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A Manual of Laboratory Practice 





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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. 



AU rtgklt rt$tr*t^ 

Copyright, 1901, 

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 



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. 




§ 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 







§ 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 


§ 14. Auditory Sensation 

Experiment V 
$15. The Phenomena of Interference : BeaU 



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 


§ 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 


§ 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 



I 50. Olftctory Sensation 1 1 j 

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 

§ 34. Organic Sensation 143 

Experiment XX 
§35. The Sensation of Muscular Contraction 143 

§ 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 

Experiment XXV 


§ 43. Attention 186 

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




§ 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 


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 


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 



Experiment XXXVI 
f 57. Ideational Types 387 

Experiment XXXVll 
f 58. The Association of Ideas 402 


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$ 





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 


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 


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 


§ 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 

§ 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- 

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 

Umitruk i o iM tMpf m dlkkkHt : 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 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 

(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 

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- 

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. 



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 

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 

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 

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 

(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 


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. 


§ 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' 

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

W + 32o°Bk 

_ 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- 

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. 

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. 


§ 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. 







^ *^ 







^ black - 12 " 

ti u *< 1 1 ^ 




13 " 

11 " 



" yellow" II " 

u u u 12 ** 


Visual Sensation 

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


























yellow at 

2 cm 


U ii 

2 « 


red " 

I " 


(( a 

2 " 


black ** 

8 " 


ii a 

8 " 


yellow « 

8 « 


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 

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 « 


Incoming " 

« II 

Incoming " 

.. ,2 a 



u red " 7 " (24° 51') 

Outgoing " 

I « 



" black " 6 « (21° 40') 

Incoming ^ 

" 12 " 



** 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') 




18 " 



" green- 7 " (24° S^') 




I " 



" white " 8 « (27° S3') 




18 " 



« 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 

\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 : 

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 

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. 


§ 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 

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 


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

(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 


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 

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): 


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 


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 

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 

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, 

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. 


{ 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 

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 

(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 

* 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 

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 

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 

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 

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. 

10 « 

18 ^ 

IS « 

23 ^ 

30 " 

25 « 


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 
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 

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 

(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 

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). 

Auditory Sensation 

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

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 


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. 


§ 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. 

(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 


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). 


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 

3. Beating tone an intermediate low 

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

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 


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- 

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- 

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. 


§ 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 

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 - " •• 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. 


§ 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) 

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


§ 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 


DwDMCB 09 Tnan I>iws»> 

Triple octmve and major ^ 
Mrrenth m 


Double octave and 
uor third 

Double ocuvc 


Major eleventh— 


Major sixth 


Major third ■¥ 

Major seooiid+ 








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 : 


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- 

(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 


Minor second + 

Major second + 
Major third 



.\iajor si.xih + 


Ocuve and major third 

Octave and fifth 

Double octave and ma- 
jor second 

Triple ocUve 

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







i^ 3:4 

\T 32:45 

^ 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 

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 


Dbtamcb or FtMT Diwbii* 
imKiTOMB AwnrB Lowsa 

Major second + 
Mi^or third 
Tritone - 

Major sixth 
Major seventh — 

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



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 

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. 


{ 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 

( 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. 


§ 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 

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 

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). 


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. 


§ 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 


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. 


Cutaneous Sensation 

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

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 

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 

§ 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. 


$ 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. 


Cittaneous Sensation 

3 j 






3 ^ 




r 2 ^ 

C ^ 



( ^ 








C 1 




( ® 




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- 

§ 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 

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 


§ 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 

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 


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. 


§ 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 

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. 


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 


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. 

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 


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 

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) 

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- 

(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. 


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 : 


Weak solutions : 







I . . 

. . + 





2 . . 

. . ? 



3 • • 

. . ? 



— (cold) 


4 . • 

. . + + (weak) 






Strong solutions 


I . . 

. . + 



— (sting) 


2 . . 

. . — 

- (sting) 


+ + 


3 • • 

. . + 



+ + 

— (cold) 

4 . • 

. . + 



+ + 


(3) Weak solutions, with spread of stimulus owing to too 

large brush 

2 . . . . 

3 . . . . 

4 . . . . 

5 . . . . 


+ + 

+ + 


+ + 


+ + 


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. 


{ 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 

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. 


§ 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 


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. 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. 



§ 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. 


§ 30- Otfactary Sensation 


maker's Ust 

Aimo9utf CO.. . . 
AmdtTf CO.. . . 
Aminonium sulphide 
Atme, e. o. 
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. . 




(2) Cy a. 


(2) ^, /9. 
(2) ^, iS- 


(2) c, p? 
(2) <-, a. 

(2) dy a. 

(2) ^ )». 

(2) d, p. 
(2) ^, ^. 


(2) ^ a. 



(3) ^, /3. 
(2) b, a, 
(2) <:, a. 




(9). 7. 


(2) dy a. 


(3) ^ *• 

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. . 



nuikcr't Ust 
(pp. 933-*3i) 

(8) a. 
(2)r, y; 
(2) d, p. 


(2) b, p. 

(2) d, p. 

(3) ^ P- 

(2) a; 

(2) ^, p. 
(2) a. 
(6) a. 

(2) d, a. 
(2) a. 
(2) rf, a. 
(2) a? 
[(4) ^?]. 

(2) Cy P? 

(2) ^, i8. 

(3) ^. )8. 
(3) ^ )8. 
(2)<r, y; 
[(2) «?]. 
(6) a. 


(3) ^ P- 
(2) O )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. 


§ 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 


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 

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 


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 

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- 

(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 

(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. 


Crab-apple blossom 

2 min. to 3 min. 


White roM 

I min., 30 sec. to 2 min. 



4 min. to 6 min. 


Ammonium sulphide 

6 min. (4 to 5 min.) 


Carbon disulphide 

5 min. to 5 min., 30 sec. 



I min., 30 sec. to i min., 55 sec 


Stale cheese 

7 min., 45 sec. to 8 min., 30 sec 


Tincture of iodine 

1 min., 30 sec to 2 min., 15 sec (4 min.) 


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 

(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 

(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 

(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. 


Olfactory Sensation 

Experiment (3), — The following are typical series : 

Tincture or Iodink. 


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 . 


" " " tenth I min. rest . 

. 19 

" " " eleventh i min. rest 

• 13 

" " " twelfth I min. rest . 

• 13 

" " " thirteenth i min. rest 


Spirits of Camphor. Sec. 

Exhaustion time 105 

" " after first 2 min. rest 


" " " second 2 min. rest . 

• 52 

" " " third 2 min. rest . 

. 46 

" ■ " « fourth 2 min. rest . 

. 38 

" « " fifth 2 min. rest . 


" " " sixth 2 min. rest . 


" " " seventh 2 min. rest 


" " " eighth 2 min. rest . 


" " " ninth 2 min. rest . 


" " " tenth 2 min. rest . 


« " « eleventh 2 min. rest 


" " " twelfth 2 min. rest . 


" « " thirteenth 2 min. rest . 


" « " fourteenth 2 min. rest . 


" " " fifteenth 2 min. rest 


Others will be found in Aronsohn, pp. 344-346. 

{ 32. Smeli Exhaustion 


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. 








CM. petroselini 

• + 









OL terebinth 







01. caryophyllonim .... 







01. cajeputi . . . 

• + 






Flower perf. jasmin* 







01. nita? . . 







01. pinus picca 







01. la\*and. gallic 







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 

(•) + 







• + 







Olfactory Sensation 

The following Table shows, somewhat more fully, the results 
obtained from another O. 


Previous Tudg< 

ment of O 
•s to Intensity 
of Stimulus. 

Exhaustion by 





CI. cajeputi 

Flower perf. 

of. rutae 
Ol. pinus picea 

Ol. copaiTZ 

OI. juniperi 

Ol. macidis 

Ol. foeniculi 

Ol. citri 

Musk (natur.) 

Flower perf. 

Ol. aurant. 

Ol. succini 
Musk (artif ) 

01. rosmarini 


Ol. anisi stel> 

Flower perf. 

ylang ylang 
Ol. carvi 
Flower perf. 

Ol. lavandulac 

Ol. bergamot- 


Eau de Co- 
Ol. salvias 
Alcohol 95 % 
Ol. petroselini 
Ol. terebinth. 
Ol. caryophyl- 



Heavy and 


Rather strong 

Rather strong 

Weak and pene- 
Rather strong 


Strong and 

Rather strong 







Rather strong 




Weak and 








* Rather 


(*) Same 








' Weaker 








♦ Weaker 




♦ Nothing 
























Not so 




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- 

(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. 


$ 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, 


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 


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 

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 


10. o cm. A' compensates 

In the direction KXo B 

u a « a 


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 


** Vanilline . . 




•* Listen ne . . 




Musk (nat) and Pyridine . . . 



(6) a. 

Caryophylline and OI. cani . . 



(2) CO. 

Iodine and Ylang ylang . . . 



(3) <^ 

** Camphor .... 



(2) a. 

Camphor and Ol. aurant. dale. . 


(2) a, 

(2) ^tp. 

♦* 01. anisi . . . 



(2) CO. 

« Ylang ylang . . 



(3) ^a- 

" Laudanum . . . 




*< 01. terebinth. . . 



(2) a. 

** 01. juniperi . . 



(2) ca. 

Laudanum and Ol. juniperi . . . 



(2) CO. 

Allyl sulphide . . 




Iodine and Ol. succini 




Valerianic add and Ol. lavandulae 


(2) cy, 

(2) cy. 

•* 01. salviae . . 




** Hyacinth . . 



(3) da. 

Petroleum and Ol. salviae . . . 




Noimxture. — 

Pyridine and Jasmine • ** 

(6) a, 


Hyacinth " 

Valerianic acid and Heliotropine ... " 

(2) ^y, 


Opium and Ol. salviae ** 



Neroli and Petroleum ^ 

(3) «A 
(2) a, 

A^^S^cl MilB^I A VVfl\/SWUSIl •••••■• 

Camphor and Allyl sulphide 

" Petroleum . . 




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 

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 : 

{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 




LIbmb Cm (t). 

Scries I 


6.0 mm. 

5.0 mm. 

A- after ^ 












A' after Z? 






AT after /I 







A- after Z> 




1 0.0 







1 0.0 

/rafter iE" 





1 0.0 




Series III. 




KziXtx L 






K^iX^x M 


















KtAxzx L 






AT after c; 



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 

Questions. — ^^(i) There is good evidence of contrast, in 
results like the above. This evidence tallies with the results of 


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 

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 : 


Limen for C> (i). 

Limen for O (2). 


7.0 mm. 

6.0 mm. 

















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- 


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. 


§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 



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. 

§ 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 

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 

* 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 

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. 


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 


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. 


$ 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 

(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 

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— 


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 

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. 


§ 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 

i6o The Affective Qualities 

The following scents may be recommended 

{a) Pleasant. 

Crab-apple blossom. 

White rose. 

Oil of orange. 

Jockey Club. 


Oil of cinnamon. 

{b) Unpleasant. 

Carbon disulphide. 
Rancid cheese. 
Wood alcohol. 
Castor oil. 
Cod liver oil. 



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 


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 

(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). 


§ 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 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 














































S 1 


B 2 

fl ? 

8 S 

10 . 

8 4 





5 7 


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- 

(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 































8 10 16 20 26 30 35 40 46 60 58 60 86 70 76 

§ 40- y«fimtary Mwtmtnt 


11. • 


















T t 








• A 















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 







a A 







a a 












• < 








2 g 




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 

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 

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 

(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 


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. 




(crab-apple blossom) 
(white rose) 


(carbon disulphide) 
(wood alcohol) 



(oil of anise) 
(spirits of camphor) 


(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 





(oil of cinnamon) 
(oil of anise) 


(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. 


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. 


$ 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 

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 


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. 


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 

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 


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 

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- 


^ 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 

(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. 


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 


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 


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 


maintains this level for some time. If the stimulus be unpleas- 
ant, the curve drops during application, and then drops still 



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 

(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- 

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 

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. 


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- 


§ 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 


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 

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- 

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- 

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 

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 

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 

§ 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 


•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 
s u ppleme n ts 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 

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 


§ 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 

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 

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 


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. 






. -23 

' .21 


.19-.22 sec. 

.I4-.I9 " 
.I2-.18 " 



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." 


Attention and Action 

Results. — The following are typical series. 
(i) First series taken after the 50 'central ^ reactions. 






.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. — 

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 


honest as regards his * muscular * tendencies, and shows marked 
improvement as the series progpresses. 

(a) Fifth 





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.— 

Idea of sound as before ; idea of result just comfortableness 
and of-course mood. — Good. 

False stimulus ; no tendency to movement, and no mental 

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. — 

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- 


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. 




.12 sec. 























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 

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 

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 

(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. 





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.' 


§ 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 

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 

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 



' *~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 


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 : 


{ 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 


.11 I I 


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) 

{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 


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, 


(</) 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, 

€. 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, 

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 

(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- 

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 

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 


Visual Space Perception 




intersecting ai the centre of the screen. 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 

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 


Fig. 53. — Hering, Bin. Sehen, 67. 

§ 4^. Listing* s Law 



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, 

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 


{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 

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 


§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 


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^ 


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 

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 


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'. 



f\ ■ 

/ A' 


[ \ 


\ A 

\^ 1 \ / 

> D 

V ' / / 

\ / 

\ / 

\\ ' 1 / 

\ ' '/ 



\\' / 

/\ / 



\ /'; 

/ A ^ 




V \ 

1 / \ '' 



1 / \ ' 


/ y 




;/ \ 




y ,'■ 


V I 



/ 1 

1 V 

A » 


' i\ 


/ / ' 

/ \ 

»' \ 

\ V 

/' \ 

/ 1 

/ ' * 




1 \ 
1 \ 
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, 


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 (. 


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- 





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., 

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. 


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., 

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 


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. 

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 


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. 


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- 


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. 


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 


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. 


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 


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, 



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 


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 


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 


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 


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 

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. 



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. 

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- 

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 


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 ? 


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, 

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 


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 

Fia 78. — Dove's converting 

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 


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 


(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. 


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 

300 Visual Space Perception 

Experiment (2). — In every case there is conversion of the 

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 

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 

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). 


{ 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, 

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. 


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, 

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. 

§ 49- Optical IllHsioHS : Bibliography 307 

J. I. Hoppe, Psych.-ph3rs. Optlk, 158* 351. 

A. Kundu Poggendorff*8 Annalen* cxx., 1863, ti8. 

T. Lipps, HelmholU Fcstgniss, 1891, 321 ; Raumacsthetik, 366, 393. 

H. MUnsterberg, Beitriige x. experiment. Psych., 3, 1889, 135. 

J. Oppel, jahresber. d. physikal. Ver. xu Frankfurt a. M., 1854-5, 38. 

£. C. Sanibrd, Course, 335. 

A. ThWr>\ Philos. Studien, xii., 1896, 93. 

W. Wundt, Beitriige z. Theorie d. Sinneswahrnehmung, 1863, 158 ; Phyi. 

Psych., iU 137; Tiiuschungen, 105. 
(5) VmrimbU iUmsitms of Direttion. — H. Aubert, Physiol. Optik, 1876, 630. 
S. BklwelU Curiosities of Light and Sight, 1899, 141. 
£. Burmester, Zeits. f. Psych., xii., 1896, 355. 
J. Delbceuf, Bull, de TAcad. roy. de Bclgique, 3 s<«nV. x\x., 3, 1865, 195 ; 

Revue scientifique, li., 1893, 337. 

F. B. Dresslar, Amer. Joum. of Psych., vi., 1893-5. 275. 
W. Einthoven, PflUgcr's Archiv, Ixxi., 1898, 4. 

W. Filehne, Zeits. f. Psych., xvii., 1898, 15. 
C. L. Franklin, Amer. Joum. of Psych., i., 1887-8, 99. 
A. A. Guye, Revue scientifique, li., 1893, 594. 
H. von Helmholtz, Phys. Optik, 705, 707, 708, 713. 
£. Hering, Hermann's Hdbch. d. Physiol., iii., i, 1879, 373; Beitrage 
z. Physiol., i., 1 861, 73, 79. 

G. Heymans, Zeits. f. Psych., xiv., 1897, loi. 
W. Holtz, Gbttinger Nachrichten, 1893, 159. 
J. I. Hoppe, Psych.-phys. Optik, 74. 

J. Jastrow, Amer. Joum. of Psych., iv., 1 891-3, 381 ; Pop. Sci. Monthly, 

liv., 1898-9, 304. 
O. KUlpe, Outlines of Psych., 1895, 367. 
A. Kundt, Poggendorff*s Annalen, cxx., 1863, I3i, 148. 
T. Lippft, Helmholtz Festgruss, 1891, 267 ; Raumaesthetik, 357 (333, 365, 

307; 307* 3»9; 263, 374, 371) ; Zeits f. Psych., xviii., 189*, 440. 

E. Mach, Beitrage z. Analyse d. Empfindungen, 1886,98; Eng. trans., 


F. C. MUller-Lyer, Du Bois-Reymond's Archiv, 1889, S. B., 363. 
H. MUnsterberg, Zeits. f. Psych., xv., 1897-8, 184. 

J. Oppel, Jahresber. d. physikal. Ver. zu Frankfurt a. M., 1854-5, 41. 
A. H. Pierce, Psychol. Rev., v., 1898, 333; vii., 1900, 356. 

E. C. Sanford, Course, 3 18, 319, 234. 

A. ThiM', Philos. Studien, xi., 1895, 3 '2. 360, 607 ; xii., 1896, 74. 

K. Ueberhorst, Zeits. f. Psych., xiii., 1896-7, 59. 

A. W. Volkmann, Physiol. Untersuchungen im Gebiete d. Optik, L, 1863, 

W. Wundt, Phys. Psych., ii., 144; Tauschungen, 113. 
W. von Zehender, Zeits. f. Psych., xx., 1899, 79, 83, 85, 103. 

F. Zollner, Poggendorff's Annalen, ex., i860, 500; cxiv., 1861, 587. 

3o8 Visual Space Perception 

(6) Constant Illusions of Direction. — F. C. Donders, Arch. f. Ophthalmo- 

logic, xxi., 3, 1875, ^oo. 
H. von Helmholtz, Phys. Optik, 694, 862. 

E. Hering, Hermann's Hdbch. d. Physiol., iii., i, 1879, 355» 37^* 

F. KUster, Arch. f. Ophthalmologic, xxii., i, 1876, 149. 

F. von Recklinghausen, Arch. f. Ophthalmologic, v., 2, 1859, 127. 

E. C. Sanford, Course, 191, 268. 

A. W. Volkmann, Physiol. Unt. im Gebiete d. Optik, i., 1863, 220. 
W. Wundt, Phys. Psych., ii., 129, 141 ; Tauschungen, 130. 

(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, 

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 

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 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 

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 

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 

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 

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- 

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 

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. 

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 


$ 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 ^ ; 
*«; 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. 




A • 


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 ^ 

> < > 




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 


(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 

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. 



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 


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 

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 

(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. 


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 


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. 


§ 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 


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. 






Series i 


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 

Clock movement again. Quite unpleasant sensa- 
tion in head. 

Sound suggested blacksmith's shop. 

Clock again. Annoyed by its rapidity and regu- 

Series 2 



No g[roup 

Attention ^^'andered. 




Suggested clock. 




Rapid clock ticks. 




Normal ticking of clock ; breaking stone. 




Pencil tapping on slate. 








Clock. Sounds seemed to move farther off at end 
of series. 



No suggestion. 
Series 3 



No group 

Clock : also vague suggestion in the sounds. 




Clock ; head swayed backwards and forwards. 



No group 

Beats came at regular intervals, and all alike. 




Regular at first; then the interval between the 
different sets of tick-tocks seemed longer than 
the interval between tick and tock. 



No group 

Beats regular. 




Beats regular at first ; then grew confusing. 




Beats went in couples. Interval between couples 
seemed longer ; but by beating time I proved 
that all the intervals were equal. 



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 

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 

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 

.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- 

>3 -3 4-group Main accent on first beat, with deep in- 

halation. Suggested goblins playing 
on mound. Thought of music and 

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 

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 

For Results, see Bolton, 226. The Instructor must use his 
discretion in the choice of O's for this and the three following 

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 


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 

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 

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- 

(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." 


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). 


§ 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 

§53* Localisatiam of Sounds 


No.or l». 











etc., etc 











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 : 







- I 

+ 5 

+ 3 
+ 4 

- I 

- 3 

+ 3 

m.e.— ->f 0.3 

m, V. ss 3.84 

The introspective reports will hardly contain more than the 

(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 

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 


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. 






















§ 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 

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. 


§ 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. 

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 


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, 


§53* Localisation of Sounds 


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- 



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. 


Tactual Space Perception 


§ 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 

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 


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. 


§ 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. 


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 

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 



Mm. t 































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. 


§ 5S- Discrimination of Two Points 
Left wrist, volar surfue, ^ » 





Mm. t 


a (quickly) 





















2 (ceruin) 







5 Spread out, al- 
( most like i 


At first 3, then i 



Suggestion of 3 ; 


they seemed to 
, run together. 

2 (with hesitation) 



Line or oval ; i 















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 


(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- 

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- 

(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- 


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. 


{ 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 

(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 

(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 


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. 

Ideational Type and the Association op Ideas 


§ 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 


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 

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 

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- 

$ 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- 

(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 


Ssms I. -Won 






WHsidewaik. . 


Rmlromd . . . 

A, O, V 

Fog . 

Dog . 
Ltax*€S . 

\\ V, A 


V, V, P, T 
A. V, O 


V. v,o 
. v,o 


. 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 . 

Chimes . . 
Gas . . . 
State roof . 
Steam whistte 
Inkstand . 








\.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 : 


Auditory Sbribs 

V 12^ 





A, O 2.5 





T .8 




G,M .5 





P 3 





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 

{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 


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 

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) Vi s m al-t mc t dr 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 

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- 

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. 


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. 


§ 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 ^»!:» 


I'tf-trf. fM (/) 




/ V<./r-/, 35 («) 

Calkins, 38. 


SnMvura Cako 

Tut Cako 

Peacock, 46 


Blmt, 38 (») 

B/me (r) 

Brown, 51 


Stra^'bcrry, 85 


Grey, 74 


Yellow, 29 


BIh€, 52 (r) 

Calkins, 39. 


SnMOLvs Gua> 

Test Cakd 

Brown, 34 


Orange, 51 

Dark red 

Green, 792 (v) 


Blue. 19 

Green (v) 

Violet, 48 


GreeHy 69 («) 


Dark red, 54 


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. 


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 


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, 

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* 

( I ) General Table of Correct Associations. 

Number of Series. 

Possible Correct 

Actual Correct Associations : 




7-term 444 
10 to i2-term 867 





(2) Specimen Special Table : Frequency 3:12. 

Number of 

Both Numbers 
Associated : 

Normal only 
Associated : 

Frequent only 
Associated : 




















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^* 

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 

* 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. 


Ideational Type and Association of Ideas 


Total time, x6o sec. ; catch words, 4. 





Mode of 




Point of 



a sec. 




All clear, but 
best in lower 




Visual and 







Verbal - audi- 
tory and vis- 
ual ; but 
chiefly or- 



Full, but 

and I and 



Gurth and 
suppl e- 
mented by 
woods, din- 
ing room 

40 sec. 

Visual, ver- 
organic; the 
forest visual 

Pleasant, so far 
as pictures 
were con- 
cerned; unr 
when I tried 
to remem- 
ber author's 

with asso- 
ci at i ve 

Clear, with 
vague fringe 

Last idea 



Verbal -audi- 
tory, organic 




Last idea 







Last two 



75 sec. 

Visual and 



Word clear; 
details of 
visual im- 
agery indis- 
tinct: full 

Last three 






ness ' thin- 
ner'; im- 
age more 




Visual and 


Similarity ? 


or its im- 



125 sec. 

Visual (and 
motor ?) 



Indistinct in 
detail ; line- 
up clear 



Lehigh and 





Last idea 



tory (calls) 



Very indis- 


Exp. ended 
at 160 sec. 



§ 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- 


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.). 


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. 


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 } 


1. Describe the structure of the cochlea, including the 
arrangement of the terminal formations. Illustrate by dia- 

2. What reasons led Helmholtz to modify his original 
theory of audition.^ 


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 } 


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. 


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 

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 

4. Classify and explain the movements which 'express* 

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. 


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. 


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 

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 


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 ? 


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. 


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 


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 ? 


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. 


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. 


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- 

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? 


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 

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 ? 


1. Define: perception, state of consciousness, mental con- 

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. 

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. 


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. 

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. 


14. E. Hering, beiirage zur i'nysiologic. Leipzig, W. JLugelmann. 1861- 


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.^ 

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. 


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., 

50. A. Zwaardemaker, Die Physiologic des Geruchs. Leipzig, W. Engel- 

ntann. 1895. 


Firms Recommended for the Supply of Psychological 


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, 


2. J. Brandli, 59 Freie Strasse, Basel. (Griesbach's instru- 


3. Cambridge Scientific Instrument Co., St. Tibb's Row, 

Cambridge. (Optical and acoustical pieces ; Galton's 

4. Clark University Laboratory, Worcester, Mass. (Sanford's 


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- 



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 


17. E. B. Meyrowitz, 104 E, 23 Street, New York City. (Optics, 


18. Michigan Apparatus Co., 305 South Main Street, Ann 

Arbor, Mich. (Lombard's and Pillsbury's instru- 

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- 


24. W. Schmidt, Seltersweg 30, Giessen. (Sommer's instru- 


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 



See Part U pp. 207 ft 


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. 

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, 


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*!, 


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 


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 


Riofi, meteU 292. 

Rod, wooden, ptdded at iowcr end, 359. 
Robber tobiai^ 13a, 177 U s^St 3<^ 

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. 


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, 

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, 

Papers, grey, 32. 
Pseudoptics, MQnsterberg's, xxxiii., 260, 

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, 


List of Materials 


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. 

Chair, cane-bottomed, 262. I Desk, skeleton standing, 39. 


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., 

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. 


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, 

B^ich. E^ 329, 333. 
BoBfcltR., 104. 






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, 

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, 

Friedrich, M., 205. 
Funke, O., 82, 143, 433. 

Gale, H., iii. 

Gallon, F., 387 ff., 390 ff., 393, 395, 404, 

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, 

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., 

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 


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 


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, 

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. 
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, 

Ward,;.. 157, 375,433. 
Washburn, M. P., 48, 382, 400. 
Weber, E., 369 f. 
Weber, E. H., 82, 143, 374 f., 382, 425, 

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» 



Abcmtioa, cbroaMtk» 1391 ipheriad, 


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; 
q nw t i oM 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 

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 e x per im ent, 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.