  most 
observov,  the  concavity  is  more  marked  and  more  readily  perceived  than  the 


268 


Visual  Space  Perception 


convexity.  Let  the  student  work  out  an  explanation  of  the  phenomena.  — 
Amer.  Journ.  of  Science,  3  Series,  xxiii.,  1882,  298  ff.,  359;  xxiv.,  1882,  243; 
J.  Le  Conte,  tind.y  xxxiv.,  1887,  103. 

We  have  now  to  consider  the  refracting  stereoscope  of  Brewster 

( 1 781-1868),  which  has  driven  the  reflecting  stereoscope  out  of 

general  use.     There  seems  to  be  no  doubt  that  Wheatstone 

invented  a  prism  stereoscope  before  Brewster  thought  of  it  (see 

,  ,  The  Edinburgh  Re- 

^$. 1  ^^^^'    ^^^'^     ^^58, 

/jVv^  /fj;  cviii.,455;  Encycl. 

.• ;  W  //  I  ♦  Britannica,     ninth 

/  !    \  \  /  /    j  \  edn.,    art.    Stereo- 

/  \     \  \  /  /     I  '.  scope):   Brewster's 

/    i       \    \      /    /       i    \  substitution  of  two 

/     i        \     V     /        I     \  semi-double-convex 

/     1  \  /  \^  /         j     I  lenses  for  the  two 

/      1  X       X  I      '.  prisms,    and    simi- 

lar  improvements, 
date  theoretically 
from  1843-4  (pa- 
pers read  to  the 
Royal  Soc.  of  Ed- 
inburgh, Jan.,  1843, 
April,  1844),  prac- 
tically from  1849- 
50  (Encycl.  Brit., 
art.  Brewster). 

Question  (5).  — 
The  accompanying 
diagram  shows  the 
optical  principles  of 
the  instrument.  G  and  G'  are  the  lenticular  prisms  for  the 
left  and  right  eyes  respectively.  AB  and  A^B'  are  the  stereo- 
grams. The  ray  Ab  comes  to  the  eye  in  the  direction  bdy 
instead  of  bc\  it  seems,  therefore,  to  come  from  the  point  AA'. 
The  ray  A'b'  comes  to  the  eye  in  the  direction  b'd'y  instead  of 
b'c'y  it  too,  therefore,  seems  to  come  from  the  point  AA'.  The 
same  thing  holds  of  rays  from  B  and  B\  and  of  the  point  BB'. 


A 

/ 

f\  ■ 

/       A' 

\ 

[         \ 

oB' 

\    A 

\^      1            \  / 

>  D 

V            '   /  / 

\  / 

\  / 

\\    '            1  / 

\           ' '/ 

X 

/ 

\\'            / 

/\  / 

1 

y^ 

\     /'; 

/    A  ^ 

1 

1 
1 

\ 

V    \ 

1       /    \  '' 

1 

* 

1    /     \         ' 

u_ 

/    y 

1 

N 

\ 

;/     \ 

/ 

v;^ 

^ 

y    ,'■ 

\ 

V  I 

1 

,71 

/   1 

1  V 

A  » 

l\\ 

'  i\ 

K\ 

/  /  ' 

/  \ 

»'  \ 

\  V 

/'     \ 

/  1 

/        '    * 

« 

1 

1 

1    \ 
1     \ 
1      ^ 

'c' 

.'1 

Fig.  66. 


{  47*   Bnewsttr's  St€r€OScop€  269 

Wc  accordingly  sec  the  binocular  (enlarged,  virtual)  image  at 
AA'Bff,  C  is  the  central  screen.  If  it  were  absent,  we  should 
8CC  (besides  the  binocular  image  ^^4'^-^)  the  figure  AB  with 
the  right,  and  A'B*  with  the  left  eye.  —  Ruete,  Dls  Stereoskop, 
72  ff. 

The  hood  of  our  instrument  serves  to  exclude  lateral  light. 
**  The  exclusion  of  all  light  from  the  eyes,**  writes  Brewster,  **  and 
of  every  other  light  from  the  picture  but  that  which  illuminates 
it,  is  essentially  necessary  to  the  perfection  of  stereoscopic 
vision"  (Stereoscope,  71).  The  bar  allows  us  to  adjust  the 
instrument  for  eyes  of  difiFerent  focal  lengths.  The  cross  upright 
at  the  end  of  the  screen  allows  us  to  shorten  the  screen  itself, 
and  so  to  get  a  wide  range  of  movement  along  the  bar.  If  it 
were  not  for  the  upright,  screens  of  different  lengths,  extending 
to  meet  the  slide  cards,  would  be  required  for  difiFerent  eyes. 
The  prisms,  as  is  plain  from  the  diagram,  bring  it  about  that, 
despite  the  convergence  of  the  lines  of  regard  as  one  looks  into 
the  instrument,  the  stereograms  image  themselves  on  the  retinas 
approximately  as  they  would  do  if  the  lines  of  regard  were 
parallel  The  lenticular  prisms  have  the  further  advantages  of 
(a)  enlarging  the  binocular  image,  and  {b)  serving  to  correct 
accommodation,  which  is  normally  insufficient  for  the  close 
proximity  of  the  pictures,  i.e.,  making  the  binocular  image  more 
distinct.  —  Hering,  Hermann's  Hdbch.,  586 ;  Helmholtz,  785  ; 
Aubert,  623. 

In  Brewster's  own  model,  we  have  to  note  the  following  features,  {a)  The 
lenses  are  held  in  tubes,  which  move  up  and  down,  for  eyes  of  different  focal 
lengths.  The  same  result  is  obtained  in  our  instrument  by  the  movement  of 
the  slide  carrier  along  the  bar.  {b)  The  lenses  are  prevented  from  turning  in 
their  tubes  by  a  pin  (but  see  Hering,  Hermann's  Hdbch.,  $86).  In  our 
instrument  the  lenses  are  fixed,  once  and  for  all.  {c)  The  lenses  can  be 
moved  together  and  apart,  for  the  accommodation  of  observers  with  different 
interocular  disUnces.  This  is  a  great  advantage.  The  author  has  found  a 
variation  in  these  distances  of  61  to  68  mm.  {d)  Convex  or  concave  lenses, 
coloured  glasses,  etc.,  can  be  introduced  below  the  lenses  of  the  instrument,  for 
the  benefit  of  longsighted  and  shortsighted  observers,  etc.  Spectacles,  carefully 
adjusted,  answer  the  same  purpose  (Stereoscope,  66  f.).  —  The  *  hood  stereo- 
scope,' used  in  our  experiments,  was  devised  by  O.  W.  Holmes  in  1861 :  see 
art.  Stereoicopey  by  W.  LeC.  Stevens,  in  Johnson's  Universal  Cydopxdia. 


270  Visual  Space  Perception 

What  are  the  comparative  merits  of  the  two  instruments  ?  We 
shall  get  a  full  tale  of  the  defects  of  the  reflecting  stereoscope  if 
we  take  Brewster's  criticism  of  it  (Stereoscope,  62  f.).  Brewster 
makes  the  following  points,  {a)  The  reflecting  stereoscope  is 
rather  a  clumsy  and  unmanageable  apparatus  than  an  instrument 
for  general  use.  This  is  true :  Wheatstone's  stereoscope  is, 
as  Ruete  says,  an  *  uncomfortable '  instrument.  The  required 
solidity  and  ease  of  manipulation  could  be  obtained  by  making 
certain  parts  of  metal ;  but  the  cost  would  thereby  be  very 
greatly  increased,  {b)  There  is  loss  of  light  by  the  reflection 
from  the  mirrors,  {c)  There  is  a  separation  of  the  image  pro- 
duced by  the  glass  surface  from  the  more  brilliant  image  produced 
by  the  metallic  surface,  {d)  There  are  four  refractions  in  each 
mirror,  and  the  light  is  transmitted  through  twice  the  thickness 
of  the  glass.  These  three  objections  are  of  little  weight,  {e)  The 
eye  and  all  parts  of  the  apparatus  are  exposed  to  light.  This  is  a 
good  point :  Helmholtz,  785.  (/)  There  is  left-right  conversion 
of  the  half  slides  by  reflection.  This  is  true,  but  the  fact  need 
not  lead  to  any  confusion,  {g)  Transparent  half  slides  could 
be  used  only  with  great  inconvenience,  as  two  lights  would  be 
needed.  (//)  The  size  of  the  pictures  that  can  be  introduced  is 
strictly  limited.     These  two  arguments  are  unimportant. 

Wheatstone,  on  the  other  hand,  declares  (Phil.  Trans.,  1852, 
5)  that  "there  is  no  form  of  the  instrument  which  has  so  many 
advantages  for  investigating  the  phenomena  of  binocular  vision 
as  the  original  reflecting  stereoscope.  Pictures  of  any  size  may 
be  placed  in  it,  and  it  admits  of  every  kind  of  adjustment."  This 
last  remark  touches  the  essential  point.  We  have  seen  that  in 
the  Wheatstone  instrument  there  is  a  natural  conjunction  of 
accommodation  and  convergence,  while  we  can  vary  convergence 
without  change  of  the  retinal  image,  and  vary  the  retinal  image 
without  change  of  convergence.  We  can  also  induce  divergent 
positions  of  the  lines  of  regard.  There  are,  indeed,  a  number  of 
scientific  experiments  that  can  be  performed  with  this  apparatus 
(Hering's  haploscope  is  practically  the  same  thing),  but  that  can- 
not be  performed  with  the  Brewster  stereoscope.  Moreover,  the 
limits  of  size  for  pictures  are  undoubtedly  smaller  in  the  latter 
instrument,  unless  one  gives  up  the  advantage  of  compendious- 


{  47-    RfflecttHg  and  Refracting  SUrtoscopts  271 


ness  and  portability  altogether ;  the  lenses  are  as  a  rule  very  far 
from  achromatism  ;  and  the  plan  of  the  instrument  is  less  simple, 
even  when  full  weight  is  given  to  the  left-right  reversal  of  the 
stereograms  in  the  reflecting  stereoscope.  On  the  whole,  the 
preference  must  with  Wundt  and  Hering  be  accorded  to 
the  Wheatstone  apparatus.  The  laboratory  should  therefore 
possess  this,  for  demonstration  and  investigation  ;  the  refracting 
stereoscopes  are  prescribed  for  our  experiments  simply  because 
their  cheapness  and  compactness  make  it  possible  to  procure  a 
number  of  them  for  class  purposes. 

There  are  very  many  forms  of  stereoscope.     Figs.  67, 68  and  69  show  three 
curiosities  in  this  line,  drawn  from  Brewster's  diagrams  (The  Stereoscope,  109, 


L 

Fig.  69. 


113,  119).  Binocular  relief  is  obtained  in  Fig.  67  by  the  use  of  two  similar 
figures  and  a  single  mirror ;  in  Fig.  68,  by  the  use  of  a  single  figure  and  a 
total-reflection  prism ;  in  Fig.  69,  by  the  use  of  two  stereographic  figures  and 
a  single  small-angled  prism.  An  instrument  that  deserves  special  mention  is 
Melmholtz'  telestereoscope,  an  apparatus  which,  as  we  said  above,  is  combined 
with  Wheatstone's  stereoscope  in  Sanford^s  design.  The  telestereoscope  ex- 
aggerates binocular  relief,  and  is  therefore  particularly  well  adapted  for  bringing 
out  the  tridimensionality  of  very  remote  objects,  which  in  ordinary  vision  show 
little  or  nothing  of  their  solidity.  The  simpler  and  earlier  model  is  given  in 
fig.  70.  LR  are  the  two  eyes ;  M\f  two  small  plane  mirrors,  set  at  an  angle 
of  90^  The  sides  of  the  instrument  consist  of  two  larger  mirrors,  of  which  the 
one  can  be  turned  about  a  vertical  and  the  other  about  a  horizontal  axis.  The 
course  of  the  rays  is  indicated  by  the  dotted  lines  above  L  and  R.  It  is  clear 
that  the  eyes  see  the  binocular  mirror  image  as  if  they  were  placed  at  L'R^ 
/v.,  at  a  distance  stxy  much  larger  than  the  interocular.  ~  Helmholtz,  793  f., 
622  (. 


2/2 


Visual  Space  Perception 


The  more  complicated  form  of  the  apparatus  is  figured  by  Helmholtz,  831, 
and  is  represented  in  schematic  form  in  Fig.  71.  —  Ruete,  Das  Stereoskop,  83. 

To  use  the  telestereoscope,  we  have  only  to  place  it  on  the  sill  of  an  open 
window,  or  on  a  balcony,  that  commands  a  landscape  of  fair  depth  (it  is  well 


Fig.  70. 


if  the  lines  of  distance  in  the  landscape  are  clearly  marked  by  rows  of  trees, 
low  hills,  more  distant  mountains,  etc.),  and  to  vary  the  positions  of  the  mirrors 
until  the  monocular  images  combine  without  strain.  When  the  principal  ob- 
jects in  the  landscape  are  remote  and  the  lines  of  regard  parallel,  the  binocular 
image  has  the  appearance  of  "  a  very  pretty  and  accurate  model "  (Helmholtz). 
Landscape-slides  for  the  Brewster  stereoscope,  if  their  two  views  were  photo- 


/ 


M 


M 


lif 


Ac  71.  —  Z,  JRf  the  two  eyes;   P,  P,  two  totally  reflecting  prisms;  J/,  M,  the  lateral 
mirrors.     The  dotted  lines  indicate  the  direction  of  the  rays. 


graphed  from  points  separated  by  more  than  the  interocular  distance,  may 
give  the  same  model-effect. 

Another  useful  laboratory  instrument  is  the  Ludwig  tropostereoscope  (Fig. 
72).  Two  metal  tubes  20  cm.  long  and  3  cm.  in  diameter,  blackened  within, 
are  attached  to  a  handle  in  such  a  way  that  the  open  ends  can  be  brought 
together  or  moved  apart,  to  match  the  interocular  distance.     The  remote  ends 


{  47*    SUrtoscopU  Siidts  273 

of  the  tubes  aie  mppUed  with  threaded  capt,  within  which  coloured  glass  dia- 
grams, metal  discs  with  radii  cut  out,  etc.,  can  be  fitted.    The  caps  are  geared 
together,  so  that  the  diagrams  or  radii  can  be  brought  into  the  required  stereo- 
graphic  positions,  their  relief  converted,  etc. 
The  tropostereoscope   is  evidently  a  refined 
form   of   the    tube    stereoscope    referred    to 
above,  p.  360,  and  requires  £sr  fixation. 

Experiment  (2). — The  slides  here 
figured  should,  if  time  permit,  all  be 
made  by  the  student,^  and  preserved 
(like   the  kymograph  tracings)  either     p,^,     _p^,j 
in    the   note-book    or   in    a    portfolio.  Mk.34.       ' 

The  best  published  set  of  stereoscopic 
slides  for  the  Brewster  instrument  is,  probably,  the  set  of  36 
issued  by  J.  Martius-Matzdorff  (Die  interessantesten  Erschei- 
nungen  der  Stereoskopie,  in  36  Figuren  mit  erlauterndem  Text, 
2d  edn.,  1889 :  VVinckelmann  &  Sbhne,  Berlin.  The  same  author 
and  publisher  issue  a  packet  of  Zwolf  Darstellungen  des  stereo- 
skopischen  Glanzes  an  Krystallformen,  n.  d.). 

The  selected  slides  are  discussed  by  the  following  authors  : 

I.,  Wheatstone,  1838,  Fig.  11 ;  Ruete,  49. 
11.,  Ruete,  48;  Helmholtz,  877;  Wundt,  ii.,  194;  also  Human  &  Animal 

Psych.,  187. 
\\U  Wheatstone,  1838,  Fig.  12. 
I\'.,  Wheatstone,  1838,  Fig.  10;  Hering,  Beitrage,  86;  Wundt,  Human  & 

Animal  Psych.,  187. 
v.,  Martius-Matzdorff,  no.  19. 
VI.,  Martius-Matzdorff,  no.  20;  Wundt,  ii.,  180. 
VII.,  Martius-Matzdorff,  no.  22;  Wundt,  it,  182;  Human  &  Animal  Psych., 

185. 
VIII.,  Martius-Matzdorff,  no.  23. 
IX.,  Martius-Matzdorff,  no.  24. 
X.,  Martius-Matzdorff,  no.  26. 
XI.,  Martius-Matzdorff,  no.  27. 
XII.,  Martius-Matzdorff,  no.  29. 
XI I U  Martius-Matzdorf!;  na  32. 
XIV.,  LeConte,  Sight,  137. 
XV.,  in  the  Cornell  Laboratory  series,  is  a  photograph  of  the  interior  of  the 
railway  bridge  at  Cologne. 

>  If  time  does  ooC  pennit  of  this,  the  student  should  at  least  make  slides  i.,  ii.,  iv., 
xriii^  xix.,  xxi.,  xxv.,  xxviiL.,  uuu,  xxxv.  and  the  colour  slides. 

T 


274  Visual  Space  Perception 

XVI.  is  a  lunar  photograph  by  Warren  de  la  Rue,  London. 
XVII.  is  a  photograph  of  ruins  of  temple,  Sphinx  and  Great  Pyramid, 
published  by  Strohmeyer  &  Wyman,  New  York.     (These  three 
slides  chance  to  be  the  best  of  the  Cornell  collection  for  the 
purposes  of  this  experiment.     Every  laboratory  will,  doubtless, 
possess  a  large  number  that  will  answer  the  purpose  more  or 
less  completely.) 
XVIII.,  Hering,  Beitrage,  84. 
XIX.,  Hering,  Beitrage,  85. 
XX.,  Hering,  Beitrage,  86. 

XXI.,  Helmholtz,  881 ;  Wundt,  ii.,  193  ;  Human  &  Animal  Psych.,  187. 
XXII.,  Wheatstone,  1838,  385,  Fig.  24;  Helmholtz,  882;  Wundt,  ii.,  193; 

Sanford,  Lab.  Course,  291. 
XXIII.,  Martius-Matzdorff,  no.  13. 
XXIV.,  Wundt,  ii.,  193 ;  Sanford,  Lab.  Course,  292. 
XXV.,  Hering,  Hermann's  Hdbch.,  380;  cf.  Helmholtz,  917. 
XXVI.,  Wheatstone,  1838,  Fig.  25;   Wundt,  Human  &  Animal  Psych., 

198. 
XXVII.,  Hering,  Hermann's  Hdbch.,  383  ;  Helmholtz,  918. 
XXVIII.,  Hering,  Hermann's  Hdbch.,  382. 
XXIX.,  Wundt,  ii.,  211  ;  Human  &  Animal  Psych.,  198;  Helmholtz,  919. 
XXX.,  Hering,  Hermann's  Hdbch.,  383  ;  Helmholtz,  919. 
XXXI.,  Halves  of  Martius-Matzdorif,  nos.  28,  30. 
XXXII.,  Martius-Matzdorff,  no.  II.  of  set  of  lustre  slides ;  Helmholtz,  933 ; 

Sanford,  173. 
XXXIII.,  Wundt,  ii.,  209. 
XXXIV.,  Wundt,  ii.,  210. 
XXXV.,  Wundt,  ii.,  210. 
XXXVI.,  Wundt,  ii.,  210. 
XXXVII.,  in  the  Cornell  series,  is  a  photograph  entitled  "Where  the  water- 
lilies  bloom  in  March ;  Florida "  (child  in  boat,  among  water- 
lilies),  and  published   by  The   Littleton  View  Co.     It  shows 
patches  of  lustre,  as  well  as  true  reflections. 

Slide  i.    The  four  dots  combine,  and  we  see  two,  of  which  the 
right  is  nearer  to,  the  left  farther  from,  the  observing  eyes. 

•    •  »•  •  • 

Slide  i. 


Experiment  (3).  —  Slide  ii.  The  lines  combine,  with  the 
same  effect  as  is  given  by  the  dots.  Slide  iii.  The  curves  com- 
bine, the  concavity  being  towards  the  observer. 


§  47-    Stereoscopic  Slides 


27S 


Inversion  of  i.  and  ii.  gives  dots  and  lines  of  which  the  right- 
hand  member  is  farther  off.     Inversion  of  iii.  (and  here  the  un- 


SUDB  It.  — Fnlltitt. 


SUOB  III.  —  Full  UM. 


wary  student  is  apt  to  predict  falsely)  gives  concavity,  again, 
only  that  the  left-hand  direction  of  the  curved  line  is  reversed. 


SuDB  IV.  —  Fan  tize. 


SUDB  V.  —  Half  size. 


A  neat  variation  of  Slide  iii.  is  a  slide  composed  of  the  two 
right-hand  (or  left-hand)  halves  of  the  truncated-cone  stereo- 


SUDB  VL  — Hilf  siM. 


SUDB  VII.  —  Half  sue. 


2/6  Visttal  Space  Perception 

grams.     If,  e.g.,  halves  of  the  figures  of  Slide  vii.  are  taken, 
their  combination  shows  two  curves,  of  which  the  smaller  is  the 


Slide  viri.  —  Half  size. 

nearer.  Ask  what  will  happen  when  the  slide  is  inverted,  and 
a  good  part  of  the  class  will  reply  at  once  that  the  cone  in  relief 
will  be  converted  into  a  hollow  cone. 


Ix 
Slide  ix.  —  Half  size 


Experiment  (4).  —  Some  students  will  probably  draw  the 
double  images  as  they  look  when  both  eyes  are  open,  instead  of 
drawing  the  single  image  of  each  eye  separately.     The  result  is 


Slide  x.  —  Half  size. 


a  reversal  of  direction.  Note  that  Wheatstone  and  Hering 
draw  the  diagram  correctly  (Wheatstone  for  the  reflecting  stere- 
oscope, Hering  for  crossing  of  the  lines  of  regard  before  the 


§  47-    Stereoscopic  Slides 


277 


plane  of  the  page)^  while  Wundt  has  interchanged  the  explana- 
tions of  his  two  Figs.,  28  and  29  (H.  and  A.  Psych.,  187). 


SuDB  XI.  —  Half  size. 


Experiment  {5).  — The  model-effect,  referred  to  on  p.  272,  is 
very  striking  in  lunar  photographs.     Notice  that,  for  a  careful 


^ 


SuDE  ML  —  Half  sire. 


xili 


Slide  xiii.  —  Half  site. 


obserx^er,  the  combination  of  the  geometrical  figures  is  rarely 
complete.     If  the  base  of  the  object  is  fixated,  the  vertex  falls 


Slide  xtv.  —  Half  size. 


into  double  images  ;  and,  conversely,  if  the  vertex  is  fixated,  the 
base  is  seen  double.  If  a  point  is  taken  midway  between  base 
and  vertex,  the  binocular  image  at  first  appears  single,  but  con- 


2/8 


Vistial  Space  Perception 


tinued  steady  fixation  may  bring  out  double  images  both  before 
and  behind  the  point  of  regard. 

Experiment  (6). —  Slide  xviii.  gives  the  right  and  left  views 
of  two  lines,  situated  in  a  vertical  plane  passing  through  the 


SuDE  XVIII.  —  Full  size. 


Slide  xix.  —  Full  size. 


direction  of  regard  of  the  right  eye.  The  combined  image  veri- 
fies this  analysis.  Vary  the  slide,  by  increasing  the  distance 
between  the  left-hand  parallels.  Draw  the  figures,  with  in- 
creased distance  between  the  parallels,  upon  a  transparent  slide. 
See  Hering,  Beitrage,  84. 

Slide  xix.  gives  the  right  and  left  views  of  a  flat  ruler,  stand- 
ing in  the  vertical  plane  which  contains  the  line  of  regard  of  the 
right  eye. 

Slide  XX.  gives  the  two  projections  of  an  obtuse  angle,  whose 
limbs  diverge  from  the  observer  over  against  the  left  eye.  Vary 
the  slide,  by  left-right  conversion  of  the  right-hand  figure,  and 
the  obtuse  angle  opens  towards  you,  over  against  the  same  eye. 


\ 


\ 


Slide  xx.  —  Full  size. 


Fig.  73. 


Fig.  73,  which  is  known  as  <  Wheatstone's  Figure,'  has  played  a  large  part 
in  the  discussions  of  stereoscopic  vision  (Wheatstone,  1838,  384  f.).  Its  final 
and  complete  analysis  has   been  given  by  Hering  (Beitrage,  87-96).     The 


J  47.    Stereoscopic  Slides  279 

woikinf-throqgh  of  Hering*s  demonstration  with  free  stereoscopy  (convergent 
squinting)  is  good  practice,  and  the  experiment  is  theoretically  important. 
WundtHi  account  (ii..  195 ;  Beitrtige  zur  Theorie  d.  Sinneswahmchmung,  iv., 
1860,  386;  Human  and  Animal  Psych.,  191)  is  incorrect,  or  at  least  inade- 
quate. In  this  additional  experiment,  Hering's  caution  as  to  the  horizontal 
lines  of  separation  must  be  borne  in  mind  (Beitriige,  89).  The  parallel  lines 
di  the  i^guict  must  remain  sensibly  parallel  until  the  moment  of  fusion. 


ui 


SUDB  XXI.  —  Full  me. 

Experiment  (7).  —  The  combined  image  of  Slide  xxi.  shows 
simply  two  horizontal  lines  in  the  plane  of  the  slide-card.  Com- 
bination is  more  difficult  than  in  the  case  of  Slide  ii. ;  and  a 
steady  fixation  of  the  lines,  drawn  as  above,  may  bring  out 
the  double  images.  The  discrepancy  may  be  very  much  larger 
in  the  case  of  the  vertical  lines,  though  there  are  great  individ- 
ual differences  in  this  regard  (Wundt,  ii.,  104). 

The  two  circles  of  Slide  xxii.  combine ;  but  careful  observa- 
tion shows  that,  while  the  combination  is  perfect  at  the  sides 


SUDB  XXII.  —  Fall  uze. 


(vertically),  it  is  constantly  lapsing  above  and  below  (horizon- 
tally).    Cf.  Helmholtz,  882  f. 

Slides  xxi.  and  xxii.  might  represent  a  single  object  situated 
close  up  to  the  eyes  on  the  extreme  left  of  the  observer ;  the 
image  on  the  right  retina  would,  in  such  a  case  of  asymmetri- 
cal convergence,  be  smaller  than  that  on  the  left.  Wheatstone, 
1838,  386. 

Slides  xxiii.  and  xxiv.  cannot  represent  a  single  object.  In 
Slide  xxiii.,  the  diameters  of  the  small  circles  should  differ  by 
.5  mm.,  the  sides  of  the  squares  by  i  mm.,  and  the  diameters  of 
the  large  circles  by  2  mm.     In  Slide  xxiv.,  the  second  and  outer 


28o 


Visual  Space  Perception 


•circles  are  alike,  the  central  and  third  circles  different.  Notice 
the  readiness  of  combination,  as  one  first  looks  at  the  pictures 
in  the  instrument,  and  the  consequent  lapse  into  double  images 
above  and  below  under  steady  fixation. 


xxiii 


Slide  xxiii.  —  Half  size. 


The  general  lesson  is  that  "we  combine  in  a  single  idea 
retinal  images  that  cannot  possibly  proceed  in  reality  from  a 
single  object,  provided  only  that  they  approximate  very  closely 
to  the  real  images  of  an  object"  (Wundt).  The  greater  our 
practice  in  the  observation  of  double  images,  the  more  difficult 
is  it  for  us  to  secure  a  true  binocular  fusion.     This  is  true,  not 


Slide  xxiv.  —  Half  size. 


only  of  diagrams  like  those  of  Slides  xxiii.  and  xxiv.,  but  of 
stereograms  in  general  (see  Hering,  Beitrage,  109,  337 ;  Her- 
mann's Hdbch.,  432). 

Experiment  (8).  — We  might  expect  that  the  A  of  Slide 
XXV.  would  be  washed  over  by  the  white  background  of  the  right 
monocular  field,  so  that  it  would  appear  greyish  and  indistinct. 
In  actual  fact,  the  letter  is  seen  as  clearly  as  if  it  combined  with 
another  A  on  the  other  half  of  the  slide. 

In  Slide  xxvi.  we  have  no  combination  in  a  single  idea.  We 
may  see  either  letter  alone,  or  fragments  of  the  two  letters 
simultaneously.     In  neither  case  is  there  any  permanence  of  the 


§  47-    Sttrtoscopic  Slides 


281 


binocular  impression  ;  on  the  contrary,  there  is  a  constant  build- 
ing-up and  breaking-down  of  images.  The  variation  called  for 
m  the  text  consists  in  the  attempt  to  unite  two  letters  whose 
forms  are  partially  identical,  such  as  E  and  /%  L  and  7%  C  and  G, 


A 

■i« 

Slide  xxv.  — Half  site. 


SUDI  XXVI  —  Half  tixe. 


O  and  Q,  P  and  B.     The  resultant  letter  is  not  quite  so  steady 
as  the  A  of  Slide  xxv. 

In  Slide  xxvii.  we  may  see  the  vertical  band  continuous,  with  a 
lustrous  greyish  fringe  to  right  and  left  of  the  crossing-point ; 
or  the  horizontal  band  continuous,  with  the  fringe  above  and 
below ;  or  a  black  central  square,  with  grey  fringes  above,  below 


SUDK  XXVII.  — Full  tire. 


and  to  right  and  left.  We  never  see  a  continuous  cross,  such 
as  we  should  get  if  the  two  bands  imaged  themselves  upon  the 
same  retina. 

In  Slide  xxviii.  we  see  a  square,  whose  left  upper  quadrant  is 
black,  the  right  lower  quadrant  white,  while  the  other  two  quad- 
rants are  (over  most  of  their  surface)  a  lustrous  grey.  Note  the 
permanent  contrast  bands,  and  the  rivalry  of  the  vertical  and 
horizontal  contours. 

In  Slide  xxix.  we  see  a  total  image,  in  which  the  lines  in  the 
one  direction  are  interrupted  by  those  in  the  other.  The  inter- 
ruption oscillates,  from  the  vertical  to  the  horizontal  lines  or 


282  Visual  Space  Perception 

vice  versa.     There  may  be,  indeed,  not  only  an  interruption,  but 
an  actual  suppression,  so  that  the  portions  of  the  one  pair  of 


Slide  xxviii.  —  Full  size. 


lines  that  should  appear  between  the  other  pair  are  entirely 
obliterated ;  or  there  may  be  unilateral  suppression,  one  line  of 


XXIX 

Slide  xxix.  —  Full  size. 


a  pair  showing  a  gap  in  its  middle,  while  the  other  continues  its 
full  course  uninterrupted  save  by  the  crossing  contours  of  the 


Slide  xxx.  —  Full  size. 


Other  pair.  We  have,  then,  in  this  slide,  a  suggestion  of  depth, 
since  the  one  pair  of  lines  may  seem  to  lie  behind  the  other  pair  ; 
and  we  have,  further,  the  rivalry  of  contours.     Slide  xxx.  shows 


{  47-    SUreoscopk  Slides  283 

a  similar  phenomenon.  Slide  xxxi.  is  extremely  baffling.  One 
has  a  very  distinct  suggestion  of  tridimensionality,  and  the  eyes 
soon  grow  fatigued  in  the  attempt  to  *  set  themselves  *  for  a  true 

•  •■ hr  combination.     The  combined  figure  becomes  flatter 

icr  under  steady  fixation.     The  rivalry'  of  contours  may 
be  noticed  at  the  points  of  crossing  of  the  boundary  lines. 


SUDB  XXXI.  —  Half  size. 

The  phenomena  to  which  this  set  of  slides  introduces  us  are 
those  of  the  prevalence  of  contours,  the  rivalry  of  contours  and 
(i)  Slide  XXV.  gives  a  pure  instance  of  the  prevalence  of 
contours.  The  white  of  the  right-hand  field  is  *  suppressed  '  by 
the  A  of  the  left-hand  field.  This  fact  may  be  generalised  as 
follows:  "Any  contour  in  the  one  retinal  image  assists  the 
adjacent  portions  of  the  field  to  a  permanent  victory  over  the 
differently  tinted  ground  of  the  other  retinal  image"  (Hering). 
(2)  Slides  xxvi.-xxxi.  show  the  rivalry  of  contours.  "  If  contours 
in  the  two  retinal  images  take  such  directions  that  there  is 
retinal  congruence  for  only  a  single  point  of  each,  they  appear 
to  cross  one  another  at  the  point  of  the  visual  field  which  cor- 
responds to  this  pair  of  congruent  points,  but  always  in  such  a 
manner  that  the  one  contour  (together  with  the  strip  of  ground 
adjacent  to  it)  interrupts  the  other  or  is  interrupted  by  it" 
(Hering).  Hering  finds  the  significance  of  the  prevalence  and 
rivalry  of  contours  in  the  fact  that  "  they  prevent  the  fusion  of 
the  two  retinal  images,  and  secure  to  each  a  certain  amount  of 
independence."  Without  them,  the  images  of  the  two  unmoved 
eyes  would  necessarily  run  together,  as  objects  directly  seen 
through  an  unmoved  glass  and  objects  mirrored  in  it  run  to- 
gether.    They  are,  indeed,  a  sine  qua  non  of  the  binocular  per- 


284  Visual  space  Perception 

ception  of  depth.  Nevertheless,  Hering  does  not  attempt  any 
detailed  explanation  of  the  facts.  He  recommends  the  "  treffliche 
Schrift "  of  P.  L.  Panum  (Physiologische  Untersuchungen  iiber 
das  Sehen  mit  zwei  Augen,  Kiel,  1858);  and,  as  Panum's  expla- 
nation is  physiological  (p.  47),  and  Hering  himself  inclines 
always  to  physiological  as  distinct  from  psychological  interpreta- 
tions, we  may  take  it  for  granted  that  the  explanation  would  be 
couched  in  strictly  physiological  terms  (Beitrage,  308  ff.,  312  ff. ; 
Hermann's  Hdbch.,  384  f. ;  cf.  Helmholtz,  Phys.  Optik,  922  ; 
Sanford,  Lab.  Course,  171).  Helmholtz,  on  the  other  hand, 
argues  from  the  phenomena  of  rivalry  that  "the  contents  of  each 
visual  field  comes  to  consciousness  separately,  without  being 
fused  with  that  of  the  other  by  means  of  some  physiological 
mechanism,"  and  that  "the  fusion  of  the  two  fields  in  a  common 
image,  if  it  occurs,  is  consequently  a  psychical  act."  His  own 
explanation  is  couched  in  terms  of  attention  (922  ff.).  Fechner 
gives  a  full  discussion  of  the  attention  theory  in  his  paper  Ueber 
einige  Verhaltnisse  des  binocularen  Sehens  (Abh.  d.  kgl.  sachs. 
Ges.  d.  Wiss.,  vii.,  i860,  392  ff.).  His  conclusion  is  that  the 
attention  may  occasion  a  change  of  the  image  seen,  but  can 
never  determine  the  direction  of  the  change  (402).  Wundt 
deduces  from  the  phenomena  of  binocular  mixture,  suppression, 
rivalry  and  lustre  the  general  law  that  "the  impressions  of  the 
two  eyes  always  fuse  to  a  single  idea"  (ii.,  214).  Where  refer- 
ence to  a  single  object  is  impossible,  we  have  mirroring  and 
lustre,  or  rivalry  ;  but  there  is  always  a  fusion,  a  single  resultant. 
Rivalry  itself  is  determined  by  eye  movements  :  "  that  image  is 
always  preferred,  whose  contours  run  in  the  same  direction  as 
the  (accidental  or  purposed)  movement  of  regard"  (213;  cf. 
Beitrage  zur  Theorie  d.  Sinneswahrnehmung,  362 ;  Human  and 
Animal  Psych.,  209). 

(3)  Slides  xxvii.  and  xxviii.  show  the  phenomenon  of  lustre, 
to  the  consideration  of  which  we  now  pass. 

Experiment  (9).  —  If  a  black  and  a  white  fall  upon  the  same 
portion  of  a  single  retina,  we  see  an  intermediate  grey.  If  a 
black  and  a  white  fall  upon  corresponding  portions  of  the  two 
retinas,  we  see,  not  a  grey  {cf.  Slides  xxvii.,  xxviii.),  but  a 
graphite-like  lustre  or  sheen.     To  understand  this  effect,  we 


§  47-    Wnndt^s  Mirror  Expetimtnt 


285 


must  understand  the  psychology  of  reflexion,  of  the  percep- 
tion of  mirror  images 

Wundts  Exptrim€Ht,  —  Lay  a  square  of  red  paper,  a.  Fig.  74, 
upon  a  grey  background.  Above  it,  at  an  angle  of  45**,  set  up 
the  sheet  of  glass  g.  Lay  a  square  of  white  paper,  b,  upon  a 
similar  g^y  background,  in  the  position  indicated  in  the  flgure. 
The  eye,  looking  through  g  at  <?,  sees  the  white  image  of  b 
(marked  ^  in  the  figure)  mirrored  behind  the  red  of  a.  Neither 
the  red  nor  the  white  has  suffered  any  loss  of  individuality ; 
neither,  ir,  has  taken  on  any  tinge  of  pink. 

If  the  grey  ground  of  b  is  moved  to  the  position  r,  there  is  no 
reflexion,  but  simply  mixture;  we  see  a  single  pink  squaiv      It 


Fig.  74- 


FiG.  75. 


the  grounds  are  left  as  before,  but  are  themselves  coloured  red 
and  white,  we  again  get  no  reflexion,  but  a  single  pink  surface. 
If,  finally,  we  draw  small  outline  squares  in  black  upon  these 
red  and  white  grounds,  the  phenomenon  of  reflexion  reappears ; 
each  square  is  assigned  to  its  appropriate  distance. 

Now  give  the  eyes  and  the  apparatus  the  positions  indicated 
ri  Fig.  75.  The  left  eye  sees  a  alone;  the  right  eye  sees  the 
image  y  mirrored  behind  a.  If  b  is  very  bright,  and  if  b^  covers 
the  whole  of  <?,  the  latter  may  be  completely  ignored :  the  left 
eye  then  sees  «,  and  the  right  eye  sees  only  b\  Under  these 
conditions  we  have,  as  we  had  at  first,  the  single  idea  of  a  re- 
flecting object,  and  a  clear  discrimination  of  the  reflecting  surface 
from  the  image  mirrored  behind  it. — Wundt  uses  this  latter 


286  Visual  Space  Perception 

result  to  explain  the  suppression  of  the  middle  portion  of  the 
lines  of  Slide  xxix.  "Where  the  position  of  the  object  [the 
reflecting  surface]  corresponds  to  that  of  the  reflected  image, 
the  object  [the  reflecting  surface]  is  ignored ;  just  as  those  por- 
tions of  one  of  the  stereoscopic  pictures  which  were  covered  by 
lines  of  the  other  picture  were  ignored."  The  uninterrupted 
lines  are  seen  through  the  interrupted  lines  (Human  and  Animal 
Psych.,  202;  Phys.  Psych.,  ii.,  214).  Does  this  interpretation 
agree  with  O's  introspection  > 

The  conditions  under  which  this  perception  of  transparency, 
of  the  seeing  of  an  object  behind  another  object,  arises  are  stated 
by  Wundt  as  follows.  "We  say  that  a  surface  reflects,  or  is 
transparent,  when  it  gives  perfectly  clear  mirror-images,  while 
there  is  still  some  sort  of  indication  to  remind  us  of  its  own 
presence.  A  few  patches  of  brighter  illumination,  which  are 
therefore  lustrous,  would  serve  this  end."  Note  that  the  reflector 
and  the  reflected  image  are  never  seen  in  strict  simultaneity, 
since  the  field  of  vision  for  Wundt  is  always  a  surface.  If  the 
mirroring  is  perfect,  we  lose  the  reflector,  except  that  its  con- 
tours may  serve  to  *  frame '  the  reflected  object ;  if  it  is  imperfect, 
we  get  the  single-surface  perception  of  lustre.  For  "we  say 
that  a  surface  is  lustrous,  when  the  mirror-image  that  it  gives  is 
very  indistinct ;  when  a  clear  apprehension  of  the  mirror-image 
is  prevented  by  irregularities  of  the  reflecting  surface ;  or  (and 
this  is  the  commonest  case)  when  both  these  factors  are  cooper- 
ating to  produce  the  result"  (Phys.  Psych.,  ii.,  205;  cf.  the 
original  discussion  in  the  Beitrage  zur  Theorie  der  Sinnes- 
wahrnehmung,  300  ff.,  and  Aubert,  Physiol,  d.  Netzhaut,  1865, 
302  ff.).  Mirroring  and  lustre  are,  then,  our  perceptual  *way 
out  *  of  the  difficulty  of  making  two  heterogeneous  groups  of 
sensations  into  a  single  idea.  Wundt's  analysis  is  structural ; 
his  explanation  is  purely  functional. 

Helmholtz'  account  is  very  similar.  If  light  falls  upon  a 
dead-finished  surface,  he  says,  it  is  reflected  in  all  directions  in 
such  a  way  that  the  surface  appears  uniformly  bright  from  what- 
ever point  it  is  viewed.  Lustrous  surfaces  are  those  that  give 
more  or  less  regular  mirror-reflexions.  Suppose  that  the  surface 
is  smooth,  in  all  its  parts,  but  is  not  quite  even :  then,  as  we 


§  47*    Stereoscopic  Lustre 


287 


look  at  it,  one  of  our  eyes  may  be  in  the  direction  of  the  reflected 
light,  and  the  other  not.  The  surface  will  thus  seem  to  be  of  a 
different  brightness  to  the  two  eyes.  If,  therefore,  we  synth6- 
tisc  the  conditions,  and  offer  black  to  the  one  eye  in  the  stereo- 
scope, and  white  to  the  other ;  or  if  we  offer  one  colour  to  the 
one  eye,  and  another  colour  to  the  other,  — choosing  such  colours 
as  a  really  lustrous  surface  might  present ;  we  necessarily  obtain 
the  effect  of  lustre  from  our  combined  image  (933  f.;  cf,  San- 
ford,  Lab.  Course,  173). 

Hering,  who  also  refers  lustre  to  irregular  or  imperfect  reflex- 
ion, writes  that  the  condition  of  its  appearance  is  "a  cleavage 
of  sensation  ;  a  portion  of  the  sensation  seems  to  be  the  essential 
colour  of  the  surface,  while  other  portions  are  regarded  as  acci- 
dental light  or  shade,  lying  on  or  before  the  surface,  or  proceeding 
from  the  interior  of  the  lustrous  body."  He  notes  that  rivalry 
of  the  monocular  fields  is  favourable  to  lustre,  since  the  required 
cleavage  of  the  total  sensation  is  directly  given.  Movement, 
whether  of  the  lustrous  object  or  of  our  own  bodies  {cg.^  change 
of  ocular  convergence^  is  also  a  favourable  condition  (Hermann's 
Hdbch.,  576  f.> 

We  may  now  consider  the  slides  of  this  group.  —  Slide  xxxii. 
shows  a  graphite  lustre.     This  was  discovered  by  H.  W.  Dove 


SuDE  xxxii.  —  Half  size. 


(see  Darstellung  der  Farbenlehre  und  Optische  Studien,  Berlin, 
1853,  171  [the  original  paper  was  published  in  185 1] ;  Optische 
Studien,  Fortsetzung,  1859,  i  ff.). 

Slide  xxxiii.  shows  no  lustre.  The  white  disc  appears,  with- 
out darkening  or  sheen,  in  the  middle  of  the  binocular  image. 
The  slide  is,  therefore,  analogous  to  Slide  xxv.  rather  than  to 


288 


Visual  Space  Perception 


Slide  xxxii.  If  lustre  or  mirroring  is  to  arise,  two  conditions 
must  be  fulfilled:  (i)the  impressions  must  be  so  far  different 
that  they  can  be  referred  to  two  different  objects,  a  reflecting 


xxxil! 
Slide  xxxiii.  —  Full  size 


and  a  reflected ;  and  (2)  they  must  force  themselves  upon 
perception  with  approximately  equal  intensities.  This  latter 
condition  is  not  satisfied  by  Slide  xxxiii. 


xxxiv 

1 

SUDE  XXXIV.  —  Half  size. 


XXXV  ^^^^~ 

Slide  xxxv. — Half  size. 


Slide  xxxiv.  shows  lustre.  The  slide  is  best  made  by  pasting 
strips  of  black  and  white  paper  upon  a  grey  ground.  Slide  xxxv. 
gives  the  same  effect  as  Slide  xxxiii.,  and  for  similar  reasons. 


xxxvl 
Slide  xxxvi.  —  Full  size. 


In  Slide  xxxvi.  the  smaller  disc,  together  with  its  immediate 
surroundings  of  white,  seems  to  lie  behind  the  large  disc.  Lus- 
tre is  seen,  but  not  so  plainly  as  in  Slide  xxxiv. 


5  a 7.    PiMtk'k/ttr  Co/our  AfLr/ufit  289 

Slide  xxxvii.  may  be  replaced  by  any  photographic  slide 
showing  polished  tables,  columns,  etc. ;  rippling  water,  with  sun- 
light upon  it ;  satin  dresses  or  hangings  ;  plants  with  lustrous 
leaves,  etc.  (Hclmholtz,  933).  Some  wet  stones  in  A  Mirror 
View  of  the  Forum,  published  by  J.  F.  Jarvis,  give  a  very 
striking  lustre.  Notice  that  the  beginner  may  mistake  the  pho- 
tographic glaze  for  the  lustre  of  the  pictured  objects. 

Experiment  (io)l  — The  essential  point  in  this  experiment  is 
the  production  of  a  binocular  colour  mixture.  The  possibility 
of  binocular  mixtures  has  been  keenly  disputed.  "  Hermann 
Meyer,  Volkmann,  Meissner,  Funke  and  I  myself,"  says  Helm- 
holtz,  "have  never  seen  the  mixed  colour;  Dove,  Regnault, 
Briicke,  Ludwig,  Bering  and  Panum  declare  that  they  are  able 
to  see  it  "  (Phys.  Optik,  926).  Wheatstone  (1838,  386  f.)  might 
have  been  added  to  the  list  of  negatives.  Helmholtz  ascribes 
the  illusion  of  binocular  mixture  to  various  conditions :  lack  of 
check  or  control  of  the  experiment  by  simultaneous  vision  of  the 
true  (monocular)  mixed  colour,  and  consequent  failure  to  per- 
ceive the  rivalry  which  is  really  present ;  after-images ;  colour 
induction ;  contrast.  He  admits,  however,  that  there  may  be 
great  individual  differences  as  between  different  observers. 
Hering  asserts  that  the  discrepancy  of  result  is  due,  quite  apart 
from  individual  differences,  to  diversity  of  the  conditions  of 
observation,  and  to  divergent  interpretations  of  the  term  '  binoc- 
ular mixture*  and  correspondingly  divergent  expectations  as  to  the 
character  of  the  combined  image  (Hermann's  Hdbch.,  592).  The 
one  thing  needful  for  binocular  mixture-effects  is  the  elimination 
of  contours,  points  and,  indeed,  any  sort  of  irregularity,  from  the 
coloured  surfaces.  Helmholtz  neglected  this  precaution,  and 
was  further  led  astray  by  his  presupposition  that  the  result  of 
binocular  would  be  identical  with  the  result  of  monocular  colour 
mixture  (595,  599).  This  is  not  the  case.  The  facts  arc 
summed  up  by  Hering  in  his  general  law  of  the  "  complementary 
share  of  the  two  retinas  in  the  visual  field"  (Beitrage,  308  ff . ; 
Hermann's  Hdbch.,  596  ff.).  There  is  no  addition  of  the  monoc- 
ular sensations  :  the  resultant  sensation  is  always  si.  Hence, 
if  the  one  retina  furnish  |  of  this  resultant,  the  other  must  fur- 
nish \ ;  if  the  one  furnish  J,  the  other  must  also  furnish  J  ;  if 


290  Visual  Space  Perception 

the  one  furnish  i,  the  other  must  furnish  o.  — The  working-out 
of  this  law  in  binocular  and  monocular  mixtures,  and  in  certain 
of  Fechner's  binocular  experiments,  is  very  instructive ;  if  time 
allow,  it  may  be  given  to  the  student  as  an  extra  experiment. 

Slide  xxxviii.  and  its  Variants,  —  The  author  has  no  doubt 
but  that  binocular  mixture  occurs,  and  no  doubt  but  that  some 
of  these  slides  will  demonstrate  its  occurrence  to  every  student 
who  observes  the  conditions  of  the  experiment.  The  squares 
must  be  so  placed  as  to  be  entirely  and  exactly  coincident  in  the 
binocular  field,  and  it  is  well  to  throw  them  a  little  out  of  focus 
(/>.,  to  look  at  them  with  inadequate  accommodation),  in  order 
to  blur  the  contours.  Note  ( i )  that  neighbouring  colour-tones 
give  the  mixture,  as  a  rule,  more  easily  than  complementary 
colours.  It  is,  however,  possible  to  combine  complementaries  to 
a  binocular  grey.  (2)  The  less  the  saturation,  the  easier  as  a 
rule  is  the  binocular  mixture.  It  is,  however,  possible  to  com- 
bine saturated  colours.  (3)  The  less  the  brightness,  and  the 
more  nearly  equal  the  brightness  of  the  combined  colours,  the 
easier  is  the  mixture.  Bright  colours  can,  however,  be  com- 
bined. 

In  the  cases  where  mixture  is  impossible,  the  observed  phe- 
nomena will  be  those  of  retinal  rivalry.  Now  the  one,  and  now 
the  other  colour  will  be  seen ;  now  the  one  will  seem  to  hang, 
like  a  translucent  veil,  before  the  other ;  now  a  patch  of  the  one 
will  give  way  to  the  other,  which  spreads  gradually  over  the 
whole  square ;  now  the  two  will  give  a  brilliant  lustre.  The 
changes  should  be  carefully  noted  by  Oy  and  their  times  taken 
by  £•. 

Slide  xxxix. — The  two  extreme  squares  are  monocular  im- 
ages, and  are  unimportant  for  the  present  purpose.  The  three 
middle  squares  are  binocular  images :  the  two  outer  show  the 
pure  colour,  the  middlemost  shows  the  mixture  colour.  See 
Hering,  Hermann's  Hdbch.,  592.  The  student  should  draw  a 
diagram,  indicating  how  the  images  arise. 

Slide  xl  —  At  the  centre,  where  green  and  red  meet,  we  see 
simply  these  two  colours ;  toward  the  outside  they  are  inter- 
mixed with  a  bluish  colour.  The  slide  is,  therefore,  analogous 
to  Slide  xxxvi. 


§  47'    Bimvck/ar  Colour  Mixturt 


391 


SUdi  xH,  —  We  sec,  upon  the  red  background,  a  large  blue 
square,  in  the  middle  of  which  is  a  small  yellow  square  sur- 
rounded by  a  fringe  that  shows  a  deep  red  on  the  inside,  but 
becomes  more  and  more  tinged  with  blue  towards  the  outside. 
Wundt  (Human  and  Animal  Psych.,  208)  explains  the  result 
entirely  in  terms  of  reflexion.  Can  it  be  explained  in  terms  of 
dominance  of  contours  ? 


suggest 
stereo- 


These  colour-slides  may  be  varied  indefinitely,  as  further  questions 
themselves.  It  is  of  advantage,  in  some  instances,  to  put  aside  the 
scope  and  have  recourse  to  free  stereoscopy.  It 
is  still  better  to  use  Hering's  binocular  colour 
mixer,  although  a  successful  handling  of  the  in- 
strument requires  a  certain  amount  of  skill  and 
practice.  A  combination  of  such  work  with  a 
careful  repetition  of  the  ex|>eriments  cited  by 
Helmholtz  against  binocular  mixtures  in  general 
forms  an  excellent  additional  experiment.  In  any 
case,  the  interested  student  should  be  allowed 
critically  to  repeat  Helmholtz*  experiments. 

Question  (6). — The  terms  and  phrases 
are :  prevalence  of  contours,  suppression, 
rivalry  of  contours,  retinal  rivalry,  lustre, 
binocular  mixture,  reflexion  or  mirroring. 
These  have  been  sufficiently  explained  in 
the  foregoing  discussions.  The  attention 
of  the  student  may  be  called  (if  he  has  not 
discovered  the  fact  for  himself)  to  the  part 
played  by  monocular  contrast  in  some  of 
:he  slides  where  its  presence  has  not  been 
expressly  noted. 

(7)  Cover  the  one  half  of  a  slide  with 
black,  the  other  with  white  paper.     On 

the  flrst  half,  paste  a  small  square  of  white,  on  the  second  a  simi- 
lar and  congruently  placed  square  of  black.  Notice  that  there  is 
rivalry  between  backgrounds  and  squares  alike.  This  is  said  by 
Herin^  (Beitrage,  309)  to  prove  the  point. 

(8)  The  slide  should  be  made  on  the  analogy  of  Slide  viii. 
Draw,  side  by  side,  the  stereograms  of  two  precisely  equal  and 
similar  truncated  pyramids:  but  draw  the  one  for  a  solid  and 


Fig.  76. —  Hering't  binoca- 
lar  colour  mixer  (Rothe, 
Mk.  32).  L,  R,  the  two 
eyes;  ^,  dark  box;  ggf, 
coloured  glasses  (red  and 
blue) ;  //,  supporting 
plate  of  clear  glass;  sss, 
squares  of  white  paper. 
Hermann's  Hdbcb.  d. 
Physiol.,  ui.,  i,  1879,  593. 


393  Visual  Space  Perception 

the  other  for  a  hollow  effect.  Notice  that  the  square  that  comes 
out  towards  you  looks  distinctly  smaller  than  the  square  that 
bounds  the  far  end  of  the  hollow  pyramid. 

Related  Questions. — (9)  One-eyed  persons  have  no  diffi- 
culty in  finding  their  way  about ;  and  we,  ourselves,  if  we  close 
one  eye,  suffer  from  no  illusion  as  to  the  solidity  of  the  objects 
around  us.  It  must  be  remembered,  however,  that  in  such  cases 
(i)  the  observer  can  change  his  position  with  regard  to  sur- 
rounding objects ;  (2)  the  objects  themselves  may  change  their 
positions,  with  regard  to  him  and  to  one  another;  and  (3)  a 
number  of  secondary  criteria  of  distance  are  still  available. 
How  is  it  if  these  auxiliary  factors  are  ruled  out } 

There  is  a  *  parlour  game '  which  bears  upon  this  point.  A 
curtain  ring  is  suspended  in  the  median  plane  of  the  observer's 
body.  He  is  given  a  pencil,  and  required  to  thrust  the  pencil 
through  the  ring,  with  one  eye  closed.  The  pencil  passes  at 
'surprising*  distances  before  or  behind  the  ring.  Plainly,  then, 
binocular  vision  is  required  for  accurate  localisation.  —  See,  for 
a  better  form  of  the  experiment,  Helmholtz,  796 ;  Sanford,  exp. 
216.  Cf.  Hering,  Beitrage,  347;  Hermann's  Hdbch.,  391.  The 
*game*  may  be  raised  to  the  dignity  of  an  experiment  by  a 
careful  ruling-out  of  possible  secondary  factors  :  thus  the  ob- 
server may  look  through  a  blackened  tube,  so  that  he  does  not 
see  the  hand  that  holds  the  pencil ;  rings  and  threads  of  differ- 
ent diameters  may  be  used  interchangeably,  etc.  See  Hofler 
and  Witasek,  Psychologische  Schulversuche,  1900,  21. 

Our  particular  Question  may  be  answered,  roughly,  by  Brew- 
ster's statement  (Stereoscope,  3)  that  monocular  stereoscopy  is 
possible  only  with  pictures,  not  with  diagrams.  This  is  so  far 
true  as  that  the  secondary  criteria  of  the  depth-perception  are 
of  enormous  advantage  in  monocular  stereoscopy.  It  is,  how- 
ever, not  strictly  true.  There  are  diagrams,  as  Hering  says 
(Beitrage,  66,  78  f.),  which  ** incite  or  even  constrain  us  to  the 
perception  of  depth,"  in  the  absence  of  the  secondary  factors. 

Place  Slide  vi.  or  vii.  in  the  stereoscope.  Close  one  eye,  and 
look  at  the  half-stereogram  with  the  other.  In  all  probability, 
you  will  obtain  the  image  of  a  cameo  or  intaglio,  the  figure 


§  47-   MoHocuIttr  Siertoscofy  293 

oscillating  from  th«  one  form  to  the  other  (see  p.  310)  The 
relief  is  not  nearly  so  well  marked  as  it  is  when  both  eyes  are 
open :  test  this,  by  opening  the  closed  eye  at  a  moment  when 
the  relief  is  clearly  seen  in  monocular  vision.  Steady  fixation 
of  the  centre  of  the  figure  enables  one  to  keep  the  image  in  the 
plane  of  the  card  for  some  little  time  together. 

Vary  the  experiment,  by  looking  into  the  stereoscope,  first, 
with  both  eyes  open,  and  then  closing  one  eye.  In  most  cases, 
there  is  an  immediate  conversion  of  relief,  which  is  the  more 
pronounced  the  less  practised  the  observer.  In  a  few  seconds, 
the  figure  comes  to  the  plane  of  the  card,  and  the  oscillation  of 
cameo  and  intaglio  begins. 

Place  Slide  xv.,  xvi.,  or  xvii.  in  the  stereoscope.  Notice  that 
Slides  XV.  and  x\\\.  give  a  good  stereoscopic  effect  in  monocular 
vision  (allowance  must  be  made  for  the  difference  in  brightness 
between  this  and  binocular  vision  !),  whereas  Slide  xvi.  shows 
hardly  any  relief  at  all.  See  Aubert,  Physiol,  d.  Netzhaut,  323 
ff. ;  Helmholtz,  767  ff.  ;  Wundt,  ii.,  204 ;  VVheatstone,  1838,  380. 

(10)  Brewster,  speaking  of  diorama,  says  :  "The  light,  con- 
cealed from  the  observer,  is  introduced  in  an  oblique  direction ; 
and  the  distance  of  the  picture  is  such  that  the  convergency  of 
the  optic  axes  loses  much  of  its  distance-giving  power.  The 
illusion  is  very  perfect,  especially  when  aided  by  correct  geomet- 
rical and  aerial  perspective."  *'  If  light  come  from  various  di- 
rections, or  the  canvas  move  to  the  least  degree,  the  illusion  is 
gone"  (Stereoscope,  2  f.).  In  the  more  modern  cyclorama,  one 
has  constancy  of  illumination  ;  distance ;  correct  perspective 
(the  technique  of  such  painting  has  improved  very  greatly  since 
Brewster  wrote) ;  a  *  real '  foreground,  blended  skilfully  with  the 
scenes  of  the  painted  wall ;  and  illusory  surroundings  (one  is 
on  the  roof  of  a  house,  or  on  a  hillock,  in  the  midst  of  the  scene 
portrayed^  See  Aubert,  Physiol,  d.  Netzhaut,  324 ;  Phys.  Optik, 
619  f.  (Aubert  notes  that  vision  of  the  painted  surface  through 
a  large  convex  glass  renders  our  estimate  of  its  distance  uncer- 
tain, and  so  enhances  the  illusion);  Hofier,  Psychologic,  294; 
Helmholtz,  776. 

(11)  The  secondary  criteria  may  be  summed  up  as  follows. 
(a)  Linear  perspective ;  the  course  of  the  contour-lines  of  ob- 


294  Visual  Space  Perception 

jects  in  the  field  of  vision,  (b)  Aerial  perspective.  This  may 
be  generalised  as  relative  clearness  of  outline  and  colour-tone. 
{c)  Distribution  of  light  and  shade,  {d)  Interposition  ;  the  par- 
tial covering  of  far  by  nearer  objects,  {e)  Especially  in  the 
case  of  familiar  objects,  apparent  magnitude  (visual  angle).  (/) 
Movement  of  objects  in  the  field  of  vision,  {g)  Movement  of 
our  own  head  or  body.  If  we  fixate  a  near  object,  and  move 
the  head  to  one  side,  distant  objects  show  a  movement  in  the 
same  direction  ;  if  we  fixate  a  far  object,  and  move  the  head  as 
before,  nearer  objects  show  a  movement  in  the  opposite  direc- 
tion.—  Hering,  Hermann's  Hdbch.,  578  ff.  ;  Wundt,  ii.,  199  ff. ; 
Helmholtz  and  Aubert,  as  quoted  ;  Brewster,  Stereoscope,  44  f. ; 
Titchener,  Outline,  204  f.  ;  Sanford,  Lab.  Course,  exps.  176, 
183,  184,  188. 

(12)  Brewster  assigns  a  triple  superiority  to  monocular  vision. 
{a)  Reflected  light  is  shut  off,  so  that  there  is  less  suggestion 
of  a  plane  surface;  (^)  there  is  no  'convergency  of  the  optic 
axes '  to  indicate  a  plane  surface  [the  student  should  perform 
Bonders'  experiment ;  Aubert,  Phys.  Optik,  620] ;  (c)  possible 
differences  between  the  two  eyes  are  eliminated.  —  Stereoscope, 
45  f.  Cf.  Aubert,  Phys.  d.  Netzhaut,  324;  Wheatstone,  1838, 
380  f.  ;  Wundt,  ii.,  203. 

Literature : 

Sir  D.  Brewster:  The  Stereoscope,  its  History,  Theory  and  Construction. 
London,  1856. 

J.  Le  Conte :  Sight,  an  Exposition  of  the  Principles  of  Monocular  and 
Binocular  Vision.     International  Scientific  Series,  1881. 

W.  N.  Suter :  Handbook  of  Optics  for  Students  of  Ophthalmology.  New 
York,  1899. 

R.  T.  Glazebrook :  Light,  an  Elementary  Text-book,  theoretical  and  prac- 
tical.    2d  edn.     Cambridge,  1895. 

C.  G.  Th.  Ruete:  Das  Stereoskop,  eine  populare  Darstellung  mit  zahlreichen 
erlauternden  Holzschnitten  und  mit  27  stereoskopischen  Bildern.  2d  edn. 
Leipzig,  1867. 

H.  W.  Dove  :  Darstellung  der  Farbenlehre  und  Optisehe  Studien.  Berlin, 
1853. 

H.  W.  Dove:  Optisehe  Studien,  Fortsetzung  der  in  der  *  Darstellung  der 
Farbenlehre '  enthaltenen.     Berlin,  1859. 

C.  Wheatstone  :  Contributions  to  the  Physiology  of  Vision,  i.  On  some 
remarkable,  and  hitherto  unobserved,  Phenomena  of  Binocular  Vision,  Phil. 
Trans,  of  the  Royal  Society  of  London,  1838,  Pt.  ii.,  371  ff. 


{  48.    Tki  Pseudoscapt 


29S 


C.  Wbtttstone:  Samc«  ii.  Phil.  Trans,  of  the  Royal  Society  of  London, 
185a,  Pt.  i.,  I  fr. 

H.  von  Helmholu :  Handbuch  der  physiologischen  Optik.  ad  edn.  Ham- 
barf  and  Leipttg,  1896. 

£.  Hering:  Der  Raumsinn  und  die  Bewegungen  des  Aoges.  In  Her- 
mann's Handbuch  der  Phytiologie,  iii.,  1,  343  AT.    Leipxig,  1879. 


ixpiRiMEirT  xxym 

{  48.  The  Piendoeoope.  —  The  total-reflexion  pseudoscope  was 
figured  and  described  as  such  by  VVheatstone  in  1852  (Phil. 
Trans.»  10  ff.)^     Fig.  'jj  shows  its  original  form.     A  year  before, 
H.  W.  Dove  had  invented  the  same 
instrument    under   the   name    of   the 
'prism   stereoscope.*      Dove   was   de- 
sirous of    constructing  a  stereoscope 
which  should  be  free  both  from  the 
secondary     mirror-images     (reflexions 


Fia  77.  — Wheatstoiie*t  toul-reflexion 
paeudoMope. 


Fia  78.  —  Dove's  converting 
ttereoKope. 


from  the  mirror-surfaces)  of  the  Wheatstone  stereoscope,  and 
from  the  chromatic  defects  of  Brewster's  semi-lenses.  His 
choice  was  thus  narrowed  down  to  metallic  mirrors  and  total- 
reflexion  prisms,  and  he  selected  the  latter  (Farbenlehre  und 
Optische  Studien,  edn.  of  1853,  194  f.).  Fig.  78  shows  one  of 
Dove's  instruments. 

Questions.  — ( i )  Fig.  79  indicates  the  optical  principles  upon 
which  the  total-reflexion  pseudoscope  is  based.  O  is  the  object 
viewed ;  DD  the  pseudoscopic  double  images ;  re  the  rays  com- 
ing to  the  eyes.     As  the  prisms  are  turned,  and  the  lines  of 


296 


Visual  Space  Perception 


regard  correspondingly  converged,  the  double  images  overlap  to 
form  a  binocular  total  image,  while  the  object  of  course  disap- 
pears. Cf.  Figs.  58,  59,  60  above.  —  Ruete,  Das  Stereoskop,  84 ; 
Sanford,  Lab.  Course,  exp.  214. 

The  tubes,  in  the  instrument  recommended  in  the  text,  serve 
the  purpose  of  the  hood  of  the  stereoscope ;  the  turning  of  the 
tubes  about  the  vertical  axes  answers  the  same  purpose  as 
movement  of  the  slide  carrier  along  the  bar  of  the  stereoscope  ; 

and  the  to  and  fro  movement  of 
the  left-eye  tube  allows  the  instru- 
ment to  be  adjusted  for  different 
interocular  distances. 

"Each  eye,"  says  Wheatstone, 
"will  see  [in  the  pseudoscope]  a 
reflected  image  of  that  projection 
of  the  object  which  would  be  seen 
by  the  same  eye  without  the  pseu- 
doscope "  (12).  The  conversion  is, 
therefore,  that  of  the  second  line 
of  Fig.  25  of  the  text. 

Some  other  forms  of  pseudoscope 
may  be  mentioned  here.  ( i )  Mir- 
ror pseudoscopes.  (a)  Wheatstone 
describes  a  mirror  pseudoscope  of 
his  own  devising  as  follows.  "Two 
plane  mirrors  are  placed  together 
\  so  as  to  form  a  very  obtuse  angle 
towards  the  eye  of  the  observer ; 
immediately  before  them  the  object 
is  to  be  placed  at  such  distance  that  a  reflected  image  shall  appear 
in  each  mirror.  The  eyes  being  placed  before  and  a  little  above 
the  object,  must  be  caused  to  converge  to  a  point  between  the 
object  and  the  mirrors  ;  the  right-hand  image  of  the  left  eye  will 
then  unite  with  the  left-hand  image  of  the  right  eye,  and  the  con- 
verse relief  will  be  perceived.  The  disadvantages  of  this  method 
are  that  only  particular  objects  can  be  examined,  and  it  requires  a 
painful  adaptation  of  the  eye  to  distinct  vision  "  (16).  The  stages 
of  conversion  are :  a  —  b^  —  b\  see  answer  to  Question  (4),  below. 


Fig.  79. 


§  43.    Th4  Pstudosccpe 


297 


(b)  J.  R.  Ewald*s  pseudoscope  is  represented  diagrammatical ly 
in  Fig.  80.  The  rays  proceeding  from  the  object  fall  upon  the 
mirrors  J/J/,  and  are  twice  reflected  before  reaching  the  eyes. 
The  screen  5  confines  each  eye  to  its  own 
field  of  regard.  The  stages  of  conversion 
are :  a  —  ^  —  tf  —  «':  L  sees  the  right  eye's, 
md  R  the  left  eye's  picture  of  the  object. 
The  objects  viewed  with  this  instrument 
must  be  small,  and  their  range  of  distance 
is  exceedingly  limited. 

{c)  G.  M.  Stratton*s  pseudoscope  is 
shown  diagram  mat  ically  in  Fig.  81  (see 
Psychol.  Review,  v.,  1898,  632).  J/  and 
X  are  mirrors,  which  can  be  turned  about 
their  vertical  axes ;  J/  can  also  be  moved 
to  or  from  N  in  the  horizontal  line. 
L  views  the  object  directly ;  R  views  it 
after  a  double  reflexion.  The  mirrors 
must  be  of  good  quality,  or  the  loss  of 
light  in  R*s  image  will  affect  the  result. 
The  conversion  is  of  the  first  type,  though 
the  manner  in  which  it  is  induced  differ- 
entiates this  instrument  both  from  Ewald's  pseudoscope  and 
from  the  stereoscopes  with  interchanged  diagrams.  It  is  as  if 
the  right  eye,  with  its  normal  image,  were  placed  bodily  to 

the  left  of  the  left  eye: 
cf.  the  Helmholtz  telestereo- 
scope.  Wheatstone  makes 
a  limited  application  of  the 
principle,  as  follows.  **  Hav- 
ing taken  a  photograph  of 
the  object,  which  should  be 
one  the  converse  of  which 
has  a  meaning,  take  two 
others  at  the  same  angular  distance  (say  18°),  one  on  the  right 
side,  the  other  on  the  left  side  of  the  original.  Of  the  three 
pictures  thus  taken,  if  the  middle  one  be  presented  to  the  right 
eye,  and  the  left  picture  to  the  left  eye,  a  normal  relief  will  be 


6  (B 

Fio.  80.  —  Ewald's  mirror 
pseudotcope.  Majer, 
Mk.  25. 


\i-x 


Fig.  81.  —  Scratton's  mirror  pteudoftcope. 
A  working  model  can  be  made  for  $y. 


298  Visual  Space  Perception 

seen ;  but  if  the  right  picture  be  presented  to  the  left  eye,  the 
other  remaining  unchanged,  a  converse  relief  will  be  seen." 
Similar  results  are  found,  if  the  left  eye  sees  the  middle  picture, 
and  the  right  the  right  and  left  pictures  successively.  **  It 
must  be  observed,  that  the  normal  and  converse  reliefs,  when 
.  /  the    same    picture   remains 

J  M^^  presented  to  the  same  eye, 

^^^Z^""~" "^f^  belong  to  two  different  posi- 

^*"'^->>^^;--'-'^'^  /  ^S**  tions  of  the  object "  (11). 

^^^^^^^^      "'^""HL.^  n'  ^  ^^^  J'   J^s^^^^'s   adapta- 

■/--~^^!^^?^  ^^^"  ^^  ^^^  *  perspectoscope  * 

r  /  iV'     (Psychol.  Review,  vii.,  1900, 

/  I  ^       53)-     ^^^  and  NN  are  two 

/  I  mirrors,  whose  positions  can 

A^  Av       be  changed   to   M'M'  and 

(l)  \\)      N'N'.     R'  and  L'  are  the 

Pjg  g2^  centres    of    the    right    and 

left  pictures  of  an  ordinary 

Brewster  stereogram.     If  the  mirrors  are  at  MM  and  NN,  the 

instrument  is  a  pseudoscope :  R  sees  L'  and  L  sees  R'.     The 

stages  of  conversion  are,  again,  a  —  b'  —  b.     If  the  mirrors  are 

at  M'M'  and  N'N\  the  instrument  is  a  stereoscope ;   R  sees 

R'  and  L  sees  L'. 

(2)  Lenticular  Pseudoscopes. — {a)  Wheatstone's  pseudoscope. 
"  Place  between  the  object  and  each  eye  a  lens  of  small  focal 
distance,  and  adjust  the  distances  of  the  object  and  the  lenses 
so  that  distinct  inverted  images  of  the  object  shall  be  seen  by 
each  eye ;  on  directing  the  eyes  to  the  place  of  the  object  the 
two  images  will  unite,  and  the  converse  relief  be  perceived.  .  .  . 
The  field  of  view  is  very  small,  on  account  of  the  distance  at 
which  it  is  necessary  to  place  the  lenses  from  the  eyes.  .  .  .  The 
inverted  images  of  the  lenses  may  be  thrown  upon  a  plate  of 
ground  glass  as  in  the  case  of  the  ordinary  camera  obscura,  and 
may  be  then  caused  to  unite  by  the  means  employed  in  any  form 
of  the  refracting  stereoscope  "  (16).  {b)  Wood's  pseudoscope 
puts  this  idea  of  Wheatstone's  into  compendious  form.  It  con- 
sists of  a  Brewster  stereoscope,  from  which  the  slide  carrier  and 
bar  have  been  removed,  and  which  is  fitted  with  a  pair  of  black- 


{  4S.    Thi  Pseudoscopt  399 

cned  tubes  screwed  to  the  posterior  surface  of  the  hood.  Within 
these  tubes  slide  two  others,  closed  at  their  farther  ends  by 
double  convex  lenses.  An  extra  handle  enables  the  observer  to 
adjust  the  length  of  tube  to  suit  his  eyes.  Conversion  is  of  the 
third  type  (inversion )l  This  somewhat  impairs  the  value  of  the 
instrument  for  general  pur- 
poses :  on  the  other  hand, 
the  field  is  large  and  clear. 
—  Jastrow,  Psychol.  Rev., 
vii.,  48  ;  R.  W.  Wood,  Sci- 
ence, Novr.  3,  1899. 

Preliminaries  andQues- 
TiON  (2X  —  We  may   again 

quote Wheatstone.     "When     c-      o        «»    j.   ,     •    , 

^  ,  Fig.  83,  —  Wood's  lenticuUr  pteadotcope. 

the    pseudoSCOpe    is    so   ad-  Chicmgo  Ub.  Supply  Co..  18. 

justed  as  to  see  a  near  object 

while  the  optic  axes  are  parallel,  to  view  a  more  distant  object 
with  the  same  adjustment  the  axes  must  converge,  and  the 
more  so  as  the  object  is  more  distant ;  all  nearer  objects  than 
that  seen  when  the  axes  are  parallel,  will  appear  double,  be- 
cause the  optic  axes  can  never  be  simultaneously  directed  to 
them.  If  this  instrument  be  so  adjusted  that  very  distant  objects 
are  seen  single  when  the  eyes  are  parallel,  all  nearer  objects  will 
appear  double,  because  the  optic  axes  can  never  converge  to  make 
their  binocular  images  coincide.  If  the  attention  is  required  to 
be  devoted  to  an  object  at  a  particular  distance,  the  best  mode 
of  viewing  it  with  the  pseudoscope  is  to  adjust  the  instrument 
so  that  the  object  shall  appear  at  the  proper  distance  and  of  its 
natural  size.  In  this  case  the  more  distant  objects  will  appear 
nearer  and  smaller,  and  the  nearer  objects  will  appear  more 
distant  and  larger"  (12)^  The  first  part  of  the  quotation  ac- 
counts in  some  measure  for  the  difficulty  experienced  by  begin- 
ners in  using  the  instrument ;  the  latter  part  explains  our  fixation 
of  the  cross  upon  the  screen. 

Experiment  (i).  —  The  nearer  ball  or  rod  seems  to  be  the 
more  remote,  the  left-hand  object  the  right-hand,  and  vice 
versa.  The  illusion  persists  when  the  number  of  objects  is 
increased. 


300  Visual  Space  Perception 

Experiment  (2).  —  In  every  case  there  is  conversion  of  the 
hoof>-curvature. 

Experiment  (3).  —  It  is  probable  that  the  cone  will  appear, 
for  a  second  or  two,  in  normal  relief.  Then  the  apex  gradually 
begins  to  retreat ;  the  whole  cone  '  telescopes,*  and  a  hollow 
cone  is  perceived.  In  the  second  part  of  the  experiment  the 
same  process  is  repeated,  in  the  opposite  direction.  The  con- 
version requires  less  and  less  time  as  practice  is  continued. 

Experiment  (4).  —  O  must  report,  as  accurately  as  possible, 
the  appearance  of  the  pseudoscopic  field.  He  should  note  the 
fluctuations  of  relief  that  appear  in  one  and  the  same  object,  and 
should  attempt  to  grade  the  objects  in  order  of  difficulty  of  con- 
version. At  first,  as  Sanford  says,  "the  pseudoscopic  effect 
seems  quite  capricious."  Presently,  however,  as  the  observer 
comes  to  know  what  to  look  for,  the  objects  sort  themselves  out : 
those  are  easily  converted  whose  'converse  has  a  meaning,'  i.e.^ 
whose  conversion  is  not  opposed  by  central  factors  ;  and  those 
change  with  difficulty  or  not  at  all  whose  converse  is  meaning- 
less, />.,  whose  conversion  is  opposed  by  central  factors,  by  the 
'apperception'  of  the  binocular  image.  If  the  cortex  is  set 
obstinately  for  'cup'  it  is  useless  for  the  eyes  to  say  'sphere.* 
To  analyse  the  central  factors  by  introspection  is  exceedingly 
difficult.  The  visual  images  come  to  us,  so  to  speak,  with  the 
recognition-mark  upon  them ;  and  the  only  thing  that  militates 
against  conversion,  so  far  as  introspection  is  concerned,  may  be 
some  muscular  attitude,  or  organic  complex,  which  constitutes 
the  'feel*  of  familiarity.  Logically,  therefore,  the  classification 
of  objects  as  just  proposed  is  fairly  easy ;  psychologically,  we 
have  no  criterion  other  than  the  intensity  of  the  recognition- 
mark. —  Wheatstone,  13  ;  Kiilpe,  Outlines,  171  ;  Titchener,  Out- 
line, 275  ;  Bentley,  Amer.  Journ.  of  Psych.,  xi.,  i  ff. 

We  assume,  in  the  above  discussion,  that  monocular  criteria 
are  ruled  out.  When  we  turn  the  pseudoscope  upon  a  group  of 
objects  (whether  these  are  arranged  before  the  screen  or  regarded 
as  they  lie  in  the  room  or  landscape)  such  criteria  inevitably  come 
into  play. 

Experiment  (5).  —  The  more  remote  ball  appears  to  O  to  be 
swinging  not  in  a  straight  line  but  in  a  circle  or  ellipse.     As  it 


$  4B,    Th€  Pseudoscopt  501 

disappears  behind  the  near  ball,  it  looks  farther  off;  as  it  re* 
ppears,  it  comes  to  the  front  again. 

The  pseudoscopic  effect  is  destroyed  near  the  table,  but  per- 

sts  above.  If  it  persists  completely,  the  pencils  seem  to  be 
rossed;  if  it  persists  only  partially,  they  incline  towards  each 
other. 

The  experiment  shows  clearly  the  effect  of  the  fourth  monoc- 
ular criterion  :  interposition. 

E.XPERIMENT  (6).  —  As  (?  looks  along  the  line  mn,  the  large 
square  readily  comes  up  to  the  front  of  the  two  middle-sized 
squares.  The  small  square,  on  the  other  hand,  lags  behind. 
Even  if  it  comes  to  the  front  of  the  two  middle-sized  squares, 
it  is  still  farther  off  in  the  pseudoscopic  field  than  the  largest 
square.  The  experiment  shows  the  effect  of  the  fifth  criterion  : 
magnitude  of  retinal  image. 

Experiment  (7).  —  As  O  looks  along  the  line  mn,  the  two 
•.rther  rings  (white  and  grey)  come  up  before  the  two  front  rings 
(white).  It  will  be  noticed,  however,  that  the  grey  ring  lags 
behind  its  white  companion  ;  so  that,  under  favourable  condi- 
tions, the  far  white  ring,  the  grey  ring,  and  one  of  the  near 
white  rings  seem  to  lie  in  the  same  straight  line,  the  far  white 

ng  nearest  the  observer. 

The  experiment  succeeds  best  in  a  dull  twilight.  In  any  case, 
the  light  must  be  distributed  with  perfect  evenness  over  the 
screen  and  wires. 

If  the  laboratory  has  no  suitable  grey-covered  wire,  a  black 
wire  may  be  taken  and  lightly  chalked  over.  It  should  be  noticed 
that,  if  the  four  rings  are  observed  in  monocular  vision,  without 
'  he  pseudoscope,  the  grey  ring  looks  farther  off  than  the  corre- 
i)onding  white  ring  (second  criterion  ;  indistinctness  of  outline). 
This  illusion  is  strong  enough  to  persist  under  pseudoscopic 
conditions. 

Experiment  (8X — The  one  cone  telescopes  readily;  the  other 
with  difficulty,  or  not  at  all.  If  O  knows  the  side  from  which 
the  illumination  came,  he  will  probably  say  positively  that  the 
originally  hollow  cone  looks  hollow,  while  the  originally  project- 
ing cone  merely  flattens  or  undergoes  a  very  gradual  inversion. 
If  he  does  not   know,  he  will  be  able  to  invert  either  cone, 


302  Visual  Space  Perception 

according  to  the  side  from  which  he  supposes  the  light  to  be 
coming.  The  experiment  shows  the  effect  of  the  third  criterion  • 
distribution  of  light  and  shade. 

Experiment  (9).  —  The  hollow  mask  is  very  easily  converted 
into  a  projecting  face.  On  the  other  hand,  the  mask-face  is 
only  with  very  great  difficulty  convertible  into  a  hollow.  Its 
appearance  is  changed :  the  nose  seems  to  be  driven  into  the 
face,  and  the  chin  and  forehead  protrude  abnormally ;  but,  for  a 
long  time,  it  persists  as  a  face.  Steady  fixation  will,  in  most 
cases,  secure  the  required  conversion,  —  especially  if  O  has 
handled  the  mask  beforehand,  and  is  thus  familiar  with  the  look 
of  the  painted  interior. 

In  this  case,  the  apperceptive  or  central  factors  are,  at  first, 
strong  enough  entirely  to  outweigh  the  perceptive  or  periph- 
eral. In  the  case  of  the  human  face,  the  central  factors  are 
still  stronger.  James  says  that  the  features  of  the  living  face 
obstinately  refuse  to  be  converted  by  the  pseudoscope  (Princ.  of 
Psychol.,  ii.,  258).  Wheatstone,  however,  effected  the  conver- 
sion after  *'  a  fixed  stare  of  more  than  half  an  hour  "  (Edinburgh 
Review,  1858,  460).  The  author  once  succeeded  in  obtaining 
such  a  conversion,  and  in  maintaining  it  for  a  few  seconds,  at  a 
time  when  he  had  had  a  very  unusual  course  of  practice  with 
busts  and  casts,  some  of  which  were  tinted  :  but  the  success  has 
remained  unique.  —  For  a  study  of  central  vs.  peripheral  pro- 
cesses, see  Pillsbury,  Amer.  Journ.  of  Psychol.,  viii.,  315  ff. 

Question  (3)  No.  "The  refraction  of  the  rays  of  light  at  the 
incident  and  emergent  surfaces  of  the  prisms  enables  the  reflex- 
ion of  an  object  to  be  seen  when  the  object  is  even  behind  the 
prolongation  of  the  reflecting  surface,  .  .  .  and  thus  the  binoc- 
ular image  may  be  seen  in  the  same  place  as  the  object  itself, 
whereas  the  images  cannot  be  made  by  plane  mirrors  thus  to 
coincide"  (Wheatstone).  Let  the  student  demonstrate  this 
statement  by  a  diagram. 

(4)  "  The  reason  is  this :  that  [in  the  pseudoscope]  the  pro- 
jections to  each  eye  are  separately  reflected,  still  remaining 
presented  to  the  same  eye,  whereas,  by  the  reflexion  of  the 
object  itself  [in  a  mirror],  not  only  are  the  projections  reflected, 
but  they  are  also  transposed  from  one  eye  to  the  other ;  and 


i  49*   Optical  Illusions  303 

these  circumstances  occurring  simultaneously  reproduce  the 
>rroal  relief"  (Wheatstone).  In  terms  of  Fig.  25  of  the  text, 
a  mirror  will  change  a  to  if.  The  same  reason  may  be  given 
for  the  fact  that  inversion  of  an  actual  object  does  not  convert 
its  relief  (a  becomes  (!\  The  student  should,  again,  be  required 
to  draw  explanatory  diagrams. 

(5)  "The  conversion  of  distance"  in  the  pscudoscope,  like 
the  perception  of  distance  in  the  stereoscope,  "  takes  place  only 
within  those  limits  in  which  the  optic  axes  sensibly  converge, 
or  the  pictures  projected  on  the  retinae  are  sensibly  dissimilar. 
Beyond  this  range  there  is  no  mutual  transposition  of  the 
apparent  distances  of  objects  with  the  pseudoscope ;  a  distant 
view  therefore  appears  unchanged  "  (Wheatstone). 


BZPBRIMBHT  ZZIX 

{  49.  Yiinal  Space  Pereeption :  the  Oeometrioal  Optical  lUa- 
L  —  The  main  current  of  work  in  a  science  is  interrupted, 
from  time  to  time,  by  some  eddy  of  special  interest.  A  few 
years  ago  the  *  kinaesthetic  *  sensations  were  attracting  what 
seemed  to  be  more  than  their  due  share  of  psychological  atten- 
tion ;  and  more  recently  the  'geometrical  optical  illusions '  have 
loomed  very  large  in  the  pages  of  the  psychological  journals. 
The  right  way  to  approach  a  subject  of  this  kind  is  to  take  the 
literature  as  a  whole :  to  trace  the  conditions  which  have  led 
several  observers,  independently,  to  a  study  of  the  same  or  similar 
phenomena,  and  which  have  prepared  still  other  workers  in  the 
field  to  offer  expert  criticism,  at  short  notice,  of  the  results  and 
theories  first  published ;  and,  in  the  light  of  these  conditions,  to 
read  synoptically  all  that  has  been  written,  not  losing  oneself  in 
details,  but  keeping  watch  throughout  for  the  broader  psycho- 
logical principles  that  underlie  the  detailed  discussions.  There 
must,  in  the  present  case,  have  been  something  in  the  psycho- 
logical atmosphere  that  was  favourable  to  the  growth  of  an 
Ulusion-literature ;  and  the  profit  to  be  drawn  from  this  literature 
is,  most  assuredly,  not  the  mere  collection  of  possibilities  of 
explaining  a  particular  figure,  —  though  the  understanding  of 
these  possibilities  is  no  small   matter,  and   the  experimental 


304  Visual  Space  Perception 

methods  devised  for  the  study  of  particular  figures  are  no  small 
gain  to  the  science,  —  but  rather  the  grasp  of  principles:  the 
clarifying  of  one's  idea  of  spatial  contrast,  for  instance,  or  the 
weighing  of  arguments  for  and  against  the  '  perception  *  and  the 
'judgment  *  theories  of  optical  illusions  at  large,  or  the  estimation 
of  a  *  genetic '  as  against  a  *  physiological '  or  *  nativistic  *  theory 
of  space  perception. 

Unfortunately,  study  and  appreciation  of  this  sort  demand 
more  time  and  more  knowledge  than  are  available  in  a  first 
laboratory  course.  The  teacher  is  therefore  met  by  the  old 
pedagogical  difficulty.  Shall  he  try  to  work  up  the  material  into 
a  coherent  system,  at  the  risk  of  being  one-sided }  Or  shall  he 
take  the  student  over  the  whole  ground,  at  the  risk  of  being 
scrappy }  The  author,  after  experience  of  both  alternatives,  has 
decided  in  favour  of  the  former.  In  following  Wundt's  exposi- 
tion, the  student  is,  perhaps, — one  might  almost  say  'is  prob- 
ably '  —  led  to  underestimate  the  complexity  of  the  problems 
before  him.  But,  at  any  rate,  he  learns  a  method ;  he  realises 
that  the  way  to  solve  a  problem  is  to  grapple  with  it  steadfastly, 
consistently,  systematically.  On  the  other  hand,  if  he  is  set 
down  before  separate  illusion-figures,  and  required  to  tabulate 
all  the  principles  of  explanation  that  different  writers  have 
employed,  he  comes  to  think  (what  is  emphatically  not  true) 
that  these  '  principles '  are  very  much  a  matter  of  guesswork, 
and  that  one  way  of  explaining  a  psychological  phenomenon  is 
as  good  as  another.  He  has  not  the  perspective  that  would 
enable  him  to  refer  the  various  explanations  to  their  proper 
psychological  places;  he  has  not  traced  conditions. 

There  is  a  further  point.  The  one-sidedness  can  be  corrected 
more  easily  and  effectually  than  the  scrappiness.  The  author 
has  been  accustomed,  at  the  conclusion  of  the  Experiment,  to 
run  over  in  class  the  proposed  explanations  of  the  M tiller- Lyer 
(arrowhead  and  feather)  illusion.  The  variety  of  factors  to 
which  these  explanations  appeal  comes  with  something  of  a 
shock  to  the  student.  But  the  Instructor  can  lessen  the  shock, 
by  giving  the  novel  principles  their  historical  and  systematic 
setting  ;  while  the  student  still  has  the  Wundtian  canons  firmly 
in  mind,  can  compare  the  range  of  the  new  principles  with  their 


§  49-    Optical  lUusums  305 

range,  can  always  come  back  to  them  when  he  seems  to  be  losing 
his  bearings  in  the  multitude  of  details,  and  may  very  well  be 
incited  by  the  clash  of  ideas  to  investigation  on  his  own  account. 
Scrappiness,  on  the  contrary,  is  apt  to  mean  a  self-satisfied  dilet- 
tantism. You  can  meet  a  prejudice  by  giving  it  the  lie  direct ; 
but  how  are  you  to  convince  a  shallow  mind  that  other  minds  are 
deeper  than  itself  ? 

The  following  are  the  most  important  literary  references. 

( 1 )  SysUmatk  Discussums.  —  W.  Wundt,  Die  geometrisch-optischen  Tiiuscb- 

uQgen.     Leipzig,  Teubncr,  1898. 
Th.  Lipps»  Raumaesthetik  uDd  geometrisch-optische  Tauschungen.    Leip- 

ng,  Baurth,  1897. 
A.   Thi^,  Ueber   geometrisch-optische   Tauschungen.      In    Wundt*s 

Philosophiache  Studien,  xi.,  1895, 307, 603 ;  xii.,  1896,  67.     EniDliasises 

perspective  as  a  principle  of  explanation. 
E.  C.  Sanford,  A  Course  in  Experimental   Psychology,   loyo,  z\z  ff. 

Diagrams,  with  **  brief  commentary  .  .  .  intended  merely  as  a  sugges- 

tion  of  the  views  held  with  regard  to  them,  not  as  an  exposition  or 

criticism  of  those  views." 
J.   I.    Hoppe,  Psychologisch-physiologische  Optik.     Leipzig,  Wigand, 

1881. 
To  these  may  be  added:  Helmholtz,  Phys.  Optik,  2d  edn.,  1896,  705; 

Wundt,  Phys.  Psych.,  4th  edn.,  1893,  ii.,  137 ;  James,  Princ.  of  Psych., 

1890,  ii.,  231,  248,  264;  Bowditch,  in  HowelPs  American  Textbook  of 

Physiology,  189(5,  789^^06. 

(2)  IJbtsiams  of  ReversibU  Perspective,  —  H.  Beaunis,  Nouvcaux  ^l^ments  de 

physiologie  humaine.    Paris,  1888,  ii.,  569. 
W.  Filehne,  Zeits.  f.  Psych.,  xvii.,  1898,  19. 
H.  von  Helmholtz,  Phys.  Optik,  771. 

E.  Heriog,  in  Hermann's  Handbuch  der  Physiologie,  iii.,  i,  1879,  579. 
J.  L  Hoppe,  Psych.-phys.  Optik,  64,  203,  251,  274. 
W.  James,  Princ  of  Psych.,  il,  254-256,  265. 
J.  Jastrow,  Pop.  Sd.  Monthly,  xxxiv.,  1889,  150;  liv.,  1898-9,  306. 
N.  Lange,  Philos.  Studien,  iv.,  1888,  406. 
T.  Lipps,  Raumaesthetik,  73. 
J.  Loeb,  PflUger's  Archiv,  xl.,  1887,  274,  281. 
E.  Mach,  Beitrage  zur  Analyse  der  Empfindungen,  1886,  87,  94,  96  f-; 

Eng.  trans.,  1897,  91,  99,  loi. 
L.  A.  Necker,  Poggendorif's  Annalen,  xxvii.,  1833,  497. 
J.  OppeU  Poggendorff's  Annalen,  xcix.,  1856,  466. 
£.  C.  Sanford,  Coarse,  215,  255. 
H.  Schroder,  Poggendorff's  Annalen,  cv.,  1858,  298. 
A.  Thi^ry,  Philos.  Studien,  xi.,  1895,  317. 

X 


3o6  Visual  Space  Perception 

C.  Wheatstone,  Phil.  Trans.,  1838,  381. 
S.  Witasek,  Zeits.  f.  Psych.,  xix.,  1899,  81-174. 

W.  Wundt,  Phys.  Psych.,  ii.,  200 ;  Tauschungen,  58  ff. ;  Philos.  Studien, 
xiv.,  1898,  27  ff. 

(3)  Variable  Illusions  of  Extent.  — H.  Aubert,  Physiol,  d.  Netzhaut,  1865, 

264. 
F.  Auerbach,  Zeits.  f.  Psych.,  vii.,  1894,  152. 
A.  Binet,  Revue  philosophique,  xl.,  1895,  11;  Annde  psychologique,  i., 

1894,  328. 
J.  J.  van  Biervliet,  Revue  philosophique,  xli.,  1896,  169. 

F.  Brentano,  Zeits.  f.  Psych.,  iii.,  1892,  349;  v.,  1893,  61 ;  vi.,  1893-4,  i. 
C.  Brunot,  Revue  scientifique,  Hi.,  1893,  210. 

J.  Delbceuf,  Bull,  de  I'Acad.  roy.  de  Belgique,  3  s^rie,  xxiv.,  1892,  12; 

Revue  scientifique,  li.,  1893,  237. 
W.  Einthoven,  Pfluger's  Archiv,  Ixxi.,  1898,  i. 
H.  von  Helmholtz,  Phys.  Optik,  705. 

E.  Hering,  Beitrage  zur  Physiologic,  i.,  1861,  66;  Hermann's  Hdbch., 
iii.,  I,  554. 

G.  Heymans,  Zeits.  f.  Psych.,  ix.,  1895-6,  221. 

J.  Jastrow,  Amer.  Journ.  of  Psych.,  iv.,  1891-2,  396. 

H.  W.  Knox  and  R.  Watanabe,  Amer.  Journ.  of  Psychol.,  vi.,  1893-5, 

413*  509- 
O.  KUlpe,  Outlines  of  Psych.,  1895,  366. 
A.  Kundt,  Poggendorff's  Annalen,  cxx.,  1863,  128. 
W.  Liska,  Du  Bois-Reymond's  Archiv,  1890,  326. 
T.  Lipps,  Zeits.  f.  Psych.,  iii.,  1892,  501 ;  Raumaesthetik,  70,  141   (146, 

161;  150;  363;  237,241,251,254,364;  128,135,137;  72). 
J.  Loeb,  PflUger's  Archiv,  Ix.,  1895,  509. 
H.  Messer,  Poggendorff's  Annalen,  clvii.,  1876,  172. 

F.  C.  MUller-Lyer,  Du  Bois-Reymond's  Archiv,  1889,  S.  B.,  263;  Zeits. 
f.  Psych.,  ix.,  1895,  I ;  x.,  1896,  421. 

J.  Oppel,  Jahresber.  d.  physikal.  Ver.  zu  Frankfurt  a.  M.,  1856-7,  51 ; 

1860-1,  35. 
E.  C.  Sanford,  Course,  229,  233. 
A.  Thidry,  Philos.  Studien,  xii.,  1896,  67. 
W.  Wundt,  Phys.  Psych.,  ii.,  142 ;  Tauschungen,  82. 

(4)  Constant  Illusions  of  Extent.  —  A.  Chodin,  Arch.  f.  Ophthalmologic, 

xxiii.,  I,  1877,99. 
J.  Delbceuf,  Bull,  de  TAcad.  roy.  de  Belgique,  2  sdrie,  xix.,  2,  1865,  9. 
R.  Fischer,  Arch.  f.  Ophthalmologic,  xxxvii.,  i,  1891,  97;    xxxvii.,  3, 

1891,  55. 
H.  von  Helmholtz,  Phys.  Optik,  684,  702. 
E.  Hering,  Beitrage  zur  Physiol.,  v.,  1864,  355 ;  Hermann's  Hdbch.,  iii., 

I,  1879,  553. 
W.  Holtz,  Wiedemann's  Annalen,  x.,  1880,  158. 


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(7)  Illusions  of  Association.  —  H.  Aubert,  Physiol.  Optik,  1876,  629. 
J.  M.  Baldwin,  Psychol.  Rev.,  ii.,  1895,  244. 

T.  Lipps,  Helmholtz  Festgruss,  300;    Zeits.  f.  Psych.,  xii.,  1896,  52; 

Raumaesthetik,  100;  104  f. 
A.  Hofler,  Zeits.  f.  Psych.,  x.,  1896,  99. 
J.  Loeb,  Pfluger's  Arch.,  Ix.,  1895,  509. 

F.  C.  Mullcr-Lyer,  Du  Bois-Reymond's  Arch.,  1889,  S.  B.,  263;  Zeits.  f. 
Psych.,  ix.,  1895,  3  ;  X.,  1896,  421. 

E.  C.  Sanford,  Course,  238,  246,  253. 

A.  Thidry,  Philos.  Studien,  xii.,  1896,  83. 

W.  Wundt,  Phys.  Psych.,  ii.,  146,  150;  Tauschungen,  137. 

W.  von  Zehender,  Zeits.  f.  Psych.,  xx.,  1899,  106  f. 

(8)  Illusions  with  Complication  of  Conditions.  —  J.  Delboeuf,  Revue  scien- 

tifique,  Ii.,  1893,  237  ;  Bull,  de  TAcad.  roy.  de  Belgique,  2  s^rie,  xx.,  no. 
6,  1865,  70. 

F.  B.  Dresslar,  Amer.  Jour,  of  Psych.,  vi.,  1893-5,  275. 
H.  von  Helmholtz,  Phys.  Optik,  707. 

E.  Hering,  Hermann's  Hdbch.  d.  Physiol.,  iii.,  i,  1879,  372' 

G.  Heymans,  Zeits.  f.  Psych.,  xiv.,  1897,  117. 

T.  Lipps,  Helmholtz  Festgruss,  1891,  233,  290;  Raumaesthetik,  321  (389, 
398;  108,  plate  at  end;  72,  291;  313,  317);  Zeits.  f.  Psych.,  xv., 
1897-8,  137;  xviii.,  1898,  433,  435. 

J.  Loeb,  Pflugers  Archiv,  Ix.,  1895,  512. 

W.  L^ka,  Du  Bois-Reymond's  Archiv,  1890,  326. 

F.  C.  MUller-Lyer,  Du  Bois-Reymond's  Archiv,  1889,  S.  B.,  263 ;  Zeits. 
f.  Psych.,  X.,  1896,  421. 

J.  Oppel,   Jahresber.   d.   physikal.  Ver.   zu   Frankfurt  a.   M.,   1856-7, 

48. 
E.  C.  Sanford,  Course,  227,  243,  246,  251. 
A.  Thi^ry,  Philos.  Studien,  xi.,  1895,  357;  xii.,  1896,  94,  108. 
W.  Wundt,  Phys.  Psych.,  ii.,  148,  151  ;  Tauschungen,  145. 

(9)  General   Theoretical  Discussions.  —  E.  B.    Delabarre,  Amer.  Journ.  of 

Psych.,  ix.,  1898,  573. 
T.   Lipps,   Raumaesthetik,    1-69    (esp.   61    ff.) ;    Zeits.   f.    Psych.,  xii., 

1896,  39. 
A.  Thi^ry,  Philos.  Studien,  xi.,  1895,  307,  603 ;  xii.,  1896,  67. 


§  49-    Optical  lUusions  309 

S.  Wiusek,  Zeits.  f.  Ptych.,  xiz.,  1899,  81. 

W.  Wondt,  TSuschungen,  157;  Philos.  Studicn,  xiv.,  1898,  i. 

W.  voo  Zebender,  Zeits.  f.  Psyche  xviii^  1898,  91-98. 


We  come  now  to  the  Experiment,  with  Wundt's  figures  and 
interpretations.  The  diagrams  which  show  these  illusions  have 
become  more  or  less  common  property ;  but  the  author  has  at- 
tempted to  refer  them  to  their  first  inventors  or  observers.  For 
more  careful  work  than  the  Experiment  demands,  the  figures 
should  be  drawn  on  a  larger  scale  and  on  separate  sheets  of 
paper,  so  that  they  stand  practically  alone  in  the  visual  field. 
Those  that  show  perspective  may  be  constructed  of  narrow 
strips  of  white  paper  pasted  on  black  cardboard  backgrounds. 
Whether  or  not  the  student  make  these  larger  diagrams  for 
himself,  the  Instructor  should  have  a  few  prepared  as  large  wall- 
diagrams  :  the  author  recommends  for  this  purpose  Schroder's 
stair-figure,  Necker's  cube,  Helmholtz'  cross-lined  squares,  the 
Miiller-Lyer  figure,  the  Oppel-Delboeuf-Kundt  cross,  Hering's 
parallels,  Wundt's  parallels,  Zollner's  figure,  Helmholtz*  chess- 
board (von  Recklinghausen's  illusion),  Poggendorff's  figure  and 
Miiller-Lyer's  broken  circle.  Some  authors  advise  the  demon- 
stration of  illusions  by  means  of  wire  models  ;  and  it  is  true  that 
the  apparent  lengthening  or  shortening  of  a  piece  of  wire  is  more 
striking  than  the  lengthening  or  shortening  of  a  pen-stroke. 
Half-a-dozen  pairs  of  wires,  showing  various  forms  of  the  Miiller- 
Lyer  illusion,  can  be  obtained  from  any  tinsmith,  or  made  in  the 
Laboratory;  they  are  very  effective  for  class  purposes.  The 
author  has  also  used  for  some  years  a  large  movable  model  of  the 
Miiller-Lyer  figure :  two  strips  of  black  card  (the  two  constants) 
are  pasted  upon  a  sheet  of  heavy  millboard,  and  a  number  of 
loose  back  strips,  of  varying  length,  provided.  The  loose  strips 
are  put  together,  V-wise,  by  a  pin,  which  is  then  thrust  through 
the  extremity  of  the  fixed  line.  It  is  thus  possible  to  vary  the 
length  and  the  angle  of  the  oblique  attachments,  and  to  modify 
or  convert  the  illusion  before  the  eyes  of  the  observer.  The 
same  principle  is  employed  in  Miinsterberg's  Pseudoptics. 

It  should  be  noted  that  Wundt  is  followed,  in  this  Experiment, 
only  to  his  proximate  interpretations.     How,  for  instance,  the 


3IO  Visual  Space  Perception 

increase  or  decrease  of  expenditure  of  muscular  energy  comes  tc 
have  an  influence,  on  his  theory,  upon  our  perceptions  of  space, 
is  a  point  that  is  not  here  explained.  The  explanation  must 
come  in  a  systematic  lecture  course.  The  points  emphasised 
here  are  the  factual  influence  of  fixation  and  eye-movement, 
especially  in  the  illusions  of  reversible  perspective,  and  the  veri- 
fication of  this  influence  by  introspection  throughout  the  five 
principal  illusion-series.  At  the  conclusion  of  the  Experiment, 
and  before  the  Questions  are  attempted,  the  contents  of  Wundt's 
final  section  (§  lo,  i68  if.)  —  except  where  the  answers  to  the 
Questions  are  anticipated  by  it  —  should  be  given  to  the  student. 

Experiment  (  i  ).  —  (i. )  Fixation  oiain  A  and  B  brings  a  out, 
towards  the  observer.  The  figures  are  thus  seen  in  perspective 
as  crosses :  the  line  cd  is  constant  in  the  plane  of  the  paper,  the 
limb  ab  stretches  across  it,  into  the  space  behind  the  paper.  As 
the  eye  moves  to  by  the  point  b  comes  out  to  the  observer ;  the 
perspective  is  reversed.  Note  the  tendency  (not  mentioned  in 
the  text)  to  see  the  angles  of  intersection  all  alike  as  right 
angles. — In  6' and  D  there  is  no  line  of  constant  orientation  ;  it 
is  only  the  point  of  intersection  that  remains  in  the  plane  of  the 
paper.  Hence  fixation  of  a  brings  out  both  a  and  d  towards  the 
observer ;  fixation  of  b  brings  out  both  b  and  c.  —  The  two  per- 
spectives may  be  obtained  with  E  and  F.  There  is,  however,  a 
tendency  to  regard  the  lower  part  of  a  linear  figure  as  the  part 
that  is  nearer  to  the  observer.  Hence  the  illusion  with  fixation 
of  b  is  more  difficult  to  obtain  than  that  with  fixation  of  a. 
Notice  the  influence  of  this  tendency  in  C  and  D.  —  G  and  H 
repeat  the  illusions  of  A  and  B.  We  see  telegraph-poles  in  place 
of  the  right-angled  crosses.  —  The  student's  attention  should  be 
called  to  the  extreme  difficulty  with  which  any  considerable 
perspective  effect  is  obtainable  from  a  simple  vertical  or  simple 
horizontal  line. 

(ii.)  As  a  general  rule,  A  is  seen  with  the  edge  be  convex. 
Fixation  of  any  point  on  bCy  or  movement  along  it,  maintains 
this  perspective.  Fixation  of  any  point  upon  ad  or  cf  brings 
these  lines  forward.  Movement  from  a  or  c  to  by  and  movement 
from  f  or  d  to  Cy  render  be  concave.  The  opposite  movements 
restore  its  convexity. 


§  49*   liiftsians  of  RcversibU  Pfrspgctivf  3 1 1 

Note  the  tendency  to  see  the  figures  ahed,  hcfe  as  right-angled 
parallelograms. 

L0tl^s  Exptrimimts,  — At  a  moment  when  the  figure  appears  convex,  move 
h  rapidly  away  from  the  observing  eye :  the  perspective  changes.  Now  move 
it  quickly  in  again :  the  convexity  is  restored.  The  reason  is,  that  movement 
away,  when  some  point  on  Ar  is  under  fixation,  necesaiutes  an  eye-movement 
in  the  direction  ab  or  cb ;  whereas  movement  towards  the  observer  implies  eye 
movement  in  the  direction  Ac  or  Ar.  —  Bring  up  a  pencil-point  between  the 
figure  and  the  observing  eye.  Move  it  towards  the  figure:  d^  is  concave. 
Move  it  towards  the  e}*e :  Ar  is  convex.  The  reason  is,  again,  that  movement 
of  the  point  towards  the  figure  means  an  eye-movement  in  the  direction  ab  or 
^A,  while  movement  towards  the  observer  means  eye-movement  in  the  direc- 
tion Atf  or  6c.  If  the  movement  of  figure  or  pencil  is  so  slow  that  the  eye  can 
maintain  its  original  fixation,  there  is  no  shift  of  perspective. 

Figure  B  is  ordinarily  seen  as  a  tetrahedron,  with  the  edge  </A 
convex.  Fixation  of  a  point  on  this  edge,  or  movement  of  the 
eye  in  the  directions  da,  bc^  maintains  this  perspective ;  fixation 
of  a  point  upon  ac,  ad  or  cd,  and  movement  of  the  eye  in  the 
directions  ab,  cb,  reverse  the  perspective.  The  secondary  modi- 
fications are  transparency  and  shift  of  orientation.  The  line  ac 
is  seen  behind  bd,  or  vice  versa  ;  and  the  vertical  axis  of  the  tetra- 
hedron inclines  in  the  one  case  towards,  in  the  other  case  away 
from  the  observing  eye. 

Loeb's  experiments  may  be  repeated  with  this  figure. 

The  figure  is  capable  of  four  other  interpretations.  It  may 
appear,  not  as  a  tetrahedron  at  all,  but  as  a  figure  composed  of 
the  junction  of  two  plane  triangles.  Fixate  the  point  b :  the  tri- 
angle abc  is  turned  towards  the  observer.  Fixate  some  point 
upon  ac  (e.g.,  the  point  of  intersection  of  ac  and  bd^ :  the  triangle 
abc  is  bent  away  from  the  observer.  The  fixation  must  be  steady 
and  continuous;  and  the  least  eye-movement  means  that  the 
figure  slips  back  into  its  tetrahedral  form.  Finally,  the  figure 
may  appear  as  a  pentahedron,  a  solid  or  hollow  four-sided  pyra- 
mid, whose  apex  is  the  point  of  intersection  of  ac  and  bd.  The 
illusions  are  more  striking  if  the  figure  be  turned  through  45° 
/.  A  and  B  of  Fig.  29,  Pt.  i.)  and  the  sides  cui,  cd  somewhat 
lortened.  The  conditions  of  the  two  perspective  interpretations 
c.in  easily  be  worked  out  by  the  student. 

(iiL)  The  figure  appears  ordinarily  as  a  flight  of  steps.     If  a 


312  Visual  Space  Petxeption 

be  fixated,  or  the  eye  move  from  a  to  b^  this  perception  persists. 
If  ^  be  fixated,  or  the  eye  move  from  b  to  a^  the  figure  appears  as 
an  overhanging  portion  of  a  wall. 

If  a  is  fixated,  and  this  fixation  maintained  while  the  figure  is 
turned  through  i8o®,  the  converse  relief  must,  of  course,  appear. 
This  is  the  explanation  of  Schroder's  statement,  that  the  inver- 
sion of  perspective  occurs  most  easily  with  inversion  of  the  dia- 
gram. Intrinsically,  there  is  as  strong  a  tendency  to  see  the 
flight  of  steps  (to  fixate  b  or  c)  when  the  figure  is  inverted  as 
there  is  to  see  it  (to  fixate  ^)  when  the  figure  is  in  its  normal 
position.  The  tendency  to  fixate  the  lower  end  of  an  oblique 
line  drawn  in  perspective,  and  to  follow  the  lines  of  fixation 
from  below  upwards  rather  than  from  above  downwards,  has 
been  noted  above  under  (i.). 

(iv.)  The  tendency  is  to  see  the  edge  ab  as  nearer  the  observer. 
Fixation  of  any  point  upon  aby  and  eye-movement  in  the  directions 
bfy  bcy  maintain  this  perspective ;  fixation  of  a  point  on  gh^  and 
eye-movement  in  the  directions  gf,  gCy  reverse  it.  A  right-hand 
turn  of  the  figure  through  90°,  making  cd  horizontal,  exaggerates 
the  tendency  to  see  the  edges  be,  ed  as  convex.  Contrariwise,  a 
left-hand  turn,  making  <?/"  horizontal,  exaggerates  the  tendency  to 
see  the  edges  ef,  eh  as  convex.  These  turns  of  the  figure,  there- 
fore, facilitate  the  reversal  of  perspective.  The  reason  is  that 
the  fixation-lines  are  brought  farther  from  the  horizontal,  and 
that  the  general  suggestion  of  perspective  is  thereby  enhanced. 

Note  that  the  figure  in  perspective  is  not  that  of  a  true  cube ; 
the  farther  side  appears  too  large.  It  follows  that  the  angles  of 
the  figure  are  not  all  seen  as  right  angles.  Note  also  that  the 
conversion  of  perspective  is  always  accompanied  by  an  apparent 
turn  of  the  whole  figure  about  a  horizontal  axis. 

Two  other  illusions  are  possible.  Fixate  steadily  and  continu- 
ously an  imaginary  point  lying  midway  between  ab  and  gh.  The 
edges  ab  and  gh  both  appear  convex ;  there  is  no  solid  cube,  but 
two  roofs,  or  two  book-covers,  crossing  each  other  in  a  somewhat 
baffling  way.  Now  fixate  an  imaginary  point  midway  between 
ab  and  ef^  or  gh  and  ed.  The  edges  ab  and  gh  are  both  concave ; 
the  roofs  or  covers  are  open  towards  the  observer.  Neither  illu- 
sion is  easy  to  obtain ;  the  former  is  the  less  difficult  of  the  two. 


§  49-    VariabU  lilusions  of  Extent  3  r  3 

(v.)  Fixation  of  the  centre  of  the  surface  abed  of  A  g^ves  the 
illusion  of  a  solid  prism.  Fixation  of  points  on  cc,  bf  ox  dg 
brings  these  edges  out  towards  the  observer :  this  accords  with 
our  previous  rules.  Movement  of  the  eye  from  any  one  of  these 
lines  along  an  oblique  line  does  not  alter  the  perspective  until 
the  line  hi  or  kl  has  been  passed ;  beyond  this  point,  the  perspec- 
tive is  reversed,  i.r.,  the  apparent  irregularity  comes  into  play. 
Movement  of  the  eye  along^i  or  kl  produces  a  quick  and  confus- 
ing alternation  of  reliefs.  Movement  from  these  lines  along  an 
oblique  line,  if  directed  towards  rr,  makes  the  prism  concave ;  if 
directed  towards  bf  or  dg,  makes  it  convex.  These  results  are 
regular. 

The  student  can  work  out  for  himself  the  corresponding  illu- 
sions of  B.  We  may  have,  from  left  to  right,  hollow-solid,  solid- 
hollow,  or  solid-solid.     The  conditions  must  be  carefully  noted. 

Experiment  (2).  —  (vi.)  It  is  natural  to  estimate  the  lines  and 
distances  oi  A^  B  and  C  by  eye-movement ;  in  D,  however,  the 
middle  division  of  a  arrests  the  eye,  and  the  tendency  is  to 
ike  in  the  whole  line  at  once,  by  a  single  fixation.  The  obvious 
ining,  in  the  way  of  illusion,  is  the  different  apparent  length  of  the 
objectively  equal  distances.  In  At  b  is  the  longer  ;  in  /?,  ^ ;  in  C 
a  and  b  are  longer  than  the  open  space ;  in  Z>,  however,  a  is 
shorter  than  b. 

There  is  a  weak  illusion  of  perspective.  In  A^  a  is  nearer 
than  b\  in  ^,  a  is  nearer;  in  C,  there  is  no  perspective,  only  an 
empty  space  between  a  and  b\  in  />,  ^  is  nearer.  C  shows  that 
the  illusion  of  extent  is  primary,  since  we  have  in  it  an  illusion 
of  extent  with  no  illusion  of  perspective  at  all :  if  the  latter  were 
the  primary  illusion,  we  could  never  have  an  illusion  of  extent 
without  the  presence  of  the  conditioning  perspective  factor. 

The  illusion  of  extent  is  fairly  constant,  whatever  the  positiou 
of  the  figures  ;  the  illusion  of  perspective  is  strongest  when  the 
distances  are  horizontal.  The  illusion  of  extent  is  more  plainly 
seen  with  eye-movement,  the  illusion  of  perspective  with  steady 
fixation. 

E  is  merely  a  variant  oi  C\  a  looks  higher,  and  b  looks  wider 
than  the  objectively  equal  square  c.  Both  a  and  b  are  seen  in 
the  same  plane,  while  c  is  somewhat  nearer  the  observer. 


314  Vistial  Space  Perception 

"  Distances,  the  traversing  of  which  requires  a  movement  of 
regard  that  is  interrupted  by  fixation-points  or  prescribed  by 
fixation-lines,  appear  longer  than  distances  that  can  be  traversed 
without  fixation-points  or  in  complete  freedom,  without  prescrip- 
tion of  path"  (Wundt). 

(vii.)  The  natural  way  of  observing  A  is  to  take  the  horizontal 
line  as  line  of  fixation,  and  to  estimate  the  length  of  the  lines 
ay  b  by  dropping  imaginary  perpendiculars  from  their  points  to 
the  horizontal.  In  A,  b  is  accordingly  longer  than  a.  In  B  and 
C,  where  the  eye  must  traverse  the  lines  a^  b  in  succession,  and 
no  simultaneous  projection  upon  a  horizontal  is  possible,  the 
illusion  disappears.  It  recurs  in  Dy  and  (though  to  a  less  de- 
gree) in  E. 

(viii.)  The  ^-vertical  is  in  every  case  longer  than  the  ^-verti- 
cal. The  illusion  is  most  marked  in  A.  All  three  figures  show 
a  perspective  illusion.  In  Cy  the  illusion  is  that  the  middle  line 
of  a  is  nearer,  and  the  middle  line  of  b  farther,  than  the  lateral 
parallels.  In  A  and  By  the  whole  figure  a  is  nearer  than  b. 
Moreover,  the  oblique  pieces  in  A  give  a  reversible  perspective. 
If  the  eye  passes  from  the  vertical  to  the  oblique  lines,  the  fig- 
ures appear  as  a  roof  or  ridge,  convex  to  the  observer ;  if  the 
eye  passes  from  the  oblique  lines  to  the  vertical  (as  may  easily 
happen  in  b\  the  latter  is  more  remote  from  the  observer. 

Both  illusions  (extent  and  perspective)  persist  when  the  fig- 
ures are  turned.  The  illusion  of  extent  persists  whether  the 
eye  be  moving  or  steadily  fixating ;  the  illusion  of  perspective  is 
enhanced  by  steady  fixation. 

"A  distance  which,  in  virtue  of  its  fixation-lines,  offers  a 
motive  to  the  continuance  of  movement  in  the  same  direction 
is  adjudged  greater,  and  a  distance  which,  in  virtue  of  similar 
lines  in  the  opposite  direction,  offers  a  motive  to  the  inhibition 
of  movement  is  adjudged  less,  than  an  objectively  equal  distance 
in  the  traversing  of  which  such  motives  are  not  operative  " 
(Wundt).  The  lengthening  of  the  ^-lines  is  thus  analogous  to 
the  greater  length  oi  b  m  A  and  By  Fig.  34  of  Pt.  i.  ;  the  short- 
ening of  the  ^-lines  is  analogous  to  the  shortening  of  ^  in  Z^  of 
the  same  Fig.  Note  that  the  word  'motive,'  in  the  quotation,  is 
used  in  a  special  and  technical  sense. 


§  4^  lUusions  of  Constant  Extent ^  Variable  Direction    315 

The  closed  semicircle  in  D  is,  in  principle,  the  half  oi  A  a\ 
the  diameter  is  underestimated,  and  the  whole  surface  of  the 
figure  correspondingly  lessened.  The  squares  of  E  are  a  vari- 
ant of  the  B  figures. 

Experiment  (3). — (ix.)  A  presents  one  monocular  and  two 
binocular  illusions.  In  binocular  vision,  the  vertical  line  appears 
longer  than  the  horizontal  (Oppel);  and  the  upper  vertical  limb 
appears  longer  than  the  lower  (Delboeuf).  In  monocular  vision 
the  outer  horizontal  limb  appears  longer  than  the  inner  (Kundt) 

B,  Ct  D  and  E  show  Oppel's  illusion  ;  B  shows  Delbceuf  s ; 
E  shows  Kundt's.  The  author  has  not  succeeded  in  seeing 
Kundt*s  illusion  in  B ;  the  illusion  is  weak  at  best,  and  in  this 
case  the  influence  of  the  square  and  circle  counteracts  it. 

Wundt  explains  the  illusions  by  reference  to  asymmetries  of 
muscular  action.  The  fact  that  /**  produces  no  illusion,  while  B 
does,  bears  out  the  hypothesis. 

The  angular  illusions  of  B^  which  are  very  striking,  and  will 
probably  be  noticed  by  the  student,  do  not  fall  under  the  present 
heading. 

Experiment  (4).  — (x.)  The  line  ab  in  A  seems  bent  at  Cy  in 
such  a  way  that  a  and  b  are  slightly  lower  than  c.  \x\  B  the 
bend  is  in  the  opposite  direction :  a  and  b  are  slightly  higher 
than  c.  If  c  be  steadily  fixated,  A  appears  as  a  four-rayed  star : 
d  and  e  point  towards,  a  and  b  away  from,  the  observer.  B  ap- 
pears, under  similar  conditions,  as  a  bent  strip  of  metal  or  paper, 
with  the  edge  cd  near  the  observing  eye,  and  the  points  a,  b 
remote.  At  the  same  time  (and  this  is  a  point  that  the  student 
may  miss)  d  seems  to  be  somewhat  nearer  the  eye  than  r,  as  if 
the  upper  portion  of  the  convex  edge  were  tilted  towards  the 
observer. 

The  general  formula  is  that  small  angles  {dca^  ecb  in  A^  and 
doc,  dbc  in  B)  are  overestimated,  and  obtuse  angles  under- 
estimated in  comparison  with  them.  This  must  be  the  primary 
illusion,  since  the  perspective  illusion  is  not  reversible  but  con- 
stant. Moreover,  we  have  the  angle  illusion,  without  any  per- 
spective illusion  at  all,  in  B  of  Fig.  37,  Pt.  i. 

(xi.)  The  parallels  in  A  seem  to  converge,  those  in  B  to 
diverge,  to  right  and  left :  A  is  thus  a  complicated  variant  of  the 


3i6  Visual  Space  Perception 

A  of  Fig.  38  (Pt.  \.\  and  B  a  similar  variant  of  the  B.  The 
illusion  is  reversed,  because  the  acute  angles  formed  by  the  rays 
with  the  parallels  lie  on  opposite  sides  of  the  lines  in  the  two 
figures.  It  is  strongest  at  the  points  ac,  bd,  because  the  angles 
here  are  more  acute  than  they  are  towards  the  centre  of  the  dia- 
grams. 

The  illusion  of  perspective  is  constant ;  the  points  from  which 
the  rays  diverge  are  always  the  points  most  remote  from  the 
observing  eye.  If  the  eye  be  allowed  to  play  over  the  figures, 
the  band  abdc  in  A  takes  the  appearance  of  a  hollow  half-hoop, 
narrower  at  the  sides  than  in  the  distance,  while  in  ^  it  is  a  con- 
vex half-hoop,  narrower  in  the  middle  than  at  the  sides.  With 
steady  fixation,  the  general  perspective  effect  of  the  figures  is 
greatly  increased,  but  the  lines  ab^  cd  appear  parallel,  as  they 
are.     This  last  point  is  important  for  Wundt's  theory. 

(xii.)  There  are  two  illusions  of  direction  in  A.  The  parallel 
vertical  strips  appear  to  converge  and  diverge  alternately  above 
and  below ;  and  the  right  and  left  halves  of  the  oblique  cross- 
pieces  appear  shifted  vertically,  each  in  the  direction  in  which 
it  is  pointing.  The  first  illusion  is  much  more  pronounced 
in  B  than  in  A  ;  the  second  has  no  opportunity  to  show 
itself. 

Both  illusions  are  referrible  to  the  overestimation  of  acute 
angles.  If  the  acute  angles  which  the  oblique  cross-pieces  make 
with  the  verticals  are  subjectively  increased,  the  shift  of  each 
half  follows  as  a  matter  of  course ;  and  it  is  equally  necessary 
that  the  verticals  themselves  shall  diverge  in  the  direction 
towards  which  the  cross-pieces  point,  and  converge  in  the  direc- 
tion from  which  they  point. 

Steady  fixation  of  A  diminishes  (or  even  destroys)  the  illusion 
of  direction,  while  it  brings  out  an  occasional  plastic  effect  from 
one  part  or  other  of  the  figure.  Steady  fixation  of  B  produces 
a  very  strong  perspective  effect.  The  lines  that  are  crossed  by 
horizontal  pieces  are  turned  with  their  upper  ends  towards  the 
observer ;  the  lines  crossed  by  verticals  have  their  lower  ends 
towards  the  observer.  The  whole  figure  thus  seems  to  consist 
of  a  number  of  white  threads,  stretched  alternately  in  opposite 
directions  of  space.    At  the  same  time,  the  longer  lines  are  seen 


§49-    Constant  I UusioHS  of  Directum  317 

to  be  parallel,  and  their  apparent  convergence  is  referred  to 
their  different  spatial  direction.  We  have  again,  therefore,  an 
instance  of  the  compensatory  effect  of  perspective  which,  ac- 
cording to  Wundt,  characterises  this  group  of  illusions. 

(xiii.)  At  first  glance,  the  two  halves  of  the  oblique  line  appear 
shifted,  in  the  vertical  direction,  as  in  Fig.  40,  A  (Pt.  \.\  If  the 
eye  be  moved  slowly  up  and  down  <?,  the  oblique  pieces  may 
seem  to  make  a  sharp  turn  inwards,  above  and  below  the  points 
where  they  really  strike  the  verticals.  The  two  halves  of  the 
oblique  line  are  then  seen  as  continuous  in  direction ;  but  each 
half  has  a  little  hook,  where  it  touches  the  vertical :  it  follows 
the  base  of  the  triangle,  instead  of  the  side. 

Steady  fixation  of  a  point  on  a  brings  out  the  perspective 
effect ;  the  lower  end  of  the  oblique  line  is  nearer  the  observer, 
and  the  two  halves  appear  in  the  same  straight  line  without  any 
hook  or  inward  turn.  The  vertical  strip  a  is  drawn  open,  and 
the  whole  figure  shown  in  black  on  white,  to  avoid  a  possible 
complication  by  irradiation. 

"Wherever  mechanical  movements  are  produced,  of  short 
duration  —  varying  in  the  individual  case  —  and  under  the  same 
conditions,  there  will  be  a  relatively  greater  expenditure  of 
energy  in  the  shorter  than  in  the  longer  movements,  since  it 
requires  more  energy  to  set  a  definite  movement  going  than  to 
continue  a  movement  that  is  already  begun  "  (Wundt).  It  is, 
then,  the  relatively  greater  expenditure  of  muscular  energy  in 
crossing  a  small  angle  that  determines  our  overestimation  of  it. 
Notice  that  this  is  merely  a  proximate  principle  of  explanation  : 
it  still  remains  to  be  shown  how  muscular  energy  becomes  trans- 
lated into  spatial  terms. 

Experiment  (5). — (xiv.)  The  hyperbolas  become  straight 
lines,  so  that  the  figure  looks  like  a  chessboard.  The  squares 
are  of  equal  size,  about  the  centre  of  the  figure ;  towards  the 
periphery  they  may  seem  to  grow  larger,  even  though  the  lines 
of  division  are  directly  vertical  and  horizontal. 

The  perspective  illusion  in  this  case  is  that  of  a  bowl,  turned 
convcxly  to  the  observer;  the  bottom  of  the  bowl  is  flat,  and 
the  whole  surface  is  divided  up  into  equal  squares,  —  the  appar- 
ently larger  being  interpreted  as  the  more  remote.     If  the  eye 


3i8  Visual  Space  Perception 

move  over  the  figure,  we  see  a  concave  bowl ;  the  curved  lines 
are  now  the  determining  factors  in  the  perspective  effect. 

Wundt  compares  the  illusions  of  this  figure  to  the  false  tor- 
sions of  the  right-angled  after-image  projected  on  a  plane  sur- 
face (136).  "With  unmoved  line  of  regard,  we  apprehend  the 
directions  of  lines  seen  in  indirect  vision  as  they  would  neces- 
sarily appear  in  direct  vision  if  the  regard  were  transferred  (with 
unchanged  position  of  the  retinal  image)  from  the  lateral  parts 
of  the  visual  field  to  its  present  point  of  fixation." 

Experiment  (6).  —  (xv.)  The  order,  from  longest  to  shortest, 
is :  c,  «,  bf  d.  All  four  middle  pieces  are  20  mm.  in  length.  In 
a  and  ^,  this  20  mm.  is  bounded  by  lines  of  21  and  19  mm. 
respectively. 

The  lower  part  of  the  figure  (c,  d)  shows  a  perspective  illu- 
sion ;  c  is  more  remote  than  d.  There  is  no  similar  illusion  in 
a  and  b, 

Wundt  regards  these  illusions  as  'associative,'  i.e.^  as  condi- 
tioned by  purely  psychological  (not  physiological)  motives.  In 
a  and  b  we  have  an  *  assimilative  *  association  ;  lengths  that  are 
but  slightly  different  are  taken  to  be  equal.  Hence  the  middle 
line  of  a  is  overestimated,  the  middle  portion  of  b  underestimated. 
In  ^and  dfwe  have  a  *  contrastive  *  association  :  the  middle  por- 
tion of  c  is  overestimated,  and  that  of  d  underestimated,  by  'con- 
trast '  with  the  outlying  lines.  The  illusions  of  this  class  are 
but  few  in  number ;  and  we  should,  perhaps,  rather  be  satisfied 
that  so  many  forms  of  illusion  have  been  brought  under 
physiological  rules  than  cavil  at  the  exceptions.  Nor  is  there 
anything  intrinsically  unscientific  in  the  appeal  to  purely  psy- 
chological conditions.  Nevertheless,  the  author  regards  this 
section  of  Wundt's  work  as  unsatisfactory,  and  hopes  that  it 
will  presently  be  possible  to  subsume  the  refractory  illusions  to 
the  laws  of  eye-movement  and  fixation. 

(xvi.)  A  shows  an  assimilative  'interspace'  illusion  ;  the  lines 
that  are  more  widely  separated  appear  the  longer.  B  gives  a 
contrastive  interspace  illusion. 

Experiment  (7). — (xvii.)  In  Fig.  45  (Pt.  i.)  the  height  of  A 
and  B,  and  the  length  of  the  horizontal  boundary  lines,  are 
equal.     But  B  looks  higher  than  A,  and  the  horizontal  lines  of 


§  49-   Associative  and  Mixed  lilusions  319 

A  look  longer  than  those  of  B,  We  have  as  conditions  a  con- 
stant illusion  of  extent  (the  overestimation  of  vertical  as  com- 
- --  'd  with  horizontal  distances^  and  a  variable  illusion  of  extent 
ler-Lyer  figure). 

(xviiL)  The  illusion  consists  in  the  apparent  vertical  disjunc- 
tion of  the  parts  of  the  oblique  line.  We  have  as  conditions : 
(i)  the  overestimation  of  acute  angles  (variable  illusion  of  direc- 
tion: cf,  Pt.  L,  Fig.  41);  (2)  the  overestimation  of  vertical  as 
compared  with  horizontal  distances  (constant  illusion  of  extent); 
and  (3)  the  overestimation  of  filled  space  (here  the  vertical 
lines)  as  compared  with  empty  space  (the  empty  interior  of  the 
figure :  a  variable  illusion  of  extent :  cf.  Pt.  i.,  Fig.  34,  B).  All 
three  conditions  work  in  the  same  direction. 

(xix.)  The  small  arc  seems  to  be  concentric  with  the  large  arc, 
but  to  belong  to  a  circle  of  greater  radius.  We  have  (i)  an 
overestimation  of  the  small  arc,  analogous  to  the  overestimation 
of  small  angles  (variable  illusion  of  direction).  As  the  curva- 
ture is  not  altered,  the  arc  must  belong  to  a  circle  of  greater 
radius.  (2)  By  an  'assimilative  *  illusion,  the  smaller  and  larger 
arcs  are  referred  to  the  same  centre. 

(xx.)  The  lower  trapezoid  in  A  appears  the  smaller.  The 
condition  of  the  illusion  is  the  overestimation  of  small  angles. 
Supf>ose  that  the  lines  of  fixation  eg,  ae,  bf,  dh  are  drawn.  We 
shall  then  have  at  a  and  e  acute  angles  below  the  parallels  ab, 
ef\  and  at  c  and  g  acute  angles  above  the  parallels  cd,  gh.  But 
this  means  that  ae  and  eg,  which  are  really  parallel,  appear  to 
diverge  above :  hence  the  lower  figure  must  appear  the  smaller. 

In  ^  we  have  this  same  variable  illusion  of  direction,  but  we 
have  in  addition  the  'assimilative*  illusion  of  reference  to  a 
common  centre.     The  total  illusory  effect  is  thus  increased. 

Neither  .<4  nor  Ogives  rise  to  illusion  if  the  figures  are  shifted 
from  their  direct  vertical  coincidence. 

Questions.  —  (i)  Retinal  image:  distortion  of  the  image  by 
dioptrical  defects ;  phenomena  of  irradiation.  Eye-movements : 
strabism ;  paplysis  of  eye  muscles.  Wundt,  Tauschungen, 
170  f. 

(2)  Constant  illusions  of  extent  and  direction  :  purely  physio- 
logical.    Illusions  of  reversible  perspective ;  variable  illusions  of 


320  Visual  Space  Perception 

extent  and  direction :  mixed.     Illusions  of  association :  purely 
psychological.     Wundt,  Tauschungen,  173. 

(3)  The  answer  to  this  Question  is  important  for  the  *  proxi- 
mate' understanding  of  Wundt's  theory  (p.  309  above).  See 
Tauschungen,  172;  Phys.  Psych.,  ii.,  439;  ^.  Titchener,  Out- 
line, 203. 

(4)  There  are  three :  the  requirement  of  a  determinate  posi- 
tion of  the  retinal  image  (more  exactly,  of  a  determinate  direction 
of  the  lines  of  fixation) ;  the  rule  that  the  point  first  fixated,  and 
the  point  from  which  movement  proceeds,  appear  nearer  to  the 
observing  eye ;  and  the  rule  that  the  perspective  which  corre- 
sponds to  the  usual  conditions  of  tridimensional  vision  usually 
evokes  the  eye-movements  that  accord  with  it,  and  so  is  most 
frequently  perceived.     Wundt,  Tauschungen,  171  f. 

(5)  This  question  is  intended  to  introduce  the  student  to 
Lipps'  method  of  analysis.  The  answer  should  be  worked  out 
from  the  Raumaesthetik,  271,  last  paragraph.  Lipps*  reasoning 
is,  at  best,  not  easy  to  follow.  It  is,  however,  important  that 
the  student  should  have  some  knowledge  of  the  mechanical-aes- 
thetic theory,  and  give  it  the  respect  due  to  an  acute  and  con- 
sistently worked  out  hypothesis.  The  method  of  appeal  to 
particular  figures,  with  comparison  of  explanations,  has  not  been 
found  satisfactory  by  the  author ;  Lipps'  arguments  lose  very 
considerably  by  separation  from  their  context. 

(6)  This  Question  may  be  somewhat  beyond  the  capacity  of 
the  average  student.  If  it  is  attempted,  its  answer  should  be 
worked  out  from  Wundt,  Tauschungen,  157  ff.;  Philos.  Studien, 
xiv.,  27  ff.  ;  Witasek,  Zeits.  f.  Psych.,  xix.,  81  ff.;  Lipps,  Raum- 
aesthetik, 1-69,  esp.  61  ff.  The  Question  gives  the  Instructor 
a  good  opportunity  to  emphasise,  and  by  reference  to  historical 
conditions  to  explain,  the  *  intellectualistic  '  or  '  logical '  tenden- 
cies of  popular  psychology.     See  Kiilpe,  Outlines,  189  ff. 

(7)  Fig.  49  (Pt.  i.)  shows  a  number  of  illusions  of  reversible 
perspective;  Fig.  50,  some  variable  illusions  of  extent;  Fig.  51, 
variable  illusions  of  direction  ;  Fig.  52,  illusions  that  may  be 
regarded  as  associative  ;  and  Fig.  53,  illusions  that  appear  to  be 
due  to  a  complication  of  conditions.  Many  of  these  figures  will 
be  found  in  Sanford,  Course,  212  ff. 


§  so.    Th€  MHlUrLycr  Illusion 


321 


$  50.  SzpUnationi  of  the  Miiller-Lyer  (Arrow  Hoad  and  Feather) 
niution.— (i)  Delbaufs  Theory  of '  Attraction  of  Regard:  —  Del- 
boeuf  considered  that  here,  and  in  a  number  of  other  illusion- 
figures,  the  eye  is  drawn  or  attracted  to  or  from  the  principal 
line  by  neighbouring  lines.  In  Fig.  36  A  (Pt.  i.)  the  regard  is 
attracted  towards  the  central  line  in  a,  and  away  from  it  in  ^ ;  0 
*«;  therefore  shorter,  b  longer.  Delboeuf  employed  Fig.  84  to 
ubstantiate  his  theory.  The  illusion  is  much  more  pronounced 
in  A  than  in  B ;  the  acute  angles  act  more  powerfully  than  the 
obtuse  in  drawing  the  eye  to  or  from  the  principal  line. 

Revue  sdentifique.  li.,  1893,  237-241.  Criticised  by  BrenUno,  Zeits.  f. 
Psych.,  vi.,  1-7;  Einthoven,  PflUgcr's  Arch.,  Ixxi.,  5;  Heymans,  Zeits.  f. 
Psych.,  iz.,  246  £ ;  Thi^ry,  Phil.  Stud.,  zii.,  92 ;  Wundt,  Tauschungen,  93. 


V 


A 

A 


A   • 


N 


O  • 


Fig.  84.  — Delboeat 


Fig.  85.  —  Brentano. 


( 2 )  Brentano' s  Theory  of  tne  *  Pseudoscopic  A ngle. '  —  Brentano 
reduces  the  figure  to  its  simplest  form,  Fig.  85.  There  is  noth- 
ing in  ^  to  make  the  distance  from  the  point  to  the  end  of  the 
line  seem  shorter  than  the  distance  between  the  points  in  A,  or 
than  the  distance  marked  off  in  C,  except  our  estimation  of  the 
angle  formed  by  the  imaginary  line  ab  with  the  line  be.  We 
overestimate  acute,  and  underestimate  obtuse  angles.  The  result 
of  this  tendency  is  shown  in  Fig.  86.  The  relation  between  the 
end-point  of  the  line  and  the  isolated  point  is  here  changed  by 
our  incorrect  estimation  of  the  angle,  and  the  change  of  relation. 


322  Visiuil  Space  Perception 


directly  affects  our  further  estimation  of  distance,  —  underesti- 
mation of  obtuse  angles  increasing,  and  overestimation  of  acute 
angles  lessening  the  distance. 
In  Fig.  87,  the  conditions  of 
illusion  are  multiplied,  and  the 
illusion  is  therefore  enhanced. 
In  Fig.  88  the  illusion  is  greatly 
diminished ;  in  Fig.  89,  it  is  prac- 
tically destroyed.  J  r  ^ 


>      <  > 


\ 


• 


H  CD 


Fia  86.  —  Brentano,  Figs.  87,  88,  89.  —  Brentano. 

Zeits.  f.  Psych.,  ill.,  349-358  (esp.  356-8)  ;  v.,  61-82  (esp.  77-82)  ;  vi., 
1-7.  Criticised  by  Delboeuf,  Rev.  sci.,  li.,  237  ff. ;  Heymans,  Zeits.  f.  Psych., 
ix.,  236  ff. ;  Lipps,  Zeits.  f.  Psych.,  iii.,  498-504;  Miiller-Lyer,  Zeits.  f.  Psych., 
ix.,  7  f. ;  Thi^ry,  Phil.  Stud.,  xii.,  89. 

(3)  Auerbach's  *  Physiological'  (^Indirect  Vision)  Theory.  —  In 
estimating  the  length  of  the  divided  line  ac.  Fig.  90,  the  eye  in- 


FiG.  90.  —  Auerbach. 

voluntarily  draws  lines  df,  gi,  km,  parallel  to  ac.  The  line  ac  is 
bisected  at  b  ;  but  the  line  bl  divides  the  three  parallels  unequally 
at  e,  //,  /.  This  unequal  division  of  the  surfaces  above  and  below 
ac  affects  our  estimate  of  the  divisions  of  ac  itself.  Hence  ab 
becomes  smaller  than  be. 

Zeits.  f.  Psych.,  vii.,  152-160  (esp.  153).  Criticised  by  Einthoven,  PflUger's 
Arch.,  Ixxi.,  5  ;  Heymans,  Zeits.  f.  Psych.,  ix.,  236  fF. ;  Thidry,  Phil.  Stud.,  xii., 
88  f. 


§  50.    Thi  MiUUr-Lytr  lUusum 


323 


(4)  BruHofs  *Mttm  Distcmce*  Theory,  —  Our  estimate  of  the 
comparative  length  of  ab  and  cd  in  Fig.  91  is  based  not  upon  the 


# 


Fig.  91.  —  Bronot. 

apparent  lengths  of  the  lines  themselves,  but  upon  the  distances 
between  the  *  centres  of  gravity  *  of  the  spaces  included  by  the 
terminal  circles.  We  are,  therefore,  really  comparing  the  lines 
/^,  34,  The  theory  is  substantiated  by  Figs.  92-94.  In  Fig.  94 
the  lines  are  rendered  unusually  important,  and  the  influence  of 
the  end-spaces  is  reduced  ;  in  Figs.  92  and  93  the  end-spaces  are 
emphasised. 

Rev.  sd.,  lii.,  212.    Criticised  by  Thi^ry,  Phil.  Stud.,  xii.,  88. 


FIGS.  92,  93,  94.  — BmnoC. 

(5)  MUllet'Lyet^ s  *  Confluence*  Theory. — When  two  mental 
processes  are  set  up  by  neighbouring  stimuli,  they  may  influence 
each  other  in  the  direction  of  greater  likeness  (confluence)  or  of 


324  Visual  Space  Perception 

exaggerated  difference  (contrast).  In  the  estimation  of  the 
equal  lines  of  the  figure  we  take  account  not  only  of  the  lines 
themselves,  but  also,  involuntarily,  of  the  spaces  included  by  the 
oblique  pieces.  The  line  bounded  by  obtuse  angles  is  therefore 
longer  than  that  bounded  by  acute  angles :  in  each  case,  the 
impression  is  strengthened  by  the  accompanying  impressions, 
and  strengthened  in  the  direction  of  these  latter  (confluence).  — 
The  explanation  is  not  unlike  that  of  Auerbach,  though  the 
principle  upon  which  it  rests  is  different. 

Du  Bois-Reymond's  Archiv,  1889,  S.  B.,  266  f. ;  Zeits.  f.  Psych.,  ix.,  1-16 
(esp.  4  ff.)  ;  X.,  421.  Criticised  by  Einthoven,  Pfliiger's  Arch.,  Ixxi.,  4  f . ; 
Heymans,  Zeits.  f.  Psych.,  ix.,  236  ff. ;  Liska,  Du  Bois-Reymond's  Arch.,  1890, 
326-328 ;  Thi^ry,  Phil.  Stud.,  xii.,  88 ;  Wundt,  Tauschungen,  91  ff. 

(6)  Thirty  s  *  Perspective  *  Theory.  —  The  line  that  appears 
nearer  is  seen  as  smaller,  the  line  that  appears  farther  off  is  seen 
as  longer.  If  the  central  point  of  Hering's  figure  (Ft.  i..  Fig. 
39  y4)  be  drawn  out,  in  imagination,  to  form  a  horizontal  line,  it 
will  represent  the  (apparently)  longer  Miiller-Lyer  line,  and  be 
seen  behind  the  plane  of  the  paper.  If  a  line  be  drawn  in 
Wundt's  figure  (Pt.  i..  Fig.  39  E)  between  any  corresponding 

pair  of  angles  in  the  centre  of  the 
diagram,  it  will  represent  the  (appar- 
ently) shorter  Miiller-Lyer  line,  and 
be  seen  before  the  plane  of  the  paper. 
The  illusion  of  irreversible  perspec- 
tive in  the  Miiller-Lyer  figure  is,  as 
we  said  above  (p.  314),  that  the 
shorter  line  seems  to  be  nearer  than 
the  longer.  Thiery  makes  the  differ- 
ence of  distance  the  primary  illusion. 


V 


A 


Phil.   Stud.,   xii.,   73    ff.      Criticised   by 
Wundt,  Tauschungen,  loi. 


(7)    Wundfs  *  Eye-movement '  The- 
ory.—  Every  line  of  fixation  is  trav- 
ersed   by   means   of  a  determinate 
Fig.  95.— Wundt.  movement,  or  (if  the  eye  remain  at 


{  50^    Tkt  MUUtr-Lyer  lUusion 


32$ 


rest)  contains  a  '  motive '  to  the  execution  of  such  a  determinate 
movement  Eye-movements  may  be  free,  continuous,  or  may 
be  hampered,  arrested ;  and  the  difference  is  reflected  in*  our 
perceptions  of  spatial  extent.  Lines  containing  a  motive  to 
the  continuance  of  movement  in  their  own  direction  are  over- 
estimated ;  lines  containing  a  motive  to  the  arrest  of  movement 
are  underestimated.  The  illusion  is,  therefore,  lessened  in  the 
.onger  figure  of  Fig.  95,  where  the  oblique  pieces  lie  farther  out 
of  the  direction  of  the 
vertical  than  they  do 
:i  the  shorter  figure. 

1  au>u)ungen,  100  ff. 
Criticised  by  Einthoven, 
Pfliigers  Arch.,  Ixxi.,  5; 
Heymans,  Zeits.  f.  Psych., 
ix.,  246  ff. ;  MUller-Lyer, 
Z«its.  f.  Psych^  ix.,  9. 


(8)  Eintkavin's  *  Dis- 
persion Image '  Theory. 
—  The  only  parts  of 
the  figure  clearly  seen 
are  the  parts  directly 
seen.  Fig.  96  shows 
how  the  parts  indirectly 
seen  may  be  changed 
by  dispersion. 

PflUgcr's  Arch^  hod.,  i  ff. 


#  m 


Fiu  96.  —  Einthoven. 


(9)  Ldska's  Theory  of 
*  Joining  the  Discontin- 
uous.' —  All  our  judg- 
ments are  the  resultant  of  two  sets  of  factors :  habitual  ten- 
dency and  present  circumstances.  In  this  case,  our  tendency 
is  to  join  a  discontinuous  figure,  to  malce  it  continuous,  by  the 
shortest  possible  road ;  the  figures  themselves  supply  the  cir- 
cumstances. But  the  lines  necessary  to  make  a  complete  figure 
of  the  pointed  line  are  shorter  than  those  required  to  make  a 


326  Visual  Space  Perception 

complete  figure  of  the  feathered  line ;  therefore  the  latter  ii  the 
longer. 

Du  Bois-Reymond's  Arch.,  1890,326.  Note  that  Ldska  himself  does  not 
make  the  above  definite  application  of  the  theory ;  he  merely  throws  it  out  in 
general  terms.    The  explanation  resembles  that  of  Auerbach. 

(10)  Heymans'  'Movement  Contrast'  Theory, — When  one  fix- 
ates the  end-point  of  either  of  the  vertical  lines,  the  eye  takes 
in  the  oblique  pieces  as  well.  This  perception  implies  an  idea 
of  eye-movement,  from  the  point  of  rest  to  the  end-points  of  the 
oblique  pieces.  And  this,  in  turn,  implies  a  very  strong  tendency 
to  actual  movement.  Now  in  the  case  of  the  pointed  vertical, 
the  suggested  movement  is  in  a  similar  direction  to  movement 
along  the  principal  line ;  in  the  case  of  the  feathered  vertical,  it 
is  in  a  different  direction.  Hence,  in  the  former  case,  the  sum 
of  eye-movement  is  less  than  it  is  in  the  latter:  just  as  a  fore- 
going red  weakens  a  following  red  but  strengthens  a  green.  We 
have,  accordingly,  the  underestimation  and  overestimation  of  the 
two  verticals.  Contrast  occurs  in  two  forms :  the  inward  and 
outward  directions  of  the  oblique  pieces  exert  opposite  influences 
upon  the  movement  of  regard  ;  and,  within  each  figure,  the  upper 
and  lower  oblique  pieces  have  an  opposite  effect.  The  former 
statement  needs  no  further  explanation ;  the  latter  is  explained 
as  follows.  Increase  of  the  illusion  depends  upon  the  oblique 
pieces  with  which  the  eye-movement  begins  ;  its  decrease  depends 
upon  those  with  which  the  movement  ends.  For,  if  the  obliques 
are  lengthened,  the  influence  of  the  initial  pair  is  gradually  les- 
sened, and  finally  altogether  destroyed :  this  is,  of  course,  fully 
demonstrable  only  on  the  feathered  vertical,  since  only  there  can 
the  obliques  be  increased  to  any  required  length.  The  reason  is, 
that  the  initial  obliques  exercise  their  full  power  only  when  they 
are  relatively  short,  and  so  directly  seen  ;  as  they  lengthen,  they 
are  seen  less  and  less  clearly,  and  their  superiority  (as  illusion- 
producing  factors)  over  the  final  obliques  (the  illusion -arresting 
factors)  is  presently  reduced  to  zero. 

Zeits.  f.  Psych.,  ix.,  248-252.  Criticised  by  Einthoven,  PflUger's  Arch., 
l3^->5j  Wundt,  Tauschungen,  92-94,  160-162. 

(11)  L  ipps  *  Mechanical-CBsthetic '  Theory.  —  This  explanation 


§  so.    Tk€  MUlla^Lftr  Illusum  327 

is,  unquestionably,  that  which  suffers  most  by  disjunction  from 
its  context  It  shall  be  given,  so  far  as  possible,  in  Lipps'  own 
words.  Why  do  we  overestimate  the  length  of  the  line  (r.^.,  of 
a  horizontal  line)  that  lies  between  diverging  end-pieces  ?  The 
answer  is  this.  "  The  terminal  points  of  the  line  limit  it,  and 
limit  also  the  oblique  pieces.  This  second  limiting  activity  works 
upwards  and  downwards,  in  so  far  as  the  oblique  pieces  trend 
upwards  and  downwards.  It  works  outwards,  in  the  horizontal 
direction,  in  so  far  as  the  oblique  pieces  trend  outwards.  Just 
in  so  far  as  this  is  the  case  must  the  limiting  activity  of  the 
terminal  points  towards  the  inside,  towards  the  horizontal  line 
itself,  be  cancelled  by  their  limiting  activity  outwards,  towards 
the  oblique  pieces.  To  the  same  degree,  of  course,  the  limiting 
activity  of  the  points  towards  the  oblique  pieces  is  cancelled  by 
their  activity  on  the  side  of  the  horizontal  line.  That  is  to  say  : 
the  length  of  all  these  lines  is  overestimated."  Why,  on  the 
other  hand,  do  we  underestimate  the  length  of  the  horizontal 
line  that  lies  between  converging  end-pieces }  **  The  limiting 
activity  which  the  common  terminal  point  exerts  upon  the  hori- 
zontal line,  and  the  limiting  activities,  relatively  of  the  same 
direction,  which  it  exerts  upon  the  oblique  pieces,  reinforce  one 
another."  The  illusion  is  less  than  in  the  former  case,  because 
the  tension  (produced  as  reaction  by  the  increase  of  the  limiting 
activity)  is  greater. 

Raumaesthetik,  237, 250 ;  Zeits.  f.  Psych.,  iii.,  502  f.  Criticised  by  Brentano, 
Zeits.  f.  Psych.,  v.,  77-82 ;  Einthoven,  Pfliiger's  Arch.,  Ixxi.,  5 ;  Heymans, 
Zeito.  f.  Psych.,  ix.,  243  ff. ;  Wundt,  Tauschungen,  164  (general  criticism). 

(12)  Jastrow's  'Relativity*  Theory. — Jastrow  does  not  deal 
directly  with  the  Miiller-Lyer  illusion,  but  lays  down  general 
principles  upon  which  this  and  the  cognate  illusions  may  be 
explained.  They  are  all,  he  thinks,  essentially  psychological  in 
origin,  illusions  of  judgment  and  not  of  perception.  And  they 
are  all  reducible  to  the  law  that  we  are  prone  to  judge  relatively, 
!>.,  to  modify  our  judgment  according  to  environment. 

All  angles  are  overestimated.  If  we  call  **  the  direction  of  an 
angle  the  direction  of  the  line  that  bisects  it  and  is  pointed 
toward  the  apex,  then  the  direction  of  the  sides  of  an  angle  will 


328  Vtsua/  Space  Perception 

be  deviated  toward  the  direction  of  the  angle."     When  obtuse 

and  acute  angles  are  so  placed  as  to  lead  to  opposite  deviations, 

the  former  will  outweigh  the  latter,  and 

the  illusion  will  appear  according  to  the 

I  direction  of  the  obtuse  angle.    The  smaller 

the  angle,  the  less  is  the  illusion.     And 

\  /       "just  as  the  presence  of  angles  modifies 

^  '  our  judgment  of  the  directions  of  their 

sides,  so  too,  the  angles  will  modify  the 
apparent  lengths  of  lines." 

Fig.  97.  —  Jastrow.  Amer.Journ.ofPsych.,iv.,  1891-2,381  (382,396). 

The  following  analysis  may  save  labour  in  the  use  of  the 
bibliography. 

(i)   Delboeuf  (Rev.  sci.,  li.,  237)  criticises  Brentano. 

(2)  Brentano  (Zeits.  f.  Psych.,  v.,  77-82)  criticises  Lipps ;  (vi.,  i)  criti- 
cises Delboeuf. 

(3)  Auerbach  (Zeits.  f.  Psych.,  vii.,  1894,  152)  criticises  Brentano. 

(5)  Miiller-Lyer  (Zeits.  f.  Psych.,  ix.,  6-16)  criticises  Auerbach,  Brentano, 
Delboeuf,  L^ka,  Lipps,  Wundt. 

(6)  Thi^ry  (Phil.  Stud.,  xii.,  87-94)  criticises  Auerbach,  Brentano,  Brunot, 
Delboeuf,  Miiller-Lyer. 

(7)  Wundt  criticises  Delboeuf,  Heymans,  Miiller-Lyer,  Thi^ry. 

(8)  Einthoven   criticises   (very  hastily)  Auerbach,  Brentano,  Delboeuf, 
Heymans,  Lipps,  MUller-Lyer,  Wundt 

(9)  Liska  (Du  Bois-Reymond's  Arch.,  1890,  326)  criticises  Miiller-Lyer. 

(10)  Heymans  (Zeits.  f.  Psych.,  ix.,  236-248)  criticises  Auerbach,  Brentano, 
Delboeuf,  Lipps,  MUller-Lyer,  Wundt. 

(11)  Lipps  (Zeits.  f.  Psych.,  iii.,  498)  criticises  Brentano. 

A  good  summary  of  the  views  of  Thiery,  Miiller-Lyer,  Hey- 
mans, Lipps  and  Burmester  is  given  by  V.  Henri,  in  L'Ann^e 
psychologique,  iii.,  1896,  495.  The  views  of  Heymans,  Lipps 
and  Wundt  are  summarised  ibid.y  iv.,  1897,  538. 


CHAPTER   X 

Auditory  Perception 

experiment  xxx 

§  51.  Tonal  Fusion.  — The  doctrine  of  tonal  fusion  is  very  far 
from  being  a  closed  chapter.  Indeed,  one  of  the  most  recent 
writers  on  the  subject,  E.  Buch,  denies  that  there  is  any  need 
of  the  term  'fusion'  at  all,  and  professes  to  reduce  the  phe- 
nomena of  fusion  to  the  ordinary  laws  of  association  (Philos. 
Studien,  xv.,  1900,  268 ;  cf.  M.  Meyer,  Zeits.  f.  Psych.,  xxii., 
1900,  460).  It  is  necessary,  then,  at  the  outset,  to  have  a  clear 
definition  of  the  word. 

"If  two  tones  whose  pitch-numbers  stand  in  the  ratio  i  :2 
are  sounded  together,  they  can  be  but  very  imperfectly  sep- 
arated (gesond^rt)  as  compared  with  two  tones,  given  under  the 
same  conditions,  whose  pitch-numbers  form  the  ratio  40:77" 
(Stumpf  )l  This  difficulty  of  separation  depends  upon  "  an  in- 
variable peculiarity  of  the  sensation-material,  which  persists 
when  all  other  obstacles  to  analysis  have  been  removed.*'  In 
the  one  case  the  tones  *come  apart'  in  sensation  ;  in  the  other 
they  form  a  whole  or  total  impression,  nearly  akin  to  the  im- 
pression of  the  simple  sensation.  Fusion  is,  then,  a  phenome- 
non of  sensation,  a  sinnliches  Phdnomen,  not  an  hypothesis  set 
up  to  explain  the  problems  of  tonal  mixture. 

Stumpf  defines  fusion  as  "  that  relation  of  two  sensation  con- 
tents in  which  they  form  not  a  sum  but  a  whole  "  ;  "  that  rela- 
tion of  two  sensations,  in  consequence  of  which  (in  its  higher 
stages)  the  total  impression  approaches  more  and  more  closely 
to  that  of  a  single  sensation,  and  is  analysed  with  greater  and 
greater  difficulty."  The  reader  must  be  careful  not  to  misun- 
derstand these  statements.  A  definition  is  necessarily  couched 
in  logical  terms,  and  there  is  a  temptation  to  translate  the  terms 

329 


330  Audi  to  fy  Perception 

into  psychological  processes.  But  the  fusion-relation  is  not 
something  superadded  upon  the  tone  sensations.  Two  tones, 
sounded  together,  are  given-fused,  given  in  the  relation  of 
fusion  ;  the  fusion  is  the  sound  of  the  tones  as  they  sound  to- 
gether. Nor  must  any  process-meaning  be  read  into  the  word 
•fusion.*  There  is  no  trace  of  fusing,  of  being  fused,  when  the 
tones  sound.  They  form  a  blend,  — as  we  speak  of  a  *  blend  of 
tea  * ;  and  this  blend,  the  sound-whole,  is  the  fusion. 

Stumpf  gives  two  further  cautions.  The  fusion  of  two  tones 
is  not  identical  (even  at  its  highest  degree)  with  the  origination 
of  a  third  tone.  And  we  must  be  on  our  guard  against  spatial 
metaphors.  *'  All  spatial  extension  is  either  outside  or  identical. 
But  simultaneous  tones  offer  an  instance  of  interpenetration 
{Durchdringiingy  —  See  Tonps.,  ii.,  64  f.,  127  ff . ;  Zeits.  f. 
Psych.,  XV.,  280;  xvii.,  422;  Beitr.  i.,  42:  ct.  Meyer,  Zeits.  f. 
Psych.,  xvii.,  414;  xx.,  1899,  28. 

Materials.  — The  harmonicas  can  be  bought  for  about  25^ 
each.  Each  instrument  has  twenty  reeds,  ten  of  which  speak  to 
inspiration,  and  ten  to  expiration.  It  is  the  latter  ten  only  that 
are  used  in  the  Experiment.  The  blowing-device  described  in 
the  text  may  be  improved  by  having,  instead  of  the  quills,  two 
sliders  of  sheet  tin,  fitting  over  the  top  of  the  harmonicas,  and 
carrying  a  short  piece  of  tin  tube,  over  which  the  rubber  tubing 
can  be  slipped. 

It  need  hardly  be  said  that  the  harmonicas  are  recommended 
simply  on  account  of  their  extreme  cheapness.  They  should  be 
selected  from  the  music-dealer's  stock  as  carefully  as  the  cheap 
forks  of  Exp.  V.  In  default  of  better  instruments,  they  *  work  ^ 
very  well. 

For  more  elaborate  experiments,  the  reed-clangs  of  the  har- 
monical  and  the  tones  of  tuning  forks  may  be  recommended. 
The  tests  reported  in  the  literature  have  been  carried  out  upon 
organ-pipes,  church  organ,  piano,  violin,  forks,  etc. — On  the 
use  of  clangs  and  tones,  see  Stumpf,  Zeits.  f.  Psych.,  xvii.,  1898^ 
423  ff. ;  Meyer,  ibid.,  412. 

Experiment.  —  The  method  indicated  in  the  text  is  that  to 
be  followed  with  unmusical  observers.  There  is  no  direct  esti- 
mation of  fusion  degree ;  the  scale  is  constructed  from  the  re- 


§  5i«    Tonal  Fusion  331 

suits,  by  inference,  after  a  sufficient  number  of  trials  has  been 
made  to  exclude  chance  errors.  The  25-limit  is  theoretically 
too  low ;  but  in  practice,  with  careful  observation  should  be 
adequate  to  the  purpose  of  the  experiment.  The  time  available 
for  a  single  exercise  is  so  short  that  full  series  can  hardly  be 
taken.  Even  as  it  is,  the  Instructor  will  probably  do  well  to  as- 
sign several  C>'s  (separated  from  each  other  by  cardboard  screens, 
arranged  along  the  table  at  which  they  sit)  to  a  single  E. 

The  single-note  stimuli  must  be  introduced  here  and  there 
into  the  interval-series,  in  order  to  prevent  bias  upon  the  part  of 
O.  If  one  knows  that  two  notes  are  to  be  given,  one  will  natu- 
rally tend  to  hear  two  notes  in  every  case.  The  single-note 
judgments  may  be  neglected  in  the  final  calculation,  and  the 
tests  are  not  included  in  the  300  total.  Doubtful  judgments 
may  be  counted  \  to  the  right  (*  two  note  *)  and  \  to  the  wrong 
(*one  note')  judgments.  Doubtful  judgments  with  inclination 
in  a  particular  direction  may  be  counted  (though  this  is  rough 
procedure)  |  to  the  judgments  towards  which  they  incline,  and 
\  to  those  of  the  opposite  class. 

There  are  five  principal  cautions  to  be  given  with  regard  to 
this  experiment,  (i)  The  number-differences  upon  which  the 
scale  of  fusion  degrees  is  based  must  be  considerable,  and,  if 
not  absolutely  uniform,  still  extremely  constant.  (2)  If  a  wide 
interval  give  more  correct  judgments  than  a  narrow  interval, 
the  latter  is  not  necessarily  the  better  fusion ;  the  judgments 
may  be  based  upon  distance  in  the  tonal  scale.  But  if  a  narrow 
interval  give  more  correct  judgments  than  a  wide  interval,  the 
latter  is  very  certainly  the  better  fusion.  (3)  Pleasantness  and 
unpleasantness  of  impression  must  not  be  confused  with  higher 
and  lower  degree  of  fusion.  (4)  All  the  tones  of  a  series  must 
be  sounded  with  approximately  the  same  subjective  intensity. 
(5)  Each  pair  of  tones  must  begin  and  end  at  the  same  moment 
and  in  the  same  way.  Extreme  accuracy  of  intonation  is,  for- 
tunately, a  matter  of  indifference  with  unmusical  observers. 

With  musical  observers  a  different  procedure  must  be  fol- 
lowed. Such  observers  are  able  to  pass  direct  judgment  upon 
fusion  degree.     There  are  two  chief  obstacles  to  the  analysis  of 


332  Auditory  Perception 

a  sound-complex  by  an  unmusical  ear:  lack  of  practice,  and 
fusion.  With  musical  observers,  the  first  of  these  obstacles  is 
removed.  In  their  case,  therefore,  "as  soon  as  analysis  has 
been  performed,  and  the  tones  clearly  cognised  as  two,  the  fusion 
can  be  remarked  for  itself"  (Stumpf). 

The  method  is  that  of  'paired  comparisons*  (see  Exp.  XXI.). 
Every  interval  is  compared  with  every  other  interval  as  regards 
degree  of  unitariness.  A  scale  of  degrees  will  be  obtained, 
which  tallies  in  all  essentials  with  the  scale  of  indirect  (un- 
musical) observation. 

Points  to  be  noted  are  the  following.  ( i )  The  degree  of  cer- 
tainty with  which  a  given  interval  is  adjudged  a  better  or  worse 
fusion  than  another  interval  should  be  carefully  set  down.  For 
this  direct  scale  of  fusion  degrees  depends,  not  upon  the  num- 
ber of  tests  made,  but  upon  the  conviction  of  the  trained  ob- 
server. (2)  Distance  upon  the  scale  must,  again,  be  distinguished 
from  degree  of  fusion.  (3)  The  observer  must  be  upon  his 
guard  against  the  confusion  of  pleasantness  or  unpleasantness 
of  the  impression  with  the  sensible  relation  (fusion  degree)  ob- 
taining between  its  component  sensations.  (4)  The  beginning, 
ending  and  subjective  intensity  of  the  tones  must  be  regulated  as 
before.  (5)  The  more  delicate  the  ear,  the  more  accurate  must  be 
the  intonation  of  the  intervals.  (6)  The  observer  must  abstract 
from  his  knowledge  of  the  musical  significance  and  rating  of  the 
clangs  submitted  to  him  for  analysis,  and  from  all  considerations 
of  harmony  and  inharmony,  direct  and  indirect  relationship,  etc. 

On  the  technique  of  work  with  forks,  see  Wundt,  Phys.  Psych.,  1893,  i., 
460;  R.  Schulze,  Philos.  Studien,  xiv.,  1898,  473. 

On  method  in  general,  see  Stumpf,  Tonpsychologie,  ii.,  140  if. ;  Zeits.  f. 
Psych.,  XV.,  1897,  297  ff. 

Results. — The  percentage  of  errors  (/>.,  of  judgments  of 
unity  when  two  notes  are  sounded)  with  unmusical  observers 
will  be  roughly  as  follows : 

Octave 75% 

Fifth 40  to  60  % 

Fourth        .        .         : 28  to  36  % 

Thirds  and  sixths 20  to  30  % 

Seconds  and  sevenths ca.  1 5  % 


$  $1.    Tomai  pHsicn  333 

The  tritone  will,  in  all  probability,  fall  between  the  fourth  and 
fifth  gproups,  rather  nearer  the  former  than  the  latter :  its  posi- 
tion cannot,  however,  be  predicted  as  certainly  as  can  those  of 
the  other  intervals.  The  wide  range  of  the  percentages  is  due 
(apart  from  aids  or  hindrances  to  analysis  inherent  in  the  use  of 
a  particular  instrument,  etc.)  to  the  indefiniteness  of  the  term 
'  unmusical.*  There  are  all  degrees  of  transition  between  '  musi- 
cal *  and  *  unmusical '  observers ;  and  though  the  extremes  them- 
selves are  well  marked,  they  are  certainly  not  absolute.  The 
Instructor  must,  therefore,  inform  himself  as  accurately  as  he 
can  of  the  status  of  his  observers  in  musical  regard;  and  the 
principal  data  upon  which  the  characterisations  '  altogether  un- 
musical,' 'distinctly  unmusical,'  etc.,  are  based  should  be  entered 
in  the  student's  note-book.  —  See  Stumpf,  Zeits.  f.  Psych.,  xv., 
299 ;  Tonpsychologie,  ii.,  142  ff. 

StumpTs  tests  for  unmusicalness  are  as  follows,  {a)  A  note  within  the 
compass  of  the  observer's  voice  is  struck  upon  the  piano,  and  he  is  then 
required  to  sing  it.  {b)  Two  successive  notes  are  played,  and  he  is  required 
to  say  which  is  the  higher  of  the  two.  {c)  Intervals  are  played  (high  and 
low  fusion  d^^rees  in  random  order),  and  he  b  asked  in  each  case  whether  he 
has  heard  one  note  or  two.  (</)  Two  chords  are  played,  in  fairly  quick  suc- 
cession, and  be  is  asked  which  is  the  pleasanter  or  less  pleasant  of  the  two.  — 
Tonp8ychok)gie,  ii.,  157  ff.  These  tests  may  be  supplemented  by  suitably 
prepared  questions,  regarding  the  observer's  musical  training  in  childhood, 
his  interest  in  music,  his  ability  to  recognise  and  ^  carry  *  an  air,  etc. 

On  the  scale  of  fusion  degrees,  in  direct  and  indirect  observa- 
tion, see  Stumpf,  Tonpsychologie,  ii.,  135,  142  fif. ;  Kulpe,  Out- 
lines, 286;  A.  Faist,  Zeits.  f.  Psych.,  xv.,  1897,  102  ;  A.  Meinong 
and  S.  Witasek,  ibid.,  189;  M.  Meyer,  ibid.,  xvii.,  1898,  401 ;  E. 
Buch,  Philos.  Studien,  xv.,  1900,  i,  183. 

Questions  and  Cognate  Experiments.  —  (i)  There  are 
five  or  six  degrees  of  fusion  :  five,  if  we  count  the  tritone  with 
the  group  of  thirds  and  sixths,  or  with  the  group  of  seconds  and 
sevenths;  six,  if  we  regard  the  tritone  as  a  transition  interval 
between  these  'imperfect  consonances*  and  the  'dissonances.' 
It  is  probable  that  the  latter  view  is  the  more  correct :  that  there 
is  a  '  seven-group,'  consisting  of  the  intervals  4 : 7  (natural 
seventh)  and  5  :  7  (approximate  tritone),  roughly  represented  in 


334  Auditory  Perception 

our  experiment  by  the  tritone  32  :  45,  which  lies  between  the 

group  of  thirds  and  the  group  of  seconds. 

There  is  a  greater  difference  between  the  better  than  there  is 

between  the  worse  fusions.     This  fact  is  brought  out  by  the 

diagram  (modified  from  Stumpf),  in  which  the  higher  wave- 
crests  stand  for  the  higher  degrees 
of  fusion,  and  the  base-line  gives  the 
fusion  degree  of  the  dissonances.  — 
Stumpf, Tonps.,  ii.,  135,  176 ;  Zeits.  f. 
Psych.,  XV.,  284;  Faist,  ibid.,  114. 

(2)  "  The  degree  of  fusion  is  a 
function  of  the  vibration-ratio  of  the 
component  tones. " — Stumpf, Tonps., 
ii.,   136;  Zeits.  f.   Psych.,  xv.,  287; 

Fig.  98. -The  fusion  relation  of     Kulpe,  Outlines,  286;  Faist,  Zeits. 

octave,  fifth,  fourth,  and  thirds      ^   ,^        , 

and  sixths.  f.  Psych.,  XV.,   121. 

(3)  In  general,  the  degree  of  fusion 
is  independent  of  the  tone  region.  This  law  may  be  tested  over 
the  three  octaves  of  the  harmonicas.  In  the  very  lowest  part  of 
the  scale,  where  analysis  is  difficult  or  impossible,  the  recognition 
of  fusion  degree  becomes  difficult  and  impossible.  And  in  the 
highest  part  of  the  scale,  from  tones  of  about  4000  vs.  onwards, 
the  fusion  differences  disappear.  Elsewhere  they  persist  un- 
changed.—  Stumpf,  Tonps.,  ii.,  136 ;  Kiilpe,  Outlines,  286 ;  Faist, 
Zeits.  f.  Psych.,  xv.,  122. 

(4)  Fusion  degree  is  independent  of  the  absolute  intensity  of 
the  tones.  So  long  as  these  can  be  heard  at  all,  and  so  long  as 
they  are  not  too  loud  to  overpower  the  organ,  the  degree  of 
fusion  remains  unchanged.  Stumpf  holds  the  same  opinion  with 
regard  to  the  relative  intensity  of  the  tones.  Provided  that  the 
weaker  tone  is  audible  at  all  in  the  sound-complex,  the  degree 
of  fusion  remains  unchanged.  Kiilpe,  on  the  contrary,  argues 
that  the  weaker  tone,  if  the  weakening  be  carried  far  enough, 
becomes  a  mere  attribute  or  *  colour '  of  the  stronger,  so  that  the 
total  impression  is  made  more  unitary.  The  difference  of  opinion 
seems  to  be  due  to  a  confusion,  on  Kulpe's  part,  of  *  fusion  degree ' 
and  'ease  of  analysis.'  There  can  be  no  doubt  that  variation  of 
the  relative  intensity  of  a  component  tone  will  hinder  or  facilitate 


i  $1.    Tima/  Fusum  535 

the  analysis  of  the  tonal  perception.  But  this  simply  means  that 
fusion  degree  and  relative  intensity  are  coordinate  factors  in  an- 
alysis ;  it  does  not  mean  that  alteration  of  relative  intensity  effects 
an  alteration  in  fusion  degree.  The  latter  persists,  after  analysis, 
precisely  as  it  was  before.  Stumpf  asks  the  pertinent  question  : 
*•  How  do  we  recognise  the  octave,  if  not  by  its  fusion  ?  And 
do  we  not  recognise  the  octave  when  one  of  its  tones  is  weaker 
than  the  other?"  —  Tonps.,  ii.,  136;  Zeits.  f.  Psych.,  xv.,  288; 
Kiilpe,  Outlines,  288;  Faist,  Zeits.  f.  Psych.,  xv.,  124. 

(5)  Stumpf  maintains  that  the  fusion  degrees  beyond  the 
octave  are  the  same  as  those  within  the  octave.  **The  ninths 
have  the  same  fusion  as  the  seconds,  the  tenths  as  the  thirds, 
the  double  octave  and  triple  octave  as  the  octave,  and  in  general 
wf : « •  2  '  the  same  as  m  :  /f,  where  m  <  «,  and  ;r  is  a  (small)  whole 
number."  Kiilpe  asserts,  on  the  contrary,  that  "while  the  rela- 
tive degree  of  fusion  remains  the  same  for  intervals  beyond  the 
octave  that  it  is  for  corresponding  connections  within  the  octave, 
all  the  intervals  of  the  former  kind  stand  upon  a  somewhat  lower 
level  of  fusion  than  their  less  remote  correlates.  In  other 
words,  the  double  octave  possesses  a  higher  degree  of  fusion 
than  the  twelfth,  the  twelfth  than  the  tenth,  etc.,  but  the  double 
octave  in  its  turn  fuses  less  well  than  the  octave,  the  twelfth 
than  the  fifth,  etc." 

Stumpf  replies  {a)  that  the  observer  must  not  be  misled  by 
greater  ease  of  analysis.  Distance  upon  the  scale  may  help 
analysis,  while  it  still  does  not  affect  fusion  degree.  He  asks, 
further,  {b)  how  it  is  that  we  recognise  the  double  octave,  except 
by  the  fact  that  the  two  tones  have  the  same  fusion  as  those  of 
the  octave,  and  merely  lie  a  greater  distance  apart.  Finally,  he 
urges  {c)  that  the  alleged  decrease  of  fusion  degree  must  either 
be  so  small  as  to  be  negligible  in  comparison  with  the  stages  of 
fusion  within  the  octave,  or  must  be  so  great  that  a  consonant 
interval  ultimately  passes  into  a  dissonance. 

Passing  over  certain  other  and  less  important  arguments,  we 
may  meet  these  three  as  follows,  (a)  Let  the  observer  compare 
the  intervals  of  the  fifth  and  the  twelfth,  with  analysis  in  each 
case,  so  that  he  can  direct  his  attention  upon  fusion  degree  and 
upon  it  alone.     He  will  find  that  the  twelfth-tones  come  apart 


336  Auditory  Perception 

in  perception  more  easily  than  the  fifth-tones.  (^)  The  fact 
that  we  recognise  the  double  octave  as  the  double  octave  tells 
against  Stumpf.  We  do  not  recognise  the  twelfth  as  the  fifth, 
but  as  the  twelfth  ;  we  do  not  recognise  the  ninth  as  the  second, 
but  as  the  ninth.  There  is  a  sense-difference  present,  over  and 
above  the  difference  of  tonal  distance,  (c)  The  third  argument 
has  weight  only  on  the  assumption  that  the  scale  of  fusion 
degrees  must  be  a  linear  scale.  There  is,  however,  no  reason 
why  there  should  not  be  a  second  linear  scale,  parallel  with  the 
intra-octave  scale,  the  steps  upon  which  agree  in  relative  posi- 
tion with  the  steps  within  the  octave,  but  have  their  places  in  a 
different  fusion  system. 

While,  therefore,  the  author  agrees  with  Stumpf  on  (4),  he  agrees  with 
Kulpe  on  (5).  These  judgments  are  the  outcome  of  more  or  less  systematic 
work  (direct  observation ;  Konig  forks  and  Ellis  harmonical)  repeated  every 
year  since  1892. 

Stumpf,  Tonps.,  ii.,  139;  Zeits.  f.  Psych.,  xv.,  293;  Kiilpe,  Outlines,  287; 
Faist,  Zeits.  f.  Psych.,  130. 

(6)  This  question  includes  the  question  of  the  influence  of 
clang-tint  upon  degree  of  fusion.  On  the  negative  side,  see 
Stumpf,  Tonps.,  ii.,  \i6{cf.,  however,  Beitr.,  ii.,  1898,  168);  Zeits. 
f.  Psych.,  XV.,  290;  Faist,  ibid.,  127.  On  the  positive,  Kiilpe, 
Outlines,  293;  Faist,  Zeits.  f.  Psych.,  xv.,  128;  Meyer,  ibid.y 
xvii.,  413  ff.  ;  xviii.,  1898,  274  ff.  ;  xx.,  1899,  445.  We  have  no 
alternative  but  to  suspend  judgment,  until  more  systematic  ex- 
periments have  been  made. 

(7)  The  degree  of  fusion  remains  unchanged,  although  analy- 
sis is  facilitated.  —  Stumpf,  Tonps.,  ii.,  138;  Zeits.  f.  Psych., 
xvii.,  423  ;  Kiilpe,  Outlines,  299. 

(8)  No  ;  although,  e.g.,  the  beats  which  the  actual  tones  would 
make  can  be  slowed,  quickened,  or  entirely  suppressed  in  idea- 
tion.—  Stumpf,  Tonps.,  ii.,  138;  Beitr.,  i.,  10  f. ;  Faist,  Zeits.  f. 
Psych.,  XV.,  130. 

(9)  We  have  already  had :  distance  on  the  tonal  scale,  abso- 
lute and  relative  intensity,  spatial  separation.  To  these  may  be 
added :  number  of  simultaneous  tones,  duration  of  the  clang, 
partial  tone  change  (qualitative  or  intensive) ;  attention,  practice 
and  fatigue,   expectation   and  habituation,   memory. — Stumpf, 


§  52.   Rhythm  337 

Tonps.,  ii.,  318  ff. ;  Ktiipe,  Outlines,  298  ff. ;  Sanford,  72, 
exp.  84. 

( 10)  We  must  make  a  distinction  between  analysed  and  un- 
analysed  clangs,  (a)  Analysed  clangs.  ''In  a  continuously 
sounding  compound  clang,  the  whole  appears  to  possess  the 
pitch  of  its  deepest  tone,  even  if  this  be  not  the  loudest" 
(Stumpf)L  "The  rule  holds,  in  the  author's  experience,  only  for 
stimulation  by  clangs  containing  numerous  overtones"  (Kulpe)i 
— Tonps.,  ii.,  384;  Outlines,  304;  Sanford,  72,  exp.  85.  (b) 
Unanalysed  clangs.  1.  Unequal  intensity  of  the  components. 
Here  we  find  two  illusions :  a  simple  clang  appears  a  little  lower 
than  the  compound  clang  of  equal  fundamental  pitch-number 
with  which  we  compare  it ;  and  the  absolute  pitch  of  a  simple 
clang  may  be  estimated  one  or  two  octaves  too  low.  iV.  Equal 
intensity  of  the  components.  Here  it  depends  upon  circum- 
stances whether  the  higher  or  the  lower  tone  shall  '  carry  '  the 
whole  sound-mass. — Tonps.,  ii.,  406,  410. 

The  answers  here  given  are,  of  course,  merely  schematic.  It 
must  be  left  to  the  discretion  of  the  Instructor  whether  or  not 
he  carry  the  doctrine  of  tonal  fusion  into  greater  detail ;  and  it 
must  be  left  to  his  ingenuity  to  devise  or  select  experimental 
tests  of  the  various  *  laws  *  of  fusion.  One  of  these  laws  (that 
which  deals  with  the  effect  of  mistuning  upon  degree  of  fusion : 
Stumpf,  Tonps.,  ii.,  137;  Zeits.  f.  Psych.,  xv.,  288;  Faist,  ibid.^ 
129)  has  been  left  without  mention  in  the  text;  and  many  inter- 
esting points  (the  apparent  interval  between  simultaneous  tones, 
the  movement  of  the  tonal  mass  in  a  succession  of  chords,  etc.) 
have  also  been  passed  over.  A  student  who  has  the  desire  and 
the  ability  to  gain  a  'judgment'  in  matters  of  qualitative  tone- 
psychology  cannot  begin  better  than  by  reading  through 
Stumpf  s  second  volume,  abstracting  as  he  goes,  and  working 
out  the  illustrations  (so  far  as  possible)  with  the  instruments 
and  under  the  conditions  prescribed  by  the  author. 

EXPERIMENT   XXXI 

§  52.  Rhythm.  —  The  best  introduction  to  the  psychology  of 
rhythm  is  to  be  found  in  ch.  i.  of  E.  Meumann's  Untersuchungen 
zur  Psychologic  und  Aesthetik  des  Rhythmus,  Pt.  i.,  Philos. 


338  Auditory  Perception 

Studien,  x.,  1894,  249.  The  problem  is  clearly  formulated  on 
p.  273 :  "  What  we  now  need  most  of  all  are  an  exhaustive  intro- 
spective description  of  those  data  of  the  inner  experience  which 
we  term  specifically  '  rhythmical ' ;  the  reference  of  these  expe- 
riences to  the  operation  of  mental  factors  of  general  validity ; 
and  the  determination  of  the  conditions  under  which  the  spe- 
cifically 'rhythmical'  impression  arises."  We  have,  in  other 
words,  to  describe  and  explain  the  perception  of  rhythm,  and  to 
give  it  its  place  in  our  system  of  psychology.  Although  no  one 
of  these  three  part-problems  has  as  yet  been  fully  solved,  the 
very  fact  of  their  discrimination  and  definite  formulation  marks 
a  great  step  ,in  advance.  Where  we  have  a  problem  and  a 
method,  it  becomes  merely  a  matter  of  time  until  we  also  have 
the  answer. 

On  temporal  ideas  in  general,  see  Wundt,  Outlines  of  Psych.,  trs.  1897,  pp. 
142-158.  On  the  advisability  of  beginning  work  with  uniform  sounds,  see 
Meumann,  302;  Bolton,  Amer.  Journ.  of  Psych.,  vi.,  1893,  178.  On  visual 
rhythm  and  auditory  symmetry,  see  Meumann,  279;  Philos.  Studien,  x.,  1896, 
261 ;  M.  K.  Smith,  ibid.,  xvi.,  1900,  288,  296,  299. 

Materials.  —  It  is  said  in  the  text  that  the  variation  of  audi- 
tory stimuli  is  easily  regulated.  This  is  principally  due  to  the 
fact  that  the  rise  and  fall  of  auditory  sensations  are  exceedingly 
short,  "  so  that  any  temporal  succession  of  sounds  is  reproduced 
with  almost  perfect  fidelity  in  the  corresponding  succession  of 
sensations  "  (Wundt).  On  the  other  hand,  the  instruments  which 
give  the  rhythm  stimuli,  the  variously  modified  sound  series,  must 
have  a  high  degree  of  mechanical  accuracy,  and  are  correspond- 
ingly expensive.  The  most  useful  appliance  for  investigation 
is,  probably,  Meumann's  'time-sense'  apparatus,  consisting  of 
Baltzar  kymograph,  time-disc,  set  of  contacts,  and  sound-ham- 
mers (described  and  figured  in  Philos.  Stud.,  ix.,  1894,  270  ff. ; 
xi.,  1896,  145  ff.).  This,  however,  is  not  to  be  thought  of  for  a 
drill-course.  Bolton's  apparatus  (Amer.  Journ.  of  Psych.,  vi., 
1893,  179  ff.)  might  be  simplified;  but  the  author  has  had  no 
opportunity  of  working  with  it. 

The  metronome  recommends  itself,  for  the  initial  experiment, 
both  by  its  cheapness  and  by  its  wide  range  of  rate.     Unfortu- 


§  52.   Rhytkm  339 

nately  it  is  true  in  most  cases,  as  Bolton  says,  that  **the  two  sounds 
heard  during  a  complete  swing  of  the  pendulum  of  the  metronome 
are  not  of  the  same  intensity  or  quality"  {pp.  cit.,  205  f. ;  cf.  F. 
Schumann,  Zeits.  f.  Psych.,  i.,  1890,  jy).  The  Instructor  should, 
therefore,  select  the  instrument  himself  from  the  music-dealer's 
stock,  and  not  order  at  haphazard.  There  is  a  great  difference 
between  one  metronome  and  another,  despite  the  sameness  of 
make.  An  instrument  whose  clacks  sound  approximately  equal 
on  the  music-counter  (and  such  an  one  should  be  found  among 
the  first  half  dozen  tried)  will  give  still  more  nearly  equal  ticks 
in  the  laboratory,  when  resonance  is  ruled  out.  With  a  metro- 
nome so  chosen  there  is  no  "impossibility  of  restraining  the 
grouping  by  two."  As  will  be  seen  from  the  Results,  O  may 
give  3-groups,  or  no  group  at  all.  And  where  this  happens,  we 
may  be  sure  that  the  differences  in  intensity,  quality  and  clang- 
tint,  which  we  have  intended  to  eliminate,  are  so  far  eliminated 
that  they  have  become  subliminal,  and  do  not  influence  O's  atti- 
tude to  the  sound  series. 

It  should,  perhaps,  be  said  that  the  author  has  not  been  able  to  find  a  bell- 
metronome  which  answers  the  purpose  of  this  first  experiment.  This  is  regret- 
table, as  the  bell-metronome  b  required  for  Exp.  XXV.  above. 

Preliminaries.  — The  use  of  six  rates  is  arbitrary :  more  may 
be  employed,  if  time  permits.  The  metronome  is,  in  general,  a 
very  reliable  instrument.  Nevertheless,  these  rates  should  be 
tested,  on  principle,  by  counting  the  beats  with  a  stop-watch. 

Experiment  (i).  —  The  object  of  this  experiment  is  to  bring 
out  the  fact  of  subjective  rhythmisation,  or  (as  it  is  also  termed) 
subjective  accentuation.  Most  Cs  (there  are  exceptions)  can- 
not listen  to  a  sound  series  without,  so  to  speak,  hearing  a  rhythm 
into  it.  In  some  cases  this  subjective  rhythmisation  rises  to 
the  height  of  pure  illusion ;  O  insists  that  the  sounds  differ  con- 
siderably in  objective  intensity  (Bolton,  192,  195,  2CX>,  202 ; 
Meumann,  302). 

It  is  evident  that  suggestion  to  O  must,  as  far  as  possible,  be 
avoided.  The  author  would,  therefore,  advise  that  two  students 
make  their  preparations  with  two  metronomes,  working  together, 
and  then  that  two  others,  who  know  nothing  of  the  experiment, 


340  Auditory  Perception 

be  called  upon  unawares  to  serve  as  O.  This  is  the  only  way  in 
which  the  facts  of  involuntary  (purely  subjective)  rhythm  can  be 
certainly  secured. 

Meumann  (302)  gives  as  the  conditions  of  purely  subjective 
rhythmisation :  ( i )  a  high  rapidity  of  succession  of  the  sound 
impressions  (less  than  .4  sec.  intervals) ;  (2)  absolute  equality  of 
impressions  as  regards  intensity  and  quality ;  (3)  a  fairly  long 
continuance  of  the  sound  series  ;  and  (4)  a  receptive  and  passive 
attitude  to  the  sound  series  on  the  part  of  O.  The  statement  as 
to  rapidity  of  succession  has  led  the  author  to  select  the  two 
intervals  .39  and  .3  sec.  for  the  first  experiment,  though  he  is  by 
no  means  sure  that  the  time  limit  is  valid.  It  is  true,  as  Meumann 
says,  that  Bolton,  whose  upper  and  lower  limits  are  o.  i  and  1.5  sec. 
respectively,  did  not  distinguish  with  sufficient  care  between  in- 
voluntary and  voluntary  (suggested)  rhythmisation.  Neverthe- 
less, the  author  has  found  cases  of  apparently  pure  subjective 
accentuation  with  a  time  interval  of  over  i  sec.  between  click 
and  click.^  The  nature  of  the  sounds  employed,  and  individual 
differences  of  rhythmical  disposition  (of  which  we  shall  have 
evidence  presently),  may  both  exert  an  influence.  The  second 
and  fourth  conditions  must  be  fulfilled  to  the  letter.  Any  notice- 
able irregularity  in  the  stimuli  is  disturbing  ;  and  separate  atten- 
tion to  the  sounds  as  such  will  prevent  the  formation  of  a  rhythm 
(Bolton,  207).  As  for  the  third  condition,  the  author  has  found 
45  sec.  to  be  the  most  satisfactory  time  for  the  average  O. 
Rhythmically  disposed  (9's  may  not  object  to  a  longer  series ; 
but  for  the  most  part  a  prolongation  of  the  clicks  to  70  sec,  even 
at  fairly  quick  rates  (.65  and  .39  sec.  intervals),  will  render  O 
uneasy,  and  perhaps  evoke  the  exclamation  '  This  is  horrible  ! ' 
or  *  This  is  unbearable  ! '  The  '  listening '  to  a  series  of  sounds, 
without  the  least  hint  of  what  is  to  be  listened  for,  puts  a  severe 
strain  upon  the  attention. 

Full  reports  of  30  observers  will  be  found  in  Bolton,  186  ff. 
The  following  Results  were  obtained  without  any  the  least  sug- 
gestion that  might  direct  (9's  attention  to  subjective  grouping. 

1  M.  K.  Smith  (Philos.  Studien,  xvi.,  1900,  282)  places  the  lower  limit  of  subjective 
sound-rhythmisation  at "  less  than  2  sec."  G.  Martius  asserts  {ibid.,  vi.,  189 1,  196)  that 
the  *  constraint '  towards  accentuation  ceases  at  "  less  than  0.5  sec." 


$  52.   Rkytkm 


341 


O  (I).  Slight  musical  training:  not  trained  in  introspection.  Critical  atti- 
tude to  experiment ;  some  amusement  at  the  *  nonsense '  of  listening  for  no 
reason.    Time  of  stimulus :  45  sec. 


lirrsavAL 


2 

59 


39 


GaoOTWo 
No 


Series  i 

RSMAKKt 

Beats  made  a  rat-tat.  Counted,  to  see  if  they 
were  regular.    Found  them  perfectly  regular. 

Sound  made  me  drowsy.    Attention  wandered. 

Beats  resembled  clock  ticking.  Tried  to  put 
poetr>'  to  them.     Unpleasant. 

Counted  up  to  50.     Attention  wandered. 

Noticed  that  beats  were  more  rapid.  Attention 
wandered. 

Clock  movement  again.  Quite  unpleasant  sensa- 
tion in  head. 

Sound  suggested  blacksmith's  shop. 

Clock  again.  Annoyed  by  its  rapidity  and  regu- 
larity. 


Series  2 


9 

J-43 

No  g[roup 

Attention  ^^'andered. 

10 

.65 

•• 

Suggested  clock. 

II 

•3 

•• 

Rapid  clock  ticks. 

12 

•9 

u 

Normal  ticking  of  clock ;  breaking  stone. 

»3 

1-43 

u 

Pencil  tapping  on  slate. 

14 

.65 

u 

Qock. 

'5 

•3 

a 

Clock.  Sounds  seemed  to  move  farther  off  at  end 
of  series. 

16 

1.2 

No  suggestion. 
Series  3 

17 

•39 

No  group 

Clock :  also  vague  suggestion  in  the  sounds. 

18 

•9 

2-group? 

Clock ;  head  swayed  backwards  and  forwards. 

»9 

1.2 

No  group 

Beats  came  at  regular  intervals,  and  all  alike. 

20 

•3 

2-group? 

Regular  at  first;  then  the  interval  between  the 
different  sets  of  tick-tocks  seemed  longer  than 
the  interval  between  tick  and  tock. 

21 

1.4 

No  group 

Beats  regular. 

2. 

/ 

M 

Beats  regular  at  first ;  then  grew  confusing. 

-J 

•39 

2-group? 

Beats  went  in  couples.  Interval  between  couples 
seemed  longer ;  but  by  beating  time  I  proved 
that  all  the  intervals  were  equal. 

24 

M 

No  group 

Thought  of  making  couples,  but  could  not.    Inter- 

vals  between  the  beats  were  even. 


342  Auditory  Perception 

It  is  noteworthy  that  this  O  did  not  once,  in  the  24  tests, 
notice  any  variation  of  intensity  in  the  metronome  sounds. 
The  illusion  of  rhythm,  where  it  begins  to  appear,  is  an  illu- 
sion of  time-interval,  not  of  intensity.  It  was  found  impos- 
sible to  induce  subjective  accentuation  by  suggestion.  This 
O  is  therefore  to  be  classed  with  Bolton's  Subjects  18  and 
30.  —  The  results  furnish  good  evidence  of  the  steadiness  of 
the  metronome. 

0(2).  No  musical  training;  not  trained  in  introspection.  Listened  pas- 
sively without  criticism.     Time  of  stimulus :  45  sec. 

Series  i 

Ex».     Ihtbrval     Grouping  Remarks 

1  1 .4      No  group    Counted  as  high  as  40.     Some  beats  seemed  louder 

than  others. 

2  .9  "  Counted  a  little ;  breathed  deeply  several  times ; 

beats  seemed  very  slow. 

3  .28  "  Saw  telegraph  key;   then  horses.     Heard  sound 

of  rapid  driving. 

4  1.2       2-group        At  once  began  beating  time:    one',  two.      Saw 

soldiers  marching. 

5  .65  "  Could  not  count  the  beats,  because  they  kept  say- 

ing One',  two.  The  sound  seemed  to  be  hitting 
first  on  one  side  of  the  head  and  then  on  the 
other. 

6  .39  "  Felt  confused  at  first;    sound  seemed  to  knock 

me  from  side  to  side.  Then  the  second  beat 
seemed  to  be  an  echo  of  the  first;  it  was 
broader  but  less  intense. 

7  1.2  "  Moved  head  backwards  and  forwards  in  time  ta 

beats.  Uncomfortable  twitching  in  eyes  and 
lids  until  I  beat  time  with  my  foot,  when  the 
twitching  stopped. 

8  .39  "  Whole  body  moved.     Sounds  seemed  to  say  Get' 

up,  get'  up. 

Series  2 

9  1.4      No  group     Attention  wandered.     Wanted  to  nod  my  head, 

but  thought  it  would  look  ridiculous. 
10  .65  "  Thought  of  blacksmith  and  shoemaker.     Felt  as 

if  I  must  keep  my  hands  clasped,  or  in  some 
way  I  should  go  to  pieces. 


JS2.   Jajxim  343 

IimtaTAL  Gaooram  Rsmasks 

.3      No  groap    Saw  two  small  sparks  before  my  eyes.     Eyelids 

twitched;   felt  frightened;   could  not  breathe 

wen ;  when  metronome  stopped,  tears  came. 
.9      a-group        Beau  said  Read'y,  read'y,  and  I  could  not  keep 

quiet. 
I  -4  **  Driving  nails.  Saw  house ;  nodded  head ;  counted 

One\  two. 
.65  ?  Attention  distracted  by  noise  in  room.     Head 

and  body  moved  in  time  to  beats;   but  felt 

confused. 
.3      No  group    Confused ;  head  moved,  eyes  twitched.    Thought 

of  a  railroad  train. 
1.2      2-group        Saw  soldiers  marching  through  a  street.     Then 

became  confused,  and  wished  beats  would  stop, 

1  felt  so  uncomfortable.     Soon  I  began  to  beat 

time  with  foot  and  head,  and  then  1  was  sorry 

when  beats  stopped. 

Series  3 

'7  '39    2-group        Beats  seemed  to  say  Get'  up,  get'  up.     Very 

loud.  Head  wanted  to  move;  arms  jerked. 
Felt  that  if  I  stopped  something  would  happen. 

18  .9  **  Thought  of  Hickory  dickory  dock.     Kept  time 

with  right  foot  and  head;  annoyed  because 
they  would  not  keep  the  same  time. 

19  1.3  **  Time  seemed  slow.     Saw  a  see-saw.     Confused 

till  I  counted  One',  two. 

20  .3      4-group        Counted  One',  two,  three',  four,  with  a  pause 

after  the  three'.     Had  heard  a  coach  at  a  foot- 
ball game  count  in  that  way. 
31  1^      No  group    Counted  up  to  36.     Saw  a  long  line  of  people  going 

through  a  turn-stile.    Thought  of  World's  Fair. 

22  .9      2-group        Counted  One',  two.      Lost  count  and  got  con- 

fused ;  eyes  twitched  and  I  felt  queer. 

23  '39    4-gi^'up        First  beats  sounded  like  a  giggle.     Settled  down 

into  Ba',  ba,  ba',  ba.  Saw  a  clown,  and  wanted 
to  laugh.  Thought  of  "The  Man  who 
Laughs,'"  and  seemed  to  be  following  him. 
Beats  became  disagreeable,  and  pounded  me. 
Glad  to  stop. 

24  .65    3-groap        Thought  of  an  engine.     Beats  said  One',  two. 

Found  that  I  was  beating  time  with  my  thumb, 
and  thought  how  fiinny  I  must  look.  Then 
lost  count. 


344  Auditory  Perception 

This  O,  unlike  the  former,  is  rhythmically-minded.  It  was 
found  possible,  by  indirect  suggestion,  to  induce  3-,  6-,  8-  and 
—  though  with  much  greater  difficulty  —  5-groups. 

Experiment  (3).  —  This  is  Bolton's  experiment.  Its  object  is 
twofold :  to  establish  the  normal  rhythm  of  the  various  <9*s,  and 
to  estimate  the  relative  difficulty  of  grouping  by  2,  3,  4,  5,  etc. 

The  method  is  that  of  indirect  suggestion.  If  the  **  subjects 
had  spoken  of  the  clicks  seeming  like  the  clock  ticks,  they  were 
asked  if  there  was  the  same  difference  of  intensity  or  quality  in 
the  sounds  as  was  apparent  in  the  clock  ticks.  ...  If  they  had 
said  the  sounds  were  all  alike,  they  were  asked  why  they  had 
said  sounds  and  not  sound.  Did  they  suppose  there  was  more 
than  one  sound }  .  .  .  In  some  cases  it  was  sufficient  to  ask  the 
subjects  to  count  the  clicks  as  they  heard  them,  and  then  to  ask 
how  they  counted.  .  .  .  Again  ...  a  subject  was  asked  why 
he  tapped  every  fourth  or  second  click,  and  so  his  attention  was 
called  to  a  grouping  that  was  going  on  unconsciously"  (185). 
Questions  of  this  sort  will  bring  out  the  rhythmical  preferences 
of  (9's  who  are  at  all  rhythmically-minded. 

It  is  needless,  in  view  of  Bolton's  work,  to  cite  results  in  full. 
The  following  is  the  first  series  with  suggestion  taken  from  an  O 
whose  natural  rhythm  is  the  4-group 

Exp.       ^^^ '  Grouping  Remarks 

1  1.2  4  in  2-groups  Accent  on  first  and   third.     Second  beat 

blacker  than  rest. 

2  .45         4-group  Beats  less  heavy :  visualised  walking. 

3  .31         8  in  4-groups  Inhaled   on   first   and    fifth ;    exhaled   on 

third  and  seventh. 

4  1.4  4  in  2-groups  As  i.     Breathed  in  time  to  ticks.     Moved 

head  and  right  leg. 

5  .65        8  in  2-groups  Accent  on  second  beat  of  each  2-group. 

Visualised  numbers. 

6  .28        8  in  4-groups  Accent  on  first  and  third  of  each  group.  Saw 

dust  following  a  running  horse.      First 
group  slanted  to  right,  second  to  left. 

7  -39        4-group  Hydraulic  pump  keeping  time  to  metro- 

nome.    Each  group  distinctly  separated 
from  next  following. 

8  .39        5-group  Group  came  naturally,  and  yet  was  difficult 

to  hold.     Principal  accent  on  first. 


§  52.  Rkytkm  345 

9     1 .4    4-group  Very  disagreeable ;  feeling  of  effort.  Ham- 

mer striking  anvil. 

10  .39  4-grou|>,  then  8  in  4- 

gnxips,  then  S-group  Pleasant  rate. 

11  .39  a-gnxip  Tried  to  make  3*group  and  could    not. 

Effort  made  head  ache. 

13  1.3    4-group  Head  moved.     Group  had  form  of  rhom- 

boid. 
>3       -3    4-group  Main  accent  on  first  beat,  with  deep  in- 

halation. Suggested  goblins  playing 
on  mound.  Thought  of  music  and 
dancing. 

14  .9    3-group  Third  beat  accented ;  seemed  to  turn  back, 

so  as  to  lie  between  iirst  and  second. 
Saw  blocks  with  red  stripes. 

15  .65  No  group,  then  5-group  Disagreeable;   no  group  could  be  made. 

On  direct  suggestion,  5-group  formed 
with  effort.     Still  disagreeable. 

16  1.3    4-group,  then  3-group     4-group  came   naturally.     On  direct  sug- 

gestion, changed  (with  feeling  of  jump) 
to  3-group,  with  accent  on  first. 

17  .3    4  in  3-groups,  then  3-  Disagreeable;  jockey  riding  in  circus-ring. 

group  On  direct  suggestion,  3-group  made  with 

difficulty  and  discomfort. 
iS       '39  4-gn>up,  then  5-group,  Sound  unpleasant;  pleasant  when  group- 
then  3-group  ing  began.    5-group  suggested,  and  made 

easily.      3-group  suggested;    made   by 

counting. 
19       .65  4-group,  then  3-group    Visualised  green.  3-group  suggested ;  made 

easily.     Sounds  seemed  uneven ;  formed 

figures,  polygons. 
ao       .9    4-group,  then  3-group    Visualised  glass  tubes.     3-group  made  at 

suggestion.      Accent    irregular,  and   3- 

rhythm  unpleasant. 

These  three  sets  of  Results  were  obtained  from  0*s  who  were 
either  entirely  unpractised  or  (as  in  the  last  case)  had  had  no 
more  training  in  the  introspection  of  rhythm  than  the  prelimi- 
nary experiments  afford.  With  practice,  the  rhythmical  attitude 
of  O  becomes  steadier,  and  there  are  fewer  irrelevancies  in  the 
introspections.  Nevertheless,  the  elements  of  the  perception  of 
rhythm  can  be  teased  out,  without  difficulty,  from  the  Remarks. 
''An  exhaustive  description  of  the  rhythmical  consciousness," 


346  Auditory  Perception 

writes  Meumann,  "  would  have  to  distinguish,  in  any  case,  ele- 
ments of  time,  elements  of  accentuation,  intellectual  processes 
of  an  associative  and  apperceptive  character,  emotional  facts 
[direct  effects  of  sense-feeling,  and  aesthetic  feelings :  265], 
organic  and  motor  concomitant  phenomena  "  (280).  All  these 
part  processes  can  be  traced  in  the  records. 

Question  (i). — This  Question  has  already  been  answered. 
Exps.  (1)  and  (2)  bring  out  the  fact  of  subjective  accentu- 
ation, a  grouping  "  accomplished  by  accenting  regularly  certain 
sounds  more  than  others,"  with  intervals  between  the  groups 
"  which  are  apparently  longer  than  the  interval  which  separates 
the  individual  clicks"  (Bolton).  Exp.  (3)  brings  out  the  facts  that 
normal  grouping  is,  in  the  majority  of  cases,  a  grouping  by  2  or 

4  (Bolton,  212);  that  3-groups  and  2  x  3-groups  can  be  formed 
fairly  easily,  on  suggestion ;  and  that  5-groups  are  difficult, 
whether  to  form  or  to  maintain. 

When  the  fact  of  subjective  accentuation  has  been  remarked,  the  student 
may  be  asked  to  mention  analogies  from  other  sense-departments.  Vision 
furnishes  some  striking  examples.     Rule  a  series  of  vertical  black  lines,  some 

5  mm.  apart,  on  white  paper.  Not  only  does  the  eye  '  take  them  in '  in  groups 
of  3  or  4,  but  the  white  interspace  between  group  and  group  seems  to  be  broader 
than  the  space  between  line  and  line.  Divide  up  a  square,  10  x  10  cm.,  by 
black  lines,  drawn  chess-board  fashion,  5  mm.  apart.  It  is  possible  to  single 
out  larger  and  smaller  squares,  or  other  figures,  from  the  uniform  pattern.  If 
this  is  done,  the  boundary  lines  of  the  selected  figure  seem  to  be  darker  than 
the  other  lines  of  the  chess-board.  See  J.  Henle,  Anthropol.  Vortrage,  li., 
1880,  47;  F.  Schumann,  Zeits.  f.  Psych.,  xxiii.,  1900,  7,  11. 

Does  subjective  accentuation  imply  an  intensification  of  sensation  ?  Meumann 
leaves  the  question  open :  302.  Stumpf,  admitting  that  (and  explaining  how) 
very  weak  sensations  are  actually  intensified  by  attention,  inclines  to  a  negative 
view.     Tonpsychologie,  i.,  373  ff. 

Subjective  accentuation  has  been  observed  by  many  authors.  Besides  Henle 
and  Stumpf,  we  may  mention  G.  Dietze,  Philos.  Studien,  ii.,  1885,369;  G. 
Martius,  Philos.  Studien,  vi.,  1891,  196  f. ;  J.  Angell  and  A.  H.  Pierce,  Amer. 
Journ.  of  Psych.,  iv.,  1892,  534,  539. 

It  is  to  be  noticed  that  0\  preference  for  a  given  form  of  rhythm,  in  exp. 
(3),  is  in  large  measure  independent  of  the  rate  of  succession  of  the  clicks. 
This  is  important,  in  view  of  the  ftirther  fact  that  the  most  pleasant  or  '  natural  * 
period  for  the  rhythmical  unit,  no  matter  what  number  of  terms  it  may  comprise, 
is  practically  constant  at  i  sec.  Require  O  to  tap  with  a  pencil  on  the  table 
(or  better  with  a  single-click  telegraph  key)  the  2-,  3-  and  4-group  rhythm  that 


§  52.    Rhythm  347 

it  most  *nttsfyiiig*  to  htm,  that  he  feels  to  be  'right.'  The  rate  of  Upptng 
qokkens  with  increaie  of  the  number  of  terms  in  the  rhythmical  unit,  so  that 
the  time  occupied,  say,  by  ten  units,  is  approximately  the  same  in  every  case. 
5-,  6-  and  8-groups  may  be  tried ;  but  the  experiment  is  then  complicated  by 
the  dificuhy  of  tapping  with  the  needed  rapidity.  —  Meumann,  317,  427 ;  for 
of  determination,  see  Bolton,  314,  216. 


(2)  Meumann  (303)  answers  this  question  as  follows,  (i)  We 
find  an  apparent  alternation  in  the  accent  or  weight  of  the 
impressions,  (ii)  The  periodic  alternation  of  accented  and  un- 
accented impressions  is  heard  as  an  alternation  of  intensities, 
(iii)  As  a  rule,  the  rhythmical  group  begins  with  the  term  on 
which  the  principal  accent  falls.  The  groups  are  clearly  sepa- 
rated, (iv)  This  separation  may  take  on  a  temporal  form  :  the 
terms  of  the  group  come  in  quick  succession,  while  there  is 
a  pause  between  group  and  group.  —  E  should  also  be  on 
the  watch  for  (v)  reports  of  the  apparent  lengthening  of  the 
accented  clicks,  and  (vi)  apparent  differences  of  time  interval 
within  the  more  complicated  rhythmical  units. 

Experiment  (4).  —  There  are  many  ways  of  varying  the  inten- 
sity of  the  metronome  clicks.  A  window,  closed  by  a  spring, 
may  be  let  into  the  face  of  the  box  ;  the  instrument  may  beat 
l>efore  the  opening  of  a  tube,  at  the  far  end  of  which  O  sits,  and 
the  sounds  be  interrupted  by  a  falling  screen  ;  a  stop-cock  may 
be  introduced  in  the  length  of  the  tube,  etc.  The  method  of  the 
text  is  the  simplest,  and  (in  the  author's  experience)  entirely 
satisfactory. 

For  Results,  see  Bolton,  226.  The  Instructor  must  use  his 
discretion  in  the  choice  of  O's  for  this  and  the  three  following 
experiments. 

Question  (3).  —  "The  group  must  either  begin  with  a  very 
intense  sound  or  close  with  a  very  weak  one.  The  subject 
strives  either  to  put  all  the  strong  sounds  as  near  the  beginning 
as  possible,  or  all  the  weak  ones  as  near  the  close  as  possible.  .  .  . 
The  general  principle  is  well  illustrated  in  the  last  two  forms  of 
the  5-groups  "  (Bolton). 

(4)  The  following  points  may  be  noticed,  (i)  Under  certain 
conditions,  O  hears  not  two  but  three  degrees  of  intensity.  Thus 
the  rhythm  i'  i'  i  is  heard  as  i'  \"  i ;  and  i'  i'  i'  i  as  i'  i'  i"  i. 


348  Auditory  Perception 

Bolton  explains  the  phenomenon  by  contrast  (227).  (ii)  The 
experiment  brings  out  very  clearly  the  intimate  connection 
(which  is,  indeed,  an  interchangeability,  or  vicarious  operation) 
of  the  part-factors  in  rhythm.  To  most  6>'s,  the  stronger  (or 
strongest)  sound  appears  longer  than  the  rest :  intensity =dura- 
tion.  The  strongest  sound  "spreads  itself  over"  the  rest.  Again, 
the  introduction  of  the  stronger  sound  effects  a  change  of  sub- 
jective time-interval ;  in  general  —  the  complication  of  factors  is 
too  great  to  allow  us  to  lay  down  an  exceptionless  rule  —  the 
interval  following  the  intensive  sound  is  lengthened.  Here,  then, 
intensity =temporal  disjunction.  Bolton,  228;  Meumann,  305, 
311.  These  results  pave  the  way  for  the  three  following  experi- 
ments, in  which  we  are  to  make  duration,  temporal  disjunction 
and  quality=intensity. 

Experiment  (5).  — It  is  well  that  (9  should  be  kept  in  igno- 
rance of  the  order  of  the  three  following  experiments.  Hence 
the  lack  of  details  in  the  text. 

E  is  to  play,  with  equal  intensity  and  upon  the  same  digital, 

the  series  111111  Till  |  I  I  I  »  etc.  The  rhythmical 
effect  is  unmistakable.  The  longer  sound  appears  more  intensive 
than  the  rest,  and  the  familiar  illusions  of  interval  are  aroused. 
Meumann,  61. 

If  E  distrust  his  ability  to  strike  the  key  uniformly,  the  Instructor  may  play 
for  him.  It  is  not  difficult  (but  it  is  also  not  necessary)  to  devise  a  system  of 
levers  for  striking  the  key  with  equal  force.  The  time  of  pressure  may  then 
be  regulated  by  a  '  soundless  metronome,'  —  a  useful  laboratory  appliance,  con- 
sisting simply  of  a  string  and  bob,  whose  rate  of  vibration  has  been  determined 
by  aid  of  a  stop-watch. 


Experiment  (6).  —  ^  is  to  play,  with  equal  intensity  and  upon 
the  same  digital,  the  series  ill    "'ll   I    I    •'»   11    •'ill   I    •'l» 

rrrr=ijrrrr5,  rrr=irirrr^f. etc.  xherhythmi. 

cal  effect  is,  again,  quite  clear.  In  most  cases,  the  sound  that  is 
followed  by  the  rest  appears  louder  than  the  others,  and  also 
seems  to  begin  the  rhythmical  unit.  There  are,  however,  indi- 
vidual differences  in  the  manner  of  grouping. 


{  $2.    Rkytkm 


349 


The  experiment  may  alio  be  performed  with  the  boxed  metronome  O  siu 
at  tiich  a  distance  from  the  box  that  closure  of  the  lid  entirely  destro)'s  the 
soand  of  the  dick.  K  starts  the  metronome  at  one  of  the  more  rapid  rates, 
and  cuts  out  every  fourth,  fifth,  etc.,  beat  by  dropping  the  lid.  The  results  in 
this  case  are  modified  by  the  length  and  invariability  of  the  pause. 

Experiment  (7> — E  plays,  in  regular  alternation  and  with 
equal  intensity,  the  notes  f*-<-V  The  change  of  quality  will 
mean,  for  most  6>*s,  a  change  of  accent,  i.r.,  a  rhythm.  E  may 
then  go  on  to  play  c^-d^-e^ ;  then  ^*-</W*-/^  etc.,  etc. 


FiG.  99.  —  Rhythm  spparstus.  The  belt  runs  to  a  Piilsbary  speed  reducer, 
from  which  it  is  carried  to  the  motor  (not  shown  in  the  Fig.).  — The  speed 
reducer  is  sold  by  the  Michigan  App.  Co.  for  1 12. 


The  author  must  confess  his  fiulure^  after  many  attempts,  to  devise  a  cheap 
apparatus  that  shall  satisfy  the  requirements  of  Exps.  5-7.  Sanford  has  sug- 
gested an  arrangement  for  varying  the  duration  and  intensity  of  tonal  stimuli, 
which  is  figured  by  Bolton,  229.  It  is  an  adaptation  of  a  beat  instrument 
devised  by  A.  M.  Mayer  (Amer.  Joum.  of  Science,  Ser.  3,  viii.,  1874,  241 ; 
xlviL,  1894,  5),  and  consists  of  an  electrically  driven  tuning-fork  (say,  of  250 

.),  vibrating  over  the  mouth  of  the  appropriate  Helmholtz  or  Kcenig  reso- 
nator. Within  the  space  (not  more  than  i  cm.)  between  fork  and  resonator 
travels  the  margin  of  a  heavy  junk-board  disc,  50  cm.  in  diameter.  The  disc 
revolves  once  in  the  i  sec  A  rubber  tube,  ending  in  a  two-way  ear-tul)e 
(phonograph  tube),  nuy  be  led  off  from  the  farther  end  of  the  resonator. 


3 so  Auditory  Perception 

It  is  clear  that,  if  the  margin  of  the  disc  is  continuous,  O  will  hear  no  sound 
from  the  fork.  If  portions  of  the  margin  are  cut  away,  to  a  sufficient  depth  to 
expose  the  prongs  of  the  fork,  there  will  be  an  alternation  of  sounds  and  silences. 
With  cuts  of  an  equal  number  of  degrees,  equally  spaced,  we  shall  get  a  series 
of  sounds  alike  in  pitch,  duration,  intensity  and  time-interval.  By  varying  the 
length  of  cut  and  of  interspace,  we  can  vary  the  duration  and  time-interval  of 
the  tones.  Further,  by  cutting  the  margin  only  to  such  a  depth  as  will  expose 
a  single  prong  of  the  fork,  we  obtain  a  sound  of  greater  intensity  than  the  rest. 
Hence,  if  the  revolution  of  the  disc  is  constant,  we  have  the  three  variables 
intensity,  duration  and  interval  under  good  control. 

In  Sanford's  form  of  the  apparatus,  the  disc  stands  vertically  and  is  turned 
by  hand.  Owing  to  the  weight  of  the  junk-board,  and  the  extreme  irregularity 
of  form  of  certain  discs,  it  is  better  to  let  the  disc  rotate  in  the  horizontal 
plane.  And  it  is  (in  the  author's  experience)  essential  that  the  turning  be 
done  by  some  constant  source  of  power  {c.j^.y  the  motor  of  the  Edison  phono- 
graph, Class  M).  The  diagram  represents  this  modified  arrangement:  the 
belt  runs  from  the  disc-support  to  a  Pillsbury  speed  reducer  (transmitter),  by 
which  it  is  connected  with  the  motor. 

The  following  discs  are  recommended  by  Bolton,  and  will  be 
found  useful  for  preliminary  tests. 

(i)  2  notches  of  150°  each  ;  one  accented.  Pauses  30°.  Measure:  Z.  __ 
or  _  j1. 

(2)  I  notch  of  200°,  one  of  100°.     Pauses  30".     Measure :   \j  or  ^ . 

(3)  As  (2),  except  that  the  200°  notch  is  accented.     Measure '.    ^kj  or 

(4)  3  notches  of  100°.     Pauses  20°. 

(5)  3  notches  of  80°.     Pauses  40''. 

(6)  3  notches   of   100°,  one  accented.     Pauses   20°.     Measure:  ^ , 

__  ^  _  or /_. 

(7)  I  notch  120°;  2  notches 60°.    Pauses  40°.    Measure:  \j  \ji  \j \j 

or  ,^  x^  _. 

(8)  As  (7),  except  that  the  120°  notch  is  accented.  Measure:  Z.\j  kj, 
\j  JL.  \j  or  \^  \j  _/_. 

(9)  4  notches  of  60° ;  one  accented.  Pauses  30°.  Measure:  6  w  v^  w>  etc 

The  discs  may  be  taken  in  order,  ( i )  to  (9).  O  is  to  listen,  in 
each  instance,  until  such  time  as  a  definite  subjective  rhythm  has 
taken  shape :  the  period  varies  from  20  to  80  sec.  The  follow- 
ing are  the  rhythms  preferred  by  two  (9's :  the  results  are  aver- 
aged from  7  series  of  tests. 


§  sa.  RAj^tAm  351 

Dltc(i)  ^vy;  jiL\j'    Bolton:  ^^. 

•*  (a)  v/Z.;  ^— .    Bolton:  v^^otv^^. 

**  (3)  w  ^ ;  w  «.     Bolton :  s^  ^. 

•*  (4)  lo-gTOup;  ^  v/ ^-     Bolton :  4-group  or  3-group. 

**  (5)  lo-^proup ;  ^  v^  vy-     Bolton:^ 

"  (6)  v^  v/  ^  or  •.  ^  v^  ;  jl  v^  v^. 

**  (7)  xy^/ Jl;  vy  wZ.     Bolton:  v^  v^  _. 

"  (8)  w  v^  Z ;  yj  \j  ^'     Bolton :  v^  v^  ^. 

**  (9)  il  w  wv^;   ^^  v^  v^  v^. 

We  notice  here  {a)  the  fact  of  subjective  accentuation  :  discs 
(4)  and  (5).  The  lo-group  was  formed  by  counting  (at  first  un- 
noticed by  O);  it  consisted  of  5  2-groups.  {d)  The  accented 
term  imposes  a  rhythm  by  twos,  threes,  fours,  etc.  (c)  The 
longer  sound  imposes  a  similar  rhythm.  Other  results  are  :  (</) 
a  temporal  displacement,  due  to  the  accented  or  to  the  longer 
term ;  (t)  a  subjective  increase  in  the  duration  of  the  accented 
term ;  (/)  illusions  of  pitch,  the  louder  sound  appearing  the 
higher;  (^)  the  introduction  of  weaker  secondary  accents  in  the 
4.groups. 

This  apparatus,  given  the  power  supply,  is  easily  adjusted,  and 
the  discs  are  capable  of  wide  variation. 

Question  (5). — The  experiments  demonstrate  that  the  vari- 
ous part-conditions  of  rhythm  may  function  vicariously  one  for 
another ;  that  they  are,  in  reality,  coordinate  and  independent. 
We  have  as  yet  no  psychological  theory  of  this  interchange- 
ability.  See  Meumann,  Philos.  Studien,  ix.,  1894,  305  f.  ;  x., 
1894.  305. 

Related  Experiments.  —  We  may  mention  here  certain  tem- 
poral illusions  which  stand  in  a  close  relation  to  rhythmisation. 

( 1 )  Let  the  metronome  beat,  at  a  given  rate,  first  for  two  or 
three  clicks  only,  and  then  for  a  longer  time.  Note  that  the 
series  seems  to  run  much  more  quickly  than  the  separate  ticks. 

Try  the  experiment  with  various  rates  of  beating. 

(2)  Let  the  metronome  beat,  first  slowly  and  then  quickly,  for 
20  ticks.     Note  that  the  quicker  series  appears  the  louder. 

Repeat  the  experiment  with  the  reverse  order  of  stimulation, 
and  with  different  rates  of  beating. 


352  Auditory  Perception 

(3)  Place  the  metronome  in  its  box,  and  close  the  lid.  When 
the  ticks  have  sounded  for  some  little  time,  raise  the  lid  for  a 
single  beat ;  then  close  it,  and  let  the  muffled  ticks  continue. 
Note  the  shift  of  time-interval  produced  by  the  more  intensive 
beat. 

Try  the  experiment  with  various  rates  of  beating. 

(4)  Place  the  metronome  in  its  box,  and  close  the  lid.  When 
20  ticks  have  sounded,  raise  the  lid  for  another  20  ticks.  Note 
that  the  louder  series  appears  the  quicker. 

Repeat  the  experiment  with  the  reverse  order  of  stimulation, 
and  with  different  rates  of  beating. 

See  Meumann,  Philos.  Studien,  ix.,  1894,  274  ff. ;  x.,  1894,  311. 

To  these  may  be  added  the  following  experiment,  which  con- 
firms the  statement  that  there  is  a  natural  tendency  to  place  the 
accented  beat  at  the  beginning  of  the  rhythmical  unit  {cf.  Ques- 
tion 3  above). 

(5)  Place  the  metronome  in  its  box,  and  sound  the  rhythm 
1-2-3'  or  i-2'-3.  Note  that,  in  a  little  while,  the  former 
rhythm  changes  subjectively  to  3'-i-2,  and  the  latter  to  2^-3-1. 

Require  O  to  tap,  on  a  single-click  telegraph  key,  the  rhythm 
1-2-3'.  Note  that,  if  the  tapping  is  continued  long  enough,  the 
rhythm  invariably  changes  to  3'- 1-2. 

See  Meumann,  Philos.  Studien,  x.,  286;  Bolton,  222,  231. — 
For  other  experiments,  see  K.  Ebhardt,  Zeits.  f.  Psych.,  xviii., 
1898,  99. 

Question  (6).  —  If  the  question  is  not  understood  by  the  stu- 
dents, it  may  be  put  in  this  way :  Is  it  right  to  call  rhythm  a 
perception  }  Might  it  be  classified  elsewhere  in  a  psychological 
system  }     What  are  the  grounds  on  which  you  make  your  choice  "i 

According  to  Meumann,  "  the  specifically  rhythmical  consists 
essentially  in  intellectual  acts,  to  which  occasion  is  given  (under 
certain  conditions)  by  a  rapid  succession  of  determinate  sensa- 
tions." That  the  intellectual  processes  "are  the  priiis  in  the 
total  rhythmical  perception"  is  shown  by  such  facts  as  the  fol- 
lowing. 

(i)  Subjective  rhythmisation  is  always  introduced  by  apparent  periodic 
alternations  of  intensity,  which  effect  a  subordination  of  weaker  to  stronger 
and  a  coordination  of  the  stronger  impressions ;  and  by  an  innerliches  Zu- 


§  52.    Rhythm  353 

sammumfasstn  of  weaker  and  stronger,  etc.  ^^ ;  \  ur^e  intellectual  processes 
are  independent  of  afiiective  change,  and  are  compatible  with  a  state  of  indif- 
ference. (3)  The  greatest  energy  of  *  internal  grouping '  runs  parallel  with  a 
very  slight  feeling-eifect  (slow  rhythms).  (4)  The  measure  in  subjective 
rhythmUation  nuy  be  altered  by  simple  ideation  of  a  different  measure.  — 
Fhilos.  Studien,  x.,  273  f.,  384. 

U  then  remains  to  explain  the  motor  phenomena,  feeling 
effects  and  orjifanic  changes  which  accompany  the  perception 
of  rhythr 

M.  K.  Smiifi  U'hilos.  Studien,  xvi.,  1900,  291  f.),  at  the  conclu- 
Mun  of  a  later  investigation  carried  out  in  Meumann's  laboratory, 
writes  as  follows. 

**  Rh}'thm  is,  according  to  Wundt,  a  progressive  emotion  {Affectverlau/^y 
m  which  there  is  a  regular  alternation  of  expectation  and  satisfaction.  The 
author  is  inclined,  from  her  experience,  to  say  that  Wundt  has  here  given,  in 
a  few  words,  the  best  explanation  of  the  psychological  nature  {IVgsen)  of 
rhythm  that  we  yet  have.  .  .  .  Rhythm  may  be  designated  an  emotion, 
whose  motor  (and,  in  part,  whose  vasomotor)  expressions  and  discharges 
cannot  take  place  with  entire  freedom,  as  in  the  ordinary  progressive  emotion, 
but  whose  expressive  movements  are  regulated,  temporally  and  intensively, 
by  a  determinate  schema.  Rhythm  is  (so  Meumann  modifies  Wundt's  view) 
an  emotion,  which  discharges  itself  in  ordered  movements."  This  order 
extends  to  the  movement  pauses,  to  the  time  of  initiation  of  movement,  to 
*he  time  occupied  by  the  movement,  to  the  gradation  of  intensities  of  impulse, 

the  course  of  acts  (pulses)  of  attention  and  probably  to  vasomotor  pro> 
cesses.  ^  The  psychological  condition  of  rhythm  at  large  is  the  rapid  resolu- 
tion of  expecution." 

It  is  evident  that  there  is,  here,  a  change  of  view  on  Meumann's 
part.  The  matter  is  interesting,  and  systematically  important.^ 
^n  order  to  make  a  decision,  the  student  will  be  obliged  to  form 
..  very  clear  and  precise  idea  of  what  is  meant  by  '  perception ' 
and  'emotion.'  If  he  becomes  impressed  by  the  fluidity  of  the 
processes  covered  by  these  and  similar  functional  terms,  so  much 
the  better. 

As  the  author  has  worked  out  the  rhythm  experiment,  emphasis  is  laid 
ither  on  the  perceptive  than  on  the  emotive  constituents  of  the  rhythmical 

>  Staxnpf  remarks  (Tonpcychologie,  i.,  135)  :  **  Judgments  of  time  and  of  intensity 
are  connected  in  the  apprehension  of  rhythm :  but  we  shall  best  treat  of  that  in  the 
coarse  of  our  doctrine  of  feeling." 

2A 


354  Auditory  Perception 

consciousness.  The  Instructor  should  point  out  this  £eict,  and  draw  the 
students'  attention  to  the  affective  elements  in  the  introspective  records.  Cf. 
the  answer  to  the  following  Question. 

Question  (7). — In  the  foregoing  experiments,  we  have  varied 
the  sense-material  of  rhythm :  we  have  had  an  uniform  sound 
series,  followed  by  series  with  intensive,  temporal  (duration  and 
interval)  and  qualitative  changes.  It  remains  only,  under  this 
head,  to  vary  the  filling  of  the  intervals  ;  to  compare  the  rhythm 
of  *  empty  *  intervals  with  that  of  intervals,  marked  off  by  sounds, 
and  filled  with  other  sounds,  with  sights,  etc. 

We  have  then  to  investigate  the  organic  changes  that  accom- 
pany the  rhythmical  perception.  Breathing  deserves  especial 
attention.  Meumann  has  proved  that  respiration  adapts  itself 
to  rhythmisation  :  a  change  in  subjective  accentuation  is  fol- 
lowed by  a  change  in  breathing  (270,  272).  Cf.  Mentz,  Leumann, 
Dogiel,  Dutczinsky,  as  cited  by  Meumann  ;  Bolton,  202 ;  and 
references  in  the  introspective  reports  quoted  above. 

We  have,  thirdly,  to  study  the  associative  and  interpretative 
ideas  that  accompany  the  rhythmical  perception  :  Meumann,  265  ; 
Bolton,  184  ff. 

Fourthly,  we  must  examine  the  affective  side  of  the  rhythm 
consciousness.  We  must  note,  and  seek  to  analyse,  (i)  the  feel- 
ings interwoven  with  the  sense-material  as  such  :  feelings  of 
stimulation,  of  expectancy,  of  confusion,  of  painful  slowness,  of 
simple  agreeableness  or  disagreeableness,  of  unrest  and  uneasi- 
ness, of  effort  and  discomfort,  of  annoyance,  of  drowsiness ;  (2) 
the  emotive  forms  accompanying  the  perception  :  satisfaction, 
pleasant  animation,  excitement,  gravity  or  'staidness,'  melan- 
choly, cheerfulness,  dread,  torment ;  and  (3)  the  aesthetic  senti- 
ments, of  completeness,  rightness,  'being  rounded-up,'  *  restful 
evenness,'  intrusion,  ease.  —  Meumann,  264  ff. ;  Bolton's  intro- 
spections, 186  ff. ;  ^  the  series  quoted  above. 

Finally,  we  must  observe  and  classify  the  motor  expressions  of 
the  rhythm-feeling,  or  the  motor  concomitants  of  the  rhythmical 
perception.  It  may  be  noted  here  that,  according  to  Smith, 
"there  is  a  constraint  towards  motor  rhythmisation  of  continued 
movements,  just  as  there  is  towards  the  subjective  rhythmisation 
of  sound  impressions  "  {loc.  cit.y  282).     This  remark  leads  us  to  the 


{  $2,  Rkytkm  355 

l^neral  question  of  tactual  rhythm,  which  requires  a  programme 
of  its  own. 

Question  (8).  —  Meuraann  (306  ff.)  gives  5  points  of  differ- 
ence, (i)  Besides  grouping  in  terms  of  time  and  intensity,  we 
have  a  grouping  dependent  on  the  inner  connection  of  the  tones, 
/.r.,  phrasing.  (2)  The  tones  within  the  motif  have  varying 
values.  Some  dominate,  expressing  the  culmination  of  the  musi- 
cal thought ;  some  furnish  a  preparation  for  this  thought ;  in 
others  it  works  itself  out.  (3)  The  tonal  variation  gives  gpreater 
space  and  freedom  to  subjective  rhythmisation.  (4)  Tones  may 
vary  in  duration,  as  simple  sound  impressions  cannot :  cf.  the 
hold.    (5)  The  higher  intellectual  processes  are  enhanced. 

Question  (9). — ^The  separate  objects  are  successively  appre- 
hended :  each  in  turn  affords  a  fi.\ation-point  for  the  eye  and  a 
point  of  rest  for  the  attention.  The  rhythm  is  tactual  or  *  motor/ 
et  up  by  the  alternation  of  rest  and  movement ;  and  the  muscles 
involved  are  those  which  subserve  eye-movement  and  those  which 
ire  normally  concerned  in  the  'expression*  of  visual  attention. — 
Meumann,  261  f . ;  Smith,  300. 

This  answer  is  obvious.  The  Question  is  introduced  in  order  that  the  In- 
structor may,  if  he  wishes,  have  a  point  upon  which  to  hang  a  discussion  of 
the  relation  of  attention  to  rhythmisation.  Wundt  (the  first  to  propound  a 
psychological  theory  of  rhythm),  Meumann,  Bolton  and  Smith  have  all  a  good 
deal  to  say  upon  this  topic. 

Question  (10). —  See  Wundt,  Phys.  Psych.,  ii.,  84  ff.;  Meu- 
mann, 285  f. 

Question  (11).  —  References  (and  criticism)  in  Meumann, 
252  ff.  Stumpf  (Ton psychologic,  i.,  340)  remarks  that  "our 
sense  of  time  and  rhythm  appears  to  have  developed,  for  the 
most  part,  in  walking,"  and  quotes  Wundt  (Phys.  Psych.,  2d  ed., 
1880,  ii.,  286)  to  the  effect  that  the  time-period  which  is  most  accu- 
rately reproducible  in  idea  is  practically  identical  with  the  time 
required  for  a  movement  of  the  leg  in  rapid  walking.  Wundt, 
however,  gives  up  the  fact,  and  the  theory  based  upon  it,  in  his 
later  editions  {cf.  ii.,  1880,  287  f. ;  ii.,  1887,  354;  ii.,  1893,  416), 
though  he  still  regards  bodily  movement  as  the  ultimate  source 
of  the  rhythmical  impression  (ii.,  1893,  91  ;  cf  84).  Cf  James, 
Psych.,  L,  560,  634. 


356  Auditory  Perception 

Literature.  —  W.  Wundt,  Phys.  Psych.,  ii.,  1893,  83  ff.,  289; 
Vorlesungen  iiber  Menschen-  unci  Thierseele,  1897,  433  (trs. 
376  f.);  E.  Meumann,  Philos.  Studien,  x.,  1894,  249,  393  ;  T.  L. 
Bolton,  Amer.  Journ.  of  Psych.,  vi.,  1893,  145,  310 ;  M.  K.  Smith, 
Philos.  Studien,  xvi.,  1900,  71,  197;  M.  Ettlinger,  Zeits.  f.  Psych., 
xxii.,  19CX),  161  (a  paper  to  be  read  in  connection  with  Lipps* 
theory  of  the  geometrical  optical  illusions). 

EXPERIMENT   XXXH 

§  53.  The  Localisation  of  Sounds.  —  Experiments  upon  localisa- 
tion, in  all  sense-departments,  tend  to  take  on  a  purely  quantita- 
tive form.  The  records  then  consist  of  tables  of  figures,  showing 
the  accuracy  with  which  the  position  of  the  stimulus  has  been 
'judged'  or  *  estimated,'  without  any  attempted  analysis  of  the 
process  or  mechanism  of  judgment  itself.  Sometimes  there  is 
appended  to  the  report  a  'theory'  of  localisation  at  large,  a 
general  statement  of  the  physiological  conditions  under  which 
a  judgment  of  distance  and  direction  is  possible. 

This  tendency  towards  the  substitution  of  columns  of  figures 
for  analytic  work  must  not,  however,  be  too  severely  blamed. 
On  the  one  hand,  it  is  characteristic  of  a  young  science.  The 
goal  of  science  is  quantitative  formulation  ;  and  it  is  as  inevitable 
that  the  pioneers  of  a  new  science  exaggerate  the  exactness  and 
finality  of  their  results  as  it  is  that  the  trend  of  enquiry  shall 
presently  follow  the  opposite  direction,  of  a  precise  qualitative 
analysis.  The  earlier  workers  upon  localisation,  the  time  sense, 
the  various  forms  of  reaction,  the  fluctuations  of  attention,  etc., 
etc.,  set  out  to  get  figures  and  formulae  ;  and,  when  they  had  got 
them,  naturally  regarded  their  task  as  completed.  On  the  other 
hand,  this  *  scientific  *  attitude  to  psychophysical  problems  was 
encouraged,  so  to  speak,  by  the  problems  themselves.  The 
task  of  introspection,  in  the  cases  cited  and  in  many  others  like 
them,  is  immensely  difficult :  we  have  already  said  something  of 
the  difficulty  in  §  45.  But,  if  there  is  no  obvious  material  upon 
which  introspection  is  to  work,  it  is,  again,  natural  that  intro- 
spection shall  be  neglected.  There  is  no  lack  of  zeal  or  patience 
on  the  part  of  the  investigator :  it  is  simply  that,  at  the  stage 


§  53-    Localisation  of  Sounds  3S7 

of  the  science  which  we  are  now  considering,  the  problem  does 
not  present  itself  as  an  introspective  problem. 

Let  us  take  the  instance  of  localisation  of  sound.  If  we  look 
at  the  problem  abstractly,  there  seem  to  be  three  possibilities  of 
solution.  Our  apprehension  of  the  locality  of  sounds  may  be 
immediate :  there  may  be  a  special  organ,  or  specific  coordina- 
tion of  organs,  for  judgments  of  up  and  down,  left  and  right, 
before  and  behind.  In  this  case,  all  that  we  have  to  do  is  to 
measure  the  accuracy  of  localisation  in  the  different  dimensions 
of  objective  space,  and  then  search  the  physical  organism  for 
our  organ.  Preyer  and  Miinsterberg  find  such  an  organ  in  the 
semicircular  canals  of  the  internal  ear.  According  to  Preyer, 
the  ampullae  of  the  canals  give  us  an  immediate  perception  of 
the  direction  of  sound  ;  according  to  Miinsterberg,  we  derive 
this  perception,  with  equal  immediacy,  from  the  *  muscle '  sensa- 
tions attending  movements  of  the  head,  which  are  reflexly 
released  by  stimulation  of  the  ampullar  apparatus.  Secondly, 
however,  our  apprehension  of  the  locality  of  the  source  of  sound 
may  be  mediate  or  indirect.  And  the  criteria  by  which  we 
make  our  judgment  of  locality  may,  again,  be  either  homoge- 
neous or  heterogeneous.  The  judgment  may  depend,  e.g.^  upon 
the  relative  intensity  of  the  sound  as  heard  by  the  two  ears ;  a 
sound  which  is  very  loud  to  the  right  ear  and  comparatively 
weak  to  the  left  must  lie  towards  the  right  of  the  head  and  body. 
Here  we  are  perceiving  direction  of  sound  in  terms  of  intensity 
of  sound  :  the  criterion  is  homogeneous.  But  the  judgment  may 
also  depend  upon  tactual  perception.  "  Since  the  various  parts 
of  the  shell  of  the  ear  possess  a  delicate  sensitivity  to  pressure, 
a  sensitivity  which  is  enhanced  anteriorly  by  fine  hairs,  the 
tactual  sensations  of  the  two  pinnae  must  (especially  in  the  case 
of  intensive  sound  impressions)  be  differently  distributed  accord- 
ing to  the  direction  of  sound  "  ( Wundt).  It  is  also  possible  that 
specific  sensations  are  set  up  by  the  movement  of  the  tympanic 
membrane,  and  by  the  contraction  of  the  tensor  tympani.  Or  we 
may  have  recourse  to  criteria  of  a  still  more  remote  kind.  The 
spatial  position  of  the  source  of  sound  may  be  visualised,  as 
soon  as  the  sound  is  heard ;  or  a  reflex  movement  of  the  eye- 
balls (or  impulse  to  such  movement)  towards  the  source  of  sound 


358  Auditory  Perception 

may  follow  the  auditory  sensation.  We  should  then  be  in 
presence  of  one  of  those  mental  short-cuts  of  which  we  have 
spoken  above  (p.  129  of  the  text).  In  all  these  instances,  the 
criterion  is  heterogeneous. 

There  seems  to  be  no  doubt,  in  the  present  status  of  the 
problem,  that  localisation  is  mediate,  and  not  immediate.  The 
localisation  experiment  (here  as  in  the  case  of  touch)  thus 
becomes  a  qualitative  experiment.  For  the  remoter  secondary. 
criteria  we  may  appeal  to  introspection,  with  good  prospect  of  a 
successful  analysis.  Many  judgments  of  direction  and  (so  far  as 
we  can  tell)  all  judgments  of  distance  are  referable  to  'associa- 
tion,* and  the  unravelling  of  the  associations  is  not  a  very  diffi- 
cult task.  On  the  other  hand,  introspection  finds  it  as  hard  to 
deal  with  the  homogeneous  and  the  more  direct  heterogeneous 
criteria  as  it  does  to  deal  with  the  local  signs  of  touch  and  sight. 
We  must,  therefore,  try  to  assist  it  in  every  possible  way  by 
variation  of  our  experiments.  At  the  best,  however,  the  intro- 
spective harvest  will  be  scanty.  The  value  of  the  experiment 
lies,  then,  quite  as  much  in  what  may  be  called  the  'qualitative 
attitude '  of  the  student  as  in  the  positive  introspections  obtained. 

It  may  be  taken  as  a  general  rule  of  work  in  this  and  similar 
experiments  that  the  quantitative  procedure  is  incompatible  with 
the  fullest  and  most  reliable  introspection.  When  O  is  required 
to  localise  the  source  of  sound,  he  naturally  gives  his  complete 
attention  to  that  problem.  If  he  is  asked,  subsequently,  to 
describe  his  method  of  localisation,  to  inventory  the  contents 
of  the  localising  consciousness,  he  finds  that  method  and  mate- 
rial have,  in  large  measure,  escaped  his  notice,  and  that  what 
he  noticed  has,  in  large  measure,  been  forgotten.  It  is  there- 
fore essential  that  the  mixed  (quantitative  and  qualitative)  series 
be  supplemented  by  purely  qualitative  experiments,  in  which  O 
is  asked,  not  where  he  localises  the  sound  impression,  but  how 
he  would  localise  it  if  he  were  called  upon  to  do  so. 

Materials. — There  are  several  forms  of  the  sound  cage. 
All  are  somewhat  bulky,  and  the  cheapest  can  hardly  be  made 
for  less  than  $15.  It  may,  therefore,  be  worth  while  to  indicate 
a  method  by  which  the  equator  of  the  sound-sphere  may  be 
accurately  explored  with  very  simple  apparatus. 


$  53*   Locaiisatum  of  Sounds  3S9 

E  draws  upon  the  floor  a  chalk  circle  of  i  m.  diameter.  The 
centre  is  clearly  marked,  and  the  circumference  divided  into 
5^  units.  (X^  chair  is  to  be  placed  as  nearly  as  may  be  at  the 
centre  of  the  circle;  i.e.,  in  such  a  position  that,  when  O  is 
comfortably  seated,  a  vertical  dropped  from  the  centre  of  the 
line  joining  his  two  ears  would  pass  through  the  centre  mark 
upon  the  floor.  E  must  either  remove  his  shoes  or  wear  over- 
shoes, in  order  that  he  may  move  noiselessly.  He  needs  a  rod, 
padded  at  the  lower  end,  and  cut  to  such  a  length  that  when 
standing  vertically  upon  the  floor  its  upper  end  is  exactly  on  a 
level  with  0*s  ear,  and  a  toy  snapper. 

The  course  of  the  experiment  is  then  very  simple.  E  adjusts 
the  rod  and  snapper  at  some  point  upon  the  circumference  of 
the  circle.  When  O  says  "  Ready !"  the  snapper  is  sounded  :  the 
signal  must  come  from  O,  in  order  that  Es  position  may  not  be 
shown  by  his  voice.  O  localises,  whether  by  pointing  or  verbally 
(so  and  so  many  degrees),  and  E  records  the  direction  and 
amount  of  error.  The  procedure  is  adapted  both  for  quantita- 
tive and  for  qualitative  work. 

For  another  form  of  sound  cage,  see  M.  Matsumoto,  Yale  Studies,  v.,  1897, 2. 
The  limitation  of  the  movement  of  the  receiver  by  O's  body  could  be  avoided 
only  by  making  the  cage  large  enough  to  contain  a  seated  O  within  it.  On 
the  other  hand,  the  interference  of  the  iron  standard  at  a  critical  part  of  the 
sound  sphere  (back-front  confusions  are  common,  and  deserve  special  study) 
is  a  serious  defect  in  the  construction  of  the  instrument.  The  author  would 
advise,  either  that  the  cage  be  suspended  from  the  ceiling,  and  steadied  by 
light,  movable  supports,  or  that  it  be  held  from  the  sides  as  in  the  Yale  model, 
but  that  the  supports  be  placed  at  a  greater  distance  from  the  cage  itself. 
Preyer  used  a  sound  helmet,  a  cap  set  with  wires  which  pointed  in  various 
directions  and  at  the  extremities  of  which  the  sound  stimuli  could  be  given. 
The  cage  is  preferable. 

It  is  curious  that  there  has  not  been  more  discussion,  in  the  literature,  of  the 
question  of  localisation  methods.  The  author's  experiments  upon  the  matter 
seem  to  justify  the  statements  {a)  that  localisation  by  the  cardboard  semi- 
circles is  slightly  more  accurate,  upon  the  average,  than  localisation  by  the 
pointer  or  by  verbal  description,  and  {b)  that  (Ts  mannerisms  in  localisation 
will,  if  carefully  studied,  throw  some  light  upon  the  mechanism  of  the  localis- 
ing oonsdousDcss. 

Preliminaries. — The  head-clip  may  need  to  be  filed  or 
padded,  if  (7's  head  is  to  be  in  the  right  position.     Neglect  of 


360  Auditory  Perception 

this  precaution  has,  in  the  author's  experience,  brought  the  ear 
40  mm.  below  the  receiver  in  the  positions  25-25  and  25-75. 

The  semicircles  can  be  set  with  sufficient  accuracy  to  the 
half  of  a  division.  Two  series  of  ten  settings,  with  a  position  of 
the  horizontal  semicircle  in  which  a  difference  of  half  a  division 
on  the  scale  corresponded  to  a  difference  of  ,10  mm.  in  height 
above  the  floor,  gave  mean  variations  of  less  than  0.9  mm.  and 
less  than  i.o  mm.  respectively.  It  is  not  possible  to  set  accu- 
rately at  thirds  or  quarters  of  a  division. 

Some  (7*s  are  annoyed  by  the  touch  signal.  It  is  then  advis- 
able that  E  should  give  the  customary  "  Now ! "  pressing  the 
key  down  as  he  utters  the  word.  He  must,  of  course,  always 
stand  in  precisely  the  same  place.  The  objection  to  this  method 
is  that  O  forms  a  very  accurate  idea  of  £"'s  position,  and  so  has 
a  constant  direction  with  which  to  compare  the  apparent  direc- 
tion of  the  sound. 

Note  that,  if  the  rapidity  of  the  break  be  not  constant  through- 
out, the  intensity  of  the  click  will  vary.  As  any  such  variation 
is  undesirable,  E  should  be  cautioned  to  withdraw  his  finger 
from  the  key  in  exactly  the  same  manner  in  every  test. 

Experiment  (i).  —  The  experiment  with  partial  knowledge  is 
recommended  as  an  introductory  experiment,  partly  because  it 
quickens  the  course  of  practice,  and  partly  because  it  facilitates 
introspection.  The  key  should  be  closed  before  the  ready 
signal  is  given,  for  the  reason  that  there  may  be  a  faint  click  at 
make.  This  passes  unnoticed  if  O  is  not  attending;  it  may 
serve  to  distract  him  if  it  follow  the  signal. 

There  will  be  several  cases  in  which  O  is  unable  to  give  a 
definite  localisation.  It  must  then  be  left  to  E'?>  discretion 
whether  he  enter  the  f  in  the  record,  or  repeat  the  test.  If  O 
is  tired  or  inattentive,  repetition  is  useless  ;  if  his  inability  to 
form  a  decision  is  due  to  hesitancy  between  alternative  direc- 
tions, it  may  be  worth  while  to  repeat  the  click  as  many  as 
half-a-dozen  times,  in  order  that  final  judgment  may  be  passed, 
and  (what  is  more  important)  that  the  introspective  reasons  for 
such  judgment  may  be  noted. 

The  numerical  and  introspective  Results  may  be  tabulated  as 
follows. 


§53*   Localisatiam  of  Sounds 


361 


No.or  l». 

Sct: 

Ombrvbo: 

V. 

H. 

V. 

H. 

RftMARKS. 

I 
3 

3 

4 

etc.,  etc 

IS 

«5 
35 

0 
10 
60 
30 

9 
18 

U 
38 

0 
10 

66 
11 

[Enter 

introspections 

here.] 

The  mean  error  and  its  mean  variation  are  then  to  be  calculated, 
{a)  in  the  vertical  plane  for  each  of  the  five  settings  o,  5,  15,  25, 
35  ;  and  (b)  in  the  horizontal  plane  for  each  of  the  six  settings 
o,  10-20,  30-40,  50,  60-70,  80-90.  Thus  the  w.  e.  and  m.  v.  of 
V.  1 5  in  10  trials  might  be  : 


VAKIATlONt 
6.2 
1.2 
4.8 

3-2 

2.8 

3.8 

1.2 
2.2 
3.8 
0.3 


-6 

-  I 

+  5 
-3 

+  3 
+  4 

-  I 

-  3 

+  3 
o 


m.e.—  ->f  0.3 


m,  V.  ss  3.84 


The  introspective  reports  will  hardly  contain  more  than  the 
following.' 

(a)   Certain  of  side,  and  comparatively  sure  of  direction ;  less  sure  of  height. 
Localisation  as  quick  as  perception  of  the  sound. 

(d)  Back,  left ;  both  certain.     No  visualisation. 
(c)   Opposite  right  ear.     Easy. 

(</)  Vertex :  doubtful.     Had  a  strong  bias  for  low  and  back. 

(e)  Doubtful  as  to  back  or  front:  had  to  choose  back.     Curious  feeling 
of  uncertainty  as  judgment  alternated. 

(/)  Sure  of  median.     Distinct  lifting  eye-movement, 
(if)  Judgments  rougher  when  click  is  as  high  up  as  this :  I  donH  like  to 
strain  my  eyes  up  so  £u-. 

i  These  reports  do  not  coRC^Mod  to  the  experiments  of  the  Table  quoted  aboret 


362  Auditory  Perception 

That  is  to  say :  O  is  able  to  describe  the  judgments  as  mediate 
or  immediate,  to  indicate  some  of  the  more  remote  secondary 
criteria,  to  give  the  degree  of  certainty  with  which  a  judgment 
is  passed,  and  to  note  the  influence  of  expectation,  habitua- 
tion, etc. 

The  three  series  of  experiments  will  have  brought  out  (9's 
preference  for  a  particular  method  of  localisation  (visual,  tactual, 
verbal).  This  method  should  be  adopted  for  the  following 
experiments. 

Experiment  (2). — The  fifty  tests  should  be  distributed  sym- 
metrically over  the  available  surface  of  the  sound  sphere.  To 
save  time  in  setting  the  receiver,  the  numbers  V.  o,  10,  20,  30,  40, 
and  H.  o,  10,  20,  30,  40,  50,  60,  70,  80,  90  may  be  taken  as  the 
basis  of  the  Table.  The  remaining  tests  should  be  taken  from 
the  high  and  low  regions  on  either  side  of  the  median  plane, 
back  and  front.  Errors  and  variations  should  be  calculated  as 
before.  The  introspections  will  be,  perhaps,  even  more  scanty 
than  those  of  exp.  ( i ). 

The  second  list  of  fifty  should  be  made  out  with  special  refer- 
ence to  constant  tendencies  or  preferences  on  the  part  of  O. 
Suppose,  e.g.y  that  he  shows  a  distinct  leaning  towards  15-80. 
There  may  be  something  in  the  disposition  of  the  apparatus,  or 
of  the  surrounding  surfaces,  to  favour  that  point ;  or  there  may 
be  a  constant  difference  of  intensive  sensitivity  between  (9's  two 
ears.  The  former  source  of  error  should  have  been  guarded 
against  from  the  outset :  the  room  should  have  been  carefully 
tested  for  echoes,  and  curtains  hung  where  any  such  disturbance 
was  found  or  even  suspected.  A  test  may  now  be  made,  by 
turning  the  sound  cage,  say,  through  90°,  and  noticing  whether 
the  15-80  tendency  persists.^  As  for  the  possible  difference 
between  the  two  ears,  most  men  hear  more  intensively  with  the 
left  than  with  the  right  ear  (r/!  the  *  better  ear'  of  Exps.  V.,  IX. ; 
Fechner,  Abh.  d.  kgl.  sachs.  Ges.  d.  Wiss.,  vii.,  i860,  541  ;  Stumpf, 
Tonpsychol.,  i.,  1883,  Z^A)-  A  test  may  be  made  either  directly, 
by  noting  the  distance  at  which  the  ticking  of  a  watch  ceases  to 
be  audible  for  each  ear  (Sanford,  Lab.  Course,  exp.  61),  or  in- 

^  Reflection  of  sound  from  the  floor  may  be  of  influence,  but  cannot  be  eliminated. 
Cf.  Matsumoto,  Yale  Studies,  v.,  1897,  7- 


§  53*   Localisation  of  Sounds  363 

directly,  by  plugging  the  two  ears  successively  in  exp.  (3)  below, 
and  noting  the  amount  of  lateral  displacement  upon  the  equator 
of  the  sound  sphere  in  each  case.  If  the  preference  is  not 
explicable  in  terms  of  these  two  sources  of  error,  —  and  if 
careful  consideration  fails  to  bring  out  any  other  suspicious 
circumstances  in  the  conduct  of  the  experiment,  —  it  is  pre- 
sumably the  expression  of  some  mental  trend  or  bias,  or  the 
outcome  of  some  association,  which  thus  invites  enquiry.  The 
series  should  then  be  made  out  with  the  view  of  determining 
(a)  the  limits  within  which  the  bias  is  effective,  i.e.,  the  exact 
range  of  scale-divisions  in  the  two  planes  which  evokes  the 
judgment  "15-80";  (b)  the  effect  upon  the  judgment  of  dif- 
ferent modes  of  approach  (by  wide  jumps,  or  by  small  steady 
steps)  to  the  15-80  region  ;  {c)  the  presence  or  absence  of  pref- 
erence for  the  symmetrical  regions  15-20,  35-30,  and  35-70; 
and  so  forth.  The  introspections  should  be  carefully  noted  ; 
especially  should  the  degree  of  confidence  with  which  the  local- 
isations are  made  be  recorded :  and  the  click  may  be  repeated 
as  often  as  O  desires. 

If  no  constant  tendency  has  appeared,  the  second  series  may 
repeat  the  tests  of  the  first,  in  a  different  order. 

Results. — The  general  results  of  these  series  may,  in  all 
probability,  be  summarised  as  follows. 

(i)   There  is  no  confusion  of  right  and  left. 

(2)  There  is  no  confusion  of  right  or  left  and  median. 

(3)  There  are  confusions  of  above  and  below,  before  and  behind. 

(4)  Localisation  is  most  accurate  in  (or  about)  the  transverse  or  auditory 
axis  and  in  the  horizontal  plane. 

(5)  There  b  no  constant  difference  in  accuracy  of  localisation  {a)  between 
the  upper  and  lower  hemispheres,  or  {b)  —  unless  (7s  ears  diflfer  in  sensitivity 
—  between  the  right  and  left  hemispheres.  On  the  other  hand,  (t )  localisa- 
tion in  the  front  is  somewhat  more  accurate  than  that  in  the  back  hemisphere. 

(6)  An  error,  positive  or  negative,  once  established  at  a  given  point,  is 
likely  to  be  carried  in  the  same  sense  through  the  whole  number  of  settings 
on  that  point. 

(7)  Localisations  given  as  'doubtfuP  are  as  a  rule  largely  in  error;  but 
localisations  given  as  *8ure  ^  auv  not  always  correct. 

Individual  differences,  e.g.,  as  regards  (3),  should  be  noted  by 
the  Instructor.     They  may  sometimes  be  accounted  for,  at  least 


364 


Auditory  Perception 


conjecturally,  by  differences  in  the  shape  of  the  pinnae,  irre* 
pressible   tendencies  to  head-movement,  etc. 

Experiment  (3).  —  The  object  of  this  experiment  is  to  test 
the  hypothesis  that  sound  localisation  depends,  primarily  at 
least,  upon  the  relative  intensity  of  the  sound  as  heard  by  the 
two  ears.  If  the  hypothesis  be  correct,  there  must  be  a  general 
shift  of  localisations :  a  sound  given  at  25-0,  e.g.^  will  be  localised, 
not  in  the  median  plane,  but  in  the  direction  of  the  open  ear. 

The  elimination  of  one  ear  is  by  no  means  an  easy  matter. 
It  is  possible,  by  closing  or  shading  one  eye,  under  certain 
general  conditions  of  illumination,  to  secure  a  satisfactory 
monocular  observation  ;  and  even  if  retinal  rivalry  supervene, 
there  are  moments  when  the  field  of  the  open  eye  is  unaffected 
by  that  of  the  closed  eye.  In  closing  one  ear,  on  the  other  hand, 
we  are  merely  substituting  internal  for  external  stimulus.  The 
stopped  ear  rustles  and  throbs  and  buzzes  in  what  may  be  a 
very  distracting  way.  All  that  we  can  do,  therefore,  is  to  make 
the  internal  stimulus  as  constant  as  possible,  while  we  hold  the 
attention  as  steadily  as  we  can  upon  the  external  stimulus.  A 
tightly  fitting  plug  of  cotton  wool  and  wax  answers  the  purpose 
fairly  well.  Cotton  wool  alone  is  not  so  good.  Best  of  all,  if  it 
can  be  procured,  is  one  of  the  conical  eraser-caps  sold  for  attach- 
ment to  a  lead-pencil.  The  cap  has  a  cylindrical  bore,  which 
can  be  filled  with  wax  to  give  the  plug  greater  firmness;  its 
conical  form  renders  it  adaptable  to  any  ear. 

The  effectiveness  of  the  plug  may,  if  the  Instructor  think  it 
worth  while,  be  tested  by  the  watch-tick  experiment  mentioned 
above,  or  by  connection  of  the  telephone  receiver  to  an  induc- 
torium,  as  in  the  experiment  on  distance,  p.  371  below. 

The  numerical  results  will  be  somewhat  as  follows : 


No.  or  Exp. 

Set: 

Observed: 

v. 

H. 

v. 

H. 

I 
2 

3 

4 

5 

IS 

25 

0 

40 

0 
20 

0 
90 
10 

14 

IS 
8 

23 
3S 

94 
18 

97 

n 

0 

§  53*   Localisation  of  Sounds  365 

etc,  etc.     The  mean  errors  and  their  mean  variations  are  to  be 
calculated  as  before.     The  introspections  will  still  be  scanty.^ 

(«)  To  right  of  median :  wanted  to  make  it  median,  but  could  not. 
(^)    Fairiy  sure,  neariy  opposite  left  car:  dl«tin#»  '•^'•-nv»vrmrnt. 
(0    Very  doubtful  of  front  or  back. 

(4)  Doubtful  between  front  and  back :  when  click  was  repeated,  was  quite 
sure  of  back;  immediate  judgment. 

(/)    Opposite  left  ear :  very  clear  and  sure.  —  And  so  forth. 

Experiment  (4)1  —  It  is  important  that  O,  in  entering  upon 
this  experiment,  clearly  represent  to  himself  the  intrinsically 
non-spatial  character  of  sounds,  or  clearly  call  to  mind  the 
associative  character  of  auditory  space.  He  may  say  to  himself 
something  like  this :  "  The  sounds  that  I  am  going  to  hear  are, 
in  themselves,  not  localisable ;  if  I  localise  them,  it  must  be,  in 
the  last  resort,  by  way  of  some  association  with  touch  or  sight ; 
even  a  difference  of  intensity  in  the  two  ears  has  to  be  inter- 
preted, if  it  is  to  be  put  to  spatial  use,  and  the  interpretation 
must  be  in  tactual  or  visual  terms  ;  let  me,  then,  be  on  my  guard 
not  to  read  into  the  sound  impressions  characters  that  really 
attach  only  to  their  tactual  or  visual  associates."  On  the  other 
hand,  it  is  important  that  a  successive  association  be  not  con- 
fused with  a  real  criterion  of  locality.  O  may  first  localise,  and 
//ten  have  a  visual  picture  or  a  reflex  movement  of  the  eyes  :  the 
picture  and  movement  (or  movement-impulses)  are,  in  such  a  case, 
not  concerned  in  the  mechanism  of  judgment.  He  should,  there- 
fore, go  on  to  say :  "  What  I  have  to  analyse  is  the  immediate 
datum  of  consciousness ;  I  must  say  what  I  experience  at  the 
moment  of  perception  of  the  sound ;  if  there  is  nothing  but  a 
g^ven  *  thereness,'  I  must  report  that ;  if  there  is  doubt,  I  must 
analyse  that ;  if  there  is  a  medley  of  perceptual  material  from 
various  sense-departments,  I  must  put  the  whole  situation  into 
words ;  if  an  associated  idea  crops  up  after  I  have  localised,  I 
must  report  it  as  a  later  process;"  and  so  on.  Some  O's  will 
make  nothing  at  all  of  the  test,  and  will  be  apt  to  pride  them- 
selves upon  their  failure;  others  will  secure  a  few  positive 
results,  as  well  as  a  useful  training. 

>  These  reports  do  not  correspond  to  the  experimenu  of  the  Table  quoted  above. 


366  Auditory  Perception 

The  following  introspections  were  taken  with  random  settings 
of  the  semicircles.  The  settings  were,  unfortunately,  not  recorded 
in  units  of  the  instrument,  and,  in  the  majority  of  the  tests  of 
the  first  series,  no  attempt  was  made  to  determine  whether  the 
localisation  was  correct.  O  gave  his  full  attention  to  the  quali- 
tative features  of  the  introspection. 

If  the  Instructor  wish  to  combine  both  the  qualitative  and 
the  quantitative  features  in  the  record,  the  following  procedure 
should  be  employed.  O  formulates  his  qualitative  introspection 
(including  a  verbal  localisation)  before  he  opens  his  eyes.  Then, 
the  cage  remaining  in  its  original  setting,  he  opens  his  eyes,  and 
the  error  of  localisation  is  measured  according  to  his  directions. 
After  this,  he  dictates  his  qualitative  analysis  from  memory. 
The  method  '  works,'  at  least  after  a  little  practice ;  but  there  is 
probably  some  loss  of  accuracy  on  both  sides. 

Series  i 

The  report  given  under  Localisation  is  not  analytic,  but  represents  a  judg- 
ment made  after  the  qualitative  analysis  had  been  performed. 

1 .  Accommodation  (centrally  excited  ?)  to  visual  source  of  sound.  Local- 
isation: front  median. 

2.  Verbal-auditory  *  right.'    Eye-movement  (centrally  excited?). 

3.  As  2 :  but  seemed  to  come  after  the  localisation  had  been  made. 

4.  Verbal -auditory  'left.'  The  sound  was  'placed'  in  a  vague  visualisa- 
tion of  the  room,  cage,  receiver,  etc.     Also  c.  e.  eye-movement. 

5.  No  analysis. 

6.  Verbal-auditory  '  overhead.' 

7.  There  was  a  preliminary  click  at  the  make.  I  consequently  directed 
my  attention  to  the  right ;  I  felt  that  I  was  anticipating  '  rightness '  both  with 
ear  and  eyes. 

8.  Eye-movement  (?)  and  vague  muscular  pulls  on  right  side  of  body. 
Also  the  vague  visualisation  of  4.     Loc. :  right. 

9.  No  analysis.     Loc. :  left  back. 

10.  Known  at  once  as  up-front.     No  analysis  possible.  ' 

Rest  of  5  min. 

11.  Eye-movement,  and  the  visual  placing  of  4  and  8. 

12.  Louder  in  left  ear. 

13.  C.  e.  strain-sensations  in  eyes  and  arms,  as  if  I  were  pointing  to  the 
receiver. 

14.  Period  of  doubt  as  to  the  altitude.  A  distinct  idea  of  running  my 
eyes  up  and  down  a  vertical  line.    There  was  a  *  feeling '  for  the  proper  place. 


4 


§  53-   Localisation  of  Sounds  367 

15.  A  very  certain  *  fieel  *  of  some  sort  about  my  eyes,  as  if  I  were  directing 
my  attention  Tisually  to  the  left. 

16.  No  analysis.    Loc. :  vertex. 

17.  As  15,  with  up  for  left. 

I S.  As  1 5 .  The  eye  *  feel  *  is  followed  directly  by  a  verbal -auditory  sjrmbol, 
*  median  front.* 

19.  No  analysis.    Lac, :  opposite  left  ear. 
ao.  Visual  elements,  mainly ;  but  vague. 

Rest  of  5  min. 

3t.  C.  e.  eye-mo\>ement  sensations;  vague  visuiil  placing,  as  in  4  and  8; 
▼erbal-auditory  *  up  there.* 

22.  Tried  several  times:  10  or  12  clicks.  Ver}*  uncertain  as  to  front  or 
back.  Knew  it  was  level  with  ears  and  median.  During  the  conflict,  I  could 
make  it  front  or  back  by  expectation.  Distinct  movements  of  scalp  and  eye> 
brows,  and  always  a  visual  placing,  while  attending  to  front  or  back.  Loc, : 
front.     Correct. 

23.  Eye-movement  and  visualisation  as  before.  Lac. :  knew  it  was  *  right,' 
but  estimated  much  too  high. 

24.  Very  full  sound  in  left  ear.     Lac, :  opposite  left  ear.     Correct. 

25.  Visualisation  of  the  receiver,  as  in  4.  Imaged  arm-movement  (point- 
ing).    Later:  verbal-auditorj*  *  back.*    Lac.:  low  back.     Correct. 

26.  As  24,  but  opposite  right  ear.     Lac. :  correct. 

27.  Visualisation  and  verbal-auditory  *  vertex.*    Lac. :  correct. 

2S.  In  doubt  between  front,  left,  high  (my  place  of  preference  in  the 
previous  series)  and  front,  left,  level.  Distinctly  visual  elements  during  the 
conflict.  —  Setting  was  back,  median,  horizontal. 

29.  Full,  intense  sound  in  left  ear.  Lac. :  opposite  left  ear.  Too  high ; 
the  receiver  was  below  level. 

30.  C.  e.  arm-movement  sensations  (reaching  to  receiver)  and  eye-move- 
ments  (looking  at  it).    Z.^v. ;  front  median.    Correct. 


Series  2 

31.  Eye-movement  (c.  e  )  upwards,  and  lifting  of  eyebrows.     Lac. :  front, 
left,  high.     Actual  setting  was  back,  left  (near  median)  and  high. 

32.  Reflex-like  muscular  movements  in  face.     Lac.:  left,  back,  horizontal. 
Correct. 

33.  C.  e.  eye-movement.     Lac. :  high,  right,  near  median.     Correct. 

34.  No  analysis.    Lac. :  front,  near  vertex.     Setting  was  near  vertex,  left, 
and  back. 

35.  C.  e.  eye-movement  and  the  vague  placing  outwardly  in  visual  space. 
Lac. :  too  hr  front ;  setting  was  vertex,  right. 

36.  Full  intensity  in  right  ear;    also  distinct  tendency  to  eye-movement 
(still  c.  e.,  however).    Lac.:  opposite  right  ear,  level.    Correct. 


368  Auditory  Perception 

37.  No  eye-movement;  but  distinct  visual  placing.  Saw  the  receivei 
behind  me.     Loc. :  directly  behind,  level.     Correct. 

38.  Heard  the  make-click,  and  was  sure  it  was  opposite  the  right  ear,  level. 
But  the  break-click  sounded  higher.  Tried  4  times  to  decide.  Visualised  in 
all  trials.  —  It  was  really  low,  right,  back. 

39.  Tried  3  times.  Slight  doubt  between  back  low  and  front  low 
(/.^.,  between  62  and  87  on  the  horizontal  circle).  Vague  *  external'  vis- 
ualisation and  c.  e.  eye-movement.  Loc:  front,  left,  low.  Was  back, 
left,  low. 

40.  Distinct  eye-movement:  actually  moved?  Loc:  opposite  left  ear, 
level.    Was  really  lower. 

41.  C.  e.  eye-movement  and  visualisation.  Loc:  median,  fairly  high,  front. 
Was  slightly  to  left  of  median. 

42.  Analysis  as  41.     /-<?<:.;  opposite  left  ear,  but  low.     Correct. 

43.  Analysis  as  in  41.     Loc  :  up,  right,  front.     Correct. 

44.  C.  e.  eye-movement ;  less  visualisation.  Loc :  median,  front.  So  far 
correct ;  but  localised  too  low. 

45.  Vague  picture  of  self  in  chair.  Saw  receiver  as  if  from  experi- 
menter's position.  Saw  only  the  back  of  the  chair  distinctly.  Loc:  low, 
median,  back.    Correct. 


It  is  clear,  from  these  records,  that  cases  of  confusion,  i.e., 
cases  where  a  repetition  of  the  stimulus  is  necessary  to  the  for- 
mation of  a  judgment,  are  especially  likely  to  throw  light  upon 
the  mechanism  of  localisation.  The  change  of  attitude  that 
constitutes  the  change  from  *  hereness '  to  *  thereness '  gives  a 
better  opportunity  for  introspection  than  does  the  *  hereness '  or 
the  *  thereness  *  by  itself. 

Instructive  results  may  be  obtained  from  series  where  O  is 
told  beforehand,  "  You  will  be  given  a  sound  at  this  point  or  at 
that "  (two  possibilities),  or,  **  You  will  be  given  a  sound  at  so- 
and-so"  (complete  knowledge).  Analysis  must  here  be  directed 
upon  the  processes  involved  in  expectant  attention. 

Questions. — The  first  5  questions  have  been  sufficiently 
answered  in  what  precedes.  Question  (6)  must  be  answered,  in 
part,  from  the  literature.  Question  (7)  should  be  approached 
methodically.  The  different  part  functions  of  space  perception 
(the  various  space-determinations  and  space-relations)  should  be 
enumerated,  and  the  three  sense-spaces  compared  term  for  term. 
See  Kiilpe,  Outlines  of  Psychology,  334  ff.,  374  ff. ;  J.  von 
Kries,  Zeits.  f.  Psych.,  i.,  1890,  235  (an  extremely  suggestive 


§  53*   Localisation  of  Sounds  369 

jiapcr);  A.  Hofler,  Psychologic,  1897,  342;  A.  Hofler  and  S. 
Witasek,  Psych.  Schulversuche,  1900,  24. 

Related  Experiments. — There  are  many  modifications  of 
this  Experiment,  which  serve  to  bring  out  the  importance  for 
localisation  of  absolute  intensity,  relative  and  absolute  pitch, 
clang-tint,  phase,  the  subjective  factors  of  attention  and  fatigue, 
etc.,  etc.  All  of  these  variants  must  be  taken  into  account  in  a 
final  theory  of  sound  localisation.  We  can  here  do  no  more 
than  mention  some  of  the  most  important  experiments.  It  may 
be  said  that  there  is  nothing  in  the  results  of  any  of  them  to 
cast  doubt  upon  the  hypothesis  accepted  in  the  text :  that  local- 
isation depends  primarily  upon  the  relative  intensity  of  the 
sound  as  heard  by  the  two  ears. 

{a)  Variation  of  the  Receiving  Apparatus. — Take  a  short 
series  of  tests,  as  in  (2)  above,  with  the  pinnae  strapped  flat 
against  the  side  of  the  head.  Take  three  further  series,  with 
the  pinnae  strapped  as  before,  but  with  two  artificial  pinnae  of 
cardboard  tied  to  the  head,  their  concavities  pointing  backwards, 
upwards  and  downwards. — J.  Kessel,  Arch.  f.  Ohrenheilk., 
xviii.,   1882,   120. 

Carefully  fill  the  external  ear  passages  with  water,  and  plunge 
the  whole  head  under  water.  Note  that  localisation  (even  as 
regards  right  and  left)  is  impossible  ;  sounds  are  localised  simply 
'within  the  head.*  —  E.  Weber,  Ber.  d.  kgl.  sachs.  Ges.  d.  Wiss., 
185 1,  30. 

{b)  Variation  of  the  Character  of  the  Stimulus.  —  Take  a 
series  of  tests,  before  and  behind  in  the  median  plane,  with  the 
tone  of  a  tuning-fork,  the  clap  of  two  wooden  blocks,  and  a 
spoken  word,  as  stimuli  Note  the  relative  difficulty  of  localisa- 
tion in  the  first  case.  The  fork  must,  of  course,  be  either  so 
remote,  or  screened  in  such  a  way,  that  O  does  not  hear  the 
thud  of  the  felt  hammer  as  it  strikes.  —  Rayleigh,  Nature,  xiv., 
1876,  32;  cf.  Sanford,  Course,  83,  e.xp.  10 1  d. 

(c)  Intracranial  Localisation :  Purkinje's  and  E.  Wcbct's  Ex- 
periments. —  (i)  Connect  the  two  ears  by  a  piece  of  rubber  tub- 
ing. Strike  a  tuning-fork  sharply,  and  set  its  stem  upon  the 
middle  point  of  the  tubing.  Note  that  the  sound  is  heard  in 
the  occipital  region  of  the  head.     Shift  the  position  of  the  fork 

3B 


370  Auditory  Perception 

upon  the  tubing ;  remove  the  tubing  entirely  from  one  ear :  note 
the  results.  Repeat  the  experiment  with  a  very  weakly  sound- 
ing fork.  —  K.  L.  Schaefer,  Zeits.  f.  Psych.,  i.,  1890,  300;  M. 
Matsumoto,  Yale  Studies,  v.,  1897,  37;    Sanford,  Course,  exp. 

102.  (ii)  Strike  a  tuning-fork  sharply,  and  set  its  stem  upon 
the  vertex.  The  tone  sounds  within  the  occiput,  in  the  median 
plane.  Now  close  the  opening  of  one  ear  with  the  finger :  the 
sound  is  heard  within  the  closed  ear.  Repeat  the  experiment, 
with  the  fork  placed  at  various  points  in  the  occipital  and  pari- 
etal regions.  —  Weber,  loc,  cit.^  29  ;  cf.  Sanford,  Course,  84,  exp. 

103.  Schaefer  gives  a  pretty  variant  of  the  experiment.  "  Sing 
loudly  a  very  deep  ooy  and  while  it  is  sounding  stop  one  ear,  not 
too  closely.  The  00  shifts  from  the  larynx  to  the  closed  ear. 
Now  treat  the  other  ear  in  the  same  way ;  the  00  travels  to 
the  median  plane  within  the  head"  {loc.  cit.,  305). 

(d)  The  Effect  upon  Localisation  of  Fatigue  and  Attcjition.  — 
(i)  Expose  one  ear  for  30  sec.  (by  means  of  a  tube  connected 
with  the  resonator)  to  the  tone  of  a  ^^  fork.  Now  sound  the 
same  fork  in  the  median  plane  (in  the  *  subjective'  median  plane, 
if  O's  ears  are  unequal),  and  require  O  to  localise  it.  He  places 
it  a  little  away  from  the  median  plane,  in  the  direction  of  the 
unstimulated  ear.  An  a^  fork,  or  in  general  any  fork  of  a  dif- 
ferent pitch,  is  unaffected  by  the  r^-fatigue.  (ii)  Sound  two  ^ 
forks  by  striking  the  one  upon  the  other.  Hold  them  at  equal 
distances  from  the  two  ears,  or  set  their  stems  in  the  openings 
of  the  ear  passages.  You  are  able  at  will,  according  to  the  direc- 
tion of  attention,  to  localise  the  single  resulting  tone  in  the  right 
or  left  ear.  —  Fechner,  Abh.  d.  kgl.  sachs.  Ges.  d.  Wiss.,  vii., 
i860,  549. 

{e)  Localisation  with  Two  Stimuli.  —  (i)  Hold  two  unison 
forks,  sounding  with  equal  loudness  in  opposite  phase,  close  up 
to  the  two  ears.  Note  that  the  resulting  tone  is  localised  within 
the  occiput  in  the  median  plane.  Try  the  effect  of  removing  the 
two  sources  of  sound,  slowly  and  evenly,  away  from  the  ears. 
Repeat  the  experiment  with  sameness  of  phase.  —  S.  P.  Thomp- 
son, Phil.  Mag.,  Ser.  5,  1877,  iv.,  274;  1878,  vi.,  383;  Schaefer, 
loc.  cit.;  V.  Urbantschitsch,  Pfluger's  Arch.,  xxiv.,  i88r,  579. 
(ii)   Hold  two  unison  forks,  sounding  at  unequal   intensities, 


I 


§53*    Localisation  of  Sounds 


Z7i 


equidistant  from  the  two  cars.  Note  that  the  sound  is  heard  ex- 
clusively by  the  ear  on  whose  side  is  the  louder  fork.  —  Fechner, 
/oc.  cit.,  543  fF. ;  cf.  Dove's  experiment,  549  f.  (iii)  Systematic 
experiments  may  be  carried  out  on  the  sound  cage,  with  two  tele- 
phone receivers.  The  results  will  be  that,  apart  from  occasional 
confusions  of  back  with  front  and  above  with  below,  the  resulting 
sound  is  localised  by  ^  at  a  point  midway  between  the  points  at 
which  the  two  stimuli  are  given.  —  Matsumoto,  loc.  cit,  42  ff. 
On  the  conditions  of  separate  localisation  with  simultaneous 
stimuli,  see  von  Kries,  loc.  cit. 

Schaefer  recommends,  for  (i),  two  telephones  connected  to  the  two  second- 
ary coils  of  Preyer's  double  inductorium.  The  same  arrangement  will  serve 
for  (iii). 

Matsumoto*s  apparatus  is  shown  in  the  diagram.  A  fork  of  250  vs.  is 
placed  as  a  shunt  across  the  telephone  circuit.  The  intensity  of  the  tone  in 
a  is  r^ulated   by  the  posi- 


Fomt 


^ 


Fit;.  100. 


tion  of  the  sccondarj*  coil;      (^TTtRY 
that    of   the    tone    in    ^   by  t — 

a  copper-sulphate  rheostat. 
The  author  has  not  tested 
this  arrangement  An  evi- 
dent criticism  is  that,  owing 
to  the  reciprocal  effect  of 
the  secondary  upon  the  pri- 
mar)'  coil,  there  will  be  intensification  of  the  sound  in  d  when  the  sound  in  a 
is  intensified.  As  Matsumoto  does  not  mention  this  source  of  error,  it  is 
probably  negligible. 

If  the  sound  cage  is  not  available,  the  present  experiment  may  be  per- 
formed by  help  of  two  cheap  ('pipe  metal,'  open)  organ-pipes,  held  upon 
upright  stands,  and  connected  by  rubber  tubing  to  a  T-way  and  thence  to  a 
foot  bellows.     C/.  p.  359  above. 

So  far  we  have  been  dealing  only  with  the  apparent  direction 
from  which  a  sound  comes.  The  problem  of  localisation  includes, 
further,  an  enquiry  into  the  apparent  distances  of  sounds.  All 
experiments  go  to  prove  that  (as  was  said  above,  p.  358)  our  judg- 
ment of  distance  is  a  matter  of  association.  A  sound  of  known 
intensity  is  localised,  by  visual  association,  at  a  certain  distance  : 
similar  sounds  of  greater  intensity  are  then  perceived  as  nearer, 
similar  sounds  of  less  intensity  as  farther  off.  The  law  may  be 
roughly  demonstrated  by  connecting  the  receiver  upon  the  sound 


3/2  Auditory  Perception 

cage  with  the  secondary  coil  of  an  inductorium  from  which  the 
vibrator  and  Helmholtz  side-wire  have  been  removed.  Matsumoto 
thinks  that,  within  certain  limits,  the  "  perceived  distance  of  the 
sound  increases  in  arithmetical  progression  when  the  intensity 
of  the  sound  diminishes  in  geometrical  progression  "  {loc,  cit.^ 
60).  As,  however,  his  observers  had  only  the  intensity  of  the 
sound  to  serve  as  basis  for  judgment,  it  is  more  probable  that 
the  law  should  read :  *  the  perceived  intensity  of  the  sound 
diminishes  in  arithmetical  progression  when  its  physical  inten- 
sity diminishes  in  geometrical  progression.'  The  results  would 
then  be  simply  a  rough  confirmation  of  the  validity  of  Weber's 
law  for  sound. 

The  procedure  here  indicated  is  open  to  the  objection  that  O  knows  the 
actual  distance  in  every  test.  We  may  therefore  discard  the  cage  altogether, 
and  either  move  the  single  receiver  in  and  out,  along  a  measure,  or  use  two 
receivers,  and  allow  O  to  estimate  the  distance  of  the  (singly  heard  and 
mediaoly  localised)  double  click. 

If  two  receivers  are  used,  there  are  two  modes  of  connection,  (i)  In 
series.  This  is  the  better  way,  if  the  receivers  are  mechanically  and  electri- 
cally very  similar :  for  precisely  the  same  amount  of  current  goes  through  the 
coils.  There  wil'  still  be  chance  variations  in  the  response  of  the  receiver 
plates ;  but  these  can  be  minimised  —  if,  indeed,  they  are  noticeable  at  all  — 
by  keeping  the  diaphragm  well  away  (.75  to  i.o  mm.)  from  the  core  of  the 
coil.  (2)  In  parallel.  This  is  the  better  way  if  the  receivers  react  unequally, 
or  if  0\  ears  are  unequal,  since  it  is  possible  to  put  resistance  (no.  36  or  40 
German-silver  wire)  in  the  strong  line  until  the  localisation  is  median. 

If  clicks  and  not  tones  are  employed,  the  rapidity  of  break  must  (as  was 
said  above)  be  kept  constant.  This  can  best  be  accomplished  by  the  intro- 
duction of  an  automatic  key. 

Literature.  —  M.  Matsumoto,  Studies  from  the  Yale  Psycho- 
logical Laboratory,  v.,  1897,  i.  Besides  the  references  given 
by  Matsumoto,  cf.  O.  Kiilpe,  Outlines  of  Psychology,  1895, 
374  ff. ;  A.  Hofier,  Psychologic,  1897,  342. 


CHAPTER   XI 

Tactual  Space  Perception 

BXPERIMSNT  XXXm 

§  54.  Loealiiation  of  a  Single  Point  upon  the  Skin.  Cautions 
not  noted  in  tJu  Text.  —  Avoid  temperature  points  ;  a  vivid  sen- 
sation of  heat  or  cold  is  distracting.  If  a  temperature  point  be 
touched,  record  the  fact,  whether  O  localise  or  not.  But  do  not 
use  the  experiment  in  drawing  your  final  conclusions ;  return 
to  the  neighbourhood  of  the  point  later  on  in  the  experimental 
series. 

The  length  of  the  interval  between  experiment  and  experi- 
ment must  be  regulated  according  to  O's  introspections.  The 
after-image  of  pressure  will  probably  be  found  to  vary  in  dura- 
tion for  different  observers. 

It  may  happen  that  O  declares  all  traces  of  after-image  to 
have  vanished,  but  that  nevertheless  a  new  stimulation  serves 
to  bring  out  a  pressure  after-image  at  the  spot  last  stimulated. 
This  means  that  the  skin  is  not  thoroughly  rested.  The  inter- 
val between  experiments  must  then  be  lengthened. 

Questions.  — (i)  By  the  *  local  sign,*  which  is  most  probably 
visual.     Outline,  156. 

(2)  All  the  later  errors  are  probably  smaller  than  the  earlier 
of  the  same  region.     For  practice,  see  Kiilpe,  Outlines,  43,  340. 

(3)  The  errors  will  probably  be  smaller  on  the  R  and  U  boun- 
dary lines,  owing  to  visualisation ;  and  on  the  P  line,  owing  to 
visualisation  and  to  an  intrinsically  lower  localisation  limen. 
The  skin  at  the  carpal  folds  is  rigidly  attached  to  the  underlying 
tissues ;  and  the  wrist  is  exposed,  and  so  gets  more  practice 
than  the  upper  part  of  the  arm. 

(4)  Diflferent  observers  give  very  different  results.  Since  the 
right  hand  is  localising,  and  will  tend  to  fall  short,  there  may  be 

373 


374  Tactual  Space  Perception 

a  displacement  of  all  localisations  towards  the  U  border  of  the 
left-arm  area.  Again :  the  localisations  may  be  thrown  out 
towards  the  R  and  U  borders  alike,  or  thrown  up  towards  the 
P  border,  owing  to  visualisation,  etc.  Cords,  scars,  etc.,  may 
*  attract '  localisation  towards  them,  by  serving  as  visual  or  tac- 
tual landmarks. 

(5)  a.  Visualisation  is  not  excluded.  Hence  the  experiment 
is  not  a  pure  tactual  experiment. 

b.  The  errors  are  not,  as  they  stand,  to  be  counted  as  errors 
of  localisation.  Chance  must  be  taken  into  account.  See  W.  B. 
Pillsbury,  Amer.  Journ.  of  Psych.,  vii.,  1895,  42. 

c.  The  units  of  direction  are  rough.  Errors  do  not  all  fall 
upon  the  eight  radii  employed. 

(6)  Experiment  upon  the  right  arm,  to  see  whether  the  local- 
isations are  shifted  towards  the  R  side  of  the  area.  Experiment 
upon  the  back  of  the  neck,  visualisation  of  which  is  not  so  accu- 
rate ;  or  upon  any  part  of  the  body  which  has  not  clear  visual 
boundary  lines. 

Related  Experiments. — This  experiment  is  capable  of  many 
variations,  all  of  which  are  of  interest  for  the  theory  of  tactual 
localisation.  Thus  O  may  localise  the  point  of  impression  with- 
out himself  touching  his  arm :  he  arrests  the  point  of  his  pencil 
in  the  air,  over  what  he  takes  to  be  the  point  of  stimulation.  E 
then  drops  a  perpendicular  to  the  arm,  and  measures  the  amount 
and  direction  of  the  error  of  localisation  (Henri,  100;  C.  S. 
Parrish,  Amer.  Journ.  of  Psych.,  viii.,  1897,  250).  Or  6^  may 
open  his  eyes,  after  the  arm  has  been  stimulated,  and  mark  the 
point  of  stimulation  with  his  pencil  upon  a  life-size  photograph 
or  plaster  of  Paris  model  of  his  arm  (Henri,  117;  W.  B.  Pills- 
bury,  Amer.  Journ.  of  Psych.,  vii.,  1895,  55).  Or  he  may  look 
at  his  arm  while  E  is  stimulating  it,  and  then  close  his  eyes, 
and  localise  the  point  in  the  usual  way  with  his  own  pencil 
(Henri,  106 ;  Pillsbury,  44,  46).  Or  he  may  follow  the  ordinary 
method,  but  make  a  special  effort  to  suppress  or  to  reinforce 
visualisation  during  the  time  that  E  is  holding  the  point  upon 
his  arm  (Henri,  98  ;  Pillsbury,  46,  51). 

Literature.  —  The  method  followed  in  this  Experiment  is 
known  as  *  Weber's  Second  Method  ' :  see  E.  H.  Weber,  Ueber 


§  55-   Discrimination  of  Two  Points  375 

den  Raumsinn»  etc.  (Verb.  d.  k.  sachs.  Ges.  d.  Wiss.,  math.-phys. 
ClasseX  1852,  89  f.  Cf.  also  J.  Czermak,  Physiol.  Studien,  ii., 
1855,  52  f. ;  W.  B.  Pillsbury,  Amer.  Journ.  of  Psych.,  vii.,  1895, 
42 ;  W.  Lcwy,  Zeits.  f.  Psych.,  viii.,  189s,  254;  V.  Henri,  Ueber 
d.  Raumwahmehmungen  d.  Tastsinnes,*  1895,  90  ff.  (esp.  102 
fF. ) ;  Sanford,  Course,  2,  exp.  2  ;  C.  H.  Judd,  Philos.  Studien,  xii., 
1896,  411  f. 

For  and  against  local  signs,  seeWundt,  Phys.  Psych.,  ii.,  1893, 
36  ff.,  215  ff.,  231  ff. ;  Outlines,  105,  127  ff.,  134  ff . ;  Kulpe, 
Outlines,  344,  369;  James,  Psych.,  ii.,  155  ff.,  167  ff.  ;  Sturapf, 
Ueber  d.  psychol.  Ursprung  d.  Raumvorstellung,  1873,  106  fiF., 
272  ff. ;  T.  Lipps,  Psychol.  Studien,  1885,  i  ff. ;  Grundtatsachen 
d.  Seelenlebens,  1883,  472  ff. ;  Henri,  Raumwahmehmungen, 
159  ff. ;  Hering,  Beitr.,  v.,  1864,  323;  Hermann's  Hdbch.,  iii., 
^  1879,  565,  572;  J.  Ward,  art.  Psychology,  Encycl.  Brit.,  9th 
ed.,  1886,  46,  53.  For  R.  H.  Lotze's  theory  of  local  signs,  see 
the  Medicinische  Psych.,  1852,  325  ff. ;  the  appendix  to  Stumpf  s 
Ursprung,  etc. ;  and  the  references  in  Henri,  177. 

These  references  are  given  rather  for  the  Instructor  than  for 
the  student.  The  road  of  space  theory  is,  as  we  said  above 
(p.  256),  rough  travelling  for  the  beginner  in  psychology ;  and 
the  question  of  nativism  vs.  genesis  may  well  be  postponed  until 
the  conclusion  of  this  Course. 


EXPERIMENT   XXXIV 

§  55.  The  Discrimination  of  Two  Points  upon  the  Skin.  Cau- 
tions  not  noted  in  tfu  Text. — The  cautions  of  Exp.  XXXHI. 
must  be  regarded  with  great  attention  here.  Disturbance  by 
temperature  spots  must  be  noted,  but  is  not  a  reason  for  repeat- 
ing an  experiment.  Temperature  difficulties  may,  however, 
justify  a  slight  travelling  out  of  the  line,  in  the  lateral  direction. 
Cf.  G.  A.  Tawney,  Philos.  Studien,  xiii.,  1897,  169.  —  The  inter- 
vals between  experiments  must,  naturally,  be  longer  than  they 
were  in  Exp.  XXXHI. 

1  This  work  has  a  bibliography  of  322  titles. 


376 


Tactual  Space  Perception 


Tawney  recommends  an  application  time  of  4  sec.  and  an 
interval  of  10  to  20  sec.  (165  f.,  173).  C.  H.  Judd  (Philos. 
Studien,  xii.,  1896,  417)  advises  3-sec.  applications.  These  ap- 
plication times  are,  in  the  author's  judgment,  needlessly  long. 

It  is  important  to  keep  the  temperature  of  the  room  constant : 
E.  Loewenton,  Versuche  iib.  d.  Gedachtniss  im  Geb.  d.  Raum- 
sinnes  d.  Haut,  1893,  18;  Tawney,  166. 

The  questions  of  method  (see  References  below),  of  the  time,  vacillations 
and  relative  certainty  of  judgment  (Tawney,  194),  of  the  direction  of  atten- 
tion (194,  210  f. ;  Judd,  429),  and  of  the  existence  of  two  limina  (Tawney, 
174),  are  all  weighty  questions.  They  cannot,  however,  be  discussed  in  this 
volume. 

Note  that  the  aesthesiometer  is  so  constructed  that  the  limbs  are  always 
vertical  to  the  cutaneous  surface  (Tawney,  164). 

Results.  —  The  following  is  the  first  set  of  results  ob- 
tained from  a  careful  O. 

Left  fore-arm,  volar  surface,  < — >■ 


Mm.  i 

Jdgt. 

Jdgt. 

Mm.  t 

24 

2 

— 



23 

2 

— 

— 

22 

2 

2 

22 

21 

2 

2 

21 

20 

I~~~-~^^ 

2 

20 

19 
18 

I 
I 

19 
18 

— 

— 

I 

17 

— 

— 

I 

16 

The  determination  of  the  average  value  is  here  very  easy.  We 
take  the  mean  of  20  (the  first  *One'  of  |)  and  19  (the  first 
*Two'  of  W  The  value  is,  therefore,  19.5  mm.;  it  will 
decrease  with  practice.  The  effect  of  the  error  of  expectation 
is  shown,  though  not  clearly.  There  is  no  introspection,  over 
and  above  the  words  *  One,'  'Two,'  and  the  'Don't  know'  of 
exp.  3    f  • 

The  following  is  a  series  taken  from  the  same  6^  at  a  more 
advanced  stage  of  practice. 


I 


§  5S-   Discrimination  of  Two  Points 
Left  wrist,  volar  surfue,  ^      » 


377 


Um.k 

J<lit 

J<«r. 

Mm.  t 

30 

a  (quickly) 

_ 

30 

90 

u 

— 

30 

«5 

M 

— 

«5 

14 

« 

— 

14 

«3 

M 

— 

«3 

13 

U 

2  (ceruin) 

13 

tl 

3(withhesiUtioQ) 

2 

II 

u 

5  Spread   out,  al- 
(    most  like  i 

9 

At  first  3,  then  i 

2 

9 

Suggestion  of  3 ; 

8 

they  seemed  to 
,  run  together. 

2  (with  hesitation) 

8 

7 

Line  or  oval ;  i 

I 

7 

6 

I 

I 

6 

5 

I 

I 

5 

4 

I 

— 

4 

The  \  series  is  unnecessarily  long ;  the  exps.  with  9  and  8 
mm.  show  the  error  of  habituation.  A  shorter  series  would  have 
given  the  values  10  or  9  and  8  mm.,  instead  of  7  and  8  mm. 
The  introspections  show  great  improvement. 

Henri  (6)  gives  the  following  introspective  stages  for  an  f 


scnes: 

(a)   One  small  sharp  point ; 
(^)    a  larger,  blunter  point ; 
(c)    a  small  area  of  oval  form ; 
(it)  aline; 

(/)    two  points,  near  together,  connected  by  a  line  of  light  contact ; 
(/)  two  separate  points  ;  direction  of  the  line  of  junction  uncertain  ; 
(f)  two  separate  points ;  direction  known. 

This  is,  of  course,  an  ideal  series.  See,  further,  G.  A.  Tawney, 
Psych.  Rev.,  il,  1895,  587  fF. ;  Philos.  Studien,  xiii.,  1897,  174, 
etc. ;  C.  H.  Judd,  idid.,  xii.,  1896,  428. 

The  perception  of  two  separate  points,  while  the  judgment  of 
direction  is  still  uncertain,  belongs  to  a  group  of  phenomena 


378  Tactual  Space  Perception 

which  have  often  been  discussed  in  experimental  psychology, 
but  which  still  await  systematic  treatment.  See  Judd,  419,  423, 
430  f.,  436  f.  According  to  G.  S.  Hall  and  H.  H.  Donaldson, 
movement  over  the  skin  is  perceived  before  the  direction  of 
movement  can  be  given  (Mind,  O.  S.,  x.,  1885,  557);  cf.  James, 
Psych.,  ii.,  172  f.  James  remarks,  again,  that  "difference,  .  .  . 
immediately  felt  between  two  terms,  is  independent  of  our  ability 
to  identify  either  of  the  terms  by  itself,"  and  posits  **a  real 
sensation  of  difference  "  (i.,  495  f.,  and  references).  A.  Gold- 
scheider  notes  (Ges.  Abh.,  ii.,  196)  that  movement  of  a  limb  may 
be  perceived  before  there  is  any  certainty  as  to  the  direction  of 
its  movement.  Kiilpe  refers  these  cases  to  the  operation  of  "  a 
psychological  law  absolutely  valid  within  certain  limits,  —  the 
law  that  general  denominations  are  more  easily  reproduced  than 
special"  (Outlines,  172).  This  law  is  "itself  only  a  particular 
case  of  the  universal  rule  that  the  frequency  of  excitation  exerts 
an  influence  upon  the  reproductivity  of  impression.  .  .  .  When 
memory  begins  to  fail  in  consequence  of  age,  concrete  names 
.  .  .  are  forgotten  before  abstract.  .  .  .  The  existence  of  a 
difference  between  the  compared  sensations  is  earlier  remarked 
than  the  direction  which  it  takes,  or  the  nature  of  the  objects 
between  which  it  obtains"  (173  f.).  The  hypothesis  of  specific 
*  movement  sensations '  and  *  difference  sensations '  is  discussed 
and  rejected,  pp.  347  f.  Finally,  Kiilpe  brings  under  the  same 
heading  of  *  reproduction  of  the  general '  many  of  the  results  of 
experiments  upon  the  duration  of  the  association  (association- 
reaction). 

Kiilpe's  law  is  undoubtedly  valid  in  many  cases.  But  the 
facts  need  sifting.  A  small  coloured  surface,  seen  from  a  suf- 
ficient distance,  looks  colourless  (see  Sanford,  Course,  142,  exp. 
143).  Is  this  merely  because  the  abstract  term  Might'  is  more 
easily  reproducible  than  the  concrete  term  '  red  *  or  *  blue  * }  On 
the  other  hand,  Wundt  explains  the  confusion  of  very  weak  warm 
sensations  with  minimal  pressure  sensations  by  their  reference 
to  a  single  sense-organ  (Phys.  Psych.,  i.,  1893,  416):  so  that  the 
law  is  not  confined  to  the  domain  of  perception,  but  has  an 
application  in  the  sphere  of  sense.  The  whole  matter  calls  for 
reinvestigation,  more  especially  in  the  light  of  Meyer's  recent 


§  55-   DiscrimipMtioH  of  Two  Points  379 

statement  (Zeits.  f.  Psych.,  xvi.,  1898,  359  ff.)  that  the  time 
required  for  the  cognition  of  tonality  is  also  sufficient  for  the 
cognition  of  determinate  pitch. 

Questions. — (i)  For  expectation,  see  Kiilpe,  Outlines,  39, 
Let  O  write  out  an  introspective  analysis  of  the  state.  If  the 
tendency  to  correct  were  present,  the  fact  must  be  noted :  the 
results  will  be  variable  and  unreliable. 

(2)  Habituation  (Kulpe,  41),  the  tendency  to  have  now  the 
same  perception  that  you  have  had  before.    Fatigue  (Kiilpe,  43). 

(3)  In  order  that  the  conditions  may  be  kept  constant.  The 
d^ree  of  habituation  and  fatigue,  and  the  amount  of  practice 
and  expectation,  with  which  the  region  of  change  is  approached, 
should  evidently  be  the  same  for  both  series. 

(4)  O  may  have  been  inattentive,  tired,  habituated,  etc.  E 
may  have  made  the  series  too  long,  have  waited  too  long  between 
separate  experiments,  have  made  the  waits  irregular,  etc. 

(5)  One  has  no  right  to  argue  from  the  results  of  a  given 
method  to  that  of  a  single  experiment  taken  by  a  different 
method.  We  have  determined  the  required  distance  by  creeping 
up  to  it,  from  two  different  positions,  cautiously  and  by  slow 
degrees.  We  have  used  a  gradation  method,  a  method  of  steady 
approach  by  small  steps.  When  the  compasses  are  set  down 
once  and  for  all,  as  the  Question  supposes,  we  have  travelled  into 
an  error  method.  In  an  error  method,  a  single  distance  would 
be  set  down,  over  and  over  again,  and  introspective  *  shots  *  taken 
at  it.  Notes  would  be  made  of  the  number  of  cases  in  which 
there  was  a  perception  of  two  points,  and  of  the  number  in 
which  there  was  a  perception  of  one.  From  these  data  we  could 
calculate  out  the  distance  required.  But  it  is  unfair  to  take  a 
single  trial :  the  error  methods  demand  a  large  number  of  trials. 
The  careful  stalk  may  not  be  more  successful  than  a  multitude 
of  *  shots ' ;  we  have  no  right  to  compare  it  with  a  single  shot.  — 
These  considerations  show  us  an  important  truth :  the  truth 
that  an  experiment  which  aims  at  a  quantitative  result  is  never 
a  deUched  trial,  capable  of  being  performed  by  itself  without 
respect  to  other  experiments,  but  is  always  an  experiment  within 
an  experimental  method,  i.e.,  a  detached  member  of  a  systema- 
tised  series  of  experiments. 


380  Tactual  Space  Perception 

In  actual  fact,  the  probabilities  are  (the  arm  being  tired)  that 
the  two  impressions  would  give  rise  to  a  single  perception. 

(6)  Between  the  perceptions  of  two  points  and  of  one  point, 
there  will  probably  be  perceptions  of  line  or  blur,  due  to  summa- 
tion and  irradiation  of  sensations  from  the  pressure  spots. 

(7)  Variation :  work  with  larger  or  with  smaller  steps. 
Modification  :  reduce  your  steps  to  the  smallest  size  possible 
when  you  approach  the  region  of  change. 

(8)  Work  crosswise  on  the  arm,  because  (i)  you  will  then 
get  the  effect  of  visualisation,  and  (2)  the  pressure  spots  are 
themselves  more  thickly  distributed  transversely  than  they  are 
longitudinally :  A.  Goldscheider,  Neue  Thatsachen  iiber  die 
Hautsinnesnerven,  Arch.  f.  [Anat.  u.]  Physiol.,  Suppl.  Bd.,  1885, 
100;  cf.  Tawney,  Philos.  Studien,  xiii.,  170;  Judd,  ibid.y  xii.,  425. 
Work  upon  forehead,  tip  of  forefinger,  ball  of  thumb. 

(9)  Since  practice  would  aid  discrimination,  the  distance- 
values  of  the  two  points  of  change  would  both  be  rendered 
smaller.  The  dotted  line  of  the  Fig.  would  be  shifted  down- 
wards, parallel  with  itself.  —  In  the  single  experiment,  practice 
will  affect  the  \  more  than  the  \  series.  The  divergence  of 
the  dotted  line  from  the  horizontal  will  therefore  be  increased. 

(10)  To  avoid  complication  by  pain  and  temperature  sen- 
sations. 

(11)  Because  it  is  always  best  to  start  out  with  something 
that  is  quite  clear  and  easy,  and  to  work  from  that  towards  the 
obscure  and  difficult.  Since  O  knows  that  in  all  cases  there  are 
two  points  set  down  upon  the  skin,  he  is  likely  to  be  puzzled  if 
you  begin  with  a  two-point  impression  which  is  perceived  only 
as  one  point.  —  If  the  experiment  is  repeated,  and  practice  is 
gained,  the  series  should  be  alternated  ;  the  first  experiment 
\  \ ,  the  second  \  \ ,  the  third  \  \  again,  etc. 

After  determinations  have  been  made  in  the  transverse  direc- 
tion of  the  arm,  ask  O  and  E  why  they  were  directed  to  begin 
with  experiments  on  the  longitudinal  axis.  The  reason  is  that 
the  arm  taken  lengthwise  localises  more  roughly  than  the  arm 
taken  crosswise ;  and,  when  you  are  beginning  a  line  of  work,  it 
is  better  to  operate  with  the  rougher  of  two  available  machines. 
Your  own  mistakes  will  be  liable  to  do  less  harm. 


§  55-   Discrimination  of  Two  Points  381 

Related  Experiments,  (i)  The  Paradoxical  Localisation 
Experiment,  —  It  not  infrequently  happens  that  single  impressions 
give  rise  to  double  perceptions.  The  pressure  of  one  limb  of 
the  compasses,  f>.,  may  be  perceived  as  that  of  two  distinct 
points.  Give  irregularly  alternating  series  of  two-pressures  and 
one-pressure.  Note :  ( 1 )  the  influence  of  expectation  on  the 
number  of  wrong  double  perceptions  in  a  given  series  ;  (2)  that 
oi  fatigue ;  (3)  that  of  the  separation  of  the  compass  points  in 
the  experiments  in  which  two  points  are  really  set  down.  Notice 
also  (4)  the  distance  at  which  the  supposed  second  pressure 
seems  to  lie  from  the  given  single  pressure;  (5)  its  direction; 
and  (6)  its  character  (intensity,  extent,  duration)  as  compared 
with  that  of  the  given  pressure. 

You  will  find  that  expectation  and  fatigue  increase  the  number 
of  double  perceptions ;  that  wide  separation  in  the  alternate 
experiments  decreases  it ;  and  that  the  character  of  the  supposed 
second  point  varies.  Sometimes  the  real  and  supposed  points 
are  connected  in  introspection  by  a  line  of  pressure.  —  The  con- 
ditions of  the  second  perception  are  probably  physiological,  not 
psychological,  though  the  frequency  and  insistency  of  it  are 
modified  by  ^s  frame  of  mind. 

Henri,  61-^  and  references ;  esp.  Tawney,  Philos.  Studien,  xiii.,  197, 220 ; 
H.  Nichols,  Our  Notions  of  Number  and  Space,  1894,  161. 

(2)  The  Localisation  Pattern,  —  Make  some  rough  trials  with 
the  compasses  on  the  volar  side  of  the  upper  arm,  just  above  the 
elbow-crease,  and  in  the  transverse  direction.  Give  the  points 
a  separation  which  is  a  little  less  than  that  required  for  the 
arousal  of  two  perceptions,  and  draw  the  compasses  slowly  and 
steadily  down  the  arm  to  the  tips  of  the  second  and  third  fingers. 
Mark  the  resulting  series  of  perceptions  upon  an  outline  map  of 
the  arm,  and  (for  the  sake  of  comparison)  rule  on  the  map  in 
dotted  lines  two  parallels,  corresponding  to  the  track  of  the 
compass  points.  The  perception-figure  will  shrink  to  a  single 
line  on  parts  of  small  discriminating  power,  and  widen  out  into 
loops  on  the  regions  of  greater  discrimination. 

Perform  the  same  experiment  on  the  face.  Start  upon  the 
cheek-bone,  just  below  the  lobe  of  the  ear,  and  draw  the  com- 


382 


Tactual  Space  Perception 


Fig.  ioi. 


passes  transversely,  so  that  the  points  pass  above  and  below 
the  red  portions  of  the  lips.  Mark  the  resulting  series  of 
perceptions  on  a  map. 

E.  H.  Weber,  Ueb.  d.  Raumsinn,  etc.,  93 ;  Henri,  58  f. ;  Sanford,  Course, 
4,  exp.  7  c ;  Judd,  456  f. 

Instruments. — There  are  many  forms  of  aesthesiometer, 
which  we  shall  describe  in  vol.  ii.  Fig.  loi  shows  H.  Gries- 
bach's    dynamometrical    aesthesiometer    (Brandli,    $17).      This 

instrument  is  held  by  the 

thumb  and  the  first  and 

second  fingers  of  £"'s  right 

hand.     It  has  a  mm.  scale 

and  nonius.      The  points 

(of  which  there  are  four, 

—  two   rounded  and  two 

pointed)      push      against 

coiled     springs,     and      a 

scale-pointer  indicates  the  amount  of  pressure  exerted.     The 

points  are  of  metal.      This  is  a  disadvantage,  as  it  introduces 

the  temperature  error.     Pfluger's  Arch.,  Ixviii.,  1897,  65. 

Note  that  (as  the  author  found  in  1892,  and  as  Tawney  has  also  discovered  : 
Philos.  Studien,  xiii.,  168)  equality  of  objective  pressure-intensities  by  no 
means  guarantees  equality  of  subjective  pressures.  The  compass  points  may 
be  'pressing  equally'  while  the  two  sensations  aroused  are  markedly  different  in 
intensity.  The  important  thing  is  to  have  the  two  pressure  sensations  clear  and 
distinct  (Tawney,  168  f. ;  F.  B.  Dresslar,  Amer.  Journ.  of  Psych.,  vi.,  1894, 331). 

Literature.  — The  experimental  literature  begins  with  E.  H. 
Weber  (Annotationes  anat.  et  physiol.,  1834,  44).  The  Table 
of  values  in  the  article  on  Tastsinn  und  Gemeingefiihl  (Wagner's 
Handworterbuch  d.  Physiol.,  iii.,  2,  1846,  539)  has  often  been 
quoted  in  textbooks  of  psychology.  On  the  method  of  the  text 
(a  form  of  Weber's  *  First  Method'),  see  Kiilpe,  Outlines,  55  f.; 
Henri,  Raumwahrnehmungen,  12;  Tawney,  Philos.  Stud.,  xiii., 
173.  For  a  general  account  of  work  done  upon  the  '  Raumsinn 
d.  Haut,'  cf.  Henri,  5  ff. 

On  visualisation,  see  M.  F.  Washburn,  Philos.  Studien,  xi., 
1895,  190;  on  the  method  of  successive  stimulation,  C.  H.  Judd, 


§  56.   AristotUs  Exptrimmt  383 

Und.^  xil,  1896,  415;  on  linear  stimulation,  Judd,  413,  431; 
Goldschcider.  Arch,  f.  [Anat.  u.]  Physiol.,  1885,  Suppl.  Bd.,  84, 
95  ;  C.  S.  Parrish,  Aracr.  Journ.  of  Psych.,  vi.,  1895,  520. 


SXPERIMSNT  XXXV 

{  56.  LooHtation  with  Changed  Position  of  Parts  Stimulated. 
Cautions  not  noted  in  tfu  Text.  —  It  is  very  important,  for  the 
success  of  this  experiment,  that  all  the  directions  should  be 
carefully  carried  out.  The  ink-dots  mentioned  on  p.  191  of  the 
text  should  be  placed  on  the  R  side  of  the  second  and  the  U 
side  of  the  third  finger,  and  should  always  touch  when  the  fin- 
gers are  crossed.  In  the  *  normal '  position  of  the  fingers,  the 
U  side  of  the  second  finger  is  apposed  to  the  R  side  of  the 
third,  along  the  whole  length  of  the  latter.  The  student  must 
plainly  understand  that  two  impressions  constitute  a  single  ex- 
periment in  series  ( i ),  and  that  only  one  impression  is  required 
in  series  (2).  Be  very  careful  that  the  impressions  last  for  at 
least  I  sec,  and  are  not  of  the  nature  of  dabs  or  taps  upon  the 
skin.  The  crossing  and  uncrossing  of  the  fingers  should  be 
done  in  a  business-like  and  matter-of-fact  way,  so  that  C?*s  atten- 
tion is  not  particularly  called  to  the  proceeding.  E  should  han- 
dle (7's  fingers  as  little  as  is  compatible  with  avoidance  of  the 
fatigue  which  naturally  results  in  time  from  the  strain  of  the 
crossed  position.  The  *  crossed  *  series  should  directly  follow 
the  *  normal  *  series  in  each  of  the  three  cases.  The  hand  experi- 
mented on  must  lie  upon  the  table  as  flat  as  it  comfortably 
can;  the  upward  bend  of  the  finger-tips,  the  'give'  when  the 
compass  points  are  set  down,  must  be  reduced  as  far  as  possible. 
The  compasses  must  be  held  vertically,  and  not  approach  the 
skin  obliquely. 

Results.  —  The  results  are  as  follows.  In  Aristotle's  ex- 
periment, one  object  is  perceived  as  two.  In  the  normal  dis- 
crimination series,  the  20  mm.  separation  is  the  clearest ;  in  the 
crossed  series,  the  reverse  obtains.  A  similar  result,  though  of 
less  pronounced  a  kind,  is  gained  with  the  two  distance  series. 
The  estimated  distances  are  fairly  correct ;  correct  in  the  normal 
series,  correct  after  reversal  in  the  crossed  series.     The  direc- 


384  Tactual  Space  Perception 

tions  are  rightly  given  in  the  normal  localisation  series,  and  are 
exactly  reversed  in  the  crossed-finger  series. 

Questions.  —  (i)  In  most  cases,  O  is  sure  of  his  results: 
surprisingly  sure,  when  the  character  of  these  results  is  con- 
sidered. Uncertainty  may  arise  from  lack  of  practice,  or  from 
similarity  of  stimuli  (thus  the  20  and  12  mm.  separations  may 
occasionally  be  only  doubtfully  distinguished).  A  moderate  de- 
gree of  uncertainty,  varying  with  individuals,  may  attach  to  the 
estimations  of  series  (2) :  the  results  of  this  series  are,  as  a  rule, 
less  satisfactory  in  the  case  of  beginners  than  are  those  of  series 
(i)and(3> 

(2)  When  we  try  to  account  for  the  results,  we  have  to  note 
first  of  all  what  are  the  psychological  factors  involved.  These 
seem  to  be  three  in  number.  We  have  {a)  the  *  local  signs  '  of 
the  two  skin  areas  (see  Exp.  XXXIII.).  These  are  probably 
visual.  We  have  {b)  the  reinforcement  of  the  local  signs  by  our 
recent  visual  experiences.  In  other  words,  we  have  a  number 
of  visual  memories,  more  or  less  fresh,  which  tell  us  that  in 
everyday  life  the  two  skin  areas  upon  which  we  are  experiment- 
ing are  not  touched  except  by  two  different  objects.  And  we 
have  {c\  making  against  these  two  factors,  our  present  know- 
ledge, visual  and  tactual,  of  the  position  of  the  fingers.  Just  as 
present  knowledge,  in  Aristotle's  experiment,  may  counteract 
the  local-sign  evidence  from  the  fingers,  so  might  we  expect  that 
in  these  later  series  of  experiments  our  knowledge  of  finger- 
crossing  would  counteract  the  reversal  of  the  local  signs  and 
lead  to  the  construction  of  new  'right*  and  'left,'  and  of  a  new 
scale  of  distances.  ^ 

It  is  evident  from  the  results,  however,  that  factors  {a)  and 
{b)  are  (with  occasional  exceptions  in  the  distance  experiments) 
fully  able  to  outweigh  factor  {c).  The  old  visual-tactual  rela- 
tions persist  in  the  new  position  of  the  fingers;  an  objective 
*  left '  in  this  position  is  taken  to  be  *  right,'  because  it  would  be 
'right'  in  the  normal  position;  an  objective  Mong'  is  taken  to 
be  *  short,'  because  it  would  be  '  short '  in  the  normal  position ; 
etc.  The  general  explanation  asked  for  is,  then,  that,  no  mat- 
ter how  the  normal  relation  of  the  two  stimulated  surfaces  is 
changed,  there  is  constancy  of  tactual  localisation. 


$55-   Localisation  with  Changed  Position  385 

(3)  Because  the  forefinger  has  no  finger  apposed  to  it  on  its  R 
:de,  and  is  thus  differentiated  from  the  second  and  third  fingers. 

Nevertheless,  the  results  gained  can  be  verified  (although,  per- 
haps, not  quite  so  easily  as  they  were  gained)  with  the  fore  and 
middle,  or  third  and  fourth  fingers.  — The  second  is  the  longer 
finger. 

(4)  Just  the  same  results  arc  obtained.  The  only  change  in 
the  conditions  of  the  experiments  is  that  (7's  present  visual  and 

ictual  knowledge  of  the  position  of  the  fingers  (dorsal  side  up)  is 
:u)t  identical  with  their  position  on  the  maps  (volar  side  up);  and 
this  change  is  not  important  enough  to  confuse  his  localisations. 

(5)  We  are  constantly  manipulating  objects  with  our  fingers 
in  our  daily  life,  and  so  come  to  have  an  accurate  visual  idea  of 
the  width  of  these  phalanges.  This  visual  idea  is  easily  trans- 
lated into  the  visual  pencil-line  that  the  experiment  calls  for. 

(6)  Experiments  with  other  fingers  have  been  mentioned  above. 
The  right  hand  might  be  worked  on.     Bring  together  the  tip  of 

le  nose  and  the  upper  lip,  or  lay  the  lobe  of  the  ear  against  the 
head,  and  touch  the  two  apposed  surfaces  lightly  with  a  pencil 
or  the  whalebone ;  you  get  the  perception  of  two  objects.  Draw 
the  two  lips  apart  sideways,  the  one  to  the  left  and  the  other  to 

he  right.  Apply  the  compass  points  vertically,  the  one  to  the 
upper  and  the  other  to  the  lower  lip.  The  two  impressions 
*?eem  to  lie  diagonally,  and  in  an  opposite  direction  to  that  in 

vhich  the  lips  are  drawn. 

(7)  A  visual  memory-image  of  the  lines  drawn  in  previous  ex- 
periments would  form  part  of  O's  consciousness  at  the  moment 
that  the  new  impression  was  given.  The  line  next  drawn  would, 
therefore,  be  the  line  associated  not  to  this  tactual  perception 
alone,  but  to  the  tactual  perception  plus  the  memory-images. 

On  suggestion  in  general  see  J.  M.  Baldwin,  Mental  Development  (Methods 
and  Processes),  1895, 104  E,  with  references;  Wundt,  Hypnotismus  u.  Sugges- 
tion, Phtlos.  Studien,  viii.,  1892,  i ;  Lipps,  Suggestion  u.  Hypnose,  eine  psych. 
Untersuchung,  1895  (Sitzungsber.  d.  p.-  p.  u.  d.  hist.  CI.  d.  k.  bayer.  Akad. 
d.  Wiss.,  ii^  1897,  391)  ;  Pillsbury,  Amer.  Journ.  of  Psych.,  viii.,  315  ;  W.  C. 
Bagley,  AftrV/.,  xU.,  1900,  80;  A.  Binet,  L'Ann^e  psych.,  v.,  1899,  82. 

Related  Experiments.  —  In  the  two  experiments  now  to  be 
described,  local  sign  and  present  visual  knowledge  are  set  more 

2C 


386  Tactual  Space  Perception 

nearly  upon  an  equality  than  they  have  been  in  the  previous  ex- 
perimental series.  The  second  experiment,  moreover,  allows 
one,  with  practice,  to  dissociate  the  two  factors  entirely. 

(i)  Extend  the  two  arms,  turning  the  volar  surfaces  of  the 
hand  outwards.  Lay  the  hands  together,  right  over  left,  appos- 
ing the  volar  surfaces.  Link  the  fingers  of  the  two  hands. 
Bend  the  elbows,  and  bring  the  hands  up,  opposite  the  chest, 
fingers  upwards.  As  you  look  down  on  the  hands,  the  fingers 
of  the  right  hand  extend  from  left  to  right,  those  of  the  left  from 
right  to  left.  E  now  points  to  a  finger,  without  touching  it ; 
and  you  try  to  move  it.  As  a  general  rule,  you  move  the  cor- 
responding finger  of  the  other  hand. 

Repeat  the  experiment,  allowing  E  to  touch  the  finger  which 
he  wishes  you  to  move.     What  happens.-*  —  Henri,  139. 

(2)  E  provides  a  sheet  of  paper,  upon  which  two  points  have 
been  marked  in  a  diagonal  direction  ;  a  screen  of  paper  or  card- 
board ;  a  pencil ;  and  a  mirror.  O  seats  himself  before  the  mir- 
ror, the  pencil  in  his  right  hand.  The  paper  is  laid  down  before 
the  mirror,  and  the  screen  so  arranged  that  O  cannot  see  the 
paper  directly,  though  he  can  see  its  reflexion.  The  point  of 
<9*s  pencil  is  set  by  E  upon  one  of  the  two  points,  and  O  en- 
deavours to  draw  a  straight  line  from  that  to  the  other  point, 
guiding  his  movement  by  its  reflexion  in  the  mirror.  Individual 
differences  are  large:  usually,  however,  O  finds  the  task  diffi- 
cult, confusing  up  with  down  and  right  with  left.  Practice  re- 
moves the  difficulty. —  Henri,  139  f. 

Literature.  —  Aristotle's  references  to  the  illusion  of  duality 
are  to  be  found  in  the  Ile/jl  kwirvrnv,  ch.  2,  460,  and  in  the 
Metaphysics,  iii.,  ch.  6,  loi  i  and  x.,  ch.  6,  1063.  The  present 
Experiment  is  based  upon  Henri's  investigation  :  Raumwahr- 
nehmungen,  69  ff.,  136  ff.  Cf.  also  J.  Czermak,  Physiol.  Studien, 
ii.,  1855,  91  ff. ;  G.  C.  Robertson,  Mind,  O.  S.,  i.,  1876,  145  ;  W. 
H.  R.  Rivers,  Mind,  N.  S.,  iii.,  1894,  583. 

On  the  value  of  Aristotle's  experiment  in  systematic  regard, 
see  Henri,  169,  192,  195,  208,  212. 


CHAPTER    XII 
Ideational  Type  and  the  Association  op  Ideas 

XXZVI 


§  57.  Ideational  Tjrpei.  —  The  author  has  chosen  the  phrase 
•  ideational  types  *  or  *  types  of  idea  *  —  in  accordance  with  the 
historical  usage  of  English  psychology  —  to  denote  what  are 
more  generally  termed  'memory  types,*  'speech  types,'  'types  of 
imagery/  The  psychology  of  these  types  begins  with  the  inde- 
pendent work  of  G.  T.  Fechner,  F.  Galton  and  J.  M.  Charcot. 

Fechner  (EUem.  d.  Psychophysik,  ii.,  469  ff. :  On  the  Interrelation  of 
Memor)'  Images  and  After-images)  publishes  introspective  accounts  of  the 
visual  imagery  of  several  well-known  persons,  and  gives  a  very  elaborate  com- 
parison of  his  own  memor)'-images  and  after-images.  The  programme  which 
he  drew  up  for  further  work  was  carried  out,  with  curious  exactness,  by  Fran- 
ds  Galton  (Inquiries  into  Human  Faculty,  1883,  83  fT. ;  cf.  articles  in  Mind 
and  The  Fortnightly  Review  for  1880).  Charcot  came  to  the  question  from 
the  pathological  side  (see  Binet,  The  Psychology  of  Reasoning  [1886],  trs. 
1899,  13;  Charcot,  Lemons  sur  les  maladies  du  syst^me  nerveux,  Oeuvres 
completes,  1886-1890,  t.  iii.  [trs.  by  S.  Freud,  Neuc  Vorlesungen  lib.  d. 
Krankheiten  d.  Ner\'ensystems,  1886]). 

The  best  general  account  in  English  is  that  of  James :  Principles,  ii.,  50  fT. 
Sec  also  L.  W.  Stem,  Ueber  Psychologie  d.  indiv.  Differenzen,  1900,  47  ff. 
(bibliography,  138  f.) ;  W.  Lay,  Psych.  Rev.  Mon.  Suppl.  7,  1898;  H. 
Taine,  De  I'intelligence,  i.,  ed.  of  1883,  76  flf. ;  T.  Ribot,  Les  maladies  de  la 
memoire,  ed.  of  1891,  106  ff.;  J.  M .  Baldwin,  Mental  Devel.  in  the  Child  and 
the  RacCt  1895  (1899),  431  if.  and  references;  and  the  author's  Outline  of 
Psych.,  285  ff.,  293 ;  Primer,  123  ff. 

The  psychological  questionary  seems  to  have  originated  with 
Galton.  The  method  has,  of  late  years,  been  widely  used  by 
G.  S.  Hall  and  his  pupils  at  Clark  University  (see  recent  vols. 
of  the  Amer.  Joum.  of  Psych.). 

Question  ( I ).  —  The  requirements  are  given  by  Galton  (84) 
as  follows,     (a)  The  questions  must  be  such  as  will  be  quickly 

387 


388  Ideational  Type  and  Association  of  Idea 

and  correctly  understood,  (b)  They  must  admit  of  easy  reply, 
(r)  They  must  cover  the  ground  of  enquiry,  {d)  They  must 
"tempt  the  correspondents  to  write  freely  in  fuller  expla- 
nation of  their  replies,  and  on  cognate  topics  as  well." 
"  These  separate  letters,"  says  Galton,  "  have  proved  more 
instructive  and  interesting  by  far  than  the  replies  to  the  set 
questions." 

It  is  plain  that  the  arawing-up  of  a  questionary  is  no  light 
task.  The  questioner  must,  in  the  first  place,  know  the  ground 
that  he  desires  to  cover.  He  must,  secondly,  be  a  master  in  the 
art  of  questioning  itself.  And,  thirdly,  he  is  called  upon  to 
exercise  sound  judgment  in  the  acceptance  or  rejection  of  indi- 
vidual replies.  What,  now,  can  the  questionary  accomplish } 
What  does  it  do  that  could  not  be  done  by  the  personal  ques- 
tioning of  a  few  individuals  } 

In  the  hands  of  a  capable  enquirer,  it  can  accomplish  three 
things,  (a)  It  can  serve  to  establish  a  norm.  If  the  answer 
to  a  given  question  is,  in  a  very  large  number  of  cases,  essen- 
tially the  same,  we  can  accept  it  as  an  average  or  normal  account 
of  the  phenomena  under  investigation.  The  collective  result 
commands  a  higher  measure  of  belief  than  the  single  result, 
because  it  is  not  likely  that  50  or  loo  independent  observers,  all 
of  whom  are  liable  to  error,  will  all  be  liable  in  extreme  degree 
to  the  same  error,  {b)  It  can  give  a  fuller  characterisation  of 
the  phenomena  than  can  the  single  description.  Suppose  that 
a  number  of  persons  are  reporting  the  same  occurrence,  and 
that  there  is  no  contradiction  between  report  and  report,  but 
that  there  are  differences  of  detail,  —  one  report  emphasising 
one  of  the  minor  features  of  the  whole,  and  another  another. 
We  get  from  a  combination  of  all  the  reports  a  fuller  and  more 
accurate  picture  than  we  could  get  from  any  one  taken  singly  ; 
the  separate  accounts  not  only  reinforce  but  also  supplement  one 
another,  {c)  It  can  bring  out  individual  differences.  Suppose 
that,  while  the  majority  of  the  answers  are  in  essential  agree- 
ment, there  are  a  certain  number  —  returned  by  persons  of  simi- 
lar education  and  equal  trustworthiness  —  that  agree  among 
themselves  but  differ  radically  from  the  rest.  We  are  justified 
in  accepting  this  smaller  group,  at  least  provisionally,  as  evidence 


§  57-    T^h^  Quest ionary  389 

of  the  existence  of  a  second  '  type '  or  '  norm  '  and  in  making  it 
the  starting-point  of  further  investigation. 

All  three  results  were  accomplished  by  Galton's  questions  upon  Visualis- 
ing and  Other  Allied  Faculties  (Inquiries,  378  ff.)«  which  may  be  said,  as 
James  remarks,  **  to  have  made  an  era  in  descriptive  psychology."  But  we 
must  not  forget  the  limitations  of  the  questionar)'.  Galtun  writes :  *Mt  is  a 
much  easier  matter  than  1  had  anticipated  to  obtain  trustworthy  replies  to 
psjrchological  questions.  Many  persons  .  .  .  take  pleasure  in  introspection, 
.-ind  strive  their  very  best  to  explain  their  mental  processes.  1  think  that  a 
delight  in  self-dissection  must  be  a  strong  ingredient  in  the  pleasure  that 
many  are  said  to  take  in  confessing  themselves  to  priests  *^  (87).  And  James 
gives  us  the  same  idea  when,  after  declaring  that  '*  Fechner  was  gifted  with 
unusual  talent  for  subjective  obser\'ation,'^  he  refers  to  Fechner's  comparison 
of  memor)-i mages  and  after-images  as  "a  type  of  observation  which  any 
reader  with  sufficient  patience  may  repeat'*  (i.,  50  f.).  Such  statements  sug- 
gest that  introspective  exercises  may  be  paralleled,  as  a  form  of  polite  recrea- 
tion, with  the  word-puzzles  in  the  magazines,  and  that  the  circular  of  ques- 
tions is  a  ro>'al  road  to  the  atuinment  of  psychological  truth.  Nevertheless, 
Galton  asserts  that  *^  there  is  hardly  any  more  difficult  task  than  that  of  fram- 
ing'^  a  sacoessful  questionary  (84);  and  James  prints  his  own  introspective 
results  with  great  modesty  and  reserve  (65). 

There  is  here  a  real  contradiction,  but  a  contradiction  which  it  is  not  diffi- 
cxilt  to  resolve.  We  must  remember  that  the  questionary  can  never  transcend 
or  go  behind  the  introspections  of  the  individual  correspondents.  The  col- 
lective result  is  worthy  of  more  credence  than  the  individual  result,  but  it 
does  not  penetrate  more  deeply  than  this  into  the  structure  of  mind.  Stumpfs 
mass-tests  of  the  relative  unitariness  of  chords  serve  to  establish  the  scale  of 
fusion  degrees,  but  tell  us  nothing  of  tonal  analysis.  So  the  quest ionar)- 
retums  upon  visual  imagery  enable  us  to  plat  our  curves  of  distribution,  but 
tell  us  nothing  more  of  the  mechanics  of  visual  thinking.  We  put  point- 
blank  and  clear-cut  questions :  questions  which,  in  their  ideal  form,  demand 
no  more  than  a  *  yes '  or  a  *  no '  for  answer :  and  we  get  replies  upon  the  intro- 
spective level  of  the  average  educated  man.  This  level  is  low.  It  remains 
low,  even  when  the  introspections  are  directed  and  assisted  by  our  phrasing 
of  the  questions.  The  self-dissection  of  the  confessional  and  of  the  '  psycho- 
logical novel '  is,  therefore,  a  very  different  matter  from  the  introspection  of 
psychological  science ;  and  the  *  patient  reader '  will  have  but  small  success  if 
he  tr\',  without  practice  or  model,  to  match  the  analyses  of  Fechner  and 
James. 

Galton's  work  lay,  if  we  may  use  the  expression,  on  the  objective  side  of 
psydwlogy ;  and  this  fact  accounts  for  its  success.  The  ordinary  observer, 
untrained  in  psychological  method,  can  give  an  opinion  as  to  the  match  of  two 
colours  upon  the  colour  mixer,  while  he  is  wholly  unable  to  follow  the  course 
of  an  after-image.     Similarly,  the  ordinary  observer  can  tell  us  whether  his 


390  Ideational  Type  and  Association  of  Ideas 

mind  is  furnished  with  visual  ideas,  and  can  describe  some  of  the  uses  to 
which  he  puts  his  visual  furniture  in  everyday  life  (Galton,  95  f.),  though  he 
will  be  wholly  unable  to  unravel  the  part-processes  in  visual  recollection,  visual 
recognition,  visual  apperception,  etc. 

We  may  cite,  in  support  of  the  position  here  taken,  the  elaborate  mono- 
graph of  E.  D.  Starbuck,  on  The  Psychology  of  Religion ;  an  Empirical  Study 
of  the  Growth  of  Religious  Consciousness  (London,  1899).  ^^  '^^s  been 
pointed  out  by  a  reviewer  (J.  H.  Leuba,  Psych.  Rev.,  vii.,  1900,  515)  that 
phrases  like  *  a  vital  experience  of  spiritual  truth,' '  the  attainment  of  spiritual 
life,'  *a  spiritual  grasp,  a  new  insight,'  Uhe  higher  life  of  intelligence  and  in- 
sight,' *a  personal  hold  on  virtue,'  'a  first-hand  perception  of  right  and  wrong,* 
are  hardly  in  place  in  the  work  of  a  professional  psychologist.  Yet  they  fairly 
represent  the  introspective  depth  to  which  the  writer's  questionaries  have 
taken  him. 

However,  the  fault  lies  in  such  cases  not  with  the  method,  but  with  those 
who  overestimate  the  method.  On  this  score,  as  we  have  seen,  both  Galton 
and  James  are  to  be  held  guilty.  Let  us  now  enquire  into  the  scope  of  the 
questionary,  in  the  various  fields  of  psychological  research. 

The  questionary  does  excellent  psychological  service  («)  in  a 
field  of  observation  which  is,  in  strictness,  extra-psychological : 
that  of  expressive  bodily  movement.  Darwin  made  use  of  it  in 
getting  material  for  his  work  on  the  Expression  of  the  Emo- 
tions in  Man  and  Animals  (1872).  The  applicability  of  the 
method  in  this  sphere,  and  its  importance  for  animal,  infant 
and  ethnic  psychology,  are  obvious,  and  need  not  be  insisted  on. 
ib)  The  questionary  can  inform  us  of  the  variation  of  a  given 
mental  fact  with  variation  of  age,  sex,  race,  occupation,  etc.  It 
thus  throws  light  upon  what  we  may  call  the  'natural  history' 
of  mind.  Cf.  Galton 's  statement  that  "the  power  of  visualising 
is  higher  in  the  female  sex  than  in  the  male  "  (99).  And  {c)  the 
method  is  of  value  in  purely  descriptive  psychology,  where 
the  introspection  required  is  of  a  simple  and  *  massive '  kind. 
Here  belong  the  major  part  of  Galton's  enquiries,  and  such  an 
enquiry  into  the  types  of  ethical  and  religious  sentiment  as  is 
suggested  in  the  author's  Outline,  334  f. 

We  are  ourselves  employing  the  method  under  extremely  favourable  condi- 
tions, since  the  0\  to  whom  the  questions  are  submitted  have  already  had 
training  in  introspection.  Under  such  circumstances,  the  individual  results 
have  a  higher  value  than  usually  attaches  to  the  single  sheet  of  questionary- 
returns. 


$  57-    T'Ar  Questionary  391 

QtusHonary  upon  Ideational  Type,  —  This  questionary  includes 
practically  all  of  Galton*s  questions*  and  is  also  indebted  for  spe- 
cial points  to  a  VVellesley  questionary  upon  Memory  Type  and 
to  the  Psychol.  Schulversuche  of  Hofler  and  Witasek,  14  f.  (cube 
and  octahedron).  It  is  in  so  far  an  improvement  upon  Gal  ton's 
paper  as  that  the  questions  upon  auditory,  tactual,  etc.,  imagery 
are  drawn  from  definite  situations,  and  not  made  a  mere  appendix 
to  the  \isual  portion  of  the  enquiry.  For  somewhat  similar  lists, 
see  Lay,  21 ;  R.  H.  Stetson,  Psych.  Rev.,  iii.,  1896,  402. 

The  questionary  is  still  most  complete  and  satisfactory  upon 
the  visual  side.  "  A  statistical  enquiry  upon  a  large  scale,  into 
the  variations  of  acoustic,  tactile,  and  motor  imagination,  would 
probably  bear  less  fruit  than  Galton's  enquiry  into  visual  images  *' 
(James,  ii.,  65).  The  reason  is,  simply,  that  the  demands  upon 
introspection  are  greater. 

On  the  auditory  type,  and  questions  pertaining  to  it,  see  B. 
Bourdon,  Ber.  iiber  d.  3  internat.  Congress  f.  Psychol.,  1897, 
240  f. ;  Stem,  53  ;  Stumpf,  Tonps.,  i.,  279  ff. ;  A.  Binet,  Psy- 
chologie  des  grands  calculateurs  et  joueurs  d'^checs,  1894,  24  ff. 

On  the  tactual  or  'motor'  type  and  its  interrelations,  see 
Strieker,  Studien  iiber  d.  Sprachvorstellungen,  1880;  Studien 
iiber  d.  Bewegungsvorstellungen,  1882;  Studien  iiber  d.  Asso- 
ciation d.  Vorstellungen,  1883;  Rev.  philos.,  xviii.i  1884,  685; 
Stumpf,  Tonps.,  L,  153  ff. ;  F.  Paulhan,  Rev.  philos.,  xvi.,  1883, 
405  ;  xix,  1885,  118;  xxi.,  1886,  26;  R.  Dodge,  Die  motorischen 
Wort  vorstellungen,  Halle,  1896. 

Results.  —  Each  student  enters  his  own  questionary-retums 
in  his  note-book,  and  then  hands  the  sheets  to  the  Instructor 
for  statistical  working-over.  The  returns  from  the  class  should 
be  arranged  according  to  Galton's  classification  (Human  Faculty, 
49  ff.,  93>  The  following  is  Galton's  specimen  Table.  Similar 
Tables  are  to  be  made  out  by  the  Instructor  (or  by  some  student 
deputed  by  him  to  the  task)  in  the  other  sense-departments. 
All  should  be  recorded  in  the  note-books,  so  that  every  student 
knows  his  place  in  the  various  scales. 

It  is  well 'to  save  the  answer-sheets,  from  year  to  year,  and  to  give  them  to 
the  ttudento  for  working-over,  after  the  questionary  itself  has  been  answered. 
Practice  b  thus  gained  in  the  manipulation  of  sUtistical  results. 


392  Ideational  Type  and  Association  of  Ideas 

Galton's  Table  for  Vividness  of  Mental  Imagery. 


Highest.  —  Brilliant,  distinct,  never  blotchy. 


First  Suboctile.  —  The  image  once  seen  is  perfectly  clear  and  bright. 

First  Octile.  —  I  can  see  my  breakfast-table  or  any  equally  familiar  thing  with 
my  mind's  eye  quite  as  well  in  all  particulars  as  I  can  do  if  the  reality  is  before  me. 

First  Quartile.  —  Fairly  clear ;  illumination  of  actual  scene  is  fairly  repre- 
sented. Well  defined.  Parts  do  not  obtrude  themselves,  but  attention  has 
to  be  directed  to  different  points  in  succession  to  call  up  the  whole. 

Middlemost.  —  Fairly  clear.  Brightness  probably  at  least  from  one-half  to 
two-thirds  of  the  original.  Definition  varies  very  much,  one  or  two  objects 
being  much  more  distinct  than  the  others,  but  the  latter  come  out  clearly  if 
attention  be  paid  to  them. 

Last  Quartile.  —  Dim,  certainly  not  comparable  to  the  actual  scene.  I 
have  to  think  separately  of  the  several  things  on  the  table  to  bring  them 
clearly  before  the  mind's  eye,  and  when  I  think  of  some  things  the  others 
fade  away  in  confusion. 

Last  Octile.  —  Dim  and  not  comparable  in  brightness  to  the  real  scene. 
Badly  defined  with  blotches  of  light ;  very  incomplete ;  very  little  of  one 
object  is  seen  at  one  time. 

Last  Suboctile.  —  I  am  very  rarely  able  to  recall  any  object  whatever  with 
any  sort  of  distinctness.  Very  occasionally  an  object  or  image  will  recall 
itself,  but  even  then  it  is  more  like  a  generalised  image  than  an  individual 
one.     I  seem  to  be  almost  destitute  of  visualising  power  as  under  control. 


Lowest.  —  My  powers  are  zero.  To  my  consciousness  there  is  almost  no 
association  of  memory  with  objective  visual  impressions.  I  recollect  the  table, 
but  do  not  see  it. 

The  Instructor  should  be  on  the  look-out  for  special  remarks 
bearing  upon  peculiarities  of  mental  constitution.  Nearly  every 
paper  will  contain  some  such  observations.  Here  are  two,  from 
the  first  two  sheets  of  the  author's  pile  of  class  returns. 

(i)  If  I  am  tired,  I  generally  find  that  mathematical  work  is  made  easier  if 
I  visualise.  I  always  feel  as  if  I  am  working  more  slowly  when  I  visualise, 
but  it  frequently  makes  things  clearer. 

(2)  I  always  think  of  numerals  as  printed  in  rather  heavy-faced  type.  I 
almost  always  have  images  without  colour.  In  fact  I  always  dream  in  black, 
white  and  grey. 

If  a  student  is  noticeably  weak  in  one  or  other  of  the  partial 
memories,  he  may  be  advised  to  practise  it,  with  a  view  to  im- 
provement.    See  Galton,  105  ff.  ;  James,  ii.,  58,  60;  E.  B.  Tal- 


§  57     Types  of  Idea  393 

hot,  Amcr.  Joum.  of  Psych.,  viii.,  1897,  414;  Cohn,  Ber.  lib.  d. 
5  internat.  Congress  fur  Psych.,  1897,  458  ;  Stetson,  loccit.,  408. 

As  to  the  relative  frequency  of  the  various  types  of  idea,  there 
seems  to  be  no  doubt  that  the  great  majority  of  students  are 
predominantly  visual  {cf,  A.  C.  Armstrong,  Psych.  Rev.,  i., 
1894,  505)^  Galton  says  (87)  that  "scientific  men,  as  a  class, 
have  feeble  powers  of  visual  representation."  It  must  be  re- 
membered, however,  that  the  men  here  referred  to  are  men  of 
standing  and  reputation,  —  men,  therefore,  who  have  lived  long 
enough  to  outgrow  their  visualisation.  Unless  the  visualising 
jK)wers  are  kept  alive  by  occupation  {cf.  Hankel's  case  in  Fechner, 
ii.,  480,  487  i.\  there  is  a  tendency  in  'thinking*  minds  for  the 
visual  to  be  replaced  by  a  verbal-motor  imagery.  —  Cf,  Lay,  1 5  f. 

The  verbal-motor  type  stands,  in  the  author's  experience,  next 
in  order  of  frequency  to  the  visual.  How  common  this  type  is 
in  general  society,  or  in  the  less  educated  classes  of  the  com- 
munity, cannot  be  said.  It  is  probable,  however,  that  a  general 
enquiry,  if  it  could  be  carried  out,  would  reveal  a  very  large  pre- 
ponderance of  visualisation. 

The  auditory  type  is  rare,  except  in  the  form  of  verbal  audi- 
tory-motor. The  questionary  may  bring  home  to  the  student  his 
lack  of  purely  auditory  images,  and  so  serve  as  incentive  to  the 
study  of  music  :  a  result  devoutly  to  be  wished  {cf,  p.  52  above). 
See  Binet,  Psychology  of  Reasoning,  22  f. 

It  b  worth  noting  that  smell  images,  which  Wundt  declares  to  be  extremely 
nnoommon  (**  It  is  in  most  cases  illusion  when  you  think  that  you  can  recall 
the  scent  of  a  rose "" :  Human  and  Animal  Psych.,  286),  have  been  found  by  Dr. 
Gamble  to  be  of  6urly  frequent  occurrence.  "  Allowing  for  the  untrust worthi- 
ness of  my  introspective  retums,""  Dr.  Gamble  writes,  "  and  although  I  do  not 
have  smell  memorj-images  myself,  I  cannot  think  that  they  are  as  rare  as  you 
say.  Fully  half  of  our  65  subjects  insisted  that  they  had  them.  .  .  .  More- 
over, there  was  a  clear  tendency  in  the  limina  of  these  subjects  to  be  lower 
than  the  limina  of  the  other  subjects.  Which  fact  was  cause  and  which  effect 
I  do  not  know ;  but  the  coincidence  was  marked.""     Cf.  Lay,  37. 

On  the  *  organic,"  or  as  it  is  also  called  the  *  affective,"  memory  type,  see  T. 
Ribot«  The  Psychol,  of  the  Emotions,  trs.  1897, 140  ff. ;  Titchener,  Phil.  Rev., 
iv.,  1895,  65  ;  Outline,  292  ff. ;  Primer,  129  f. ;  Lay,  38  f. 

Question  (2). — There  are  several  methods  of  determining 
ideational  type,  and  of  attacking  the  problems  connected  with 


394  Ideational  Type  and  Association  of  Ideas 

it.  Those  with  which  the  author  is  acquainted  are  given  below. 
It  is  desirable  that  the  student,  besides  answering  the  question- 
ary,  should  work  by  one  or  other  of  the  experimental  methods 
here  outlined.  The  author  advises  that  the  various  methods  be 
distributed  to  various  pairs  of  students,  and  that  the  results  of 
the  whole  class  be  worked  over  by  the  Instructor,  so  that  a  gen- 
eral statement,  prepared  by  him,  may  be  copied  into  all  note- 
books. 

(i)  The  most  obvious,  and  perhaps  the  most  reliable,  method 
of  gaming  information  about  ideational  type  is  to  read  "mono- 
graphs, by  competent  observers,  about  their  own  peculiarities." 
We  have  material  of  this  kind  from  Fechner,  Stumpf,  Strieker, 
James  and  others.     See  Lay,  32,  36,  40;  Dodge,  op.  cit. 

(2)  The  Word  Method.  —  This  method,  like  the  questionary, 
can  be  employed  in  cases  where  there  has  been  no  previous 
training  in  introspection.     It  has  two  forms. 

{a)  Kraepelin' s  Method.  —  Require  O  to  write  out  a  list  (i)  of 
objects  that  are  characterised  by  their  colour  and  (ii)  of  objects 
that  are  characterised  by  their  sound.  Let  him  have  5  min.  for 
each  list.  —  E.  Kraepelin,  Psychol.  Arbeiten,  i.,  1895,  73;  G. 
Aschaffenburg,  ibid.,  i.,  255. 

(^)  Secor^s  Method.  —  A  series  of  (say,  20)  words  is  written 
or  printed  upon  slips  of  paper.  At  the  "  Now  !  "  O  glances  at  a 
word,  and  at  once  notes  down  (i)  the  nature  of  the  verbal  image 
(visual,  auditory,  articulatory)  and  (ii)  the  further  imagery  sug- 
gested by  the  word  as  seen. 

The  experiment  is  repeated  with  a  second  series  of  words, 
which  are  read,  not  shown,  to  O.  —  W.  B.  Secor,  Amen  Journ. 
of  Psych.,  xi.,  1900,  227  ff. 

The  words  must  be  carefully  selected.  The  following  are  the  results  of  an 
experiment.  The  visual-verbal  image  in  Series  i.,  and  the  auditory-verbal 
image  in  Series  ii.,  are  not  recorded. 

Series  I.  — Word  Seen  Series  II. — Word  Heard 

Driftwood V,  V  Summer  night     ...     V,  V-V 

IVaves V,  T  Picnic V,  V-V 

VioUt V,  V  Foghorn V,  A 

Brook A,  V  Landscape V 

Satt G,  V  Fire V 


§  57-    Types  of  Idea:  Methods 


395 


Ssms  I. -Won 

Sum 

SemskeU 

A,V,V 
V.V 

Rose 

V 
V 

WHsidewaik.    . 

V,M 

Rmlromd    .    .     . 

A,  O,  V 

Sprimgiimi 
imimity. 
Fog  . 

Dog  . 
Ltax*€S   . 

\\  V,  A 

\%v,v,o 

V,  V,  P,  T 
A.  V,  O 

Expamst 
Bng^day. 

V.  v,o 
.   v,o 

Fort 

.     V,  O,  A 

Here  V  =  visuai ;  i 

\  -  auditory ; 

SSMBt  II.  —  W<MU>  HbaKO 

BUdMrds      .     .     .     .  V,  V 

The  imormttg  wind  .    .  P,  A,  O 

GUmrimg  horsiskot    .    .  V,  V 

FbiU A 

ic«  woier V,  T 


Brass  band 
Horse    . 
Bees 
Robin 

Chimes  .     . 
Kerosene 
Gas  .     .     . 
State  roof  . 
Steam  whistte 
Inkstand    . 


A,V,V 

V 

V 

V 

A,V,0 

V 

V,V,0 

y 
\.v,  o 


P  =  pressure ;  O  =  organic ;  T  =  tempera* 
tore ;  G  =  gtistatory ;  M  =  motor ;  V-V  =  visual-verbal. 

If  we  sum  up  the  results,  giving  an  unit  to  every  word,  and  counting  all  the 
ideas  of  a  single  categor>'  as  one  (so  that  Driftwood  gives  *  one  visual  ^ ;  Bright 
dkf  gives  *  one-half  visual,  one-half  organic,^  etc),  we  obtain : 


ViSOAL  SnOBS 

Auditory  Sbribs 

V                   12^ 

64.0% 

V 

14.6 

73.0% 

A,  O          2.5 

12.5" 

A 

2.9 

14.5" 

T                 .8 

4.0" 

0 

1.4 

7.0" 

G,M            .5 

2.5" 

T 

•5 

2.5" 

P                  3 

1.5^ 

P 

•3 

1.5" 

It  is  clear,  even  from  so  brief  a  series  as  this,  that  O  is  predominantly  visual, 
and  that  auditory  and  organic  '  images '  follow  the  visual  at  a  very  long  inter- 
val.    It  is  noteworthy  that  there  is  not  a  single  A-V  image  in  Series  i. 

(3)    The  Questionary  or  Galtons  Method. 

^  We  may  assert,  without  fear  of  contradiction, '  says  KUIpe  (Outlines,  185), 
**  that  the  number  of  discriminable  qualities  of  centrally  excited  .sensations  in 
geneial  is  less  than  that  of  the  peripherally  excited  qualities.''  The  author  is 
not  convinced  by  KUlpe's  reasoning,  and  hopes  that  the  question  may  some 
day  be  put  to  the  test  of  experiment.  In  the  meantime,  it  has  been  suggested 
to  him  by  Dr.  Bentley  that  questions  which  require  an  accurate  discrimination 
between  similar  images  might  be  introduced,  with  good  result,  into  a  ques- 
tionary upon  ideational  type.     The  following  are  typical  distinctions : 

(tf)  The  dangs  of  locomotive,  door,  school,  church  and  dinner  bells.  The 
roar  of  wind,  water^dl,  distant  thunder,  distant  cannon. 

{b)  The  colours  pink,  carmine,  blood  red,  rose.  The  different  patterns  of 
wall  paper  In  a  well-known  house. 


396  Ideational  Type  and  Association  of  Ideas 

(<)  The  tastes  of  apple,  pear,  quince  (with  full  analysis). 
(//)  The  *  feels '  of  silk,  satin,  velvet,  plush,  as  the  finger  is  passed  over 
them. 

{e)  The  scent  of  geranium,  rose  wood,  cedar  wood,  sandal  wood. 
(/)  The  organic  complexes  in  weak,  strong,  slow  and  quick  anger. 

(4)  The  Method  of  Letter  Squares  or  Bincfs  Method.  —  This 
method  has  been  modified  and  extended,  in  the  Cornell  labora- 
tory, as  follows. 

Experiment,  Part  i.  Without  Direction.  —  Materials  :  4  let- 
ter squares,  4  blanks ;  4  series  of  9  letters  ;  4  irregular  figures. 
[The  letter  squares  are  cards  or  papers,  10  by  7.5  cm.,  divided 
into  12  squares  (2.5  x  2.5  cm.),  each  of  which  contains  a  letter. 
The  letters  are  consonants,  printed  in  gothic  type,  about  8  mm. 
in  height.  They  are  arranged  in  random  order ;  but  any  collo- 
cation that  might  serve  as  an  aid  to  memory  should  be  studi- 
ously avoided.  The  blanks  are  similar  cards,  ruled  in  squares 
without  the  letters.  The  letters  in  the  9-letter  series  are  also 
arranged  at  haphazard.  The  irregular  figures  are  simple  'non- 
sense diagrams,'  made  up  of  6  curved  or  straight  lines,  within  an 
area  of  about  20  by  15  cm.] 

{a)  O  sits  at  a  table,  upon  which  are  a  blank  square  and  a 
letter  square  turned  face  downwards.  At  the  "  Now  !  "  he  turns 
over  the  letter  square,  and  learns  the  letters.  After  10  sec,  at 
another  "Now!"  he  lays  down  the  letter  square,  and  counts 
aloud  I  to  20  for  20  sec.  At  a  third  signal,  he  proceeds  to  fill 
out  the  blank  square  from  memory.  Ten  sec.  are  allowed  for 
the  writing.  Then,  at  a  fourth  "  Now  !  "  O  writes  on  the  back 
of  the  blank  square  an  account  of  his  method  of  reproduction. 

Illustration :  letter  square  given :  Q  H  B  K       reproduced  :  Q  H  R  T 

Y  N  P  G  Y  N        V 

F  T  C  V  F  C        G 

Introspection  :  I  visualised  the  card,  and  the  third  column  was  blank.  Then 
I  said  over  the  letters  by  groups  of  three.  The  second  group  suggested  R  for 
the  third  column,  but  I  could  not  see  it  on  my  visualised  card. 

The  test  is  to  be  repeated  with  the  remaining  three  cards. 
The  results  may  then  be  evaluated,  on  an  arbitrary  scale,  as  fol- 
lows. All  letters  given  in  introspection  as  reproduced  by  a  pure 
memory  (V ;  A ;  M)  are  to  count  as  i  ;  all  letters  given  as  re- 


§  57-    TyP^^  of  Idta  :  Mithods  397 

produced  by  double  memories  (V  4.  A  ;  V  -f  M  ;  A  -f  M)  are  to 
count  \  to  each  partial  memory  concerned  ;  and  all  letters  repro- 
duced by  mixed  memory  (V  4-  A  +  M)  are  to  count  \  to  each 
partial  memory.  Under  these  rubrics,  a  rightly  placed  and 
rightly  remembered  letter  counts  as  i  ;  a  rightly  remembered 
but  misplaced  letter  counts  as  } ;  a  substituted  letter  counts  as 
\ ;  and  an  omitted  letter  counts,  of  course,  as  o. 

/Uustrmiiott :  square  given :  B  K  F   P         reproduced :  B  K   F  G 

DXTM  DXTM 

R  L  J    S  R        H  N 

Pint  two  horixonul  lines  V ;  last  line  A  +  M. 

Visoal :  correct,  7 ;  misplaced,  o ;  substituted,  i  (value   \) ;  omitted,  o. 

Total,  If. 

Auditor)'-motor :  correct,  i ;  misplaced, o ;  substituted  2  (value  \)  ;  omitted,  i. 
Total  auditor}',  ^ ;  motor,  ^. 

General  result :  —  ratio  V :  A :  M  =  29 : 3 : 3.    Total  memory  =  ||. 

(d)  £  takes  one  of  the  9-letter  series,  and  reads  it  to  O.  He 
must  read  evenly,  clearly  and  slowly,  —  giving  at  the  quickest 
not  more  than  2  letters  in  the  i  sec,  —  with  entire  avoidance  of 
rhythm.  At  the  end  of  the  series,  O  recalls  the  letters,  and  dic- 
tates them,  in  what  he  thinks  their  right  order,  to  E.  He  then 
describes  his  method  of  reproduction. 

The  test  is  to  be  repeated  with  the  remaining  three  series. 
The  results  are  worked  over  as  before. 

(c)  O  closes  his  eyes,  and  takes  a  pencil  in  his  hand.  E  lays 
one  of  the  drawings  upon  the  table,  and  guides  O's  hand  along 
its  outlines.  The  movement  must  be  slow  and  continuous,  and 
the  pencil  in  O's  hand  must  never  leave  the  paper.  When  the 
tracing  is  complete,  E  gives  O  a  blank  sheet  of  paper,  and  O 
reproduces  the  drawing  with  eyes  closed.  He  then  describes 
his  method  of  reproduction. 

E  estimates  the  accuracy  of  the  drawing  on  the  basis  of  60  ( 10 
units  for  each  of  the  6  lines).  The  test  is  repeated  with  the 
remaining  three  drawings. 

It  is  clear  that,  although  no  directions  as  to  mode  of  reproduction  are  here 
given,  the  first  test  encourages  a  visual,  the  second  an  auditory-motor,  and  the 
third  a  visual-motor  memory.  Rough  as  the  method  of  calculation  is,  it  is 
alike  for  all  Cs,  and  will  furnish  a  fsdr  sUtement  of  the  relative  availability  of 


398  Ideational  Type  and  Association  of  Ideas 

the  different  images.     The  statement  is  checked  and  refined  by  the  results 
of  the  following  experiment. 

Note  that  the  above  12  tests  are  not  to  be  taken  in  regular  sequence  (4 
squares,  4  series,  4  drawings),  but  to  be  intermixed  in  random  order.  Note 
also  that  the  method  of  evaluation  yields  a  structural  and  not  a  functional 
result.  In  the  second  illustration  under  («),  e.g.^  the  A  +  M  memory,  which 
functions  singly,  is  split  up  into  an  A  and  an  M. 

Experiment,  Part  ii.  With  Direction.  —  Materials:  6 
letter  squares,  6  letter  series,  4  drawings. 

(a)  O  learns  a  letter  square  by  vision  alone  (or  with  emphasis 
on  vision).  He  reproduces  by  writing  from  visual  images.  Two 
squares. 

O  learns  as  before,  but  reproduces  by  writing  from  auditory 
images.     Two  squares. 

O  learns  as  before,  but  reproduces  by  writing  (with  eyes 
closed)  from  motor  (articulatory  or  finger-movement)  images. 
Two  squares. 

{b)  O  learns  a  letter  series  by  hearing  alone  (or  with  emphasis 
on  hearing).  He  reproduces  by  dictating  from  auditory  images. 
Two  series. 

O  learns  as  before,  but  reproduces  by  writing  from  visual  im- 
ages.    Two  series. 

O  learns  as  before,  but  reproduces  by  writing  (with  eyes 
closed)  from  motor  (articulatory  or  finger-movement)  images. 
Two  series. 

{c)  O  learns  an  outline  by  movement  alone  (or  with  emphasis 
on  movement).  He  reproduces  by  drawing  from  movement 
images.     Two  drawings. 

O  learns  as  before,  but  reproduces  by  drawing  from  visual 
images.     Two  drawings. 

The  results  are  worked  out  as  before,  and  combined  with  those  of  the  pre- 
ceding tests  to  form  a  total  picture  of  O's  mental  furniture. 

Like  all  work  in  <  individual '  psychology,  this  experiment  demands  of  -£"  a 
certain  tact  and  interpretatory  insight.  One  may  say  to  a  psychologist  "  Re- 
produce by  articulatory  images,"  and  he  will  understand  the  requirement ;  but 
with  novices  one  must  use  a  more  concrete  and  suggestive  formula.  The 
following  list  of  phrases,  taken  from  the  introspective  records  of  a  number  of 
students,  may  be  of  assistance  to  the  Instructor. 

{a)  Pure  Visual  Memory.  —  Visualised  C.  Every  letter  was  seen.  B 
seemed  blacker  than  the  rest.     I  saw  the  whole  card.     Visual  image.     The 


§  57-    ^«  of  ItUa:  Methods  399 

letters  arranged  themselves  in  groups  of  two ;  the  image  of  the  second  was 
always  £gunter  than  the  picture  of  the  first. 

{b)  Fure  AudHory  Mtm&ry,  —  The  R  seemed  to  ring  through  my  head, 
rtters  came  by  sound ;  I  did  not  speak  them.  I  remembered  L  because  of 
N  sound,  which  I  like. 

(t-)  Pure  Mt4ar  Mitmory,  —  Remembered  by  the  feel  of  the  muscle.    Wrote 

in  a  mechanical  way;  nothing  there  but  the  writing ;  seemed  reflex.    Tried  to 

remember  the  way  the  muscles  of  my  hand  felt  when  I  traced  on  the  paper. 

he  long  upward  stretch  gave  a  sensation  in  the  fore>arm,  and  the  motor 

memory  was  quite  easy. 

{d)  Vismal-tmctdr  Mimory.  —  Looked  over  the  card :  remembered  G  be- 
cause it  started  the  group,  and  A  because  it  was  diagonally  across.  Drew 
from  a  visual  picture  of  mountain  range  and  bridge.  Movement  suggested  a 
occasin  flower,  which  I  visualised.  Thought  the  curves  must  be  like  the 
lines  of  a  capital  M.  I  said  the  first  two  letters  with  my  lips  as  I  read  them, 
and  afterwards  in  writing  moved  my  lips. 

{e)  AudHory-mator  Memory.  —  Heard  the  series  as  I  wrote  it ;  my  throat 
and  lips  moved  at  certain  letters.     Remembered  after  saying  over  the  first  line 

a  sort  of  rh)-thm.     Letters  went  in  a  rh>'thm,  in  groups  of  four. 

(/)  Mixed  Memory.  —  Everj'thing  seemed  to  come  in ;  the  memory  was 
certainly  not  a  pure  type,  but  very  mixed.  I  could  not  make  the  rhythm  of  the 
third  line  go  right  until  I  saw  the  card.  Saw  and  heard  the  letters :  remem- 
bered that  the  last  letters  were  formed  by  the  lips.  With  the  upward  move- 
ment seemed  to  hear  the  word  northeast ;  thought  of  a  compass,  and  visualised 
it  in  its  place  in  a  ship. 

{g)  Associations.  —  Remembered  R  and  S  because  they  go  together. 
Thought  of  algebra  when  I  heard  X.  Letters  of  first  line  made  donkey  (D, 
N,  K,  J).  Remembered  that  the  last  column  was  all  letters  towards  the  end 
of  the  alphabet. 

See  A.  Binet  and  V.  Henri,  L'Ann^e  psychologique,  ii.,  1895, 442 ;  £.  Tou- 
louse, Enqu^e  m^dico-psychologique,  etc.  (Emile  Zola),  18961  182;  S.  E. 
Sharp,  Amer.  Joum.  of  Psych.,  x.,  1899,  353,  370. 

(5)  The  Method  of  Letter  Squares  or  Cohn's  Method.  — This 
method  enables  us  to  compare  the  relative  values  of  the  visual 
and  the  auditory-motor  memory  in  a  given  individual. 

Materials.  —  Letter  squares  and  blanks. 

Experiment. — (i)  At  the  word  of  command,  O  turns  the 
letter  square,  and  reads  the  consonants  aloud,  twice  over.  He 
then  replaces  the  square,  and  counts  aloud  i  to  20,  as  before, 
for  10  sec.  At  the  second  word  of  command,  he  ceases  to 
count,  and  proceeds  to  enter  the  letters  that  he  recalls  upon 
the  blank  square. 


400  Ideational  Type  and  Association  of  Ideas 

(ii)  At  the  word  of  command,  O  turns  the  letter  square, 
sounds  the  vowel  a  (*Ah  ! ')  continuously,  and  reads  the  letters 
through  by  vision,  twice  over.  He  then  replaces  the  square, 
begins  to  count  aloud  i  to  20,  and  continues  the  counting  for  10 
sec.  At  the  second  word  of  command,  he  ceases  to  count,  and 
enters  the  letters  that  he  recalls  upon  a  blank  square. 

It  is  clear  that  the  first  procedure  favours  the  auditory-motor, 
the  second  the  visual  memory.  The  results  may  be  worked  over 
as  before. 

For  further  methods,  and  for  a  more  elaborate  mode  of  evaluating  the  re- 
sults, see  J.  Cohn,  Zeits.  f.  Psych.,  xv.,  1897,  161.  Cf.  also  H.  MUnsterberg, 
Psych.  Rev.,  i.,  1894,  34. 

(6)  The  Method  of  Distraction  or  Washbtmi  s  Method.  —  This 
method  requires  two  £"s.  The  one  E  reads  aloud  to  O  some 
interesting  tale ;  the  other  names  numbers,  which  O  is  to  add 
together. 

O  attends  as  completely  as  possible  to  the  reading,  and  (in 
order  that  E  may  have  a  check  upon  the  degree  of  attention)  is 
required,  at  the  end  of  each  experiment,  to  write  out  a  r^siim^ 
of  what  he  has  heard.  The  adding  is  continuous  :  i.e.,  each 
number  given  by  E  is  added  by  O  to  the  total  already  reached. 
O  states  the  result  of  every  separate  addition,  and  the  figures 
are  recorded  by  E.  The  experiment  may  last  from  5  to  10  min., 
according  to  (9's  powers  of  endurance. 

At  the  end  of  the  experiment,  E  has  («)  (9's  rhum^  of  the 
tale,  which  shows  the  direction  of  his  attention  and  so  indicates 
the  success  or  failure  of  the  method  ;  and  {b)  the  column  of 
figures  employed  in  the  addition,  together  with  (9's  summations. 
If  the  experiment  has  been  successfully  conducted,  E  works  over 
these  numerical  results,  noting  (9's  mistakes  as  they  occur.  The 
character  of  the  mistakes  is  an  indication  of  (9's  ideational  type. 

An  illustration  will  make  this  clear.     Suppose  that  O  says : 

312  and  15  =  317, 
724  "  33  =  657, 
599    "    29  =  618, 

and  so  on:  making  mistakes  of  10  and  100,  while  the  number  given  for  the 
digits-column  is  correct.     We  may  be  sure,  without  the  introspective  corrobo- 


§  57-    Types  of  Idea:  Methods  401 

ration  which  we  always  obtain,  that  thete  mistakes  are  mistakes  of  vision. 
Suppose,  on  the  other  hand,  that  O  says : 

282  and  20  =  503, 
569  -  23  =  593, 
634  ♦«  9  =  619* 
668    "    14  =  674, 

2nd  so  on :  making  mistakes  which  can  hardly  be  explained  from  vision,  but 
which  suggest  a  sound-echo  of  one  or  other  of  the  numbers  summed.    We 
\^  sure,  especially  if  we  obtain  introspective  corroboration,  —  which  the 
T  has  never  failed  to  do,  —  that  these  mistakes  are  auditory  or  auditory- 
motor. 

See  Titchener,  Mind,  N.  S.,  v.,  1896,  238.  For  hints  of  a  similar  method, 
i/.  Lay,  5 ;  C.  F^r^,  Rev.  philos.,  xxi.,  1886,  547. 

(7)  The  Method  of  Style  or  Frascrs  Method.  — The  thought- 
stuff  of  a  writer  may  be  inferred  with  a  high  degree  of  certainty 
from  his  writings.  Cf  A.  Fraser,  Amer.  Journ.  of  Psych.,  iv., 
1 891,  230;  Lay,  24.  A  variant  of  the  method  (observation  of 
the  imagery  aroused  in  one's  own  mind  by  the  reading  of  a  given 
author)  is  suggested  by  Lay,  29. 

(8)  Miscellaneous  Tests.  —  {a)  Image  a  red  cross,  and  then 
gaze  at  a  sheet  of  white  paper.  If  the  after-image  appears,  you 
are  of  the  visual  type.  Binet,  Psych,  of  Reasoning,  41 ;  but  cf 
James,  ii.,  67  f.  The  author  has  never  found  a  student  who 
obtained  the  after-image,  nor  has  he  ever  obtained  it  himself. 
See,  however,  J.  E.  Downey,  Psych.  Rev.,  viii.,  1901,  42. 
{b)  Let  O  learn  a  square  of  25  figures  or  letters.  If  he  is 
visual,  he  can  repeat  the  figures  in  any  order,  —  by  diagonals, 
spiral-fashion,  etc.,  —  almost  as  easily  as  he  can  repeat  them  line 
by  line ;  if  he  is  auditory  or  auditory-motor,  he  will  stumble  and 
hesitate  when  called  upon  to  travel  out  of  the  order  of  learning. 
Binet,  Psych,  des  grands  calculateurs,  etc.,  144,  146.  {c)  Stern 
(54)  suggests  an  enquiry  into  the  part  played  by  the  different 
senses  in  spatial  perception,  beginning  with  an  exact  study  of 
the  auditory  and  tactual  types  of  the  blind  consciousness  (T. 
Heller,  Philos.  Studien,  xi.,  1895,  109  f.).  (</)  An  experiment  of 
Meumann's  (Philos.  Studien,  xii.,  1896,  169)  is  made  by  Stern 
(54  ff.)  the  basis  of  a  distinction  between  a  formal  and  a  material 
type  of  temporal  perception. 

2D 


402  Ideational  Type  and  Association  of  Ideas 

Question  (3)  —  See  pp.  215  f.,  above ;  Stern,  op.  cit. ;  H.  Mun- 
sterberg,  as  quoted  p.  411,  below;  A.  Binet,  L'Ann^e  psych., 
iii.,  1897,  315  ;  S.  E.  Sharp,  Amer.  Journ.  of  Psych.,  x.,  1899, 
372  f. ;  G.  E.  Muller  and  F.  Schumann,  Zeits.  f.  Psych,  vi.,  1893, 
265  ;  etc.,  etc.     Cf.  also  the  doctrine  of  affective  temperaments. 


EXPERIMENT  XXXVn 

§  58.  The  Association  of  Ideas.  —  The  phrase  *  association  of 
ideas '  is  one  of  the  most  familiar  and  one  of  the  most  slippery 
phrases  that  are  found,  as  a  matter  of  course,  in  works  upon 
psychology.  It  is  a  phrase  with  a  long  psychological  history ; 
and  it  has,  naturally,  in  the  course  of  its  history,  taken  on  many 
different  shades  of  meaning.  The  facts  that  it  covers  are  of 
high  importance.  The  traditional  English  psychology  —  often 
spoken  of  as  the  psychology  of  *  associationism  '  —  has  not  hesi- 
tated, time  and  again,  to  compare  the  operation  of  the  law  of 
association  in  the  sphere  of  mind  with  that  of  the  law  of  gravi- 
tation in  the  physical  universe.  And  Wundt,  who  is  assuredly 
not  an  *associationist,*  is  emphatic  upon  the  point  that  without 
association  there  can  be  no  consciousness  (Phys.  Psych.,  ii., 
1893,  256,  475). 

What  is  meant  by  the  phrase  *  association  of  ideas ' .?  It  is 
sufficient  for  the  student,  at  this  stage,  to  distinguish  five  uses 
of  the  word  'association.'  {a)  Association  is  the  technical  term 
for  all  forms  of  mental  (as  contradistinguished  from  physical) 
connection,  {b)  Association  is  not  simply  a  descriptive  name 
for  mental  connection,  but  is  the  universal  principle  or  *  explana- 
tion •  of  such  connection.  Over  against  these  wider  interpreta- 
tions stand  the  following,  {c)  Association  is  the  general  name 
for  all  those  modes  of  conscious  connection  in  which  the  elements 
are  still  recognisable,  as  parts,  in  the  compound.  This  use  is 
hardly  to  be  distinguished,  in  the  older  literature,  from  {a).  In 
the  days  when  ideas  were  hypostatised  as  mental  atoms,  and 
psychology  moved  almost  exclusively  in  the  intellectualistic 
world  of  visual  and  auditory-verbal  elements,  it  was  difficult  to 
conceive  of  a  mode  of  connection  in  which  (as  in  the  fusion)  the 
parts  should  be  merged  in  an  unitary  complex,     {d)  Association 


{  5^.   Meanings  of  *  Association*  403 

is  the  explanatory  principle  of  'reproduction/  of  the  calling-up 
of  a  past  experience  by  a  present  stimulus.  Finally,  (r)  just  as 
fusion  may  mean  either  a  mode  of  intimate  connection  or  its 
product,  the  weld  or  fused  mass  of  elementary  processes,  so  may 
association  mean  —  not  the  mode  of  looser  connection,  or  its 
explanatory  principle,  but  —  the  resultant  complex,  the  *  associ- 
ated •  itself. 

We  may,  ourselves,  at  once  reject  the  uses  {b)  and  {d). 
Experimental  psychology  cannot  employ  'association'  as  a 
principle  of  explanation.  We  may  also  reject  {a):  we  do  not 
speak  of  the  formation  of  auditory  rhythm,  or  of  the  tonal  fusion, 
as  a  matter  of  association.  There  remain  {c)  and  {e).  And  we 
must  say  here  precisely  what  we  said  in  the  case  of  fusion 
(p.  330  above).  The  relation  of  associatedness  is  not  something 
superadded  upon  the  associated  sensations.  Two  sensations, 
given  together  in  temporal  succession  or  in  spatial  contiguity, 
are  given  in  the  relation  of  association ;  the  association  is  the 
look  or  sound  or  feel  of  the  sensations  as  they  occur.  Nor  must 
any  process-meaning  be  read  into  the  word  *  association.*  There 
is  no  trace  of  associating,  of  being  associated,  when  the  sense- 
processes  appear.  They  form  a  group  or  a  series;  and  this 
group  or  series,  the  sense-whole,  is  the  association.  We  may 
abstract,  in  our  logical  thinking,  the  relation  from  the  contents, 
and  speak  of  association  as  **an  observable  connection  between 
contents  of  consciousness"  (Calkins  ;  cf.  p.  109  of  the  text);  but 
there  is  no  relation-process  present,  over  and  above  the  processes 
related.  We  are  able,  having  taken  up  this  attitude  to  association, 
to  define  the  problem  which  it  offers  to  experimental  psychology. 
We  have  to  enquire  (i)  under  what  conditions  the  associated 
complex  makes  its  appearance  in  consciousness,  and  (2)  what  are 
the  distinguishing  characteristics  of  the  complex,  as  compared 
with  other  mental  formations.  The  first  of  these  questions,  as 
has  been  pointed  out  in  the  text,  falls  into  a  number  of  part- 
problems.  All  connections  tend  to  persist :  under  what  special 
conditions,  then,  is  the  given  connection  realised }  The  question 
can  be  answered,  with  some  degree  of  completeness.  For  an 
answer  to  the  second  enquiry,  on  the  other  hand,  we  are  thrown 
back  upon  descriptive  psychology. 


404  Ideational  Type  and  Association  of  Ideas 

It  is  a  little  curious,  at  first  thought,  that  the  association  of  ideas  —  apart 
from  the  question  of  its  time  relations  —  should  have  been  handled  in  step- 
motherly fashion  by  experimental  psychology.  The  riddle  is,  however,  easily 
read  when  we  remember  the  historical  conditions  under  which  experimental 
psycholog}'  arose,  and  note  the  coldness  with  which  the  experimental  method 
has  been  received,  on  its  side,  by  English  psychologists.  The  new  psychol- 
ogy came,  in  Germany,  by  way  of  revolt  against  the  metaphysical  psychology 
which  reigned  before  Herbart,  and  which  Herbart  himself,  standing  on  the 
line  of  division,  both  accepted  and  rejected ;  it  came,  in  large  measure,  from 
the  hands  of  men  who  had  received  their  training  in  natural  science  ;  it  was  to 
be  a  scientific  psychology.  But  England  had  possessed,  ever  since  the  time 
of  Hobbes,  an  empirical  (if  not  a  scientific)  psychology.  There  was  no  need 
of  revolt.  If  the  traditional  psychology  was,  in  reality,  rather  a  theory  of 
knowledge  than  a  science  of  mind,  the  result  was  only  that  it  seemed  to  be  so 
much  the  more  practical,  so  much  nearer  to  the  actual  use  and  employment  of 
mind.  Its  *  ideas'  were  the  current  coin  of  human  intercourse,  meanings, 
*  universals ' ;  but  they  passed  for  psychological  facts.  Imagine  a  psychologist 
of  this  school.  What  could  he  expect  of  the  experimental  method,  that  should 
be  better  than  the  masterly  developments  of  the  associationist  doctrine  to  be 
found  in  the  pages  of  Bain  and  Spencer  t 

Consider,  on  the  other  hand,  the  German  experimentalist,  with  the  spirit 
of  revolt  keen  within  him.  Consider  his  philosophical  ancestry,  and  his  power 
to  draw  just  those  distinctions  which  the  English  psychologists  did  not  draw. 
He  might  heartily  admire  the  skill  and  patience  of  the  associationist  writers, 
but  he  could  hardly  sympathise  with  their  position.  Moreover,  if  he  wanted  a 
VorstelUingsmechanik,  was  there  not  Herbart  ?  —  and  the  differences  between 
Herbart  and  the  English  school  would  seem  greater  than  we  now  know  them 
to  be.  So  it  is  but  natural  that  association,  except  in  so  far  as  it  is  open  to 
measurement,  has  been  neglected.  And  it  is  significant  that  the  first  investi- 
gation made,  even  into  the  time  relations  of  association,  was  made  by  an 
English  psychophysicist  (Galton,  Brain,  ii.,  1879,  M9)  5  ^'^d  ^^^^  ^he  two 
monographs  which  deal  with  association  for  its  own  intrinsic  sake,  those  of 
Scripture  and  Calkins,  are  written  by  English-speaking  psychologists. 

On  Association  in  general,  see  the  art.  by  G.  C.  Robertson,  in  the  Encyc. 
Britannica,  9th  edition ;  James,  Principles,  i.,  550;  Wundt,  Phys.  Psych.,  ii., 
437;  A.  Bain,  The  Senses  and  the  Intellect,  ed.  of  1868,  321  ;  H.  Spencer, 
The  Principles  of  Psychology,  i.,  ed.  of  1881,  250  ;  J.  Sully,  The  Human  Mind, 
ii.,  1892,  339  (and  references)  ;  G.  T.  Ladd,  Psychology,  Descriptive  and 
Explanatory,  1894,  263 ;  A.  Allin,  Ueber  d.  Grundprincip  d.  Association, 
Berlin,  1895.  Kiilpe's  chapter  on  Centrally  Excited  Sensations  (Outlines,  Pt. 
i.,  ch.  iv.,  169)  is  the  most  authoritative  statement  yet  made  from  the  experi- 
mental side,  and  will  presently  bear  rich  experimental  fruit. 

The  law  of  association,  as  stated  in  the  text,  is  that  all  the 
connections  between  sensations  which  are  set  up  by  the  forma- 


•^  is:  Apparatus  405 

tion  of  perceptions  and  ideas  tciv  sist,  even  when  the 

original  conditions  of  connection  ai.  ....  .onger  fulfilled.     This 

law  makes  the  non-fulfilment  of  original  conditions  an  extreme 
or  limiting  case.  The  name  '  association '  has,  however,  been 
narrowed  down  by  historical  usage  to  those  connections,  and  to 
those  connections  only,  which  are  realised  in  the  absence  of  the 
original  conditions  of  connection.  And  this  restriction  of  mean- 
ing, if  conventional,  is  also  convenient ;  for  it  enables  us  to 
mark  off  the  association  from  other  conscious  complexes.  The 
primary  connections,  whereby  sensations  are  grouped  into  per- 
ceptions and  ideas,  do  not  fall  under  the  rubric  of  *  associative  * 
connections.  And,  as  the  association  appears  when  the  original 
conditions  of  connection  are  not  fulfilled,  the  second  term  of  the 
association  (second  in  point  of  time,  or  secondary  in  point  of 
formation)  must  always  be  a  centrally  excited  sensation.  See 
the  author's  Outline,  201  ff. 

Materials.  —  The  apparatus  described  in  the  text  is  the 
original  form  of  Jastrow's  Memory  Apparatus,  as  sold  for  $12.00 
by  the  Garden  City  Model  Works,  124  Clark  Street,  Chicago, 
111.  The  instrument  may  be  made  of  any  size,  as  required ;  it 
can  now  be  ordered  from  the  Chicago  Laboratory  Supply  and 
Scale  Co.  The  author  would  advise  that  the  openings  in  the 
horizontal  strip  of  tin  be  made  6  and  3  cm.  in  length,  respec- 
tively, and  that  they  be  separated  by  an  interval  of  not  more 
than  I  cm.  It  is  well  also  to  run  a  string  from  the  hinged  flap 
over  a  pulley  placed  at  the  top  of  the  screen,  in  order  that  E^  as 
he  sits  behind  the  instrument,  may  be  able  to  open  and  close 
the  window  at  will. 

Stimulus  Cards. — The  cards  for  use  in  the  successive 
method  are  prepared  as  follows.  A  piece  of  white  cardboard  is 
cut  to  fit  the  card  holder.  At  the  bottom  of  the  card  —  the  end 
that  is  to  appear  first  behind  the  window  —  is  pasted  a  strip  of 
coloured  paper,  large  enough  to  fill  the  larger  opening  in  the 
middle  of  the  horizontal  strip  of  tin.  Above  this,  at  the  right 
height,  are  pasted  two  (or  more)  black  numerals.  Then  follows 
a  coloured  paper ;  then  more  white  card  and  black  numerals ; 
and  so  on.  As  the  card  is  dropped  by  the  lever,  O  will  see, 
first,  a  colour ;  then,  a  number ;  then  colour  again  ;  and  so  forth, 


406  Ideational  Type  and  Association  of  Ideas 

for  14  exposures.  Seven  colours  and  seven  numbers  are  thus 
seen  in  alternate  series. 

The  cards  for  use  in  the  simultaneous  method  are  prepared  in 
just  the  same  way,  except  that  colour  and  number  are  placed 
upon  the  same  line.  Fourteen  colours  and  fourteen  numbers 
can  thus  be  shown,  paired,  in  a  single  series.  Twelve  only  are 
employed  in  the  experiments. 

Besides  these,  E  must  have  test  cards :  cards  which  carry  the 
colours  of  the  various  stimulus  cards,  but  have  no  numerals. 
The  colours  are  rearranged  as  the  requirements  of  the  experi- 
ment suggest.     See  examples,  below. 

The  coloured  papers  may  be  obtained  from  the  Mihon  Bradley  Co.,  Spring- 
field, Mass.  Gummed  numerals  and  letters  are  sold  by  the  Dennison  Mfg. 
Co.,  198  Broadway,  N.Y.  City. 

If  the  two  openings  are  made  of  the  dimensions  recommended  above,  the 
stimulus  card  and  test  card  of  the  successive  method  can  be  combined.  The 
stimulus  colours  and  numbers  are  pasted  on  the  left  of  the  white  card,  and 
the  test  colours  on  the  right.  The  larger  opening  is  then  set  at  the  left  end 
of  the  oblong  window,  and  the  smaller  at  the  right ;  the  openings  are  blocked^ 
as  required,  by  extra  strips  of  black  japanned  tin.  E  is  thus  spared  the 
trouble  of  removing  the  card-holder  for  the  exchange  of  cards.  O's  fixation 
must  be  secured  by  a  white  paint-dot  upon  the  closed  shutter. 

It  is  possible,  in  the  same  way — though  it  is  less  convenient  —  to  employ 
three  openings  for  the  combined  cards  of  the  simultaneous  method. 

Experiments  (i)-(4).  —  The  method  of  the  first  four  experi- 
ments is  that  suggested  by  M.  W.  Calkins,  Psych.  Rev.  Mono- 
graph Suppl.  2,  1896,  37  ff.  Two  principal  modifications  have 
been  made.  Calkins*  exposure  times  and  intervals  have  proved, 
in  the  author's  experience,  to  be  too  long ;  and  it  is  necessary  to 
fill  the  intervals  with  some  occupation  (such  as  the  repeating 
of  the  alphabet),  and  not  to  let  O  stare  blankly  at  the  shutter. 
If  the  interval  is  not  filled  in  some  way,  O  is  likely  to  memo- 
rise the  foregoing  connection  of  colour  with  number  during  the 
4  sec,  and  the  whole  series  may  be  rightly  repeated. 

The  following  is  a  specimen  Frequency  series. 

Stimulus  Card  Test  Card 

Green,  47  Blue 

Violet,  61  (/)  Brown 

Brown,  73  Violet  {/) 


"^'^rrimrrt  Srn 

Srivt  I  r  N  V  ^»!:» 

TbST  GAUD 

I'tf-trf.  fM  (/) 

Green 

4 

Orange 

/  V<./r-/,  35  («) 

Calkins,  38. 

Recency 

SnMvura  Cako 

Tut  Cako 

Peacock,  46 

Grey 

Blmt,  38  (») 

B/me  (r) 

Brown,  51 

Peacock 

Stra^'bcrry,  85 

Yellow 

Grey,  74 

Strawberry 

Yellow,  29 

Brown 

BIh€,  52  (r) 

Calkins,  39. 

Vividness 

SnMOLvs  Gua> 

Test  Cakd 

Brown,  34 

Blue 

Orange,  51 

Dark  red 

Green,  792  (v) 

Violet 

Blue.  19 

Green  (v) 

Violet,  48 

Brown 

GreeHy  69  («) 

Orange 

Dark  red,  54 

407 


Calkins,  38. 

Better  than  the  three-place  number  is  a  two-place  number  printed  in  un- 
usually thick-£iced  or  thin-£aced  type,  spaced  widely,  printed  in  colour,  larger 
or  smaller  than  the  average,  etc. 


Primacy 

Stimuli-s  Ca«o  Te«t  Cako 

/jjp*/  rei^y  48  (/)  Grey 

Violet,  60  Yellow 

Grey,  82  UgAi  red  (/) 

Orange,  29  Blue 

Light  red,  31  («)  Orange 

Yellow,  53  Violet 

Blue,  69 
Calkins,  39. 

In  these  scries, /=  frequent ;  r  =  recent ;  v  =  vivid ;  /  =  prime ;  n  =  nor- 
mal. The  structure  of  the  series  will  be  evident  on  inspection.  In  every 
case,  the  *  preferred '  numeral  —  frequent,  recent,  etc.  —  has  two  chances  of 
association :  the  one  a  *  normal  ^  chance,  equal  to  that  of  the  other  terms  of 


4o8 


Ideatiofial  Type  and  Association  of  Ideas 


the  series ;  the  other  a  weighted  chance,  greater  than  that  of  the  other  terms 
by  the  handicap  which  frequency,  etc.,  bestow.  See  the  evaluation  of  results, 
below. 

The  series  are  somewhat  short,  and  it  would  be  well,  if  the  apparatus  is 
made  to  order,  to  secure  a  card-holder  arranged  for  24  exposures. 

If  time  does  not  permit  of  the  taking  of  80  series  from  every 
O^  the  number  may  be  reduced  to  40  or  20,  and  the  results 
from  the  whole  class  thrown  together  for  calculation.  This  is 
Calkins*  procedure  {e.g.^  p.  42).  Cf.  the  questionary  method,  and 
Stumpf's  mass-experiments  upon  degree  of  tonal  fusion. 

Exps.  (i)-(4)  should  not  be  performed  in  regular  sequence, 
but  carried  on,  so  to  speak,  all  at  the  same  time.  The  series 
can  be  sorted  out,  to  their  respective  experiments,  as  the  work 
proceeds ;  so  that  there  is  no  danger  of  confusion. 

Results. — The  following  specimen  Tables  are  taken  from 
Calkins :  the  data  which  the  author  has  at  his  disposal  are  less 
extensive,  though  they  offer  a  general  confirmation  of  Calkins* 
percentages. 

( I )  General  Table  of  Correct  Associations. 


Number  of  Series. 

Possible  Correct 
Associations. 

Actual  Correct  Associations  : 

Full. 

Half. 

% 

7-term  444 
10  to  i2-term  867 

2144 
7672 

674 
1728 

170 

35.2 
26.1 

(2)  Specimen  Special  Table  :  Frequency  3:12. 


Number  of 
Series. 

Both  Numbers 
Associated  : 

Normal  only 
Associated  : 

Frequent  only 
Associated  : 

Full. 

Half. 

% 

Full. 

Half. 

% 

Full. 

Half. 

% 

200 

37 

3 

19.2 

r 

9 

5.7 

83 

12 

44-5 

It  follows  that  the /-number  is  associated  in  63.7%  (44.5  + 
19.2%)  of  the  possible  cases;  the  ^-number  in  only  24.9%  (5.7 


§  58.   Association  of  Idtas :  Frequency  409 

4- 19.2  ^y    These  two  percentages  are  to  be  compared  with  the 
26. 1  %  of  the  foregoing  Table. 

Calkins'  percentages  for  vividness  are  52.2  and  20.8 ;  for 
recency  (short  series)^  53.7  and  25.7 ;  for  primacy,  36.5  and  29.5 
(great  individual  dififerences)L  In  the  short  series  in  general, 
*hc  first  number  (primacy)  showed  an  association  percentage  of 

Question  (1)  This  Question  may  be  answered  exactly  by 
the  percentages  of  correct  associations  obtained  in  comparable 
series.  Only,  E  must  be  sure  that  the  series  arc  comparable 
(cf.  Calkins,  41).  It  may  be  said,  in  general  terms,  that 
frequency  stands  highest  in  order  of  efficacy ;  *  then  follow 
vi\ndness  and  recency,  with  vividness  in  all  probability  slightly 
ahead  ;  while  primacy  has  the  lowest  position. 

(2)  It  must  be  remembered  that  all  four  experiments  presup- 
pose an  attentive  consciousness.  We  can  hardly  think  that 
frequency  of  repetition,  as  a  merely  mechanical  matter,  — 1>., 
apart  from  the  state  of  attention, — would  produce  the  effects 
here  obtained.  Let  the  mature  reader  attempt  to  recall  the 
wall-paper  of  his  childish  bedroom,  to  name  the  faces  in  a  school 
photograph,  etc.  He  will  find  that,  despite  the  extreme  fre- 
quency of  the  stimulus,  memory  is  somewhat  surprisingly  blank  ; 
unless,  of  course,  vividness  or  interest  come  to  its  assistance 
{cf.  Kulpe,  Outlines,  211).  It  must  be  remembered,  too,  that 
vividness  is  a  condition  of  exceedingly  wide  range,  and  that  the 
half-dozen  variants  which  are  at  our  disposal  for  purposes  of 
experiment  cannot  pretend  to  do  it  even  relative  justice  (Calkins, 
42)1  Again :  the  expectation  of  a  series,  —  not  of  a  single  stim- 
ulus,—  and  the  distribution  and  adjustment  of  attention  that 
follow  from  such  expectation,  must  tend  to  reduce  the  influence 
of  primacy  and  recenc 

These  and  other  like  consiucrations  will  suggest  themselves  to 
a  careful  student.  What  the  experiments  tell  us  is  that  frequency, 
recency,  primacy  and  vividness  are  real  conditions  of  association 
in  the  attentive  consciousness.  So  much  is  certain ;  farther 
it  is  hardly  safe  to  go. 

*  C/.  the  diacaasion  of  the  Uw  of  *Uie  reproduction  of  the  general,'  P>  37^* 
aboire. 


4IO  Ideational  Type  and  Association  of  Ideas 

(3)  In  answering  this  Question,  O  must  be  careful  to  distin- 
guish the  four  conditions  studied  from  the  fifth  condition,  — 
{e)  Pt.  i.,  p.  201. 

Experiments  (5)-(8).     See  Calkins,  46  f. 

In  view  of  the  extreme  similarity  of.  result,  it  is  hardly  worth 
while  to  require  a  given  O  to  perform  both  sets  of  experiments. 
The  class  may  be  divided,  half  taking  the  successive  and  half 
the  simultaneous  method.  Comparison  of  results  is,  of  course, 
only  relative. 

Related  Experiments.  Question  (4).  —  Auditory  series 
may  be  made  up  in  various  ways,  {a)  Calkins  employs  non- 
sense syllables  and  two-place  numbers,  both  pronounced  by  E. 
Vividness  is  here  best  obtained  by  reading  the  number  in  an 
unusually  loud  tone  :  one  may  also  use  a  one-place  number, 
speak  with  slowness  or  hesitancy,  speak  in  falsetto,  etc.  Pp.  47  ff . 
{b)  The  author  has  found  it  better  to  substitute  harmonium  (or 
any  form  of  reed)  clangs  for  the  nonsense  syllables.  The  clangs 
stand  nearer  to  the  colours  of  the  visual  experiments  than  do 
the  syllables. 

Both  of  these  experiments  imply  the  successive  procedure. 
For  simultaneous  work,  one  may  form  mixed  series,  whether 
{c)  of  colours  seen  and  clangs  heard,  or  (^)  of  numbers  seen  and 
clangs  heard. 

Finally,  {/)  comparative  visual  series  (Calkins,  51  ff.)  may  be 
taken.  Thus  a  12-term  successive  series  may  contain  a  thrice 
repeated  /-number  and  a  3-place  z/-number  in  combination  with 
the  same  colour  ;  or  a  7-term  series  may  be  constructed  in  which 
the  last  colour  (r)  had  appeared  once  before  with  a  3-place 
^-number,  or  at  the  beginning  of  the  series  (/),  or  twice  before 
with  the  same  number  (/). 

Further  :  the  alphabet-repetition  between  experiments  may  be 
replaced  by  some  other  occupation  :  listening  to  short  anecdotes 
or  news  items  (Calkins,  53),  arithmetical  exercises,  translation, 
etc.  And  the  interval  between  stimulus-card  exposures  and 
test-card  exposures  (or  their  auditory  equivalents)  may  be  varied 
within  wide  limits. 

These  related  experiments  may  bring  out  individual  differ- 
ences, —  associative  habits,  preferences  in  the  direction  of  atten- 


§  5S.    Association  of  Idios :  Suggestion  41 1 

tion,  liability  to  fatigue  or  distraction,  —  but  will  hardly  throw 
new  light  upon  the  conditions  of  association  at  large.  And  even 
in  the  sphere  of  individual  psychology,  we  must  not  expect  too 
rich  a  harvest  (Stem,  Psych,  d,  indiv.  Differenzen,  69).  The 
\pcrimcnts  present  two  main  advantages.  In  the  first  place, 
they  ser\-e,  by  contrast,  to  emphasise  the  extreme  delicacy, 
instability,  complexity,  transiency  of  the  most  substantive 
of  all  consciousnesses.  And,  secondly,  they  enable  O  to 
realise  the  very  gpreat  difficulty  of  introspection  in  the  asso- 
ciative field. 

/>.    The  condition  which  we  are  to  examine  is  the  relation  of 

the  given  impression  to  the  present  contents  of  consciousness 

(p.  207,  above).     The  method  was  suggested  by  Miinstcrberg 

(Beitr.  2.  experiment.   Psych.,  iv.,  1892,  17  ff.),  and  has  been 

employed  by  W.  B.  Pillsbury  (Amer.  Journ.  of  Psych.,  viii.,  1897, 

55)  and  (independently)  by  Goldscheider  and  Miiller,  op.  cit.^ 

56  ff.     It  rests  upon  the  fact  that,  if  a  word  is  displayed  for  a 

rief  time  which  presents  some  slight  difference  from  another 

)rd,  it  is  read  as  if  this  difference  were  not  visible,  provided 

ciiat  words  have  previously  been  pronounced  to  O  which  stand 

in  intimate  association  to  the  other,  slightly  different  word,  but 

have  nothing  to  do  with  the  actual  impression. 

MUnsterbcrg  obtained  his  first  hint  of  the  method  from  R.  Avenarius' 
Kritik  d.  reinen  Eriahrung,  ii.,  1890,  472.  The  author  is  glad  to  avail  himself 
of  this  opportunity  to  recommend  the  Kritik  to  psychological  readers.  Like 
certain  writings  of  E.  Mach  and  Richard  Wagner,  it  belongs  to  a  department 
of  literature  hardly  to  be  termed  psychological,  and  yet  abundantly  rich  in 
sobtle  psychological  observation. 

MUnsterberg's  procedure  differs  from  that  of  the  text  in  that  the  *  wrong  * 
words  were  given  only  occasionally,  as  puzzle  experiments.    See  p.  21. 

Materials. — The  object  cards  carry  a  monosyllabic  word. 
This  may  be  (a)  a  *real  *  word,  similar  in  form  to  the  word  which 
E  means  to  suggest.  Thus  part  will  be  read  as  past,  if  *time, 
future '  are  pronounced  ;  fright  will  be  read  as  fniit,  if  '  pear, 

:)ple*  are  given.  Or  it  may  be  (b)  a  mutilated  word.  The 
mutilation  may  be  accomplished  in  three  ways.  We  may  omit 
a  letter  altogether.     Sige  will  be  read  as  siege,  if  '  fortress,  war ' 

:e  given.     We  may  substitute  one  letter  for  another:  sixge^ 


412  Ideational  Type  and  Association  of  Ideas 

siage,  etc.     And  we  may  blur  a  letter ;  say,  by  writing  or  pasting 
an  X  over  the  middle  e  of  siege. 

On  methods  of  mutilation,  and  on  the  importance  of  the  position  of  the 
omitted,  etc.,  letter  in  the  word,  see  Pillsbury,  355  ff. 

The  series  of  object  cards  may  be  made  as  complete  and  as  long  as  the  In- 
structor deems  desirable.  The  point  of  the  experiment  —  the  misreading  of 
the  stimulus-word  under  the  influence  of  association  —  can  be  demonstrated  in 
a  few  minutes. 

Experiment  (9).  —  \i  O  does  not  read  the  stimulus-word  at 
the  first  exposure,  he  should  keep  his  eye  at  the  tube  until  its 
reading  is  possible.  E  notes  the  number  of  revolutions  required. 
Most  (9*s  withdraw  their  eye  from  the  tube  as  soon  as  ever  the 
*  suggestion  '  has  operated.  Should  an  O  incline  to  await  further 
exposures,  in  order  to  verify  the  suggestion,  he  must  be  cau- 
tioned to  read  the  word  at  the  earliest  possible  moment :  other- 
wise—  since  the  word  falls  within  the  range  of  attention  —  he 
will  presently  notice  the  mutilation,  and  so  get  an  inkling  of  the 
nature  of  the  experiment. 

When  E  takes  the  place  of  (9,  he  will,  of  course,  be  working 
*with  knowledge.'  A  comparison  of  the  two  sets  of  results  is 
instructive.  The  number  of  misreadings  is  reduced,  but  by  no 
means  reduced  to  zero.  The  new  E  should  introduce  (and  should 
inform  O  that  he  has  introduced)  a  certain  number  of  correctly 
printed  cards  into  the  series  ('puzzle  experiments '). 

On  the  time  of  exposure,  and  its  regulation,  see  Pillsbury,  345.  The 
essentials  of  Scripture's  and  Pillsbury 's  apparatus  (criticised  by  J.  Zeitler,. 
Philos.  Studien,  xvi.,  1900,  441)  are  given  with  the  after-image  apparatus  of 
Exp  IV.  (see  Pt.  i.,  Fig.  5). 

Question  (5)  The  general  conclusion  is  that  a  close  relation 
of  the  new  impression  to  the  present  contents  of  consciousness — 
one  of  the  determinants  of  passive  attention  —  is  of  high  associ- 
ative importance.  We  have  not  been  able  so  to  arrange  the 
experiment  that  condition  (^)  can  operate  in  pure  form.  To 
that  end,  we  should  have  to  take  an  O  who  was  in  a  state  of  day- 
dreaming or  reverie,  to  subject  him  to  stimuli,  some  of  which 
were  and  some  of  which  were  not  related  to  his  train  of  ideas. 


§58.   Association  of  Ideas:  Train  of  Ideas  413 

and  to  show  that  the  former  did  while  the  latter  did  not  alter 
the  direction  of  the  train.  The  task  is  difficult,  if  not  impos- 
sible ;  and  our  experiment  serves  every  purpose. 

(6)  Mutilated  sentences  are  spoken  into  a  phonog^ph,  and 
then  repeated  to  O,  Sec  W.  C.  Bagley,  Amer.  Joum.  of  Psych., 
xii..  19CX).  80  ff. 

(7)  This  question  has  been  answered  do£p:natically  in  the 
answer  to  (5)  above.  The  student  will  be  able  to  work  out  the 
reasons  for  that  answer  on  his  own  behalf. 

C.  The  Train  of  Ideas,  —  It  is  customary  to  employ  printed 
or  spoken  words  as  the  stimuli  to  the  train  of  ideas.  Words 
were  chosen  for  this  end  by  Galton,  and  have  been  much  used 
by  later  writers.  The  advantages  of  the  word-stimulus  are 
obvious ;  and,  under  certain  conditions  of  experimentation,  we 
have  hardly  any  choice  but  to  accept  it.  On  the  other  hand,  the 
isolated  word  is  not  the  natural  starting-point  of  an  associative 
series ;  the  mental  unit  is  the  sentence.  Hence  the  author 
recommends  the  present  exercise  as  a  substitute  for  the  word- 
test.  It  seems,  at  first  sight,  to  be  somewhat  complicated ;  but 
it  has  stood  the  test  of  laboratory  practice.^  The  following 
fllustration  will  speak  for  itself. 

Question.  —  Who  ^'as  king  of  England  in  the  year  1654? 

Report  of  Introspiction.  —  Saw  outline  map  of  England  and  Scotland,  the 
southern  part  more  distinct.  Saw  the  number  1654,  and  tried  to  remember 
who  was  king  (verbal).  Thought  of  Gurth  and  Wamba.  Woods ;  dining- 
room  in  Saxon  house :  verbal  and  visual,  but  forest  clearly  visual.  Knew  that 
Scott  (verbal)  was  the  author  of  the  book.  Tried  to  think  of  name  of  book. 
Ivanhoc :  verbal-auditory.  Tournament ;  visual  picture  of  Disinherited  Knight. 
Date  bothered  again.  Indistinct  picture  of  C.  U.  football  team  on  Percy  Field. 
Line-up  rather  distinct.  Lehigh  and  Princeton  games  (verbal-auditory). 
Verbal  idea  of  own  i)ractice. 

The  introspective  report  may  be  thrown  into  tabular  form  as 
follows. 

*  It  wiil  be  ncccuary  to  give  some  half-dozen  preliminary  tests,  before  the  exp.  is 
serk>iisly  undertaken.  The  sisociatiTe  consciousness  is  to  complex,  and  its  constitu- 
eoU  so  elusive,  that  the  result  of  the  first  few  trials  will,  in  all  probability,  l>e  nothing 
but  confusion.     A  careful  O  will,  however,  very  soon  bring  order  out  uf  the  chaos. 


414 


Ideational  Type  and  Association  of  Ideas 


Table 

Total  time,  x6o  sec. ;  catch  words,  4. 


Situations. 

Time. 

QUALITV. 

Affective 
Tone. 

Mode  of 

Con- 
nection. 

Richness, 

etc. 

Point  of 
Depar- 
ture. 

I 

J/«> 

a  sec. 

Visual 

Indifferent 

G)ntiguity 

All  clear,  but 
best  in  lower 
parts 

Stimulus 

a 

Date 

Visual  and 
organic 

Unpleasant 

Contiguity 

Clear 

Stimulus 

3 

King 

Verbal  -  audi- 
tory and  vis- 
ual ;     but 
chiefly     or- 
ganic 

Unpleasant 

Contiguity 

Full,   but 
vague 

Stimulus, 
and  I  and 

a 

4 

Gurth  and 
Wamba, 
suppl e- 
mented  by 
woods,  din- 
ing room 

40  sec. 

Visual,    ver- 
bal-auditory, 
organic;  the 
forest  visual 

Pleasant,  so  far 
as    pictures 
were    con- 
cerned; unr 
pleasant, 
when  I  tried 
to      remem- 
ber author's 
name 

Similarity, 
with  asso- 
ci  at  i ve 
supple- 
menting 

Clear,    with 
vague  fringe 

Last  idea 

5 

Scott 

Verbal -audi- 
tory, organic 

Pleasant 

Contiguity 

Clear 

Last  idea 

6 

Ivanhoe 

Verbal-audi- 
tory 

Pleasant 

Contiguity 

Clear 

Last    two 
situations 

7 

Tourna. 
meni 

75  sec. 

Visual     and 
verbal-audi- 
tory 

Pleasant 

Contiguity 

Word  clear; 
details      of 
visual    im- 
agery indis- 
tinct:    full 
conscious- 
ness 

Last  three 
situations 

8 

Knight 

Visual 

Pleasant 

Contiguity 

Conscious- 
ness '  thin- 
ner';     im- 
age     more 
distinct 

Preceding 
situations 

9 

Date 

Visual     and 
organic 

Unpleasant 

Similarity  ? 

Clear 

Stimulus, 
or  its  im- 
mediate 
associ- 
ates 

xo 

Football 

125  sec. 

Visual    (and 
motor  ?) 

Pleasant 

Similarity 

Indistinct  in 
detail ;  line- 
up clear 

Situation 
7 

XX 

Lehigh  and 
Princeton 
games 

Verbal-audi- 
tory 

Indifferent 

Contiguity 

Indistinct 

Last  idea 

XI 

Practice 

Verbal-audi- 
tory (calls) 

Indifferent 

Contiguity 

Very    indis- 
tinct 

Situation 
10 

Exp.  ended 
at  160  sec. 

'^ 


s„ 


§  58.    Thi   Trah'    ^    '•  415 

The  diagram,  which  should  be  panUicled  by  tbe  lime-scale,  will  have 
the  following  form. 

It  may,  of  course,  be  made  very  much  more  elaborate.  The 
situations  may  be  more  fully  anal)'sed,  in  Scripture^s  way; 
different  kinds  of  lines  may  represent  the  two  different  modes 
of  connection ;  the  *  fringes  *  and  *  strands  *  of  consciousness  may 
be  indicated,  etc.,  etc. 

It  is  clear  that  an  experiment  of  this  sort  will  throw  j  >  ^ 

some  light  upon  the  mechanism  of  the  associative  { 

consciousness,  will  afford  training  in  introspection,  i  <•• 

and  will  drive  home  the  lessons  taught  by  the  Related 
Experiments  of  Question  (4).  The  experiment  has 
never  failed,  in  the  author's  experience,  to  elicit  such 
remarks  as  :  "What  a  tangle  of  stuff  there  is  there ! " 
or  *' I  never  knew  before  what  an  idea  was  really  like!**  — 
whereas  the  association  series  that  follows  upon  a  word-stimulus 
is  apt  to  be  as  artificially  clean-cut  and  over-focal ised. 

For  word  associations,  and  a  classification  based  upon  them,  see  T.  Ziehen, 
Die  Ideenassoziation  d.  Kindes,  i.,  Berlin,  1898  (Sammlung  v.  Abh.  aus  d. 
Gebiete  d.  padagogischen  Psych,  und  Physiol.,  herausg.  v.  H.  Schiller  u.  T. 
Ziehen,  i.,  6). 

Question  (8)  This  Question  is  answered  in  what  follows.  The 
Instructor  may  avail  himself  of  it  to  take  the  student  as  far  into 
the  general  psychology  of  association  as  time  permits. 

The  experimental  literature  of  association  falls  into  two  main 
divisions  :  the  work  done  by  the  reaction  method,  and  the  mono- 
graphs of  Scripture  (incomplete)  and  Calkins.  Under  the  former 
heading  fall  the  investigations  of  M.Trautscholdt(Philos.  Studien, 
i.,  1883,  213),  J.  McK.  Cattell  {ibid.,  iv.,  1888,  241),  E.  Kraepelin 
(Tagebl.  d.  Naturforschervers.  z.  Strassburg,  1885  ;  Ueb.  d.  Beein- 
flussung  einfachster  psych.  Vorgange  durch  einige  Arzneimittel, 
Jena,  1892),  G.  Aschaflfenburg  (Psychol.  Arbeiten,  i.,  1895,  209), 
and  H.  Munsterberg  (Beitr.,  i.,  1889,  64).  We  have  ourselves 
drawn  for  experimental  material  upon  Miinsterberg  (Beitr.,  iv., 
1892,  17)  and  Calkins.  The  first  part  of  E.  W.  Scripture's  re- 
search is  to  be  found  in  the  Philos.  Studien,  vii.,  1892,  50.  A 
parallel  investigation  by  Munsterberg  (mentioned  in  Beitr.,  iv., 
24)  has  not  as  yet  been  published. 


4i6  Ideational  Type  and  Association  of  Ideas 

If  we  sift  out  the  general  results  of  the  enquiries  which  have 
not  been  considered  in  what  precedes,  we  seem  to  find  the 
following  laws.  Several  of  them  are  generalisations  from  inci- 
dental remarks  or  single  experimental  results  :  all  would  repay 
reinvestigation.  And  even  if  all  are  valid,  they  make  but  a 
poor  showing  as  against  the  complexity  of  the  concrete  con- 
sciousness, the  "ununterbrochene  Vcrflechtung,  in  welcher  alle 
Dispositionen  einmal  gehabter  und  unserem  Bewusstsein  noch 
verfugbarer  Vorstellungen  mit  einander  stehen." 

I.  (i)  Temporal  connections  of  ideas  stand,  as  regards  quick- 
ness of  realisation,  in  the  order  unequivocal,  ambiguous,  free. 
The  proportion  is,  roughly,  3  or  4 :  5  or  6  :  7  tenths-of-a-second. 
The  rule  is  a  rule  of  average,  and  has  many  exceptions.  (2)  The 
more  frequently  an  idea  has  been  connected  with  other  ideas, 
the  more  quickly  and  readily  does  it  associate  in  the  experimental 
case.  (3)  The  more  direct  the  temporal  connection  of  two  ideas, 
the  more  quickly  is  it  realised.  (4)  The  more  closely  related  a 
given  idea  is  to  another  idea,  the  more  quickly  does  it  connect 
with  this  other.  (5)  The  more  frequently  a  given  form  or  order 
of  connection  between  ideas  has  occurred,  the  more  quickly  is  it 
realised  in  the  experimental  case.  (6)  The  more  intensive  or 
clear  the  idea,  the  more  quickly  does  it  connect  with  other  ideas. 

II.  (7)  The  more  intensive  or  vivid  idea  connects  with  the 
more  intensive  or  vivid  idea.  (8)  The  more  frequently  or  per- 
manently an  idea  has  been  present  in  consciousness,  the  more 
vivid  and  clear  are  the  ideas  that  connect  with  it.  (9)  Related 
ideas  frequently  connect  with  the  same  idea.  (10)  Many  peculi- 
arities of  association  can  be  explained  by  reference  to  a  law  of 
exclusion.  "When  a  simultaneous  or  successive  connection  of 
three  contents,  ^,  b  and  c,  has  established  a  liability  of  repro- 
duction between  a  and  c,  c  gradually  comes  to  be  directly  excited 
by  tty  without  the  intermediation  of  b  "  (Kiilpe,  Outlines,  209). 

This  law  of  exclusion  suggests  the  doctrine  of  'association  by  unconscious 
intermediaries,'  maintained  by  Scripture  (83),  accepted  in  modified  form  by 
Wundt  (Human  and  Animal  Psych.,  306  f.,  3d  German  edn.,  349  f. ;  Philos. 
Studien,  vii.,  360  f. ;  Phys.  Psych.,  ii.,  459  f.)  and  Aschaffenburg  (Psychol. 
Arbeiten,  i.,  1895,  244,  294),  but  negatived  by  the  work  of  Munsterberg  (Beitr., 
iv.,  1892,  i),  H.  C.  Howe  (Amer.  Journ.  of  Psych.,  vi.,  1894,  239)  and  W.  G. 


§  $8.    Classification  of  Associations  417 

Smith  (Mind,  N.S.,  ii-f  1894,  389;  Zur  Fnige  d.  mittelb.  Asa.,  Leipxig,  1894). 
Cf,  also  W.  JeruMlcnu  Philos.  Studien,  x.,  1894,  323,  and  Wundt,  ibid.^  326. 
The  antbor  believes,  with  Miinsterberg,  that  there  is  no  such  thing  as  an  asso- 
ciation by  unconscious  intennediaries.  He  is,  however,  of  the  opinion  that 
associations  occur  in  experinM^ntal  practice  which  represent  various  stages  or 
degrees  of  the  habit-process  which  culminates  in  the  Uw  of  exclusion. 

The  concept  of  psychological  *  relationship '  must  be  worked  out  by  the 
student,  as  we  worked  out  the  concept  of  *  similarity  ^  above,  pp.  54  f. 

Experiments  upon  the  reaction  time  of  association  can  be  earned  out  by 
aid  of  the  vernier  chronoscope.  See  San^-^rf!.  Amer.  Journ.  of  Psych.,  Ix., 
196  f. 

The  question  of  the  classification  of  successive  associations, 
like  the  question  of  the  classification  of  the  emotions,  is  an  old  one 
in  psychology.  We  have,  in  the  text,  kept  the  rubrics  *  associa- 
tion by  similarity'  and  'association  by  contiguity.'  Wundt 's 
substitution  of  the  terms  *  intrinsic '  and  *  extrinsic '  association 
—  the  former  dependent  upon  the  principle  of  associative 
relationship,  the  latter  upon  that  of  associative  practice  —  marks 
a  distinct  step  in  advance.  But  the  advance  consists  rather  in 
the  explication  of  the  principles  than  in  the  change  of  classi- 
ficatory  names.  Wundt's  own  classification  (Phys.  Psych.,  ii., 
455)  is  logical,  not  psychological,  in  its  details.  The  still  more 
elaborate  classification  of  Aschaffenburg  {op,  cit.,  231),  which  is 
based  upon  Wundt's  dichotomy,  has  little  psychological  value. 
On  the  other  hand,  Miinsterberg's  distinction  of  three  intellec- 
tual temperaments,  the  subordinating,  coordinating  and  super- 
ordinating  (Beitr.,  iv.,  36),  although  it  is  open  to  criticism  on 
several  counts,  does  good  service  in  laboratory  work 

In  the  author*s  opinion, — an  opinion  resting  on  several  years^  class- work 
in  association  reactions, —  Miinsterberg's  three  temperaments  come  nearer  to 
the  tnie  psydiological  *  t>'pe '  than  is  admitted  either  by  Stern  {op.  cit.^  69)  or 
by  Aschaffenburg  (225).  MUnsterberg  himself  grants  (33)  that  the  classifica- 
tion is  not  exhaustive. 

The  reader  who  is  interested  in  the  question  of  classification  may  consult 
further:  F.  Paulhan.  L'activit^  mentale  et  les  ^l<5ments  de  Tesprit,  Paris,  1889; 
R.  Wahle,  Vierteljahrss.  f.  wiss.  Fhilos.,  ix.,  1885,  404;  M.  Offner,  Philos. 
Monauhefte,  xxviii.,  1892,  385,  513 ;  B.  Bourdon,  Rev.  phil.,  xxxii.,  1891,  561. 

Wundt's  Bemerkungen  zur  Associationslehre  (Philos.  Studien, 

1.,  1892,  329)  represent  the  first  attempt  at  a  psychological 

theory  of  the  association.     The  p^per  was  prompted  by  the  well- 

2E 


4i8  Ideational  Type  and  Association  of  Ideas 

known  controversy  between  H.  Hoffding  and  A.  Lehmann  (see 
references,  pp.  331  ff.);  but  its  conclusion  follows  directly  from 
Wundt's  primary  distinction  of  intrinsic  and  extrinsic  associa- 
tions. "  All  associations,"  says  the  summary  in  the  Phys.  Psych., 
ii,,  468,  "are  the  resultants  of  elementary  connective  processes^ 
between  simple  sensations  or  relatively  limited  sense-complexes. 
Two  such  elementary  processes  are  conceivable ;  and  both  may 
be  traced  in  every  instance  of  association.  They  are  the  con- 
nection of  identical  elements,  and  the  connection  of  elements 
which  have  entered  into  a  functional  interrelation  by  their  com- 
mon occurrence  in  consciousness.^  We  will  term  these  two 
forms  of  elementary  connection  the  connection  of  identity  and 
the  connection  of  contiguity.  These  names  suggest  the  cus- 
tomary terminology  of  association.  But  we  do  not  mean  to 
imply  that  what  is  usually  called  an  *  association  by  similarity ' 
can  be  analysed  into  elementary  connections  of  identity,  or  an 
'association  by  contiguity*  into  elementary  connections  of  con- 
tiguity. Both  alike  depend  upon  the  simultaneous  operation  of 
the  two  elementary  processes."  The  formula  of  the  former, 
roughly  stated,  is  abc-bcd ;  the  formula  of  the  latter  abc-cde.  We 
have,  then,  the  connections  of  identity  bc-bc  and  c-c,  and  the  con- 
nections of  contiguity  a-d  and  ab-de.  It  is  clear  that  the  term 
'connection*  in  the  phrase  'connection  of  identity'  is  only 
figurative ;  the  qualitative  contents  of  the  original  sensation  or 
sense-complex  remains  unchanged ;  the  sense-link  changes 
merely  in  intensity  and  (more  especially)  in  power  over  the 
attention.  "We  retain  the  term  'connection,'"  says  Wundt 
(469),  "  in  order  to  emphasise  the  equal  significance  of  the  two  — 
always  coexistent  —  processes.  .  .  .  The  relation  of  the  identity 
to  the  contiguity  connections  may  be  expressed  in  the  proposi- 
tion that  the  former  enhance  the  effect  of  a  given  ideational 

^  *  Processes '  in  the  ordinary  sense  of  *  occurrences  or  operations  in  time,'  not  in 
the  technical  sense  in  which  we  speak,  e.g.,  of  sensation  as  a  *  mental  process.' 

2  In  speaking  of  the  identity  connection,  Wundt  uses  the  itxvns  gleich,  sich  deckend, 
ubereinsiimmend,  [den  beiden  Vorstellungen]  gemein  ;  in  speaking  of  the  contiguity 
connection,  the  phrases  das  zeitlich  und  r'dumlich  durch  Beriihrung  Verbundene,  die 
BestandtheiU  die  in  friiheren  Vorstellungen  mit  jenen  i^leichen  Elementen  in  ausserer 
Beriihrung  gewesen  war  en,  die  Elemente  die  durch  gemeinsames  Vorkommen  in  einen 
functionellen  Zusammenhang  getreten  sind. 


§  5^.    Th€  Ultimate  Canfuctive  Procfssis  419 

clement  upon  consciousness  on  the  intensive,  the  latter  on  the 
extensive  side 

It  is  but  natural  that  we  should  look  for  confirmation  of  this  analytic  theory 
to  Scripture*s  monograph,  the  chief  aim  of  which  was  **  the  collection  of  a  large 
number  of  individual  &cts,  from  which  conclusions  might  be  drawn  as  to  the 
particular  conditions  of  the  association  of  ideas  *^  (5 1  )•  And  for  one  who  reads 
between  the  lines.  Scripture's  article  is  rich  in  suggestion.  Unfortunately,  the 
author  himself  is  trapped  in  the  logical  pitfall  which  has  swallowed  up  so  many 
of  the  association  psychologists.  His  four  categories  of  preparation,  influence, 
apposition  and  after-effect  are  logical,  not  psychological,  in  character.  This 
is  shown  partly  by  the  writer's  subdivisions  (see,  /.jf.,  88),  but  still  more 
plainly  by  the  evidence  of  overlapping  which  his  instances  afford.  Logically, 
the  four  stages  may  be  distinguished ;  psychologically,  they  run  into  one  an- 
other, cross  one  another,  form  toUl  processes  whose  dissection  is  entirely 
artiflciaL  It  is,  however,  only  fair  to  say  that  Scripture's  theoretical  conclu- 
sions have  not  yet  been  published  (146). 

It  is,  perhaps,  worth  while  again  to  call  the  reader's  attention  to  the  dis- 
parity obtaining  between  the  *  idea '  of  the  traditional  English  associationism 
and  the  VorsUUung  of  experimental  psychology.  See,  esp.,  Wundt,  Philos. 
Studien,  vii.,  358  f. ;  x.,  1894,  121  ff. ;  MUnsterberg,  Beitr.,  iv.,  26. 

The  second  part  of  the  problem  which  association  sets  to  ex- 
perimental psychology  is  the  problem  of  "the  distinguishing 
characteristics  of  the  complex,  as  compared  with  other  mental 
formations"  (p.  403)1  A  good  deal  of  work  has  been  done,  as 
we  have  seen,  upon  the  duration  of  the  association ;  and  much 
has  been  done  also,  though  we  have  made  no  mention  of  it  in 
this  Volume,  upon  the  duration  and  time-relations  of  the  simple 
sense-processes  which  underlie  the  association.  The  question 
of  the  intensity  oi  the  association  as  compared  with  the  intensities 
of  its  elements  —  unlike  that  of  the  fusion  (Stumpf,  ii.,  41,  423 
ff . ;  Kiilpe,  283)  —  appears  not  to  have  been  discussed.  We 
must  start  out  from  Kulpe's  definition  of  the  colligation  (21, 
277X  as  the  mode  or  pattern  of  connection  typical,  in  analytical 
psychology,  both  of  temporal  and  spatial  perceptions  and  ideas, 
and  of  the  association  of  ideas,  and  ask,  first  of  all,  as  to  the 
intensity  of  a  spatial  connection  of  sensations.  What  do  we 
mean  by  the  intensity  of  brightness  and  colour  in  *a  picture,'  a 
colligated  whole  of  visual  elements.^  We  mean,  probably,  a 
middle  intensity,  higher  than  that  of  the  shades  and  lower  than 
that  of  the  lights  in  the  composition.     What  shall  we  say,  again, 


420  Ideational  Type  and  Association  of  Ideas 

of  the  quality  of  such  a  colligation  ?  —  a  question  parallel  to  that 
of  the  pitch  of  a  fusion.  We  can  only  say  the  obvious.  If  the 
colligated  qualities  are  the  same,  then  we  have,  in  the  case  of 
spatial  colligation,  a  single  quality  of  greater  extension  ;  in  the 
case  of  temporal  colligation,  a  single  quality  of  greater  duration. 
If,  on  the  other  hand,  the  colligated  qualities  are  different,  then 
we  have  a  looser  unity,  one  that  runs  the  risk  of  simultaneous  and 
successive  contrast.  The  spatial  colligations  of  everyday  life  — 
our  dress,  furniture,  house  decorations  generally  —  are  evidently 
planned  with  implicit  reference  to  this  danger. 

The  questions  of  the  intensity,  quality  and  space-relations  of 
the  colligation  offer  an  inviting  field  for  new  work. 

Further  Experiments. — For  other  ways  of  attacking  the 
association  problem,  cf.  the  following. 

(i)  J.  A.  Bergstrom,  Amer.  Journ.  of  Psych.,  v.,  1893,  356; 
vi.,  1894,  432;  H.  Miinsterberg,  Beitr.,  iv.,  1892,  69. 

(2)  H.  Ebbinghaus,  Das  Gedachtniss,  Leipzig,  1885 ;  H. 
Miinsterberg,  Zeits.  f.  Psych.,  i.,  1890,  99;  G.  E.  Miiller  and 
F.  Schumann,  ibid.,  vi.,  1893,  81,  257  (and  later  articles  from 
Miiller's  laboratory  in  the  same  journal);  G.  E.  Miiller  u. 
A.  Pilzecker,  Experiment.  Beitr.  zur  Lehre  vom  Gedachtniss, 
Leipzig,  T900  (critique  of  Calkins,  155  f.). 


APPENDIX   I 

Examination  Questions 

The  following  questions  are  taken  from  examination  papers  set  during  the 
last  few  years  in  the  qualitative  part  of  this  Course.  They  give  a  rough  idea 
of  the  standard  which  the  student  may  be  expected  to  attain. 

I 

1.  What  are  the  chief  phenomena  of  colour  contrast }  How 
are  they  explained  (a)  by  Helmholtz  and  (d)  by  Hering  ? 

2.  Define  the  terms  and  phrases :  local  adaptation,  disposi- 
iion,  simultaneous  light  induction,  valence,  rise  and  fall  of 
sensation,  flight  of  colours,  after-inlage.  What  is  the  e£Fect 
for  vision  of:  the  macular  pigment,  the  visual  purple,  the 
imperfections  of  the  dioptric  media  .^ 

3.  Mention  some  of  the  weak  points  of  the  Young- 
Helroholtz  theory  of  visual  sensations.  State  briefly  the 
amendments  proposed  by  Hering,  von  Kries,  C.  L.  Frank- 
lin, Pick. 

4.  Either:  Give  Fechner's  theory  of  the  negative  after- 
image. How  would  you  set  to  work  to  test  it,  from  Hering's 
standpoint  .^ 

Or:  What  apparent  change  does  a  red-green  blue-yellow 
white-equation  undergo  with  change  of  objective  illumination  ? 
What  explanations  of  it  have  been  offered } 

II 

1.  Describe  the  structure  of  the  cochlea,  including  the 
arrangement  of  the  terminal  formations.  Illustrate  by  dia- 
grams. 

2.  What  reasons  led  Helmholtz  to  modify  his  original 
theory  of  audition.^ 

4JI 


422  Appendix  I. 

3.  What  are  '  gaps '  or  *  tonal  islands '  ?  How  are  they  to 
be  explained  by  the  Helmholtz-Hensen  theory?  Would  this 
explanation  be  affected  by  the  Ebbinghaus  theory  ?     How  ? 

4.  What  are  Rutherford's  objections  to  the  Helmholtz- 
Hensen  theory  ?  What  is  his  own  theory  ?  What  criticisms 
can  be  passed  upon  it  ? 

5.  What  is  the  difference  between  *  structural  *  and  *  func- 
tional '  psychology  ?  Illustrate  by  reference  to  the  lectures 
or  experimental  work  of  the  past  term.  Which  is  the  more 
important  to  the  beginner  in  psychology  ?     Why  ? 

6.  What  are  the  chief  reasons  for  and  against  the  existence 
of  a  third  conscious  element  ? 

7.  Explain  clearly  the  relation  of  affection  (i)  to  sensation 
and  (2)  to  attention. 

8.  Can  a  psychological  experiment  be  performed  by  the 
lecturer  before  a  class }  If  so,  is  it  advisable  that  experiments 
should  be  thus  performed } 

III 

1.  What  are  our  reasons  for  supposing  that  the  skin  contains 
separate  organs  for  pressure  and  for  pain }  And  what  are  the 
reasons  for  the  further  assumption  that  the  pain  organs  are 
situated  more  peripherally  than  the  pressure  organs } 

2.  What  is  Dessoir's  classification  of  the  provinces  of  Haptics.^ 
What  criticisms  have  you  to  offer  upon  it  ? 

3.  Summarise  Goldscheider's  arguments  in  favour  of  the  ex- 
istence of  a  sensation  of  movement.     Criticise  them. 

4.  How  would  you  set  to  work  to  discover  the  cold  spots  of 
the  skin }  Describe  method,  apparatus,  etc.  What  special 
precautions  would  you  take  to  avoid  error } 

5.  Define  experiment.  How  does  a  psychological  experiment 
differ  from  the  experiment  of  physical  science }  Should  labora- 
tory work  in  psychology  be  preceded  by  a  lecture  course  t 
Why  >  Should  a  course  of  lectures  in  psychology  be  illustrated 
by  demonstrations  and  desk-experiments  }     Why  } 

6.  On  the  wall  facing  you  hangs  a  spectrum  chart.  What 
facts  of  importance  for  the  psychology  of  vision  does  an  intro- 
spective examination  of  this  chart  bring  out } 


ExaminatioH  Qutstions  423 

7.  It  is  probable  that  we  employ  brightness  (illumination  of 
m  object)  as  a  criterion  of  distance ;  i.e.,  that  the  brighter  a 
thing  is,  the  nearer  (other  things  equal)  do  we  take  it  to  be. 
Suggest  a  simple  form  of  apparatus  for  the  investigation  of  this 
problem.     Give  drawings. 

IV 

1.  What  is  the  special  method  of  psychology  ?  How  does  it 
resemble,  and  how  does  it  differ  from,  the  methods  employed 
by  the  physical  or  natural  sciences } 

2.  What  qualities  of  sensation  occur  in  consciousness  during 
the  writing  of  a  sentence  upon  paper  ? 

3.  Describe  briefly  the  structure  and  mode  of  function  of  the 
auditory  organ. 

4.  How  would  you  set  to  work  to  discover  what  qualities  of 
smell  the  nose  can  distinguish  ? 

5.  If  with  closed  eyes  you  move  the  two  hands  outwards 
from  the  median  plane  of  the  body,  and  attempt  to  make  your 
two  movements  of  equal  length,  one  hand  will  be  found  to 
travel  farther  than  the  other.  Which  hand  makes  the  greater 
excursion,  and  why  ? 

6.  Analyse  the  perceptions  of  resistance,  impact,  traction  and 
ivetn€ss. 

7.  What  are  the  attributes  of  a  *  perfect  *  sensation  ?  Give 
instances  of  perfect  and  imperfect  sensations. 

8.  Describe  some  recent  expenence  which  would  throw 
light  on : 

(a)  your  memory  type ; 

{b)  your  emotional  temperament ;  and 

(c)  your  intellectual  temperament  or  type. 


1.  Define  'local  sign.'  How  has  the  system  of  local  signs 
developed  }  Can  you  think  of  any  alternative  theory  to  that  of 
local  signature } 

2,  Give  a  full  analysis  of  the  perception  of  melody. 


424  Appendix  I. 

3.  Distinguish  *  perception,'  *  idea,*  *  simultaneous  association 
of  ideas.'  What  is  the  law  of  association  ?  Apply  it  to  in- 
stances chosen  from  each  of  the  four  main  subdivisions  of 
association. 

4.  Classify  and  explain  the  movements  which  'express* 
emotion. 

5.  Outline  the  psychology  of  impulse. 

6.  EWier  (i)  work  out  a  classification  of  emotions,  stating 
the  principles  upon  which  the  classification  is  based  ;  or  (2) 
show,  by  references  to  examples,  the  importance  of  genetic 
psychology  for  the  analysis  of  complex  psychological  processes. 

VI 

1.  What  do  you  mean  by  '  accommodation ' }  What  is  its 
organ,  and  how  does  that  organ  function  } 

2.  What  anomalous  relations  exist  between  stimulus  and 
sensation  in  the  sphere  of  sight } 

3.  State  Wundt's  theory  of  colour  vision. 

VII 

1.  State  the  facts  of  colour-blindness.  To  what  facts  of 
normal  colour  vision  are  they  related,  and  in  what  way .? 

2.  Describe  the  methods  of  colour  mixture.  What  are  the 
special  advantages  and  disadvantages  of  the  method  with  which 
you  are  yourself  familiar  .^ 

3.  Formulate  the  general  dependence  of  visual  sensation 
upon  {a)  amplitude,  {b)  frequency  of  oscillation,  and  (^)  com- 
position of  the  ether  wave.  Give  a  case  of  special  depend- 
ence under  each  head,  illustrating  by  reference  to  a  concrete 
example. 

4.  Make  a  list  of  the  general  and  special  rules  for  introspec- 
tion in  experimentation  upon  simultaneous  hand-movements 
(*  innervation '  sense).  Discuss  the  question  of  the  existence 
of  an  innervation  sensation. 

5.  What  are  the  constant  sources  of  error  to  be  guarded 
against  in  all  psychological  experimentation  }     Illustrate  by  an 


Examimatiom  QutsHoms  425 

analysis  eiiker  of  Aristotle's  experiment  or  of  the  experiment 
on  Weber's  sensory  circles. 

6.  What  are  the  principal  introspective  data  from  which  a 
theory  of  visual  sensation  has  to  set  out  ?  What  are  the  princi- 
pal anatomical  and  physiological  data  ? 

7.  Give  a  theory  of  the  intermittences  observable  in  a  sound 
that  lies  near  the  limit  of  audibility. 

8.  What  are  the  chief  reasons  for  and  against  the  acceptance 
of  the  solar  spectrum  as  the  standard  of  reference  in  work  upon 
colour  vision  ? 

9.  Suppose  that  you  were  beginning  an  investigation  into 
the  pressure  after-image.  What  problems  would  you  set  your- 
self for  solution }  Are  they  in  any  way  parallel  to  the  prob- 
lems that  arise  in  the  investigation  of  visual  sensation }  By 
what  methods  would  you  work }  Give  full  reasons  for  your 
choice. 

VIII 

1.  What  is  *  introspection  *  ?     Give  an  instance  of  it. 

2.  What  is  the  relation  of  ione  to  noise,  physically  and  psy- 
chologically ? 

3.  How  many  qualities  of  sensation  are  furnished  by  the 
skin  ?     Give  reasons  for  your  answer. 

4.  What  is  the  function  of  the  internal  ear } 

5.  Touch  yourself  on  the  back  of  the  head. 

(a)  What  is  the  *  local  sign  '  of  this  particular  touch  > 

(b)  What  processes  may  be  involved  in  *  local  signature  * 

in  general } 

6.  How  would  you  set  to  work  to  show  that  different  sensa- 
tions proceed  from  skin,  joint,  muscle  and  tendon  ? 

IX 

1.  Define  and  distinguish  carefully  between:  affection,  feel- 
ing, mood,  emotion,  passion,  sentiment,  temperament.  Give  an 
instance  under  each  head. 

2.  How  many  qualities  of  affection  are  there  ?  Support  your 
answer  by  reference  to  introspective  facts. 


426  Appendix  /. 

3.  What  is  the  importance  of  the  reaction  experiment  ? 
Describe  the  apparatus  required  for  it,  giving  a  diagram. 

4.  What  is  meant  by  *  individual  *  psychology  ?  How  is  it 
related  to  psychology  as  a  whole  ?  Are  there  any  other 
branches  or  sub-forms  of  psychology  that  are  of  special  im- 
portance for  general  psychology  ? 

5.  Describe  experiments  for  the  determination  of  the  extent 
and  position  of  the  blind  spot.  Why  is  the  blind  spot  of  im- 
portance psychologically  .^ 

6.  How  would  you  classify  (i)  emotions  and  (2)  the  expres- 
.sions  of  emotion  } 

7.  What  theories  have  been  suggested  of  the  origin  of  the 
aesthetic  sentiment } 

8.  Describe  fully  any  set  of  experiments  that  you  have  made 
during  the  year,  showing  (i)  the  method  employed,  (2)  the 
reasons  for  choice  of  method,  (3)  the  character  of  the  results 
and  (4)  the  value  of  such  results  either  for  psychology  as 
science  or  for  your  own  training. 

X 

1.  Distinguish  between  'action'  and  'movement.'  What 
are  the  two  current  theories  of  the  origin  of  voluntary  move- 
ments }  Who  are  their  prominent  representatives }  Which 
do  you  prefer  ?     Why  } 

2.  What  is  the  technique,  and  what  the  psychological  value 
of  the  simple  sensorial  reaction  }     Illustrate. 

3.  Distinguish  between  idea  and  the  simultaneous  association 
of  ideas.  What  is  the  function  of  the  word-idea  in  the  associa- 
tive consciousness  ^     Give  examples. 

4.  Give  a  psychological  analysis  of  the  simple  judgment. 
What  is  the  place  of  judgment  in  a  scheme  of  the  intellectual 
processes } 

5.  What  is  the  law  of  association  }  How  does  it  differ  from 
the  laws  of  successive  association  formulated  in  the  older  psy- 
chology ?     What  are  these  latter  .? 

6.  To  what  various  analytic  purposes  can  the  reaction  experi- 
ment be  put } 


ExtrntmatWH  Qucsttons  427 

XI 

1.  Give  the  laws  of  colour  mixture. 

2.  Describe  tKe  refractive  media  of  the  eye. 

3.  How  and  why  do  you  see  the  blood-vessels  of  the  retina  } 

4.  How  are  consonance  and  dissonance  of  tones  explained  ? 

5.  Why  do  you  see  two  images  of  the  pin  in  Scheiner's 
experiment  when  the  eye  is  not  properly  accommodated  ? 

XH 

1.  What  reasons  have  led  to  the  assumption  of 
{a)  a  sensation  of  innervation  ; 

{b)  a  sensation  of  muscular  contraction  ? 

2.  State  a  theory  of  visual  contrast. 

3.  Give  some  account  of  psychological  method. 

4.  Discuss  the  following  statements  : 

(a)  "  Awareness  of  change  is  the  condition  on  which  our 

perception  of  time's  flow  depends." — James. 

(b)  "  A  difference  in  the  form  of  the  stimulus,  answering 

to  a  difiference  of  quality  in  the  sensation,  affects  the 

sense-feeling."  —  Sully. 
{c)  "We  cannot  predicate  Intensity  of  visual  sensation." 

—  Kulpe. 
{d)  "  Preyer's  theory  refers  the  cognition  of  direction  to 

the  canals."  —  Miinsterberg. 

XIII 

1.  State  and  discuss  some  definitions  of  psychology. 

2.  How  have  sensations  of  smell  and  taste  been  investigated } 
What  are  the  chief  difficulties  in  their  investigation  } 

3.  What  are  the  mental  elements.^  How  do  you  decide 
whether  a  process  is  elemental  or  not.^  What  differences  of 
opinion  exist  among  psychologists  in  this  matter.^ 

4.  In  what  sense  may  action  be  termed  an  association } 

5.  What  is  meant  by  '  complication  experiments ' }  Describe 
them.     Why  are  they  important } 


428  Appendix  L 

6.  Give  a  theory  of  the  feelings,  naming  its  principal  authoi 
or  authors. 

7.  Explain  the  following  terms  and  phrases  : 

(a)  Sensation  of  difference. 
(d)   Original  similarity. 
(c)    Recognition. 
{d)  Consciousness. 

XIV 

1.  How  does   the    method    of    psychology  differ  from    the 
methods  of  the  physical  sciences  ? 

2.  Analyse  the  experiences  of  hardness,  smoothness,  impact, 
resistance  and  sharpness  into  their  lowest  conscious  terms. 

3.  Give  a  theory  of  the  pressure  sense. 

4.  What  are  the  functions  of  the  semicircular  canals  of  the 
internal  ear.? 

5.  State  a  method  for  the  investigation  of  the  articular  sen- 
sitivity. 

6.  What  is  meant  by  the  *  association  of  ideas  * }     What  light 
does  its  study  throw  upon  the  constitution  of  mind } 

7.  What  sensation  arises  when  one  looks  at  running  water, 
over  a  precipice,  etc. }     Why  } 

8.  Why  should  a  cold  weight  seem  to  be  heavier  than  a  warm 
weight  of  the  same  objective  heaviness? 

XV 

1.  What    problems    does    *  memory '    present    to    the    psy- 
chologist } 

2.  Discuss  the  possibility  of  an  affective  memory-type. 

3.  Explain  :   unity  of  consciousness,   imagination  mark,   re- 
cept,  aggregate  idea,  golden  section. 

4.  What  is  the  psychological   basis   of   the  aesthetic   senti- 
ments } 

5.  Define  the  place  of  the  reaction  experiment  in  a  system 
of  psychology. 

6.  Give  the  theory  of  psychophysical  parallelism. 


ExamimitwH  Questioms  429 

7  Wha.  .wo  types  of  action  have  been  regarded  as  primi- 
tive ?  Which  type  does  the  psychologist  advocate,  and  for  what 
reasons? 

8.  Give  a  schema  of  the  development  of  action.  Give  a 
concrete  illustration  of  each  type  in  the  schema. 

9.  How  would  you  find  the  time  occupied  by  the  purely 
associative  processes  in  an  association  reaction }  What  sug- 
gestions can  you  make,  as  regards  technique  and  computation 
in  such  an  experiment  ? 

XVI 

1.  Define:  perception,  state  of  consciousness,  mental  con- 
stitution. 

2.  Name  the  three  forms  of  attention.  Trace  their  growth, 
showing  the  conditions  under  which  they  have  developed. 
What  are  the  characteristics  of  the  attentive  consciousness? 
Do  these  characteristics  differ  in  the  three  different  forms  of 
attention,  or  are  they  the  same  in  all  forms?  What  is  the 
importance  of  the  different  forms  of  attention  in  the  mental 
life  of  man? 

3.  Discuss  the  perception  of  rhythm,  showing  what  psycho- 
logical problems  are  involved. 


APPENDIX   II 
Books  and  Periodicals 

The  student  should  be  taught  to  connect  the  facts  of  experi- 
mental psychology  with  the  names  of  their  discoverers  :  so  that 
the  idea  of  '  temperature  spots '  shall  be  associated  with  the 
names  of  Blix,  Donaldson  and  Goldscheider,  —  the  *  paradoxical 
sensation  of  cold*  with 'that  of  von  Frey, — the  *  fusion  quality 
of  heat '  with  that  of  Alrutz,  etc.,  etc.  Something  should  be 
known  of  the  life  and  work  of  these  investigators,  and  their 
original  monographs  should  be  read  (or,  at  least,  handled  and 
glanced  through,  the  plates  studied,  etc.)  wherever  practicable. 
Even  in  an  elementary  Course,  the  student  may  be  given  in- 
formation about  the  geographical  distribution  and  historical 
development  of  the  science  that  will  prove  of  great  value  to 
him  in  later  work. 

The  buying  of  books  for  oneself,  the  formation  of  a  private 
library,  should  also  be  encouraged.  If  the  student  will  spend 
even  so  small  a  sum  as  $  i  a  month,  he  will  have  at  the  end  of 
three  years  the  nucleus  of  a  working  library. 

For  the  school  or  college  library,  the  following  periodicals  are 
essential : 

(i)  VAnn^e  psycJiologique.  Edited  by  A.  Binet,  with  the 
collaboration  of  H.  Beaunis  and  T.  Ribot.  1895.  Bib- 
liography from  1894. 

(2)  Philosophische    Stiidien.       Edited    by    W.    Wundt.       1881. 

Contains  the  work  done  in  the  Leipzig  laboratory. 

(3)  The  American   'Journal  of  Psychology.      Edited    by   G.    S. 

Hall,  E.  C.  Sanford  and  E.  B.  Titchener.      1887. 

(4)  The  Psychological  Review.     Edited  by  J.  M.  Baldwin  and 

J.  McK.  Cattell.     1894.     Bibliography  (sold  separately) 
from  1894. 

430 


Books  and  Periodkals  431 

(5)  Zeitschriftfur  PsyckologU  und PkysUlogU  dtr  Sinmsorgam, 
Edited  by  H.  Ebbinghaus  and  A.  Konig.  1890.  Bibliog- 
raphy from  18S9. 

Many  of  the  volumes  of  these  periodicals  extend  over  a  longer 
period  than  one  year.  Thus  the  first  volume  of  the  Philos. 
Studien  is  dated  1883,  but  the  parts  extend  from  1881  to  1883. 
The  author  has  sought,  wherever  possible,  to  date  the  articles 
cited  in  the  text  by  the  year  of  their  part  on  number,  rather 
than  by  that  of  their  volume. 

The  following  are  the  50  books  that,  in  the  judgment  of  the 
author,  will  prove  most  useful  to  students  taking  this  Course. 

1.  H.  Aubert,  GrundzUge  dcr  physiologischen  Optilc.     Leipzig,  W.  Engel- 

nuuin.     1876. 

2.  A.  Bain,  The  Senses  and  the  Intellect.     3d  edn.     London,  Longmans, 

Green  &  Co.     1868. 

3 .  A.  Bain,  The  Emotions  and  the  Will.     3d  edn.     London,  Longmans, 

Green  &  Co.     1880. 

4.  J.  M.   Baldwin,  Mental    Development   in   the   Child  and    the    Race, 

^fethods  and  Processes.    2d  edn.    New  York,  The  Macmillan  Co. 
1899. 

5.  F.  Brentano,  Psychologie  vom  empirischen  Standpunkte.     Vol.  i.     Leip- 

zig, Duncker  &  Humblot.     1874. 

6.  H.  Ebbinghaus,  Grundzligeder  Psychologie.    Erster  Halbband.    Leipzig, 

Veit  &  Comp.     1897. 

7.  G.  T.  Fechner,  Elemente  der  Psychophysik.     2d  (unchanged)  edn.     2 

vols.     Leipzig,  Breitkopf&  Hartel.     1889. 

8.  M.   von  Frey,  Ueber  die  Sinnesfunctionen  der  menschlichen  Haut.  i. 

Druckempfindung  und  Schmerz.     Leipzig,  S.  Hirzel.     1896. 

9.  F.  Gallon,  Inquiries  into  Human  Faculty  and  its  Development.    London, 

Macmillan  &  Co.     1883. 

10.  A.  Goldscheider,  Gesammelte  Abhandlungen.     2  vols.     Leipzig,  J.  A. 

Barth.      1898. 

11.  U.  L.  F.  von  Helmholtz,  Handbuch  der  physiologischen  Optik.     2d  edn. 

Hamburg  and  Leipzig,  L.  Voss.     1896. 

12.  H.  L.  F.  von  Helmholtz,  On  the  Sensations  of  Tone  as  a  Physiological 

Basis  for  the  Theory  of  Music.    Translated  by  A.  J.  Ellis.     3d  edn. 
London  and  New  York,  Longmans,  Green  &  Co.     1895. 

13.  V.  Henri,  Ueber  die  Raumwahmchmungen  des  Tastsinncs,  ein  Bcitrag 

zur  experim^Titi'llpn    P>ivrhologic.      Berlin.    Reuther   &    Reichard. 

1898. 

14.  E.  Hering,  beiirage  zur  i'nysiologic.     Leipzig,  W.  JLugelmann.     1861- 

1864. 


432  Appendix  II. 

15.  E.    Hering,  Die  Lehre  vom  binocularen   Sehen.     Leipzig,  W.  Engel- 

mann.     1868. 

16.  E.  Hering,  Zur  Lehre  vom  Lichtsinne.     Wien,  C.  Gerold's  Sohn.     1878. 

17.  E.  Hering,  Der  Raumsinn  und  die  Bewegungen  des  Auges.     In  L.  Her- 

mann's Handbuch  der  Physiologic,  iii.,  i,  343-601.  Leipzig,  F.  C. 
W.  Vogel.  1879.  (This  Part  contains,  also,  A.  Kick's  Lehre  von 
der  Lichtempfindung.) 

18.  H.  Hoffding,  Outlines  of  Psychology.     Trans,  by  M.  E.  Lowndes.     Lon- 

don and  New  York,  Macmillan  &  Co.  1891.  2d  German  edn.^ 
1893. 

19.  A.  Hofler,  Psychologic.     Wien  and  Prag,  F.  Tempsky.     1897. 

20.  A.  Hofler  and  S.  Witasek,  Psychologische  Schulversuche,  mit  Angabe 

der  Apparate.     Leipzig,  J.  A.  Barth.     1900. 

21.  W.  James,  The  Principles  of  Psychology.     2  vols.     London,  Macmillan 

&  Co. ;  New  York,  H.  Holt  &  Co.     1890. 

22.  O.  Kulpe,  Outlines  of  Psychology,  based  upon  the  Results  of  Experi- 

mental Investigation.  Trans,  by  E.  B.  Titchener.  London,  Swan 
Sonnenschein  &  Co. ;  New  York,  Macmillan  &  Co.     1895. 

23.  G.  T.  Ladd,  Psychology,  Descriptive  and  Explanatory,  a  Treatise  of  the 

Phenomena,  Laws  and  Development  of  Human  Mental  Life.  New 
York,  Charles  Scribner's  Sons.     1894. 

24.  O.  Langendorff,  Physiologische  Graphik,  ein  Leitfaden  der  in  der  Phy- 

siologic gebrauchlichen  Registrirmcthoden.  Leipzig  and  Wien,  F. 
Deutickc.     1891. 

25.  A.  Lehmann,  Die   Hauptgesetze  des  menschlichen  Gefuhlslebens,  cine 

experimcntelle  und  analytische  Untcrsuchung  iiber  die  Natur  und 
das  Auftretcn  der  Gefiihlszustande  nebst  cinem  Beitrage  zu  deren 
Systcmatik.     Leipzig,  O.  R.  Reisland.     1892. 

26.  A.  Lehmann,  Die  korpcrlichen  Aeusserungen  psychischer  Zustandc.     I. 

Plethysmographische  Untersuchungen.  Leipzig,  O.  R.  Reisland. 
1899.     With  atlas  of  68  plates;  Kopenhagen,  1898. 

27.  T.  Lipps,  Grundtatsachen  des  Seelenlebens.     Bonn,  M.  Cohen  u.  Sohn. 

1883. 

28.  T.  Lipps,  Raumaesthetik  und  geometrisch-optische  Tauschungen.     Leip- 

zig, J.  A.  Barth.     1897. 

29.  R.   H.    Lotze,   Medicinische   Psychologic   oder  Physiologic  der  Seelc. 

1852.     Reprinted,  1896.     L.  Horstmann,  Gottingen. 

30.  E.  Mach,  Contributions  to  the  Analysis  of  the  Sensations  [1886].    Trans. 

by  C.  M.  Williams.     Chicago,  Open  Court  Publ.  Co.     1897. 

31.  A.  Mosso,  Fear.     Trans,  by  E.  Lough  and  F.  Kiesow.     London,  Long- 

mans, Green  &  Co.     1896. 

32.  A.  Munsterberg,  Beitrage  zur  cxperimcntcllen  Psychologic.    Freiburg  i.  B., 

J.  C.  B.  Mohr.     1889-1892. 

33.  T.  Ribot,  Psychologic  dc  Tattention.     Paris,  F.  Alcan.     1889.     Trans., 

Open  Court  Publ.  Co.,  Chicago,  111.     1896. 


Books  and  Periodicals  433 

34.  E.  C.  Sanibrd,  A  Course  in  Experimental  Psychology.    Pt.  i.    Sensation 

and  Perception.    Boston,  U.  S.  A.,  D.  C.  Heath  &  Co.     1898. 

35.  E.  W.  Scripture,  The  New  Psychology.    Cont.  Sd.  Series,  xxxiii.     Lon- 

don. Walter  Scott,  Ltd. ;  New  York,  Charles  Scribnef  s  Sons.     1897. 
:6.   L.  W.  Stem,  Ueber  Psycbologie  der  individuellen  Diflferenzen,  Ideen  zu 

einer  *  differentieUen  Psychoiogie.'     Leipzig,  J.  A.  Barth.     1900. 
;7.  G.  F.  Stout,  Analytic  Psychology.    3  vols.    London,  Swan  Sonnenschein 
•    &  Ca ;  New  York,  Macmillan  &  Co.     1896. 

38.  C.  Stumpf,  Tonpsychobgie.    2  vols.     Leipzig,  S.  Hirzel.     1883,  1890. 

39.  C.  Stumpf,  Ueber  den  psychologischen  Ursprung  der  Raumvorstellung. 

Leipzig,  S.  Hirzel.     1873. 

40.  J.  Sully.  The  Human  Mind,  a  Text-book  of  Psychology.    2  vols.    London, 

Longmans,  Green  &  Co.     1893. 

41.  E.  B.  Titchener,  An  Outline  of  Psychology.    3d  edn.     London,  Mac- 

millan &  Co. ;  New  York,  The  Macmillan  Co.  1899. 
43.  M.  von  Vintschgau,  Physiologic  des  Geschmackssinns  und  des  Geruchs- 
sinns.  In  L.  Hermann's  Handbuch  der  Physiologic,  iii.,  i,  145-286. 
Leipzig,  F.  C.  W.  Vogcl.  1880.  (This  Part  contains  also  V.  Hen- 
sen*s  work  on  hearing,  O.  Funke's  on  touch  and  common  sensation, 
and  E.  Hering's  on  the  temperature  sense.) 

43.  J.  Ward,  Psychology.    Encyd.  Brit.,  9th  edn.,  pt  77.    Edinburgh,  A.  &  C. 

Black.     1886. 

44.  E.  H.  Weber,  Der  Tastsinn  und  das  GemeingefUhl  [1846].     Published 

as  off-print  from  R.  Wagner's  Handworterbuch  der  Physiologic,  1851. 

45.  W.  Wundt,  GrundzUge  der  physiologischen  Psychologic.    4th  edn.,  2  vols. 

Leipzig,  W.  Engelmann.     1893. 

46.  W.  Wundt,  Lectures  on  Human  and  Aninud  Psychology.     Trans,  by 

J.  E.  Creighton  and  E.  B.  Titchener.  2d  edn.  London,  Swan 
Sonnenschein  &  Co. ;  New  York,  The  Macmillan  Co.  1896.  Third 
German  edn.,  1897. 

47.  W.  Wundt,  Outlines  of  Psychology.    Trans,  by  C.  H.  Judd.     2d  edn. 

Leipzig,  W.  Engelmann ;  London,  Williams  &  Norgate ;  New  York, 
G.  E.  Stechert.     1898.     Third  German  edn.,  1898. 

48.  W.  Wundt,  Die  geometrisch-optischen   Tauschungen.     Leipzig,  B.  G. 

Teubner,  1898. 

49.  T.  Ziehen,  Introduction  to  Physiological  Psychology.     Trans,  by  C.  C. 

van  Liew  and  O.  W.  Beyer.  2d  edn.  London,  Swan  Sonnenschein 
&  Co.;  New  York, The  Macmillan  Co.  1895.  Fifth  German  edn., 
1900. 

50.  A.  Zwaardemaker,  Die  Physiologic  des  Geruchs.     Leipzig,  W.  Engel- 

ntann.      1895. 


APPENDIX   III 

Firms   Recommended   for   the   Supply   of   Psychological 

Instruments 

The  Instructor  should  secure  the  catalogues  and  price-lists 
of  the  following  firms,  —  and  of  as  many  more  as  possible. 
A  good  collection  of  trade  catalogues  is  indispensable  to  the 
economical  conduct  of  a  laboratory. 

1.  M.  Bradley  Co.,  Springfield,  Mass.    (Coloured  papers,  rings, 

etc.) 

2.  J.  Brandli,  59  Freie  Strasse,  Basel.      (Griesbach's  instru- 

ments.) 

3.  Cambridge    Scientific    Instrument    Co.,    St.    Tibb's    Row, 

Cambridge.  (Optical  and  acoustical  pieces  ;  Galton's 
instruments.) 

4.  Clark  University  Laboratory,  Worcester,  Mass.    (Sanford's 

instruments.) 

5.  Chicago  Laboratory  Supply  and  Scale  Co.,  31-45  W.  Ran- 

dolph Street,  Chicago,  111.  (General  supplies  ;  Jastrow's 
instruments  ;  certain  of  the  instruments  recommended 
in  the  text.) 

6.  Collin,    6   Rue   de   I'Ecole   de    M^decine,    Paris.      (Dyna- 

mometers, etc.) 

7.  Columbia  University  Laboratory,  New  York  City.     (Cat- 

tell's  instruments.) 

8.  C.  Diederichs,  Gottingen.     (Miiller's  instruments.) 

9.  Eimer  and  Amend,   205  Third  Avenue,  New  York  City. 

(Chemicals ;  glassware.) 

10.  H.  Elbs,    17  Friedrichstrasse,   Freiburg  i.   B.      (Miinster- 

berg's  instruments.) 

11.  J.   H.    Harting-Bank,    Utrecht.      (Zwaardemaker's    instru- 

ments.) 

434 


Psychological  Instrument  Makers  435 

12.  R,  Jung,  Heidelberg.     (Helmholtz*  instruments.) 

13.  D.    B.    Kagenaar,    Utrecht.      (Instruments    by    Donders, 

Snellen,  Engelmann,  Zwaardemaker.) 

14.  R.  Koenig,  27  Quai  d'Anjoii,  Paris.     (Acoustical  instru- 

ments :    Helmholtz,  etv 

15.  M.  Kohl,  51  Poststrasse,  Chemnitz  i.  S.    (General  supplies; 

optics,  acoustics.) 

16.  F.  Majer,   10  Kramergasse,  Strassburg  i.   Els.     (Kwald's 

instruments.) 

17.  E.  B.  Meyrowitz,  104  E,  23  Street,  New  York  City.  (Optics, 

acoustics.) 

18.  Michigan   Apparatus   Co.,   305   South  Main  Street,   Ann 

Arbor,  Mich.  (Lombard's  and  Pillsbury's  instru- 
ments.) 

191  Moore  &  Moore,  105  Bishopsgate  Street,  London,  E.  C. 
(Ellis'  harmonical.) 

la  W.  Petzold,  13  Bayersche  Strasse,  Leipzig.  (Physiological 
instruments:  Ludwig,  von  Kries,  etc.) 

21.  Prang  Educational  Co.,  7  Park  Street,  Boston,  Mass.    (Spec- 

trum chart ;  coloured  papers.) 

22.  Queen  &  Co.,  loio  Chestnut  Street,  Philadelphia,  Pa.  (Gen- 

eral supplies ;  optics,  acoustics.) 

23.  R.    Rothe,    16  Liebigstrasse,    Leipzig.      (Hering's   instru- 

ments.) 

24.  W.  Schmidt,  Seltersweg  30,  Giessen.     (Sommer's  instru- 

ments.) 

25.  H.  Sumner,  Cambridge,  Mass.     (Bowditch's  instruments.) 

26.  C.  Verdin,  7  Rue  Linn^,  Paris.    (Physiological  instruments  : 

Marey,  Mosso,  etc.) 

27.  Yale  University  Laboratory,  109  Elm  Street,  New  Haven, 

Conn.    (Scripture's  instruments.) 

28.  Ziegler  Electric  Co.,  141   Franklin  Street,  Boston,  Mass. 

(General  supplies:  optics,  acoustics.) 

29.  E.   Zimmermann,  21    Emilienstrasse,  Leipzig.     (Wundt's 

instruments.) 


LIST  OF  MATERIALS 


See  Part  U  pp.  207  ft 


I.  SPECIAL  APPLIANCES 


i£nhetk)meto,  Gfktbach*a,  38a.  I  Hannonicas,  7a,  330. 

After-ioMge  apparatua,  44:    Franz',  44;  <  Harmonium,  72,  79,41a 

Wondt's,  50;  Hehng't,  50;  Scripture's,    Head-rest,  245,  255. 

412. 
Analyaer,  tridimensional,  Sommer's,  161  f. 
Arm-rest,  145.  170. 
Antomatograph,  158;  Jastrow's,  159, 162; 

Sommer's,  161 ;  Delabarre's,  162. 


let,  17;  Hering's,  20,  23. 

Colour  blindness,  Hering's  test  for,  7. 

Colour  mixer,  9,  17:  spectroscopic,  14, 
16;  mixture  by  juxUposition,  14:  Lam- 
bert's, 14  f.;  Hering's,  16,  20;  Marbe's, 
17;   Hering's  binocular,  29 1. 

Complication  pendulum,  206  f. 

Contrast  iMtniments,  Hering's,  36  t 


Diaphragm,  Aubert's,  44. 

Dynamograpb,  167. 

Djroamometer,  finger,  147;  hand,  167. 

Electrodes,  97  f. 

Ergograph,  Moiio's,  170;  CatteU's,  170; 
Btaet  and  Vaachkle's,  170  f. 


Fall-chronometer,  Wundt's  demonstration, 

201;  CatteU's,  201. 
Ftnger-moremeot   recorder,  Delabarre's, 

162. 

Haploacope,  Hering's,  265,  27a 
Harmonical,  Ellis',  52,  79  f. 


Inductorium,  97  f.,  144, 197, 371;  Preyer** 
double,  371. 

Jacquet's  chronometer,  1 78. 

Key,  pneumatic  reaction,  196  f. 
Kymograph,  172  f.,  195. 

Marey  tambour,  1 76  f. 
Memory  apparatus,  Jastrow's,  405. 
.Metronome,  193,  338  f.,  351  f.;  with  bell, 
205  f. 

Olfactometer,  Zwaardemaker's  fluid-man« 

tie,  142. 
Organ  pipes,  72,  371. 


Pain  apparatus:    horse-hairs,  94;    hog's 
bristles,  94  f.;  fine  needle,  94  t 

Perimeter,  Wundt's,  26. 

Phacoscope,  Helmholtz',  236 

Phonograph,  413. 

Piano,  78  ff. 

Pitch  pipe,  Ellis'  double,  61. 

Plethysmograph,  Franck's,  180  f.;  Lom- 
bard and  PUbbury's,  183. 

PDeomograph,  Verdin's,   184;  Sumner*!, 
184. 
437 


433 


List  of  Materials 


Pseudoscope,  Wheatstone's,  295  ff.,  298; 
Dove's,  295;  Ewald's,  297;  Stratton's, 
297;  Jastrow's  (perspectoscope),  298; 
Wood's,  299. 

Psychodometer,  Obersteiner's,  227. 

Quincke's  tubes,  66,  68,  72. 

Resonators,  Appunn's,  77;    Helmholtz', 

77;  Kcenig's,  77,  80. 
Rhythm  apparatus,  349;  Bolton's,  338. 

Savart  wheel,  52. 

Sonometer,  76,  80. 

Sound  cage,  358  f. ;   Matsumoto's,  359. 

Sound  helmet,  Preyer's,  359. 

Sphygmograph,  von  Frey's,  183. 

Sphygmomanometer,  Mosso's,  182. 

Stereoscopes,  early,  of  Wheatstone's  de- 
vising, 261;  Wheatstone's  reflecting, 
263  f.,  265;   Brewster's  refracting,  268 


f.;  various  devices  of  Brewster,  271 ; 
converting,  Dove's,  295;  Jastrow's  (per- 
spectoscope), 298. 

Tachistoscopes,  2CX)  ff .,  41 1 ;  Wundt's,  201 ; 
Cattell's,  201;  Goldscheider  and  Mai- 
ler's, 201 ;   Erdmann  and  Dodge's,  204. 

Telephone  receivers,  371. 

Telestereoscope,  Helmholtz',  265,  271  f. 

Temperature  apparatus,  for  keeping  water 
at  a  constant  warmth,  83;  Blix',  84; 
Cattell's,  84. 

Time-markers,  178  f.,  197. 

Time-sense  apparatus,  Meumann's,  338. 

Tonometer,  Appunn's,  80. 

Tropostereoscope,  Ludwig's,  272  f. 

Tuning-forks,  55,  61,  80,  332,  369  ff. 

Vernier  chronoscope,  Sanford's,  212  f.; 
attachments  to,  223  ff. 

Window,  Hering's,  36  C 


II.    GENERAL   APPLIANCES   AND    MATERIALS 


Alcohol  lamp,  132. 

Arm    photograph,    or    plaster    of    Paris 
model,  374. 

Bicycle  whistle,  double,  72. 

Brass  T-way,  371. 

Brass  wire  with  cotton  wad,  132. 

Brushes,  camel's-hair,  for  taste  work,  100. 

Bunsen  burner,  197. 

Candle  or  lamp,  234  f. 
Cells,  Leclanche,  97. 
Concertina,  72. 

Corks,   covered,   81;    for  Scheiner's   ex- 
periment, 237. 

Ear  plug,  364. 

Felt  hammers,  55. 

Field  of  regard,  Sanford's  model  of,  250. 
Flat  spring,  wooden  cap  and  pin,  226. 
Foot  bellows,  371. 


Gauze,  wide-meshed,  1 14. 
Gong,  224. 

Hard-rubber  syringes,  163,  225. 

Kymograph  paper,  173. 

Lenses,  for  irregular  astigmatism,  240. 

Metronome  box,  347. 

Mirror,  386. 

Mouth  board  with  sighting  mark,  245. 

Needle,  fine,  85,  94  f. 

Paper  funnel,  118. 

Petroleum  smoking  lamp,  1 73  £ 

Prism,  9. 

Resonance  jars,  55. 
Rheostats,  371  f. 


List  of  Materials 


439 


Riofi,  meteU  292. 

Rod,  wooden,  ptdded  at  iowcr  end,  359. 
Robber  tobiai^   13a,  177  U  s^St  3<^ 
37«. 

Scalpel,  17$. 

Smoking  stand,  1 73  t 

Stand  for  apare  kymograph  dnim,  174. 

Standards,  bates,  anna  and  dampa,  179. 

Thistle-tiabe  and  rubber  bolb,  135. 
Tin  funnel,  132. 


Txn  sliders,  33a 
Tins  or  cups,  133. 
Toy  snapper,  359. 
Toy  trumpet,  73. 

Varnishing  tray  and  drying  rack,  175  C 
Violin,  72. 


Watch.  194.  197. 

Wire  models,  for  optical  Olusiona,  309^ 

Writing-lereri,  177. 


III.   PAPER,   DRAWING   MATERIALS,   ETC. 


Asttgmatisai  figure,  241. 

Card,  white,  tipped  with  black  disc,  27; 
for  Scheiner*s  experiment.  237;  black, 
with  white  disc,  for  chromatic  aberra- 
tion, 239;  black,  with  pin-hole,  for 
trr^ttlar  astigmatism,  240;  red,  for 
Listing's  screen,  245 ;  white,  with  three 
pin-holes,  255;  for  artificial  pinnae,  369. 

Csfds,  for  blind  spot.  i&  ff. 

Cards,  object,  for  associative  supplement- 
ing, 412. 

Cards,  stimulus,  for  work  on  association, 
405  f. 

Cards,  test,  for  work  on  association,  406. 

ChaSk,  194.  359. 

Chrome  alum,  solution  of,  30. 

Disc,  Masson's,  197. 

I>isc,  pierced,  193. 

I>iscs,  fur  rhythm  apparatus,  35a 

Discs.  Hclmholt/'  contrast,  37. 

•  'elatine  discs,  15;  sheets,  44. 
'lass,  cobalt-blue,  239,  242;  and  papers 
for  Wandt*s  mirror  experiment,  285. 

I>etter  squares  and  blanks,  396  C,  398, 399  f. 
letters  and  numerals,  gummed,  406. 

'■IcUi;  r.»fi,  253. 

Mm.  paper  scale,  17. 


I  Movable    model   of    Mflller-Lycr    figure, 
309. 

Paper,  cross-ruled,  154. 

Paper,  white,  27;  white  tissue,  32*.  white 

baryta.  42;    black  and  red,  with  blue 

thread,  252. 
Papers,   coloured.    7,   9,    14,    151.    154; 

Wundt's.  10,  II,  12;    Hering's.  19,  20, 

32,  Zl»  34  f.;    MUton  Bradley's,   155, 

157.406. 
Papers,  grey,  32. 
Pseudoptics,    MQnsterberg's,  xxxiii.,   260, 

309. 
Puzzle  pictures,  19a 


Rings,  von  Bezold's,  240. 

Screens,  black  and  white,  for  Scheiner's 
experiment,  237;  black,  with  slit,  for 
chromatic  al)erration,  239;  for  Donders' 
and  Listing's  laws,  245  f..  248. 

Screens,  Hering's  grey,  20,  23. 

Sealing  wax,  red,  7. 

Slides,  stereoscopic,  of  glays  or  celluloid, 
260;  for  Wheatstone  stereoscope,  267; 
list  of,  for  laboratory  work,  273  f.; 
illustrations  of,  274  ff.,  287  f. 

Spectrum  chart,  7. 

Tubes,  stereoscopic,  260;  blackened, 
392. 


440 


List  of  Materials 


IV.  SMELL  AND  TASTE   SOLUTIONS,  ETC. 


Beeswax,  120. 

Carbolic  acid,  solution  of,  132. 

Cocaine  hydrochlorate,  103. 

Cylinders,  olfactometries  119  C,  I3l»  139. 

Eye,  white  rabbit's,  233. 

Gum  benzoin,  121. 

Gymnemic  acid,  alcoholic  solution  of,  104. 

Homatropinum  hydrobromicum,  solution 
of,  199. 


Listerine,  132. 

Oil  of  cloves,  115,  120. 

Smell  stimuli,   113,   121,   122  f.,  124  ff., 

127  f.,  131,  137  f.,  139,  160,  169. 
Soap,  85. 

Taste  stimuli,  105,  163. 

Water,  warm,  85,  95. 
Wax,  laboratory,  56. 


V.    LABORATORY   FURNITURE 
Chair,  cane-bottomed,  262.  I  Desk,  skeleton  standing,  39. 


INDEX  OF   NAMES 


TUt  Vitk  does  not  repeat  the  namet  contained  in  the  bibliography  of  th« 
Geometrical  Optical  IHusioni,  pp.  305  ff. 


Calkina,  M.  W.,  403  f.,  406  ff..  409  f., 
4«5.4ao. 

CattelU  J.  McK.,  xxr^  84,  170^  aoi,  203, 
308.225  f.  415.430. 

Charcot,  J.  M.,  387. 

Chaq>enlier,  A..  39.  46. 

Cohn,  J..  154.  158.  393,  400. 
136.    Coolc.  H.O..  aoo. 

Courtier.  J,  171. 
232,   Crawford,  J.  F..  87. 
286,   Czermak,  J.,  375,  386. 


Darwin.  C.  R.,  390. 

Dearborn,  G.  van  N.,  162. 

Deifner,  K.,  55. 

Delabarre,  E.  B.,  143,  162. 

Delboeuf,  J.,  3«5»  3*1  f-,  325. 

Dessoir.  M.,  422. 

Dietze.  G.,  346. 

Dodge.  R..  203  f..  391.  394* 

DoUey.  C.  S..  225  f. 

Donaldson,  H.  H.,  87,  94,  378. 

Donders,  F.  C,  242  f. 

Dove,  H.  W.,  200,  287,  294  f.,  371. 

Downey,  J.  E.,  401. 

Drenlar,  F.  B.,  382. 

Drobisch,  M.  W.,  55. 

Ebbinghaus,  H.,  xxvi.,  5, 6  f..  16.  36,  38  f.. 

43.  45,  48,  51,  54  r.  57.  72,  76.  188. 

420,  422,  431. 
Ebhardt,  K.,  352. 
Eckener,  H.,  195,  1980: 
Einthoven.  W.,  321  f..  324  ft,  327  L 
Elliot,  J.,  260. 

Ellia,  A.  J.,  52,  54,  61,  68,  79  f. 
Erb,  W.,  146.  148. 
Erdmann,  B.,  203  f. 
Ettlinger,  M..  356. 
Ewald.  J.  R.,  297. 
Exner.  S.,  55,  201. 


N,  214,  225. 

AlliB,A^404. 

Alnrti,  S.,  91. 

AngeD.  J.  IL,  185,  207,  225.  346^ 

AppoBB,  A^  8a 

Ar«U)Ue,  383  f^  386.  425. 

AnoBrtroiig,  A.  C,  393. 

AroMohn,  E^  121.  125, 127, 130. 133, 

Aflchaffeaborg.  G..  394. 415 1 

Aubefft.  H.,  5.  30,  37  ff^  43  f.,  46  f.. 

237.  247.  H9  ffn  252,  262,  269, 

293  f-  43«- 
Auerbach.  F^  322,  328. 
ATenarios,  R^4ii. 

Begley,  W.  C,  385,  413. 

Bain.  A^  256.  404,  431. 

Baldwin,  J.  M..  225, 385,  387, 430  f. 

Earth,  A..  51. 

Bastian,  H.  C,  144,  148. 

Baxt,  N..  201. 

Beaimia,  H.,  143.  430- 

BcBtley,  I.  M.,  226,  258.  300.  395. 

BergMrSm,  J.  A^  420. 

Beiold,  W.  voD,  240. 

BidwdU  S.,  39.  46. 

Biaet,  A..  170  f..  177.  182.  185.  385. 

39«.  393.  396,  .99.  40i  f.,  430. 
BUa,  M^  84,  86  f. 
Bokon,  T.  L^  xxvii.  f.,  199,  J3!&  (L, 

344,  346  ff^  349  «:,  354  ff. 
Bonnet,  C^  188. 
BoMcha,  H.  P.,  39. 
Bonrdon,  B.,  391,417. 
Bndley.  F.  H.,  55. 
Braonschweiger,  D.,  186  f. 
Brentano,  F.,  321  U  327  U  43>* 
BKwatcr,  D^  255,  260  f.,  263, 268  fL, 

a93t 
Breno€,C323. 
B^ich.  E^  329,  333. 
BoBfcltR.,  104. 


387. 


342, 


27«. 


441 


442 


Index  of  Names 


Faist,  A.,  333  ff.,  336  f. 
Fechner,  G.  Th.,  37  f.,  43,  49,  150,  191  f., 
194,  199,  209.  284,  290,  362,370  f.,387, 

389.  393  U  421,  43»- 
Fere,  C,  401. 
Fick,  A.,  5,  39,  118,  232,  239,  241,  252, 

421,432. 
Fick,  A.  E.,  39. 
Flournoy,  Th.,  225. 
Foster,  M.,  5,  51,  82,  99,  114,  143,  233  f., 

242,  252,  255. 
Franklin,  C.  L.,  5,  45,  421. 
Franz,  S.  I.,  44,  49  f. 
Fraser,  A.,  401. 
Frey,  M.  von,  81,  86  f.,  94,  95  ff.,  183, 185, 

43>- 
Friedrich,  M.,  205. 
Funke,  O.,  82,  143, 433. 

Gale,  H.,  iii. 

Gallon,  F.,  387  ff.,  390  ff.,  393,  395,  404, 

431. 
Gamble,  E.  A.  McC,  112,  131,  133,  393. 
Gerling,  C.  L.,  233. 
Glazebrook,  R.  T.,  294. 
Goldscheider,  A.,  82,  87,  91,  94,  97,  in, 

143,  145  ff.,  201,  203  f.,  378,  380,  383, 

411,422,431. 
Grassmann,  H.,  16. 
Griesbach,  H.,  382. 
Gurber,  A.,  39. 

Hall,  G.  S.,  94,  378,  387,  430. 

Hamlin,  A.  J.,  157,  189,  192. 

Heinrich,  W.,  200. 

Heller,  T.,  401. 

Helmholtz,  H.  L.  F.  von,  5,  7,  16,  21,  26, 
28,  30,  36  ff.,  43,  45  ff.,  51  f.,  54  ff.,  61, 
64,  66,  68,  72,  75  ff.,  79  f.,  81,  187,  191, 
198,  200  f.,  211,  232  ff.,  235  f.,  238  ff., 
241  ff.,  244  ff.,  247, 249  ff.,  252  ff.,  255  ff., 
260,  262,  267,  269  ff.,  272,  274,  279, 
284,  286,  289,  291  ff.,  294  f.,  421  f., 

431. 
Henle,  J.,  346. 
Henri,  V.,  144,  148,  171,  182,  185,328, 

374  f-»  377.  381  f.,  386,  399.  431- 
Hensen,  V.,  51,  55,  422,433. 
Herbart,  J.  F.,  186,  404. 
Hering,  E.,  xxi.,  5,  6  f.,  8,  10,  15  f.,  19  ff., 

26,  30  ff.,  36  ff.,  43,  45,  49  f.,  81  f.,  129, 


211,  234,  242  ff.,  246  f.,  248  ff.,  251  ff., 
254  f.,  256  f.,  259,  265,  267,  269  ff, 
273  f.,  276,  278,  280,  283  f.,  289  ff.,  292, 

294  U  375. 421,  431  ff. 

Hermann,  L.,  72. 

Hess,  C,  26,  36,  38,  46. 

Heymans,  G.,  321  f.,  324  ff.,  327  f. 

Hillebrand,  F.,  265. 

Hobbes,  T.,  404. 

Hoffding,  H.,  418,  432. 

Hofler,  A.,  xxvi.,  xxxiii.  ff.,  51,  55,  187  f., 

255,  292  f.,  369,  372,  391,  432. 
Hofmann,  F.,  104. 
Holmes,  O.  W.,  269. 
Howe,  H.  C,  416. 

James,  W.,  xxvi.,  37,  55,  150,  187,  208  ff., 
227, 302,  355,  375,  378,  387,  389  ff.,  394, 
401,  404,  427,  432. 

Jastrow,  J.,  162,  207,  298  f.,  327  f.,  405. 

Jerusalem,  W.,  417. 

Judd,  C.  H.,  375  ft,  378,  380,  382  f. 

Kaiser,  F.,  213. 

Kessel,  J.,  369.  » 

Kiesow,  F.,  86  f.,  94,  98,  99  f.,  104,  184. 

Kirschmann,  A.,  26,  36,  44. 

Koenig,  A.,  431. 

Koenig,  R.,  73,  77,  80. 

Kohn,  H.  E.,  187,  210. 

Kraepelin,  E.,  394,  415 

Kries,  J.  von,  5,  39,  368,  371,  421. 

Kroner,  E.,  143. 

Kriiger,  F.,  61,  73. 

Kulpe,  O.,  5,  51,  55,  66,  76,  81,  97,  99, 
1 14, 140, 143, 151, 171, 186  f.,  189, 193  f., 
207  f.,  21 1,  219, 225, 227, 300,  320, 2,12,  ff., 
336  f.,  368,  372  f.,  375,  378  f.,  382,  395, 
404,  409,  416,  419,  427,  432. 

Kundt,  A.,  315. 

Ladd,  G.  T.,  39,  404,  432. 
Lambert,  J.  H.,  15. 
Lange,  C,  150. 
Lange,  L.,  213  f.,  225. 
Lange,  N.,  195,  197  ff.,  2CX). 
Langendorff,  O.,  177  f.,  180,  183,  185,432. 
Laska,  W.,  324ff.,328. 
Lay,  W.,  387.  393  f.,  401. 
Le  Conte,  J.,  252,  259,  261,  268,  273,  294. 
Lebmann,  A.,  36,  151,  166,  1 71,  185,  195, 
197  ff.,  200,  418,  432. 


Index  of  Names 


443 


Ixabft,  J.  H^  J90. 
Lcwv.  \V^  375. 
I.inn.cuft,  IJ9. 

Lipjn,  Th..  J9, 1 87  f^  ao8, 3J0>  jaa,  3j6  «^ 

375.  385. 432. 
I  j»iing,  J.  B^  23a,  243,  Ml' 
IakWc,  J..81. 
Luch,  J..  311. 
Loewenton.  EL,  376. 
Lomliard.  W.  P.,  183  C 
Ia>Uc,  R.  H^  iSS,  375,  432. 
Ix>iigh,J.  E..  39. 
I  tttfwig,  C^  272. 

:^.:..  L.  So,  143.411,432. 

Maior,  D.  Rn  158. 

Marbe,  K.,  17,  196  ft,  aoa 

Martin,  L.  J.,  xxiv. 

Martiu*.  G^  39,  225,  340, 346. 

Miriius-MaUdorif,  J^  260,  273  f. 

Maston,  V.,  199. 

Matsamoto,  M^  359,  362,  370  fiC 

Maadsley,  H.,  191. 

MaxweU.  J.  Qerk.  id. 

Mayer.  A.  M^  349- 

Mayo,  H.,  263. 

McQurc,  M.  F.,  39. 

Meinong.  A..  333. 

Meisancr,  G..  252 

XIelde,F.,6i. 

Meumann,    E.,   xxiv.,    199,  337  if.,  340, 

346  flL,  351  ff..  354  ff.,  401. 
Meyer,  H.,  31  f.,  262. 
Meyer,  M..  73,  329  f.,  333,  336,  378  f. 
Moore,  A.  W..  225. 
MoaM>.  A..  170  f..  182,  184  f..  432. 
M&Ucr.  G.  E^  xwT.,  5,  143,  187,  207,  222, 

402,420. 
Mailer.  R.  F.,  201,  203  f.,  411. 
MuUer-Lycr,  F.  C,  322  flf..  325,  328. 
Mttittterberg,  H.,  xxxv.,  150.  162, 192. 195, 

198  f.,  aoo.  211,  260,  263.  309,  357»4<»» 

402,  411,  415  ^  4«9  f .  427.  432. 
MttSKhenbroek,  P.  ran,  16. 

NageU  W.  A.,  ijo.  133.  >35  f-  "38  i- 
Newton,  L.  16.  49. 
Nicbok,  H..  381. 

Obersteiner.  H.,  227. 
Oehrwall,  H.,  too.  104. 


Offner,  M.,  417. 
(>ppel.J..3i5. 
Orschansky,  S.,  214. 

Pace,  E.  Am  I95>  198  f.,  200. 

Panum.  P.  L.,  284. 

Parriih.  C,  S..  374.  383. 

Patrick.  G.  T.  W.,  lit. 

Paulhan,  F..  391,  417. 

Pflaum,  C.  D.,  207. 

Pierce,  A.  H.,  207,  346. 

PilUbur)-.  W.  B.,  44,  183,  302,  349,  374  U 

385.411  f. 
Pilzeckcr,  A.,  187,   191,  JOG,  207  f.,  211, 

222,  225,  420. 
PUtcau.  J.,  16,  49. 
Pretori,  H..  36. 
Preyer,  W.,  73,  357. 
Purkinje,  J.,  48,  234,  369. 

Rayleigh,  68,  369. 

Ribot,  Th.,  187.  387,  393.  430,  432. 

Richet,  C.  143. 

Rivers,  W.  H.  R..  386. 

Robertson,  G.  C,  356,  404. 

Rood,  O.  N..  38. 

Ruete,  C.  G.  T.,  259,  262  flL,  267,  269, 

272  f.,  294,  296. 
Rutherford,  W.,  422. 

Sachs,  M.,  36. 

Sanford,  E.  C,  xxriv.  f.,  5, 7, 30, 37, 40, 45  f., 

48,  5».  57.  61,  64,  73,  75,  80,  97,  143. 

203,  207,  212  f.,  223,  234  f.,  237,  239  f.. 

242,  246, 250  ff.,  255,  260,  265,  267,  274, 

284.  287,  292,  294,  296,  300,  320,  337, 

349  f..  362.  369  f..  375.  378,  382,  4i7» 

430.  433- 
Sanson.  L.  J.,  235  f. 
Schaefer,  K.  L.,  370. 
Scheiner.  C,  237.  427. 
Schmidt.  H..  III. 
Schroder,  H.,  312. 
Schttlze.  R.,  332. 

Schnnuinn,  F.,  143,  339,  346,  402,  420. 
Scini,  D.  R.,  37. 
Scripture,  E.  W..  xxxiv.,  28.  44.  94»  404» 

412,  4i5f-4»9»433- 
Secor.  W.  B.,  394. 
Sharp.  S.  E.,  399,  402. 
Shaw,  W.  J.,  225. 


Index  of  Names 


Smith,  M.  K.,  338,  340,  353  ff.,  356. 

Smith,  W.  G.,  417. 

Soramer,  R.,  162. 

Spencer,  H.,  404. 

Starbuck,  E.  D.,  390. 

Stern,  L.  W.,  xxvii.,  214,  216,  225,  387, 
391,401  f.,  411,417,433. 

Sternberg,  W.,  105. 

Stetson,  R.  H.,  391,  393. 

Stevens,  W.  LeC,  267,  269. 

Stout,  G.  F.,  5,  51,  82,  188  f.,  228,  433. 

Stratton,  G.  M.,  297. 

Strieker,  S.,  391,  394. 

Stumpf,  C,  51,  54  f.,  56  ff.,  64, 66, 73,  75  f., 
80, 187, 191  f.,  194,  208, 219, 229,  231  f., 
329  f.,  332  ff.,  335  ff,  346,  353,  355,  362, 

375.  391,  394.  419.  433. 
Sully,  J.,  404,  427,  433. 
Suter,  W.  N.,  239,  241,  294. 

Taine,  H.,  387. 

Talbot,  E.  B.,  392. 

Tallman,  R.  W.,  in. 

Tawney,  G.  A.,  191,  375  ff:,  380  ff. 

Tetens,  J.  N.,  188. 

Thiery,  A.,  321  ff.,  324. 

Thompson,  H.  B.,  185. 

Thompson,  S.  P.,  148,  370. 

Toulouse,  E.,  399. 

Trautscholdt,  M.,  415. 

Treitel,  T.,  39. 

Tschermak,  A.,  16,  39, 

Tschisch,  W.  von,  206. 

Tuke,  D.  Hack,  191. 

Tyndall,  J.,  61. 

Uhl,  L.  L.,  187. 
Uhthoff,  W.,  39. 
Urbantschitsch,  V.,  194,  199  f.,  370. 

Valentin,  G.,  136  f. 
Vaschide,  N.,  170  C 


Vintschgau,  M.  von,  99,  in,  114,  433. 
Voeste,  H.,  39. 

Volkmann,  A.  W.,  200,  234,  252. 
Volkmann  von  Volkmar,  W.,  55,  187. 

Wagner,  R.,  411. 

Wahle^R.,  417. 

Waller,  A.  D.,  144,  148,  233,  239,  242, 

252. 
Ward,;..  157,  375,433. 
Washburn,  M.  P.,  48,  382,  400. 
Weber,  E.,  369  f. 
Weber,  E.  H.,  82,  143,  374  f.,  382,  425, 

433. 
Wheatstone,  €.,  260,  263,  265,  267  f.,  270, 

273  f.,  276,  278  f.,  289,  293  ff.,  296  ff., 

300,  302  f. 
Wirth,  W.,  39. 
Witasek,  S.,  xxxiii.,  xxxv.,  292,  333,  369, 

39 1 »  432. 

Wolff,  C.,  188. 

Wood,  R.  W.,  299. 

Wundt,  W.  M.,  xxii.,  xxvi.,  5,  10  ft.,  26, 30, 
36  ff.,  49  f.,  51,  82,  99,  III,  114,  143, 
150,  185,  187  f.,  197  ff.,  200  f.,  203  ff., 
206,  211,  213,  219,  222,  224  ff.,  230  f., 
233  f.,  242  ff.,  247,  249,  251  f.,  254, 
256  f.,  260,  262,  271,  273  f.,  277,  279  f., 
284  ff.,  291,  293  f.,  304,  309  f.,  314, 
316  ff,  319  ff,  324  ff.,  327  f.,  332,  338, 
353.  355  f-.  357.  375. 378.  385, 393,  402, 
404,  416  ff.,  419,  424,  430,  433. 

Zeitler,  J.,  201,  203  f.,  412. 

Zeynek,  R.  von,  105. 

Ziehen,  Th.,  150,  415,  433. 

Zindler,  K.,  5. 

Zollner,  F.,  200. 

Zwaardemaker,   H.,   112,   114  f.,   118  ff., 

128  f.,  130  f.,  133,  134  ff.,  138  f.,  I42» 

433- 


INDEX   OF  SUBJECTS 


Abcmtioa,   cbroaMtk»   1391    ipheriad, 

340. 

Accentuation,  tubjecthre,  3J9  fL,  346, 35 1 ; 
analogies  to,  346;  and  intensification, 
346;  IB  the  Uctual  sphere,  354. 

artiiictal   paraljiit    of 
oi;  199;  mechittinDoi;  234  01; 
unpenectKMW  olf  341  • 

Action,  paycbology  o(,  313,  319,  336; 
qnwtioM  on,  434, 436  «:,  439. 

AclHritj,  mental,  meanings  of,  187  f. 

Adaiiladon,  Tisoal,  local,  8,  37  ff^  40  (L; 
geBenl,38;  references  on,  39;  ofcaU- 
neons  sensation,  81;  of  smell,  129; 
▼isnal,  importance  of,  in  tachistoscopic 
work,3Q4C 

Additional  exercises,  experiments  and 
qnestions,  on  colour  mixing,  16;  the 
blind  spot,  37  C;  the  macula  lutea,  30; 
negattre  after-images,  43  f. ;  binocular 
after-images,  50;  beats,  61;  pitch-dif- 
ference in  Imiaaral  hearing,  65  f.;  the 
ear  as  resonator,  66  ;  besting  of  differ- 
eace-tones,  72;  mechanical  stimulation 
of  temperature  spots,  85;  their  anal- 
gesia, 85;  their  inadequate  thermal 
■timalation,  85  f.;  the  perception  of 
heat,  90  f.;  Goldscheider't  secondary 
97;  electrical  stimulation  of 
and  pain  spots,  97  f.;  Kiesow's 
dieek  area,  98;  mechanical 
and  dectrical  stimulation  of  fungiform 
papiike,  103;  taste  reactions  of  filiform 
and  circumTallate  papillae,  103;  elimi- 
nation of  single  taste  qualities,  103  f.; 
neotralisation  of  tastes,  no;  sjmthesis 
of  mixed  taites,  1 10  f. ;  Pick's  inspira- 
tkm  experiment,  118;  serial  method 
(•flection),  155  fL;  muscular  strength 
(band  dynamometer),  167  fil ;  the  ergo- 
gacfk,  171;  the  S|^ygmograph,  184: 
the  pneamograph,  184;  Tariations  of 
the  reaction  experiment,  324  ft,  417; 
▼isnal  space  perception  (preliminaries), 


354  f.;  Wundt's  mirror  experiment, 
385  f.;  Hering's  binocular  colour 
mixer,  391;  the  MUIler-Lyer  illusion, 
331  ff.;  illusions  of  rhythmisation,  351  f.; 
variation  of  receiving  apparatus  in  work 
on  sound  localisation,  369;  of  character 
of  stimulus,  369;  intracranial  localisa- 
tion, 369  f. ;  effect  of  fatigue  and  atten- 
tion, 370;  k>calisation  with  two  sound 
stimuli,  370  f.;  variations  of  Weber's 
second  method  of  skin  localisation,  374; 
paradoxical  localisation,  381 ;  localisa- 
tion pattern,  381  f.;  clasped  hand  ex- 
periment, 386;  Henri's  mirror  experi- 
ment, 386;  determination  of  types  of 
idea,  394  ff.;  experiments  on  auditory 
association,  410 ;  on  visual-auditoiy 
association,  410;  attributes  of  the  visual 
colligation,  420;  further  experiments 
on  association,  420. 
Adhesion,  error  of,  in  smell  work,  119, 

"32.  135- 

Adjustment  of  writing-lever  to  kymo- 
graphic  surface,  180. 

/Esthesiometer,  Griesbach's,  383. 

Affective  psychology,  reasons  for  back- 
wardness of,  149  f.;  methods  of,  149, 
151,  154,  158,  162,  167,  171 ;  questions 
on,  422  f.,  425  ff.,  428. 

Affective  qualities,  theories  of,  150;  refer- 
ences on,  150  f.;  indicated  by  invol- 
untary arm  movement,  158  ff.;  by 
muscular  strength,  162  ff.,  167  ff.;  by 
bodily  volume,  171  ff.;  in  the  rhythm 
consciousness,  354. 

After-images,  visual,  31,  33,  37  ff.;  theo- 
ries of  negative,  37 ;  references  on,  38 ; 
duration  of,  40  f. ;  objective  match  for, 
41;  contrast  in,  42  f.;  periodicity  of,  43 ; 
results  of  experiments  on,  40  ff.,  45; 
observation  of,  with  persistence  of 
stimulus,  45;  change  in  apparent  mag- 
nitude of,  with  distance  of  reacting  sur- 
Cftce,  45 ;  movement  of,  with  movement 


445 


446 


Index  of  Subjects 


of  the  eye,  46;  positive,  46;  positive 
and  complementary,  47  f.;  flight  of 
colours  in,  48  f. ;  theory  of  flight  of 
colours,  49;  binocular,  49  f.;  instru- 
ments, 50;  and  binocular  colour  mix- 
ture, 289;  of  pressure,  373,  425. 

Analysis  and  genesis,  spheres  of,  in  the 
psychology  of  perception,  228  f.,  231  f., 
424. 

Analysis  of  clangs,  factors  in,  336  f. 

Angles,  overestimation  of  small,  317. 

Answers  to  questions,  on  visual  sensation, 
5  flf.;  on  colour  mixing,  14  ff".;  on  campi- 
metry,  23  ff. ;  on  visual  contrast,  35  f. ; 
on  visual  after-images,  42  f.,  45,  49; 
on  auditory  sensation,  54  f.;  on  beats, 
57  ff.;  on  cutaneous  sensation,  81;  on 
temperature  spots,  84  f.;  on  tempera- 
ture sensitivity,  88  ff. ;  on  pressure  spots, 
92  f.;  on  pain  spots,  95;  on  taste  sen- 
sitivity, loi  ff.;  on  the  taste  qualities, 
105  f.;  on  taste  contrasts,  107  ff.;  on 
the  field  of  smell,  1 1 7  f. ;  on  smell  ex- 
haustion, 128  ff.;  on  smell  compensa- 
tions, 133  ff.;  on  smell  mixtures,  136  ff.; 
on  smell  contrasts,  141  f.;  on  organic 
sensation,  143;  on  muscular  sensation, 
147  f.;  on  affection  (method  of  impres- 
sion), 152  ff.;  on  involuntary  arm 
movement,  161  f.;  on  dynamometry, 
166;  on  plethysmography,  182  ff.;  on 
attention  in  general,  187  ff.;  on  atten- 
tion as  a  state  of  consciousness,  190  f., 
192  ff.,  195  ff.,  203  ff.,  206  ff.;  on  the 
sense  processes  in  attention,  209  ff. ;  on 
attention  and  affective  process,  21 1 ;  on 
action,  212;  on  the  simple  reaction, 
219,  225  ff.;  on  the  reduced  eye,  233; 
on  the  formation  of  the  retinal  image, 
233  f.;  on  accommodation,  234  ff.;  on 
eye  movements,  242  ff.;  on  retinal  cor- 
respondence, 252  ff.;  on  stereoscopic 
vision,  261  ff.,  268  f.,  291  ff.;  on  pseu- 
doscopic  vision,  295  f.,  299,  302  f.;  on 
optical  illusions,  319  f.;  on  tonal  fusion, 
333  ff.;  on  rhythm,  346  ff.,  351,  352  ff.; 
on  localisation  of  sound,  368  f. ;  on  cu- 
taneous localisation  of  a  single  point, 
373  f.;  on  aesthesiometry,  379  f.;  on 
Aristotle's  experiment  and  variants, 
384  f. ;  on  the  questionary,  387  ff. ;  on 


ideational  type,  393  ff.,  402;  on  associ- 
ation of  ideas,  409  f.,  412  f.,  415  ff. 

Apparatus,  general  remarks  on,  xxxii.; 
for  study  of  visual  sensation,  20,  26, 
28  ff.,  30,  36  f.,  50;  for  auditory  sensa- 
tion, 52,  55,  61,  77.  80;  for  cutaneous 
sensation,  81,  S^  f.,  93  f.,  97  f . ;  for 
gustatory  sensation,  100;  for  olfactory 
sensation,  131  ff.,  142;  for  organic  sen- 
sation, 145;  for  the  study  of  affection, 
159,  161  f.,  167,  170  f. ;  the  kymograph 
and  its  accessories,  172  ff.;  plethysmo- 
graphs,  152  f.;  sphygmograph,  183; 
pneumographs,  184;  tachistoscope,20i; 
for  reaction,  212  f.,  227,  417;  phaco- 
scope,  236;  for  Listing's  law,  245,  248; 
stereoscopes,  261,  264  f.,  268  f.,  271  ff.; 
slides,  274  ff.;  for  perception  of  re- 
flexion, 285;  for  binocular  colour  mix- 
ture, 291;  pseudoscopes,  295,  297  ff.; 
for  study  of  optical  illusions,  309;  for 
tonal  fusion,  330;  time-sense,  338;  for 
rhythm,  338,  349;  sound-cage,  358  f.; 
for  localisation  of  sound  with  two  stim- 
uli, 371 ;  sesthesiometer,  382;  for  study 
of  ideational  types,  396  ff.;  memory, 
405  f. ;   list  of  makers,  434  f. 

Apperceptive  factors  in  pseudoscopic 
vision,    300,  302. 

Aristotle's  experiment,  383  f.,  386. 

Arm-rest,  145. 

Articular  sensation,  143,  425,  428;  and 
Wundt's  theory  of  visual  space  percep- 
tion, 230. 

Assimilative  illusions,  318. 

Association,  principle  of,  illustrated  by 
the  filling  of  the  blind  spot,  29  f.;  by 
temperature  sensitivity,  90;  associative 
processes,  central  and  peripheral,  in  taste 
discriminations,  102;  smell  associations 
of  ordinary  'taste,'  112;  error  of,  in 
affective  work,  151;  the  association  re- 
action, 226,  378;  optical  illusions  of 
association,  318;  the  basis  of  sound 
localisation,  358,  365;  five  meanings  of 
the  phrase  *  association  of  ideas,'  402  f.; 
problem  of,  403;  attitude  of  experi- 
mental psychology  to,  404;  references, 
404;  law  of,  404  f.;  working  definition 
of,  405 ;  apparatus  and  materials,  405  ff. ; 
stimulus  cards,  406  f.;   test  cards,  406; 


IiuUx  of  Subjects 


447 


rtsults  of  oiperimeiit  (CaUdns),  408  C; 
reUtive  effect  of  freqaenqr*  viTidneM, 
recency  and  primacy,  409;  auditory 
and  mixed  (visual^auditory)  ienet,4io; 
indrridaal  differencea,  410  C;  as  deter« 
mined  by  relation  of  impreation  to  pres- 
ent contents  of  coatdoasnessi  41 1; 
tachistoacopic  method,  413;  the  train 
of  ideas,  413  ff.;  specimen  table  of  re- 
sults, 414;  verbal  associations,  415; 
references,  415  f.;  results  of  experi- 
mental work  on  association,  416;  me- 
diate association,  416  f.;  clasiitication 
of  successive,  417;  Wundt's  theory  of 
identical  and  contiguous  connections  of 
418  f.;  association  as  coUiga- 
419;  its  intensity,  419;  its  qual- 
ity, 4X>;  references  to  further  methods 
of  %rork,  420;  questions  on,  4Z4,  426  ff^ 

4*9. 

Astigmatism,  irregular,  340;  r^ular,24of. 

Attention,  problem  of,  186  ff. ;  history  of, 
1S6;  theories  of,  187;  classifications 
of,  187;  asstateofconsciousness,l89ff.; 
cleamesa  of  contents  attended  to,  189  ff. ; 
'bringing  out'  of  sensations  by,  191; 
intensification  by,  191  l.\  increase  of 
duration  by,  192  f.;  reproductory  value 
of,  192  f.;  inertia  of,  194,  206;  fluctu- 
ationof,  194  fL ;  duration  of,  195,  198  f. ; 
errors  in  determination  of  duration, 
196  f. ;  programme  of  work  on  fluctu- 
ation, 197  ff.;  references  on,  200;  seat 
of  fluctuations,  200;  range  of,  200  ff., 
203;  roving  of,  203  fL;  rise  of  sensa- 
tion in  state  of,  205  f.;  the  complica- 
tion expenroent,  206  f.;  determinants 
of  passive,  207  f.;  sense-processes  in, 
209  ff.;  motor  aspect  of,  211 ;  measure- 
ment of  degree  of,  21 1 ;  relation  of,  to 
affective  process,  references  on,  211 ; 
signal  for,  omitted  in  certain  reaction 
experiments,  224;  and  retinal  rivalry, 
191,  284;  and  localisation  of  sound, 
370;  in  tactual  discrimination,  379;  and 
association,  409;  questions  on,  422, 
425,  427*  4*9- 

Attentive  consciousness,  analysis  of^  166  f., 
209  f. 

Aubert's  diaphragm,  44. 

Auditory  sensation,  difltmltics  of  investi- 


gationof,5i  f.;  references  on,  51;  tOM 
and  noise,  53:  pitch  of  noise,  53;  ter- 
minology of,  54;  likeness  of  octave  and 
fundamental,  55;  diagram  of,  55;  the- 
^Pl  o^  55 ;  pilch  of  a  beating  complex, 
57  ff. :  pitch-difference  of  ears,  successive 
method,  61  ff.;  simultaneous  method, 
6$  f.;  ear  as  resonator,  66;  combina- 
tion-tones, 66  ff^;  clang-tint,  73  ff.; 
overtones,  75  ff.;  methods  of  observing 
partials,  76  ff.;  questions  on,  421  fi^ 
425. 

Auditory  stimuli,  useful  in  affective  work, 
171  f. 

Automatograph,  159,  i6x 

Beats, experiment  on,  55  ff.;  counting  of, 
56;  pitch  of  beating  complex,  57  ff.; 
double  pitch-pipe  for  demonstration  of, 
61 ;  of  difference-tones,  72;  method  of, 
for  observation  of  partials,  79;  can  be 
changed  in  idea,  336. 

Bitter,  of  distilled  water,  108. 

Black,  a  sense  quality,  291. 

Blind  spot,  place  of,  18,  21 ;  mapping  of, 
27;  filling  out  of,  28;  figures  of,  28; 
spatial  value  of,  29;  theory  of  filling, 
30;  references  on,  30;  and  binocular 
after-images,  50. 

Blix'  temperature  point,  84. 

Books,  the  best  fifty  for  work  with  this 
Course,  431  ff. 

Breathing  spots,  method  of  mapping, 
114  f. ;  cuts  of,  115  fil;  and  field  of 
smell,  117. 

Brushes  for  stimulation  of  fungiform  pa- 
pillae, 100. 

Campimeter,  dimensions  of  Hering's,  23; 
advantages  of  this  form,  24. 

Campimetry,  17;  results  of  experiments, 
19,  20,  22;  extent  and  stability  of  reti- 
nal zones,  23  f. ;  references  on,  26. 

Catalogues,  collection  of,  434. 

Chronoscope,  Sanford's  vernier,  212  f., 
417. 

Clang-tint,  strict  sense  of  term',  73;  sec- 
ondary criteria  of  clang,  73  f.;  illustra- 
tion of,  76;  influence  of,  upon  degree 
of  fusion,  336. 

Oeanliness,  in  taste  work,  99  f. 


448 


Index  of  Subjects 


Cold  sensation,  von  Frey's  paradoxical, 
86,  430. 

Cold  spots,  map  of,  96;  set  Temperature 
spots. 

Colligation,  opposed  to  fusion  as  mode  of 
conscious  connection,  130,  419  f. 

Colour  blindness,  6  f.,  26;  Hering's  ap- 
paratus fur  testing,  7. 

Colour  equations,  method  of  making,  32. 

Colour  mixer,  Marbe's,  17. 

Colour  mixture,  9;  results,  first  law,  10; 
second  law,  1 1 ;  third  law,  1 1 ;  mixture 
of  three  or  more  colours,  12;  matching 
of  unsaturated  colours,  13;  contrast  in, 
14;  methods  of,  14  f.,  16;  with  pig- 
ments, 16;  references  on,  16  f.;  binoc- 
ular, 289  ff.;  Hering's  apparatus  for, 
291. 

Colour  pyramid,  5  f. 

Coloured  papers,  error  of  experiments  with, 
9;  characteristics  of  good,  14;  used  in 
experiments  on  aflFection  by  the  method 
of  paired  comparisons,  151  ff.;  by  the 
serial  method,  I54ff. ;  emotive  value  of, 

153  f. 

Coloured  shadows,  36. 

Combination-tones,  experiment  on,  66; 
diagrams,  67,  69,  71;  practice  in  hear- 
ing of,  68. 

Compensation  of  smell  qualities,  131  ff.; 
tested  by  olfactometric  method,  131  ff.; 
various  views  of,  133;  numerical  results, 
134;  in  everyday  life,  131,  135;  system- 
atic importance  of,  136;   and  mixture, 

137- 

Complication  apparatus,  206  f. 

Confluence,  principle  of,  in  optical  illu- 
sions, 323  f. 

Connection,  modes  of  conscious,  91,  130, 
419  f.;  the  tracing  of,  part  of  the  prob- 
lem of  perception,  228  f. 

Consciousness,  nature  of  the  experimental, 
4;  in  affective  work,  151  f.,  156,  166, 
171,  181 ;  the  attentive,  166  f.,  209  f.; 
grades  or  degrees  of,  187,  194;  connec- 
•  tion  with  contents  of,  as  determinant  of 
attention  and  association,  207  f.,  41 1; 
the  rhythmical  and  its  opposite,  342, 
344,  352  ff.;  the  associative,  416,  419  f.; 
questions  on, 422  f.,428f.;  see  Ideational 
types.  State  of  consciousness,  Types. 


Contours,  influence  of,  on  attention,  208; 
prevalence  of,  283,  291 ;  rivalry  of,  283  f., 
290;  and  binocular  colour  mixture,.  289. 

Contrast,  visual,  30;  Meyer's  experiment, 
31  ;  results  of  experiments  on,  32,  33, 
34»  35;  instantaneousness  of,  35;  with 
coloured  shadows,  36;  references  on, 
36;  ihctruments  for  demonstrating,  36  f.; 
in  the  after-image,  42  f.;  of  tastes, 
simultaneous  method,  106  ff.;  instances 
of,  107;  error  of  expectation  in  work  on, 
107;  laws  of,  109;  successive  method, 
109  f.;  of  smells,  139;  simultaneous 
method,  141;  successive  method,  142; 
visual,  and  attention,  208;  and  binocular 
colour  mixture,  289,  291;  illusions  of, 
318;   of  movement,  326. 

Corresponding  points,  252. 

Course,  conduct  of  the  present,  xxi.,  xxix., 
xxxi.,  xxxii.,  xxxiii.,  18;  choice  of  experi- 
ments for,  XXXV. 

Courses,  published,  in  experimental  psy- 
chology, xxxiii. 

Cutaneous  sensation,  81  f.;  organs  of,  81 ; 
adaptation  of,  81;  references  on,  82; 
temperature,  82  ff.,  87  f.,  96;  pressure, 
92  ff.,  96;  pain,  94  ff.;  Goldscheider's 
secondary  pressure  (pain),  97;  electrical 
stimulation  of  pressure  and  pain  spots, 
97  f.;  Kiesow's  painless  cheek-area,  98; 
questions  on,  422  f.,  425,  428. 

Cyclorama,  illusions  of,  293. 

Defects  of  optical  systems,  239  ff. 
Difference,    sensations    of,    non-existent, 

378. 

Difference-tones,  67  ff.,  72;  beating  of, 
72;   intensified  by  attention,  192. 

Diffusion,  error  of,  in  taste  work,  105;  in 
smell  work,  118,  1 20,  1 68. 

Direction  of  sound,  judgment  of,  358;  ex- 
periments on,  360  ff.;  of  tactual  impres- 
sions, with  changed  position  of  parts, 
380  f. 

Dispcision  images,  in  optical  illusions,  325. 

Distance,  secondary  criteria  of,  293  f.;  of 
sound,  judgments  of,  358;  experiments 
on,  371  f.;  of  tactual  impressions,  with 
changed  position  of  parts,  383. 

Distraction  of  attention,  overcome  by  prac- 
tice, 227;   method  of,  400. 


Indicx  of  Subjects 


449 


I  <..  ...^.  ^^  ....  .^w.  xgnifkftiicc  i'.. 
.V;i  f. 

lent,  aj;  «.,  254. 

l»uiaii  u  1  >^.i>av.  •It*,  how  aflcctcil  by 
ancntii>n.  193  f.;  c<)aivalcnt  of  intensity 
^T  :ntc-r\AU  in  the  rhythmical  coniciou*- 
:  ,^s.   ;;S,  351 ;  rariation  of,  35a 

I»\n.\m!:.cier,  finger,  163;  hand,  167. 

Lar,  the  .nfcnc!.  ;6,  62;  as  resonator, 
66;  s.Hj.;  !  .;  ;.  t  .  \  (  6, 192;  direct  analy- 
sis hy  the.  -  , .        i^ging  of,  364. 

Ears,  pitch->: -t  of  the,  61;  average 

diflRerencc  t>ct\vccn,  62  f.;  pitch  differ- 
ence in  binaural  hearing,  65. 

Ellis*  doable  pitch-pipe,  for  beats,  6i. 

Ellb*  harroonical,  52,  80. 

Emotion,  and  the  systematic  position  of  the 
rhythm  consciousness,  352  ff.;  emotions 
i>f  rhMhm,354;  questions  on, 424^^,428. 

Kmutivc  value  of  colonrs,  153  f. 

Entopiic  phenomena,  241  f.;  question  on, 
427. 

Equation,  personal,  213. 

Ergograph,  170  f. 

Frr  r.  nv.in,  ;'.!;  error  methods,  379. 

Kt:.t.  r  spray. n;^,  I45. 

KxAuiination  questions,  on  visual  sensa- 
t^n,  421  fT.,  424  f.,  427;  on  auditory 
sensation,  421  ff.,  425;  on  cutaneous 
sensation,  422  f^  425, 428;  on  olfactory 
sensation,  423,  427;  on  gustatory  sen- 
sati  jn,  427 ;  on  organic  sensation,  422  ff ., 
42$,  427  f.,  on  affection,  422  f.,  425  ff!., 
428:  on  attention,  422,  425,  427;  on 
action,  424,  426  ffl,  429;  on  visual  per- 
ception, 423  f.,  426  f.;  on  auditory 
perception,  423,  425,  427;  on  tactual 
perception,  422  ff.,  425,  428;  on  as- 
sociation. 424,  426  ff.,  429;  general, 
422  ff.,  425  ff.,  428. 

Kxhaustion,  method  of,  in  smell  work, 
1190.;  time  results,  121 ;  and  recupera- 
tion, time  results,  1 24 ;  determination  of 
qualities  by,  125  ff.;  problem  of,  in  sen- 
sation, 1 28  f. 

Hjcpectation,  error  of,  in  taste  work,  105, 
107;  to  l>e  sturlied  by  the  reaction 
methoil,  226;  in  touch  work,  376,  379; 
in  work  on  association  of  ideas,  409. 

2G 


i  ^,  viicnce,  appeal  to,  254. 

Experiment,  the  synthetic,  xxii.,   110  f., 

258. 
Eye,  listing's  reduced,  232  f. 
Eye  and  ear  obsenrationa,  in  astronomy, 

306. 
Eye  movements,  laws  of,  242  ff.;  in  space 

|)erception,  255  ff.;  in  the  Mttller-l.yer 

illusion,  324;  rhythm  based  on,  355. 

Faculty  psychology,  187  f.,  254. 

Fall-chronometer,  Wundt's,  aoi ;  Cattell's, 
201. 

Fatigue,  error  of,  in  campimetry,  18,  24; 
in  work  on  cutaneous  sensation,  82, 
96;  on  gustatory  sensation,  100,  105; 
on  olfactory  sensation,  116,  118,  129; 
in  affiective  work,  168:  to  be  studied 
by  the  reaction  method,  226;  in  sound 
localisation,  370;  in  tactual  discrimina- 
tion, 379. 

Fixation,  lines  of,  in  optical  illusions,  314. 

Flight  of  colours  in  the  visual  after-image, 
48  f. 

Flute,  range  of,  73,  74. 

Frequency,  curve  of,  217;  illusion  of,  with 
metronome  beats,  35 1  f. ;  as  condition  of 
association,  409. 
I  Fusion,  instances  of,  91,  129;  andcoUiga- 
i      tion,  1 29  f.,  402. 

i  Fusion,  tonal,  application  of  reaction 
method  to,  226;  Stumpf's  theory  of, 
231  f.;  definilion  of,  329  f.;  procedure 
with  unmusical  and  musical  observers, 
330  ff.;  sourcesof  error,  331  f.;  scale  of 
fusion  degrees,  for  unmusical  observers, 
332;  references  on,  333;  fusion  steps, 
334  •  general  law  of  fusion,  334;  fusion 
and  intensity  of  components,  334;  de- 
grees of,  within  and  beyond  the  octave, 
335;  influence  of  clang-tint  on,  336; 
unchangeable  in  idea,  336;  pitch  of, 
337.    . 

General  terms,  Kfilpe's  law  of  reproduc- 
tion of,  378  f.,  409. 

Genetic  theory,  place  of,  in  psychology  of 
perception,  208,  229,  231  f.,  424. 

Gradation  methods,  379. 

Gtistatory  sensation,  Kiesow's  scheme  of 
relationships  in,  99;  references  on,  99; 


450 


Index  of  Subjects 


distribution  of,  over  the  tongue,  99  f!.; 
number  of  taste  qualities,  105  f. ;  taste 
contrasts,  106  ff.;  question  on,  427. 

Habituation,  error  of,  in  taste  work,  105; 

to  be  studied  by  the  reaction  method, 

226;  in  touch  work,  379. 
Halo  of  after-image,  40,  41. 
Haploscope,  Hering's,  265,  270. 
Heat,  perception  of,  86,  90,  430;  mode 

of  arousal  of,  91 ;  references  on,  91. 
Hering's  window,  36. 

Idea,  two  meanings  of,  404,  419. 

Ideational  types,  discovery  of,  387 ;  visual, 
auditory  and  tactual  (motor),  391 ; 
references,  391 ;  Gallon's  table  of  men- 
tal imagery,  392;  relative  frequency  of, 
393;  experimental  methods  for  deter- 
mining, 393  fT. ;  questions  on,  423,  428; 
see  Type. 

Impression,  method  of,  for  study  of  affec- 
tion, 151,  154. 

Impulse,  as  typical  motive,  212,  424;  in 
the  simple  reaction,  219,  226. 

India  rubber,  as  typical  smell  stimulus, 
132  f. 

Indirect  vision,  1 7  fF. ;  in  optical  illusions, 
322. 

Individual  psychology,  398,  410  f. 

Induction  coil,  use  of,  98,  144,  371  f.; 
theory  of,  148;  Preyer's  double,  371. 

Inertia  of  attention,  194,  206. 

Instinctive  stimuli,  James',  208. 

Instructor,  preparation  of,  in  introspec- 
tion, xxii.;  in  physics,  xxv. ;  in  mathe- 
matics, XXV. ;  in  physiology,  xxv.  f. 

Instrument  makers,  434  f. 

Intellectual  temperaments,  Miinsterberg's 
three,  417. 

Intensity,  characteristic  of  clangs  of  cer- 
tain instruments,  73;  variation  of, 
characteristic,  74;  judgments  of,  and 
the  intensifying  power  of  attention, 
192;  as  determinant  of  attention, 
207  f.;  reactions  to,  224  f.,  226;  of 
components  of  tonal  fusion  (relative 
and  absolute),  334;  in  sul)jective 
rhythmisation,  346  f.;  in  rhythm,  as 
equivalent  of  duration  or  interval,  348, 
351 ;  illusions  of,  with  metronome  beats, 


351  f.;  of  pressure,  subjective  and  oh 
jective,  382;  of  association,  419. 
Interval,  in  subjective  rhythmisation,  340, 
342,  347;  variation  of,  equivalent  to 
change  of  intensity  or  duration,  348, 
351 ;  illusion  of,  with  metronome  beats, 

352. 

Introspection,  the  learning  of,  xxi.;  the 
teaching  of,  xxii.;  concrete  and  pictur- 
esque wording  of,  xxxi. ;  of  fluctuation  of 
attention,  199  f.;  of  roving  of  attention, 
203  ff. ;  hindered  by  the  quantitative 
method  in  work  upon  localisation, 
358;  danger  of  underestimating  its 
difficulty,  389  f. 

Involuntary  movement,  as  index  of  affec- 
tion, 158(1.;  records  of,  160;  apparatus 
for,  159,  161  f.;  biological  explanation 
of,  161  f.;  references  on,  162. 

Jacquet  chronometer,  178. 

Kiesow's  painless  cheek-area,  98. 

Kinaesthetic  sensations,  144,  148. 

Kinesimeter,  93,  145. 

Kymograph,  and  its  accessories,  172;  the 
drum,  172  f.;  paper  for,  173;  smoking 
stand  and  lamp,  173  f.;  stand  for 
spare  drum,  174;  removal  of  smoked 
paper  from  drum,  175;  varnishing  and 
marking,  175  f.;  care  of  record,  176; 
tambour  and  writing-lever,  176  f.;  rub- 
ber tubing  and  its  care,  177  f,;  air- 
cock,  178;  time-marker,  178  f.;  stand- 
ards, 179;  adjustment  of  apparatus  for 
an  experiment,  179  f. 

laboratory  work,  how  to  fail  in,  xxx.  f. 
Letter  squares,  method  of,  396  ff.,  399  f. 
Letters  and  numerals,  gummed,  406. 
Light  induction,  simultaneous,  8. 
Likeness,  psychological,  meanings  of,  54  f. ; 

references  on,  55;   question  on,  428. 
Limen,  stimulus,  140. 
Listing's  law,  242  ff.,  247;   corollaries  to, 

250;   significance  of,  251  f. 
Local  sign,  tactual,  373,  384;  references 

on,  375;   questions  on,  423,  425. 
Localisation,    mechanism   of  visual,    25; 

monocular,  292. 
Localisation  of  a  single  point  upon  the 


Indix  of  Sulijects 


451 


■^u>t  373  ff-;  Weber*t  second  method 
•nd  ila  inrants*  374  f.;  refereacct  on, 
375;    diicrtadaation    of    two    points, 

375  AT. ;  rcsttlts  from  Weber^  lint  method, 

376  r.:  intrcxpecUfe  ttagct  in  an  m- 
cewUng  •eries,  377;  mmom  for  choice 
of  nMthod.  3(8o:  the  pavwioxkal  local- 
i»^  ; '  I ;  the  localintion 
r^  icci,  382;  Aria- 
toik'scx^KruncnUj^jf.;  diacrimination, 
diatancc  and  directioo,  with  changed 
poaitkm  of  parts,  383  ft;  factors  deter- 
minnif  localisation,  384;  Tariants  of 
experiment  with  changed  position  of 
parts,  J85  f. ;  references,  386. 

Localisation  of  sound,  problem  of,  356  ff. ; 
three  possibilities  of  aolation,  357  f.; 
homogeneous  and  heterogeneous  crite- 
ria, 357  f. ;  mediate,  not  direct,  358, 365 ; 
rdative  Talue  of  methods  of  locslising, 
359;  mean  error  and  mean  rariation 
of  cage  settings,  361 ;  introspective 
results,36i,363, 365, 366fll;  individual 
diflcrences,  362  ff . ;  depends  on  relative 
intensity  of  stimulus  in  the  two  ears,364, 
369;  combined  qualitative  and  quantita- 
tive procedure,  366;  variation  of  the  re- 
cehriag  apparatus,  369;  ofthe  nature  of 
sHf  hw,  369;  intracranial,  369  f. ;  as  af- 
fected by  fatigue  and  attention,  370;  with 
two  stimuli,  370  f.;   references,  372. 

Ladwig-Baltxar  kymograph,  173. 

Lostre,  283,  284  f!.,  290;  Wnndt's  mirror 
experiment,  285  f.;  explanation  of, 
386  f.;  favourable  conditions  for,  287  f. 


lotea,  determination  of,  30;  effect 
of  yellow  colouring  on  colour  vision,  30. 

Maicy  tambour,  with  attachments,  177. 

Mathematics,  xxv.,  18. 

Mean  variation,  217. 

Mediate  association,  416  f. 

MeoBory  after-images,  fluctuation  of,  199. 

Memory  apparatus,  Jastrow's,  405  f. 

Memory  images,  flnctnation  of,  199. 

Memory  typea,  387  «.;  visual,  auditory 
and  tactual  (motor),  391  f. ;  refer- 
ences, 391;  practice  of  partial  memo- 
ries, 392  f;  relative  frequency  of,  393; 
qnestions  on,  423,  428. 

Mental  imagery.  Gallon's  table  of,  392. 


Method,  in  psychological  iMtraction,  i; 
of  stepa,  in  campfaneCvy,  18  f.;  of  varia- 
tion, in  colour  equations,  33  ;  of  com- 
paring tone  and  noise.  53  ;  of  exhaus- 
tion, in  smell  work,  119  fl. ;  olfactomet- 
ric,  119,  131  ff. ;  of  just  noticeable 
stimuli,  140,  142  ;  of  paired  compari- 
sons, 151  ff. ;  serial,  in  sffcctive  u 
154  ff. ;  for  registering  truly  the  1' 
ations  of  sttention,  198;  of  in: 
suggestion,  344  ;  of  sound  locaIi»a; 
359 ;  of  error  and  of  gradation,  y,^)  ; 
KSthesiometric,  variation  of,  380  ;  WDni 
method  (Kraepelin  and  Secor)  for  de- 
termination of  ideational  type,  394  f. ; 
qaestionary,  395  f. ;  method  of  letter 
squares (Binet),  396  ff.;  (Cohn), 399  f. ; 
of  distraction  (Washburn),  400;  of 
style  (Fraser),  401  ;  miscellaneous 
(Binet,  Stern),  401 ;  questions  on, 
422  ff.,  425  ff.,  428. 

Metronome,  use  of,  in  work  on  attention, 
205  f. ;  in  work  on  rhythm,  338  f.,  347  ; 
illusions  of  rate,  interval  and  intensity 
of  beats,  351  f. 

Mirror  experiment,  Wundt's,  285  f.;  Hen- 
ri's, 386. 

Mirror  images,  perception  of,  285  ff.;  why 
not  converted,  302  f. 

Mixed  scents,  with  varying  exhaustion 
times  of  components,  122  f . ;  psycho- 
logical analogues  of,  1 29  f. ;  references 
on,  130  f. ;  Zwaardemaker's  indcfmable, 
and  their  explanation,  135;  mixture 
and  rivalry,  136  ff. ;  stable  and  instable, 
137  f. ;  of  more  than  two  components, 

136,  139- 

Mood,  influence  of,  on  affective  work, 
154,  166,  169,  181. 

Moon,  faces  in  the,  190. 

Movement  contrast,  Heymans',  326. 

Movement  of  stimulus,  as  determinant  of 
attention,  208  f. 

Movement  sensstions,  mislesding  term, 
378. 

MOller-Lyer's  figure,  309,  313;  theory  of 
attraction  of  regard  (Delbceuf ),  321 ; 
of  pseudoacopic  angle  (BrenUno),  321 ; 
of  indirect  vision  (Auerbach),  322  ;  of 
mean  distance  (Brunot),  323;  of  con- 
fluence  (MOller-Lyer),   323;    of  per- 


452 


Indix  of  Subjects 


spective  (Thi6ry),324;  of  eye-movement 
(Wundt),  324 ;  of  dispersion  images 
(Einthoven),  325;  of  junction  of  dis- 
continuity (Liska),  325  ;  of  movement 
contrast  (Hcymans),  326;  mechanical- 
aesthetic  (Lipp8),326;  of  relativity  (Jas- 
trow).  327. 

Muscular  sensation,  quality  of,  143  ff., 
147 ;  use  and  abuse  of  term,  144 ; 
Goldscheider's  description  of,  146; 
analysable  from  the  fatigue  complex, 
147 ;  references  on,  144,  148 ;  ques- 
tions on,  425,  427. 

Muscular  strength,  as  index  of  affection, 
162  ff.,  167  ff.;  records,  164  f.,  169; 
instruments,  163,  167,  170;  references, 
171. 

Noise,  relation  of,  to  tone,  52;  pitch  of, 
53  ;  distinguished  from  tone,  53  ;  char- 
acteristic of  certain  clangs,  73  f.  ;  tonal 
component  in,  intensified  by  attention, 
192  ;   question  on,  425. 

Nonius,  see  Vernier. 

Note-book,  laboratory,  xxxi. 

Novelty  of  impression,  as  determinant  of 
attention,  207  f. 

Olfactometer,  fluid-mantle,  142. 

Olfactometric  method,  119,  131  ff. 

Olfactory  sensation,  classificailon  of,  112, 
114;  lists  of  stimuli  for  laboratory  use, 
113,  121,  122  f.,  125,  126,  127  f.,  131, 
137  f-»  139;  references  on,  114;  the 
field  of  smell,  114  ff.;  determination 
of  qualities  by  method  of  exhaustion, 
119  ff.;  compensation  of,  131  ff. ;  ulti- 
mate qualities  of,  136;  mixtures  of, 
136  ff.;  contrasts  of,  139  ff.;  instru- 
ments, 142;    questions  on,  423,  427. 

Open  pipe,  pitch  of,  68;  use  of,  in  work 
on  sound  localisation,  371. 

Optical  illusions,  geometrical,  problem  of, 
.  303;  method  of  work  upon,  304  f.; 
bibliography  of,  305  ff.,  328;  wall  dia- 
grams and  wire  models,  309 ;  of  reversi- 
ble perspective,  310;  variable,  of  ex- 
tent, 313,  321  ff.;  constant,  of  extent, 
315;  variable,  of  direction,  315;  con- 
stant, of  direction,  317;  associative, 
318;  mixed,  318;  physiological  and 
psychological  conditions,  318,  319  f.; 


mechanical-aesthetic  theory  of,  320, 
326;  explanations  of  Muller-Lyer's 
figure,  321  ff. ;  analogues  of  subjective 
accentuation,  346. 
Organic  sensation,  references  on,  143; 
systematic  importance  of,  143;  sensa- 
tion of  muscular  contraction,  143  ff.; 
questions  on,  422  ff.,  425,  427  f. 

Pain  spots,  cutaneous,  experimental  deter- 
mination of,  94  ff. ;  introspective  charac- 
terisation of  pain  sensation,  95 ;  map  of, 
97 ;  sensation  of '  secondary  pressure,'  97 ; 
electrical  stimulation  of,  97;  Kiesow's 
painless  area,  98;   references  on,  98. 

Paired  comparisons,  method  of,  in  affec- 
tive work,  151  ff.;  results  of,  153,  155; 
references  on,  154;  in  work  on  tonal 
fusion,  332. 

Papers,  grey,  usual  defects  of,  32. 

Papillae,  fungiform,  selective  sensitivity  of, 
loi ;  mechanical  and  electrical  stimula- 
tion of,  103;  circumvallate  and  filiform, 
sense-reactions  of,  103;  results  of  work 
on  fungiform,  104;  references  on,  104  f. 

Paradoxical  cold  sensation,  86;  resistance 
and  weight,  143;   localisation,  381. 

Partials,  odd-numbered  more  easily  heard, 
75 ;  special  factors  in  discrimination  of, 
75  f.;  methods  of  observing,  76  ff. 

Perception,  genesis  of,  208,  229  ff.;  three- 
fold problem  of  (analysis,  mode  of  con- 
nection, history),  228  ff.;  difficulty  of 
its  study,  229;  Wundt's  genetic  theory 
of  space  perception,  230  f.;  Stumpf's 
theory  of  the  tonal  fusion,  231  f.;  visual 
space,  232  ff. ;  meaning  of  *  theory '  in, 
257;  method  of  study  of,  303  f.;  audi- 
tory (qualitative),  329  ff. ;  (temporal), 
337  ff-;  (spatial),  356  ff.;  tactual  space, 
373  ff.;  questions  on,  423  f.,  429. 

Performances,  characteristic,  of  various 
instruments,  74. 

Perimeter,  Wundt's,  26. 

Periodicals,  the  five  essential,  430  f. 

Perspective,  in  optical  illusions,  310  ff., 
313  ff.,  324,  429. 

Physics,  xxiii. ;  of  an  open  pipe,  68;  of  a 
sounding  string,  76;  of  sympathetic 
vibration  of  strings,  79;  questions  im- 
plying knowledge  of,  422  f.,  424  f. 


Imdtx  of  Subjects 


453 


OCT.  (;  255:  <)M«ftoMCHW4ai, 

Pitcli.  uf  MMie,  53;  of  hmii^  complwc, 
57  •.;  chanurtermtk  of  daagi  of  cecUia 
iaMrainenu,  73;  vairiatiott  of^  character- 
irtic,  74;  ▼mhatioa  oC  CkToon  aaalytit 
of  dangi»  336;  of  futioo,  337. 

FkchHitflcreQce  of  the  c«n»  aoccc«ive 
hearingt  61 ;  limaltaBeoat  hearing,  65. 

FletbytoMgniph,  nie  of  Fnuick*a,  180  f.; 
ti«d«g»,  iSi  L\  Lombard  and  Pill*- 
bniT^iSi. 

PBcaBMgnq>h«  Verdin's,  184;  Somner*!, 
184- 

Practke,  in  laitework,  to6;  to  be  itttdied 
by  method  of  reaction,  318,  336: 
lion  uf  the  practised  con- 
236  f.;  eflecti  of,  337;  in 
tactoal  localisation,  373. 

Pressure  intensitj,  objectire  and  sabjec- 
tire,  383. 

PresBore  qx>ts,  experimenul  determina- 
tion of,  93  AT.;  relation  of,  to  hairs, 
93,  96;  tuning  of,  93;  pressure  sensa- 
tions from  hairless  areas,  93  f.;  Hall's 
kinestmeter,  93  f.;  references  on,  94; 
map  oC  96;  electrical  stimulation 
fA,  97;  general  distribution  of,  380; 
qnestions  on,  422,  435,  428. 

Primacy,    as    condition    of    association, 

409. 

Primary  position,  determination  of,  247. 

FKndoacopes,  total-reflexion,  295  ff.; 
Wlicatstone's,  295;  Dove's,  395;  opti- 
cal principles  of,  396:  mirror,  396  fi.\ 
Wheatstone's,  396;  Ewald's,397:  Strat- 
toa's,397;  Jastrow's  (perspectoscope), 
398;  lenticular,  398  f.;  NN'heatstonc's, 
398;  Wood's,  399;  adjustment  of  toul- 
reBexioo,  399. 

Ptettdoacopic  angle,  321. 

Plendoscopic  effect,  when  obtained,  300, 
303;  limit  of,  303. 

I^ychodometer,  Obersteiner's,  327. 

Fqrchology,  systematic  and  experimenul, 
xxxiii,  3,  36:  the  teaching  of,  i ;  aHec- 
tiTe,  difficulties  of,  149  f. ;  of  faculties, 
187  f^  354;  popular,  330;  English  and 
German,  attitude  of  to  the  association  of 
ideas,  404:  questions  on,  432,  427;  see 
Introtpectiun.  Method,  Perception,  etc. 


ftychophytks,  of  attention,  907  f.;  of 
tonal  ftisioa,  231 1\  queskioa  on  psycho- 
physical paraUelinn,  438. 

Pnrkhtge  phenomenon,  6  f . 

Pttrkinje*s  imagea,  334  ff.;  experiment 
on  intracranial  localiiation  of  sound, 
359  f. 

Qualitative  and  quantitative  work,  dis- 
tinction between,  xxii.  ff. ;  mcthufls  in. 
xxiv.;  illustrated  by  the  reaction  ex- 
periment, 212;  by  work  on  localisation 
of  sound,  356  (1^  365. 

Qualitative  perceptions,  instances  of,  91, 
129;  difficulty  of  analysis  of,  339. 

Qualities,  six  ultimate,  of  sight,  5,  7  f., 
136;  four,  of  cutsneous  sensation,  81 ; 
four,  of  taste,  99,  103,  136;  ultimate,  of 
smell,  136;  of  affi:ction,  149  f.;  reac- 
tion to  qualities  and  intensities,  326; 
change  of  quality  as  determinant  of 
rhythmisation,  349,  355 ;  of  association, 
430. 

Questionary,  psychological,  begins  with 
Galton,  387 ;  requirements  of  a  success- 
ful,  387  f. ;    what   it   can  *  accomplish, 

388  flf. ;  instances  of  (Galton,  Starbuck  ), 

389  i. ;  and  intros{)ection,  389  f.;  scope 
of,  in  various  tieUIs  of  psychology,  390; 
used  by  Darwin  for  expressive  move- 
ments, 390;  that  employed  in  the  text, 
391 ;  value  of  additional  remarks,  388, 
392;  refinement  of,  395  f. 

Quincke's  tubes,  pitch  and  tuning  of,  66, 
68,72. 

Reaction  experiment,    functions  of,  214, 

226;  temporal  norms  of,  216;  tosound, 

214  ff.;  to  pressure,  223;  to  sight,  223  f.; 

to  smell  and  taste,  335;  to  pain,   326; 

to  intensities,  224  f. ;  with  and  without 

the  signal  for  attention,  224. 
Reaction,  muscular  or  abbreviated,  313  f., 

221  ff.;  favoured  bysubjective  type, 21C: 

specimen  results,  333 ;    references  on, 

335. 
Reaction,  natural  or  central,  314  ff. 
Reaction,   sensorial  or  complete,  313  f., 

3 1 8  ff . ;  favoured  by  objective  type,  216; 

specimen  results,  330  f.;  references  on, 

335. 


454 


Index  of  Subjects 


Reactions,  erroneous  and  premature,  222. 
Recency,  as  condition  of  association,  409. 
References,  literary,  xxxiii. 
Regard,  movements  of,  in  optical  illusions, 

314;  attraction  of,  321. 
Relationship,  direct   and   indirect   clang, 

332;  psychological,  417. 
Relativity,  principle  of,  in  optical  illusions, 

327- 

Reproduction,  as  dependent  on  attention, 
192  f.,  409;  of  general  terms,  378  f. 

Resonators,  the  ears  as,  66;  use  of,  for  ob- 
servation of  partials,  76  ff.;  forms  of,  77; 
alter  the  tonal  complex  observed,  78; 
Koenig's,  77,  80. 

Respiration,  as  index  of  affection,  184 ; 
and  attention,  199  ;  and  rhythm,  354. 

Results,  general  remarks  on,  xxxii. 

Retinal  image,  formation  of,  233  f. ;  inver- 
sion of,  233. 

Rhythm,  problem  of,  337  f.;  instruments 
for  study  of,  338,  349;  subjective,  339  ff., 
346,  351 ;  its  conditions,  340;  reports  of 
unpractised  observers,  341  ff.;  elements 
in  apprehension  of  rhythm,  346;  normal 
grouping  in,  346;  natural  period  of 
rhythmical  unit,  346  f.;  vicarious  oper- 
ation of  intensity,  duration  and  interval, 
348,  35 1 ;  discs  for  use  with  tuning-fork 
and  resonator,  350;  results,  35 1;  illu- 
sions of  rate,  interval  and  intensity  of 
metronome  beats,  351  f. ;  perception  or 
emotion,  352 ff.;  programme  of  further 
work,  354  f.;  subjective  tactual  rhyth- 
misation,354;  rhythms  of  eye-movement, 
355;  of  walking,  355;  references,  356. 

Rise  and  fall  of  tones,  characteristic  of 
certain  clangs,  73;  of  auditory  sensa- 
tions, 338. 

Rivalry,  of  contours,  283  f.,  290;  of  colours 
(retinal  rivalry),  191,  289  ff.;  and  lustre, 
287. 

Sanson's  images,  235  f. 

Scheiner's  experiment,  237  ff.,  254. 

Sensation,  subject-matter  for  psychology, 
3;  nature  of,  4;  not  genetic  unit,  4; 
not  functional  unit,  4;  and  perception, 
4;  paradoxical,  of  cold,  86;  problem  of 
sense  fatigue,  128  f.;  paradoxical,  of  re- 
sistance and  weight,  143;  kinaesthetic. 


144;  normal  state  of,  189  f.;  'brought 
out*  by  attention,  191 ;  see  Articular 
sensation,  etc. 

Sense-connex,  proposed  equivalent  for  per- 
ception, 228. 

Serial  method,  in  affective  work,  154  ff.; 
references  on,  158. 

Singing  in  the  ear,  pitch  of,  66;  intensi- 
fied by  attention,  192. 

Smell,  field  of,  114  ff.;  objective  sources 
of  error  in  mapping,  115,  116  f. 

Smell  compensations,  131;  mixtures  and 
rivalries,  136;  mixtures,  permanent  and 
impermanent,  137  f.;  contrasts,  139; 
images,  393;   questions  on,  423,  427. 

Smell  stimuli,  lists  of,  113,  121,  122  f., 
125  ff.,  131,  137  f.,  39;  characteristics  of 
india  rubber,  132;  for  affective  work, 
160,  171. 

Smoking  stand,  universal,  174. 

Sommer's  tridimensional  movement-ana- 
lyser, 161. 

Sonometer,  tuning  of,  76;   Koenig's,  80. 

Sound  cage,  358  f . ;  Preyer's  helmet,  359; 
accuracy  of  cage  settings,  360. 

Sounds,  intrinsically  non-spatial,  365. 

Space,  theories  of,  229;  Wundt's  genetic 
theory  of,  230  f.;  as  attribute  of  visual 
and  cutaneous  sensations,  230;  auditory, 

365- 

Spectrum,  introspection  of,  7  f. ;  use  of,  in 
psychology,  9;  question  on,  425. 

Sphygmograph,  von  Frey's,  183,  185. 

Sphygmomanometer,  Mosso's,  182,  184. 

State  of  consciousness,  attention  as  a, 
189  ff.;  practice  as  a,  226  f.;  see  Ex- 
pectation, Fatigue,  Habituation. 

Stereograms,  depth  values  of,  262  f. 

Stereoscopes,  WTieatstone's,  261,  264  f.; 
Brewster's,  268  f.,  271 ;  Holmes'  modi- 
fication of,  269;  comparative  value  of 
reflecting  and  refracting,  270  f.;  Dove's 
converting,  295;  Jastrow's  (perspecto- 
scope),  298. 

Stereoscopic  slides,  for  Wheatstone's  stere- 
oscope, 267;  list  of,  recommended  for 
Brewster's  stereoscope,  273  f.;  illustra- 
tions of,  274  ff.,  287  f.;  Wheatstone's 
figure,  278  f.;  Hering's,  in  proof  of 
positive  nature  of  the  black  sensation, 
291. 


Indfx  of  Subjects 


4S5 


Steftotcopic  visioii,  and  atteadott,  191 ; 
prablem  of,  257  f.;  fr«e  iterroMOpjr, 
l$8  L;  convergence  enaier  ami  better 
than  parmUel  viaion,  as9i  simple  aida  to, 
359  f.;  ilUfcreace of  aUe  between  com- 
bined  and  lateral  imagca,  a6i ;  locaUsa- 
tion  of  combined  image,  a6a;  refereacea 
on,  994  f. 

8teteoacopy,  monocular,  99a  f^  994. 

Stoinfi,  flfmpathecic  vibration  of,  78. 

8hMlrBt,  preparation  of,  in  introq>ectk>n, 
ni.;  in  paycbological  and  related 
Coonea,  xxvi.  f.;  typet  of,  xxvii.  ff.;  ad^ 
vantagea  of  thb  Coorae  to,  xxix.;  rules 
for  bflnre  of,  xxx.  f.;  tuggettibility  of, 
nxL;  not  to  be  misled  by  conflict  of 
tbeoriea,  257;  attitude  of,  in  introapec- 
tion  of  auditory  space,  365. 

Suddennem  of  imprcmion,  as  determinant 
of  attention,  207. 

Soggeation,  method  of  indirect,  in  work 
on  rhythm,  344;  psychology  of,  385. 

Summation-tones,  70,  72. 

Synergies,  specific,  in  Stumpfs  theory  of 
tonal  fusion,  231  f. 

Tachistoacopes  200 U\\\\  disc-tachisto- 
acope,  calculation  of  exposure  values 
for,  ao2;  requirements  of  a  good  instru- 
ment, 203  f. 

Taste,  associative  elements  in,  112. 

Taste  qualities,  independence  of  the  four, 
103  f. ;  limited  number  of,  proved,  105  f. ; 
neutralisation  of,  loi,  no;  synthesis  of, 
liof.;  question  on,  427. 

Taste  sensitivity,  distribution  of,  over  the 
tongue,  99  ff.;  concomitant  sensations 
and  perceptions,  102. 

Taste  stimuli,  list  of,  105;  for  aHective 
work,  163. 

Tekstereoscope,  Helmholtz',  265,  272. 

Temperament,  doctrine  of  affective,  402; 
of  intellectual,  417. 

Temperament,  just  and  equal,  79. 

Temperature  sensitivity,  d^rees  of,  87; 
mapa  sho%ring,  88;  continuous,  under 
areal  stimulation,  89;  possible  part 
pkyed  by  association  in,  90. 

Tcaperature  spots,  method  of  determina- 
tion,  82  ff.;  instruments  employed  in 
83  f.;    distribution  of. 


84:  introspection  of  cold  and  warm 
aensations.  84;  tuning  of,  84;  mechani- 
cal stimulation  of,  8$;  analgeaia  of,  8$; 
response  of,  to  inadc«}uatc  thermal  stim* 
nlation,  85  f.;  references  on.  86  f.;  re- 
of,  to  areal  stimulation,  87  f.; 
of,  96;  disturbing,  in  localisation 
work,  373.  375»  38o»  3*«J  qnasUonson, 
4aa.4a8. 

Theories  of  perception,  etc^  value  of,  257. 

Time,  idea    of,  338,  401;    illusions  of, 

35«f. 

Tonometer,  Appunn's,  80. 

Torsion,  244  f.,  248,  250;  false,  248  f., 
250  f.,  318. 

Tropt>stereoscope,  Ludwig's,  272  f. 

Tuning-forks,  effect  of  temperature  on,  57, 
64;  determination  of  pitch  of,  61 ;  ap- 
plication of  wax  to,  64:  rise  of  pitch  of, 
as  tone  rings  off,  80;  Ktenig's,  80;  tech- 
nique of  work  with,  in  fusion  experi- 
ments, 332. 

Type,  subjective  and  objective,  xxvii.  ff.. 
215  f..  402. 

Types,  in  reaction  work,  219,  222;  refer- 
ences, 402. 

Unmosicalness,  tests  of,  333. 

Variation,  mean,  217,  361. 

Varnishing  tray  and  drying  rack,  for  ky- 
mograph, 176. 

Vernier,  application  of,  to  time,  213. 

N'isual  analogues  of  subjective  accentua- 
tion, 346. 

Visual  sensation,  references  on,  5 ;  prob- 
lems of,  6f.;  development  of,  26;  col- 
our mixture,  9  ff.;  campimetry,  17  ff.; 
blind  spot,  27  ff. ;  determination  of 
macula  lutea,  30;  contrast,  30  ff. ;  after- 
images, 37  ff.;  and  Wundt's  theory  of 
visual  space  perception,  230;  questions 
on,  421  ff:,  424  f.,  427. 

Visualisation,  error  of,  in  touch  work, 
373  f.f  380;  references,  382  f. 

Vividness  as  condition  of  ass<x:iation,  409. 

Volume,  bodily,  as  index  of  affection, 
171  fl. 

Warm  spots,  map  of,  96;  su  Temperature 
spots. 


456 


Index  of  Subjects 


Water,  distilled,  taste  of,  loo  f. 

Wax,  laboratory,  composition  of,  56;  use 
of,  in  experiment  on  pitch-difference  of 
the  ears,  62  f. ;  in  ear  plugging,  364. 

Weber's  experiment  on  intracranial  locali- 
sation of  sound,  370. 


Weber's  law,  372. 

Wheatstone's  figure,  278  f. 

Words,  as  expression  of  introspective  data, 
xxxi.;  reproduction  of  general,  378  f.; 
method  of,  in  work  on  types  of  idea, 
394  f.;  word  association,  415,  426. 


2525  4 


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