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A TEXT-BOOK OF PSYCHOLOGV
•The
THE MACMILLAN COMPANY
NEW YORK • BOSTON • CHICAGO
SAN FRANCISCO
MACMILLAN & CO., Limited
LONDON • BOMBAY • CALCUTTA
MELBOURNE
THE MACMILLAN CO. OF CANADA, LTD.
TORONTO
A TEXT-BOOK OF
PSYCHOLOGY
BY
EDWARD BRADFORD TITCHENER
THE MACMILLAN COMPANY
1928
All rights reserved
Copyright, 1896, 1897, 1899,
By the MACMILLAN COMPANY.
Set up and electrotyped. Published July, 1896.
Revised Edition Under New Titxk
Copyright, 1909, 1910,
By the MACMILLAN COMPANY.
Set up and electrotyped. Published June, 1909. Reprinted
January, 1910; December, 1911 ; September, 1912; March,
June, 1914; September, 1915; February, October, 191 6; April,
1917; February, 1919; September, 1919; November, 1919;
January, October, 1921 ; April, 1923; March, 1924; October,
1926; August, 1928.
German Translation, 1910.
French Translation, 1923.
PRINTED IN the UNITED STATES OF AMERICA BY
THE BERWICK & SMITH CO.
TO THE MEMORY OF
JOHN SCOTT BURDON SANDERSON
PREFACE
The present work has been written to take the place of
my Outline of Psychology. The Outline f^\{\zh. was stereo-
typed in 1896, had long passed beyond the possibility of
revision, and the continued demand for it showed that
there was still room in the science for a text-book which
set experimental methods and experimental results in the
forefront of discussion. I should have preferred, however
ungratefully, to let the book die its natural death ; for I
feared that it would be impossible to recover the freshness
and vigour of the first writing, and I knew that another
issue would lay an oppressive tax upon future time and
energy. But colleagues and pupils and publisher were
insistent, and I finally decided to rewrite. A first part,
containing approximately half of the new work, appeared
in 1909. For the benefit of those who have purchased
this installment, the second part is now issued in sepa-
rate form. Both parts are comprised in the present
volume.
It was the intention of author and publisher that, on the
completion of the Text-book, the Outline should be with-
drawn from the market. They look forward to this with-
drawal in the near future ; meanwhile, so long as the
steady demand for the book is kept up, the last edition
of the Outline will be held on sale. —
viii Preface
It is, I think, unnecessary to apologise for the increase
in size. If psychology is to be taken seriously, its prob-
lems must nowadays be treated in some detail. Besides,
the Text-book aims, within its limits and upon the elemen-
tary level, at systematic completeness ; it is not a digest or
redaction of a larger work, to which the student may be
referred for further information. I could wish, remem-
bering some of the criticism called forth by the Outline,
that I had a fully elaborated Systematic Psychology to fall
back upon ; but I am inclined to believe that, from the
student's point of view, a text written expressly for the
class-room is more satisfactory than the simplified version
of a book written primarily for psychologists.
The Text-book follows, in general, the lines laid down in
the Outline. The only point that calls for special men-
tion here is, perhaps, the scant space accorded to nervous
physiology. Readers of the Introduction, and especially
of § 9, will acquit me of any desire to minimise the
importance of this subject. But I have always held that
the student should get his elementary knowledge of the
nervous system, not from the psychologist, but from the
physiologist ; the teacher of psychology needs all the time
at his disposal for his own science. It is true that psy-
chology, if it is to be explanatory, must supplement the
description of mental processes by a statement of their
physiological conditions. But then it is also true, unfortu-
nately, that any such statement, in the present condition
of our knowledge, must be largely hypothetical. In a
comprehensive work, discussion of the various physiologi-
cal theories, for instance, of feeling and attention would
be altogether in place ; to discuss them with beginners
strikes me, I confess, as a sheer waste of time. My own
Preface ix
plan is to show, by reference to the theory that appeals to
me at the moment as the most plausible, how in principle
an explanation is to be worked out. But I am careful to
say that the theory itself is simply guess-work, that many
other guesses have been made, and that there is a great
gulf fixed between established physiological fact and the
secondary constructions of physiological psychology.
A special feature of the Outline was^the paragraph,
entitled " Method," in which I showed how the reader
might test for himself the statements made in the. Section
to which it was appended. Some of the methods thus
described had been worked out only in my own laboratory ;
their technique was crude and their range of application
restricted. Now, after fourteen years, the variety and
refinement of method are so great that an adequate treat-
ment, within text-book limits, is out of the question. Never-
theless, it is important that the student be instructed in
method. And if I might offer a suggestion to teachers
of psychology who propose to use this book in the class-
room, it would be that they go behind my discussion, now
and again, to the original sources. A topical lecture, that
gives a critical account of the plan, method and results of
some single investigation, is not less interesting and may
sometimes be more valuable than a logically proportioned
review of the entire subject-matter of a Section.
My thanks are due to my wife, and to my colleague, Pro-
fessor Madison Bentley, for constant advice and assistance
during the preparation of the Text-book. I dedicated the
third edition of the Outline to the Regius Professor of
Medicine in my old university; it was he who, in 1890,
suggested the writing of the book. Sir John Burdon
X Preface
Sanderson has now laid down a life full of years and
honours. I owe him — as who of his pupils does not ? — •
a heavy debt of gratitude ; and I dedicate the Text-book to
his memory.
Cornell Heights, Ithaca, N.Y,,
July 15, 1910.
CONTENTS
SUBJECT-MATTER, METHOD AND PROBLEM
OF PSYCHOLOGY
PAGE
§ I. Science and Experience i
§ 2. The Subject-matter of Psychology 6
§ 3. The Common-sense View of Mind ....... 9
§ 4. Psychophysical Parallelism 13
§ 5. Mental Process, Consciousness and Mind 15
§ 6. The Method of Psychology 19
§ 7. The Scope of Psychology 25
§ 8. The Use of Analogy in Psychology 30
§ 9. The Problem of Psychology 36
References for Further Reading ....... 42
Note on the Classification of Psychology 4j
SENSATION
§ 10.
§11.
§ 12.
§13.
§ 14-
§15.
§ 16.
§17-
§18.
The Elementary Mental Processes
Elements and Attributes .......
The Attributes of Sensation
The Classification of Sensations
References for Further Reading cy
The Quality of Sensation: Vision
The Visual Qualities ^g
Visual Stimulus and Visual Sensation 64
The Dependence of Visual Sensation upon Wave-length and
Energy of Light 65
The Dependence of Visual Sensation upon Composition of Light 67
The Dependence of Visual Sensation upon the Time and Space
Relations of Stimulus 7 1
c: m^
4^
/■
xii Contents
PAGE
§ 19. Daylight and Twilight Vision • . 78
§ 20, Indirect Vision and Colour Blindness . . ... .80
§ 21. The Primary Colours 85
§ 22. Theories of Vision .........87
References for Further Reading .......92
Audition
§ 23. The Auditory Qualities 93
§ 24. The Dependence of Auditory Sensation upon Wave-number of
Sound
97
§ 25. The Dependence of Auditory Sensation upon Composition of
Sound 100
§ 26. Beats and Intermediate Tones 103
§ 27. Combinational Tones 106
§ 28. Theory of Audition . 109
References for Further Reading I13
Smell
§ 29. Sight and Hearing, Taste and Smell 1 14
§ 30. The Olfactory Qualities 117
§ 31. Olfactory Sensation and Olfactory Stimulus . , , . .119
§ 32. The Dependence of Olfactory Sensation upon the Composition
and Time-relations of Stimulus , I2I
§ 33. Theory of Smell 125
References for Further Reading ....... 128
Taste
§ 34. The Gustatory Qualities , , .129
§ 35. Gustatory Sensation and Gustatory Stimulus . . . • 131
§ 36. Mixtures and Adaptations .■ .133
§37. Theory of Taste 138
References for Further Reading ....... I42
Cutaneous Senses
§ 38. The Skin and its Senses ........ 143
§ 39. The Pressure Sense . , 146
Contents xiii
PAGE
§ 40. The Temperature Senses . . . . . , , .149
§ 41. The Pain Sense .......... 152
§42. Theory of the Cutaneous Senses 155
§43. Tickle and Itch 157
References for Further Reading 159
Kinesthetic Senses
§ 44. The Kinsesthetic Senses 160
§ 45. The Muscular Sense , 162
§ 46. The Tendinous Sense 163
§ 47. The Articular Sense . . . . . . . . .164
§ 48. Movement and Position, Resistance and Weight . . . .166
''§49. The Alleged Sensation of Innervation ...... 169
§ 50. Some Touch-blends . . . . . . . . .171
References for Further Reading . . . . . . .172
§51. The Kinaesthetic Organs of the Internal Ear , . . .173
§ 52. The Ampullar Sense . 174
§53. Theory of the Ampullar Sense 176
§ 54. The Vestibular Sense . . .178
§55. Theory of the Vestibular Sense ....... 180
References for Further Reading 182
Other Organic Sensations
§ 56. The Sensitivity of the Abdominal Organs
§ 57. The Sensations of the Digestive and Urinary Systems .
§ 58. The Sensations of the Circulatory and Respiratory Systems
§ 59. The Sensations of the Genital System ....
References for Further Reading
183
187
189
191
193
Synaesthesia
§ 60. Synaesthesia • • • • . 194
§ 61. The Image • * • . . 197
References for Further Reading 200
The Intensity of Sensaiion
§ 62. The Intensity of Sensation 201
§ 63. Mental Measurement ......... 207
XIV
Contents
§ 64. Liminal and Terminal Stimuli
§ 65. The Just Noticeable Difference as the Unit of Measurement
§ 66. Weber's Law
§ 67. Theory of Weber's Law
PAGE
210
213
215
221
References for Further Reading 224
AFFECTION
§ 68. Feeling and Affection
§ 69. Affection and Sensation . . . .
§ 70. Other Views of Affection . . . .
§ 71. The Methods of Investigating Affection
§ 72. The Tridimensional Theory of Feeling .
§ 73. The Dependence of Affection upon Stimulus
§ 74. The Bodily Conditions of Affection
References for Further Reading .
225
228
236
240
250
257
260
263
ATTENTION
§ 75. The Attentive Consciousness .......
§76. The Development of Attention
§ 77. The Two Levels of Consciousness ......
§ 78. The Kinsesthetic and the Affective Factors in the Attentive Con-
sciousness ..........
§ 79. The Experimental Investigation of Attention . . • .
§ 80. The Range of Attention
§81. The Duration of Attention
§ 82. The Degree of Attention
§ 83. Accommodation and Inertia of Attention . , . . .
§ 84. The Bodily Conditions of Attention
References for Further Reading
265
268
276
281
284
287
291
293
296
299
302
Contents xv
PERCEPTION
Spatial Pekceptions
PAGE
§ 85. The Sensory Attribute of Extent ...... 303
§ 86. The Third Dimension 306
§ 87. The Stereoscope. 316
§88. The Perception of Space : LocaHty 321
§ 89. The Perception of Space : Magnitude 326
§ 90. Secondary Spatial Perceptions 330
§ 91. Illusory Spatial Perceptions 332
§ 92. Theories of Space Perception 335
References for Further Reading 338
Temporal Perceptions ^
§ 93. The Sensory Attribute of Duration ...... 340
§ 94. The Perception of Rhyth.n 344
§ 95. Theories of Time Perception ....... 346
References for Further Reading 347
Qualitative Perceptions
§ 96. Qualitative Perceptions ........ 34^
§ 97. Tonal Fusion 351
§ 98. Theories of Qualitative Perception 352
References for Further Reading 355
Composite Perceptions
§ 99. Simple and Composite Perceptions 357
§ 100. The Perception of Movement ....... 357
§ loi. The Perception of Melody . » > 360
References for Further Reading 363
The Psychology of Perception
§ 102. Pure and Mixed Perceptions 365
§ 103. Meaning 367
§ 104. The Form of Combination ........ 371
References for Further Reading 373
s
xvi Contents
ASSOCIATION
PAGB
§ 105. The Doctrine of Association 374
§ 106. The Idea ....,, 376
§ 107. The Law of Association 378
§ 108. The Experimental Study of Association ..... 380
§ 109. Results : The Conditions of Impression ..... 382
§ no. Results: The Conditions of Associative Tendency . . . 384
§ III. The Associative Consciousness 389
References for Further Reading 395
MEMORY AND IMAGINATION
§ 112. Retention: The Course of the Image 396
§ 113. Retention: The Process of Dissociation 401
§ 114. Retention: Individual Differences 403
§ 115. The Recognitive Consciousness 407
§ 116. Recognition and Direct Apprehension ..... 410
§ 117. The Memory Consciousness . . , . , . .413
§118. The Memory Image and the Image of Imagination . . . 416
§ 119. The Imaginative Consciousness 421
§ 120. Illusions of Recognition and Memory . ..... 424
References for Further Reading ..,,.,. 426
ACTION
§ 121. The Reaction Experiment ........ 428
§ 1 22. The Analysis of the Simple Reaction ...... 432
§ 123. Compound Reactions 437
§ 124. Action 447
§ 125. The Genesis of Action 450
§ 1260 The Classification of Action 458
§ 127. Will 466
References for Further Reading 469
EMOTION
§128. The Nature of Emotion 471
§ 129. The 'James-Lange Theory' of Emotion . . « . . 474
Contents
XV] 1
§ 130.
§ 131-
§ 132-
§ 133-
§ 134-
§ 135-
§ 136.
§137-
PAGE
The 'James-Lange Theory': Criticism and Modification . . 476
The Organic Reaction as Constitutive of Emotion , . .481
The Organic Reaction as Expressive of Emotion . . . 484
The Forms of Emotion ........ 4S9
Emotive Memory . ...» ... . 493
Mood, Passion and Temperament . . . . . .497
The Nature of Sentiment ........ 498
The Forms of Sentiment ........ 500
References for Further Reading ....... 503
§138.
§ 139-
§ 140.
§ 141.
§ 142.
§ 143-
§ 144-
§ 145-
§ 146.
§ 147-
§ 148.
THOUGHT
The Nature of Conscious Attitude
The Alleged Elementary Process of Thought
The Alleged Elementary Process of Relation
The Analysis of Conscious Attitude
Language ......
The Abstract Idea ....
Generalisation and Abstraction .
Comparison and Discrimination ,
Expectation, Practice, Habituation, Fatigue
Judgment ......
The Self
References for Further Reading .
505
508
512
521
525
529
532
537
540
544
547
CONCLUSION
§ 149, The Status of Psychology ........ 550
References for Further Reading ....... 552
Index of Names 553
Index of Subjects ...>....... 556
INDEX OF FIGURES
FIGURE PAGE
1. The Miiller-Lyer Illusion 7
2. The Colour Pyramid 63
3. Model of the Colour Pyramid 64
4. Deinonstrational Colour Mixer 69
5. Adaptation Frame 73
6. Wundt's After-image Apparatus ....... 75
7. Contrast Frame 76
8. Contrast of Shadows 77
9. Perimeter ...........81
10. Hering's Colour-blindness Apparatus 84
11. Tuning-fork and Bottle 93
12. The Tonal Pencil 94
13. The Series of Auditory Qualities 98
14. Weighted Wire Fork and Galton Whistle 99
15. Stern's Variator loo
16. Set of Quincke Tubes 107
17. Koenig's Difference-tone Apparatus ...... 108
18. Zwaardemaker's Olfactometer (for Solids) 121
19. Zwaardemaker's Olfactometer (for Liquids) . . . „ .122
20. Horse-hair Point for Pressure Spots 146
21. Apparatus for Localising Warm and Cold Spots (Blix) . . . 149
22. Map of Warm and Cold Spots (Blix) 150
23. Map of Pressure and Pain Spots (von Frey) ..... 153
24. Exner's Model of a Semicircular Canal 177
25. Diagram of Continuous Scale of Noise Intensity .... 209
26. Lehmann's Acoumeter ......... 213
27. Diagram of the Relation of .S" to ^ according to Weber's Law
(Wundt) 219
28. Discs for Demonstration of Weber's Law 219
xix
XX
Index of Figures
FIGURE
29. Marey Tambour with Writing Lever
30. Clockwork Kymograph .
31. Franck's Volumetric Sphygmograph
32. The Verdin Pneumograph
33. Franck's Plethysmograph
34. Automatograph
35. Mosso's Ergograph .
36. Plethysmographic Tracing
37. von Frey's Sphygmograph
38. Diagram of the Course of a Sense-feeling (Wundt)
39. Distribution of Judgments of Unpleasantness and Tension
40. Diagram of the Attentive Consciousness
41. A Puzzle Picture (R. Gudden)
42. Demonstrational Tachistoscope
43. Masson's Disc .....
44. Simple Complication Pendulum (Stevens)
45. Model of the Horopter .
46. Stereoscopic Slide .
47. Stereoscopic Slide .
48. Wheatstone's Stereoscope
49. Plan of Wheatstone's Stereoscope
50. Plan of Brewster's Stereoscope
51. Demonstrational Stereoscope .
52. Stereoscopic Slide .
53. Plan of Binocular Colour Mixer (Hering)
54. Diagram Illustrating Visual Acuity (Hering)
55. Blind Spot
56. The Miiller-Lyer Illusion: Ebbinghaus' Swallow Figure
57. Mach's Book Figure
58. Illusion of Movement (Bourdon)
59. Artificial Waterfall (James)
60. Memory Apparatus (Ranschburg)
61. Field of Telescope .
62. Hipp's Chronoscope
63. Wundt's Sound Hammer
64. Telegraph Reaction Key ,
65. Figures for Abstraction of the Lil:e (Griinbaum)
A TEXT-BOOK OF PSYCHOLOGY
A TEXT-BOOK OF PSYCHOLOGY
o>Hc
SUBJECT-MATTER, METHOD AND
PROBLEM OF PSYCHOLOGY
§ I. Science and Experience. — A science consists- of a
large body of observed facts, which are related to one
another, and are arranged under general laws. If, for
instance, you open a text-book of physics, you find that it
gives the results of numerous observations, or prescribes
experiments in which you are to observe for yourself ; and
you find that these results or experiments are grouped
under certain main headings (mechanics, heat, electricity)
and are made to illustrate certain comprehensive laws
(Newton's laws of motion, Kirchhoff's law of radiation.
Ohm's law of the strength of the electric current). All
scientific text-books, whether the science is physics or
chemistry, biology or psychology, philology or economics,
are of the same pattern.
It is worth while, before we begin our special study of
psychology, briefly to consider some of the questions
which this definition of science suggests. How, we may
ask, do the various sciences come into being ? How are
they differentiated, their several fields laid out and marked
off .'' What do we mean when we say that the facts of
any given science are related to one another.? What is
the nature of the relation } What precisely is a scientific
2 Subject-matter, Method and Problem of Psychology
law ? Why is it important for the progress of science that
laws should be established ? An answer, even a rough
answer, to these questions will help us to understand the
scope and aim of psychology.
First of all, then, it is plain that all the sciences have
the same sort of subject-matter; they all deal with some
phase or aspect of the world of human experience. If we
take a mere fragment of this world, — say, our own ex-
perience during a single day, — we find it a rather hope-
less mixture. Our lawn-sprinkler obeys the third law of
motion, while our pleasure in possessing it is a fact for
psychology ; the preparation of our food is an applied
chemistry, its adulteration depends upon economic condi-
tions, and its effect upon health is a matter of physiology ;
our manner of speech is governed by phonetic laws, while
the things we say reflect the moral standards of the time :
in a word, one science seems to run into another science
as chance may decide, without order or distinction. If,
however, we look over the world as a whole, or examine
historically any long period of human existence, the survey
is less bewildering. The world of nature breaks up at
once, as we inspect it, into living objects, the objects that
change by growth, and non-living objects, the objects that
change only by decay. And living objects divide, again,
into objects that grow in one place, the plants, and objects
that move about as they grow, the animals. Here, almost
at the first glance, we have distinguished the raw materials
of three different sciences : geology, botany, zoology. Now
let us turn to some stage of human evolution : we may
choose the social life of mankind before the dawn of civi-
lisation. Primitive man was required, by the necessities
of his case, to make himself weapons ; to hunt animals for
§ I. Science and Experience 3
food ; to protect himself by clothing and shelter, and to
avoid eating or drinking from poisonous or tainted sources.
If he ventured upon the water, he must steer his course
by the stars ; if he banded with his fellows, he must hold
to the code of honour of the tribe. He dreamed, and told
his dreams ; when he was glad, or angry, or afraid, he
showed his feeling in gesture or by the expression of his
face. Doubtless, his daily experience, if he ever thought
about it, seemed to him as chaotic as our own has just
appeared to us. But we, who have a larger vision of that
experience, can see that it contained the natural germs of
many sciences : mechanics, zoology and physiology, —
astronomy, ethics and psychology.
We are thus led to the conclusion that the world of
human experience is not altogether confused and disor-
derly. It shows lines of cleavage ; to a certain extent, it
arranges itself for us ; so that the raw materials or the
natural germs of what, in the higher forms of civilisation,
become the separate sciences force themselves separately
upon the attention. But we have not, as yet, anything
more than raw materials. Science appears only when
some man, taking the hint from nature, deliberately
follows up a special line of enquiry throughout the whole
of experience. Bridges and dwellings and weapons and
furniture and tools and utensils were made long before
there was a science of mechanics. The science begins
when men begin to interpret the universe in mechanical
terms, when the world at large is looked upon as a vast
machine, working precisely as a tool or an engine works.
Dreams, and the phenomena of trance, and the movements
which express emotion were observed long before there
was a science of psychology. The science begins when
4 Subject-matter, Method and Problem of Psychology
men begin to interpret the universe in psychological termss
when the world at large is looked upon as mind, as a body
of experience subject to psychological laws. In a word,
every science takes up a certain attitude towards the
world of human experience, or regards it from a definite
point of view, and it is the business of a science to describe
the world as it appears after the attitude has been taken
up or the point of view adopted. What differentiates the
sciences is just this difference of human interest; and
what holds a science together, and brings its observations
into relation, is just the fact that all the work has been
done under the guidance of the same principles and from
the same point of view.
We have now answered some of our general questions.
Experience, we have seen, presents itself under different
aspects. The differences are roughly outlined, but are
definite enough to serve as a starting-point. These differ-
ent aspects engage the attention of different men. Divi-
sion of labour is necessary, if the whole of experience is to
be brought within the sphere of science ; and men's inter-
ests are so various that every aspect of experience is sure,
in the long run, to find a student. As scientific investiga-
tion proceeds, and as the number of scientific men in-
creases, more and more aspects of experience are revealed,
and the sciences multiply. They do not exist independently,
side by side, as accounts of separate portions of the world
or of separate regions of experience ; they overlap and
coincide, describing one and the same world of experience
as it appears from their special standpoints. They are not
like blocks of knowledge, which when cut to the proper
size and properly fitted together will give us a map of the
universe ; they are rather like the successive chapters of a
§ I. Science and Experience 5
book which discusses a large topic from every possible
point of view. Some chapters are long, and some are
short ; some are general, and some are special : this de-
pends upon the sort of attitude which a given science
takes towards experience. But all the chapters, or sciences,
deal with the same world under its various aspects. —
We have still to enquire what science means by a law,
and why it is that the advance of science depends upon the
establishment of laws. The answer is simple. The longer
scientific observations are continued, and the more scien-
tific methods are refined, the clearer does it become that ex-
perience is regular and orderly. If only the conditions of
an occurrence remain the same, the occurrence will always
take place in the same way. A scientific law thus expresses
a regularity, an unbroken uniformity, of some aspect of ex-
perience. Go to a dictionary, and look up Charles' law, and
Grimm's law, and Weber's law : you will find that in all
three cases — physics, philology, psychology — the laws
are of this sort.
The formulation of a scientific law, therefore, means the
final writing of some paragraph in some chapter of that
book of the world which contains all the different sciences.
No science is as yet complete : but the formulation of a law
means that the science of which it holds is complete up to
a certain point. The law embraces, covers, summarises a
large body of observations, and also serves as a point of
departure for the making of fresh observations. This is
why the important dates in the history of science are the
years in which scientific laws were established, and why the
most honoured names in science are the names of the men
who established them. It would, perhaps, make the study
of science easier for the beginner if all proper names were
6 Subject-matter, Method and Problem of Psychology
omitted, and we ceased to speak of the principle of Archi-
medes, and Euchdean geometry, and Newton's laws of
motion. But these terms serve a good purpose : they show
the importance of scientific laws, and they also reinforce a
conclusion at which we have already arrived, — that what
differentiates the sciences is the difference of human inter-
ests, and that what makes a science is some man's consistent
adherence to a definite point of view.
§ 2. The Subject-matter of Psychology. — If it is true
that all the sciences have the same sort of subject-matter,
there can be no essential difference between the raw mate-
rials of physics and the raw materials of psychology.
Matter and mind, as we call them, must be fundamen-
tally the same thing. Let us find out, now, whether this
statement is really as paradoxical as at first thought it
appears.
All human knowledge is derived from human experi-
ence ; there is no other source of knowledge. But human
experience, as we have seen, may be considered from
different points of view. Suppose that we take two points
of view, as far as possible apart, and discover for ourselves
what experience looks like in the two cases. First, we
will regard experience as altogether independent of any
particular person ; we will assume that it goes on whether
or not anyone is there to have it. Secondly, we will re-
gard experience as altogether dependent upon the partic-
ular person ; we will assume that it goes on only when
someone is there to have it. We shall hardly find stand-
points more diverse. What are the differences in experi-
ence, as viewed from them }
Take, to begin with, the three things that you first learn
§ 2. The Subject-matter of PsycJiology 7
about in physics : space, time and mass. Physical space,
which is the space of geometry and astronomy and geol-
ogy, is constant, always and everywhere the same. Its
unit is I cm., and the cm. has precisely the same value
wherever and whenever it is applied. Physical time is
similarly constant ; and its constant unit is the i sec.
Physical mass is constant ; its unit, the i gr., is
always and everywhere the same. Here we
have experience of space, time and mass con-
sidered as independent of the person who ex-
periences them. Change, then, to the point of
view which brings the experiencing person into
account. The two vertical lines in Fig. i are
physically equal; they measure alike in units of
I cm. To you, who see them, they are not
equal. The hour that you spend in the wait-
ing-room of a village station and the hour that
you spend in watching an amusing play are
physically equal ; they measure alike in units of
I sec. To you, the one hour goes slowly, the
other quickly ; they are not equal. Take two
circular cardboard boxes of different diameter
(say, 2 cm. and 8 cm.), and pour sand into them
until they both weigh, say, 50 gr. The two y\g. i
masses are physically equal ; placed on the
pans of a balance, they will hold the beam level. To
you, as you lift them in your two hands, or raise them
in turn by the same hand, the box of smaller diameter is
considerably the heavier. Here we have experience of
space, time and mass considered as dependent upon the
experiencing person. It is the same experience that we
were discussing just now. But our first point of view
8 Subject-matter, Method and Problem of Psychology
gives us facts and laws of physics ; our second gives us
facts and laws of psychology.
Now take three other topics that are discussed in the
physical text-books : heat, sound and light. Heat proper,
the physicists tell us, is the energy of molecular motion ;
that is to say, heat is a form of energy due to a movement
of the particles of a body among themselves. Radiant
heat belongs, with light, to what is called radiant energy,
— energy that is propagated by wave-movements of the
luminiferous ether with which space is filled. Sound is a
form of energy due to the vibratory movements of bodies,
and is propagated by wave-movements of some elastic
medium, solid, liquid or gaseous. In brief, heat is a dance
of molecules ; light is a wave-motion of the ether ; sound
is a wave-motion of the air. The world of physics, in
which these types of experience are considered as inde-
pendent of the experiencing person, is neither warm nor
cold, neither dark nor light, neither silent nor noisy. It is
only when the experiences are considered as dependent
upon some person that we have warmth and cold, blacks
and whites and colours and greys, tones and hisses
and thuds. And these things are subject-matter of psy-
chology.
We find, then, a great difference in the aspect of experi-
ence, according as it is viewed from the one or the other
of our different standpoints. It is the same experience all
through ; physics and psychology deal with the same stuff,
the same material; the sciences are separated simply —
and sufificiently — by their point of view. From the stand-
point of physics, we get such sciences as physics (in the
narrower sense), chemistry, geology, astronomy, meteo-
rology. From the standpoint of psychology we get, in the
§ 3- The Common-sense View of Mmd 9
same way, a special group of sciences : their names and
provinces are given in § 7.
It must be clearly understood that we are not here attempting
to give a strict definition of the subject-matter of psychology.
We assume that everybody knows, at first hand, what human
experience is, and we then seek to mark off the two aspects of
this experience which are dealt with respectively by physics
and psychology. Any further definition of the subject-matter of
psychology is impossible. Unless one knows, by experience itself,
what experience is, one can no more give a meaning to the term
' mind ' than a stone can give a meaning to the term * matter.'
§ 3. The Common-sense View of Mind. — If, before you
read the two preceding sections, you had been asked to
define psychology, you would probably have said, without
hesitation, that it is the science of mind. But you would
have meant by mind something that, at all events in
appearance, is very different from the meaning that these
two sections have given it. Let us see how nearly we can
reconcile the common-sense idea of mind with the view
that it is the sum-total of human experience considered as
dependent upon the experiencing person.
The common-sense idea of the world is roughly this.
The world is made up of, or contains, two radically differ-
ent things : matter and mind. Matter is found in the
physical objects around us; it always fills space; it is gov-
erned by mechanical laws, laws of cause and effect. Mind
is found in ourselves and, very likely, in some of the other
animals ; it is immaterial, not spatial ; it is not bound by
mechanical laws, but is free to act as it will ; if it submits
to laws at all (as, for instance, to the laws of thought in
our processes of reasoning), these are laws peculiar to it,
and are not the same as the laws of nature. Nevertheless,
lO Subject-matter, MetJiod and Problevi of Psychology
different as mind and matter are, they are joined together,
in a very intimate way, both in ourselves and in such of
the animals as possess minds; for our physical bodies are
material. And when they are thus joined together, they
act upon each other, mind affecting matter and matter
affecting mind. We cry because we are grieved ; we can-
not think clearly because we have eaten too heavy a dinner.
Compare these statements, now, with the statements of
§§ I and 2. Common sense declares that mind and matter
are radically different. We have said that, in order to get
the subject-matter of physics and of psychology, one must
regard human experience from standpoints as diverse as
can be found. So far there is a general agreement. Com-
mon sense declares that the laws of matter are different
from the laws of mind. We have seen that, for instance,
space, time and mass behave very differently, according as
they are taken to be independent of, or dependent upon,
the experiencing person. Again there is agreement. Com-
mon sense declares that we, and perhaps the animals, are
made up both of matter and of mind. Here also, if we go
beneath the difference of terms, there is agreement. The
living body, as it is treated in the science of physiology, is
treated from the physical point of view ; it belongs to the
independent aspect of experience. The same living body
— that is to say, an organism, an organised individual —
is, however, precisely the 'experiencing person' referred to
in our definition of mind. It is when heat-waves strike the
skin, and sound-waves strike the ear, and light-waves strike
the eye, that we have experience in its dependent aspect,
as warmth and tone and colour. On these three points,
therefore, we have no serious quarrel with common sense.
On the other hand, common sense makes certain other
§ 3- The Common-sense Viezv of Mind 1 1
statements that we cannot accept. These statements all
point to a view of mind which is not often expressed out-
right, in so many words, but which is very generally held :
the view, namely, that mind is a living being, with all the
qualities and powers that are possessed by material living
beings; an immaterial animal, so to say, that dwells within
the material animal; an inward man, manifesting itself in
the behaviour of the outward man. A mind so conceived
cannot fill space, because it is not material ; but it has all
the other properties of a living creature. It is free to act
as it pleases, just as you are free to come or to go, to do
this or to do that. It can influence the body, and be
influenced by the body, just as you may influence or be
influenced by your friend. This view of mind probably
appears natural enough, although, as soon as you begin to
ask questions, you will find that it is by no means clear.
Natural or not, however, it is a view which we must here
reject, for the following reasons.
(i) A statement that rests upon common sense is not
likely to be argued ; it is taken for granted, as something
that needs no discussion. Yet, in theoretical matters,
common sense is an unsafe guide. For the common
sense of our own generation simply sums up so much of
the advanced thought of former generations as the great
body of mankind has found acceptable and intelligible.
A brilliant speculation of one age may become the com-
mon sense of the next: but this does not make it any the
less speculation, while in the course of becoming common
sense its logical structure has, inevitably, been more or
less damaged. Common sense, in theoretical matters, is
past philosophy ; and the philosophy is the more vulgar
ised, the farther it has travelled from its source.
12 Subject-matter, Method and Problem of Psychology
There is no dispute as to the philosophical source from
which, in the present instance, our common-sense ideas
are derived. The view of mind and matter which we are
now criticising was set forth, in all essential points, by
the French philosopher, Rene Descartes (i 596-1650). Np
doubt, the common-sense version has certain crude ele
ments which are indefinitely older than Descartes; no
doubt, also, it has been tinged by later thought, notably
by the doctrine of organic evolution. In the main, how-
ever, what is common sense to-day was high Cartesian
philosophy two centuries and a half ago.^
Plainly, then, we cannot take common sense for granted.
As we should not nowadays pin our philosophical faith
to Descartes, so we cannot leave Cartesian doctrines un-
questioned when they appear in the garb of common
sense. We shall rather expect to find that Descartes, and
with him our own common sense, are partly right and
partly wrong.
(2) That some of the doctrines of common sense agree,
in general, with the position of §§ i and 2 has already
been shown. The remainder must be rejected, because
the evidence is against them. We are told that mind is
not spatial : yet, as Fig. i shows, mental experience takes
on the spatial form as readily as physical experience.
We are told that mind is free to act as it pleases : yet, as
we shall see in this book, the more carefully mind is stud-
ied, the more plainly are the laws of mental experience
revealed. We are told that mind influences body, and
' You will find that this statement is borne out by the histories of philoso-
phy. Turn, for instance, to A. K. Rogers, A Student'' s History of Philosophy,
1901, pp. 269-289, especially 2S4-287. The passage is not easy reading;
but you will understapd it well enough to see that what is said in the text is
historically corrtcl.
§ 4- Psychophysical Parallelism 13
body mind. How an immaterial thing can influence and
be influenced by a material thing we are not told, — for
the very good reason that nobody knows : though, if this
were the only view that did justice to the facts, we should
nevertheless be bound to accept it. Since, as the follow-
ing section shows, all the observed facts can be rationally
explained from the standpoint of §§ i and 2, this stand-
point must be preferred.
§ 4. Psychophysical Parallelism. — Common sense says
that we cry because we are sorry, laugh because we are
amused, run because we are frightened; that we feel
gloomy and morose because we do not digest our food,
go insane from softening of the brain, lose consciousness
because we have inhaled ether. Mind influences body,
and body influences mind. Our own position has been
that mind and body, the subject-matter of psychology and
the subject-matter of physiology, are simply two aspects
of the same world of experience. They cannot influence
each other, because they are not separate and independent
things. For the same reason, however, wherever the two
aspects appear, any change that occurs in the one will
be accompanied by a corresponding change in the other.
Your view of a town from the east cannot influence your
view of the same town from the west ; but as your view
from the east differs in sunhght and moonlight, so corre-
spondingly will your view from the west differ. This
doctrine of the relation of mind to body is known as
the doctrine of psychophysical parallelism : the common-
sense doctrine is that of interaction.
From the point of view of psychophysical parallehsm,
then, it is not strictly true to say that we cry because we
14 Subject-matter, Method and Problem of Psychology
are sorry. If we look at the whole experience under its
independent aspect, we find that certain physical eventSi
certain stimuli, affect the body ; they set up in the body,
and especially in the nervous system, certain physical
changes; these changes cause the secretion of tears. This
is an exhaustive account of the experience, considered as
independent of the experiencing person. If we look at
the experience under its dependent aspect, we find that our
consciousness has been invaded by grief or remorse or
some kindred emotion. The two sets of events, physical
and mental, are parallel, but they do not interfere with
each other. And the same thing holds of all the other
cases cited at the beginning of this section.
By accepting this doctrine of parallelism we gain a two-
fold advantage. On the positive side, we are able to do
justice to all the observed facts ; we never come into con-
tradiction with facts. On the negative side, we avoid per-
plexing questions, questions that lead nowhere because
they are put from a wrong standpoint. The common-
sense view of mind appears natural ; but as soon as
you ask questions, you find it obscure. Where, for in-
stance, on that view, does the body end and the mind
begin ? Do the senses belong to mind or to body .-' Is
the mind always active and the body always passive .'' Do
body and mind ever act independently of each other 1 Ques-
tions such as these arise at once ; but it is a hard matter to
answer them. Parallehsm has no logical pitfalls of this
kind.
At the same time, we need not be pedantic, and change
our manner of speech to accord with the strict letter of
parallelism. The astronomer does not scruple to talk, with
all the rest of us, about sunrise and sunset. It is not strictly
§ 5- Mental Process, Conscioiisness and Mind 15
true to say that we cry because we are sorry ; our crying
is the effect of certain nervous (that is, physical) changes,
whose parallel on the mental side is the emotion of grief.
But this parallel is constant and invariable. We should
not cry, under the circumstances, unless we were sorry,
because our sorrow is the mental aspect of those nervous
changes that make us cry : we have only to shift our point of
view, and what appeared as nervous change appears as
emotion. So that, for all practical purposes, it is true to
say that we cry because we are sorry, and run because we
are frightened, and so forth. What we have to guard
against is not the phrasing of these statements, but their
popular interpretation. To suppose that the sorrow and
the fear are literally the cause of tears and bodily move-
ments would be on a par with supposing that the idea of
watering the lawn can, literally and directly, turn the tap
and set the sprinkler in motion.
§ 5 . Mental Process, Consciousness and Mind. — The most
striking fact about the world of human experience is the
fact of change. Nothing stands still ; everything goes on.
The sun will someday lose its heat ; the eternal hills are,
little by little, breaking up and wearing away. Whatever
we observe, and from whatever standpoint we observe it,
we find process, occurrence ; nowhere is there permanence
or stability. Mankind, it is true, has sought to arrest this
flux, and to give stability to the world of experience, by
assuming two permanent substances, matter and mind :
the occurrences of the physical world are then supposed
to be manifestations of matter, and the occurrences of the
mental world to be manifestations of mind. Such an
hypothesis may be of value at a certain stage of human
1 6 Subject-matter, Method and Problem of Psychology
thought ; but every hypothesis that does not accord with
the facts must, sooner or later, be given up. Physicists
are therefore giving up the hypothesis of an unchanging,
substantial matter, and psychologists are giving up the
hypothesis of an unchanging, substantial mind. Stable
objects and substantial things belong, not to the world of
science, physical or psychological, but only to the world of
common sense.
We have defined mind as the sum-total of human experi-
ence considered as dependent upon the experiencing person.
We have said, further, that the phrase * experiencing per-
son ' means the living body, the organised individual ; and
we have hinted that, for psychological purposes, the living
body may be reduced to the nervous system and its attach-
ments. Mind thus becomes the sum-total of human experi-
ence considered as dependent upon a nervous system. And
since human experience is always process, occurrence, and
the dependent aspect of human experience is its mental
aspect, we may say, more shortly, that mind is the sum-
total of mental processes. All these words are significant.
' Sum-total ' implies that we are concerned with the whole
world of experience, not with a limited portion of it ; ' men-
tal ' implies that we are concerned with experience under
its dependent aspect, as conditioned by a nervous system ;
and ' processes ' implies that our subject-matter is a stream,
a perpetual flux, and not a collection of unchanging objects.
It is not easy, even with the best will possible, to shift from
the common-sense to the scientific view of mind ; the change can-
not be made all in a moment. We are to regard mind as a stream
of processes? But mind is personal, my mind; and my person-
ality continues throughout my life. The experiencing person is
only the bodily organism ? But, again, experience is personal, the
§ 5^ Mental Process, Consciousness and Mind \y
experience of a permanent self. Mind is spatial, just as matter is?
But mind is invisible, intangible ; it is not here or there, square or
round.
These objections cannot be finally met until we have gone some
distance into psychology, and can see how the scientific view of
mind works out. Even now, however, they will weaken as you
look at them. Face that question of personality. Is your Ufe, as
a matter of fact, always personal? Do you not, time and again,
forget yourself, lose yourself, disregard yourself, neglect yourself,
contradict yourself, in a very literal sense? Surely, the mental life
is only intermittently personal. And is your personality, when it
is realised, unchanging? Are you the same self in childhood and
manhood, in your working and in your playing moods, when you
are on your best behaviour and when you are freed from restraint ?
Surely, the self- experience is not only intermittent, but also com-
posed, at different times, of very different factors. As to the other
question : mind is, of course, invisible, because sight is mind ; and
mind is intangible, because touch is mind. Sight-experience and
touch-experience are dependent upon the experiencing person.
But common sense itself bears witness, against its own beHef, to
the fact that mind is spatial : we speak, and speak correctly, of an
idea in our head, a pain in our foot. And if the idea is the idea
of a circle seen in the mind's eye, it is round; and if it is the
visual idea of a square, it is square.
Consciousness, as reference to any dictionary will show,
is a term that has many meanings. Here it is, perhaps,
enough to distinguish two principal uses of the word.
In its first sense, consciousness means the mind's
awareness of its own processes. Just as, from the common-
sense point of view, mind is that inner self which thinks,
remembers, chooses, reasons, directs the movements of
the body, so is conciousness the inner knowledge of
this thought and government. You are conscious of the
correctness of your answer to an examination question, of
c
1 8 Subject-matter, Method and Problem of Psychology
the awkwardness of your movements, of the purity of youi
motives. Consciousness is thus something more than
mind ; it is " the perception of what passes in a man's own
mind " ; ^ it is " the immediate knowledge which the mind
has of its sensations and thoughts." 2
In its second sense, consciousness is identified with
mind, and 'conscious' with 'mental.' So long as mental
processes are going on, consciousness is present ; as soon
as mental processes are in abeyance, unconsciousness sets
in. " To say I am conscious of a feeling, is merely to say
that I feel it. To have a feeling is to be conscious ; and
to be conscious is to have a feeling. To be conscious of
the prick of the pin, is merely to have the sensation. And
though I have these various modes of naming my sensa-
tion, by saying, I feel the prick of a pin, I feel the pain of
a prick, I have the sensation of a prick, I have the feeling
of a prick, I am conscious of the feeling ; the thing named
in all these various ways is one and the same." 3
The first of these definitions we must reject. It is not
only unnecessary, but it is also misleading, to speak of
consciousness as the mind's awareness of itself. The
usage is unnecessary, because, as we shall see later, this
awareness is a matter of observation of the same general
kind as observation of the external world; it is mislead-
ing, because it suggests that mind is a personal being,
instead of a stream of processes. We shall therefore
1 John Y.o^^, An Essay Concerning Human Understanding, [1690] Bk.
II., Ch. i., § 19.
2 Dugald Stewart, Outlines of Moral Philosophy, [1793] Pt. I., Section i.,
§7-
3 James Mill, Analysis of the Phenomena of the Human Mind, [1S29]
Vol. I., Ch. V. Mill uses the word 'feeling' to denote what we have called
' mental process.'
§ 6. The Method of Psychology 19
take mind and consciousness to mean the same thing.
But as we have the two different words, and it is convenient
to make some distinction between them, we shall speak
of mind when we mean the sum-total of mental processes
occurring in the life -time of an individual, and we shall
speak of consciousness when we mean the sum-total of
mental processes occurring now, at any given ' present '
time. Consciousness will thus be a section, a division, of
the mind-stream. This distinction is, indeed, already
made in common speech : when we say that a man has
' lost consciousness,' we mean that the lapse is temporary,
that the mental life will shortly be resumed ; when we say
that a man has ' lost his mind,' we mean — not, it is true, that
mind has altogether disappeared, but certainly that the
derangement is permanent and chronic.
While, therefore, the subject-matter of psychology is
mind, the direct object of psychological study is always
a consciousness. In strictness, we can never observe the
same consciousness twice over ; the stream of mind flows
on, never to return. Practically, we can observe a par-
ticular consciousness as often as we wish, since mental
processes group themselves in the same way, show the
same pattern of arrangement, whenever the organism is
placed under the same circumstances. Yesterday's high
tide will never recur, and yesterday's consciousnesses will
never recur ; but we have a science of psychology, as we
have a science of oceanography.
§ 6. The Method of Psychology. — Scientific method
may be summed up in the single word ' observation ' ; the
only way to work in science is to observe those phenomena
which form the subject-matter of science. And observa-
20 Subject-matter, Method and Problem of Psychology
tion implies two things : attention to the phenomena, and
record of the phenomena ; that is, clear and vivid experi-
ence, and an account of the experience in words or
formulas.
In order to secure clear experience and accurate report,
science has recourse to experiment. An experiment is an
observation that can be repeated, isolated and varied. The
more frequently you can repeat an observation, the more
likely are you to see clearly what is there and to describe
accurately what you have seen. The more strictly you
can isolate an observation, the easier does your task of
observation become, and the less danger is there of your
being led astray by irrelevant circumstances, or of placing
emphasis on the wrong point. The more widely you can
vary an observation, the more clearly will the uniformity
of experience stand out, and the better is your chance of
discovering laws. All experimental appliances, all labora-
tories and instruments, are provided and devised with this
one end in view : that the student shall be able to repeat,
isolate and vary his observations. —
The method of psychology, then, is observation. To
distinguish it from the observation of physical science,
which is inspection, a looking-at, psychological observation
has been termed introspection, a looking-within. But this
difference of name must not blind us to the essential like^
ness of the methods. Let us take some typical instances.
We may begin with two very simple cases, (i) Suppose
that you are shown two paper discs : the one of an uniform
violet, the other composed half of red and half of blue.
If this second disc is rapidly rotated, the red and blue will
mix, as we say, and you will see a certain blue-red, that is,
a kind of violet. Your problem is, so to adjust the pro-
§ 6. The Method of Psychology 21
portions of red and blue in the second disc that the result-
ing violet exactly matches the violet of the first disc. You
may repeat this set of observations as often as you like;
you may isolate the observations by working in a room
that is free from other, possibly disturbing colours ; you
may vary the observations by working to equality of the
violets first from a two-colour disc that is distinctly too
blue, and secondly from a disc that is distinctly too red.
(2) Suppose, again, that the chord c-e-g- is struck, and
that you are asked to say how many tones it contains.
You may repeat this observation; you may isolate it, by
working in a quiet room ; you may vary it, by having the
chord struck at different parts of the scale, in different
octaves.
It is clear that, in these instances, there is practically no
difference between introspection and inspection. You are
using the same method that you would use for counting
the swings of a pendulum, or taking readings from a gal-
vanometer scale, in the physical laboratory. There is a
difference in subject-matter: the colours and the tones are
dependent, not independent experiences : but the method
is essentially the same.
Now let us take some cases in which the material of in-
trospection is more complex, (i) Suppose that a word is
called out to you, and that you are asked to observe the
effect which this stimulus produces upon consciousness :
how the word affects you, what ideas it calls up, and so
forth. The observation may be repeated ; it may be
isolated, — you may be seated in a dark and silent room,
free from disturbances ; and it may be varied, — different
words may be called out, the word may be flashed upon a
screen instead of spoken, etc. Here, however, there seems
22 Subject-matter y Method and Problem of Psychology
10 be a difference between introspection and inspection.
'The observer who is watching the course of a chemical
reaction, or the movements of some microscopical creature,
can jot down from moment to moment the different phases
of the observed phenomenon. But if you try to report the
changes in consciousness, while these changes are in
progress, you interfere with consciousness ; your transla-
tion of the mental experience into words introduces new
factors into that experience itself. (2) Suppose, again,
that you are observing a feeling or an emotion : a feeling
of disappointment or annoyance, an emotion of anger or
chagrin. Experimental control is still possible ; situations
may be arranged, in the psychological laboratory, such
that these feelings may be repeated, isolated and varied.
But your observation of them interferes, even more
seriously than before, with the course of consciousness.
Cool consideration of an emotion is fatal to its very exist-
ence ; your anger disappears, your disappointment evapo
rates, as you examine it.
To overcome this difificulty of the introspective method,
students of psychology are usually recommended to delay
their observation until the process to be described has run
its course, and then to call it back and describe it from
memory. Introspection thus becomes retrospection ; in-
trospective examination becomes post mortem examination.
The rule is, no doubt, a good one for the beginner ; and
there are cases in which even the experienced psychologist
will be wise to follow it. But it is by no means universal.
For we must remember {a) that the observations in ques-
tion may be repeated. There is, then, no reason why the
observer to whom the word is called out, or in whom the
emotion is set up, should not report at once upon the first
§ 6. The Method of Psychology 23
stage of his experience : upon the immediate effect of
the word, upon the beginnings of the emotive process.^
It is true that this report interrupts the observation.
But, after the first stage has been accurately described,
further observations may be taken, and the second,
third and following stages similarly described ; so that
presently a complete report upon the whole experience
is obtained. There is, in theory, some danger that the
stages become artificially separated ; consciousness is a
flow, a process, and if we divide it up we run the risk
of missing certain intermediate links. In practice, how-
ever, this danger has proved to be very small ; and we
may always have recourse to retrospection, and compare
our partial results with our memory of the unbroken expe-
rience. Moreover, {b) the practised observer gets into an
introspective habit, has the introspective attitude ingrained
in his system ; so that it is possible for him, not only to take
mental notes while the observation is in progress, without
interfering with consciousness, but even to jot down
written notes, as the histologist does while his eye is still
held to the ocular of the microscope.
In principle, then, introspection is very like inspection.
The objects of observation are different; they are objects
of dependent, not of independent experience ; they are
likely to be transient, elusive, slippery. Sometimes they
refuse to be observed while they are in passage; they
must be preserved in memory, as a delicate tissue is pre-
1 We discuss in § 69, where we are dealing with the elementary processes
in emotion, the special difficulty mentioned above : that, if you concentrate
your attention, say, upon your anger, the anger disappears. This difficulty
makes it necessary to lay down special rules for the observation of emotion.
But it does not make it necessary — and that is the point here — to observe
emotion retrospectively.
24 Subject-matter, Method and Problem of Psychology
served in hardening fluid, before they can be examined.
And the standpoint of the observer is different ; it is the
standpoint of human Hfe and of human interest, not of
detachment and aloofness. But, in general, the method
of psychology is much the same as the method of physics.
It must not be forgotten that, while the method of the physical
and the psychological sciences is substantially the same, the
subject-matter of these sciences is as different as it can well be.
Ultimately, as we have seen, the subject-matter of all the sciences
is the world of human experience ; but we have also seen that the
aspect of experience treated by physics is radically different from
the aspect treated by psychology. The likeness of method may
tempt us to slip from the one aspect to the other, as when a text-
book of physics contains a chapter on vision and the sense of
colour, or a text-book of physiology contains paragraphs on delu-
sions of judgment ; but t'nis confusion of subject-matter must
inevitably lead to confusion of thought. Since all the sciences
are concerned with the one world of human experience, it is
natural that scientific method, to whatever aspect of experience
it is applied, should be in principle the same. On the other hand,
when we have decided to examine some particular aspect of ex-
perience, it is necessary that we hold fast to that aspect, and do
not shift our point of view as the enquiry proceeds. Hence it is
a great advantage that we have the two terms, introspection and
inspection, to denote observation taken from the different stand-
points of psychology and of physics. The use of the word intro-
spection is a constant reminder that we are working in psychology,
that we are observing the dependent aspect of the world of expe-
rience.
Observation, as we said above, implies two things : attention
to the phenomena, and record of the phenomena. The attention
must be held at the highest possible degree of concentration ; the
record must be photographically accurate. Observation is, there-
fore, both difficult and fatiguing; and introspection is. on the
whole, more difficult and more fatiguing than inspection. To
§ 7- T^^''^ Scope of PsycJiology 25
secure reliable results, we must be strictly impartial and unpreju-
diced, facing the facts as they come, ready to accept them as they
are, not trying to fit them to any preconceived theory ; and we
must work only when our general disposition is favourable, when
we are fresh and in good health, at ease in our surroundings, free
from outside worry and anxiety. If these rules are not followed;
no amount of experimenting will help us. The observer in the
psychological laboratory is placed under the best possible external
conditions; the room in which he works is fitted up and arranged
in such a way that the observation may be repeated, that the
process to be observed may stand out clearly upon the back-
ground of consciousness, and that the factors in the process may
be separately varied. But all this care is of no avail, unless the
observer himself comes to the work in an even frame of mind,
gives it his full attention, and is able adequately to translate his
experience into words.
§ 7. The Scope of Psychology. — If mind is the sum-
total of human experience considered as dependent upon
the experiencing person, it follows that each one of us
can have direct acquaintance only with a single mind,
namely, with his own. We are concerned in psychology
with the whole world of human experience ; but we are
concerned with it solely under its dependent aspect, as
conditioned by a nervous system ; and a nervous system
is a particular thing, possessed by a particular individual.
In strictness, therefore, it is only his own mind, the expe-
rience dependent upon his own nervous system, that each
of us knows at first-hand ; it is only to this limited and in-
dividual subject-matter that the method of experimental
introspection can be directly applied. How, then, is a
scientific psychology possible ? How can psychology be
anything more than a body of personal beliefs and indi-
vidual opinions }
26 Subject-matter, Method and Problem of P sychology
The difficulty is more apparent than real. We have
every reason to believe, not only in general that our neigh-
bours have minds like our own, that is, are able like our-
selves to view experience in its dependent aspect, but
also in detail that human minds resemble one another
precisely as human bodies do. Within a given race there
is much apparent diversity of outward form : differences in
height and figure, in colour of hair and eyes, in shape of
nose and mouth. We notice these differences, because
we are obliged in everyday life to distinguish the persons
with whom we come in contact. But the resemblances
are more fundamental than the differences. If we have
recourse to exact measurements, we find that there is in
every case a certain standard or type to which the indi-
vidual more or less closely conforms and about which all
the individuals are more or less closely grouped. And
even without measurement we have evidence to the same
effect: strangers see family likenesses which the mem-
bers of the family cannot themselves detect, and the units
in a crowd of aliens, Chinese or Negroes, look bewilder-
ingly alike.
Now all of our main social institutions rest upon the as-
sumption that the individuals of whom society is com-
posed possess minds, and possess minds that are of the
same sort. Language, religion, law and custom, — they
one and all rest upon this assumption, and they one and
all bear testimony that the assumption is well grounded.
Would a man invent language in order to talk to himself?
Language implies that there are more minds than one.
And would the use of a common speech be possible if
minds were not essentially alike } Men differ in their
command of language, as they differ in complexion, or in
§ /. The Scope of Psychology 27
liability to disease; but the general use of language testifies
to a fundamental likeness of mental constitution in us all.
Hence the psychologist is fully justified in believing
that other men have minds of the same kind as his own,
and in basing psychology upon the introspective reports
furnished by a number of different observers. These
reports show, in point of fact, just what we should expect
them to show : a fundamental agreement, and a great
variety of detail, — the mental differences grouping them-
selves, as we have seen that physical differences group
themselves, about a central type or standard.
If, however, we attribute minds to other human beings,
we have no right to deny them to the higher animals.
These animals are provided with a nervous system of the
same pattern as ours, and their conduct or behaviour,
under circumstances that would arouse certain feelings in
us, often seems to express, quite definitely, similar feelings
in them. Surely we must grant that the highest verte-
brates, mammals and birds, have minds. But the lower
vertebrates, fishes and reptiles and amphibia, possess a
nervous system of the same order, although of simpler
construction. And many of the invertebrates, insects
and spiders and crustaceans, show a fairly high degree
of nervous development. Indeed, it is difficult to limit
mind to the animals that possess even a rudimentary ner-
vous system ; for the creatures that rank still lower in the
scale of life manage to do, without a nervous system,
practically everything that their superiors do by its assist-
ance. The range of mind thus appears to be as wide as
the range of animal life.
The plants, on the other hand, appear to be mindless. Many
of them are endowed with what we may term sense-organs, that is,
28 Subject-matter, Method and Problem of Psychology
organs differentiated to receive certain forms of stimulus, pressure,
impact, light, etc. Ttiese organs are analogous in structure to the
sense-organs of the lower animal organisms : thus, plant ' eyes '
have been found, which closely resemble rudimentary animal eyes,
and which — if they belonged to animals — might mediate the
perception of light : so that the development of the plant-world
has evidently been governed by the same general laws of adapta-
tion to environment that have been at work in the animal king-
dom. But we have no evidence of a plant-consciousness.
Just as the scope of psychology extends beyond man to
the animals, so does it extend from the individual man to
groups of men, to societies. The subject-matter of psy-
chology is human experience considered as dependent
upon the individual. But since the individuals of the
same race and epoch are organised in much the same
way, and since they live together in a society where their
conduct affects and is affected by the conduct of others,
their view of experience under its dependent aspect natu-
rally becomes, in certain main features, a common or
general view; and this common view is embodied in those
social institutions to which we have referred above, — in
language, religion, law and custom. There is no such
thing as a collective mind, or a national mind, or a social
mind, if we mean by mind some immaterial being ; but
there is a collective mind, if we mean by it the sum-total
of human experience considered as dependent upon a
social group of similar individuals. The study of the
collective mind gives us a psychology of language, a
psychology of myth, a psychology of custom, etc. ; it also
gives us a differential psychology of the Latin mind, of the
Anglo-Saxon mind, of the Oriental mind, etc.
And this is not all : the scope of psychology extends.
§ /• The Scope of Psychology 29
still further, from the normal to the abnormal mind. Life,
as we know, need not be either complete or completely-
healthy life. The living organism may show defect, the
lack of a limb or of a sense-organ ; and it may show dis-
order and disease, a temporary or a permanent lapse from
health. So it is with mind. The consciousnesses of those
who are born deaf or blind are defective; they lack certain
sensations and images that are normally present. In
dreaming and the hypnotic state, during intoxication, after
prolonged sleeplessness or severe strain of any kind, we
have illustrations of temporary mental derangement. And
the various forms of insanity — mania, melancholia, demen-
tia — -are forms of permanent mental disorder.
Derangement of the social mind may be studied in the
various panics, fads, epidemics of speculation, of false
belief, etc., which occur from time to time even in the
most highly civihsed societies. The mob consciousness
stands to a healthy social consciousness very much as
dreaming to the waking life. Permanent disorder of the
social mind means the downfall of society.
All these various fields of psychology may be cultivated for their
own sake, on account of their intrinsic interest and value ; they
must, indeed, be so cultivated, if psychology is to progress. At
the same time, their facts and laws often throw light upon the
problems of normal human psychology. Suppose, for instance,
that a man, blind from his birth, is rendered able to see by a
surgical operation. He must learn to use his eyes, as a child
learns to walk. And the gradual perfecting of his vision, the
mistakes and confusions to which he is liable, all the details of
his visual education, form a storehouse of facts upon which the
psychologist can draw when he seeks to illustrate the development
of the perception of space in the normal mind, — the manner in
which we come to judge of the distance of objects from ourselves
30 Subject-matter, Method and Problem of P sychology
and from one another, of their direction, and of their size and
shape. Instructive, also, are those forms of mental unsoundness
which consist in the derangement of a single group of processes.
The various types of morbid fear — agoraphobia, the fear of being
alone in open spaces ; neophobia, the fear of everything that is
new ; phobophobia, the nervous dread of being afraid — are only
exaggerated forms of experiences that most of us have had. The
sanest man will feel lost when he passes, suddenly, from a quiet
country life to the bustle of a large town ; we are all a little timid
when we enter a strange community ; we have all been afraid that
on such-and-such an occasion we shall show our nervousness.
Similarly, the self-importance of paranoia is merely an exaggeration
of the pleased self-consciousness, the self-complacency, that we
often observe in others and, if we are honest, must often detect
in ourselves. In all these instances, the strong lines of the
caricature may help us to a more correct picture of the normal
consciousness.
§ 8. The Use of Analogy in Psychology. — We have agreed
that the psychologist is not confined to a knowledge of
his own mind. Although this is the only mind to which
he can directly apply the method of experimental intro-
spection, he can apply the method indirectly to any num-
ber of minds. Psychology is based upon the introspections
of a large number of trained observers.
But we have gone much farther than this. We have
spoken of an animal psychology, a social psychology, and
a psychology of the abnormal mind. What, then, is the
method to be employed in these branches of psychology .-'
We cannot ask the animal or the society or the madman
to introspect !
Yet, in a sense, this is just what we do. Observation,
it will be remembered, implies two things : attention to
the phenomena, and record of the phenomena. W^e
§ 8. The Use of Analogy in Psychology 31
ourselves record mental phenomena, for psychological
purposes, in language. This form of record has great
advantages : it is flexible, since we have a large vocabu-
lary at our disposal ; it is constant, since written or
printed reports may be preserved for a long time ; and
it is easily intelligible, since we are accustomed to the use
of words in everyday life. At the same time, language is
not the only possible means of expression. Physically
regarded, it is a complex bodily movement : spoken lan-
guage is a movement of the larynx, written language a
movement of the hand : and it belongs to the class of
movements that we term gestures. We can express our
ideas by a grimace or a shrug of the shoulders, as well
as by spoken words or a written paragraph.
Now the psychologist argues, by analogy, that what
holds of himself holds also, in principle, of the animal,
of society, and of the insane. He argues that the move-
ments of animals are, to a large extent, gestures ; that
they express or record the animal's mental processes.
He therefore tries, so far as possible, to put himself in
the place of the animal, to find the conditions under which
his own movements would be of the same general kind ;
and then, from the character of his human consciousness,
he attempts — always bearing in mind the limit of de-
velopment of the animal's nervous system — to recon-
struct the animal consciousness. He calls experiment
to his assistance, and places the animal in circumstances
which permit of the repetition, isolation and variation of
certain types of movement or behaviour. The animal is
thus made, so to say, to observe, to introspect; it attends
to certain stimuli, and registers its experience by gesture.
Of course, this is not scientific observation : science, as
32 Subject-matter, Method and Problem of Psychology
we said in § i, implies a definite attitude to the world
of experience, and consists in a description of the world as
viewed from a definite standpoint. None the less, it is
observation, and as such furnishes raw material for
science. The psychologist works the raw material into
shape ; he observes the gesture, and transcribes the ani
mal consciousness in the light of his own introspection.
Roundabout as this method appears, it has nevertheless led, in
the hands of skilled investigators, to perfectly definite results.
And it is by way of detailed investigation, and by that way only,
that the general questions of animal psychology can be finally
answered. One of these questions is that of the ' criterion of
mind.' How are we to decide whether the animal before us
does or does not possess mind? How are we to decide whether
it has attended to the stimulus, so that its movement is a gesture
movement, or whether it has received the stimulus mindlessly
and mechanically, so that the movement is a reflex? An answei
now commonly given to this question is that we may assume the
presence of mind wherever the animal rapidly adjusts itself to
new conditions, quickly learns to get its bearings in a novel
environment. The answer is, of course, based upon the analogy
of human experience. It is, however, unwise to commit oneself
to a criterion of this nature. What is needed is an exhaustive
study of all the various modes in which animals do, as a matter
of fact, adjust themselves to new conditions. Then the criterion
of mind will appear, so to speak, of its own accord.
Another general question is that of the interpretation of the
animal consciousness. Shall we assume that this consciousness
is always as simple as possible? Or shall we give the animal
the benefit of our doubt, take its different forms of behaviour at
their face value, and ascribe to it processes of memory; of idea-
tion, of reasoning, that differ from our own only in degree? On
this question opinion is sharply divided. Both positions may be
supported by the analogy of the human consciousness, since this
may be, under very similar circumstances, either extremely com-
§ 8. The Use of Analogy in Psychology 33
plex or surprisingly simple. And so we find one authority laying
it down that " in no case may we interpret an action as the out-
come of the exercise of a higher psychical faculty, if it can be
interpreted as the outcome of the exercise of one which stands
lower in the psychological scale "; ^ while another authority de-
clares that "we are too ready to adopt simple — unduly simple —
explanations of the animals by which we are surrounded." - It is,
again, unwise to commit oneself to either view. The animal
must be subjected to experimental test, under conditions of
gradually increasing complexity, and we must find out by actual
trial how far it is able to cope with these conditions. Then our
principles of interpretation will, also, emerge of their own ac-
cord. —
We do, then, make the animals attend to stimuli and report
their experiences to us; we do, after a fashion, make them in-
trospect. This would be impossible if introspection implied a
reflective attitude towards mind, or a special kind of mental
awareness of mental processes. But, as we have seen, intro-
spection is simply observation of dependent experience : it is
therefore precisely the sort of observation that an a-nimal can
make, if it has a mind at all. Our own task is to do what the
animals cannot do : to systematise and interpret the observations
in terms of human consciousness.
What holds of the study of the animal mind holds also
of social psychology. The introspections made in com-
mon by the members of a social group are recorded for
us in the forms of speech, in custom and law, in myth and
religion. Society has introspected, and has recorded its
introspections in these various institutions. It is, ob-
viously, impossible for the psychologist to experiment
upon the social mind in any direct vi^ay. It is therefore
fortunate that nature has made experiments for him. By
^ C. L. Morgan, An Introduction to Compai-ative Psychology, 1894, 53.
■^ W. Mills, The Nature and Development of Animal Intelligence, 1898, 12,
34 Subject-matter, Method and Problem of Psychology
comparing the languages, customs, etc., of different types
of human society at all the different levels of human evo-
lution, he is able to repeat, isolate and vary his observa-
tions ; history furnishes him with a laboratory of social
psychology.
It is clear that the study of social psychology requires the use
of analogy. It is we, the moderns, who study the myths and
customs of primitive man, and we have to psychologise these
myths and customs from our own modern standpoint. Hence it
is natural to find, in works upon the subject, the same sort of
disagreement on general principles that we have noted in the case
of animal psychology. And the remedy is the same. We must
not hastily adopt a particular view of human evolution, but must
patiently examine all the available records; must seek to add to
the records by researches among the lower races of mankind ; and
must then accept the general principles that an exhaustive survey
of the facts suggests to us.
Since social psychology is thus a genetic study, a study of
human development, it has become customary to speak of its
method as a genetic method. In strictness, however, there is no
such thing as a genetic method. There is a genetic point of view,
as there is a static point of view. We may be interested in the
sequence of mental processes, in tracing the course of mind from
simple to complex ; or we may be interested in the coexistence
of mental processes, in unravelling the tangle of a special sort
of consciousness. But the difference of interest does not mean
ii difference of method.
For the psychology of dreaming and of intoxication we
have the advantage of direct introspective records. We
may also have recourse to experiment. A sleeping person,
for example, may be subjected to various kinds of stimu-
lation, and may be aroused, after the stimuli have been
apphed, to give an account of the dream which they oc-
casioned.
§ 8. The Use of Analogy in Psychology 35
The psychological study of hypnosis is less direct, since
the hypnotic subject usually forgets, on arousal, what has
taken place during the hypnotic state. We must therefore
observe his behaviour during hypnosis, taking care to
make our tests as simple and straightforward as possible,
and must then seek to reconstruct the hypnotic conscious-
ness on the analogy of the normal waking consciousness.
It is, of course, possible to secure introspective reports
from hypnotic subjects; but it is still a matter of dispute
whether these reports are true records of observations, or
do not rather reflect the ideas and opinions of those who
are conducting the experiment. The hypnotic subject is
extremely suggestible ; that is to say, he is exceedingly
liable to pick up a hint from the experimenter, and to
report as he thinks the experimenter desires or expects
him to report.
For the study of the insane mind, we have, in the first
place, the utterances and behaviour of insane persons.
We have also the opportunity to experiment ; the inmates
of hospitals may be subjected to systematic tests, the
results of which will give us an insight into their mental
processes. So far, this branch of psychology is in a back-
ward condition, since we have been more concerned to
shelter and, if possible, to cure the insane than to de-
scribe the insane consciousness. Certain forms of in-
sanity are, however, of great psychological interest, and
we may look confidently to a realisation of this interest in
the near future. — •
After all, therefore, it is not so absurd as at first thought
it seems, to say that we require the animal and society
and the madman to introspect. All three may attend;
all three may report their experiences. The attention is
36 Siibject-tnatter, Method and Problem of Psychology
likely to be partial, fitful, roving, and the report is likely to
be transient, equivocal, imperfect ; and so we are com-
pelled, in all three cases, to fall back upon the analogy of
our own consciousness. In other words, it is entirely
possible to work out, by psychological method, a psy-
chology of the animal, of the social, and of the unsound
mind, but it is also very difficult : the psychologist is ex-
posed, at every moment, to the danger of misinterpreta-
tion. However, here as elsewhere in science, the pursuit
of knowledge furnishes its own corrective. Sooner or
later the unfit hypothesis breaks down in face of newly
discovered facts.
§ 9. The Problem of Psychology. — Science seeks always
to answer three questions in regard to its subject-matter,
the questions of what, how, and why. What precisely,
stripped of all complications and reduced to its lowest
terms, is this subject-matter .'' How, then, does it come
to appear as it does ; how are its elements combined and
arranged .-* And, finally, why does it appear now in just
this particular combination or arrangement } All three
questions must be answered, if we are to have a science
that shall satisfy the definition of § i.
It is often said that the answers to the questions ' what ' and
'how' give us a description, the answer to the question 'why ' an
explanation, of the facts with which science deals. This distinc-
tion is useful, if we do not make it too rigid. It would be a grave
mistake to suppose, for instance, that we may first of all work out
an exhaustive description of the world, and then proceed delib-
erately to explain what we have already described. On the con-
trary, knowledge grows by a constant give and take between
description and explanation ; we describe in terms of some theory,
that is, in terms of some tentative explanation, and then we rectifj
§ 9- 'The Problem of Psychology 37
our theory in the hght of the observed facts ; and so on, over and
over again. The distinction is thus logical only ; it does not
point to two successive stages in the history of the special
sciences.
To answer the question ' what * is the task of analysis.
Physical science, for example, tries by analysis to reduce
the world of independent experience to its lowest terms,
and so arrives at the various chemical elements. To
answer the question ' how ' is the task of synthesis.
Physical science traces the behaviour of the elements in
their various combinations, and presently succeeds in
formulating the laws of nature. When these two ques'
tions have been answered, we have a description of physi-
cal phenomena. But science enquires, further, why a
given set of phenomena occurs in just this given way, and
not otherwise ; and it answers the question ' why ' by
laying bare the cause of which the observed phenomena
are the effect. There was dew on the ground last night
because the surface of the earth was colder than the layer
of air above it ; dew forms on glass and not on metal
because the radiating power of the one is great and of
the other is small. When the cause of a physical phe-
nomenon has thus been assigned, the phenomenon is said
to be explained.
So far, now, as description is concerned, the problem of
psychology closely resembles the problem of physics.
The psychologist seeks, first of all, to analyse mental
experience into its simplest components. He takes a par-
ticular consciousness and works over it again and again,
phase by phase and process by process, until his analysis
can go no further. He is left with certain mental pro-
cesses which resist analysis, which are absolutely simple in
38 Subject-matter, Method and Problem of Psychology
nature, which cannot be reduced, even in part, to other
processes. This work is continued, with other conscious-
nesses, until he is able to pronounce with some confidence
upon the nature and number of the elementary mental
processes. Then he proceeds to the task of synthesis.
He puts the elements together, under experimental con-
ditions : first, perhaps, two elements of the same kind,
then more of that kind, then elementary processes of
diverse kinds : and he presently discerns that regularity
and uniformity of occurrence which we have seen to be
characteristic of all human experience. He thus learns
to formulate the laws of connection of the elementary
mental processes. If sensations of tone occur together,
they blend or fuse ; if sensations of colour occur side by
side., they enhance one another : and all this takes place in
a perfectly regular way, so that we can write out laws
of tonal fusion and laws of colour contrast.
If, however, we attempted to work out a merely descrip-
tive psychology, we should find that there was no hope in
it of a true science of mind. A descriptive psychology
would stand to scientific psychology very much as the old-
fashioned natural histories stand to modern text-books of
biology, or as the view of the world which a boy gets from
his cabinet of physical experiments stands to the trained
physicist's view. It would tell us a good deal about mind ;
it would include a large body of observed facts, which we
might classify and, in large measure, bring under general
laws. But there would be no unity or coherence in it ; it
would lack that single guiding principle which biology
has, for instance, in the law of evolution, or physics in
the law of the conservation of energy. In order to
make psychology scientific we must not only describe,
§ 9- The Problejn of Psychology 39
we must also explain mind. We must answer the question
'why.'
But here is a difficulty. It is clear that we cannot re-
gard one mental process as the cause of another mental
process, if only for the reason that, with change of our
surroundings, entirely new consciousnesses may be set up.
When I visit Athens or Rome for the first time, I have
experiences which are due, not to past consciousnesses, but
to present stimuli. Nor can we, on the other hand, regard
nervous processes as the cause of mental processes. The
principle of psychophysical parallelism lays it down that
the two sets of events, processes in the nervous system and
mental processes, run their course side by side, in exact
"Correspondence but without interference : they are, in ulti-
mate fact, two different aspects of the same experience.
The one cannot be the cause of the other.
Nevertheless, it is by reference to the body, to the ner-
vous system and the organs attached to it, that we explain
mental phenomena. The nervous system does not cause,
but it does explain mind. It explains mind as the map of
a country explains the fragmentary glimpses of hills and
rivers and towns that we catch on our journey through it.
In a word, reference to the nervous system introduces into
psychology just that unity and coherence which a strictly
descriptive psychology cannot achieve.
It is worth while, for the sake of clearness, to dwell on this
point in more detail. The physical world, the world of inde-
pendent experience, just because it is independent of the indi-
vidual man, is complete and self-contained. All of the processes
that make it up are bound together as cause and effect ; nowhere
is there a gap or break in their connection. Now, among thr
processes that make up this independent world are the processes
40 Subject-matter, Method and Problem of Psychology
of the nervous system. These are hnked, as cause and effect,
both to one another and also to physical processes, outside the
body, which precede and follow them ; they have their fixed
place in the unbroken chain of physical events ; they may them-
selves be explained, exacdy as the occurrence of dew is explained.
Mental processes, on the other hand, correspond, not to the
whole series of physical events, but only to a small part of them,
namely, to certain events within the nervous system. It is natural,
then, that mental phenomena should appear scrappy, disconnected,
unsystematic. It is also natural that we should seek their expla-
nation in the nervous processes which run parallel to them, and
whose causal connection with all the other processes of the inde-
pendent world ensures the continuity that they so conspicuously
lack. Mind lapses every night, and reforms every morning ; but
the bodily processes go on, in sleep and in waking. An idea
drops out of memory, to recur, perhaps quite unexpectedly, many
years later ; but the bodily processes have been going on without
interruption. Reference to the body does not add one iota to
the data of psychology, to the sum of introspections. It does
furnish us with an explanatory principle for psychology ; it does
enable us to systematise our introspective data. Indeed, if we
refuse to explain mind by body, we must accept the one or the
other of two, equally unsatisfactory alternatives : we must either
rest content with a simple description of mental experience, or
must invent an unconscious mind to give coherence and contin-
uity lo the conscious. Both courses have been tried. But, if we
take the first, we never arrive at a science of psychology ; and if
we take the second, we voluntarily leave the sphere of fact for the
sphere of fiction.
These are scientific alternatives. Common sense, also, has in
its own fashion realised the situation, and has found its own way
out. It is precisely because of the incompleteness and discon-
nectedness of mental experience that common sense constructs
a hybrid world, travelling easily from mental to physical and back
again, filling up the breaks in the mental by material borrowed
from the physical. That way, we may be sure, lies confusion of
thought. The truth underlying the confusion is, however, the
§ 9- The Problem of Psychology 41
implicit acknowledgment that the explanatory principle for psy-
chology must be looked for beyond, and not within, the world of
dependent experience. —
Physical science, then, explains by assigning a cause ; mental
science explains by reference to those nervous processes which
correspond with the mental processes that are under observation.
We may bring these two modes of explanation together, if we
define explanation itself as the statement of the proximate cir-
cumstances or conditions under which the described phenomenon
occurs. Dew is formed under the condition of a difference of
temperature between the air and the ground ; ideas are formed
under the condition of certain processes in the nervous system.
Fundamentally, the object and the manner of explanation, in the
two cases, are one and the same.
In fine, just as the method of psychology is, on all
essential points, the method of the natural sciences, so is
the problem of psychology essentially of the same sort as
the problem of physics. The psychologist answers the
question 'what' by analysing mental experience into its
elements. He answers the question ' how ' by formulating
the laws of connection of these elements. And he answers
the question 'why' by explaining mental processes in terms
of their parallel processes in the nervous system. His
programme need not be carried out in this order : he may
get the hint of a law before his analysis is completed, and
the discovery of a sense-organ may suggest the occurrence
of certain elementary processes before he has found these
processes by introspection. The three questions are in-
timately related, and an answer to any one helps towards
the answers to the other two. The measure of our progress
in scientific psychology is our ability to return satisfactory
answers to all three.
42 Subject-matter, Method and Problem of Psychology
References for Further Reading^
^ I. Herbert Spencer, I'he Genesis of Science, in Essays: Scientific-^
Political and Speculative, ii., 1891.
K. Pearson, The Grammar of Science, 1900, chs. i., iii.
\i. O. Kuelpe, Outlines of Psychology, 1909, § i, 1-7.
W. Wundt, Outlines of Psychology, 1907, §§ i, 2.
§ 3. G. S. Fullerton, A System of Metaphysics, 1904, chs. i., v.
'^ 4. W. James, Principles of Psychology, i., 1890, 128-144 (foi" inter-
action : read with E. B. Titcliener, Were the Earliest Organic
Movements Conscious or dficonscious f in Popular Science
Motithly, Ix., 1901-2, 458-469).
H. Ebbinghaus, Grundziige der Psychologie, i., 1905, § 4 (for
parallelism) .
C. A. Strong, Why the Mind has a Body, 1903, 67-160.
G. S. Fulbrton, Is Man an Automaton? in Popular Science
Monthly, Ixx., 1907, 149-156.
§ 5. For the character of mind as process, see W. Wundt, Philosophische
Studien, x., 1894, 121-124.
§ 6. On observation and experiment, see W. S. Jevons, The Principles
of Science, 1900, Bk. iv., chs. xviii., xix.
On introspection, see G. Spiller, The Mind of Man, 1902, 15-20,
34-37 ; W. B. Pillsbury, A Suggestion toward a Reinterpreta-
tio7i of Introspection, in fournal of Philosophy, Psychology and
Scientific Methods, i., 1904, 225-228.
§ 7. W. Wundt, Outlines of Psychology, 1907, §§ 19-21.
R. M. Yerkes, Atiimal Psychology and Criteria of the Psychic, in
Journal of Philosophy, Psychology and Scientific Methods, ii.,
1905, 141-149.
G. T. W. Patrick, The Psychology of Football, in American
Journal of Psychology, xiv., 1903, 368-381.
1 The works cited under this heading throughout the book are of various
degrees of difficulty, and their point of view is in many cases opposed to that of the
author. To avoid confusion of thought, the student is advised to refer to them
onLy after he has read the book through, and has thus formed a clear idea of the
psychological system which it outlines. Difficulties and contradictions will then
seem less formidable and less vital than they would if encountered at the beginning
of his study of mind.
The dates given are those of current editions. Works that have passed through
a Clumber of editions are, however, quoted by chapter and section ratUer than by
page, so that earlier editions may be used.
Note on the Classification of Psychology 43
T. Heller, Studien zur Blinden-Psychologie, in Philosophische
Stiidien, XI., 1895,226-253; 406-470; 531-562.
§ 8. C. L. Morgan, An Introduction to Comparative Psychology, 1894,
37-47-
W. Wundt, Volkerpsychologie, i., 1904, Einleitung ; also Sprach-
geschichte und SprachpsycJiologie, 1901, § i.
M. F. Washburn. The Aninial Mind, a Text-book of Comparative
Psychology, 1908, chs. i., ii.
§ 9. O. Kuelpe, Introdjiction to Philosophy, 1897, Psychology, 55-67.
W. James, Principles of Psychology, i., 1890, 1-4.
H. Miinsterberg, Psychology and Life, 1899: essay on Psychology
and Physiology, 35-99-
NOTE ON THE CLASSIFICATION OF PSYCHOLOGY
The following list of the various subdivisions of psychology is made
on'' on the basis of the distinctions drawn in § 7. We cannot hope to
make the list final and complete. But it is well to realise, at the begin-
ning of one's study of mind, how wide and varied is the territory that
psychology covers.
L Psychology of the Normal Mind
A. Individual psychology
i. Human psychology . This may be subdivided into :
1. General psychology, or the psychology of the adult civilised
man. This is the principal topic of the text-books of psy-
chology : see, for instance, W. James, Principles of Psychol-
ogy, 1890; J. Sully, The Human Mi7id, 1892.
2. Special psychology, or the psychology of the human mind in
some other stage than that of adult manhood. Special psy-
chology thus includes infant psychology, child psychology,
the psychology of adolescence, the psychology of senility,
etc. These psychologies are often written from the genetic
point of view. — W. Preyer, The Mind of the Child, 18S8-9
\L)ie Seele des Kindes, 1900] ; G. S. Hall, Adolescence, 1904.
3. Differential psychology, or the study of tlie differences between
individual minds. The minds compared may belong to per-
sons of the same race, class, age, sex, etc., or to persons who
differ in these respects. — L. W. Stern, Ueber Psychologic der
44 Subject-matter, Metfiod and Problem of Psychology
individiiellen Differ enzen, igoo ; A. Binet, L' Etude experi-
inentale de Vmtelligence, 1903-
4. Genetic psychology, which seeks to trace the development of
mind from infancy to manhood, and its gradual decay in old
age. — J. M. Baldwin, Mental Development in the Child aiid
the Race, 1906.
U. Animal psychology. This may be subdivided, like human psy-
chology, into general, special, differential and genetic psy-
chology. Since the workers in the field of animal psychology
have, for the most part, been interested in the problems of
mental evolution, animal psychology as a whole is often
termed genetic psychology: but this is a misnomer. — E.
Thorndike, Atiinial Intelligence, 1898; H. S. Jennings, Be-
haviojir of the Lower Organisjiis, 1906.
iii. Comparative psychology . This is the comparative study, either of
various types of animal mind, or of the minds of the animals
and of man. It may be general, special or genetic. Like
animal psychology, and for the same reason, it is often
termed genetic psychology. — C. L. Morgan, An Introduc-
tion to Comparative Psychology, 1894; W. Wundt, Lectures
on Human and Animal Psychology, 1896 \_Vorlesungen iiber
die Menschen- und Thierseele, 1906] ; M. F. Washburn, The
Atiitnal Mind, 1908.
B. Collective psychology
The divisions of this department of psychology are not as yet sharply
defined. We may, however, distinguish :
i. Social psychology, which includes the study of the social conscious-
ness, and also the study of the products of the collective
mind : language, law and custom, myth and religion. — G.
Tarde, Social Laws, 1899; J. M. Baldwin, Social and Ethi-
cal Interpretations in Mental Developnicnt, 1906 : W. Wundt,
V'olker psychologic, 1904-8.
ii. Ethnic psychology, the diffei^ential psychology of nations or races. —
G. le Bon, The Psychology of Peoples, 1898; W. H. R. Riv-
ers and C. S. Myers, Cambridge Anthropological Expedition
to Torres Straits, 190 1-3.
iii. Class psychology, the differential psychology of classes, professions,
etc. — E. Tardieu, Psychologie fnilitaire, 1898; L. Dauriac,
Essai sur V esprit musical, 1904.
Note on the Classification of PsycJiology 45
II. Psychology of the Abnormal Mind
A. Individual psychology
i. Psychology of deficient and exceptional minds. — M. Howe and F.
H. Hall, Laura Bridgman, 1903; C. Lombroso, Tlie Man of
Genius, 1891 [Z' uoino di genio, 1894].
ii. PsycJiology of mental deraHge?nent, the study of temporary abnor-
malities of mind. — A. Maury. Le sonnneil et les 7-tves, 1878 ;
A. Moll, Hypnotism, 1890; E. Parish, Hallucinations and
Illusions, 1897; S. de Sanctis, I sogni, 1899.
ill. Psychology of mental disorder, the study of the permanently de-
ranged mind. — -T. Ribot, Diseases of Personality, 1895; G.
Storring, Mental Pathology in its Relation to Normal Psy-
chology, 1907.
B. Collective psychology
Psychology of mental derangement. — J. Jastrow, Fact and Fable in Psy-
chology, 1900; S. S'\^t\&, La foule criminelle, 1901.
SENSATION
§ 10. The Elementary Mental Processes. — It is very im-
portant that we make no mistake as regards the nature
and number of the elementary mental processes. For
these elements are the simple materials out of which we
are to build up our entire psychology. They must, there-
fore, be various enough and numerous enough to give rise,
by their connections, to all the complicated phases of the
human mind : to thought and sentiment, to memory and
imagination, to emotion and perception. On the other
hand, they must be strictly elementary ; they must remain
unchanged, however persistent our attempt at analysis and
however refined our method of investigation. If the list
is not complete, we shall be forced presently to smuggle
in new elements : and that means bad logic and bad
science. If we now pass as elementary any process that
is really complex, we are guilty of a sheer blunder, and
shall pay for it later on.
Here, however, is a dilemma. The science of psychol-
ogy is still in the making ; and, until it is rounded out and
finished off, no final list of the mental elements can pos-
sibly be drawn up. We must make a decision in the mat-
ter; but we must not be dogmatic: we must stand ready
to modify our decision, if the results of future research
prove us to be wrong. Such a state of affairs is, perhaps,
a little discouraging, since a right choice of elements is of
cardinal importance ; but it is not unnatural, nor is it dis-
46
§ lo. T]ie Elementary Mental Processes 47
creditable to psychology. All scientific problems require
time for their solution ; and this problem of the nature
and number of the mental elements is comparatively new,
— certainly not older than the middle of the last century.
So long as mind was looked upon as a substance, a real
being, a personal creature, psychology had no more to
do than to note down the different powers or faculties or
capacities of the mind, as they fell under observation.
The list always remained open. Not until mind is re-
garded as a stream of processes, whose flow is through-
out obedient to psychological law, does the problem of
analysis become insistent. Besides, this problem can be
solved only by help of the experimental method ; and the
first laboratory of psychology was founded as late as 1879.
It is not surprising, then, that psychologists should still
disagree as to the mental elements. Every year sees the
proposal of some fresh process as candidate for element-
ary rank ; every year brings proof that one or other of the
older candidates must, after careful scrutiny, be debarred
from competition. And this back-and-forth movement will,
continue, we must suppose, for many years to come.
There is, nevertheless, beneath all these cross-currents
of controversy, a fairly definite trend of psychological
opinion in the matter of the elementary processes. The
list that we adopt in this book is accepted by a large num-
ber of psychologists, and, as a working hypothesis, has so
far proved adequate to the composition of the human mind.
If it has to be changed in the future, we may be tolerably
sure that the change will come by way of addition, and
not of subtraction, so that our acceptance of it will give us
nothing to unlearn. — We set to work upon the assump-
tion that there are at most three classes of mental ele-
48 Sensation
ments ; that two of these may, without any hesitation, be
considered as sub-classes under a single general heading,
even if they may not be grouped outright in a single class;
and that all three may, with some show of probability, be
viewed as processes of the same ultimate type.
The three classes of elementary processes are known
as sensations, images, and affections. Sensations are, of
course, the characteristic elements of perceptions, of the
sights and sounds and similar experiences due to our pres-
ent surroundings. Images are, in just the same way, the
characteristic elements of ideas, of the mental pictures that
memory furnishes of past and imagination of future expe-
rience. Sensations and images are so much alike that they
are not seldom confused ; we shall discuss their relations
in detail in § 61. Lastly, affections are the characteristic
elements of emotions, of love and hate, joy and sorrow.
At first sight, they appear to be essentially different from
sensations and images, though a closer examination brings
out a number of fundamental resemblances. We shall dis-
cuss them in § 69.
It is our business, then, to describe and explain these
elementary processes, and to show that, when grouped
and arranged in certain uniform ways, they give rise to
the different complex processes that constitute human
consciousnesses.
We shall have occasion, later on, to say something about vari-
ous other processes that have been put forward as elementary.
Many psychologists, for instance, accept an additional class of
relational elements. A quotation from Herbert Spencer will show
what is meant. "The proximate components of mind," he writes,
"are of two broadly-contrasted kinds — Feelings and the Rela-
tions between feelings. [The wora ' feelings ' here may be taken
§ II. Elements and Attributes 49
to include our sensations, images and affections.] Under an ulti-
mate analysis, what we call a relation proves to be itself a feeling
— the momentary feeling accompanying the transition from one
conspicuous feeling to an adjacent conspicuous feeling. Notwith-
standing its extreme brevity, its qualitative character is apprecia-
ble." ^ These relational processes we discuss in § 140. Again,
some psychologists have postulated a conative element, or ele-
mentary process of will ; others have set thoughts, as elementary
processes, alongside of sensations and images. These, too, we
discuss, in §§ 127, 139. The great majority of such pretenders
may, however, be passed over in silence. They die and are dis-
sected in the pages of psychological magazines, and do not live
long enough to be mentioned in text- books.
§11. Elements and Attributes. — We have taken it for
granted that the mental elements may be arranged in
groups or classes. It may be objected that, since they are
elements, — since they resist analysis, and cannot be re-
duced to anything simpler than themselves, — we can have
no means of grouping them. How is it possible to find
degrees of hkeness and degrees of difference between
absolutely simple things.''
The psychologist arranges the mental elements precisely
as the chemist classifies his elementary substances. The
chemical elements are divided, for instance, into metals
and non-metals. The metals have a high power of reflect-
ing light; they are opaque; they are good conductors of
heat and electricity ; they have high specific gravities. So
they are set off, as a group, from the non-metals. These
latter, again, include both gaseous and solid elements.
That is to say, the chemical elements possess certain prop-
1 Principles of Psychol os;y, i8Si, vol. I., pt. ii., ch. ii., § 65, The quotation
has been somewhat simplified.
50 Sensation
erties or attributes, by means of which they may be dis-
tinguished and arranged.
It is just the same with the mental elements. These are
simple, it is true, in the sense that they are mental experi-
ence reduced to its lowest terms ; but they are still real
processes, still actual items of mental experience. Hence,
like the chemical elements, they show various aspects or
attributes, —present different sides, so to speak, — each
of which may be examined separately by the psychologist.
It is by reference to these attributes that introspection is
able to classify them under different headings. —
There is no more agreement in psychology about the
attributes of the mental elements than there is about the
elements themselves. It is, indeed, probably true to say
that there is not so much ; the lists given in the different
text-books seldom correspond in all details.
Various reasons may be given for this divergence of
opinion. It is often said, for example, that the psycholo-
gist must remain in doubt as regards the attributes of a
mental element because he can never actually isolate the
element itself, in order to bring it under separate observa-
tion. The human mind is so complex, and the avenues of
approach to the human nervous system are so numerous,
that he can never reduce consciousness to a single, simple
process. Now in strictness this statement is, no doubt,
entirely correct. At the same time, it is possible to arrange
experimental conditions in such a way that, for all practical
purposes, one process and one process only is presented
for observat.'on. If we rule out distracting influences, and
concentrate the attention upon, say, a particular sensation,
then this sensation stands out clear and distinct, and all the
rest of consciousness becomes a vague blur of indifferent
§ II. Elements and Attributes 5 1
processes. Practically, therefore, the psychologist can
isolate a mental element, and can, as was said above, ex-
amine separately its various aspects or attributes. The
reason for difference of opinion in regard to these attributes
must be sought elsewhere.
The chief reason lies in the difficulty of deciding what is
original in the sensation, inherent in it, constitutive of it,
and what is mere accretion. The human nervous system,
we must remember, has an immensely long history, is the
outcome of long ages of development. The result is that
it is full of short cuts ; it is shot through and through with
paths of direct connection. When, therefore, we think
that we have a bare sensation before us, it is quite possible
that we are, in reality, observing a complex process. What
appears to be an aspect or attribute of the sensation may,
in reality, be a separate process, so habitually and insepara-
bly connected with the sensation in the past as now to
seem an integral part of it. Let us take an instance.
We hear two tones, from the deep bass and the high
treble. The former sounds voluminous and massive; the
latter sounds small and sharp. Are we to conclude, then,
that volume is an original attribute of tones.'' that tonal
sensations possess a kind of solidity, a vague extension in
the three dimensions of space .'' Some psychologists accept
this conclusion. Others believe, on the contrary, that the
volume which attaches to tones is a distinct process, and
that it belongs not to hearing but to sight. When we hear
a deep tone, that is, we are reminded of things that look
large and soft ; and when we hear a high tone, we are re-
minded of things that look small and hard : there is nothing
large or small, soft or hard, about the tones themselves.
Here, then, is the difficulty, — in deciding what is inherent
r 2 Sensation
in tonal sensation and what is merely accessory : there is
no difficulty in isolating the tones for separate observa-
tion.
Another reason may be found in the fact that, the more
closely a particular kind of element is studied, the more
many-sided is it likely to appear. Hence the specialist in
any department of psychology will sometimes claim for his
elements a larger number of attributes than the student of
general psychology can discover in them. We may again
illustrate this difference of opinion by reference to tones.
Most of us would be disposed to think that a sensation of
tone is characterised, simply and sufficiently, by its pitch,
its definite position — high or low — upon the tonal scale.
But the special student tells us that what we take to be a
simple attribute of pitch is, in point of fact, the unanalysed
resultant of no less than three distinct attributes.
Agreement will come with time ; persistent observation,
refining the longer it is continued, will someday settle the
questions that we are here discussing. Meanwhile, the
important thing is that we keep our minds open, and ob-
serve as carefully and impartially as we can. And if there
are many occasions when we must speak less positively
than we could wish, there is, on the other hand, the com-
forting reflection that an unfinished science is a good deal
more interesting than a science whose facts and laws are
already cut and dried.
§ 12. The Attributes of Sensation. — A sensation, as the
term is used in this book, may be defined as an elementary
mental process which is constituted of at least four attri-
butes, — quality, intensity, clearness and duration. There
are sensations for which the list of attributes is longer; but
§ 12. TJic Attributes of Sensation 53
these four are essential. We will consider them briefly, in
the order of mention.
Quality is, so to say, an individual attribute ; it is the
attribute which distinguishes every elementary process
from every other. It is, accordingly, the attribute which
gives a sensation its special and distinctive name : cold,
blue, salt, b^ , — these are all names of sensation qualities.
Intensity is the attribute to which we refer when we say
that a given sensation is brighter or duller, louder or fainter,
heavier or lighter, stronger or weaker, than another sensa-
tion. In making such comparisons, we think of the sen-
sations as possessing the same quality : both are blue,
both are ^*^, both are pressure, both are cold or salt or asafoe-
tida : but these two sensations, of the same quality, lie at
two different points upon a finite scale of sensation degrees,
which begins at a lower limiting value and rises to a max-
imum. The more intensive sensation is placed higher up,
the less intensive lower down, upon the scale of intensities.
Clearness, again, is the attribute which gives a sensation
its particular place in a consciousness : the clearer sensation
is dominant, independent, outstanding, the less clear sensa-
tion is subordinate, undistinguished in the background of
consciousness. If, for instance, we are listening to tones
in order to decide whether or not they all alike possess the
attribute of volume, the sensations are clear ; if we are
absorbed in work of a different kind, and someone is ex-
perimenting with tones in the next room, we still have the
tonal sensations, but they are obscure. Lastly, duration is,
as its name imphes, a temporal attribute ; it is the attribute
which makes the course of a sensation in time — its rise,
poise and fall as process in consciousness — -characteris-
tically different from the course of another sensation.
54 Sensation
All sensations, without exception, possess the attributes
of quality, intensity, clearness and duration. The list may
be lengthened in two ways : by the splitting up of an attri-
bute which has hitherto been regarded as simple, and by
the discovery of attributes altogether different from the
essential four.
On the first point, we have already remarked that what
appears to ordinary observation as a simple attribute of
quality may turn out, on closer examination, to be the
unanalysed resultant of two or three distinct attributes.
This is the case with tones, and also, as we shall see pres-
ently, with colours. The second point is best illustrated
by reference to sight and touch. Sensations of colour are
spread out areally into length and breadth ; they appear as
spatial extents. And this attribute of extent is part of
their very constitution. Reduce the colour to a pin point,
and it still occupies space ; think away the spatial attribute,
and the sensation has disappeared with it. So with press-
ures : set the point of a stiff horse-hair lightly down upon
the skin, and the sensation is extended, diffused over a
mental area. Certain sensations, then, have this attribute
of extent ; others, as odours and tones, show no trace of it.
We come back to these facts, in detail, when we discuss
the various classes of sensations.
The longest list of attributes is possessed by colour sensations.
What we ordinarily term the quality of colour is the resultant
of three qualitative attributes : colour-tone or hue, light-tone or
tint, and colour-depth or chroma. To these three must be added
the intensive attributes of intensity proper, clearness, duration and
extent.
It is to be noted that, in certain cases, the concurrence
of two or more. attributes gives rise to what we may call an
§ 13- The Classification oj Sensations 55
attribute of the second order. Thus, certain sensations
have been credited with an attribute of insistence. They
are self-assertive and aggressive ; they monopolise con-
sciousness, as a forward and pushing guest will monopolise
conversation at a social gathering. We speak of the pene-
tratingness of odours like camphor and naphthaline ; of the
urgency or importunity of certain pains or of the taste of
bitter ; of the obtrusiveness or glaringness of certain lights
and colours and tones. This character of insistence is,
however, not a new primary attribute of the sensations. It
is the resultant of clearness conjoined with quality, or with
intensity, or with quality and intensity together.
§ 13. The Classification of Sensations. — Introspection
leaves no doubt that the sensations, regarded as qualitative
processes, fall into a number of separate groups. All
colour sensations, for instance, go together ; all tonal sensa-
tions go together. Colours, again, are more akin to greys,
and tones to noises, than are colours to tones. This kin-
ship between certain sense qualities means, in general,
that the sensations fall into continuous series, so that one
can pass from quality to quality as if along a straight line,
without leaving one's path or meeting with a gap or inter-
ruption. It is possible to travel in this way from bass to
treble, through the middle tones of the scale, or from red
to white, through a series of pinks : it is not possible to
travel from a colour to a tone.
We may, then, classify sensations in terms of their in-
trospective resemblances. We may also, with change of
standpoint, classify them by reference to the body, since
observation has shown that every group of sensations
comes to us by way of a definite, specially developed bodily
56 Sensation
organ. The sensations of a particular group will then be
those whose parallel bodily processes, in spite of difference
of detail, have the same general effect within the organism.
We may accordingly speak of eye sensations, muscle sen-
sations, etc. Such a Hst, if completed, would be perfectly
accurate.
Finally, we may classify sensations by reference to the
stimuli which arouse them. Sensations at large fall into
two principal groups, according as their stimulus is external,
originating outside the body, or internal, originating within
the body. Light, the stimulus to vision, is an external
stimulus ; muscular contraction, the stimulus to muscular
sensation, is an internal stimulus. We therefore distinguish
between sensations of the special senses, which are stimu-
lated from without, and organic sensations, whose stimulus
consists in a changed state of the internal bodily organs
from which they come.
Not all the sense qualities that are ordinarily grouped together
fall into continuous series, like the series of colours and tones.
We naturally think, for example, of the sensations of pressure and
temperature as forming a group of qualities, although no transition
is possible from one quality of the group to another. We naturally
think, again, of the sensation of warmth as very closely related to
the sensation of cold, although there are no qualities which join
these two sensations, and. although their sense organs are distinct.
It might seem, then, that the sensations of pressure and tempera-
ture are bracketed together simply by reference to the skin as
their common organ, and the sensations of warmth and cold simply
by reference to their common stimulus. Nevertheless, there is a
real introspective resemblance between them. Pressure is more
like warmth and cold than it is like tone or colour ; and we do
not feel the jar, in passing from cold to warmth, that we should
feel if the disappearing cold were followed by a low tone or a
References for Further Reading 57
faint odour. The kinship which introspection finds among these
sensations is, in the last resort, a matter of conscious context : the
sensations from part of consciousnesses of the same pattern, make
the same sort of connections in consciousness, are more or less in-
terchangeable in consciousness.
In making out a list of the various departments of sensation,
we are at times compelled to speak in terms of sense-organ or of
stimulus, for the simple reason that the sensations themselves
have not received a name. There is, for instance, no name to
designate the peculiar quality of the sensation aroused by con-
traction of striped muscle. Language has developed at the com-
mand, not of theoretical interest, but of practical convenience ;
and there has been no pressing reason for the naming of all the
separate sensations. Even in the case of colours, we have terms
Hke violet and orange, the names of flower and fruit, alongside of
the much older terms blue, red, etc. ; and to denote a particular
tone we have to use such clumsy expressions as 'the c of the thrice
accented octave.'
References for Further Reading
§§ lo, II. E. B. Talbot, The Doctrine of Conscious Elements, Philo-
sophical Review, iv., 1895, 154.
M. F. Washburn, Sotne Examples of the Use of Psychological
Analysis in System-Making, Philosophical Review, xi., 1902,
445-
E. H. Hollands, Wnndfs Doctrine of Psychical Analysis and the
Psychical Elements, and Some Recent O'iticism: i. The Cri-
teria of Elements and Attributes, American fournal of Psy-
chology, xvi., 1905, 499.
O. Kuelpe, Outlines of Psychology, 1909, § 40 (elementary quality
of will).
§ 12. M. W. Calkins, Attributes of Sensation, Psychological Review,
vi., 1899, 506.
M. F. Washburn, Notes on Duratioti as an Attribute of Sensa-
tions, ibid., X., 1903, 416.
M. Meyer, On the Attributes of the Sensations, ibid., xi., 1904, 83.
E. B. Titchener, Lectures on the Elejnentary Psychology of Peel-
ing and Attention, 1908, Lecture i.
58 Sensation
It should be said that current works on psychology differ, not only
as regards the nature and number of the elementary mental processes
and their attributes, but also as regards the principles and aims of psy-
chological analysis in general. The fact is not surprising, when we
remember that the fundamental questions treated in the Introduction —
the questions of subject-matter, method and problem of psychology —
are still in debate. The reader may compare with the discussion of
the preceding paragraphs G. F. Stout, The Groundwork of Psychology,
[1903] ch. iii. ; C. H. ^wAd,, Psychology : General Introduction, 1907,
ch. iv. He should, nevertheless, look for underlying agreements
rather than for superficial differences. Judd's preface, for instance,
opens with the sentence : " There is very general agreement as to the
main topics which must be treated in a text-book on psychology."
THE QUALITY OF SENSATION: VISION
§ 14. The Visual dualities. — It needs but a casual
glance at our surroundings, indoors or out, to assure us
that the world of vision comprises a very large number of
sense qualities. Besides all the wealth of colour, there is
the whole scale of light, from the most brilhant white to
the deepest black. Both alike are qualitative systems :
black, white and grey, red, yellow, green and blue, — one
and all are qualities of sensation, individual and elementary
mental processes. To a certain extent, the sensations of
light and of colour are independent of each other : a land-
scape or a coloured painting may be translated, by pho-
tography, into an arrangement of blacks, whites and greys.
They are also, however, closely related. We speak of cer-
tain colours, without hesitation, as being darker or lighter,
that is, nearer black or nearer white, than other colours ;
and we meet with colours of all grades or degrees, from
the full quality, the deep red or rich green, to the merest
tinge which is but a step from grey.
If we look, first, at the sensations of light, we find that
they form a single linear series, extending from white
through the lighter, neutral and darker greys to black.
Language has very few words to denote the qualities of this
series. We speak of black, for instance, as if it were a
single quality. But glance, in succession, at black card-
board, black cloth, black velvet, and the black of a com-
paratively lightless space, — say, the blackened interior of
so
6o The Quality of Sensation : Vision
a long pasteboard tube. You realise at once, not only that
these four blacks are qualitatively different, but also that
their differences are quite considerable, so that there must
be several intermediate blacks between the successive terms
of the series. The same thing holds of white. Lay upon
the window-sill a sheet of white paper, and on this place a
cover-glass, silvered on the under side, in such a position
that the glass reflects a patch of uniformly bright sky.
The reflected light is astonishingly white, and the white of
the paper seems, by comparison, greyish. There are in
all, if we count up the distinguishable whites, greys and
blacks, between six and seven hundred qualities of light
sensation.
The system of colour sensations is less simple ; the
colour qualities cannot be arranged upon a single straight
line. Let us take, as the arrangement of colours with
which we are most familiar, a chart or a projection of the
solar spectrum, and let us work through it, from the left
or long-wave to the right or short-wave end. On the ex-
treme left we have the quality of red. As we travel to the
right, the red takes on more and more of a yellowish tinge,
until it passes through orange to a pure yellow. Here,
then, we have a linear series of qualities, precisely similar
to the series of light sensations. Now, at yellow, we change
our direction. The yellow gradually becomes tinged with a
new quality, that of green ; it passes through yellow-green
to a pure green. Here is a second line of qualities. Again
we change our direction ; the green becomes more and
more bluish, until it passes through blue-green to a pure
blue. Here is a third line of qualities. Once more we
change our direction. This time, however, the tinge that
our initial quality takes on is not new ; the blue becomes
§ 14- TJie Visual Qualities 6 1
increasingly reddish, as we travel to the right-hand end of
the spectrum. Here is a fourth line of qualities, but a line
which in the spectral series is left incomplete at violet. If
we continue it, by adding the purples and carmines, we are
finally brought back to our starting-point, — the red of the
extreme left. We notice, however, that this red is not, in
reality, the starting-point of a psychological colour-line ; it
is not a pure red, but an orange-red ; the red that stands
at the beginning of the red-yellow line lies outside the
spectrum, toward the carmines.
All the colours that can be distinguished upon these four
lines are ultimate qualities of visual sensation. We speak,
it is true, of pure red and of orange-red ; but these terms
merely indicate the position of the qualities upon a colour-
line : pure red comes at the beginning, orange-red towards
the middle of the line. No orange-red can be analysed, by
introspection, into a red and an orange. The lines them-
selves, and with them the system of colour qualities, are
most simply arranged in the form of a square, with R, V,
G and B at the four corners.
So far, then, we have a single straight line to represent
the sensations of light, and four straight lines, forming the
closed figure of a square, to represent the sensations of
colour. But so far, also, we have dealt with sensations of
colour only under one aspect, — that of colour-tone or hue.
Colours, as was said above, differ further from one another
as darker and lighter. Thus, in the spectrum, yellow is
undoubtedly the lightest, and violet the darkest colour.
Here, then, is a second attribute of colour, the attribute of
light-tone or tint, in virtue of which a sensation of colour
may be matched or equated with a sensation of light. Let
us assume that all the hues upon the lines of our colour-
62 The Quality of Sensatioti : Vision
square are of the same tint, and that this tint is that of a
grey situated midway between white and black. Then, if
the line of light sensations is erected as a vertical, the four
colour-lines will lie about it in the horizontal plane, and at
the level of this middle grey. All the lighter reds, or
pinks, will stand in order above the point R, opposite the
particular light greys to which their tint corresponds ; all
the darker reds will stand in order below R, opposite the
dark greys to which their tint corresponds ; and so with
the lighter and darker Y, G and B. The vertical line,
which represents the whites, greys and blacks, is thus sur-
rounded by a square tube, whose walls are made up of all
the hues in every possible variety of tint.
Suppose, now, that a line is drawn from some point on
the wall of the tube to the corresponding point upon the
vertical line : say, from the point R to the middle grey.
The sensations that lie upon this new line form a series of
the same hue and the same tint ; but they differ in respect
of a third attribute, that of colour-depth, or degree of
saturation, or chroma. The red at R, which is farthest
out from the corresponding grey, is a rich, full, deep red ;
it contains all the red that a visual sensation can contain,
just as a saturated solution in chemistry contains all of the
dissolved substance that it can contain ; it shows the attri-
bute of chroma at a maximum. As we proceed inwards,
towards grey, the reds become less saturated, more washed-
out; their chroma decreases and finally, when the grey is
reached, entirely disappears.
As these chromatic lines may be drawn from any point
upon the square shell to the corresponding point upon the
vertical, our representation of visual sensations becomes a
solid figure, a square prism. In actual observation, how-
§14- The Visual Qualities
63
ever, the lines are not all of the same length ; they arc
longest for hues of a middle tint, shortest for hues of very
dark and very light tints. There are, obviously, but few
intermediate steps between a
very dark blue and the corre-
sponding greyish black, or be-
tween a very light yellow and
the corresponding greyish white.
The square prism thus becomes
a double pyramid. At the two
poles stand the extremes of
white and black ; upon the ver-
tical axis, between the poles, are
arranged the remaining sensa-
tions of light. Round the base
of the figure lie all hues of a
middle tint and of maximal
chroma. Between base and poles
lie the same hues in all their
further variety of tint ; all are
still of maximal chroma, though the chromatic maximum
decreases steadily, above and below. If we cut into the
pyramid, from any point on the outside to a corresponding
point upon the axis, we lay bare a series of sensations of
the same hue and tint, but of varying chroma.
The double pyramid, then, as drawn in Fig. 2, embodies
the two systems of visual sensation, sensations of light
and sensations of colour, and shows these systems both in
their mutual independence and in their mutual relations.
There are at least a hundred and fifty distinguishable hues
round the base. In counting up the whole number of
visual sensations we must, however, take account also o^
Fig. 2. The Colour Pyramid.
64
The Quality of Sensation : Vision
differences in tint and in chroma. These are ultimate
differences : a pink is no more analysable by introspection
into a red and a white
than an orange-red is an-
alysable into a red and an
orange. All in all, the full
tale of the visual elements
cannot fall far short of
thirty-five thousand.
§ 15. Visual Stimulus
and Visual Sensation. —
The trains of ether waves
which constitute light, in
the physical sense, differ
in three ways : in wave-
length, in wave-ampli-
tude or energy, and in
wave-form or composi-
FlG. 3. Demonstrational Colour Pyra- tion. In general, these
r^\A.- American Journal of Psychology, ^^^^^ aspectS of the ether
XX., 1909, 15.
waves correspond to the
three attributes of colour sensation, — hue, tint and chroma.
At the red end of the spectrum, the light-waves have a
length, roughly, of 700 /u/a; at the violet end a length,
roughly, of 400 /xyu, ; and the intervening hues are corre-
lated with intermediate wave-lengths. If we increase or
decrease the energy of these waves, within certain limits,
the colours as a whole become hghter or darker, — there is
a change of tint; but the distribution of hues, and the
relative degrees of tint and chroma, remain unchanged.
Lastly, the fact that the spectral hues possess a high
§ 15- Visual Stimuhis and Visual Sensation 65
chroma, while the colours that we see in nature and art
are less saturated, is due to the relative simplicity of wave-
form in the one case and its relative complexity in the
other. These are, however, only general correspondences.
In detail, the relation between visual stimulus and visual
sensation is very far from simple.
There is, indeed, one case — the case of the sensation
black — in which there seems, at first thought, to be no
relation at all. It is often said, paradoxically, that the
stimulus to black is the absence of physical hght. If this
were true, black would stand apart from all the other
visual qualities. But, on the one hand, what we see in the
absence of light is not black. ' In the night all cats are
grey ' ; and the absence of light means, in point of fact,
that our surroundings appear in a neutral grey. On the
other hand, we can see black only in a good light ; so
that the sensation of black, like the after-images and
contrast-sensations of which we speak in § 18, is indi-
rectly, although not directly, dependent upon the presence
of physical light. We discuss the question of its origin
in § 22.
Black is, of course, a positive sensation ; as it is not due to the
absence of light, so it does not represent the absence of visual
sensation. To suppose that the blind live in darkness is altogether
wrong, because it is to suppose that they are able to see. Blind
persons see things, as Helmholtz puts it,-^ in the same way in which
we ourselves see what is behind our backs : that is to say, they do
not see them at all.
§ 16. The Dependence of Visual Sensation upon Wave-
length and Energy of Light. — In general, as we have
^ H. L. F. von Helmholtz, Handbuch der physiologischen Optik, 1896, 324.
F
66 The Quality of Sensation : Vision
said, change in the wave-length of physical light means
change in the hue of colour sensation. This statement
must now be qualified in three ways.
First, we find by reference to the spectrum that the
correspondence of wave-length and hue is not uniform
throughout the colour series. At the two ends, in R and V,
we may travel for a considerable distance without noticing
any marked change of hue. If, on the other hand, we
look at the regions on either side of Y, or at the BG
region, we see at once that a very large number of hues
is there packed into a very small space. Secondly, we
find that difference of wave-length brings with it a differ-
ence of chroma. The most saturated colours of the
spectrum are R and B ; the least saturated are Y and BG.
Chroma, therefore, depends upon wave-length as well as
upon wave-form. Thirdly, we find that change of wave-
length brings with it a change of tint. We have already
remarked that Fis the lightest and F the darkest colour
of the spectrum. Now the energy of the light-waves de-
creases continuously from the long-wave to the short-wave
end ; ^ so that, if tint depended solely on energy or wave-
amplitude, R and not F should be the lightest colour, and
B, as compared with R, should be much darker than is
actually the case.
In the same way, change in the energy of physical light
may change, not only the tint, but also the hue and the
chroma of colour sensations. If the energy of the light-
waves which form the spectrum is greatly increased, the
^ This statement holds of the dispersion spectrum of an artificial light,
such as is usually observed in psychological laboratories. In the diffraction
spectrum of sunlight — what physicists term the 'normal' spectrum — the
maximum of energy is in the blue.
§ 1 6. Effect of Wave-length and Energy of Light 6y
hues are reduced to two, Fand B, both of light tint and
low chroma. The R, O and VG of the original series be-
come lighter and yellower; the BG and F become lighter
and bluer ; G becomes simply lighter, and finally passes into
a light grey. If the energy is greatly decreased, the hues
are reduced to three, R, G and B V, all of dark tint and low
chroma. At the same time there is a marked change in
the relative distribution of tint throughout the spectrum :
all the colours are darker, but the position of the relatively
lightest tint moves from F to G, — so that the long-wave
end is darkened, and the short-wave end lightened, in com-
parison with the ordinary spectrum. This shift of tint with
decrease of energy is called, after the Austrian physiologist
who first observed it, the Purkinje phenomenon.^
The Purkinje phenomenon appears most clearly when the
energy of the spectrum has been so far diminished that the
colours fade out altogether, and only a series of sensations of
light is left. It appears, in any case, only if the energy of light
is decreased over the whole field of vision ; it is not enough to
reduce the energy of the spectrum alone. You may get an idea
of it by laying pieces of red and blue paper side by side, and
observing them first in ordinary diffuse daylight and then through
a pin-hole in a card. Or if you watch the reds and blues of a
carpet, as twilight comes on, you will notice that the reds quickly
become dark grey or black, while the blues change into a silvery
blue-grey. This aspect of the phenomenon, in which it depends
upon the general illumination of our surroundings, is dealt with in
§§ I9> 22.
§ 17. The Dependence of Visual Sensation upon Compo-
sition of Light. — In tracing out the dependence of visual
sensation upon the form or composition of light-waves, we
1 J. Purkinje, Beobachtungen und Versuche zur Physiologic der Sinne, ii.,
1825, 109.
68 The Quality of Sensation: Vision
may most conveniently employ the colour-mixer, with com-
pound discs of the sort mentioned in § 6. Everyone
knows that a glowing match, whirled round in the air, is
seen as a fiery circle: the effect produced upon the eye by
the moving stimulus persists for a time, in what is termed
the positive after-image, until the stimulus comes back
again to the same point. This is the principle which
underlies the use of the rotating discs. It is, further,
a law of physiological optics that if such particoloured
discs are rotated at a rate of speed sufBcient to prevent
flicker, the resulting impression upon the eye is the same
as it would be if the physical light, reflected from the
several sectors, were spread uniformly, layer on layer,
over the whole disc-surface.^ From this point of view,
then, the use of the discs is as safe as it is convenient.
Whether we may argue from the results obtained with the
discs to the results obtainable with other forms of stimulus,
— whether, more especially, we may argue from the disc-
colours to the pure lights of the spectrum, — is a question
which experiment must decide. We return to it presently.
The facts to be considered in this section may be
grouped under three laws, which are known as the laws of
colour mixture. The first law states (i) that for every
colour there mav be found another, antagonistic or com-
plementary colour, which if mixed with it in the right pro-
portions produces a sensation of light, and if mixed in any
other proportions a colour sensation, of low degree of
chroma and of the hue of the stronger component. An-
1 This law, called Talbot's law, was first propounded in 1834 by the ph}-si-
cist W. H. F. Talbot, one of the inventors of photography ( The London and
Edinburgh Philosophical Magazine and Journal of Science, series 3, v..
32S ff.).
§17. The Laws of Colour Mixture
69
tagonistic colours, in this sense, are carmine and bluish
green, red and verdigris, orange and greenish blue, yellow
and blue, yellowish green and violet, green and purple.
The second law states (2) that the mixture of any two
jolours which are not antagonistic produces a colour sen-
sation of intermediate hue ; this hue varies with the rela-
tive amounts of the two component colours, and the chroma
varies with their nearness or remoteness in the colour
series. Thus, a mixture of R and B will give violet, purple
or carmine, according to the amounts taken ; and the
Fig. 4. Demonstrational Colour Mixer, for six sets of discs.
mixture of R and Y will give an O of relatively low, that
oiRO and (9 Fan O oi relatively high chroma.
These two laws are, evidently, laws of the same order;
they sum up observations of the same general kind. The
third law takes us a step farther and shows the effect of
mixing, not single colours, but colour mixtures. It is
sometimes termed Newton's law of colour mixture, since
it is implicit in his theory of the composition of light. -^
We may formulate it as follows: (3) if two colour mix-
tures arouse the same sensation of light or colour, then a
mixture of these mixtures will also arouse that sensation.
If, for instance, the grey produced by a mixture of car-
^ I. Newton, Opticks: or, A IVeattse of the Reflections, Refractions, InJleC'
tions and Colours of Li^ht, [1704] bk. i., pt. ii., props. 4-6.
70 The Quality of Sensation : Vision
mine and bluish green is the same as that produced by a
mixture of red and verdigris, then this grey will also re-
sult from the mixture, in the original proportions, of all
four colours. — This third law enables us to answer in the
affirmative the question, raised above, whether it is legiti-
mate to argue from our disc-colours to other forms of
visual stimulus, and especially to the pure Hghts of the
spectrum.
The answer is reached by way of the corollary that any unsat.
urated colour may be produced by mixture of a saturated colour
with grey. The disc-colours are relatively unsaturated colours ;
they are compounded, physically, of a number of different colours,
with some one colour (or some small group of neighbouring
colours) in the ascendant. Now the first law declares that the
mixture of complementaries produces grey. By the third law,
which asserts that all colour mixtures have a constant mixing
value, any grey whatsoever may be considered as the result of
mixture, in the right proportions, of some pair.r, ji'of complemen-
tary colours. If J is present in excess, then by the first law we
obtain a colour sensation of low chroma and of the hue oi y itself.
Hence all that we have to do, in order to produce a particular
unsaturated colour, is to search among the saturated colours for
the fitting y, and, having found it, to add a certain amount of
grey. This means, however, that our disc-colours may be regarded
as spectral colours mixed with various amounts of white light, and
therefore that our demonstration of the three laws holds for the
spectrum as well as for coloured papers.
There are other important corollaries to these laws. Thus, it
follows from the first and second, taken together, that the mix-
ture of three colours, every pair of which embraces the complemen-
tary of the third, will give colour sensations of every possible hue,
and of all possible degrees of chroma from a certain maximum to
zero. Take, for example, R, G and V. The mixture of R and
G will, by the second law, give any hue from the (9, Y and YG
regions ; the mixture of G and Fwill give BG and B ; the mbi-
§17- The Laivs of Colour Mixture yi
ture of F and J? will give P and C. Further, the complementary
of Flies between i? and G ; that ofi? between 6^ and F; and that
of G between Fand i?. Hence, by a fittingly proportioned mix-
ture of these three colours, it is possible to obtain a colour sensation
of any required hue, and of any degree of chroma that is lower'than
that of the components. Similar triads of colours are J?, V, GB ;
O, G, V \ P, YG, BG; etc. — This is a useful corollary to us,
since it is seldom that the disc-colours are exactly complementary.
Hence, to demonstrate the complementarism of C and BG,y/e
take three coloured papers, C, B and G, and vary the propor-
tions of the sectors until we find 3.BG that is antagonistic to the
given C ; and so on with other complementary pairs.
It follows, again, from the third law, as we have formulated it
above, that colour-equations are independent of the energy of the
physical stimulus. Suppose, for instance, that we have matched a
grey derived from C and BG to a grey derived from^ and Y. Now
assume that the energy of these greys is doubled or tripled. This
is the same thing as assuming that we have made the match two
or three times over, and then added the greys together, mixed each
grey once or twice with itself. The resulting double or triple
greys ought, by the law, to match as well as the original, single
greys. Here, however, we may come into conflict with the Pur-
kinje phenomenon. If the equation is first made for a low degree
of Hght-energy, and this energy is then considerably increased, the
^- y grey will evidently appear lighter than the C-BG grey. If,
contrariwise, the equation is first made for a moderately high de-
gree of light-energy, and the energy is then greatly diminished, the
C-BG gxty must appear lighter than the B- Y grey. And for certain,
shifts of energy the change of tint will be accompanied by a change
of hue. Neither this corollary, therefore, nor the third law itself,
in so far as it involves the corollary, can be regarded as valid under
all conditions.
§ 1 8. The Dependence of Visual Sensation upon the Time
and Space Relations of Stimulus. — The quality of visual sen-
sation is dependent not only upon the wave-length, wave-
72 The Quality of Sensatiojt: Vision
amplitude and wave-form of light, but also upon the time
during which the waves affect the eye and upon their dis-
tribution in space. Under the former heading, we have to
consider the facts of adaptation and of negative after-images;
under the latter, the facts of light and colour contrast. —
When the lamps are first Hghted in the evening, we
clearly realise that the illumination is not white but
reddish-yellow. As time goes on, however, this colour dis-
appears, and the objects about us look as they would look
in a really white light. In ordinary language, we have
grown accustomed to the artificial light; in technical terms,
adaptation has set in. The law of adaptation is that all sen-
sations of colour tend towards neutrality, and all sensa-
tions of light towards a middle grey. Adaptation may be
either general, extending over the whole field of vision,
or local, extending over some part of the field to which
our gaze is constantly directed.
The course of general adaptation to colour may be followed by
help of an optician's trial frame and a set of coloured glasses. If,
for instance, you wear a pair of yellow glasses even for five min-
utes, you will find that adaptation has gone surprisingly far.
Adaptation to dark and light is never so complete as adaptation
to colour : the grey that you see after waking from sleep in a dark
room and the grey that you see out of doors on a dull winter's day
when the ground is covered with snow are distinctly different, the
one lying on the black and the other on the white side of the
middle grey. Nevertheless, there is a definite approach to this
grey ; after you have worn ' black ' glasses for a few hours, it is
difficult to believe that the world looks darker than it did before
you put them on.
Local adaptation may be demonstrated by the apparatus shown
in Fig. 5. Gaze steadily, say for i min., at the button which lies
at the centre of the line of junction of black and white. You soon
§ 1 8. TJie Laiv of Adaptation
n
see grey films or clouds, which appear first along this line and
gradually spread, to right and left, over the whole surface. On
the black, the cloud is dark and slowly lightens ; on the white, it
is light and slowly darkens. Both
clouds are strongest at the centre,
weaker towards the periphery.
(The fines of brilliant white and
intense black, that flash out from
time to time, are irrelevant to
the present observation ; they are
due to involuntary slips of fixa-
tion.) — The black and the white
are, evidently, tending both alike
towards a middle grey. Indeed,
if the gaze is maintained for a suffi-
cient length of time, their differ-
ence disappears, and the entire
surface is seen as a uniform grey.
Similar tests may be made with
colours. Fig. 5. Adaptation Frame.
It is plain that this law of adaptation may be brought
into relation with the laws of colour mixture. To say
that, under adaptation, all sensations of colour tend
towards neutrality is equivalent to saying that, as time
goes on, every colour in the field of vision is mixed with
an increasing amount of its antagonistic colour. To say
that, under adaptation, all sensations of light tend towards
a middle grey is equivalent to saying that, as time goes
on, the blacks in the field of vision are mixed with in-
creasing amounts of white, and the whites with increasing
amounts of black. Adaptation to colour suggests the first,
adaptation to light suggests the second law of colour
mixture.
Let us turn, now, to the after-effects of adaptation.
74 The Quality of Sejisation : Vision
When you come out into the daylight from a matinee
performance, everything looks curiously bluish ; when
you pass from daylight into a darkened room, everything
is oppressively black. Very soon, of course, the blue
wears off and the black clears up ; a novel adaptation is
in progress. But the immediate after-effect of general
adaptation is always this contrary trend of vision : if you
were yellow-adapted, you are now blue-sighted ; if green-
adapted, now purple-sighted; if dark-adapted, now light-
si£;hted.
The same thing holds of local adaptation. If, by steady
fixation, you have brought a patch of colour to disappear-
ance, and the colour stimulus is then removed, you see in
place of it a patch of the antagonistic colour, a negative
after-image. A yellow stimulus gives a blue after-image ;
a green stimulus, a purple after-image ; a black stimulus, a
white after-image.
The after-effect of general adaptation may be demonstrated with
the coloured spectacles. When, for instance, the yellow glasses
are taken off, all the blues in the field of vision look extremely
saturated, all the yellows look whitish, and the other colours ap
pear as if mixed with blue.
To demonstrate the negative after-image, we may continue the
observation made with the adaptation screen (Fig. 5). If, at the
end of the i min., the half-black and half-white card is allowed to
fall, and there is shown in its place a background of uniform grey,
the observers will see an intense black where they previously saw
white, and a brilliant white where they previously saw black.
(The black and white lines, spoken of above, owe their depth and
brilliancy to the fact that, as fixation slips, the white edge falls
upon a black-adapted part of the retina, and conversely : the
white is thus seen with a white-sighted eye, and the black with
a black-sighted eye.) After-images of colour may be demon-
§ 1 8. The Negative After-image
75
strated by the apparatus shown in Fig. 6. A disc of coloured
glass is fixated, say, for 30 sec. Then a grey screen is dropped
between glass and lamp,
and the after-image de-
velopes, in the antagonistic
colour, upon this screen.
It is a little puzzling
that, in all these phe-
nomena of adaptation,
black and white should
behave, in the sphere of
sensations of light, as
complementary colours
behave in the sphere
of sensations of colour.
We saw in § 14 that
the series of light sen-
sations, white-grey-
black, resembles the
R- V, Y-G, G-B and B-R
series of colour sen-
sations; and we have just said that the course of adap-
tation to light suggests, in consequence, the second law
of colour mixture. But F-adaptation does not leave us
C-sighted, nor does T^-adaptation leave us F-sighted or
^-sighted : why, then, should white-adaptation leave us
black-sighted, and conversely? We seek to answer this
question, and so to bring all the facts of adaptation
under a single principle, in § 22. In the meantime, we
notice that, in the domain of contrast, black and white
again appear in the same antagonistic or complementary
relation. —
Fig. 6. Wundt's Apparatus for the Observa-
tion of Negative After-images.
76
TJie Quality of Sensation: Vision
Contrast is the name given to the effects produced for
sensation by the distribution of visual stimuli in space.
Every patch of light and colour in the field of vision
affects and is affected by all the rest in certain definite
ways. The principal laws of contrast — that is, of this
reciprocal induction of lights and colours — are as follows,
(i) The contrast-effect is always in the direction of great-
est opposition; a yellow makes its surroundings bluish, a
black makes its surroundings light. (2) The nearer to-
FlG. 7. Contrast Frame.
gether the contrasting surfaces, the greater is the contrast-
effect. We may therefore distinguish between marginal
contrast, in which the effect is maximal, and surface con-
trast, in which it is less marked. (3) The contrast-effect
is enhanced by the elimination of contours or boundary-
lines, — There are two further laws of colour contrast:
(4) that the effect is greatest when there is no simultane-
ous light contrast; and (5) that the effect increases with
increase of the saturation of the inducing colour.
A general idea of the phenomena of contrast may be gained
from the contrast frame, shown in Fig. 7. The frame contains
four sheets of coloured paper, — R, G, F and B. Across the
centre of these sheets is laid a horizontal strip of neutral grey
paper. Each panel is faced with white tissue, which serves to
§ i8. The Lazvs of Contrast
77
bring colour and grey into the same plane, and also to obscure
the outline of the grey strip. Under these conditions the grey
appears in four different colours, which are complementary to the
colours of the sheets, and whose tint varies inversely with the tint
of the coloured background. The strip is so narrow that mar-
ginal contrast is secured over its whole width.
Very beautiful contrast-effects may be obtained with coloured
shadows. Fig. 8 shows two window-slits cut in the wall of a dark
room, the one filled with a blue, the other with an ordinary ground
glass. A black rod, standing on a table, casts two shadows upon
Fig. 8.
a white screen. The farther shadow, due to the white light from
the nearer slit, is illuminated by the blue light, and therefore
appears blue. The nearer shadow, due to the blue light from the
farther slit, is illuminated by the white light, and should therefore,
in terms of its physical stimulus, appear hght grey. In reality, it
appears, by contrast, in the yellow complementary to the blue
of its neighbour. — The rod should be moved to and fro, until the
shadows are exactly juxtaposed ; their lack of definite contour,
their narrowness, and their identity of plane, all serve to enhance
the contrast-effect. It is, indeed, easily possible, by varying the
widths of the window-slits, to give the yellow a higher degree
of chroma than is possessed by the blue shadow, so that a naive
observer would unhesitatingly declare the blue to be the contrast.
^8 The Quality of Sensation : Vision
and the yellow the ' real ' colour. The bluish tinge of the back-
ground shows, of course, that the yellow colour is due to contrast.
• — Other coloured glasses may be substituted for the blue, with
similar results.
It is clear, from all these facts, that the lights and
colours of the field of vision, at any given moment, are not
exclusively determined by the physical stimuli, the reflected
light-waves, which affect the eye. What we see depends,
in part, upon contrast ; in part, also, upon the preceding
adaptation of the eye, general and local. It is clear, fur-
ther, that contrast and adaptation are in one sense op-
posed, but in another sense mutually supplementary
principles. Contrast is present, throughout the field of
vision, as soon as we open our eyes ; adaptation requires
time. Contrast is a differentiating, adaptation a levelling
principle. Hence contrast helps us to discriminate all the
separate objects by which we are surrounded, while adap-
tation prevents our being fatigued or disturbed by their
variety after this discrimination has taken place.
§ 19. Daylight and Twilight Vision. — The human eye
is a single sense-organ, and all its sensations are of one
general kind. But it is also an extremely elaborate organ,
the final product of a long course of development and
differentiation. We must, therefore, consider visual sen-
sation not only in its dependence upon external stimulus,
but also in its dependence upon differences of structure
and function within the eye. We shall not, in this way,
discover any new sense-qualities ; but we shall bring the
sensations of light and colour into a novel perspective, and
shall thus find uniformities which will help us, later on,
towards their physiological explanation.
§ 19- Daylight a7id TiviligJit Vision 79
The facts of which we have to take account are, first,
those of daylight and twilight vision ; and, secondly, those
of direct and indirect vision and of colour blindness. The
former have already been touched upon, incidentally, in
references to the Purkinje phenomenon.
It is, indeed, a curious thing that our sight undergoes a
radical transformation as we pass from the light to the
dark and back again. So long as the energy of the light-
waves that strike the eye is maintained above a certain
limit, we have dayhght vision. We see the spectrum as a
band of colours, with yellow as the lightest tint ; we have
all degrees of light sensation, from white to black ; in a
word, our vision is the vision that is summed up in the
colour pyramid. When, on the other hand, the energy
of the Hght-waves falls below this limit, we have twihght
vision : the spectrum is seen as a band of greys, the
lightest of which lies in the region occupied in daylight
by the green, and sensations of colour are altogether
lacking. Under certain conditions, the two modes of
vision overlap. Twilight vision is greatly enhanced by
adaptation of the eye to dark ; so that, if there is sufficient
light for us to distinguish colours, while at the same time
the eye is partially dark-adapted, we see the Purkinje phe-
nomenon superposed upon daylight vision. On the other
hand, this overlapping is not possible over the whole
extent of the retina. At the very centre of the eye, there
is no twihght vision, and the Purkinje phenomenon does
not appear. So far, then, the two modes of vision are
locally separated : while the eye in general is composed,
so to say, of two eyes, a nyctalopic and an hemeralopic, a
small area in the middle of the retina is permanently
hemeralopic.
8o The Quality of Sensation : Vision
We said in § i6 that the Purkinje phenomenon might be ob-
served by looking at red and blue papers through a pinhole in a
card. It may also be observed by looking at the colours through
nearly closed eyelids, or by taking them from a light into a dark
room. In all three cases, since the colours are still visible, there
is a mixture of daylight and twilight vision ; that is to say, the
phenomenon does not appear at once, but only after a little while,
when dark-adaptation has gone a certain distance. A similar
mixture of the two types of vision occurs as you watch the reds
and blues of the carpet in a deepening twilight. If, on the other
hand, you go straight from bright daylight into a perfectly dark
room, in which is exposed a spectrum of such low energy that no
colour can be seen, then, as soon as you are able to observe at all,
you observe that this spectrum shows the Purkinje plienomenon.
Twilight vision is primarily dependent, not upon dark-adaptation,
but upon the reduction of the energy of light. What dark-adap-
tation does is to make the greys of twilight vision much clearer
and stronger than they are without it.
The absence of the Purkinje phenomenon at the centre of the
retina can be demonstrated only by aid of refined physical instru-
ments. It is, however, easy to convince oneself that this central
area, which in daylight is preferred for all the most delicate uses
of vision, is not stimulable by light-waves below a certain limit of
energy. Look directly, on some dark night, at a faint star or
a distant lamp that is just visible as the eye travels over the field
of vision, and the point of light disappears. Shift your gaze ever
so little from this direct fixation, and it flashes out again.
We can now understand the exceptions to the third law of
colour mixture, mentioned in §17. Colour equations made in day-
light vision will hold in daylight vision : they cease to hold when
we exchange this for twilight vision, or when in consequence of
dark-adaptation twilight encroaches upon daylight vision.
§ 20. Indirect Vision and Colour Blindness. — Under ordi-
nary circumstances, we pay but little attention to the
outlying parts of the field of vision. What we want to
§ 20. Indirect Vision and Colour Blindness 8 1
see, we look at, and so bring upon the centre of the retina ;
and we take it for granted that the visible objects which
lie far out in the field, round about this region of direct
regard, retain the colours which they show when we turn
the eye upon them. Nevertheless, the colour vision of the
peripheral retina is very different from that of the centre.
Fig. 9. Perimeter for Mapping the Retinal Zones.
Suppose that the left eye is shaded, and that the right
gazes steadily at some fixation-mark placed directly before
it, or a little to the right. Suppose, further, that a small
red object is moved into the field of vision from the nasal
side, so that its image falls upon the temporal half of the
right retina. The object first becomes visible as a patch
of black ; then it shows as B or Y\ then, as it advances,
it looks P ox O \ finally, as it approaches the fixation-point,
82 The Quality of Sensation : Vision
it appears in its true colour, as a carmine or vermilion.
Other colours give like results ; so that we are finally led
to the conclusion that the retina consists of three dis-
tinct zones. The outermost zone is totally colour blind,
and accordingly furnishes only sensations of light, what-
ever the stimulus may be. The intermediate zone is
partially colour blind and furnishes, besides the sensa-
tions of light, only sensations of B and Y, in all tints and
in all degrees of chroma. The middlemost or central area
furnishes all the sense-qualities that are represented in the
colour pyramid.
We have called the three zones distinct, and it is true that
they may be distinguished in any experiment such as that just
described. At the same time, as the P ox O phase of the ob-
servation shows, they are not sharply separated, but pass gradually
into one another. Hence a red object of large area will still be
seen as R where a smaller object would appear as P or O, and
will still be seen as coloured where a smaller object would look
dark grey or black. Similarly, a stimulus of high energy and brief
duration will retain its colour farther from the centre than a
stimulus of low energy and longer duration. It is, therefore, im-
possible to map the retinal zones in any hard and fast way. They
are regions of relatively, not absolutely different colour sensitivity.
Indeed, if the energy of the stimuli were made exceedingly great,
it is probable that they would be seen in their true colours over
the whole extent of the retina. Under the usual conditions of
stimulation, however, the zones are distinct.
A red stimulus, as it travels out from the centre, changes first
to P or O, and then to B or Y, only because it is not a physio-
logically pure red. If we can find a red stimulus that has no B or
F effect, then the red will change to black or grey as soon as it
leaves the middlemost zone. This red has, as a matter of fact,
been determined; it is not a spectral red or vermilion, but a
slightly purplish or carmine red. What holds of it holds also of
§ 20. Indirect Vision and Colour Blindness 83
its complementary, a spectral hue of about 495 /a/a ; this, too,
passes directly into grey as it leaves the middlemost zone. If
these two colours are equated as regards area, tint and chroma,
they become colourless at the same distance from the centre of
the retina, so that the zone of red-vision is coextensive with the
zone of green-vision. The same thing is true of a j5 of about
470 /A/A and a F of about 575 /a/a: the zone of ^-vision is co-
extensive with that of Kvision. The retina thus appears as made
up of an outermost Bk- W zone, an intermediate Bk- W-\- B- V,
and an innermost Bk- lV-{- B- Y-\- R-G zone.
If a spectrum is thrown upon the Bk- W zone, it appears, of
course, as a band of greys. It is noteworthy that, in light-adapta-
tion, the lightest of these greys occupies the region of the yellow,
so that the relative distribution of tint in the colourless spectrum
is unchanged. —
Most of us use our eyes for a lifetime, without discovering these
differences of zonal sensitivity. The reason is that, in indirect
vision, it is very difficult to make out the form, size or contour of
objects in the visual field. This sort of discrimination is, however,
of great importance for the organism. Hence we habitually turn
our eyes toward that which we wish to observe; attention goes
with direct vision, and the phenomena of indirect vision are
disregarded.
We must say, then, that the normal eye is normal only
for purposes of direct vision, while in indirect vision it is
partially or totally colour blind. There is also an abnormal
colour blindness ; certain persons show these defects of vis-
ion over the whole extent of the retina. Thus, some 3 per
cent, of the male population are, from birth, partially colour
blind; their eyes lack the middlemost or R-G zone. The
physiologically pure red and the physiologically pure
green, of about 495 /a/x, appear to them as grey ; the left
or long-wave end of the spectrum is yellow, and the right
or short-wave end is blue. In other words, the spectrum
84
The Quality of Sensation : Vision
looks in airect vision as it normally looks in indirect vision
with the Y-B zone, or as it normally looks in direct vision
when the energy of the light-waves is very great (§ 16);
and the whole visual world consists of blacks, whites and
greys, together with blues and yellows in all possible variety
of tint and chroma.
It follows from this that partially colour blind persons will con-
fuse a pure red and a pure green, if tint and chroma are the same.
They will also, under
these conditions, con-
fuse O and YG, P
and BG, rose and
blue, vermilion and
brown. In everyday
life they make very
few mistakes, partly
because they have
learned the names of
coloured objects from
their normal-sighted
acquaintances, partly
because objects of
the CO nfu sable col-
ours usually differ in
tint or chroma or
both, as well as in
hue, and in certain
cases because difference of hue is connected with a difference of
grain or texture.'
1 This, no doubt, explains the otherwise curious fact that only in compara-
tively recent times has partial colour blindness attracted any widespread atten-
tion. Scattered references to it go back to the seventeenth century; but it
did not obtain general recognition from scientific men until 1798, when the
chemist John Dalton published a paper on Extraordinary Facts relating to the
Vision of Colours {^Edinbui-gh Journal of Science, ix., 97 ). Dalton was him-
self partially colour blind, and for some time the defect was known as Dalton'
Fig. 10. Hering's Apparatus for the Investigation
of Partial Colour Blindness.
§ 21. The Prhnary Colours 85
There are two types of partial colour blindness. In the first
and commoner form, the distribution of tints in the spectrum is
the same as in normal vision ; the lightest grey lies in the region of
yellow. In the second, the lightest grey has shifted towards the
short-wave end, and lies in the region of yellow-green. This and
certain other anomalies of congenital partial colour blindness still
await explanation. — A partial colour blindness due to lack of the
intermediate or B-Y zqwq is found only as a pathological condition
of the eyes, not as a congenital defect.
A much more serious congenital defect of vision is that
known as total colour blindness, in which the eye lacks both
the R-G and the i5-F zones, and the world of colour ap-
pears in monotone as an arrangement of blacks, whites
and greys. The defect is rare ; only some fifty cases have
been examined. The totally colour blind eye is nyctalopic ;
that is to say, its vision, in any state of adaptation, is
twilight vision, and the spectrum as seen by it always shows
the Purkinje phenomenon. Further, the small central area
which, in the normal eye, is permanently hemeralopic is in
the totally colour blind eye either wholly or almost wholly
blind, so that direct fixation of an object in the field o^
vision is impossible, and the eye twitches and jerks in the
effort after clear vision.
§ 21. The Primary Colours. — We have seen that, psy-
chologically regarded, all colours are equally simple ; it is
impossible, for instance, by introspective analysis to split
up orange into yellow and red. On the other hand, certain
colours have exceptional positions in the colour pyramid,
— those colours, namely, which lie at the four corners of
ism. Latterly the subject has been much discussed, on account of the danger
arising from the confusion of red and green signal lights by engineers, pilots,
etc.
86 The Quality of Sensation : Vision
the base, and which thus begin and end the four colour
series. These colours, R, Y, G, B, are the psychological
primaries.
For technical and artistic purposes, we must give this
title to a different set of colours : R, V and B. The
painter who has these pigments upon his palette is able by
their means, with the help of white, to reproduce the
various colours of nature.
It is a matter of common experience that the mixture of B and
y paints will give a saturated green. The reason is that the blue
pigment crystals reflect B and G light, the K crystals, Fand G
light. Thus the B and Y cancel each other, and only the G is
left to be seen.
For the physicist, again, the primary colours are R, G
and a certain B V. The mixture of these three spectral
colours, in fitting proportions, will not only give colours
of every possible hue, but will also give them at a higher
degree of saturation than can be obtained from any other
three spectral colours.
Lastly, for the physiologist, the primary colours are the
four characteristic colours of the retinal zones : a purplish
red, its complementary bluish green ot about 495 ,tt/i, and
the Y and B of the intermediate zone. The two latter
colours are identical with the psychological primaries.
Whether the physiologically pure R is identical with the
psychological R is doubtful ; but it is certain that the
physiological G is not the psychological 6^ : it is rather a
distinctly bluish G.
Evidently, then, the term primary is misleading ; what
it means depends upon the context in which it is used.
We may, perhaps, call the psychological R, G, Y, B the
principal colours ; the artist's VV^ R, Y, B the primary
§ 22. Theories of Vision 87
colours ; the physicist's R, G and B V the fundamental
colours ; and the physiological C, BG, V and B the invari-
able colours.
§ 22. Theories of Vision. — The eye^ is, in all essentials,
a little photographic camera. The eyelids form a cap or
shutter, closure of which prevents the access of light.
Behind the shutter is an automatic diaphragm, the iris,
which closes to a pin-hole or opens out, according to the
degree of illumination. Behind the diaphragm is a lens,
which may be adjusted for near or far objects. This ad-
justment is not made by changing the length of the eye-
ball, as it were by racking the lens back and forth ; the
soft substance of the lens is encased in an elastic sheath,
which is suspended by radial fibres to muscles set vertically
in the wall of the eyeball. When the eye is at rest, the
anterior surface of the lens is relatively flat, and the organ
is consequently adjusted for far vision ; if we wish to focus
upon a near object, the muscles contract, the pull on the
radial fibres is thereby lessened, and the lens assumes a
greater curvature. Behind the lens is a dark chamber,
lined with a membrane, the choroid, which is deeply pig-
mented by a colouring matter of dark brown. This chamber,
together with the smaller chamber in front of the lens, is
filled with a clear semi-fluid or fluid substance, which serves
to maintain the shape of the eyeball ; and the whole eyeball
is surrounded by a leathery protective membrane, the
sclerotic, which is pierced behind by the optic nerve and
1 Models of the brain and sense-organs are manufactured, in all degrees of
elaboration, by a number of firms : Auzoux, Benninghoven & Sommer, Bock-
Steger, Brendel, Deyrolle, etc. The writer uses, as eve-models, the CEi/ com-
plet de t}-es grande dimension, of the Auzoux series of clastic anatomy, and the
models numbered 3 b and 3 / in the Benninghoven & Sommer series.
88 The Quality of Sensation: Vision
passes over in front into the transparent cornea. The
retina, or sensitive iilm, is produced by the expansion of
the optic nerve over the posterior two-thirds of the internal
surface ; it is self -renewing, just as the diaphragm and
lens are automatic.
The retina, with which we are chiefly concerned, is a
very thin but extremely complex membrane. Its terminal
structures, which are the sensitive receivers of the physi-
cal light stimulus, are known as rods and cones. In
general, these are intermingled over the entire retina.
There are, however, two areas — the optic disc and the
yellow spot — which show a different formation. The optic
disc is the point at which the optic nerve enters the eye-
ball. Here there is no true retina, but a blind spot, whose
situation and dimensions may readily be determined by
experiment. The yellow spot or macula lutea lies at the
posterior pole of the eyeball : it is peculiarly sensitive to
form and contour, and is therefore termed also the spot of
clearest vision. At the centre, in the fovea centralis, it
shows a depression, where the retina consists of little more
than a single layer of attenuated cones. The whole spot
is coloured yellow, so that in macular vision the colours
of the short-wave end of the spectrum are somewhat
darkened. —
It is not possible, in the present state of our physiological
knowledge, to give an entirely satisfactory explanation of
all the facts of visual sensation. The following, however,
seem to be the most reasonable hypotheses.
(i) TJie Theory of Dual Vision. — Many indications
point to the conclusion that the rods are the end-organs
of twilight, the cones the end-organs of daylight vision.
That is to say, the rods are organs which, under stimulation
§ 22. TJieories of Vision 89
by light-waves whose energy is too low to stimulate the
cones, furnish us with sensations of light. The blindness
of the normal fovea at night-time is due to the fact that
the retina is there composed only of cones. The Purkinje
phenomenon, and the exceptions to the third law of colour
mixture, are to be ascribed to the rods : they mean that the
rods are affected by Hght-waves of different length other-
wise than are the cones. The typical retina of the totally
colour blind eye is a rod-retina, lacking functional cones, and
the complete blindness of the fovea is a necessary result.
We have seen that twilight vision is extremely dependent upon
dark-adaptation. It is significant, in this connection, that the
terminal members of the rods contain a purplish red substance,
the visual purple, which bleaches on exposure to light and is re-
formed under the influence of darkness. It is further significant
that the distribution of tints in the Purkinje spectrum (lightest
region in G) accords with the chemical action of the different
light-waves upon the visual purple. Whether, however, the visual
purple is essentially concerned in rod-vision, or whether it serves
merely to sensitise the visual apparatus, cannot certainly be de-
cided. The retinas of nocturnal animals — owls, bats, rats, moles — ■
are almost wholly deficient in cones, while their rods are richly
supplied with the visual purple. Animals whose eyes lack this
rod-pigment — fowls, pigeons — are strictly diurnal in their habits.
(2) The Phenomena of Daylight Vision. — There are
two current theories of daylight vision, called respectively
the Helmholtz and the Hering theory. Both are adequate
to a large proportion of the facts ; both have been variously
modified to accord with newly discovered facts ; neither fits
the facts in complete detail. Both, of course, are physio-
logical theories ; but Helmholtz approaches physiology by
way of physics, Hering rather by way of psychology. The
go The Quality of Sensation : Vision
following account agrees, in its main outlines, with Hering's
view.
We assume that the retinal cones contain three visual
substances, which are decomposable by light, and which
are the vehicles of reversible or antagonistic chemical
reactions. We may term them the black-white, the blue-
yellow, and the red-green substances. The cones of the
central area contain all three ; those of the intermediate
zone mostly contain the Bk- W^and the B- Fsubstances ; and
those of the outermost zone mostly contain only the Bk- W
substance. The latter, which is thus the most widely dis-
tributed of the visual substances, is affected by every light
stimulus which exceeds a certain lower limit of energy ; the
other two are affected only by the wave-lengths correspond-
ing to their names. The six chemical reactions which
occur in the three substances give rise to the sensations of
black, white, and the four invariable colours. From them
and their combinations are derived, with a single exception,
all the phenomena of daylight vision.
The exception is the sensation of neutral grey. Since
this sensation may persist while the retinal organs are out
of function, it must take its origin in the brain. We ascribe
it to the molecular motion of heat in the cells of the visual
cortex, and are thus able to explain both its constancy and
its qualitative character.
According to this view, the retinal processes which arouse the
sensations of Bk and W, B and Y, and invariable R and G are
antagonistic and incompatible. If, for instance, by mixing a dark
B and a light Y on the colour mixer, we expose a certain area
of the intermediate zone to light which affects the Bk- W and the
^- y substances in equal and opposite ways, no retinal sensation
will be set up by the stimulus; we ought, so to speak, to see
§ 22. Theories of Vision 9 1
nothing whatever. What we do see is a middle grey, the grey
which is to be referred to the cortex. This grey, which mixes
with all retinal sensations, is constant, because the heat-energy
of the cortex is constant ; it is grey because, unlike the sensations
of hght from the retina, it derives simultaneously from both of the
antagonistic Bk- IV reactions : — such a simultaneous occurrence
of opposed processes is, as physics tells us, precisely the effect
produced by heat within a body which is m chemical equilibrium.
The office of the cortical grey is to prevent the darker objects in
the field of vision from being drowned out by their lighter
surroundings.
The facts of indirect vision are explained by the distribution
of the visual substances over the retina. The Bk-W is, evidently,
the oldest, the R-G the youngest, of the three. Hence the R-G
is also the most instable. In cases of partial colour blindness, it
does not occur at all, while the Bk- JV and the B- V substances are
intact. If the light-waves possess a very high degree of energy, it
is thrown out of function (§16).
The facts of colour mixture may easily be worked out in terms
of the three retinal substances and the cortical grey. Take, for
instance, the fact that C and BG, mixed in the right proportions,
give grey. The stimuli affect the R-G substance in equal and
opposite ways. They also affect the Bk- W substance : perhaps
equally and oppositely, perhaps both by way of Bk or both by way
of W, perhaps differently, so that the one of these antagonistic
processes is stronger than the other. In the first case we see
simply the cortical grey ; in the second, a distinctly dark or a
distinctly light grey ; in the third, a slightly dark or somewhat
hght grey, according as the retinal excess has fallen on the side
of Bk or of W. The same sort of analysis may be carried through
for the mixture of other light stimuli, in any number and of any
wave-length.
To account for contrast, we have merely to suppose that the
retinal substances tend towards equilibrium over the whole area
of their distribution, so that, directly affected at one point, they
are indirectly — and oppositely — affected at all other points,
\hough most noticeably, of course, in the immediate neighbour-
92 The Quality of Sensation: Vision
hood of the stimulus. If we look at a red square on a grey
ground, we see at once the contrast-fringe of verdigris ; it is as
if the whole of the R- G substance were up in arms to repel the
invasion. The same thing holds of other stimuli, including Bk and
W; all alike call out, indirectly, the antagonistic retinal process.
Lastly, the phenomena of adaptation and after-image follow
from the antagonistic character of the reactions in the three sub-
stances. As we gaze at the red square, the -/^-reaction of the R G
substance is gradually reduced ; or, what is the same thing, the
6^-reaction is gradually strengthened. Presently, the two reactions
are of equal strength ; adaptation to the coloured stimulus is com-
plete, and we see grey. If, now, the red square is removed, the
6^-reaction is suddenly given the ascendancy, and shows itself in
the complementary colour of the after-image.
References for Further Reading
§§ 14-22. The dual theory of vision was first propounded by the his-
tologist M. J. S. Schulze in 1866 {Zur Anatomic und Physiologie der
Retina, in Archiv filr inikroskopische Anatomic, ii., esp. 255 f.). Its
establishment in recent years has been largely due to the work of J.
von Kries, professor of physiology in the University of Freiburg i. Br.,
who has described it in the chapters entitled Die Gesichtsonpfitidiin-
gen, in W. Nagel's Handbiich der Fliysiologic des Menschen, iii., 1905,
109 ff. Here will also be found a full statement and criticism of the
Helmholtz and Hering theories. For the Helmholtz thepry, and its
debt to Thomas Young, see H. L. F. von Helmholtz, Handbuch der
physiologischcn Opiik, 1896, esp. §§ 20, 23. The theory of E. Hering,
who is now professor of physiology in the University of Leipzig, is set
forth in Zur Lchre vom Lichtsinne, 1874, and Gntndz'itgc der Lehrevom
Lichtsinn, pts. i., ii., 1905, 1907 (not yet completed). The cortical ori-
gin of the sensation of grey was suggested by G. E. Miiller, professor
of philosophy at Gbttingen, in Zur Psychophysik der Gesichtsempfin-
dungen (ofFprinted from Zeitschrift filr Psychologic U7id Physiologie
der Sinncsorgane), 1897. — Consult also W. H. R. Rivers, Vision, in
E. A. SchUfcr'^s Text-Book of Physiology, ii., 1900, 1026; art. Vision, in
J. M. Baldwi}i''s Dictionary of Philosophy and Psychology, ii., 1902,
765 ff. ; I. M. Bentley, The Si?nplicity of Colour Tones, American
Journal of Psychology, xiv., 1903, 92; J. W. Baird, The Colour Sen-
sitivity of the Peripheral Retina, 1905.
AUDITION
§23. The Auditory Qualities. — The world of sound,
like the world of sight, is made up of two classes of sensa-
tions, the one variegated and of manifold quality, the other
sober and monotonous. These are distinguished, in ordi-
nary speech, as tones and noises. Tones, which corre-
spond to the senations of colour, are the proper material
of music ; they have a certain clarity and stability which
fit them for their place in art. Noises, which correspond
to the sensations of light, are dull and instable; if momen-
tary, they are abrupt and harsh, if continued, they are
rough and turbid. And as in vision, so in audition, the
two kinds of sensation are in some measure independ-
ent, while at the same time they are intimately related.
We are apt to think
of tones as coming from
a musical instrument,
piano or violin. Musi-
cal tones are, however,
complicated mixtures of
tones and noises (§25).
To obtain sensibly pure
tones, elementary tonal fig. h. Tuning-fork on Resonance Box, and
Glass Bottle, fitted with mouthpiece for blow-
processes, we must .^^_ ^j^^ ^.^^^ ^^ ^^^ bottle-tone may be
have recourse to Spe- raised or lowered by pouring in or letting out
cial apparatus : the
best are weakly sounding tuning-forks standing on their
resonance boxes, and weakly blown bottles. If we
93
94 Audition
work through a long series of such pure tones, we
notice, first, that they differ qualitatively as high and
low ; they show differences of pitch. These terms are,
of course, spatial in origin, and it is not altogether
easy to see how they came to be applied to tonal
quahties.^ At any rate, they are in current use, and
we understand their meaning. We notice, secondly,
that the tones differ qualitatively in what we must
call — again in spatial terms — size or diffusion. This
attribute runs, in general, parallel with the attribute of
TREBLE
Fig. 12. The Tonal Pencil, representing the sum-total of tonal qualities, as the
Colour Pyramid represents the sum-total of visual qualities. The horizontal di-
mension corresponds to the attribute of pitch, the vertical to the attribute of volume.
pitch ; but at the ends of the scale it changes more quickly,
in the middle region more slowly, than pitch, so that deep
tones appear very large and diffuse, and high tones very
small and concentrated, while the intermediate tones seem
all to be more or less of the same size.
As we have already said (§ ii), some psychologists believe that
tones have a truly spatial attribute of volume, while others think
that the low tones merely remind the hearer of large things and
the high tones of small. This second view contains, undoubtedly,
a good deal of truth. The deepest tones from the organ, for in-
stance, are not only heard, but are also felt as a thrill over the
1 The composer Berlioz remarked that, on the piano, high means right and
low means left in the horizontal plane; and that, if the violinist's hand rises,
for high tones, the cellist's drops. The whole question is discussed by G
Stumpf, Tonpsychologie, i., 1883, % \l.
§ 23- The Auditory Qualities 95
whole body ; and the size of musical instruments varies with the
height of their tones. Children call deep and high tones big and
little, old and young : evidently because the former come from
the large grown-up people, and the latter from their small play-
mates. At the same time there can be no doubt that what we
have termed diffusion and concentration is an inherent attribute
of tones ; only, we need no more regard it as really spatial than
the other attribute of height or pitch. In trying to specify the
ultimate characters of sensation, we have to take language as we
find it, and to use metaphor and analogy. We speak of colour-tone
and of colour-depth, but we do not mean that the hues sound dif-
ferently, or that we can drop a stone into them. So we shall
speak presently of tone-colour, without implying that tones are
red or green. Pitch and size stand for certain qualitative aspects
of tonal sensation, and neither can be understood literally in terms
of space. —
There seems, in the musical scale, to be a periodical recurrence
of tonal quality ; the corresponding notes of successive octaves, if
struck together, sound in unison. It has therefore been suggested
that the tonal system must be represented, not by a straight line,
but by a line which returns upon itself, a spiral line. This resem-
blance of a note to its octave is not, however, a matter of pure
sensation ; it depends upon conditions which we discuss in Pt. II.
If the finger is run in a glissando over the white keys of the piano,
the impression obtained is that of a linear series of tonal qualities.
Hence our sensations of tone may be represented by a straight
line which tapers, in three divisions, from bass to treble, being
broadest for the diffuse deep tones and narrowest for the small
and concentrated high tones.
The noises that we hear in everyday life are of two
kinds, explosive and continuative. For the former, we
have such words as crack, pop, snap ; for the latter, such
words as hiss, sputter, rumble. It seems, at first thought,
that the continuative noises might very well be regarded
as repeated explosions; a rattle or clatter, for instance, is
96 Audition
simply a quick succession of raps or shocks. This reduc
tion cannot, however, be carried through. Such noises as
the hiss of escaping steam, the soughing of wind in the
trees, the rustle of a newspaper, — complex as they cer-
tainly are, — refuse to be analysed by introspection into
series of explosions ; and in the pattering of rain, or the
sizzle of frying fat, we distinguish the rapidly recurring
taps or clicks from the steady hiss of the background.
There are, then, two types of noise sensation, the snap
and the hiss, to be set alongside of the sensations of tone.
There can be no question that sensations of tone may be had
without accompanying noise. It is much more difificult to decide
whether sensations of noise occur without accompanying tones.
In the first place, all explosive noises have a certain, more or less
definite pitch. A hand-clap sounds lower than a snap of the
fingers, the crack of a rifle lower than the spit of a revolver. This
statement holds of the simplest noises that we can produce in the
laboratory. Thus, if soap-bubbles are filled with a mixture of air
and hydrogen, and touched off with a match, the large bubbles
give a deeper pop than the small. Or if tuning-fork tones are cut
down to mere momentary puffs of sound, we hear short, dry
strokes which are deeper for the large forks than for the small.
It would seem that, in such cases, we are listening to simple,
toneless noises, — in which event we must say that these noises
show differences of pitch akin to the pitch-differences of tones,
though of a coarser kind. But there is an alternative. If a
bar of wood is dropped upon a wooden table, we hear a thud
which sounds merely noisy. If, however, we drop a series of bars,
cut to the right lengths, we hear, over and above the noise, a
series of definite tones, an air played in a certain key. The single
thud contains a true tone, but a tone of such short duration that
introspection fails at first to find it. And the same thing may be
true of the noises from the soap-bubbles and the tuning-forks. If,
again, we pass the finger-nail slowly over the ribbed binding of a
§ 24- Tonal Sensation and Wave-number 97
book, we hear a succession of plucks or taps ; but, if we move
more quickly, a distinctly tonal scroop. The pitch of the separate
taps may, then, itself have been tonal.
In the second place, it seems safe to say that no continuative
noises are known which do not contain recognisably tonal ele-
ments. The buzz of voices in a crowded room, the beat of waves
upon a beach, the scrape of a book against others as it is returned
to the shelf, the whisper of an S, the drag of matting over a floor,
art! alike contain various tones which can be singled out by the
trained ear.^ And, contrariwise, a continuative noise may be gen-
erated from a medley of tonal stimuli. If you press down, all to-
gether, an octave of notes in the bass of a piano, — better still, if
you press suddenly upon the loud pedal, without striking the key-
board, — you hear a harsh, booming or rumbling noise with but
little trace of tone.
In fine, introspection distinguishes between tones and noises ;
and, among noises, distinguishes such things as hiss, murmur, sigh,
purl, crash, rumble from such things as snap, puff, knock, clack,
roar. But we have, as yet, no means of determining with accuracy
the nature and number of the elementary noise qualities.
§ 24. The Dependence of Auditory Sensation upon Wave-
number of Sound. — Sound-waves, like light-waves, differ in
respect of wave-length, wave-amplitude or energy, and
wave-form or composition. We are not here concerned
with their energy, since this has no influence upon the
quality of auditory sensation. And we shall speak, not
of wave-length, but rather of the wave-number — the
number of complete waves in the i sec. — which is defi-
nitely correlated with it. As referred to the tones them-
selves, this is usually termed pitch-number; as referred
* Stumpf narrates that, in listening to a mountain brook, he heard a clear
and steady tone oi f^t, with neighbouring tones playing about it; further, a
clucking and gurgling, made up of momentary deeper tones; and behind all
the noisy plash which could not be analysed. Tonpsychologie, ii., 1890, 502,
H
98
Audition
1 c^
^"~ CI
■— ~ c
to the motion of sonorous bodies, it is
termed vibration-rate..
Wave-number determines the quahty, the
pitch and size, of tonal sensations. The
tones of the musical scale range between
the limits of about 40 and 4000 vs. in the
I sec. The range of audible tones is much
wider, from about 12 to about 50000 vs.
Between these extremes the trained ear can
distinguish some iiooo different tones.
Wave-number also influences the inten-
sity of tonal sensations. High tones are
intrinsically loud, and low tones intrinsi-
cally weak, — very much as, in the spec-
trum, F is a Hght and F a dark colour.
The three attributes of pitch, size and inten-
sity, in so far as intensity is dependent not on
energy but on pitch-number, constitute together
*2^^ what is known as tone-colour. High tones have
a lighter or brighter, low tones a darker or duller
Ga-S- colouring. Where we are dealing with relatively
simple tones, the introspective analysis of tone-
FiG i^ The colour is not very difficult. The single term be-
Series of Auditory comes useful, however, when we are considering
Qualities. The ^^ compound tones employed in music.
Over the greater part of the musical scale —
from the lowest tones to tones of about 3000 vs.
— two complete sound-waves suffice to arouse a
tonal sensation, while stimuli of less than two
keyboard of a
grand piano ex-
tends from the A<2,
of 27.5 vs. to the
d> of 4224 vs. The
smaller piano key-
board ranges be-
tween the C'l of 33 vs. and the a* of 3520 vs. Hehnholtz' lower limit of orchestral
music is the E\ of 41.^25 vs. (double bass) ; his higher limit, the d'^ of 4752 vs.
(piccolo flute). The organ has a range of 9 octaves: Cn (16.5 vs ) to c^ (8448
vs.). The highest note of the violin is the e^ (2640 vs.). The range of audition is,
approximately, from the G3 of 12.35 vs. to the_/"^ of 45056 vs.
§ 24- The Limits of Tonal Sensation
99
waves give rise to a snap or stroke. Physically, then, this explo-
sive noise is merely an incomplete tone. The probable character
of noise stimuli in general is discussed in the following § 25. —
The lower hmit of tonal hearing may be determined by means
of tuning-forks or of a steel lamella. Giant tuning-forks have
been constructed, which
vibrate very slowly;
the rate of vibration
may be varied by the
adjustment of sliding
weights upon the tines.
The weighted wire forks,
a specimen of which is
shown in Fig. 14, are
more manageable. The
lamella is a blade of
soft steel, clamped in
a wooden vise, and ac-
tuated by the finger ; a
scale engraved on the
blade indicates the rate
of vibration.
The upper limit may
be determined by means
of very small tuning-forks, actuated by a bow, or more easily by
means of the Galton whistle shown in Fig. 14. The whistle is
a very small stopped labial pipe, actuated by the squeeze of a
rubber bulb, and closed by a piston which is adjustable by a
micrometer screw.
The series of distinguishable auditory qualities, between the
upper and lower limits, may be worked out in part by means
of a set of weighted wire forks and of a Galton whistle. For the
middle region of the scale we may use a tonometer : a series of
delicately adjusted tuning-forks, or a series of metal tongues of
minimally different lengths thrown into vibration by a bellows. A
less expensive apparatus is the Stern variator shown in Fig. 15.
This consists essentially of a blown brass bottle, whose pitch may
Fig. 14. Weighted Wire Fork and Galton
Whistle.
100
Audition
be varied, little by little, through the introduction or withdrawal
of a piston.
§ 25. The Dependence of Auditory Sensation upon Com-
position of Sound. — The train of sound-waves which
arouses a sensation of tone is a
periodic vibration of simple har-
monic form ; the motion of the
air-particles is a simple pendular
motion. Periodic vibrations of
any other form may be analysed,
mathematically, into a series of
superposed simple harmonic vi-
brations, whose wave-numbers are
multiples of the wave-number of
the given vibration. That is to
say, the complex wave may be
regarded as made up of a group
of simple waves, whose wave-
numbers — if the wave-number of
the complex wave is taken as i
— stand in the ratios 1:2:3:4,
etc. All musical tones or, as we
may call them, compound tones
are aroused by trains of waves of
this complex kind.
The ear, unlike the eye, is an analysing organ ; and it is
therefore possible, within limits and after practice, to
single out the simple tones which together constitute the
compound tone, — to repeat in sensation the analysis
already performed by mathematics. The compound tone
then splits up into partial tones, the lowest of which is
Fig. 15. Stern's Variator.
§ 25 Timbre of Compound Tones lOI
termed the fundamental, and the rest the upper partials,
Sometimes the upper partials are distinguished as the
overtones of the fundamental : this usage is a little con-
fusing, since the second partial becomes the first overtone,
and so on. The partial tones, when thus singled out by
the attention, have the simple character of the tones pro-
duced by tuning-forks or blown bottles ; they sound, that
is, as pure tones, and do not differ with the different in-
struments from which they come.
Most of us, however, lack the training, and some lack
the ability, to resolve a compound tone into its simple
components. Under these circumstances, the tone is
itself heard as simple, but has upon it a certain colouring
or timbre, which varies with the various instruments. The
tone of the organ is full and rich, that of the trumpet is
hard and rasping, that of the clarinet is hollow and
nasal. These differences of timbre are primarily due to
the differences in the number and relative intensity of the
overtones which accompany the fundamental.
A musical instrument consists essentially of a vibrating body
— plate, rod, string — and a resonance chamber; a tuning-fork
on its resonance box offers a simple illustration. The complex-
ity of the air-waves which it sends to the ear may be variously
produced. The vibrating body may, like the piano string, be so
constituted as to vibrate in halves, thirds, quarters, etc., at the
same time that it vibrates as a whole. Or it may be forced into
complex movements by the manner in which it is actuated ; thus
the violin string vibrates as a whole, but also zigzags back and
forth as it is drawn forward by the bow and slips away again. Or,
lastly, it may vibrate as a simple pendulum, and yet not impart a
pendular movement to the air-particles ; the metal tongue, for
instance, vibrating in an opening which it almost fills, gives rise to
extremely complicated motions of the surrounding air. When
I02 Audition
all these possibilities are taken into account, it is not surprising
that even relatively pure tones should be of rare occurrence.
The timbre of the compound tone is, in the main, the unana-
lysed resultant of the tone-colours of its simple constituents.
Bearing in mind the nature of these tone-colours, we have no
difficulty in explaining the timbre of most musical instruments.
A piano tone, for instance, necessarily sounds brighter — and
therefore, to the untrained ear, higher — than a flute tone of the
same pitch, because it contains a longer series of overtones.
These are, of course, progressively higher than the fundamental ;
and high tones have a bright tone-colour. The full and rich
tones of open organ-pipes, piano and French horn are due to the
presence, at moderate intensity, of the first half-dozen partials.
The harsh and penetrating tones of trumpet, bassoon, harmonium
are due to the predominance of the higher overtones. The tone
of the clarinet contains only the odd-numbered partials. Its
nasal character must probably be ascribed to the presence of
beats (§ 26) and to the fact that the difference-tones (§ 27)
produced by the partials do not coincide with the constituent
simple tones.
If we extend the meaning of timbre to cover everything that
helps us to distinguish the tones of the diff'erent musical instru-
ments, we must further mention, in the first place, the different
noises that accompany them. The scrape of the violin, the pluck
of the banjo, the thud of the piano, the sish of the wind instru-
ments, are characteristic. So also is the manner in which the
tones enter consciousness ; the large brass instruments lumber
into hearing, the flute glides in. Other criteria are pitch, inten-
sity, variability, and mode of performance. An instrument that
moves in the r'-octave can hardly be anything else than a piccolo ;
an instrument that sounds at a certain loudness must be a trumpet.
The oboe is distinguished by a peculiar delicacy of dynamic
shading. Lastly, many instruments have peculiar features of
melody or harmony, rhythm or modulation, so that they may be
identified by the nature of their performance. We can hardly
think of flute, harp, trumpet, without at the same time thinking
§ 26. Beats and Intermediate Tones 103
of the special way in which they are played, or the special use to
which they are put in orchestral music. —
It is sometimes said that tonal stimuli are periodic, noise stim-
uli aperiodic movements of the air-particles. But, on the one
hand, aperiodic vibrations may produce tonal sensations, as in the
* rising tone ' of the siren ; and, on the other, a periodic vibration
of short duration or a mixed medley of periodic vibrations may,
as we have seen, produce noise. The air-shock ordinarily caused
by an explosion is probably a periodic system of many, slightly
different wave-numbers and of rapidly decreasing intensity ; so
that, from the physical point of view, the crack or roar is a mix-
ture of incomplete compound tones. In the same way, the
continuative noise is probably due to a very large number of vibra-
tions, differing relatively Httle in periodicity but widely in dura-
tion. Physically, that is, the hiss must be regarded as a mixture of
compound tones, both complete and incomplete. This physi-
cal likeness of noise and tone stimuli, which enables them to act
upon the same sense organ in much the same way, accounts for
the introspective difficulty of distinguishing the tonal and the
noisy elements in many instances of auditory sensation.
§ 26. Beats and Intermediate Tones. — Tones are in-
trinsically harmonious, as colours are intrinsically antago-
nistic. It is this character of tonal sensations which, as we
shall see later, has determined the choice of notes in the
musical scale and the development of music as melody and
harmony. In the meantime, we must take account of two
sensory phenomena which result from the blending of
tones : the production of beats and intermediate tones, and
the production of what are called combinational tones. —
If two tones of precisely the same pitch-number are
heard at the same time, the resulting sensation differs
from its constituents merely in the attribute of intensity.
When the trains of air-waves are so timed that crest coin-
I04 Audition
cides with crest and valley with valley, it is stronger than
the single tone ; when the crests of the one train overlap
the valleys of the other, it is weaker.
If, now, the one of the two simultaneously sounding
tones is mistuned, so that its pitch-number is somewhat
raised or lowered, the resulting tone is no longer smooth
and continuous, but shows rhythmical fluctuations of in-
tensity, which are known as beats. So long as the mis-
tuning is slight, the beats are slow ; the tone surges up to
its maximal intensity and gradually subsides again. With
increasing difference of the generating tones, the beats
become quicker and quicker. At the same time they
grow harder and less billowy, so that they may be com-
pared to the rattle of a kettle-drum, or even to a rapid
succession of hammer-strokes upon an anvil. As the
pitch-numbers diverge still further, the separate beats give
place to an unanalysable roughness, harshness or hoarse-
ness, which with yet wider separation of the generators
finally disappears.
The number of beats produced in the i sec. is always equal to
the difference between the pitch-numbers of the generating tones.
For suppose that we are listening to tones of loo and loi vs., and
that the two trains of air-waves start in the same phase. At the
end of the first half-second, the tone of loi vs. will be exactly
half a vibration in advance of the tone of loo vs. : crest will
coincide with valley, and the resulting tone will be weakened.
At the end of the second half-second, the tone of loi vs. will be
exactly one complete vibration in advance of the other : crest will
coincide with crest, and the resulting tone will be strengthened.
We hear, therefore, one beat, one intensive fluctuation, in the i
sec. j and loi — loo = i. The same rule will evidently hold for
any other pair of generating tones.
Beats are easily distinguished and counted when they occur at
§ 26. Beats and Intermediate Tones 105
the rate of 3 or 4 in the i sec. They may be followed, by a
practised ear, from a lower limit of i in 180 sec. to an upper limit
of some 20 or 30 in the i sec. At this point, hov/ever, the com-
plex is already becoming rough. The impression of roughness or
harshness is more pronounced and more persistent in the high
than in the low regions of the tonal scale. Thus, the tones CG,
Gc, ce, eg, c^d^, d^e^, b^C' produce, all alike, 33 beats in the i sec. ;
but the roughness is increasingly marked as the pitch- numbers
grow larger. Similarly, the transition from harshness to smooth-
ness occurs in the great octave at about 40, in the four-accentec
octave only at about 400 beats in the i sec.
The surging beats which proceed from a very slight
difference of pitch-number are heard as fluctuations of a
single tone, whose pitch is indistinguishable from that of
the generators. As the difference increases, the single
beating tone may be recognised as an intermediate tone,
which at first lies near the lower generator, and gradually
rises in pitch until it approaches the upper. With a cer-
tain amount of difference (in the once-accented octave, a
difference of the musical interval of the major second), the
two generating tones may be heard alongside of the inter-
mediate tone. The upper generator now appears, with
occasional intermissions, as a smooth and continuous tone:
the intermediate tone, which carries the beats, begins to
take on a noisy character: the lower generator, whose
identity is somewhat obscured by the presence of differ-
ence-tones (§ 27), is less stable than the upper, but seems
in general to have little or no share in the production of
the beats. Finally, after this stage has been passed, the
intermediate beating tone loses its tonality, and we hear
the two generators as separate tones, accompanied by a
continuative noise, — the harshness or roughness mei>
tioned above.
I06 Audition
The gross phenomena of beats may readily be demonstrated by
means of tuning-forks, blown bottles, etc. To distinguish the
generators above and below the beating intermediate tone is,
however, by no means easy, and requires special practice. This
intermediate tone, it may be remarked, is of physical origin ^
under certain conditions, the superposition of two pendular vibra-
tions of nearly the same wave-number gives rise to a resultant
vibration of intermediate wave-number.^
If compound tones are sounded together, beats may arise
between their overtones. Under certain circumstances, the over-
tones of a single compound tone may also beat with one another.
Thus, in the case of the C of the harmonium, the partial tones
from the seventh (^^) onwards are sufficiently near and sufficiently
strong to produce sensible beats.
§ 27. Combinational Tones. — If we sound together tv^^o
precisely similar tones from the upper region of the tonal
scale, and slowly mistune the one without changing the
other, we shall hear, according to the statements of the
previous section, first a single smooth tone, then a surging,
and presently a hammering tone. When the beats have
reached a frequency of some 30 in the i sec, we hear an
entirely new, very deep tone, whose pitch-number corre-
sponds to the difference between the pitch-numbers of the
two generators. If we term the upper generating tone //,
and the lower /, we hear, in general, a third tone whose
pitch-number is it — /. This is known as the first differ-
ence tone, D^. Under favourable circumstances, a single
pair of tones will give rise to no less than five difference
tones, whose pitch-numbers correspond to the successive
differences between the pitch-numbers of the lowest tones
present in the complex. Thus, let u be a tone of 1328 and
/a tone of 1024 vs. {c^). Then we have
* Rayleigh, The Theory 0/ Sound, i., 1894, 49, 71; ii., 1896, 443, 450.
§ 27- Combinational Tones
107
Z?i= n— /= 304
Z)^ = I— Dy=2l — U= 720
D^ = D^ — D^ = ll — 2u = 416
Z>4 = i?3 — Z^i = 4 / — 3 7^ = 1 1 2
Z?5 = i?i - Z>4 = 4 2^ - 5 / = 192
all of which may be rendered audible to the practised ear.
Difference tones may be demonstrated by means of high forks,
Galton whistles, Quincke tubes, a double bicycle whistle, etc. To
hear them, one must neglect
the high tones of the instru-
ments, and listen for some-
thing lower and larger.
Sometimes the difference
tone seems to be diffused
through the room, like
the humming of a top ;
sometimes it seems to be a
very striking demonstration
Fig. 16. Set of Quincke Tubes.
deep booming within the ear. A
may be given with two Galton
whistles, the one of stationary and the other of varying pitch.
Since a difference of a certain number of vs. means a much wider
interval in the region of the difference tone than in that of the
generators, a slight change of the whistle will produce a pro-
nounced change in the difference tone, which accordingly sounds
as the howling of the wind, or as the tone of a fog-siren. — To
hear the whole series of difference tones requires special training.
The difference tone, unlike the intermediate tone of the preced-
ing section, cannot be obtained by the superposition of pendular
vibrations. It must, therefore, if it exists outside the ear at all,
be set up by some secondary vibration of the sonorous body.
Objective difference tones are, as a matter of fact, generated by
instruments, hke the harmonium, in which the two primary tones
are produced by the same air-blast, and by certain forms of vibrat-
ing membranes. The great majority of difference tones are.
however, subjective, — ear tones and not air tones. They are
occasioned by the mechanism of the ear itself.
io8
Atidition
It is noteworthy that difference tones behave, in tonal complexes,
precisely as their generators. A difference tone, that is, may beat
with another difference tone
or with a generating tone ;
and two difference tones,
or a difference tone and a
generating tone, may give
rise to an intermediate
tone and to new difference
tones. So far as hearing is
concerned, the difference
tones are on an equality
with the tones aroused by
air-waves.
Difference tones have
been known to science
since the middle of the
eighteenth century. In
1856, Helmholtz an-
nounced the discov-
ery of another kind of
combinational tone,
which he named the
summation tone ; its
pitch-number is z/-f /, the sum of the pitch-numbers of the
two generators. The summation tone is faint, and diffi-
cult to distinguish ; indeed, many investigators have ques-
tioned its existence. Recent observations seem, however,
to leave little doubt that Helmholtz' statement is correct.
It has been suggested, in particular, that the summation tone is
simply a difference tone of a higher order, generated by the first
overtone of u and the first difference tone; for 211 — D 1 = 2 u —
iu—i) = u-'fl. As, however, an objective summation tone is
Fig. 17. R. Koenig's Apparatus for the Dem-
onstration of Difference Tones. — Quel-
ques Experiences d'Acoustique, 1882, 165.
§ 28. Theory of Audition 109
produced and produced only by those instruments which produce
objective difference tones, it is clear that the physical conditions
for the arousal of the two kinds of combinational tones are the same.
And as the ear has shown itself able to originate difference tones, we
may naturally suppose that it can also originate the summation
tone. Moreover, the presence of the summation tone has been
recorded under circumstances which seem to preclude the possi-
bility of its generation by an overtone. Owing to its faintness, it is
much less important, psychologically, than are the difference tones.
§28. Theory of Audition. — Sound-waves are received
into the outer ear-passage, and impinge upon the tympanic
membrane or drum-skin, which forms the boundary between
the external and the middle ear.^ The vibrations of this
membrane are transmitted by the auditory ossicles, with
diminished amplitude of excursion but increased energy,
to the oval window. Here they are transferred to the
lymph with which the internal ear is filled.
The cochlea of the internal ear, with which, as the end-
organ of hearing, we are here concerned, is a structure of
great complexity. If we unroll it, we have a long inelastic
tube, filled with water ; both ends are closed, but the one
end contains two windows, filled with elastic membranes,
— the oval window above and the round window below.
Between the windows lies a horizontal shelf or partition,
which divides the tube into an upper and a lower half, and
1 The author uses, as ear-models, the Auzoux Oreille de ires grande
dimension ; the model numbered 4 ;^ in the Benninghoven & Sommer series;
a pair of very large models of the internal ear, from the Bock-Steger series
(these seem not to have been advertised of late years, but are probably still
procurable; they are excellent for purposes of demonstration); and Helm-
holtz' model of the middle ear. Natural preparations of the temporal bone,
and casts of these preparations (with enlarged models of the ossicles), may
also be obtained. The Ludwig or Merk model of the organ of Corti is useful
for a detailed demonstration.
no Audition
which extends throughout almost its whole length. The
partition, which we may conceive of as a long narrow
rectangle, consists partly of bone and partly of membrane.
The bone is widest at the windows and narrowest at the
far end of the cochlea ; the membrane forms a triangle
with its apex at the windows. This triangular membrane,
known as the basilar membrane, carries the hair-cells with
which the fibres of the auditory nerve are connected, and
which thus correspond to the rods and cones of the retina.
Finally, the upper half of the tube is subdivided by a
membranous cross-partition, stretched obliquely between
the oval window and the hair-cells, as if to protect these
from the direct impact of the waves set up by the push of
the ossicles.
We have seen that the ear is an analyser, that it is able
to split up a compound wave-motion into simple pendular
vibrations, or to resolve a compound tone into simple
partial tones. According to the theory of Helmholtz, this
analysis is performed by the basilar membrane. Histolo-
gists tell us that the membrane is composed, in essentials,
of a large number of cross-fibres — variously estimated at
13400 to 24000 — which range in length from 0.041 to
0.49 mm., a ratio of 1:12. The fibres represent a system
of stretched strings, like those of a harp or a piano, and will
accordingly respond by vibration to the wave-movements
to which they are tuned. Suppose, then, that a wave-
motion of a certain frequency is set up at the oval window.
The motion is transmitted, through the membranous cross-
partition, to the basilar membrane. A certain basilar fibre
(the fibre whose natural period of vibration is the same as
that of the incoming wave) is set vibrating ; this vibratory
movement is imparted to the hairs of the cells which rest
§ 28, Theory of Audition iii
upon the fibre ; and the agitation of the hairs acts as
stimulus to the fibrils of the auditory nerve. The wave-
motion, having thus done its work upon the basilar mem-
brane, spends itself at the round window, and the whole
system comes to rest again.
The Helmholtz theory regards the fibres of the basilar mem-
brane as resonators, and is therefore known as the resonance
theory of audition. Just as the strings of a piano respond
selectively when a tone is sung into the instrument, so do the
basilar fibres vibrate in sympathy with the wave-motion which
corresponds to their natural period of vibration. The tuning of
the fibres and their selective response to stimulus must not, how-
ever, be thought of as absolute. Neighbouring basilar fibres differ
but little in length, and are closely bound together. Hence we must
suppose that, if a simple pendular vibration is set up at the oval
window, it is not a single fibre but rather a narrow strip of the
basilar membrane which falls into sympathetic vibration. The
sensation of simple tone results from the agitation of the hairs of a
little group or field of hair cells.
To account for the sensation of noise, we need only assume that
a broader strip, or perhaps that several broad strips of the basilar
membrane at the same time are thrown into brief vibration. The
compound tone will be produced by the simultaneous vibration,
at different amplitudes, of a number of narrow strips, each one of
which, if it vibrated alone, would give us the sensation of a simple
tone.
To account for beats, we must suppose that the strips set in
motion by the two generating tones partially overlap. So long as
the generators are near together, we hear only a single tone, — the
intermediate tone, due to the superposition of the primary vibra-
tions. The portions of the strips which do not overlap are so
small that they cannot vibrate independently and give rise to
independent tonal sensations. The beating of the intermediate
tone results from the interference of the different oscillatory
motions impressed upon the fibres. As the generators diverge, we
112 Audition
hear them sounding smoothly above and below the beating inter-
mediate tone. It is now only a comparatively small portion of the
vibrating strips that overlaps; so that the major portions on
either side vibrate singly, each in its proper period, and con-
sequently arouse each its proper sensation of tone.
Helmholtz himself explained combinational tones as due to the
movements of the drum-skin and ossicles. Attempts have since
been made to derive them from the vibration of the basilar fibres ;
but recent investigation seems to show that Helmholtz may have
been right, and that these tones may take their physical origin in
the middle ear.
There is nothing in audition that is analogous to colour blindness
in vision. On the other hand, the resonance theory receives
strong support from pathology. Cases are known in which, while
the outer and middle ears are intact, the range of hearing is
greatly reduced : all that is left of the tonal scale is a tonal
* island,' extending perhaps over a couple of octaves, perhaps only
over two adjacent semitones. Other cases occur in which the
range of hearing is normal, but the tonal scale is not continuous ;
there are tonal 'gaps,' large or small, — parts of the scale where
the patient is completely deaf to tonal stimuli, though he can
perfectly well hear the tones above and below. Both of these
defects of hearing point to the existence, in the internal ear, of a
series of end-organs that are separately stimulable by tones of
different pitch-number ; and end-organs of this sort are provided
by the basilar fibres and the hair-cells which they support.
The principal objection urged against the Helmholtz theory is
that the basilar fibres are too minutely small to serve as resonators,
especially for the tones of the lower region of the scale. To this
the reply is made that they are loaded, by the arches of Corti and
the adjacent cells, and that their frequency of vibration is thus very
considerably reduced. We cannot at present say either that the
objection is fatal to the theory or that the reply is convincing in
its favour. No other theory has, however, been proposed which
covers so wide a range of facts or "explains these facts so satis-
factorily as the resonance theory.
References for Further Reading 113
References for Further Reading
§§ 23-28. A general summary of facts and theories is given by
K. L. Schaefer, professor of physiology at Berlin, in Nagel's Handbuch,
iii., 1905, 476 ff. More detailed treatment of the subject will be found
in the Tonpsychologie of C. Stumpf, professor of philosophy at Berlin.
On the character of auditory sensations at large, see i., 1883, §§ 10, 11 ;
ii., 1890, § 28 : on tone-colour and timbre, ii., § 28 : on beats, ii., § 27 :
on combinational tones, ii., 243 ff., and other passages cited in the
index. Another classical work is Helmholtz' On the Sensations of
Tone, translated by A. J. Ellis, 1895. Parts i. and ii. deal with the
subject-matter of these sections ; the author's theory is worked out on
pp. 128 ff., 158. — Consult also A. Barth, Zur Lehre von den Tonen
und Gerduschen, in Zeitschrift f. Ohrenheilkiinde, xvii., 1887, 81 ; art.
Hearing, in Baldwin''s Diet., i., 1901, 443 ff. ; W.Wundt, Physiologische
Psychologies ii., 1902, 63 ff., 370.
It has been known for some time that the vowel-sounds of the human
voice owe their timbre, not to a regular series of overtones, but to cer-
tain concomitant tones, whose pitch remains relatively constant what-
ever the fundamental may be upon which the vowel is spoken or sung.
These tones, called by L. Hermann '■ formants,' apparently represent
the proper tones of the buccal resonance chambers ; they are usually
inharmonic both to the fundamental and to one another ; and they may
attain to a high degree of intensity. Recent investigations, now, seem
to show that the timbre of the wind instruments may also be due to the
presence of formants: "instead of a characteristic series of harmonics,
it seems that each instrument possesses rather a characteristic tone or
tones ... of constant pitch for all notes of its scale" (D. C. Miller,
Science, N. S., xxix., 1909, 171 ; cf. R. Wachsmuth und G. Meissner,
Arch.f. d. gesammte Physiologie, cxvi., 1907, 543 ; E. Herrmann-Goldap,
Annalen d. Physik, xxiii., 1907, 979). If this result is coniirmed, the
account given of timbre in § 25 must be correspondingly modified.
Negative results have, however, been obtained by W. Kohler, Akustischt
Unte*'suclirunge)i, ia Zeits.f. Psych. ^ liv., 1909, 241 ff.
SMELL
§ 29. Sight and Hearing : Taste and Smell. — If you
were asked to make out a list of the senses, you would
probably begin with sight and hearing. These two seem,
naturally, to go together : they are the ' higher ' as con-
trasted with all the other, ' lower ' senses. The word
' higher ' may then mean one of two things : that the
sense-organs, eye and ear, have attained to the highest
degree of biological development ; or that the sensations
derived from them are put to the highest intellectual pur-
poses. The second meaning is, perhaps, that which is the
more familiar to common sense. Sight and hearing have
an obvious twofold value to the organism : a commercial
value, as the vehicle of communication, of written and
spoken language ; and a cultural value, as the vehicle of
the fine arts, painting and sculpture, literature and music.
From this point of view, the bracketing together of sight
and hearing is both natural and right : only, of course,
while we talk in terms of common sense, we must think in
terms of parallelism. On the other hand, it is worth while
to remember that, psychologically, the differences between
the two senses are very great. Visual sensations form
a manifold of three dimensions ; sensations of tone, a
manifold of two dimensions. Colour mixtures appear
themselves as simple sensations, while mixtures of tones
are analysable into their constituents. Again, there is no
114
§ 29- Sight and Hearing: Taste and Smell 115
such thing as tonal contrast, or a negative after-image of
tone. The phenomenon of beats has been compared to
that of flicker ; but there is nothing in vision that resem-
bles the combinational tones. And when we turn from
description to explanation, we find that antagonism is the
keynote of visual, and sympathetic resonance the keynote
of auditory theory. — We may sum up these differences
between sight and hearing, in a single word, by saying
that the former is a chemical and the latter a mechanical
sense.
Next after sight and hearing, in a list of the senses,
stand taste and smell. These, too, seem to go together
as a matter of course. Psychologically, indeed, they have
good right to go together. Both alike are chemical
senses, and the two groups of sensations are intimately
connected in experience : so intimately, that in everyday
life we are constantly attributing to taste what really
belongs to smell. Most meats and vegetables are taste-
less. If you hold your nose, you cannot distinguish a bit
of apple from raw potato, or vinegar from claret. A cold
in the head does not affect taste, as we ordinarily suppose ;
what really happens is that the accumulation of mucus in
the nose cuts off the sense of smell. It is clear that such
gross confusion would not be possible unless the qualities
of taste and smell were very much alike : nobody would
confuse a colour with a tone ! As a matter of fact, it may
well be doubted if the scent of lavender and the taste of
sugar do not stand, psychologically, nearer together than
the taste of sugar and the taste of quinine.
On the biological side, also, the senses of taste and smell
are closely related. Both of them, though in slightly dif-
ferent ways, stand guard over the great function of nutri-
Ii6 Smell
tion, inviting the organism to what is wholesome anj
warning it of what is deleterious.
The sense of smell is of peculiar interest : partly on account of
the problems which it sets to psychology, and which — as we shall
see in the following sections — are still very far from solution;
partly on account of the role that it has played in the course of
organic evolution. Far back in the history of life, among the
reptiles, the cortex appears as little more than an annex to the
organ of smell. As development proceeded, the sense retained
its importance as the servant of nutrition and reproduction : we
know, for instance, how largely it bulks in the mental life of the
carnivorous mammals. It is, however, essentially a land-sense :
the mammals which live wholly or partially in the water — whale,
dolphin, seal — possess a very rudimentary organ of smell, and
are probably without smell sensations. The sense-organs in fishes
which have been described as organs of smell differ in structure
from the corresponding organs of land animals, and apparently
furnish sensations, not of smell, but of something akin to taste.
It is also a ground^sense : birds have, in general, very obtuse
smell ; and our own disregard of smell sensations is largely due to
our assumption of the upright position.
On the other hand, there is no evidence for the statement,
often as it is made, that in man the sense of smell is degenerating.
Both in range of quality and in discrimination of intensity (§ 66),
it holds its own as against the other senses. Moreover, odours
still have a high biological importance as appetisers : the smell of
cooking makes the mouth water, as we say ; and invalids may be
tempted to eat by the aroma of the dishes set before them. The
significance of smell for nutrition is masked by the fact that, in
man, stimulation of the organ from within the mouth, especially
in the act of swallowing, is at least as important as its stimulation
through the external nostrils ; and here, as we have said, all the
credit is taken by taste. Whether the sense of smell has any
large share, primary or derivative, in the sexual life of man is a
disputed point. There are, no doubt, large individual differences
in this regard ; but, on the whole, the evidence is decidedly in the
affirmative.
§ 30' The Olfactory Qualities 1 17
§ 30. The Olfactory Qualities. — The sense of smell, like
the senses of sight and hearing, includes a very large num-
ber of qualities of sensation. It is impossible to say, at
present, what this number is ; we know too little about the
world of odours to be able to undertake its systematic ex-
ploration. Indeed, the number may always remain inde-
terminable, since new odours are constantly added to the
. list. The progress of chemistry and of the arts that de-
pend upon it means the continual discovery of odorous
substances ; and every experiment upon the cultivation of
flowers and fruits may, in favourable climatic conditions,
furnish a new perfume.
Under these circumstances, we can do no more than give
a provisional classification of the smell qualities, based on
their introspective resemblances. The following division
into nine classes dates, in the main, from the great Swedish
naturalist Linnaeus.
1. Ethereal or Fruit Odours.- — All fruit and wine odours; the
scents of the various ethers ; the smell of beeswax.
2. Aromatic or Spice Odours. — All spicy smells : camphor, tur-
pentine, cloves, ginger, pepper, bay leaves, cinnamon, cara-
way, anise, peppermint, lavender, bitter almonds, rosemary,
sassafras ; thyme, geranium, bergamot ; rosewood, cedar-
wood, etc.
3. Fragrant or Flower Odours. — All flower scents ; vanilla,
tonka bean, tea, hay ; gum benzoin, etc.
4. Ambrosiac or Musky Odours. — Musk, ambergris, sandalwood,
patchouli.
5. Alliaceous or Leek Odours. — Onion, garlic, asafoetida ; india-
rubber, dried fish, chlorine, iodine.
6. Empyreumatic or Burned Odours. — Roasted coffee, toast,
tobacco smoke, tar, burned horn, carbolic acid, naphthalene,
benzine, creosotq.
1 1 8 Smell
7. Hircine or Rank Odours. — Stale cheese, sweat, valerian, root
and stem of barberry and black currant, lactic acid, caproic
acid.
8. Virulent and Foul Odours. — Opium, laudanum, French mari-
gold, fresh coriander seeds, bed bugs, squash bugs.
9. Nauseous Odours. — Carrion flowers, stinkhorns, water from
wilted flower stems, decaying animal matter, faeces.
All of these classes may be further subdivided, and in
some cases the subdivisions may themselves be split up into
still smaller groups. It is, however, unnecessary to go into
more detail. The list is unsatisfactory, first, because there
are many odours that cannot certainly be classed under
any one of the nine headings ; and, secondly, because the
odours under certain headings (i and 3, or 2 and 4) seem
to be more nearly related than are particular odours under
a single heading (2 or 6). Nevertheless, it serves to give
an idea of the immense range and variety of the olfactory
qualities^
Many of the stimuli mentioned in the list have sensory effects
that extend far beyond the domain of smell. Thus the two ordi-
nary anaesthetics, chloroform and ether, belong as scents to the
ethereal group. But, further, inhaled chloroform tastes sweet,
and inhaled ether bitter ; while both stimuli may, by diffusion,
give rise to sensations of cold and, by direct application, to sensa-
tions of pain. Pungent odours (ammonia, pepper, mustard) arouse
pricking or tingling sensations in the nose and throat. The smell
of onions and of horse-radish brings tears to the eyes ; in some
cases, the smell of hay or of newly turned garden mould has an
unpleasant effect upon breathing. Odours of the eighth and ninth
classes may excite the sensation of nausea. — In view of these
facts, it becomes necessary for us to raise the question of the es-
sential nature of the olfactory stimulus, and of its mode of action
upon the organ of smell.
§ 31' Olfactory Sensation and Olfactory Stimulus 119
§ 31. Olfactory Sensation and Olfactory Stimulus. — Sen-
sations of smell are aroused, not by the transmission of
wave-motions through air or ether, but by the actual con-
tact of material particles with the sense-organ. The odor-
ous particles may be given off by volatile substances in
our immediate surroundings, or may be brought from a
distance by currents of air. They are received into the
nose in the act of inspiration : if we wish to get the full
fragrance of a flower, we sniff at it ; so long as we hold
the breath, we smell nothing. It follows that all smell
stimuli must exist in the form of gas or vapour ; solids and
liquids are odorous only if they are also volatile.
Sensations of smell may also be set up by way of the posterior
nares : especially is this the case, as we have said, in the act of
swallowing. If scented air is inhaled through the mouth, and
expired through the nose, the scent will be clearly perceived,
though there is some loss of intensity due to the adhesion of
odorous particles to the moist lining of mouth and throat.
It is possible, though it is by no means easy, to drive out all
the air from the cavities of the nose, and thus to bring an odorous
liquid into direct contact with the organ of smell. Experiments
of this sort have been made, but with uncertain result. Even if
we grant, however, that liquid stimuli can arouse sensations
of smell, it would still remain true that the normal olfactory
stimulus has the gaseous form.
There can be no doubt that the action of stimuli upon
the organ of smell is chemical in its nature, so that a sub-
stance is odorous or inodorous by virtue of its chemical con-
stitution. Many attempts have been made to express this
fact in precise terms, — to discover precisely what sort of
molecule is able to arouse an olfactory sensation. No sin-
gle or general law has as yet been found. The following
results show, however, that the prospect is not hopeless.
1 20 Smell
In the first place, it is agreed by most investigators that
the chemical elements are inodorous. True, exceptions to
the rule (chlorine, bromine, iodine) at once suggest them-
selves. It is probable, however, that these substances
become odorous only in combination with the hydrogen
of the air in the nasal cavities. If the rule holds, our field
of search is so far restricted ; we may neglect the atom,
and turn our attention solely to the molecule.
Secondly, all odorous substances (with one exception)
are derived from the trivalent, divalent, and univalent ele-
ments of the fifth, sixth, and seventh groups.^ The single
exception is given with the great group of the hydro-
carbons. The real odorous substance in their case may,
however, be a product of oxidation. Again, therefore, if
the rule holds, our field of search is restricted ; we may
confine our attention to molecules which contain certain
elements from group V., VI., or VII.
It must be confessed that these two rules, even if strictly valid,
do not take us very far. Detailed study of the chemical composi-
tion of substances of like odour, and of the odour of substances
of like chemical composition, does not, as yet, take us much
farther. One point is worth mentioning : it has been found that
the homologous series of organic chemistry furnish, within Hmits,
series of related but progressively diverging odours, so that like-
ness or difference of smell runs rougiily parallel to likeness or dif-
ference of chemical constitution. An illustration will make this
rule clear. The series of fatty acids begins with formic (CHoOg),
acetic (C2H4O2), propionic (CaHyO^), butyric (C4HSO:,), valerianic
(C5H10O2), caproic (CeHjoOo). All these substances have related
^ A statement and explanation of the periodic law, and a table of the ele»
ments arranged in accordance with it, will be found in any good encyclopaedia.
The important elements are: V. nitrogen, phosphorus, arsenic, antimony,
bismuth; VI. oxygen, sulphur, selenium, tellurium; VII. fluorine, chlorine,
bromine, iodine. Their serial positions should be noted.
§32. Smell Mixtures
121
odours, which become increasingly different with increasing dis<
tance between the terms of the series. Moreover, the odour,
which in formic acid is weak, grows stronger and stronger as the
series advances. Presently, however, the olfactory quality rather
abruptly lapses : the higher acids — palmitic (C16H32O2), margaric
(Ci;H3402), stearic (CisH^eOi), etc. — are almost or entirely in-
odorous. — As things are, theory can do little with these and simi-
lar facts ; but it is clear that, if such uniformities occur, a chemistry
of smell must in the long run be possible of achievement.
In fine, then, we cannot correlate olfactory quality with the
configuration of the molecule, as we can correlate visual quality
with the wave-length of light, and auditory quality with the wave-
number of sound, though we may hope that some day a chemical
correlation will be made out.
§ 32. The Dependence of Olfactory Sensation upon the Com-
position and Time-relations of Stimulus. — Sight and smell
are both chemical senses. We may, therefore, expect
to find a certain resemblance in the mode of behaviour
of their sense-organs. How far the resemblance goes, w^e
shall discover only by experiment ; but we may safely look
to sight for guidance in our first investigations of smell. —
Two colours that are mixed
in accordance with the first
or second law of colour mix-
ture either neutralise each
other or produce a new, in-
termediate colour. What
happens if we mix two
odours .''
We may proceed in two
ways : we may conduct the
odours separately to the two nostrils, by means of the
olfactometer ; or — if chemical combination does not occur
Fig. 18. Double Olfactometer (solid
stimuli).
122
Smell
— we may make a mechanical mixture of the odorous sub.
stances before smelling. In both cases, we obtain results
analogous to those got by the mixture of colours.
First, there are undoubtedly odours which, if mixed
in the right proportions, neutrahse each other. Bridal
bouquets often have gardenia mixed with their orange-
blossoms, in order that the aromatic scent may weaken the
too powerful fragrance. Tooth-powder of orris root is
used to counteract the foetor ex ore. In medical practice,
and in the operating room, recourse is had to this principle
of compensation : balsam of Peru offsets the smell of
iodoform, and carbolic acid the stench of pulmonary gan-
grene. Laboratory experiments yield the same result : the
odour of red india-rubber, for instance, neutralises the
odours of cedarwood, gum
benzoin, paraffin, beeswax,
tolu balsam, etc.
Secondly, there are
odours which, if mixed in
the right proportions, give
rise to a resultant odour, a
new olfactory quality. Most
of us have noticed that the
addition of a few fragrant
leaves to a bunch of flow-
ers may alter the scent of
the whole bouquet ; that
the mixture of two toilet
perfumes may produce a
perfume different from
either ; that the attempt to overpower a foul or nauseous
odour by a perfume will sometimes set up a scent more
Fig. 19.
Double Olfactometer (liquid
stimuli).
§ 32. Smell Mixtures 123
sickening than the first. Laboratory experiments bear out
this conclusion : new odours arise, for example, from the
mixture of musk and opium or listerine, iodine and ylang
ylang or camphor, valerianic acid and lavender or hya-
cinth. In all such cases the resultant odour is simple
and unanalysable; it resembles the component odours, but
it cannot be resolved into them.
Whether odours have a constant mixing value, inde-
pendent of their mode of origin, — whether, that is, we
have in smell an analogue of the third law of colour mix-
ture, — cannot be said with certainty. The trend of evi-
dence appears to be towards the affirmative.
The likeness between these results and those of colour mixture
is evident. Nevertheless, there are striking differences. Thus,
smell mixtures are, in general, much less stable than colour mix-
tures. Experiment shows that two odours rarely neutralise each
other completely for more than a few seconds ; it is easy to obtain
an unsaturated odour of the quality of the stronger component,
but not easy to get actual extinction. This seems to mean that
the chemical equilibrium of the olfactory cells is less stable than that
of the retinal cones. In the same way, the new odour resulting
from a twofold mixture is often transitory in character, giving
place either to the odour of a single component or to an oscilla-
tion of the two. This is due, in many instances, to the fact that
the sense-organ becomes more quickly adapted to the one stimulus
than, to the other, or that the substances mixed are not equally
volatile ; but in others it also seems to point to a chemical insta-
bility of the olfactory cells. Resultant odours of a more per-
manent kind may be secured by the mixture of a number o{
components. The flower perfumes of the perfume industry are,
as a rule, quite complicated mixtures : heliotrope, for example, is
derived from the mixture of vanilla, rose, orange-flower, ambergris
and almond.
Again, it is impossible to draw a sharp line of division between
1 24 Smell
compleraentaiy odours and odours that combine. We should
naturally expect that the members of the same or of related
classes would mix, and that the members of diverse classes would
cancel one another. Some ten years ago, a statement to this
eifect would have found support in the composition of toilet per-
fumes, in pharmaceutical practice, and in the results of psycho-
logical experiment. Recent work has proved, however, that no
such rule can be laid down : odours of the second and eighth
classes, for instance, may combine as readily as odours within
either group, and odours taken from the same class may behave
as complementaries. Evidently, there is in smell no such clean-
cut principle of antagonism as we have found in sight.
The fact of adaptation to stimulus is, perhaps, more in
evidence in the case of smell than it is even in that of
vision. Odours of the most insistent kind fade out, if
only the stimulation is kept up without intermission, in
a comparatively short time. Workers in tanneries,
cheese warehouses and fish markets, garbage collectors,
habitual smokers, patients with iodoform dressings, medi-
cal students in the dissecting room, — these persons are,
as a rule, quite unconscious of the odours that surround
them. All of us have, probably, at one time or another,
been asked to go into a certain room and "see if we
don't smell fire," and have noticed that, after a few
vigorous sniffs, we were wholly unable to say whether
we did or did not. Laboratory experiments simply make
these observations more precise. Thus, heliotrope be-
comes inodorous if smelled for about 5 min. ; asafoetida
in i^ min. ; stale cheese in 8 min. ; and so on.
Here, too, there are marked differences between smell and
sight. The fading out of a given sensation does not mean the
arousal of its complementary ; there is no negative after-image
of smell; adaptation to india-rubber does not leave us with a
§ 33- Theory of Smell 125
scent of cedanvood or tolu or beeswax. The effect of adaptation
is simply to increase our sensitivity for certain odours, and to re-
duce or destroy it for others. Thus, it has been found that a
partial adaptation to cedarwood or tolu or beeswax renders the
nose more sensitive to the smell of india-rubber, while partial
adaptation to glycerine soap or cocoa butter or Russian leather
has no such effect. On the other hand, adaptation to iodine
leaves us insensitive to the odour of eau de Cologne, absolute
ilcohol, heliotrope, oil of caraway. In this way, a continuous
adaptation of the sort mentioned above may materially change
the world of odours : the user of perfumery, the smoker, the
hospital attendant, will be peculiarly susceptible to certain scents
and peculiarly obtuse to others. There is, of course, a possibility
that the sense of smell as a whole may be blunted by the repeated
appUcation of the same stimulus.^
§ 33. Theory of Smell. — The organ of smell^ is ex-
tremely simple. It consists of a patch of brownish mu-
cous membrane, not much larger than one's little-finger
nail, which lines the roof and part of the walls of the
extreme upper portion of the nasal cavities. This ter-
minal pouch is so narrow and so remote that the air
current of respiration does not reach it; the olfactory
epitheUum can be stimulated only by diffusion or by
eddies from the main stream. The olfactory cells are set
amongst columnar supporting cells ; they are very slender,
possess a large nucleus, and are prolonged peripherally as
rod-shaped processes ending between the columnar cells
at the free surface of the epithelium.
1 It is said, in recent text-books, that smokers possess only about f of the
normal sensitivity to odours. The statement is apparently taken from H.
Griesbach, who in 1899 published a comparative study of the senses of
hearing, smell and touch in the blind and the seeing (^Archiv f. d. gesanimtt
Physiologie, Ixxiv., 577; Ixxv., 365, 523). But Griesbach worked only with
india-rubber !
2 The author uses the Deyrolle model, Coupe mediane du nezgrossi.
1 26 Smell
This simplicity of structure suggests at once that the
organ of smell must respond to olfactory stimulus in.
the same sort of way as the eye to light, and not as the
ear to sound. For every sensation of tone we find a
separate structure in the cochlea. On the other hand,
all the sensations represented in the colour pyramid are
derived from the six antagonistic processes in the cones
{Bk-W, B-Y, R-G) and from the cortical grey. Our day-
light vision, rich as it is in sense qualities, depends simply
upon four chemical reactions, three reversible and one
constant. Now a theory which, like the theory of vision,
reduces the manifold of psychological elements to a small
number of elementary psychophysical processes is termed
a theory of components. Black, white, grey, and the in-
variable R, G, B and Y are the components of our visual
theory : psychophysically, they are the elements of vision,
though psychologically they are no more elementary than
orange or violet or purple. It is important to bear this
distinction in mind.
We may expect, then, that the right theory of smell will
be a component theory. This expectation is borne out
by the fact, already mentioned in § 32, that adaptation to
a particular odour leaves us insensitive to some, while it
does not impair our sensitivity to other odours. The
odours that are killed by adaptation to iodine, for instance,
evidently require for their arousal the same psychophysi-
cal processes : they stand to iodine in much the same re-
lation that rose, lilac, mauve, heliotrope, purple bear to
violet. If, therefore, we could work over the whole range
of olfactory qualities, and find out which are weakened or
blotted out, and which are left intact, by adaptation to the
various odours taken singly, we might hope to discover
§ 33- Theory of Smell 127
the psychophysical elements of olfactory sensation. In-
deed, the programme need not be made so comprehensive :
if we could work systematically with even a few odours,
selected from all the nine classes and their recognised sub-
divisions, it is probable that the outlines of a component
theory would emerge from our results.
The work is, however, exceedingly laborious, and con-
sumes a great deal of time. Something has been done;
very much more remains to do. It has been calculated,
on the basis of our present knowledge, that 30 or 40 spe-
cific chemical processes must be assumed for the sense of
smell, — many more than for dayhght vision. It is unlikely
that there are 30 or 40 kinds of olfactory cells. But
whether there are, say, 10 sorts of cells, each the seat of
3 or 4 processes, or 3 or 4 sorts of cells, each the seat of
10 different chemical processes, we have no possible means
of deciding.
While these phenomena of adaptation afford the strongest sup-
port to a component theory, they do not by any means stand
alone. It is clear that the results of smell mixture — resultant
odours and compensations — point in the same direction, as does
also the mere fact that odours may be grouped, by their intro-
spective resemblances, into a number of distinct classes. Further
evidence comes from pathology. In cases of partial anosmia,
which occurs both as congenital defect and as the consequence of
influenza, diphtheria, etc., the patient is insensitive to some and
sensitive to other odours : thus, the musky odours or the vanilla-
group of the fragrant odours may be destroyed or weakened,
while all the rest persist in their normal character. Cases of par-
osmia, or subjective perversion of the sense of smell, fall into
similar groups, which, so far as they have been investigated, ap-
pear to correspond with the fourth, fifth, sixth and ninth olfac'
tory classes.
128 Smell
References for Further Reading
§§ 29-33. Die Physiologie des Geruchs, 1895, by H. Zwaardemaker.
professor of physiology at Utrecht; J. Passy, Revue ghierale sur les
sensations olf actives, in Amite psychologique, ii., 1896, 363 fF. ; W.
Wundt, Physiologische Psychologie, ii., 1902, 46 flf. ; W. Nagel, Der Ge-
ruchssinn, in NageVs Handbuch, iii., 1905, 589 ff.
TASTE
§ 34. The Gustatory Qualities. — For the most part, sen-
sations of taste come to us blended with sensations of
smell, touch and temperature. These blends have a
curiously unitary character: it is only by directing tho
attention, in the light of past experience, first to one and
then to another aspect of the given whole, that we can
distinguish the separate components. Thus the flavour
of a peach, or of black coffee, seems to be simple and
unique; but we may happen to notice the aroma before
we begin to taste, and in this way take an involuntary
first step towards analysis. At times, the difference be-
tween smell and taste comes to us with a sort of shock ;
the bitter taste of unsweetened chocolate, for instance, is
in sharp contrast to the aromatic odour. Again, we may
remark that our food to-day is more savoury than it was
yesterday, when our nose was stopped up with a cold ;
or we may discover that the repulsive flavour of certain
medicines, such as castor oil, is avoided by the simple
expedient of holding the nose. In all these cases, and in
many others like them, everyday experience plays into
the hands of psychological analysis. Smell and taste are,
after all, separate senses with separate sense-organs; and
while a blending of their sensations is the rule, occasions
are bound to arise when we taste without smelling or
smell without tasting.
1 30 Taste
There is no such natural separation of taste from touch
and temperature. It is, however, not difficult to observe
that in oily and fatty tastes we have something that is
precisely like the feel of greasy fingers, and in pungent
and biting tastes something that is precisely like the prick-
ing of pungent odours in the nose or the bite of mustard-
plaster upon the skin. The cold of ice-cream in the mouth
is the same as the cold of icy water to the hands; and
when a too hot soup scalds the tongue we have — apart
from the impairment of taste itself — the same sensations
as when we step into a too hot bath. Having made these
observations, we are able to single out, by the attention,
the touch and temperature components in ordinary tastes.
If the taste-blends are thus analysed, and the foreign
constituents referred to the sense-departments to which
they properly belong, there remain only four qualities of
taste: sweet, bitter, sour and salt. Here is poverty in-
deed, as compared with the wealth of sight, hearing and
smell ! — and a poverty all the more striking, since taste
makes so brave a show of variety in everyday life.
This result depends, not only upon introspective analysis of the
taste-blends, but also upon a systematic exploration of the organ of
taste with very various kinds of stimulus. Before the experimental
tests were made, the lists of gustatory qualities put forward by dif-
ferent authors were, as we should expect, widely different. It
would, however," be a mistake to suppose that they have grown
steadily shorter as analysis has advanced. None of them are very
long. Smell, indeed, seems to have been practically eliminated al-
most from the outset, though some physiologists speak of aromatic
tastes, foul tastes, etc., and it is odd that the rule of holding the
nose during experiments on taste was laid down for the first
time by the French chemist M. E. Chevreul as late as 1824, On
the other hand, the touch and temperature components evidently
§ 35- Gustatory Sensation and Gustatory Stimulus 131
presented great difficulty. We find oily tastes, pungent tastes,
smooth tastes, astringent tastes, etc., figuring in the scheme of taste
qualities ; and contrariwise we find sour and salt transferred, on ac-
count of their astringent and burning character, from the sense of
taste to that of touch. Here, then, are give and take, addition and
subtraction : Linnaeus brought the number of tastes up to 10, but
a recent investigator^ who reduces them to 2 (sweet and bitter) is
merely repeating what had been said sixty years earher.^
It was long supposed that nausea is a taste quality; this view
was taken, for instance, by so great a man as Johannes Miiller, the
father of modern physiology, on the ground that the sensation
aroused by pressure on the base of the tongue — putting your fin-
ger down your throat — cannot be identified with any quality of
touch. ^ At the present time, many psychologists incline to the
view that the alkaline and the metallic tastes must be regarded as
elementary qualities of taste ; but tests made with the nose closed
prove that the irreducible factor in both cases is due to smell. — •
If smell is ruled out, the ordinary taste-blends may be analysed
as follows. Sour is at first astringent ; then, as it becomes stronger,
burning ; finally, purely painful. Salt is attended by a weak burn-
ing, which does not rise to positive pain. Sweet brings with it the
perception of smoothness and softness ; at high intensities of stim-
ulus, it pricks or gives a sharp burn. Bitter suggests something
fatty ; at high intensities it may burn.
§ 35. Gustatory Sensation and Gustatory Stimulus. — In
order to be sapid, a substance must be, to some extent,
soluble in the saliva of the mouth. If this condition is ful-
filled, it may exist in any form, as solid or liquid, vapour or
gas.
There are, however, soluble substances which are taste-
^ W. Sternberg, Geschmack tmd Chemisnnis, in Zeitschrift f. Psychologie u.
Physiologic d. Sinnesorgane, xx., 1899, 387.
2 By L. H. Zenneck in J. A. Buchner's Reperto7'int7i f. d. Pharmacie, Ixv.
(ate Reihe, xv.), 1839, 224 ff.
^ Handbuch der Physiologic des Menschen, ii., 1840, 489.
132 Taste
less. We are thus thrown back, as in the case of smell,
upon the question of chemical constitution, and must try to
work out a correlation between stimulus and sensation in
chemical terms. Now chemistry uses the terms salt, acid,
sugar as class-names for related groups of compounds.
All three words — as well as the phrase 'bitter principles,'
which is employed in pharmacy and in organic chemistry —
are borrowed from the sense of taste; and we can say off-
hand, from ordinary experience, that acids generally taste
sour, salts salty, and sugars sweet. A little enquiry brings
out the further fact that the bitters with which we are
most familiar are alkaloids. Can we, then, correlate the
four taste qualities with these four types of chemical com-
bination .''
Unfortunately, the rule has puzzling exceptions even in
the cases of sour and salt. It is true that we get the taste
of salt only from chemical salts : but there are chemical
salts that taste sweet, others that taste bitter, and others
again that have no taste at all. It is also true, apparently,
that we get the taste of sour only from chemical acids, or
from substances that contain acids : but there are acids that
taste sweet, acids that are tasteless, and at least one acid
(hydrocyanic) which is said to taste bitter. The suggestion
has been made that the sour taste of the majority of acids
may be accounted for by their ionisation in aqueous solu-
tion, — may be ascribed, that is, to the setting free of the
common ion hydrogen. Hydrocyanic acid is only partially
ionised, and the tasteless fatty acids like palmitic, stearic
and oleic are insoluble in water. — There is undoubtedly a
close chemical relation between sweet and bitter ; a very
slight change of chemical constitution will change the
one taste into the other. The groups of sweet-tasting and
§ T)6. Mixtures atid Adaptations 133
pitter-tasting substances are, however, extremely hetero-
geneous.
In fine, then, much detailed work is needed, in taste as in
smell, before any general law of the correlation of stimulus
and sensation can be made out.
It has been pointed out that the inorganic sweet-tasting sub-
etances are derived from elements of the III., IV. and V. groups,
and that these elements are, so to say, double-faced, since they
combine with acids as bases and with bases as acids to form salts.
On the other hand, the inorganic bitter-tasting substances are
derived from electropositive elements of the I. and II., and from
electronegative elements of the VI. and VII. groups. Here is the
hint of a principle, which may perhaps be carried over to the
organic compounds , and it has, in fact, been maintained that all
the sweet-tasting organic substances have this double, ± -character,
while all the bitter-tasting — -though closely related to them —
have either the p/us or the minus sign. If the rule holds, we can
readily understand that a slight change of the sweet-generating
molecule will transform it into a generator of bitter. However, it
is best to be on one's guard against premature generalisation.
§ 36. Mixtures and Adaptations. — We know, from every-
day experience, that certain tastes are more or less
antagonistic. Sugar moderates the bitter taste of coffee
and chocolate, and the sour taste of unripe fruit. Sour
and salt offset each other, to a certain extent, in sour
pickles and salad dressings. Salt corrects the too luscious
sweetness of an overripe melon. On the other hand, bitter
and salt may exist side by side, as in the taste of olives ;
and bitter and sour, as in that of a green peach.
Observations of this sort are, however, unsatisfactory.
First of all, the act of eating or drinking brings the taste-
stimulus into contact with the whole surface of the tongue.
If, then, the particular stimulus contains salt and bitter,
1 34 Taste
we may have the sensation of salt set up at a part of the
tongue which is especially sensitive to salt, and the sensa-
tion of bitter at another part, especially sensitive to bitter :
the two qualities will thus appear side by side, just as a
blue and a yellow may appear side by side in the field of
vision. To obtain assured results we must apply the mixed
stimulus at one and the same point. Secondly, the four
taste-qualities require different times for their arousal : salt
comes first, then sweet, then sour, and bitter last. It is
quite possible that, in ordinary life, these time-differences
escape notice, so that we may regard two tastes as occur-
ring together when really they occur in succession. And
thirdly there is no guarantee, under the conditions, that
stimuli are mixed in the right proportions. For all these
reasons, we must have recourse to experiment.
A careful study of taste-mixtures in the laboratory
brings out the following facts. With high intensities of
stimulus, the two tastes seem not to influence each other;
they simply oscillate. With low intensities, there is in
most cases a partial compensation, which is least for sweet
and sour, better for salt and bitter, better still for sour and
bitter, sour and salt, and sweet and bitter. The antago-
nism is not so clean-cut as it is in the case of sight ; we
rarely, if ever, obtain actual neutralisation of two compen-
satory tastes. Only in one instance, the mixture of sweet
and salt, is there any reminder of the second law of colour
mixture. If salt is added, little by little, to. a v/eak sweet,
there presently emerges a taste which is neither salt nor
sweet, but flat and vapid.
We remarked in § 34 upon the curiously unitary character of
the taste-blends. It is worth noticing here that the unitariness
persists in spite of the antagonistic nature of the taste qualities.
§ 36- Mixtures and Adaptations 135
Think, for instance, of the flav^our of a ripe peach. The ethereal
odour may be ruled out by holding the nose. The taste com-
ponents — sweet, bitter, sour — may be identified by special direc-
tion of the attention upon them. The touch components — thij
softness and stringiness of the pulp, the puckery feel of the sour
— may be singled out in the same way. Nevertheless, all these
factors blend together so intimately that it is hard to give up one's
belief in a peculiar and unanalysable peach-flavour. Indeed, some
psychologists assert that this resultant flavour exists ; that in all
such cases the concurrence of the taste qualities gives rise to a
new, basic or fundamental taste, which serves so to say as back-
ground to the separate components. There is, however, no need
to make any such assumption. It is an universal rule in psy-
chology that, when sense-qualities combine to form what is called
a perception, the result of their combination is not a sum but a
system, not a patchwork but a pattern. The parts of a locomo-
tive form a system ; the colours of a carpet form a pattern ; in
neither case is there a mere heaping together of materials. The
same thing holds of perception. Hence, just as it would be
absurd to say that the plan of the locomotive is a new bit of steel,
or the pattern of the carpet a new bit of coloured stuff, so is it
wrong to say that the peach-character of a certain taste-blend is a
new taste quality. This character shows us the pattern of the
blend, the specific way in which the components are arranged ; it
is not itself a sensation. — We shall return to the general question
later, in § 104.
It was pointed out in § 29 that there is an intrinsic likeness be-
tween the sensations of taste and of smell. This fact is clearly
recognised in pharmacy. Thus, we are advised to take castor
oil or cod-liver oil in claret or lemonade ; the sour taste corrects
the nauseating or hircine odour. Quinine, which tastes bitter and
has no smell, is corrected by essence of orange peel, which has an
aromatic smell and no taste. In all sorts of children's medicines,
a disagreeable odour is offset by a sweet taste, or a disagreeable
taste by some pleasant odour. The result obtained is, of course,
only partly due to the cancellation of sensations. When a child
has fallen down and hurt itself, we try to turn its attention to
136 - Taste
something else : we tell it a fairy story, or give it a lump of sugar^
and the crying stops. The same principle, of distraction of atten-
tion from the unpleasant to the pleasant, plays its part in these
medicinal mixtures. On the other hand, adults are less suggestible
than children, and the corrections hold for us as for them ; while
an attempt to offset the stench of castor oil, say, by a popular
melody or a comic picture would strike us as laughable. Un-
doubtedly, then, sensations of taste and smell are sufficiently alike
to exert a direct influence upon one another. This conclusion
loses much of its strangeness if we remember that, phylogenetically,
taste and smell are simply two departments of a single chemical
sense, the one differentiated for the reception of liquid, and the
other for that of gaseous stimuli.
Adaptation to tastes is less obvious than adaptation to
odours. It seems that the organ of taste is more resistant,
chemically more stable, than the organ of smell. Apart
from this, however, our attention, in eating and drinking,
is largely taken up with the smell and touch components
of the taste blends. Besides, we usually have at hand the
materials (salt, sugar, vinegar, etc.) for raising the inten-
sity of taste stimuli; we reach instinctively for the salt-
cellar or the vinegar cruet as soon as we miss the taste of
salt or sour. Nevertheless, there are times when the fact
of adaptation stands out clearly enough. An orange that
would taste sweet at the beginning of a meal tastes un-
pleasantly sour if we take it after a sweet pudding. A
stock soup that is at first disagreeably salt gets better after
the first few spoonfuls. If we have the courage to attack
a plate of early strawberries without sugar, we soon grow
accustomed to the acid. — These observations are confirmed
by the results of experiment.
In smell, the effect of adaptation is to increase our
sensitivity for certain qualities, and to reduce or destroy
§ ^6. Mixtnres and Adaptations 137
it for others. In taste, where there are but four quaHties,
the negative result of adaptation is generally confined to
the quality of the stimulus itself : adaptation to bitter
weakens or abolishes the taste of bitter, but leaves the rest
at least as strong as they were before. There are, how-
ever, exceptions to this rule. If the tongue is painted
with a fitting "solution of cocaine hydrochlorate, we lose
first the quahty of bitter, and then that of sweet ; if it is
painted with gymnemic acid, we lose first the quality
of sweet and then that of bitter; in both cases, salt and
sour persist. The action of these substances upon the
end-organs has not been explained. — The positive results
of adaptation must be stated with some reserve, since there
are great individual differences among observers. It seems,
ho'vever, that adaptation to any one of the three tastes
sour, sweet, salt affects the remaining two : a foregone
sour, for instance, enhances a present sweet or a present
salt, and so on.
The sense of taste appears, further, to show phenomena
of contrast, more or less akin to those of vision. A sour
applied to the one side of the tongue brings out, for certain
persons, the taste of a subliminal sweet applied to the
other side. Contrasts may also be obtained, in laboratory
practice, between salt and sour, and salt and sweet. On
the other hand, subliminal bitter, applied at the same time
as sweet, sour or salt, is usually sensed, if at all, as sweet ;
and supraliminal bitter is, from the first, strong and
insistent.
Nothing is definitely known about after-images of taste. Many
sweet stimuli leave a bitter taste in the mouth; but this may be
due to the chemical relationship of the sweet-tasting and the
bitter-tasting substances of which we spoke in § 35. It is note-
138 Taste
worthy that, to many persons, distilled water, an intrinsicaMy
tasteless stimulus, tastes distinctly bitter ; to others it may taste
sour or sweet. Various explanations have been suggested. The
taste may be simply an after-effect of adaptation : the mouth is
never entirely free from particles of food. Or it may possibly
result from the merely mechanical stimulation of the end-organs,
just as a flash of light results from mechanical pressure on the
eyeball. Or, again, it may be an associative process, an idea or,
as it were, an illusion of taste. This and many similar points in
the psychology of taste still await explanation.
§ 37. Theory of Taste. — The description given of the
olfactory cells holds also for the specialised sensory cells
which form the end-organs of taste : they are long, slender
rod-cells, with large nucleus, set among supporting cells
of the same sort as the columnar cells of the olfactory
mucous membrane. The rod-cells are not, however,
irregularly distributed between the supporting cells; they
are gathered together into flask-shaped structures, which
are known as the taste-buds or taste-bulbs. At the centre
of the bulb stands a group of rod-cells, intermixed with a
few supporting cells ; the rod-processes converge periph-
erally to the pore of the bulb. Next comes a wrapping of
supporting or cover cells ; while the outer wall of the bulb
is composed of epithelial cells of special form.
The taste-bulbs occur in greatest numbers in the trenches
surrounding the circumvallate papillae at the root of the
tongue.^ They occur also along the edges of the tongue,
posteriorly in the folds of the regio foliata and anteriorly
in the fungiform papillae ; and at the tip again in the
^ The author uses the Deyrolle model, La langne vue dii cote droit. He
knows of no models that show the sense-organs of nose and tongue in enlarged
vertical section. The models must therefore be supplemented by charts {e.g.i
those of Wenzel's Anaiomischer Handatlas) or lantern slides.
§ 37- Theory of Taste 139
fungiform papillae, the bright red specks which can be
seen standing out from the dull pink of their surroundings.
The central area of the surface of the tongue is insensitive
to taste. In general, the root of the tongue is especially
sensitive to bitter, the tip to sweet, and the middle section
of the edges to sour.
The distribution of the end-organs of taste in man shows great
individual differences. In adult life, functional taste- bulbs are
found on the surface of the tongue, with the exception of a central
area of varying size, and on the soft palate ; less constantly on the
arches and veil of the palate and on the uvula ; rarely on a portion
of the hard palate. They also occur, curiously enough, in the
interior of the larynx and on the epiglottis, regions that are not
normally stimulated by sapid substances. Their presence here,
and on the superior (posterior) surface of the veil of the palate,
accounts however for the sweet taste of inhaled chloroform and
the bitter of inhaled ether (§ 30). In children, the taste-bulbs
extend over the whole surface of the tongue, and are also found in
the mucous membrane of the cheeks, — facts that explain, per-
haps, the childish tendency to take big mouthfuls.
Why the central area of the tongue should lose its sensitivity,
in adult life, is not easy to say. It is clear, however, if we
consider the mechanics of chewing and swallowing, that there
must be a stagnation of sapid liquid at the back and on the edges
of the tongue ; and it is clear that this stagnation is assisted by the
trenches about the circumvallate papillae and by the folds of the
regio foliata. These, then, are the important regions for tasting.
They are more important even than the tip of the tongue, which
merely samples the substances that enter the mouth ; and we find,
as a matter of fact, that insensitivity of the tip not infrequently
coexists with normal sensitivity of root and sides.
The reduction of the organ has analogies in other departments
of sense. In hearing, for instance, the range of sensation is di-
minished ; the highest audible tone is more than an octave higher
fn childhood than in old age. We may suppose that the shortest
1 40 Taste
fibres of the basilar membrane gradually lose their elasticity. In
smell, again, the acuity of sensation is diminished ; children are
much more sensitive to odours than adults, though they do not
appear to have a wider range of qualities. It is possible that, in
the course of years, the olfactory mucous membrane is coated
with minute particles of dust, etc., so that the cells are less easily
stimulated.
The papillae of the same region do not all react in the
same way to gustatory stimuli. Thus, of 39 fungiform
papillae, stimulated with salt, sugar, hydrochloric acid and
quinine, 4 proved to be wholly insensitive, while 31 were
sensitive to sweet, 31 to salt, 29 to sour, and 21 to bitter;
one was sensitive only to sweet, and one only to bitter.
It seems probable, then, that there are four kinds of taste-
bulbs, each one sensitive to a single quality of taste ; and
that all of these, or three, or two, or only one, may be
present in a given papilla.
This hypothesis agrees with the observed facts of taste mixture
and of adaptation, and is also borne out by the pathological cases of
loss of taste ; the ageusia may be complete, or may affect some
qualities more than others. On the other hand, it is impossible
to say whether the distinction of the four classes of taste-bulbs is
absolute. There are no anatomical differences that might help us
to a decision. We must suppose that the substance of the taste
cells has been chemically differentiated, for the reception of the
different forms of stimulus ; but we cannot say whether the special-
isation of function has been carried to the same point in all taste-
bulbs.
It has been suggested that the extreme sourness of the orange
eaten after sweet pudding is due to a contrast of feelings ; the
sour after the sweet is more unpleasant than a sour standing alone.
Even, however, if we grant — and the point is more than doubtful
■ — that contrast between feelings occurs, introspection shows that
the sour quality is itself intensified ; and the explanation is there*
§ 37- TJieory of Taste 141
fore to be sought in the sphere of sensation. The sweet-sensitive
bulbs have been put out of function by adaptation to the sweet of
the pudding, so that the mixed, sweet-sour stimulus affects only
the sour-sensitive bulbs. Hence the orange naturally tastes
sourer than it does under ordinary circumstances, when the sweet
and sour components are able in some measure to offset each
other.
It is more difficult to account for the fact that a sour, etc. ap-
plied to the one side of the tongue brings out the taste of a sub-
liminal sweet, etc. applied to the other side. We may, of course,
challenge the fact itself. Liquids are apt to run on the surface of
the tongue, and it is conceivable that the stimuli used in the ex-
periments spread across the middle line. We know, however,
that the terminal radiations of the n. lingualis which supply the
one half of the tongue extend across the middle to the opposite
half. The two groups of taste-bulbs, though locally distinct, are
thus brought into connection at the periphery by their common
nerve supply. —
Nothing definite is known of the order of development of the
taste qualities. A good deal has been made of the fact that sweets
cloy and bitters whet the appetite, while salts provoke and sours
quench thirst. This, however, is no argument for an original four-
fold differentiation of the sense of taste : appetite is governed largely
by smell. Some authors regard salt as a quality of late develop-
ment, on the ground that the word refers to a particular substance,
while sweet, bitter and sour are general terms, and that children
and uneducated persons often confuse salt with sour. But we find
that many primitive languages have no distinctive word for
bitter ; that some languages use the same word for sweet and salt ;
and that uneducated persons may also confuse bitter and sour !
We have also seen that sour and salt have similar effects upon the
organs of touch (§ 34). In view of the unitariness of the taste-
blends, it is not surprising, then, that the two qualities should be
confused by persons unskilled in introspection.
142 Taste
References for Further Reading
§§ 34~37- W. Wundt, Physiologische Psychologies ii., 1902, 52 ff. ; C.
S. Myers, Taste, in Reports of the Cambridge Anthropological Expedi-
tion to Torres Straits, II., ii., 1903, 186 flf. ; The Taste-names of
Primitive Peoples, in British fournal of Psychology, \., 1904, 117 ; H.
Zwaardemaker, Geschmack, in K. Asher and L. Spiro, Ergebnisse der
Physiologic, II., ii., 1903, 699; W. Nagel, Der Geschmackssinn, in
Nagel's Handbuch, iii., 1905, 621 ff.
CUTANEOUS SENSES
§ 38. The Skin and its Senses. — In popular parlance,
touch is ranked as a fifth sense beside sight and hearing,
taste and smell, and the organ of touch is the skin. Neither
the sense nor its organ is very strictly defined. We may
say, however, that the word skin denotes the whole mem-
branous investment of the body ; it includes not only the
skin proper, but also the red area of the lips, the lining of
the cavities of mouth and nose, the conjunctiva and cornea
of the eye. In so far as this surface is not occupied by
organs of special sense, such as taste and smell, it represents
the organ of touch. Hence the name touch applies to all
the sensations aroused by contact of the bodily surface with
objects of the material world. A thing is hard, soft, warm,
cold, painful to the touch; it is by touch that we distinguish
wet and dry, light and heavy, rough and smooth, yielding
and resistant, sharp and blunt, clammy and greasy, motion-
less and moving.! Exception is made, again, only of those
properties, such as odour and sapidity, that appeal to special
senses. And here, naturally, there is no attempt at analy-
sis ; the sting of pungent odours and the bite of pungent
tastes — qualities that really belong to touch — are referred
to smell and taste themselves.
1 It is, of course, as plain to common sense as it is to psychological obser-
vation that these distinctions are often drawn in terms of sight; we see that
a thing is wet or heavy or in motion. What is now under discussion, how-
ever, is the feel of objects that are actually in contact with the skin.
143
144 Cutaneous Senses
Our experience with timbre and with the blends of smell
and taste puts us on our guard in the present instance ; we
shall not, without question, accept wet and dry, rough and
smooth, etc. as ultimate qualities of tactual sensation.
Instead, however, of working through the list in detail, we
may at once clear up a confusion that inheres in the pop-
ular notion of touch, — the confusion between sensations
from the skin and sensations from the tissues that lie
beneath the skin. Pick up a pen from the table, or give, a
swing to your revolving bookcase, or try to open a window
that has swelled with the rain : in every case you will find
that the sensations from the skin are blended with internal
sensations. Popularly, the whole complex is attributed to
the sense of touch ; psychologically, the two sets of sensa-
tions are different and must be referred to separate senses.
Suppose, however, that the subcutaneous senses are ruled
out : the question still remains whether the skin itself is the
seat of one or of more than one sense. And introspection
favours the second alternative. There is no resemblance,
for example, between the hard smoothness and the chill of
a bit of ice, or between the rough brittleness and the warmth
of new-made toast; we may safely mark off the sense of
touch from the senye of temperature. Nor is there, when
we reflect upon^t; any resemblance between touch and pain.
Indeed, the two kinds of sensation are distinct in time as
well as in quality : if we dip the hand into very hot water,
or take up a very hot plate, we sense the contact appreci-
ably earlier than the pain. It would seem, then, that the
sense of touch must also be marked off from the sense of
pain.
To go beyond this point, we must have recourse to ex-
periment. The surface of the skin must be explored,
§ 38. The Skin and its Senses 145
accurately and minutely, with all sorts of stimuli, — me-
chanical, thermal, electrical, chemical, — and the sensations
which it yields must be described and classified. Much
work of this sort has been done, and the psychology of the
skin, though still unsettled in sundry details, has thus been
put upon a firm basis. —
It is found, first, that the surface of the skin is not
uniformly sensitive. Sensations can be obtained only from
definite spots or points ; the remaining area is insensitive.
The spots are fixed in their position, so that they always
respond in the same way to the same stimulus ; they un-
doubtedly indicate the presence, in the substance of the
skin, of separate sense-organs. It is found, secondly, that
these spots are of four distinct kinds : they furnish the
sensations of pressure, of warmth, of cold, and of prick.
In other words, there are four cutaneous senses, — those
of pressure, or of touch in the narrowest sense, of warmth,
of cold, and of pain. We will take them in order.
What is ordinarily called the sense of touch thus turns out to be
highly composite, — a mixture of the sensations derived from four
cutaneous and from a number of subcutaneous senses. It follows,
of course, that the terms used in current speech to denote qual-
ities of touch are not directly available for psychology. We have
words like pressure, contact, prick, sting, soreness, smart, ache,
and we must somehow make them serve our scientific purpose.
But the selection is not easy, and the same term may, as a matter
of fact, mean different things in different books. Hence it is
important that the descriptions given in these Sections be verified
by actual test : the instruments required are exceedingly simple,
and their manipulation is straightforward. The particular name
will then stand for a special bit of elementary experience, a par-
ticular feel ; the analyses of cutaneous complexes will be analyses
of concrete sense-material, and not a mere play of words ; and, on
I.
146 Cutaneous Senses
the other side, it will be possible by introspective reference to
follow the accounts given by authors who employ a different
terminology.
§ 39. The Pressure Sense. — If with the point of a pencil
you brush one of the hairs that are sparsely scattered over
the back of the hand, you obtain a weak sensation, of
bright quality, which is somewhat tickhsh, and which
though thin and wiry yet has a definite body. This sen-
sation, which we may term the sensation of contact, is
physiologically a weak sensation of pressure. Wherever
the skin carries hair, — that is, over about 95 per cent,
of the cutaneous surface, — the hair-bulb is the organ
of the pressure sense.
Pressure sensations may be studied systematically by
means of the horse-hair point shown in Fig. 20. If you
look at a hair on the
~^ ^^ back of the hand,
you will notice that
the shaft runs ob
liquely into the skin
Fig. 20. Horse-hair point, for exploration of the
cutaneous surface. A piece of horse-hair, about J USt tO wmdwaru Ot
2 cm. in length, is attached by sealing-wax to the 4-Ug Vjpij- directlvOVef
end of a match.
the bulb, lies a pres'
sure spot, which is easily found by a few trials with the
horse-hair point. By applying the horse-hair to the pres
sure spot, with different degrees of pressure, it is possible
to call out the pressure sensations at different degrees of
intensity. You get, first of all, the wiry, bright sensation
of the former experiment. As the pressure is increased,
the sensation too becomes heavier, more solid : at times it
has about it something springy, tremulous, elastic ; at
§ 39- ^'^^^ Pressure Sense 147
times it appears simply as a little cylinder of compact
pressure. Finally, at still higher intensities, the sensa-
tion becomes granular : it is as if you were pressing upon
a small hard seed embedded in the substance of the skin.
The granular sensation is often tinged with a faint ache,
due to the admixture of a pain sensation ; and is sometimes
attended by a dull, diffuse sensation derived from the sub-
cutaneous tissues. It may. however, appear as pure pres-
sure sensation.
If the hairless regions of the skin are explored with the
horse-hair point, pressure spots will be discovered which
yield the same sensations as the hair-bulbs. The organs of
pressure are here to be found in very similar structures,
known as the corpuscles of Meissner.
The end-organs of pressure may be stimulated by pressure from
without, by traction or pull, and by the wrinkling or stretching of
the skin itself. They respond, that is, to any decided change of
the local level of pressure, whether the change is positive or
negative, rise or fall. They do not, all alike, furnish the graded
series of sensations which we have just described, but are, so to
say, tuned to different intensities of stimulus, so that a pressure
v/hich evokes the granular sensation at one spot may call out only
the weak, bright sensation from another. There is, however, no
further difference in the nature of their response ; all the sensa-
tions of pressure belong to this single series.
Pressure spots are found over practically the whole extent of the
skin. Their distribution differs in different regions. On the
average, there are about 25 of them to the square centimetre ;
but this number may drop, for instance, to 7 on the upper arm,
and may rise to 300 on the scalp.
Adaptation of the pressure sense is a matter of every-
day experience. So long as we sit still, we are hardly
aware of the pressure of our clothes ; and the man who is
148 Cutaneous Senses
looking for the spectacles that he carries on his forehead
has become a stock figure in the comic papers. The posi-
tive after-images of pressure ordinarily escape notice, since
attention turns rather to the object arousing the sensation
than to the sensation itself. They may, however, be in-
tensive and of long duration ; the deformation of the skin
persists awhile, after the removal of the stimulus, and this
after-affect of stimulus shows itself in a continuance of
sensation.
It seems, at first, hardly credible that the end-organs of pres-
sure should not be differentiated for the reception of different
kinds of stimuli. When we think of the great variety of our tactual
experience, and when we remember further that the same stimulus
has markedly different effects if applied to different parts of the
skin, we are almost forced to believe in a number of qualitatively
distinct sensations. Nevertheless, the verdict of experiment is de-
cisive here, as it was decisive in the somewhat similar case of taste.
And we must not forget the facts on the other side. First, the
stimuli that normally affect the skin are areal stimuli, appealing to
a group of diversely tuned pressure organs ; and the texture of the
skin itself, and the nature of the underlying tissues, vary from place
to place. There is, then, every chance in ordinary experience for
typical differences in the intensity and the temporal course of pres-
sure sensations. Now the sensations which we have termed contact,
pressure, and granular pressure, although they are evoked by differ-
ent intensities of the same stimulus and are on that account usually
considered as different intensities of the same quality, are at least
as distinct as red and pink, or yellow and orange ; and if we may
not call them psychological quahties, we must at least say that they
do the same service for touch that true qualitative differentiation
does for other senses. Secondly, the greater number of normal
stimuli affect other organs, cutaneous or subcutaneous, besides
those of pressure. Hence most of our tactual experience does, in
strictness, consist of more than one quality, because it derives from
more than one sense. Thirdly, as has been said above, the atten-
§ 40- TJie Temperature Senses 1 49
tion is generally concerned rather with the stimulating object than
with the sensation which it excites. Here touch borrows from
sight in much the same way as taste borrows from smell ; visual
characters of form, size, texture, etc., are so firmly associated to
the feel of the stimulus that the skin gets the credit of a good deal
of work done by the eye.
We shall have occasion, in § 50, to analyse some of the com-
moner tactual complexes. In the meanwhile, this general state-
ment of the various factors which enter into them may lessen the
strangeness of the experimental results.
§ 40. The Temperature Senses. — If you draw the rounded
point of a lead pencil slowly and lightly across the back of
the hand, or, better, across the surface of the closed eye-
lids, you will get, here and there, definite flashes of cold.
There is a continuous sensation of pressure, due to the
direct or indirect stimulation of pressure spots by deforma-
tion of the skin ; but this continuum is dotted by sensations
from the cold spots.
For systematic work, it is best to use a hollow point of
metal, which can be kept at a constant temperature by the
passage of a stream of water. The
average natural temperature of the
healthy skin may be put at about
33° C.i With the metal point held
at I2°— 15° C, one obtains the char-
acteristic sensation from the cold ^p
spots, and with the point at 37°-40° ^'''- ".'• Apparatus for the in-
'■ -^ >-'/ -r vestigation of the temperature
C, the sensation from the warm senses, c, cold; w, warm
spots. Both are larger, more ex- ^"'"^= />. metal point.
tended than the sensation of pressure. The cold seems to
lance down from above ; it is set up at once in its full in-
1 Degrees C. may be converted into degrees F. by the formula § C. + 32 = F.
150 Cutaneous Senses
tensity; it might be described as a solid point of cold. The
warm often seems to well up from beneath ; it is thinner,
more diffuse than the cold, and comes gradually to its full
intensity.
The end-organs of temperature may be stimulated either from
without or from within : from without, by the application to the
skin of a cold or warm object, by radiant heat or the proximity of
a cold body, by the action of substances like mustard, pepper,
alcohol, menthol ; from within, by the organic changes occurring
in fever, in extreme fear, in an access of
shame, etc. They respond to any decided
change of the local level of temperature, the
cold organs if the change is negative, and the
warmth organs if it is positive. Like the pres"
sure spots, they are tuned to different inten-
sities of stimulus : some warm spots will give
only a lukewarm sensation at 40° C, and
Fig. 22. Cold and warm gQ^^jg q^q\^ spots only a cool sensation at 12°
spots on an area (nat- ^ _, ,..,.„ ,
urai size) of the back C. There are no qualitative differences under
of the hand. The dots the general headings warm and cold,
represent the cold, the Qq\^ spo|-g ^lay be found, without diffi-
circles the warm spots. 1,111 r i 1 -i
— M Br 88 culty, by help of a lead pencil or a carpen-
ter's spike. The warm spots are less easy of
determination : partly because the warmed point quickly cools,
and partly because the sensations themselves are duller and less
insistent than those of cold. This difference of character makes
it probable that the warmth organs are deeper seated than the cold
organs. The latter may perhaps be identified with the terminal
bulbs of Krause, and the former with the corpuscles of Rufifini.
Temperature spots are found, like pressure spots, over practi-
cally the whole extent of the skin. The distribution of the three
sets of organs differs in different regions. On the average, there
are about 13 cold spots and 2 warm spots to the sq. cm.
It is a curious fact that the cold spots, which are not affectt(J
by the stimuli ordinarily used in the determination of warm spots,
•
0. ^ o|
«
• ^ <
•
♦ ••^*
«
#*c.o .'
♦
«
•
_•_
Q
§ 40. The Temperattire Senses 151
give a clear sensation of cold if stimulated by temperatures above
45° C. This has been termed the paradoxical sensation of cold.
Why the end-organs of cold should suddenly respond, at this
particular temperature, is not known. Paradoxical sensations of
warmth, — sensations aroused at the warm spots by a very cold
stimulus, — have never been observed in the normal subject. It
may be that they do not occur ; or it may be that the end-organs
are too deeply set in the skin to be reached by a punctiform cold
stimulus. In pathological cases of anaesthesia to cold, the patients
will occasionally declare that ice, applied to the skin, feels warm.
It is, however, doubtful whether such statements do not rest upon
a confusion.
If an areal stimulus of 45° C. or over is applied to a part of the
skin which includes both cold and warm spots, we have the percep-
tion of heat. In general, this appears as a simple and unana-
lysable quality. It may, however, be analysed by a suitable ex-
perimental procedure. Let the stimulus be set, say, at 40° C, and
gradually increased. At first we get only the sensation of warmth.
With a temperature of some 45°, the paradoxical cold sensation
also appears, and grows stronger and stronger as the rising
temperature affects more and more of the cold spots. Under
these conditions, it is possible, with practice, to distinguish the two
component sensations, though each, as the attention turns to it,
seems to be coloured by the other.
The temperature senses have a wide range of adapta-
tion. In the winter we grow accustomed to cold, and in
the summer to warmth, so that a warm winter's and a cool
summer's day are judged by very different standards.
Water that at the first plunge seems unpleasantly cold,
and a room that strikes us on our entry as oppressively
hot, soon become indifferent ; we are even surprised at the
comments of later arrivals.
Intensive stimuli, of brief duration, give a positive after-
image. A long-continued and intensive cold stimulus is
152 Cutaneous Senses
also followed by an after-sensation of cold. The removal
of a continued warm stimulus, on the other hand, leaves a
sensation of coolness.
It has been found possible, by experiment, to adapt the fingers
to a temperature as low as 11° C, so that a stimulus of 12° feels
warm, and again to a temperature as high as 39°, so that a slightly
lower stimulus feels cold. If the skin is cooled by contact with
an object which is kept constantly at 10°, the paradoxical cold
sensation will be aroused by a stinuilus of 35°, instead of the nor-
mal 45°. The following rough experiment gives striking proof of
adaptation. Prepare three bowls of water, cold, lukewarm and
warm. Hold the hands in the lukewarm water until this feels
alike to both. Now place the one hand in the cold, the other in
the warm water ; let them remain for i min. Finally, dip both
hands into the lukewarm water : it will seem decidedly cold to the
warmed and decidedly warm to the cooled hand.
The after-image of cold following long-continued and intensive
cold stimulation is a little paradoxical ; we should rather expect an
after-sensation of warmth. The cold may, in fact, be the para-
doxical cold sensation, aroused in this case by the rush of warm
blood to the cold-adapted organs.
§ 41. The Pain Sense. — If you hold the shaft of a pin
loosely between the forefinger and thumb of the right hand,
and bring the point down sharply but lightly upon the back
of the left hand, you will sense first the impact itself, and
then, after a brief but noticeable interval, something finer,
like a prick or a thrill. This second sensation is due to a
moderate stimulation of the specific organ of pain.
For accurate results, the skin must be shaved, and
softened with soap and water ; and the surface must be
explored by help of a very delicate hair-point. The sensa-
tion obtained from the pain spots then occurs in three
stages : first, as a bright, itchy sensation ; secondly, as
§ 41. The Pain Sense 153
prick or wiry thrill; and thirdly, as punctiform pain. It
is always delicate and lively, and has less body than the
sensation o£ pressure.
The end-organs of pain may be stimulated, from without, by
mechanical, thermal, electrical or chemical means. They respond
most easily to chemical stimulation, as, for example, to acid
Fig. 23. Pressure and pain spots on an area (here multiplied by i6) of the
back of the hand. There are 2 pressure spots and 16 pain spots. The latter are
marked as circles, the former as triangles ; the hairs to which the pressure spots
belong are indicated by the heavy lines and semicircles. — M. von Frey, 1896.
dropped upon the cutaneous surface or to intracutaneous injection
of salt solution. They may also be stimulated from within, by the
chemical action of substances produced by inflamed tissue. Like
the other cutaneous organs, they are tuned to different intensities
of stimulus.
Pain spots occur, apparently, over the whole extent of the skin
proper. Their distribution does not coincide with that either of
the pressure or of the temperature spots. On the average, there
154
Cutaneous Senses
seem to be lOO to 200 pain spots to the sq. cm. With the excep
tion of lips, teeth, and tip of tongue, the mouth cavity shows but
little sensitivity to pain ; a large area of each cheek is entirely free
from pain spots. — - The organs of pain are, perhaps, to be found in
the free intraepithelial ne:ve-endings.
The sensation of pain is often blended with sensations of pres-
sure and temperature. The following table gives the facts for the
temperature senses :
Warmth Organs
Cold Organs
Pain Organs
Bitter cold ■•
+
+
Cold, cool
+
Lukewarm, warm .
+
Hot ... .
+
+
Burning hot .
+
+
+
The sensation of prick or pain resembles the sensation
of warmth in its slow and gradual rise to full intensity. It
resembles those of pressure and cold in its persistence after
the removal of stimulus ; the prick aroused by the impact
of the pin on the back of the hand may last, as positive
after-image, for 10 sec. or more.
The pain sense does not appear to show the phenomenon
of adaptation. If a pain spot is repeatedly stimulated, the
sensation recurs, and presently the surrounding area be-
comes sore and irritable. It is true that, in everyday
life, we learn to disregard pains of moderate intensity,
such as muscular soreness or a continued slight rheuma-
tism ; but we ignore them, as we ignore distracting noises,
because the attention is occupied with other topics, not
because they fade out with time.
The dense distribution of the pain spots, the qualitative differ-
entiation of their response to stimulus, and the long duration 0/
§ 42. Theory of the Cutaneous Senses 155
the after-image, account in general for the experiences of cutting,
burning, scratching, abrading the skin. Whether they account in
detail for all our experiences of cutaneous pain is still an open
question. We said above that the granular sensation of pressure
is often tinged with a faint ache. If, now, a fold of the skin — ■
say, the fold between the fingers — -is grasped firmly with a pair
of forceps, the same dull ache appears. The pain in these cases
is unlike any superficial pain, but like that of a severe acid burn.
It may be, then, that there is another set of pain organs, deeper
seated in the skin, whose characteristic sensation should be de-
scribed as an ache. — The pains derived from subcutaneous tissues
are discussed in § 56.
All pains at high intensities are extremely unpleasant or dis-
agreeable. It is therefore only natural that, in ordinary speech,
we refer to any very disagreeable experience as painful. But it
must be distinctly understood that the sensations proceeding from
the pain organs are not necessarily painful, in the sense that they
are necessarily disturbing or unpleasant. The bright, itchy sensa-
tion and the sensation of prick occur as often as not in indifferent
or pleasant complexes ; it is only in the third stage, that of puncti-
form pain, that the sensation hurts. And even here, the pains
aroused by minor injuries to the tissues seem in many cases to be
insistent, interesting, rather than actually painful.
§ 42. Theory of the Cutaneous Senses. — We have seen
that the end-organs of the pressure sense ^ are the hair-
bulbs and the Meissner corpuscles. How are these organs
affected by pressure stimuli .'' Under what precise condi-
tions are they thrown into function }
If a point is set down upon the skin, the pressure is
greatest directly beneath the point, and rapidly decreases
1 The author knows of no skin-model that is satisfactory for psychological
purposes. He uses the three DeyroUe models (^Coupe de la peau de Vinte-
rieur de la main. Coupe de la peati 7nontrant I' organisation d^un folliciili
pileui:, and Cotcpe de Vextremite d^iin doigi), upon which the end-organs men-
tioned in the text have been painted.
156 Cutaneous Senses
with increase of distance from it, — whether the distance
be measured laterally, upon the surface of the skin, or ver-
tically, into its substance. In other words, the point coin-
cides with the maximum of what we may call a gradient of
pressure. The gradient will be steep or gentle, according
as the stimulus is strong or weak ; it will take shape slowly
or quickly, according as the point is applied gradually or
with sudden impact.
Experiments show that the quick formation of such a
pressure gradient is the adequate stimulus to the pressure
organs. They show also that the gradient may be positive
or negative ; the pressure spots respond to pull as well as
to pressure. It is not easy to say just what changes occur
in the skin as the gradient is formed. There must, how-
ever, be a redistribution of the liquid contained in the
tissues, and there may be local concentration ; probably^
therefore, the mechanical effect of pressure upon the sur-
face of the skin is translated into a chemical action upon
the end-organs.
Reference to the pressure gradient enables us to explain two
observations which have aroused much discussion among psychol-
ogists. If the hand is dipped into water, or even into mercury, no
pressure is sensed over the immersed area, but there is a distinct
ring of pressure sensation at the place of emergence. The reason
is, evidently, that here and here only does a noticeable pressure
gradient occur. Again, if two objects of the same weight but of
different size are laid successively upon the resting skin, the smaller
appears the heavier. The reason is that the pressure gradient is
steeper for the smaller, and more gentle for the larger object.
No theory of the temperature senses can as yet be
offered ; we have not even identified, with certainty, the
terminal organs through which the sensations are aroused
§ 43' Tickle and Itch 157
If, as seems probable, the organs of the pain sense are
represented by the free nerve-endings of the epidermis, we
have to account for the fact that the deeper-lying pressure
spots are more readily stimulated by contact with material
objects than the superficial pain spots. The reason lies in
the nature of the cutaneous tissues. The epidermis is hard
and inelastic, like a board ; the cutis is soft and elastic, like
sponge rubber. Hence, under ordinary circumstances, the
stimulus is transmitted to the cutis, while the epidermis is
not affected. When the epidermis is pierced by a iine point,
or the dead cells of the outermost layer are cleared away
and the tissue softened by soap and water, the superficial
pain organs respond earlier than the organs of pressure.
§ 43. Tickle and Itch. — We described the sensation of
contact as being somewhat ticklish, and the weak sensation
of prick as being itchy. It would seem, then, that our
everyday experiences of tickling and itching might be
referred to a diffuse stimulation of the pressure spots and
pain spots.
We get tickle, as a matter of fact, by brushing lightly,
as with a feather, over a field of hairs. But we also get it,
much more insistently, by brushing over a hairless surface,
such as the red area of the lips, the palm of the hand, or
the sole of the foot. The sense quality appears to be the
same in the two cases. It is not quite easy to see how the
pressure spots in the hairless regions can be stimulated by
a contact which is too light to deform the skin : possibly,
however, the application of the stimulus changes the pres-
sure of blood in the superficial capillaries, and the nerve-
endings are thus indirectly affected. The tickle that oc-
curs when you are seized under the arms, or clutched on
158 Cutaneous Senses
the knee, appears deeper-seated than the tickle produced
by brushing the skin.
Itching may be referred with some confidence to the
organs of cutaneous pain. It is the result of certain skin
diseases, of superficial wounds and burns, of the bite of
insects, etc., — that is, of conditions by which the nerve-
endings of the epidermis are directly affected.
It is often stated, as a paradox, that tickling makes us laugh,
and is therefore pleasant, while it also makes us try to get away,
and is therefore unpleasant. Such a statement is, however, far too
simple for the facts. Tickling may be either pleasant or un-
pleasant, according to the region of the skin affected, the mode
of application of stimulus, and the mood of the person tickled.
Thus, it may be said in general that tickling on the sole of the
foot or at the hairy orifices of nose and ear is distinctly unpleasant,
while tickhng on the palm of the hand or under the arm-pits is
rather pleasant. Yet the flexing of the foot may change the un-
pleasant into a pleasant experience, and tickle on the palm may
be almost unbearably disagreeable. The arousal of laughter, again,
is exi^remely capricious. We can tickle ourselves, and get pre-
cisely the same sensations as when we are tickled by some one
else ; but we never make ourselves laugh. Nor can any rule be
laid down as to the provocation of laughter by a certain form of
stimulus, by stimulation of certain areas of the skin, etc. What
holds of one person does not hold of another, or of the same per-
son in a different mood. And the movements of escape are
equally variable : s. child may ask to be tickled to-day, and may
beg not to be tickled to-morrow ; a part of the body that is
pleasurably ticklish in one child may be unpleasantly ticklish in an-
other, and so on.
All this variety of detail means that the tickle-stimulus does not
act simply upon the sense-organ, as a colour-stimulus acts upon
the eye, but that it serves as the trigger, so to speak, to release
certain inherited mechanisms of our nervous system. These
mechanisms are, however, themselves liable to modification 01
§ 43- Tickle and Itch 159
arrest from higher nervous centres, so that they are not touched
off inevitably or with uniform result. The reason for such a
physiological arrangement can only be guessed at. It is signifi-
cant that the areas which are especially ticklish are highly vulner-
able : in nearly all of them some important structure, such as a
large artery, is close to the surface ; and where this is not the
case, as in the sole and the palm, an injury, even if not serious,
is seriously disabling to the organism. It may be, then, that tic-
kling represents a very old form of race-play, the play of combat.
The movements of attack and of defence are playful forms of
fighting, and the laughter shows that the whole affair is a friendly
game. This interpretation is, of course, speculative. Neverthe-
less, it accounts on the ground of utility for the persistence of the
motor responses to tickling, while it also leaves room for their
variety and uncertainty in our own case. On the whole, it prob-
ably comes as near the truth as, in the absence of exact data, we
can expect any theory to bring us.
References for Further Reading
§§38-43. A. Goldscheider, Gesammelte Abhandlungen, i., 1898;
C. S. Sherrington, Cutaneous Sensations, in E. A. Schafer's Text-book
of Physiology, ii., 1900, 920 flf. ; J. Sully, An Essay on Laughter, 1902 ;
M. von Frey, Vorlesungen Yiber Physiologie, 1904, 308 ff. ; T. Thunberg,
Druck-f Tempe7'atJir- 7ind Schtnersempfindnngen, in NageFs Handbuch,
iii., 1905, 647 fF. ; H. Head, W. H. R. Rivers and J. Sherren, The
Afferent Nervous System from a Nezv Aspect, in Brain, xxviii., 1905,
99 ; L. Torok, Ueber das IVesen der fieckempfindting, in Zeitschrtft f.
Psychologie, xlvi., 1907, 23 if. ; E. Murray, A Qualitative Analysis of
Tickling: its Relation to Organic Sensation, in American Jourttal of
Psychology, xix., 1908, 289 ff.
KINAESTHETIC SENSES
§ 44. The Kinaesthetic Senses. — In passing from the
special senses to the group of organic sensations, we
naturally turn first to the internal senses which are com-
monly included in the sense of touch. These senses have
their organs in the motor apparatus of the body ; they
are set in function by bodily movements ; they enable
us, without help from the eye, to judge of the position
and movement of our limbs. Hence they have been
termed, collectively, the kinaesthetic senses.^
The nature of the tissues which make up the motor apparatus,
and the distribution of sense-organs within them, may be under-
stood from the following illustration. Think of two long bones,
which form a ball and socket joint, and of a single muscle, which
passes across the joint and is attached by its tendons to the shafts
of the bones. The opposed surfaces of the joint are covered
with cartilage. This thins out, at its margin, into a layer of
vascular connective tissue, the periosteum, which extends over
the entire shaft. The joint is enclosed in a capsule of ligament ;
the inner surface of the capsule and the inner faces of the articular
cartilages are lined with synovial or lubricating membrane. The
muscle is composed of bundles of muscle fibres ; it is divided
into compartments by fascial or sheathing tissue, and is invested
by a thicker sheath of the same material. The tendons are
strong, fibrous cords, directly continuous at the one end with
the fascia of the muscle and at the other with the periosteum
of the bone.
1 The term was suggested by H. C. Bastian. See The Brain as an Organ
Of Mind, 1885, 543.
i6»
§ 44- '^l^^ Kinaesthctic Senses i6l
The muscles and tendons contain peculiar end-organs, known
respectively as the muscle spindles and the spindles of Golgi.
Pacinian corpuscles, or similar structures, have been found in
fascial tissue, in ligament, in the synovial membrane, and in the
periosteum of certain bones. Sensory nerve-endings occur also
in the substance of the bony tissue. The sensitivity of the bone
extends, apparently, up to the margin of the articular cartilages ;
whether it extends farther, so that the surface of the joint be-
neath the cartilage is sensitive, we do not know.
In everyday life, the sensations of the kinaesthetic
senses occur only as factors in what we may call touch-
blends. In all such experiences as lifting, holding, grasp-
ing, pushing, pulling, moving, handling, writing, playing
a musical instrument, tying a knot, they are fused or
blended with sensations from the skin. It is not sur-
prising, then, that the skin should itself come to be looked
upon as an active or motor organ, and should be credited
with sense-qualities which are really derived from the
deeper-lying tissues. The very fact that the motor ap-
paratus is covered by the skin, that under normal con-
ditions it cannot be separately stimulated, favours this
confusion. Besides, the kinaesthetic sensations are, in
general, very like the cutaneous ; in one case, indeed,
they seem to be indistinguishable from cutaneous pressure.
For this reason, some psychologists still describe them as
sensations of internal touch.
Nevertheless, the distinction between the sensitivity of
the skin and that of the underlying tissues was drawn very
early in psychology. Aristotle seems to have had an
inkling of the difference, and it was clearly recognised
in the sixteenth century.^ Modern writers have usually
1 Aristotle appears in general to bracket cutaneous and kinaesthetic sen-
sations together, under the heading of touch. However, he says, in the His'
M
1 62 Kinaesthetic Senses
ascribed the deeper-seated sensations to the muscles, and
the muscular sense has accordingly been added, as a sixth
sense, to the list of sight, hearing, taste, smell and touch.
We have learned, however, that this list is itself incom-
plete ; and recent experiments, coupled with the study
of pathological cases of partial anaesthesia, show that
the muscles are but one, and that by no means the most
important, of a number of sensitive tissues.
§45. The Muscular Sense. — To bring out the special
quality of muscular sensation, we must find a method of
stimulating the muscle alone, that is, independently of
skin, tendon and joint. The best way is to lay out the
arm on a support ; to render the skin and the subcutaneous
connective tissue anaesthetic by cocaine injection or ether
spray ; and then to press down upon the body of the
muscle. The result is, first, a sensation which is described
as dull, dead, diffuse ; it is simple in nature, cannot be
named, but suggests areal pressure upon the skin. With
increasing intensity of stimulus, the sensation takes on a
dragging character : sometimes there seems to be a hard,
dead lump in the muscle, sometimes the muscle fibres
seem to be ground or rolled against one another. The
general impression is that of a tired, overworked limb.
Finally, the dragging sensation becomes sore, achy, and
the whole experience passes into dull pain.
The same series of sensations appears if a muscle is thrown into
forced contraction by the electric current. Indeed, after a short
io)'y of Animals : "The sense of touch vesicles in the simple parts, as in the
flesh; . . . the capacity of action resides in the compound parts, as . . . the
power of locomotion in the feet or wings." For an historical discussion of
the subject, see T. Reid's Works, ed. by W. Hamilton, ii., 1872, S67, note IL
§ 46. The Tendinous Sense 163
practice in tlie laboratory, it is easy to identify the different stages,
by introspection, in everyday life.
As the possible seat of muscular sensations, we have the fascial
corpuscles and the muscle spindles. It is probable, from what
we know of the joints (§ 47), that the corpuscles mediate a sort
of pressure sensation. We may, then, provisionally, ascribe to
them the dull, diffuse sensation, and to the spindles the dragging,
sore, tired sensation that ultimately becomes pain.
§ 46. The Tendinous Sense. — In all cases of severe or
prolonged muscular work, we get a sensation which can-
not be identified with any one of those derived from
muscle. Where we are ourselves active, as in wrestling,
pushing, pulling, lifting, we term it effort or exertion ;
where we are passive, as in supporting a weight, or stand-
ing for a long time on one leg, we term it strain. The
quality is the same throughout.
This sensation of strain appears to come from the ten-
dons, and to have its organs in the spindles of Golgi.
Like the dragging sensation from the muscles, it passes
over, at high intensities of stimulus, into dull pain.
Tendinous tissue is, as we have said, directly continuous with
the muscle fascia and with the periosteum. It is therefore im-
possible to isolate the tendon for separate stimulation. In seek-
ing to discover the nature of tendinous sensation, we can only rule
out the qualities that come from skin, muscle and joint, and note
what is left. The remainder turns out to be the sensation of
strain. Having reached this result, we find it confirmed by the
intimate connection of strain with muscular fatigue and muscular
pain, and by the tendency to localise these sensations together in
the substance of the Hmb. —
.. There are, further, certain experiences which seem to depend
upon the cooperation of end-organs in muscle and tendon.
When we are feeling particularly well, we move lightly, springily,
164 Kinaesthetic Senses
jauntily ; and if we try to analyse the feeling, we notice light,
thrilling sensations, which appear to come from the skeletal mus-
cles, and are most marked in the calves of the legs. Again, if we
are feeling excited, and try to analyse that feeling, we soon come
upon similar bright sensations, most marked in the thighs. Now
corpuscles, of the same kind as those of the muscle fasciae and
the capsules of the joints, are found in the sheaths and substance
of the tendons, and sparsely in the substance of the muscles.
They occur also in the sheaths of certain nerve-trunks, and near
large vessels. In a word, they represent a widely distributed type
of sense-organ. Since the sensations mentioned above are also
distributed over a wide area, and since they closely resemble the
sensations set up by movement in the joints, we may suppose
that they are due to a weak stimulation of the corpuscles.
Against this conclusion stands the dull, dead character of the
sensation which is produced by pressure on the body of the mus-
cle, and which we have ascribed to the corpuscles of the fasciae.
It must, however, be remembered that the stimulus here employed
is both unnatural and severe. As the pressure spots of the skin
give first a bright sensation of contact, and then a sensation of
more soHd pressure, so may these corpuscular end-organs give
first the light, thrilling experiences of health and excitement, and
at higher intensities of stimulus something that is duller and
harder.
§ 47. The Articular Sense. — If the hand is moved slowly
to .and fro at the v^rist with fingers outspread, while the
eyes remain closed, we have, besides the visual image of
the movement, various sensations from the skin. There
is probably a sense of coolness over the palm ; and there
are waves of diffused pressure, now across the knuckles,
now down the front of the forefinger, now on the sides of
the fingers, as the tension of the skin changes. Subci^-
taneous sensations from the body of the hand, if re-
marked at all, are exceedingly faint : there is no trace of
§ 47- ^-^^^ Articular Sense 165
strain, and hardly a trace of muscular sensation. We
notice, however, a rather massive complex of sensations in
the wrist-joint, whose quality is not distinguishable from
that of cutaneous pressure.
These sensations come, predominantly, from the end-
organs of the articular ligaments. The general impres-
sion is the same as that produced by moving the linger
over a greasy surface of indifferent temperature ; or, bet-
ter, by smearing a finger of the right hand with vaseline
and turning it in the loosely closed left hand. Sensations
of like quality are derived from the sensitive surfaces of
the bones, around or beneath the articular cartilages. They
may be brought out by pressing a finger strongly down
into its socket, and in this position moving it back and
forth.
The corpuscles are distributed most thickly on the flexor side of
the articular capsule, and it is easy to see that they must be stim-
ulated by the tensions and compressions of the tissue as the limb
is moved. The corpuscles of the synovial membrane and of the
ligaments that, in some joints, run between the articular surfaces
may be stimulated either by movement or, like the surfaces of the
bones, by pressure and counterpressure within the joint itself. —
The last few sections have raised a question which recurs
throughout the study of organic sensation : the question whether
we may assume that every sensory end-organ is an organ of sense.
It seems natural to reply in the affirmative. If the hair-bulbs,
and Meissner's corpuscles, and the free nerve-endings of the
epidermis, and such and such other structures furnish sensations,
why not all the rest of them ? Nevertheless, a decision is not easy.
In the skin, for instance, there are many such organs — Rufifini's
plumes, Tomsa's knots, Merkel's cells — which cannot with cer-
tainty, even with probability, be brought into connection with
sensations. As histological research advances, more and more of
these structures are brought to light. Either they are, in large
1 66 Kinaesthetic Senses
measure, mere reflex mechanisms, or they are sense-organs which,
despite differences of form, yield the same quahty of sensation.
The second of these hypotheses is, perhaps, the more probable.
Differences of form may be attributable to local differences of
nutrition and of the conditions of development at large ; indeed,
several of the corpuscles figured by histologists seem to be related
as terms of a single developmental process.
§ 48, Movement and Position, Resistance and Weight.—
We are able, with closed eyes, to tell pretty accurately in
which direction a limb moves and how far it travels. We
are also able, as a rule, to describe the position of an un-
moved limb. These perceptions of movement and position
are based upon the articular sensations discussed in the
preceding section.
It seems clear, on general principles, that the perception of
movement cannot come by way of muscle and tendon. For
movements of equal range and of like direction may be made with
the limb bent in or stretched out, heavily weighted or held free :
that is to say, similar movements may involve very different de-
grees of muscular and tendinous sensation. It is hardly possible
that a reliable set of perceptions of movement could be built upon
so instable a foundation. Moreover, experiment shows that we
estimate passive movements as correctly as active ; it makes no
difference whether the arm, for instance, is laid on a rest and
moved by someone else or whether we hold it out and make the
movement for ourselves. The perception of movement is, then,
as a matter of fact, independent of changes in muscle and tendon.
There is also positive evidence to connect the perception of
movement with the joints. In the first place, skin, muscle and
joint may be rendered partially anaesthetic by faradisation, that is,
by the repeated passage of electrical shocks through them. If,
now, the skin and muscles are thus treated, the perception of
movement is not affected ; if, however, the joints are anaesthetised,
it is very considerably impaired. Secondly, there are diseases
§48. Movement and Position, Resistance and Weight 167
which bring with them anaesthesia of the skin, or of skin and
muscles together, or of the whole surface and substance of a limb.
In the former, the perceptions of movement and position are nor-
mal ; where the muscles are involved, they are not inadequate ;
but where the joints are also insensitive, the patients can neither
adjust their movements nor judge of the position of the diseased
limb without the aid of sight.
It may be objected to this view that we are aware of certain
movements — movements of tongue, hps, eyeballs — in which the
joints are not concerned. That is true. It must, however, be
remembered that tongue and lips play against fixed structures, the
roof of the mouth and the teeth ; and it is, in fact, mainly by ref-
erence to these that their movements are estimated. One has
only to hold the tongue free in the mouth cavity, and to watch its
movements in a mirror, to be convinced that an organ which has
only skin and muscle to rely upon is exceedingly obtuse as regards
the perception of movement. With the eye things are different.
The eyeball turns on the fatty cushion of the orbit very much as
the ball of a joint turns in its socket. We thus get a true percep-
tion of movement of the eyes, although the sensations are dulled
and weakened by the yielding nature of the tissues. —
We have spoken throughout of the perception of movement :
there is no such thing as a specific movement sensation. What
happens is that a complex of articular sensations becomes asso-
ciated, with constant repetition, to a visual perception of a move-
ment. The association is, in course of time, so firmly established
that the occurrence of the articular complex calls up, even with
closed eyes, a visual idea of the displacement of the limb. Posi-
tion is perceived in the same way. When a Hmb comes to rest,
there is a certain final distribution of tensions and compressions
in the ligaments of the joints, which gives rise to a complex of
sensations. So long as these persist, we can call up a visual idea
of the position of the limb. When they fade out, by adaptation,
we lose the visual idea along with them, and can recover the per-
ception of position only by making movements which bring the
articular end-organs into renewed function. We have all had the
experience, on waking from a sound sleep, of a blank loss of arm
1 68 Kinaesthetic Senses
or leg : for a moment, we cannot imagine where the thing is. A
slight shift of position puts us to rights again.
When we lift a weight, we are working against the force
of gravitation; when we overcome a resistance, we are
working against mechanical forces in some other direc-
tion. The perceptions of weight and resistance seem to
be of the same order, psychologically, as their objects are
of the same order physically. Their organs are, in the
first instance, the sensitive surfaces of the joints. When
strain or exertion is involved, the spindles of the tendons
also come into play.
The perception of weight may be either passive or active. If
the arm is laid out upon a table, and a heavy object placed upon
the skin, we have the passive perception : the organs affected
are the pressure spots of the skin, and the Pacinian corpuscles of
the subcutaneous connective tissue and the muscle fasciae. Under
these circumstances, our discrimination of weight is inaccurate ;
it corresponds to the perception of movement by tongue or hps.
When the weight is lifted, and the perception thus becomes ac-
tive, discrimination is much more delicate ; it corresponds to the
articular perception of movement.
Some psychologists separate the perception of weight from that
of resistance, and refer the former to the tendons and the latter
alone to the articular surfaces. And indeed it seems natural, at
first thought, to say that the pull of a weight must draw the sur-
faces of the joint apart, while the resistance of an inert body must
jam them together. Really, however, the very fact that the arm
is braced and set for lifting means that it is strongly bound at
the joints ; and the heavier the weight to be raised, the greater is
the articular pressure. Moreover, it makes little difference in the
perception of lifted weights whether the arm is flexed or ex-
tended, whether the hand grasps the object loosely or tightly;
so that the perception is, at least in some degree, independent
of the state of the tendons.
§ 49- '^^^^ Alleged Sensation of Innervation 169
Again, some psychologists hold that the sensitive surfaces of
the bones play a large part in the perception of movement. The
surfaces must, of course, rub against each other as the Hmb is
moved ; and we know that patients who suffer from anaesthesia
of skin and muscles perceive movement and position more accu-
rately when the joints are pressed together than when they are
pulled apart. On the other hand, the rubbing can be but hght
in the case of passive movements, where we are relieved of the
weight of the limb. And it is possible, in the pathological con-
ditions, that the sensations from the bones serve, by adding to
the sum of articular sensation in general, simply to call the pa-
tients' attention to the diseased limb, without contributing directly
to their perception of its movement. The strongest bit of nega-
tive evidence lies, however, in the fact that we may get the same
perception of movement with very different accompaniments of
resistance. —
Here as before it is important to remember that we are deal-
ing not with sensations but with perceptions. In movement, we
have a complex of sensations from the joint capsule, along with
varying sensations from skin, muscle, tendon and articular sur-
face. In weight and resistance, we have a complex of sensations
from the articular surfaces, coloured at high intensities of stimulus
by tendinous strain, along with varying sensations from skin,
muscle and joint capsule. There is no specific sensation of
weight or of resistance.
§ 49. The Alleged Sensation of Innervation. — We have
so far taken it for granted that sensations are due
to the action of stimuli upon a sense-organ. Light
falls on the eye, or a contraction of the muscle fibres
squeezes the muscle spindles ; the excitation thus started
is carried, by afferent sensory nerves, to the brain ; and
we get the sensation of colour or of fatigue. The course
of the nerve process which arouses sensation is always
from without inwards, from periphery to centre.
1 70 Kinaesthetic Senses
There is, however, one case — that of the sensation ot
effort or exertion — in which this view has been chal-
lenged. We have ascribed the sensation to the Golgi
spindles (§ 46), and have thus put it upon the same plane
with all other sensations. Some psychologists believe, on
the contrary, that it is an outgoing sensation, due to the
discharge of motor excitations from brain to muscle. Its
nerve process would then run from within outwards, from
centre to periphery.
The arguments are drawn, in the main, from pathology.
A patient who cannot move a leg, or who cannot turn his
right eye outwards, may nevertheless believe that he has
made these movements ; he will assure his physician that
he feels the weight of the moved limb, or the turn of the
eyeball in the orbit. Since no movement is made, these
sensations must, apparently, come from the centre, must
accompany the outgoing current of innervation.
We notice, however, in observing such patients, that the
effort to move the diseased leg always means a shift of the
hips, and various jerks and twitches in the sound leg ; and
that the effort to move the right eye always means actual
movement of the left. Here, then, are sources of kinaes-
thetic sensation which might easily give the illusion of
movement in the unmoved part. Besides, there are patho-
logical facts to be quoted on the other side. In certain
diseases, a patient may make quite extensive movements of
the limbs, without being aware of the fact ; indeed, he is
surprised, when his glance falls upon arm or leg, to find
that it has changed its position. Since these movements
are made, they must have been innervated ; since they are
made unconsciously, the innervation cannot have aroused
any sensation of effort.
§ 50- So7ne Touch-blends i/i
The following experiment tells very strongly against the exist-
ence of the innervation sensation. If two objects of the same
weight but of different size are hfted successively in the closed
hand, or even if they are lifted by a string attached to the finger,
the smaller appears the heavier. The observer may have seen
them weighed, and may be convinced that the weights are physi-
cally equal : nevertheless, the illusion persists. If, now, the judg-
ment of weight depended upon a sensation of innervation, this
result would be impossible : the observer, knowing that the same
amount of energy is required to raise both objects, would inner-
vate his muscles to the same degree.
We explained a similar illusion of the resting skin (§ 42) by
the difference in the slope of the pressure gradient. This factor
is here replaced by visual association. In the vast majority of
cases, the larger of two like objects is also the heavier. Hence
we have learned to interpret size as weight ; when we see a large
thing, we unconsciously innervate the muscles for a heavy thing.
The association holds, in spite of our knowledge that the weights
are equal : we lift the larger object as if it were heavy, the smaller
as if it were light. The former then flies up, giving us the kinaes-
thetic sensations that light things arouse, and we judge it to be
lighter than its companion.
§ 50. Some Touch-blends. — We are now able to analyse
the touch-blends mentioned in § 39. The difference
between hard and soft, for instance, is mainly a difference
in degree of resistance offered to the hand ; and this means
a difference in the degree of pressure exerted by the one
articular surface upon the other. The distinction thus
belongs to the joints rather than to the skin. Again, the
difference between smooth and rough is a difference, first,
between continuous and interrupted movement, and sec-
ondly between uniform and variable stimulation of the
pressure spots of the skin. The distinction thus belongs
to joints and skin together.
172 Kinaesthetic Senses
Sharp and blunt differ, primarily, as pain and pressure =.
a thing is sharp if it pricks or cuts, blunt if it sets up diffuse
pressure sensations. Here, however, as in all the touch-
blends, visual association plays a very large part.
Wetness is a complex of pressure and temperature. It
is possible, under experimental conditions, to evoke the
perception of wetness from perfectly dry things, — flour,
lycopodium powder, cotton wool, discs of metal ; and it is
possible, on the other hand, to wet the sl^in with water and
to evoke the perception of a dry pressure or a dry tempera-
ture. Not the moistening of the skin, but the fitting dis-
tribution of pressure and temperature sensations, gives rise
to the perception of wetness. Other modes of distribution
of the same sensations produce the perception of dryness.
Clamminess is a mixture of cold and soft : the cold sen-
sations and the pressure elements in the softness must be
so distributed as to give the perception of moisture. The
clammy feel of a wet cloth may be got by laying the finger
on a loosely stretched rubber membrane, and sending a
puff of cold air over it at the moment of contact. Oiliness
is probably due to a certain combination of smoothness and
resistance ; movement seems to be necessary to its percep-
tion. Clinging, sticky feels may be obtained from dry
cotton wool.
References for Further Reading
§§44-50. A. Goldscheider, Gesammelte Abhandlnngen, ii., i8g8;
V. Henri, Revue gentrale sur le sens miisculaire, in DAnnte psycholo-
giqite, S'"^ annee, 1899. 399; C. S. Sherrington, T/ie Muscular Sense,
in Schafers Text-book, ii., igoo, 1002 if. ; I. M. Bentley, T/ie Syui/ietic
Experiment, in American Journal of PsycJiology, xi., 1900, 414 ff . ; R.
S. Woodworth, Le Mouvement, 1903 ; W. Nagel, Die Lage-, Bewe-
gungs- und Widerstandsempfindungen, in Nagel's HandbucJu iii., 1905,
735 ff-
§ 51- KinaestJietic Organs of the Internal Ear 173
§51. The Kinaesthetic Organs of the Internal Ear. — We
have found, in the capsules of the joints, organs which re-
ceive their stimulation from movement of the limbs, and
which give us the perceptions of movement and position
of these members. We have now to consider certain struc-
tures of the internal ear, which represent kinaesthetic
organs of a different kind. They are stimulated mechan-
ically, by the acceleration of a mass-movement through
gravitation, inertia or centrifugal force, and they give us
the perceptions of movement and position of the head and,
perhaps, of the whole body. They are known as the cris-
tae ampullares of the semicircular canals, and the maculae
acusticae of the vestibule.
In § 28 we dealt with the cochlea of the internal ear, the part
of the membranous labyrinth which forms the end-organ of the
cochlear nerve and furnishes sensations of hearing. We are now
to discuss the function of the remaining portion, the vestibule and
the semicircular canals, which together form the end-organ of the
vestibular nerve. ^ There are five cell-groups, in each ear, to which
the fibres of this nerve are distributed : the maculae of the utri-
cle and saccule, the two divisions of the vestibule ; and the cristae
in the ampullar enlargements of the three semicircular canals.
Maculae and cristae are all of the same general type : there is a
local thickening of the membranous wall, upon which rests a little
field of hair-cells. In the maculae, however, the hairs support a
mass of tiny crystals of carbonate of lime, the otolith ; in the cristae,
they project freely, like a camel's-hair brush, into the ampullar
cavities. The otoliths are enclosed in a homogeneous, viscous
substance, which also interpenetrates and surrounds the ampullar
hairs. The mass which is moved in the maculae is, therefore, the
otolith ; in the cristae it is the cemented brush-like structure, which
has been termed the cupula. —
1 In addition to the models of the internal ear mentioned on p. 109, Exner's
Bogengangmodell (shown in Fig. 24, p. 177) and Otolithenmodell will be found
useful for demonstration.
1/4 KinaestJietic Senses
The study of the semicircular canals and the vestibule presents
a curious difficulty to psychology, a difficulty the reverse of that
which we have just met in our discussion of the sensitivity of mus-
cle, tendon and joint. There, we had a tangled complex of
sensations, and the problem was to distribute them among the
available end-organs. Here, we have highly developed end-organs,
but no very obvious group of sensations to refer to them. More-
over, there can be no doubt that the functions of the vestibular
nerve are, in large measure, reflex : by virtue of its cerebellar con-
nections it plays a large part in the regulation of what one may
call the tone of the muscular system ; the impulses normally pro-
ceeding from it keep the muscles trim and braced, while the
cutting off of these impulses has an atonic effect similar to that
produced by section of the dorsal roots of the myel. Under these
circumstances, it is not surprising that different investigators should
take very different views of the kinaesthetic importance of cristae
and maculae. The following sections, however, represent the gen-
eral trend of current psychological opinion.
§ 52. The Ampullar Sense. — If you turn round rapidly
upon the heels several times in succession, and then come to
rest with closed eyes, you have a sensation w^hich can only
be described as a swimming in the head. Its apparent
direction is opposed to the direction of the actual move-
ment, so that it wears the appearance of a negative after-
image. Having once noticed it, you are afterwards
able to notice, as you begin to turn, a swimming whose di-
rection is the same as that of the movement of rotation.
The sensation seems to circle through the head, and its
plane changes with change of the head's position. If, for
instance, you turn round with the head bent forwards on
the chest, and suddenly raise it to the normal attitude after
you have stood still, the plane of the swimming changes, as
suddenly, from horizontal to transverse vertical ; if you
§ 52. The Ampullar Sense 175
turn with the head inclined on the shoulder, and raise it
afterwards in the same way, the plane changes from
horizontal to sagittal.
This swimming sensation, which with practice may be
observed to follow a quick movement of the head in any
direction, comes from the cristae of the semicircular canals.
At high intensities, it passes into dizziness or vertigo.
It is significant that we find the canals fully formed, and con-
joined with a merely rudimentary cochlea, in animals, such as
birds and fishes, which have to balance in the surrounding medium.
Their size and accessibility, in these lower vertebrates, makes ex-
periment easy : the canals may be severed, plugged, or extirpated
without further injury to the organism. If, now, a single canal is
cut, say, in a pigeon, we note, as the result of the operation, a
general slackening of the whole muscular system, and also a dis-
turbance of movement in the plane of the severed canal. On the
one hand, the bird seems weakened : its flight is feeble, its legs
bend inwards ; on the other, it is subject to certain forced move-
ments. If, for instance, the right horizontal canal is cut, the pig-
eon keeps up a pendular motion of the head sidewise, to the right
and back again ; it also tends, in walking, to bend to the right and
so to circle round and round, instead of moving straight forward.
These symptoms vary with the extent and the standing of the
injury. Where the lesion is one-sided, there may presently be
complete recovery ; if both sets of canals are extirpated, the
muscular weakness may end in general muscular atrophy, and all
coordinated movements are thrown into confusion.
It is clear, then, that the canals constitute an organ which serves
to regulate the tone of the muscular system. But it seems clear,
also, that they stand in a special relation to movements of the
head. Injury done them not only cuts off the tonic impulses, but
in addition gives rise to abnormal impulses which arouse the
abnormal movements. This dynamic function might, like the
tonic, be reflex. Probably, however, it is attended by sensation,
the quality of which is lost to ordinary observation in the complex
1/6 Kinaesthetic Senses
of cutaneous and kinaesthetic sensations which we have described
in previous sections.
The evidence for sensation comes partly from experiments
made upon the normal human subject, and partly from pathology.
Experiments upon rotation, carried out under strict conditions,
reveal the swimming and dizziness of which we have spoken. Sim-
ilar sensations are evoked by syringing the ear, or passing an electric
current through it. Further, it is found that about half of the
deaf-mutes in our large institutions cannot be made dizzy by rota-
tion ; they do not stagger when thfe movement ceases, nor do they
show the compensatory twitching of the eyes which is normally a
symptom of dizziness. Now, autopsy proves that in about 50 per
cent, of deaf-mute ears there is lesion or degeneration, not of the
cochlea alone, but of the whole internal ear. This correspondence
furnishes a strong argument for referring the sensation of dizziness
to the canals.
§ 53. Theory of the Ampullar Sense. — The three semi-
circular canals of each ear are set, approximately, in the
three dimensions of space. They are also set symmetri-
cally in the two ears : the horizontal canals in the same
horizontal plane, and the posterior of the one side and the
anterior of the other side in parallel planes. It is thus clear
that any movement of the head, whatever its direction,
must affect the canals. If it is made in a plane which
coincides with the plane of a canal, then that canal alone
will be stimulated ; otherwise, two or more canals will be
involved, in different degrees, on the principle of the
parallelogram of forces.
Suppose, then, that we are subjected to a rotary motion in the
horizontal plane. When the turning begins, the water in the hori-
zontal canal lags behind the containing tube ; the back thrust of
the water bends the cupula ; and the nerves of the crista are
stimulated. We have the swimming sensation. As the turning
§53- Theory of the Ampullar Sense
■77
Fig. 24.
continues, the water takes up the motion of the canal, and the
cupula recovers its equilibrium. When we stop, the water in the
tube shoots forward, bending the cupula in the opposite direction ;
and we have the reversed swimming sensation, which continues
until the ampullar organ
comes to rest in its nor-
mal position.
Precisely the same
thing happens if we turn
round voluntarily on the
heels, and precisely the
same sort of stimulation
is set up, in the other
canals, by movements in
other planes. —
The quality of the am-
pullar sensation, at low
intensities, is most Hke
that of a diffused pres-
sure. The direction of
the swimming is not directly sensed, but depends upon association.
Dizziness usually occurs in a very complicated setting. When
we have turned upon the heels, and have come to a sudden stop,
the kinaesthetic sensations from the limbs are so disposed as to
give the perception of a certain position. On the other hand, the
swimming in the head, and the arrest of the soft viscera by the
body wall, give the perception of a movement in the opposite di-
rection. Further, if the eyes are opened, the objects about us
seem to be revolving in the same direction as that of our original
movement. Here, then, is a conflict, so to say, of three different
perceptions : the limbs are at rest, the body is moving one way,
and the outside world is moving another way. Oftentimes, to
make things still worse, nausea is added.
Under these conditions, introspection is very difficult. Some
psychologists deny the sensory character of dizziness altogether,
and regard it as the resultant of the conflicting perceptions. Since,
however, it may be set up by such local stimuli as the passage of
Exner's Model of a Semicircular
Canal.
178 Kinaesthetic Senses
an electric current through the ear, it appears to be referable to
the ampullar organs. Moreover, there can be no doubt that the
sensation in the head, as we turn it sharply to one side or start to
turn round, is from the first swimmy, faintly dizzy, so that dizzi-
ness would seem to be the quality natural to it at high intensities.
§ 54. The Vestibular Sense. — The sensory function of
the maculae is still somewhat problematical. It appears,
however, that they play a part in our perceptions of the
position of the body as a whole, and possibly of rectilinear
movements of the body in space, more especially v/hen
these perceptions refer to the vertical dimension. —
We have noticed that the people who ride on merry-go-
rounds at fairs lean inwards, as the speed of rotation in-
creases ; they shift their balance, to avoid flying off at a
tangent. This is natural enough. What is curious is that,
provided the eyes are closed, the riders think that they are
sitting uniformly upright. If they are asked to hold a
stick before them, vertically, as they revolve, they hold it
at a slant; their perception of the vertical has changed.
Again, we have noticed that, when the body is immersed
in water, as in diving or in swimming beneath the surface,
there is never any doubt as to which direction is up and
which down. No one with normal sense-organs has ever
been drowned by swimming to the bottom when he in
tended to come to the top of the water.
These perceptions are noteworthy when we compare
them with the behaviour of the deaf-mutes who lack the
sensation of dizziness. If such persons are placed upon a
merry-go-round, they do not adjust themselves to a new
vertical. They sit bolt upright, and hold the stick to the
true vertical ; they must be tied, or they are thrown off by
centrifugal force. And it is dangerous for them to bathe
§ 54- l^he Vestibular Sense 179
in deep water, even if they know how to swim, because,
once they are immersed, they lose the perceptions of up
and down, and may drown from sheer confusion of direc-
tions.
It seems, then, that we must have some source of per-
ception which the deaf-mutes are without ; and it is natural
to look for it in the vestibular organs. Many psychologists
believe that the maculae furnish sensations of pressure,
which, under favourable conditions, may be separately dis-
tinguished by introspection. —
Most of us have noticed, again, as we lay in a sleeping
car or were carried in an express lift to the top of a high
building, that there were parts of the journey during which
the perception of movement altogether disappeared. The
eyes must, of course, be closed ; there must be no draught
of air to suggest that we are moving ; and the motion itself
must be smooth and uninterrupted. Under these condi-
tions, a movement of the body forwards or backwards, up
or down, is not perceived, so long as its rate remains the
same. Let the rate change, however : let the car slow or
quicken its speed : and we are at once aware of our pas-
sage through space.
Some psychologists believe that whenever there is accel-
eration, positive or negative, of the rate at which the body
is travelling, the maculae are brought into action ; while,
so long as the rate is uniform, they adapt themselves to it,
as the ampullar organs adapt themselves to uniform move-
ment of rotation. If the movement is in the horizontal
plane, forward, backward or sidewise, the vestibular sensa-
tions are ordinarily swamped in the mass of sensations
from skin, muscle, tendon and joint. If, on the other hand,
it is in the vertical plane, — as in going up or down in a
i8o Kinaesthetic Senses
lift, tobogganing, dropping off a high place, swinging,— <
the sensations appear as a compression or lightness in
the head. Like the ampullar sensations, they are often
clearest in the form of negative after-images : when a
rising lift suddenly comes to a standstill, we have a distinct
feeling of squeeze in the region of the ears.
§ 55. Theory of the Vestibular Sense. — The maculae func-
tion in much the same way as the cristae. The otoliths
which are suspended above the fields of hair-cells corre-
spond to the water in the canals ; they lag behind, as the
supporting structure moves away, and they overshoot or
press down upon their support when the movement is
arrested. The two maculae of each ear are so situated
that the lines of displacement of the otoliths are at right
angles to each other; the one moves in a horizontal plane,
which slopes at an angle of some 45° from before back-
ward, and the other in a sagittal plane, which slopes at the
same angle from behind forward. They are thus affected,
on the principle of the parallelogram of forces, by move-
ments in any spatial dimension.
Applied to the changed perception of the vertical on the merry-
go-round, this theory means that the centrifugal force shifts the
otoliths outwards ; they glide into the position that they would
naturally assume if one were really leaning outwards with the
body at rest. The true vertical thus seems to slant out, and an
effort to restore it means a bend inwards. A like explanation
holds of the perception of direction under water • the pressure or
pull of the otoliths tells us whether we are head-up or head-down.
Destruction or atrophy of the organs would then lead to those
insufficiencies of perception which we note in the deaf-mutes.
Whether we may appeal to displacement of the otoliths for
the perception of acceleration of movement in the horizontal
§ 55- Theory of the Vestibular Sense i8i
plane depends upon the degree of inertia which they possess.
Since this is not known, any hypothesis would be merely guess-
work. There is, however, no introspective evidence of their
function, as there seems to be in the case of rectilinear vertical
movements of the body. —
Otolith organs have a very wide range in the animal kingdom,
a range that extends from the jelly-fish to man. Their functions
appear to be, from the first, tonic and static. It has been found
possible, for instance, to replace the otolith of a crustacean, which
sheds the contents of the otocyst at the same time that it sheds
the skin, by a mass of fine iron-filings. When the artificial otolith
is approached by an electromagnet, and the circuit closed, the
animal assumes a pecuhar position which is directly due to the
stimulation of the organ. On the other hand, the otolith sac is
the precursor of the organ of hearing, and this fact has been made
much of in theories of its function. It has been suggested, for
instance, that the maculae of our own ears give the sensations of
noise, and possibly of shrill, chirping tones, and that the cristae
give us the perception of the direction from which sounds come.
There is no evidence for either view. Again, it has been found
that the hairs which support the otolith are, at least in some forms,
selective : if tones are sounded in their neighbourhood, certain
hairs remain passive, while others — varying with variation of the
stimulus — are thrown into violent vibration. In the same way,
the hairs of the feathered antennae of the male mosquito vibrate
selectively to notes which correspond in pitch to the hum of the
female insect. It is tempting, in such cases, to regard the vibratile
organ as auditory, and to conclude that the stridulating, rasping
and tapping sounds of the invertebrates are heard by others of
their kind as they are by ourselves. It must, however, be remem-
bered that sympathetic vibration is a purely mechanical matter :
the excitation set up by the moving hairs might release a reflex,
or might be sensed as jar or quiver. Indeed, the close relation
of the otolith organ to the organ of touch makes it probable that
their sensations would be closely alike. Even the fish, in which
the membranous labyrinth has begun to divide into a vestibular
and a cochlear portion, do not appear to possess sensations of
i82 Kinaesthetic Senses
hearing, while they are extremely sensitive to jar of the water in
which they swim. On the whole, then, and with the reserve
which is due to the obscurity of the subject, we may say that true
hearing probably appears at a point fairly high up in the verte-
brate series.
References for Further Reading
§§ 51-55. J. G. McKendrick, The Internal Ear, in Schafer's Text-book.^
1900, 1 166 ff., 1 194 IF. ; W. Nagel, in Nagel's Hatidbnch, iii., 1905, 778 fF. ;
W. Wundt, Physiologische Psychologie, i., 1908, 440 flf. ; ii., 1902, 475 if.
J. Lubbock, On the Senses, Instincts and Intelligence of Animals, 1889,
chs. iv., v.; R. M. Yerkes, The Dancing Mouse, 1907, ch. v.; M. F.
Washburn, The Animal Mind, iqo8, ch. vi.
OTHER ORGANIC SENSATIONS
§ 56. The Sensitivity of the Abdominal Organs. — We may
group together, under the name of visceral sensations, all
the sensations, except those of sex, which are derived from
the internal organs of the body below the diaphragm. The
evidence for the nature and origin of these sensations, and
for the part that they play in the make-up of conscious-
ness, comes from various sources, surgical, physiological,
pathological, psychological. It is not all of the same tenor,
and no single line is at all complete.
Let us take, first, the testimony of the surgeon. Opera-
tions upon the abdominal organs are now fairly common,
and in many cases the anaesthetic employed affects only the
outer skin and the underlying connective tissue. Under
these circumstances, it has been found that stomach, intes-
tine, liver, gall bladder, kidney, — with the investing and
interstitial tissues, — as well as the rectal mucous mem-
brane, the anterior wall of the vagina, the uterus, the
ovaries, the Fallopian tubes with the adjacent portions of
the broad ligaments, and probably the part of the testes
that is covered by serous membrane, are one and all insen-
sitive. The organs may be pinched, stretched, cut, pricked,
burned, cooled, and the patient knows nothing about it.
On the other hand, the external or parietal peritoneum,
which lines the abdominal and pelvic walls, the muscular
and serous layers of the diaphragm, and the tunica vagina-
lis, are extremely sensitive : the first and third, apparently,
183
184 Other Orgafiic Sensations
to pain alone, the second to pressure and pain. From the
surgical point of view, then, the whole mass of visceral
sensations must be referred to these three tissues. The
sense of satiety, of a full stomach, would come from an up-
ward pressure against the diaphragm, colic pains would
be due to the pressure or pull of the distended intestine
upon the peritoneum, and so on.
On the whole, the results of direct physiological experi-
ment support this conclusion. Nevertheless, physiology
seems to take away with the one hand only to give with
the other. We learn, for instance, that there are enough
sensory mechanisms in the abdominal cavity to furnish any
number of sensations. We are reminded, also, of the dif-
ference between adequate and inadequate stimuli. The
inroads of a surgical operation are not natural or normal
to the organism ; and it is entirely possible, from the
physiological standpoint, that sensations may be aroused,
by natural processes, in organs which fail to respond to
external attack. In particular, we are confronted with the
law of reflex pain. Wherever two regions, of low and
high sensitivity respectively, stand in close nervous con-
nection, an injury done to the former is referred, as sen-
sation of pain, to the latter. Now viscera and skin are
thus connected. Hence a visceral disturbance might be
sensed, locally, as mere vague oppression, while the related
area of the skin was the seat of sharp, cutting pain. In
other words, the skin may steal from the viscera as taste
steals from smell.
If we turn to pathology, we find the facts as definite as
those offered by surgery, but of an opposite character.
There are cases of visceral anaesthesia, in which the
patients cannot tell whether they have eaten enough, but
§ 56. The Sensitivity of the Abdominal Organs 185
must measure out the amount of their food ; in which they
do not feel the need of evacuating the bladder and bowels,
etc. Now in these cases there is loss, not only of such
things as appetite, nausea, repugnance to food, the sense
of renewed vigour after sleep, but also of feeling and of
perception. Feeling may be lost entirely; the patients
are apathetic, incapable of most if not of all the emotions;
the agreeable and the disagreeable aspects of experience dis'
appear together. We return to these phenomena in § 74,
More to the present point is the loss of perception. The
patients have no knowledge of the flight of time ; in the
daytime they depend solely upon the clock, and on wak-
ing in the morning they are not aware that they have slept.
Plainly, then, if we may trust pathology, visceral sensa-
tions exist in some variety, and serve as the raw materia]
of certain complex perceptual processes.
All these differences may be reconciled, though as yet
only in a broad and general way, by an appeal to psychol-
ogy. The most obvious thing about visceral sensations is
their periodical recurrence. For the greater part of the
day we know nothing whatever, if we are in good health,
of the state of the abdominal organs ; introspection of
visceral sensation is impossible, because there is no sen-
sation to introspect. But for short times, at fairly definite
intervals, they loom large in consciousness ; either as
hunger and repletion, thirst and its satisfaction, or as the
characteristic feels that precede, accompany and follow
urination and defaecation. It is, evidently, this character
of recurrence that fits them for the part they play in per-
ception. It proves, further, that they are aroused only
under certain peculiar circumstances, on the occurrence of
certain changes in their organs. Since surgical operations
1 86 Other Organic Sensations
do not reproduce these circumstances or bring about these
changes, it is not surprising that the organs should show
themselves insensitive to knife and cautery. The negative
results are facts, but from the standpoint of psychology
they are irrelevant facts. The same thing holds of the
results of physiological experiment. The physiologist as-
serts that the stomach is insensitive to temperature; if we
drink hot or ice-cold water, we have at most a dull heaviness
in the stomach, while the warmth or cold is referred by
introspection to the body wall. But there may be a law of
reflex temperature sensation, as there is a law of reflex
pain. And in any case, we have no proof, in such results,
that the stomach is altogether insensitive, when stimulated
adequately, in the appropriate way.
In general, then, we may say that the external peritoneum
is probably responsible for colic pains ; that the diaphragm
furnishes both muscular sensation and pain ; and that
there are other sensations, peculiar to the alimentary canal,
which are aroused by special stimuli at recurring intervals
of time. We have now to examine these latter in more
detail.
We distinguish, in ordinary speech, many different sorts of pain :
we speak of head-ache, tooth-ache, stomach-ache, ear-ache ; of rheu-
matic, sciatic, gouty, neuralgic, anginal, labour pains ; and, more
generally, of dull, acute, fine, massive, throbbing, lancing, gnaw-
ing, cutting, aching, boring, shooting, stabbing, rending, chafing,
smarting, burning, scalding, racking pains. It is a disputed ques-
tion whether pain, as used in these phrases, is like colour a general
name for a number of sensible qualities, or like cold the name of a
single quality. On the whole, it seems necessary to distinguish
two ultimate pain sensations, a fine bright and a heavy dull pain
(§ 41) ; all other differences, however, appear to be reducible to
differences of intensity, of diffusion, and of duration or periodicity.
§57- Sensations of Digestive and Urinary Systems 187
Thus, a stabbing pain is a pain of limited area, definitely localised,
which suddenly attains a high degree of intensity ; a boring pain
oscillates between certain limits of intensity ; a racking pain swells
gradually to its maximum, and then sinks again ; and so on.
§ 57. The Sensations of the Digestive and Urinary Systems.
— Thirst is localised in the soft palate, and appears as a
diffuse pressure or as a blend of pressure and warmth, • — •
dryness and feverishness. It may be quenched, for a time,
by painting the soft palate with acid, or by rinsing the
mouth with water, or even by wetting the skin of face and
neck : that is to say, by stimuli which cool and moisten the
tissues, and start the salivary glands to action. It soon
recurs, however, as what Helmholtz called a general feel
of the lack of water in the body, though it is still referred
predominantly to the soft palate ; in this form, it may be
assuaged by the injection of fluid into a vein. We may,
perhaps, suppose that a deficiency of lymph in the lymph-
spaces of the mucosa of the soft palate brings about a
relaxation of the membrane, which serves to stimulate
Pacinian or kindred organs. Since the alimentary canal
is the normal channel by which the body is supplied with
water, it is natural that a regulative organ of especial sensi-
tiveness should be placed at its entrance.
Next in order, if we travel from above downwards, is the
sensation of hard pressure that results from the hasty
swallowing of too large a morsel or too large a gulp of
liquid. Unlike most of the alimentary sensations, this
pressure is localised towards the back. Its downward
course can be followed by introspection. It often has upon
it a suggestion of nausea, and undoubtedly comes from the
oesophagus ; but whether from the free nerve-endings of
the mucosa or from the layers of striped muscle, we do not
know.
1 88 Other Organic Sensations
Nausea itself is usually preceded and accompanied by
cold sweat and copious salivation. Besides the sensations
thus arising, it is sometimes complicated by a bitter taste
at the back of the mouth, by sensations of taste and smell
from contents returned by the stomach, and by dizziness.
Intrinsically, it appears as a sensation of pressure-like
quality, localised at the lower end of the oesophagus, and
probably due to muscular constriction. — The act of vomit-
ing introduces sensations from the muscles of the abdomi-
nal wall and the diaphragm, and from the pharynx, all of
familiar quality.
Hunger, like nausea, is a complex experience. It is
characterised by a dull ache, extending throughout the
lower jaw; by pressure in the pharynx; and by the sensa-
tions accompanying salivation. Its specific sensation is a
dull pressure in the stomach ; this rises, through a gnawing
soreness, to positive aching pain. The reference of hunger
to the stomach is as unhesitating as that of thirst to the
soft palate, and its localisation may be made definite by
palpation of the skin. The sensation may, perhaps, be
ascribed to tension of the stomach, caused by the engorge-
ment of the mucosa with the digestive granules developed
in the cells. — The sense of repletion, and the oppression of
a too hearty meal, are also referred to the stomach, and
may be definitely localised by palpation. We can only
guess that they are due to a tension of the walls of the
stomach, possibly complicated, in the case of overloading,
by pressure upon the abdominal wall and the diaphragm.
The intestinal tract from stomach to rectum is usually
free from sensation, with the exception of occasional colic
pain. Persons with weak digestion, however, report that
they generally find, after eating, stationary or travelling
§ 5^- Sensations of Circulatory and Respiratory Systems 189
pressure sensations in this region. The sensations are re-
ferred to the front of the body, and may be locaUsed by
palpation.
The sensations which appear before, during, and after
defaecation are those of pressure and dull pain. In urina-
tion, the sensation of warmth is added. The pressure in
both cases is somewhat sore, tinged with an ache ; it is
not unlike the sore muscular sensation (§ 45). The relief
that follows evacuation is partly a negative matter ; we are
freed from a mass of insistent sensation and can turn ouv
attention elsewhere. Oftentimes, however, we get a posi-
tive sense of lightness, akin to the bright diffused pressures
of health and excitement (§ 46) and perhaps referable to
the same organs.
It is tempting to regard the specific sensations of thirst, nausea,
hunger, etc., as novel qualities. Closely analysed, however, all the
experiences above described seem to reduce to two familiar con-
tinua : the light, thrilling sensations which pass into dull, hard
pressure, and the sore, achy sensations which pass into dull pain.
It would be overhasty to assert that the pressure quality in hunger
and nausea, for instance, is precisely the same ; but, at any rate,
analysis reveals a likeness which is surprising in view of the gross
difference between the hungry and the nauseated consciousness.
This perceptual difference will occupy us later (§ 104), as will
also the question of internal localisation (§ %2>).
§ 58. The Sensations of the Circulatory and Respiratory
Systems. — For the most part, the action of heart and
lungs is not accompanied by sensation. There are times,
however, — after severe exertion, or during transient dis-
turbance of function, — when the separate heart-beats are
clearly sensed as a dull throbbing pressure : it is not easy
to say whether the sensations are locaUsed in the body
190 Other Organic Sensations
wall or in the heart itself. Further, when we are anxious
or worried or apprehensive, we get a characteristic sense
of oppression from the cardiac region. This may appear
alone, or in connection with nausea or choking sensations
of muscular pressure from the pharynx. The two latter
experiences are so well-marked that they have received
names in everyday speech; in the first case, we say thit
we have a sinking of the stomach, in the latter that the
heart has come up to the mouth.
Again, it is supposed that circulatory sensations, due to
the contraction of the walls of the blood-vessels, play a
part in the experiences of shudder, shiver, and goose-flesh.
Analysis is here very difificult. In shuddering, however,
there is certainly a muscular element; in shivering, this is
complicated by sensations of cold ; and in goose-flesh we
have, perhaps, besides pressure from the hair-bulbs, sensa-
tions from the contraction of the unstriped muscles. The
tingling sensations that occur when circulation is suddenly
restored to a benumbed limb — pins and needles, as they
are called — are also, in all probability, to be ascribed to
nerve-endings in the walls of the vessels.
A sense of oppression, not unlike that which comes
from the cardiac region and often associated to it, appears
in the chest in connection with disturbances of breathing.
It may be induced by a cramped position of the body, as
when one sits for a long time bent over a desk ; or by bad
air, as in a lecture or concert room ; or by an unusual
effort of respiration, as in the first stages of running, be-
fore the respiratory mechanism has become adapted and
the runner, as we say, has got his second wind. At low
intensities we speak of it as stuffiness; at the highest, as
suffocation ; when it is fused with cardiac oppression, as dis-
§ 59- ^^^'^ Sensations of the Genital System 191
tress. It is probably to be referred to nerve-endings in the
alveoli of the lungs, and is prominent in asthma and other
dyspnoeic conditions. The bracing sense of fresh air, on
the other hand, is due to sensations from the respiratory
muscles.
§ 59. The Sensations of the Genital System. — Repro-
duction is one of the supreme vital functions; and the
study of the reproductive organs, their development and
mechanism, belongs accordingly to all divisions of the
science of life, — to biology in the narrower sense, to com-
parative anatomy, to embryology and histology, and to
physiology. These sciences have, as a matter of fact,
devoted much attention to the various phases of the
problem ; they have ascertained facts, established laws,
and worked out homologies and correlations. Especial
interest has been taken, of recent years, in the questions
of sexual pathology, not only in their medical, but also in
their moral, social and legal aspects. It is the more sur-
prising, then, that very little is known, psychologically, of
sexual sensation.
There seems to be no doubt that all the reproductive functions
may run their course reflexly, without any sort of conscious con-
comitant. Normally, however, the train of reflexes is under cere-
bral control. Sexual stimulation implies, besides sensations from
the sex-organs themselves, a wide-spread arousal of other organic
sensations, and a play of perceptions and ideas, visual, tactual and
kinaesthetic. The special sensations of the genital system appear
to occur in three stages : first as an irritation or excitement, which
accompanies the tumescence of certain erectile tissues ; then as
sexual gratification, which culminates in the orgasm accompany-
ing ejaculation or the consummation of the sexual act ; and thirdly
as relief, the sexual analepsis which follows coition.
192 Other Organic Sensations
Sexual excitement, so far as it is a matter of specific sensation,
is usually described as a need of evacuation. Thus, Bain writes
that " the appetite that brings the sexes together is founded on
peculiar secretions which periodically accumulate within the sys-
tem, producing a feeling of oppression until they are either dis-
charged or absorbed." ^ This view, however, is negatived by many
lines of evidence. Sexual appetite and its satisfaction may persist
after excision of the testes in the male and the ovaries, Fallopian
tubes and uterus in the female ; in children there frequently exists
a well-defined sexual excitement long before there is any true
sexual secretion ; in adults the sensations may continue to appear
long after the sexual glands have discontinued their functions ;
and, finally, there may be an intensive sexual life in the congenital
absence of any sexual glands at all. Moreover, sexual irritability is
locahsed, in the male on the surface of the glans penis, and in the
female in the clitoris and the adjacent erectile parts. These
organs are sexually sensitive even in the flaccid state, though the
degree of sensitivity differs greatly in different individuals and even
for the same individual at different times. Both in quality and in
its irradiating character the sensation of sexual excitement resem-
bles tickhng. We do not know how it is aroused : there are no
lust spots, akin to the sensitive spots of the skin, and the organs
sometimes described as genital corpuscles are certainly not sexual
in function.
Most authorities appear to regard the orgastic sensations, in
both sexes, as distinct and unique. It is, however, as difficult in
their case as it is in those of hunger and nausea to say whether we
are in presence of a novel quality or simply of a specific resultant
of muscular and glandular activity. Since the sensations may ap-
pear after extirpation of testes and ovaries, the latter view would
seem to be the more probable.
Sexual analepsis is made up, for the most part, of muscular sen-
sations. It is a general sense, either of lightness and relief, or of
lassitude and faintness, very like that which follows urination and
defaecation : indeed, we may suppose that this resemblance is
^ A. Bain, The Senses and the Intellect, i S68, 244.
References for Fiirther Reading 193
mainly responsible for the evacuation theory of sexual sensation
at large.
The sensations attending menstruation and parturition are those
of muscular pressure, pain and strain, and sometimes of nausea ;
neither among them nor in the following analeptic states are new
qualities found.
References for Further Reading
§§ 56-59. C. S. Sherrington, Common Sensation, in Schafer''s Text-
hook, ii., 1900, 965 ff. ; H. Ellis, Studies in the Psychology of Sex, iv.,
1903, I ff. (Analysis of the Sexual Impulse) ; E. Meumann, Zur Parage
der Sensibilitat der inneren Organe, in Archiv fur die gesai/n/ite Psy-
chologie, ix., 1907, 26 ff.
§ 56. Recent discussion makes it clear that the effect of a local an-
aesthesia is more extended than the surgeons at first supposed, so that
certain of the arguments upon which the conclusions of this section are
based must be regarded as invalid. The evidence is at present conflict-
ing, and the discrepancies cannot be referred certainly either to indi-
vidual differences of sensitivity or to differences in the technique of
operations. The reader may consult E. Becher, Ueber die Sensibilit'dt
der inneren Organe, in Zeits. f. Psych., xlix., 1908, 341 ff. ; Eiiiige Be-
merktmgen i'lber die SensibilitUt der inneren Organe, in Arch. f. d. ges.
Psych., XV., 1909, 356 ff. ; E. Meumann, Weiteres zur Frage d. Sensi-
bilitat d. intieren Organe u. d. Bedeutung d. Organempfindungen, ibid.^
xiv., 1909, 279 ff.
SYNAESTHESIA
§ 60. Synaesthesia. — Every sensory stimulus of moderate
intensity arouses a wide-spread reaction. It has been
shown, for instance, that the sounding of a single note
upon the harmonium will not only bring about an adjust-
ment of the organs of hearing, but will also call out visual,
verbal and other associations, often of considerable vivid-
ness and detail, as well as organic sets and attitudes of
various kinds. Such a result is, perhaps, only natural, in
view of the manifold connections within the nervous sys-
tem, — though it comes as something of a surprise to
those who are accustomed to look only at the local effects
of stimulation.
Quite apart, however, from this general disturbance of
the organism, it not infrequently happens that a stimulus
sets up, besides its appropriate sensation, a secondary or
concomitant sensation. The phenomena of synaesthesia,
as it is called, are scattered over the whole range of sen-
sation, and are extremely varied in nature. Sometimes
they seem to depend upon a purely individual feature of
nervous constitution, as when a sour taste makes the scalp
itch ; sometimes they are common to a large number of
persons : most of us shudder and grit the teeth when we
hear the squeak of chalk against the blackboard, or the
grating sound of a saw upon metal. The connection may
obtain between separate sense-departments, as sound and
sight, or between different areas of a single sense-depart-
ment; thus, an itching of the nose often comes along with
194
§ 6o. SynaestJiesia 195
pricking sensations at the back of the neck on the same side,
and the emptying of bladder or rectum is accompanied by
a muscular shiver. In some cases, the concomitance is
stable, in others it is highly variable ; in some it is limited,
as it were incidental, in others systematic, extending to an
entire series of qualities.
The commonest form of systematic synaesthesia, known
as coloured hearing, occurs almost as frequently as par-
tial colour-blindness. In it, any auditory stimulus, noise,
tone or sound complex, may arouse a photism or chroma-
tism, a visual image of light or colour. No general rules
can be laid down, since the associations vary for different
persons and, within limits, may vary for the same person
at different times. Two types, however, have been dis-
tinguished. In the one, the connection is direct; the sound
calls up the sight without any intermediary ; in the other it
is indirect, by way of organic sensations.
The following case may be quoted in illustration. "The
vowels of the English language always appear to me, when I think
of them, as possessing certain colours. Consonants, when thought
of by themselves, are of a purplish black ; but when I think of a
whole word, the colour of the consonants tends towards the colour
of the vowels. For example, in the word ' Tuesday,' when I
think of each letter separately, the consonants are purplish-black,
u'vs, z. light dove colour, ^' is a pale emerald green, and a is yellow ;
but when I think of the whole word together, the first part is a
light grey-green, and the latter part yellow. Each word is a dis-
tinct whole. I have always associated the same colours with the
same letters, and no effort will change the colour of one letter,
transferring it to another."^
In rare cases, colours accompany the sensations of taste and
1 From a letter cited by F. Galton, Inqui7'ies into Human Faculty and its
Development, 1883, 149.
196 Synaesthesia
smell. Salt, for instance, is given by one observer as dull red,
bitter as brown, sour as green or greenish blue, and sweet as a
clear, bright blue. Colour concomitants of pain, pressure and
temperature have also been recorded : thus, the plunging of the
hands into cold water may be seen as bright red.
The synaesthetically aroused colours do not follow the lines of
what we should suppose to be the least associative resistance. It
is odd to read that " the word ' red ' assumes a light-green tint,
while the word ' yellow ' is light-green at the beginning and red at
the end." And while the observer just mentioned sees the taste
of meat as red and brown, and that of bananas as yellow, he tastes
Graham bread as a rich red, and all ice creams — except choco-
late and coffee, which are brown because they have a bitter com-
ponent — as blue.
Tonal vision, the systematic opposite of coloured hearing, seems
not to occur. Incidental colour-phonisms have, however, been
noted : in one case all the blues, bright as well as dark, are heard
as deep and dull, and all the yellows as more or less high and
ringing tones. Phonisms of pain, pressure and temperature are
also known to exist. Recently, a case of gustatory (or rather
gustatory-tactual) audition has been discovered ; the sound of
* intelligence,' for example, tastes like raw sliced tomato, and the
sound of ' interest ' like stewed tomato !
It is clear that we cannot explain coloured hearing as
we explain the shudder set up by a shrill or grating noise.
The colours are presented to the mind's eye; they are,
as we have said, images, not peripherally excited sensations.
Nevertheless, several lines of evidence go to show that
they belong to the domain of sensation rather than to that
'of the association of ideas. First, the concomitance of
colour-image and sound is, in many cases, far too detailed
and too persistent to be referred to association, in the ordi-
nary sense of that word. It is impossible that the con-
nections should have been established during childhood ; it
§ 6i. The Image 197
is impossible, had they been thus established, that they
should continue unchanged. Further, attempts have been
made, by trained and interested observers, to trace back their
synaesthetic experiences to associations formed in child-
hood ; but in spite of all efforts they have ended in failure.
Again, we should expect that an association due to expe-
rience would show, along with a certain measure of varia-
tion, an underlying agreement or correspondence ; whereas,
as Galton remarks, " no two people agree, or hardly ever do
so, as to the colour they associate with the same sound."
And lastly, coloured hearing is an hereditary trait ; it tends
strongly to run in families. While, then, it is possible,
and even probable, that synaesthesia of the incidental type
may be the legacy of some vivid or thrilling experience in
early life, we are forced to the conclusion that, in general,
it represents a congenital endowment. As to its physical
basis, we can merely guess. It may depend upon some abnor-
mal disposition of the paths of connection within the brain.
Or possibly it may depend, as a recent writer has sug-
gested, upon an unusual elasticity of the walls of the cer-
ebral arteries. On this view, a rush of blood to the audi-
tory centre might, owing to the extensibility of the arteries,
be propagated to the visual centre ; the hearing would be
coloured. The theory accounts for the loss or reduction of
synaesthesia as we pass from childhood to mature life, and
for its occurrence in moments of emotional stress. As the
arterial structure might be a matter either of inheritance or
of individual peculiarity, it allows further for both the con-
genital and the acquired types of synaesthesia.
§ 61. The Image. — The facts of synaesthesia lead up
to the question of the nature of the image, and of its dif-
198 Synaesthesia
ferences from sensation. It is usually said that the image
differs from the corresponding sensation in three respects :
its qualities are relatively pale, faded, washed out, misty ;
and its intensity and duration are markedly less.
Since these differences are all differences of degree, and
not of kind, it should be possible to find experimental con-
ditions under which the sensation and the image are
confused. Experiments have, in fact, been made, and
with positive result, in the fields of sight, sound and
touch.
If, for instance, the observer is seated in a well-lighted room
facing a sheet of ground glass, behind which is a screened projec-
tion lantern, it is often impossible for him to decide whether the
faint colours that he sees on the glass are due to the lantern or to
his own imagination. You say to him : Imagine that there is a
picture of a banana on the glass ! — and in many cases it makes
no difference at all whether you show a strip of very faint yellow
light from the lantern or whether you shut off the objective light
altogether. The strip of seen yellow is confused with a yellow
image. The experimenter, who regulates the course of the obser-
vations by signalling to a third person when the lantern is to be
turned on, is sometimes greatly surprised at the gross errors made
by the observer. What seems to him obviously sensory may be
reported, without hesitation, as imaginative.
Again, we are frequently in doubt, in everyday life, whether we
hear a particular sound or merely imagine it. And if, in the
laboratory, the observer is required to listen intently to a contin-
uous faint noise, such as is produced by the falling of a stream of
fine sand (§ 81), the same confusion will be noted. The experi-
menter may reduce the stream to a mere trickle, and may finally
stop it ; the observer will still, in many cases, beheve that he
hears the hiss.
Lastly, a similar confusion is found in experiments upon pres-
sure and tickling. If, for example, in the course of a series of
stimulations of a pressure spot, the experimenter says Now ! but
§ 6i. The Image 199
omits to touch the skin, the observer may, nevertheless, report
the arousal of a pressure sensation.
It has been found, further, that a visually minded ob-
server, who knows nothing of the laws of the negative
after-image, may describe — and describe in correct terms
■ — the after-images of merely imagined colours. It is also
a matter of common knowledge that, in certain patho-
logical states, the image may become what is called an
hallucination, that is, may take on all the characters of clear
and intensive sensation.
How is it, then, that we so rarely confuse image with
sensation in our everyday experience? Well, the confusion
may not be so uncommon as we suppose. However, if it
is, the distinction may be accounted for, at any rate in large
measure, by the differences of conscious context or setting
in which the two processes appear. Images, for in-
stance, seem to be less sharply localised than sensations ;
they change and shift more rapidly, and in a meaningless
way ; they move with movement of the eyes. But the
writer is not sure that the image does not, as a rule, evince
a sort of textural difference from sensation ; that it is not
more filmy, more transparent, more vaporous. If this is
the case, then it is better to consider sensation and image
as sub-classes of a particular type of mental element than
to include them outright in a single class (§ 10).
Individual minds differ widely in the nature and frequency of
their characteristic image-processes. Visual and auditory images
are of common occurrence, although the auditory image appears,
in general, to be connected with actual innervation of the larynx,
that is, with kinaesthesis. Kinaesthetic images are extremely
difficult to distinguish from kinaesthetic sensations. The differ-
ence, in the writer's experience, is largely a matter of complexity ;
200 Synaesthesia
the mental nod which gives assent to an argument is more sche-
matic, involves fewer muscles and involves them less solidly,
than an actual nod. Images of taste and smell have often been
reported, but only exceptionally play any considerable part in
consciousness. Organic images are rare.
References for Further Reading
§§ 60, 61. E. Bleuler and K. Lehmann, Zwangsinassige Lichtemp-
findtingen durch Schall mid verwandte Erscheimingen auf dem Gebiete
der anderen Shniesempjindungen, 1881 ; F. Galton, Inquiries into Hu-
man Faculty and its Develop jftetit, 1883; G. M. Whipple, Two Cases
of Synaesthesia, in American Journal of Psychology, xi., 1900, 377 ; J. E.
Downey, An Experiment on getting an After-image from a Mental
Ijftage, in Psychological Review, viii., 1901, 42; O. Kiilpe, Ueber die
Objectivirimg und Subjectivirung von Sinneseindrucken, in Wundt's
Philosophische Studien, xix., 1902, 508 ; R. Wallaschek, Psychologic und
Pathologic der Vorstellung, 1905, 149; A. H. Pierce, A Hitherto Unde-
scribed Variety of Synaesthesia, in American Journal of Psychology,
xviii., 1907, 341 ; C. W. Perky, An Experimental ^tudy of Imagination,
ibid., xxi., 1910, 422 if.
THE INTENSITY OF SENSATION
§62. The Intensity of Sensation. — All sensations have
the attribute of intensity. A light may be bright or dull, a
tone loud or faint, a pressure heavy or light, a taste strong
or weak. If we take any given sensation as a starting
point, we can travel from it in a straight line either towards
zero, the point of its disappearance, or towards a maxi-
mum, the point of its greatest possible strength (§ 12).
The intensities that lie in order along this line are, in
their way, as individual as are the qualities that lie, for in-
stance, along any straight line of the colour pyramid. A
loud tone is not a sum of two or three weak tones, but
something entirely different from a weak tone. It may be
reduced to a weak tone, if we move from high to low upon
the intensive scale, just as a red may be reduced to pink if
we move from red towards white ; but it no more contains
a number of weak tones than pink contains white. In
other words, intensity of sensation must not be confused
with intensity of stimulus. If we want to use a weight of
5 eg. in a balance, it makes no difference whether we take
a single weight of 5 eg., or two of 2 and one of i eg., or
five of I eg. If we want a light of 16 c. p. at a corner of
a room, it makes no difference whether we take a single
16 c. p. bulb, or two of 8, or four of 4 c. p. Stimuli can be
added, subtracted, multiplied; the greater, stronger stimulus
contains or sums up a certain number of lesser, weaker
stimuli of the same kind. It is otherwise with sensation.
202 The Intensity of Sensation
You cannot get the heavy by adding together, mentally, a
number of light, or the bright by adding together a num-
ber of dull: you cannot say that the heavy differs from
the light by a certain fraction of the heavy or multiple of
the light, or the bright from the dull by a certain fraction
of the bright or multiple of the dull. Every intensity of
sensation is itself, individual and characteristic: the inten-
sive sensations represent, as we have said, points or posi-
tions upon an intensive scale which runs from a lower
limiting value to a maximum, just precisely as a particular
■pink or olive represents a point within or upon the colour
pyramid.
We live so habitually in a world of objects, and we think so habitu-
ally in terms of common sense, that it is difficult for us to take up
the psychological standpoint towards intensity of sensation, and to
look at consciousness as it is, apart from any objective reference.
This book, we say, is heavier than that ; this lamp gives the better
illumination of the two ; this piano has a louder tone than the others.
Strictly interpreted, such statements may mean either one of two
things. They may be taken physically, to mean that the books
weigh differently in the balance, the lamps measure differently in
c. p., the piano strings set up air-waves of different amplitude ;
or they may be taken psychologically, to mean that the books feel
heavy and hght, the lamps look bright and dull, the piano tones
sound louder and less loud. As a rule, however, we are talking
neither physics nor psychology, but a confused mixture of the two.
It is true, of course, that we gauge the weight by lifting, the illumi-
nation by eye, and the strength of tone by ear. But, in doing
this, we transfer to sensation the properties that really belong to
stimulus : we think of the ' feel ' of the heavier book as the ' feel '
of the lighter with some more ' feel ' added to it ; we take the look
of the bright lamp to be the same thing as the look of the dull,
only with an addition ; we regard the sound of the loud instrument
as identical with the sound of the weaker, only that there is more
§ 62. The Intensity of Sensation 203
of it. In other words, we make the intensive sensation a copy of
the intensive stimulus, and we assume that the strong sensation is
built up by adding to the weak, and the weak produced by sub-
tracting from the strong.
This fallacy of common sense is easily exposed by experiment.
Take two glasses of sugared water, the one moderately sweet, the
other very sweet, syrupy. Taste them in turn. Introspection de-
clares at once that the tastes lie in the same straight line ; the
sweets are intensive variations of the same quality. But there is
no hint — if you think only of the tastes themselves, and forget
about the sugar — that the strong sweet contains the weak, is the
sum of a number of weak. And it is impossible to imagine a
third sweet which, if added to the weak, shall give the strong :
the adding of sensation to sensation is meaningless, a task that
you cannot lay hold of. The strong sweet Ues fairly high up,
the moderate sweet somewhat lower down, on the scale of sweet
intensities. That is all.
Let us carry the experiment a little farther. Take, besides the
two cups of sugared water, which we will call a and b, a number
of others ; make them all different, but let them all be sweeter
than the moderately sweet a and less sweet than the syrupy b. Set
the cups out upon a table, a and b to your left and right respec-
tively, and the rest grouped at haphazard in the middle. Now try
to pick out, by taste, a sweet c which lies for sensation midway be-
tween a and b : taste first a, then a cup from the middle group,
and then b ; and keep on tasting until you are satisfied. If you
take your time, and rinse the mouth between observations, so that
the tongue is not cloyed, the task is rather surprisingly easy, —
and the result is illuminating. For it means that we can measure
off distances along the straight line which includes all the intensities
of sweet ; we can say by taste that the distance ae is equal to the
distance eb, precisely as we can judge by eye that two spaces be-
tween the pictures on the wall are equal. Nothing could show
more clearly that the intensive sensation is simply a point or posi-
tion upon an intensive scale ; and no experience could refute
more decisively the common-sense notion that it is a copy of the
intensive stimulus.
204 '^J^^ Intensity of Sensation
Within wide limits, the intensity of sensation may be
treated as an independent variable : that is to say, we may
discuss it without regard to quality, and may assume that
it varies while quality remains unchanged. Nevertheless,
it is important that the limits be recognised. We find,
on the one hand, qualities that are intrinsically weak or
strong ; and we find, on the other hand, intensities that are
bound up with definite qualities. In these cases, the two
attributes must be considered together.
We noted in § 24 that high tones are intrinsically loud and lovf
tones intrinsically weak. The lowest tones remain faint, even
when the energy of stimulus is, relatively, very considerable ; and
high tones give the impression of loudness, even when their stimuli
are little more than liminal. So, in the sense of taste, bitter is an
intrinsically strong sensation, as compared with sour, sweet and
salt. Conversely, there are many scents (violet, tea, vanilla) that
are intrinsically weak : they are easy to detect, they are insistent
(§ 12), but they are never strong as asafoetida or musk is
strong.
Again, we have seen that intensive variation of punctiform
pressure stimulus gives the qualitative series contact, pressure,
granular pressure (§ 39), and of punctiform pain stimulus the
series itch, prick, pain (§ 41); while the dragging sensation from
the muscles and the sensation of tendinous strain both alike pas.=
over, at high intensities, into dull pain (§§ 45, 46). The most
striking instance of the connection of particular intensities with
iefinite qualities is, however, afforded by visual sensation. A
change in the intensity of visual stimulus not only renders the
sensation brighter or duller (intensity), but also makes it lighter
or darker (quality), and in the case of colour may change all
three of the constituent attributes, hue, tint and chroma (§ 16).
Some psychologists have argued from this that visual sensa
tions do not possess the attribute of intensity at all ; that bright
ness and lightness, dullness and darkness are simply different
§ 62. The Intensity of Sensation 205
names for the same qualitative characters.^ Such a conclusion
is, however, neither probable in itself nor supported by visual
theory.
We saw in § 22 that the retinal processes which arouse the sen-
sations of ^-^ and Ware antagonistic and incompatible. If, then, a
Bk and a JVfaW at the same time upon the same area of the retina,
any one of three things may happen : the resulting processes may
be equal in intensity as well as opposite in direction, and the
retina may be undistiirbed ; or the B/i may be the stronger stimu-
lus, and may set up a Bk-process of the intensity of Bk — IV; or
the JVma.y be the stronger stimulus, and may set up a ?F-process
of the intensity IV— Bk. In other words, a purely retinal vision
would give us various intensities of Bk and JV, but no sensations
of grey. These relations are, however, complicated by the exist-
ence of the sensation of neutral grey, a cortical sensation of con-
stant quality ; and it is the addition of neutral grey to the retinal
intensities of Bk and W that makes every change in the black-
white series, as we actually have it, a change of quality as well as
of intensity. A retinal Bk, of whatever intensity, must darken
the cortical grey ; a retinal PV must lighten it : and darkening
and lightening are shifts of quality. To secure intensive varia-
tion, with constancy of quality, we should have to increase the
energy of the Bk and JV components of the cortical grey, both
together, in equal measure; but this is the very thing that the
constitution of the retina forbids.^ — In fine, then, intensity is an
1 F. Hillebrand, Ueher die specifische Helligkeit der Farben, in Sitzzings-
berichte der kais. Akademie der Wissenchaften in Wien, Alatheni.-naturw.
Classe, xcviii., Abth. iii., February, 1889, 88 f.; O. Kuelpe, Outlines of Psy-
chology, 1909, 114.
^ This explanation is due to G. E. Mueller : see Zur Psychophysik der Ge-
sichtsenipfindungen, in Zeitschrift f. Psychologie u. Physiologie d. Sinnesorgane,
X., 1896, 31 ff.; xiv., 1897, 60 ff. —
We have to solve this problem of intensity for our own visual system; and
our visual system is based upon the principle of antagonism. But it is quite
possible that other eyes are built upon a different plan. It is possible, for
instance, to think of a primitive eye, whose sensations should one and all be
sensations of light (as opposed to sensations of dark) and shouM show a
2o6 The Intensity of Sensation
attribute of visual as it is of all other sensations ; only, the dual na-
ture, peripheral and central, of the visual apparatus brings it about
that intensive change of a sensation of light necessarily involves
transition to another quality. When this fact is taken into account
along with the facts of § i6, the qualitative changes due to change
of intensity in the sphere of colour (hue, tint and chroma) follow
of themselves. —
So far, we have been considering cases in which the attributes
of quality and intensity are interdependent. There are, further,
many instances in which we cannot vary intensity without change
of quality, merely because we cannot control the stimuli. For
instance, it is impossible, except in the higher regions of the tonal
scale, to produce a sensibly simple tone that is at all loud. If we
take a flue pipe or a bottle, Vv'e find that increase of air-pressure
sends the tone up ; if we take a tuning-fork, we find that a violent
blow introduces complicating noises and overtones. Again, noth-
ing might seem easier than to secure a graded series of intensities
of noise ; all that we have to do is to let a ball drop from different
heights upon a wooden plate. Experiment shows, however, that
change in the height of fall is very likely to bring with it a change
in the pitch, as well as in the loudness of the noise ; it is, as a
matter of fact, difficult to maintain a constant quality of noise even
within the comparatively short range of intensities required for
laboratory work. Once more, the quality of what we have called
resultant odours (§ 32) seldom remains stable over any wide ex-
tent of the intensive scale. It seems that the component stimuli
behave differently, gain or lose in power to make themselves
sensed, at different intensities ; though in a field where so little is
known it is hazardous to risk an explanation.
regular intensive gradation. The world in which an organism possessed of
such an eye would live might then be very light, light, moderately light,
hardly light, or not light : the sensations of light would range between a
maximal and a zero intensity, precisely as our own sensations of noise range
between maximal loudness and silence, — that is, no noise at all. The organ-
ism would not distinguish, as we do, between light and dark, but would simply
experience varying degrees of light. In the absence of an adequate light
Stimulus it would not, as we do, see dark, but would see nothing. Cf. § 15.
-§63. Mental Measurement 207
§ 63. Mental Measurement. — The psychological problem
of the intensity of sensation is bound up, historically, with
a much wider question, the question of the possibility of
mental measurement. Every science tries to state its facts
and to formulate its laws as precisely as possible, that is, in
quantitative terms, in measured amounts. Thus, it is not
enough to say that gravitation is a force which the earth
exerts upon every particle of matter ; it is not even enough
to say that the force is proportional to the mass of the
material body, but independent of the particular kind of
matter of which it is composed : the physicist goes further,
and measures the force of gravitation in terms of accelera-
tion. Physics and chemistry are, indeed, from end to end,
quantitative or measuring sciences. But biology, too, tries
to measure : the modern biologist measures the range of
variation shown by the members of a species, gives numer-
ical expression to the factors that determine heredity, and
so on. And psychology has to face the same issue. There
are facts of mind and there are laws of mind : can, then,
these facts and laws be quantified .'' can we measure mind }
Now the question of the possibility of mental measurement
has been chiefly discussed, as was said above, with reference
to the intensity of sensation. Here, therefore, is the fitting
place to take it up. We shall ask what measurement means ;
we shall ask in what sense, and to what extent, measurement
may be applied in psychology ; and we shall draw our
illustrations from the study of sense-intensity, as defined in
the preceding § 62. —
Whenever we measure, in any department of science, we
compare a given magnitude with some conventional unit of
the same kind, and determine how many times the unit is
contained in the magnitude. If we say, for instance, that
2o8 The Intetisity of Sensation
a certain line is 5 cm. long, we mean that we have compared
the line with the conventional unit of length, i cm., and
have found that it contains this unit five times over. All
measurement thus implies three given terms : the two limit-
ing points of the magnitude to be measured (beginning and
end, top and bottom, extreme right and extreme left, zero
and maximum), and a third point lying at unit-distance from
the one or the other limiting point.
The intensities of sensation lie, as we have said, along a
straight line which extends from a zero-point to a point
of maximal strength. Here is a magnitude with limiting
points. In order to measure sense-intensity, — the intensity
of sensations of light or tone or noise, of pressure or taste or
smell, — we have, first, to establish these two points, defi-
nitely and accurately, and secondly to determine the unit of
intensive measurement, the standard subdivision of the total
line.
It is important to realise that the unit of measurement is always
a conventional unit ; its choice is simply a matter of practical con-
venience. Scientific men are now generally agreed that the unit
of physical space shall be the cm., the unit of time the sec, and
the unit of mass the gr. There is, however, nothing absolute about
these units. The metric system makes calculation easy, relates the
three fundamental quantities in a very simple manner ; but that
is its sole, as it is its sufficient, claim to acceptance.
And just as the unit of measurement is conventional, and the
pace or the span, the ounce or the pound, will give us perfectly
valid measures of space and mass, so also may our selection of the
magnitude to be measured be arbitrary or conventional. The
ordinary postal balance weighs up to 16 oz. ; the ordinary kitchen
scales weigh up to 4 lb. We can measure — we can express by
the number of contained units from zero to maximum — any mag-
nitude that chance throws in our way.
But this means that our experiments with the cups of sugared
§ 63. Mental Measurement 209
water (§62) was a quantitative experiment, a measurement of mind.
We had, as our arbitrarily chosen magnitude, the sense-distance
from the moderately sweet a to the syrupy b. Then we bisected
that distance, by finding the sweet c that lay midway for sensation
between a and b. The half-distance was our arbitrary unit ; and
we can write, in terms of it, ab ^ 2 ac ^= 2 cb, just as with a unit
of I ft. we can say that the regular carpenter's rule contains 2 ft.
The three points by help of which we have measured, the two
limiting points a, b upon the intensive line of sweets and the point
c which lies at unit-distance from the lower point a, can be estab-
lished, for comparative purposes, by a statement of the relative
amounts of sugar and water in the three solutions.
We may take another illustration of the same thing. Let the
horizontal line in Fig. 25 represent the complete scale of sensation
intensity in the sphere of
noise. And suppose that
we have given the two
noises ni and 0, a weaker
and a stronger noise due, ' ^
, r „• r Fig. 25.
perhaps, to the falhng of
two ivory balls from different heights upon ebony plates. By
selecting from a number of intermediate noises, we may deter-
mine the noise n that lies midway for sensation between m
and o. We may then write 7no = 2 mn = 2 710. That estab-
lished, we can take the distance no as given, and can compare
no with distances above 0, until we finally reach a point / such
that no = op. We may then write nip = 3 i7in. Again, we can
take mil as given, and compare it with distances below vi, until we
reach the point / at which Im = mn. We may then write Ip ^^ \ Ini.
And we can evidently go on to determine q, r, . . . and k,j, ... in
the same manner. So that, if we continue the procedure as far as
possible towards the limits of the horizontal Une of the Fig., we
shall finally have measured the entire range of noise-intensities in
terms of an arbitrary unit. Between the limits of the faintest and
the loudest noise there will be so-and-so many steps, or distances,
of the unit-magnitude mn. This is measurement of mind. —
In neither of the above instances, however, has the measurement
p
2IO The Inte7isity of Sensation
been methodical. We took any sweet-distance ab, and any noise-
distance mo. It would have been more methodical to determine,
at the outset, the two end-points of the total line of sweets and
noises, to determine what are called the liminal and the terminal
intensities of sweet-sensation and noise-sensation. Moreover, we
took as our units of measurement — and — -. Now we do not know,
2 2
in the first place, whether or not these units fit the scale, whether
they will divide it up without remainder. And, in the second place,
we have no reason to think that other psychologists will adopt
them : they do not recommend themselves, in any way, for general
use, as comparable with the c.g.s. units of the physical sciences.
§ 64. Liminal and Terminal Stimuli. — The sense-organ,
like any other mechanism, has a certain inertia, offers a
certain amount of frictional resistance to stimulus ; and has
also a definite capacity, transmits so much energy and no
more. Hence in all of the sense-departments there are
stimuli that are too weak to be sensed, and in all there
comes a point beyond which we cannot increase the inten-
sity of sensation by any further increase of stimulus, but
get the same response, over and over again, until the organ
breaks down.
Instances of subliminal stimuli are not far to seek. Some lights
are too faint to be seen : there are stars that, even on the darkest
night, remain invisible to the naked eye. Some sounds are too
weak to be heard : we know that the clock in the tower is ticking,
because we see the hands move ; but we have to climb the stairs
to hear it. Some pressures are too slight to be felt : we have no
knowledge, from the skin, of the flake of cigar-ash that has fallen
upon our hand : and so on.
Maximal stimuli fall less commonly within the range of our ex-
perience. It is, however, easy to assure oneself that there is a point
beyond which sugar cannot further sweeten or quinine make more
bitter, and that a continued increase of pressure, after it has carried
§ 64. Liminal and Terminal Stimuli 211
the sensation of pressure to a certain height, is felt not as pressure
but as pain. Dazzling lights and deafening noises set a like limit
to the functional capacity of eye and ear.
The magnitude of stimulus which evokes the sensation
at the lower end of the intensive scale, the first term of an
intensive series, is known technically as the liminal stimu-
lus. It may be determined as the stimulus which gives a
positive result, evokes a sensation, in one-half of a long
series of observations, while in the remaining one-half the
result is negative or doubtful. This value, so the mathe-
maticians tell us, is as nearly as possible identical with the
magnitude of stimulus which, if all sources of error were
completely eliminated, would call forth a barely perceptible
sensation. Since, however, the liminal stimulus is not a
constant but a variable, it cannot in strictness be repre-
sented by any single value, not even by the most probable
value; its formula must always be written x±y, where
X is the most probable value of the stimulus and ±j/ in-
dicates its range of variation.
The magnitude of stimulus which evokes the sensation
at the upper end of the intensive scale, the last term of an
intensive series, is known technically as the terminal stim-
ulus. Theoretically, it may be determined in the same
way ; in practice it is rarely approached, out of regard for
the integrity of the organ.
A variable quantity is a quantity which varies with change of the
conditions under which an observation is made. Thus, a raeasure-
rr nt in physics may vary with temperature, with humidity, with
st^^■ss, as well as with the delicacy of graduation of the measuring
instrument. The experimenter seeks, so far as possible, to keep
all the conditions constant while a measurement is in progress;
but even so there will be a slight range of variation. And the
212 The Intensity of Sensation
result is always stated in a qualified way, with reference to the
conditions.^
The liminal stimulus is, in this sense, a variable ; and its varia-
tion is due partly to the sense-organ and partly to the brain.
When we are tired, for instance, our sense-organs are dulled and
our general disposition is unfavourable to close work ; the hminal
stimulus is, accordingly, much larger than it is when we are fresh.
But even under the best conditions there is fluctuation. The or-
ganic mechanism, made up of sense-organ and brain, is extraor-
dinarily complicated, and complex machinery gets out of order
more easily than simple. Besides, the organic mechanism is
plastic, not rigid ; it is influenced by all sorts of things, — directly
by nutritive factors, indirectly by the state of all the rest of the
organism. The wonder is, indeed, not that the liminal stimulus
should be a variable quantity, but that it should be so nearly
constant, for normal persons, as in fact it turns out to be.
The exact determination of the liminal stimulus, that is, of the
amount of mechanical energy required to arouse a sense-organ to
response, is a very delicate and difficult matter, and a knowledge
of methods and results is of interest only to the special student.
It must suffice here to say that, for most of the organs, the measure-
ment has been made.^ In ordinary laboratory practice it is
enough to take a rough determination in empirical terms. Thus,
^ If there is anything constant in the world, it would seem to be the length
of the standard metre, which is the unit of reference for all linear measure-
ment in physics. Yet we are told that " from the result of many years of
comparison at the Bureau International [in Paris], the conclusion is reached
that the length of a standard can be absolutely guaranteed to an exactitude
of about 0.2 micron at all usual temperatures " (W. Hallock and H. T. Wade,
Outlines of the Evolution of Weights and Afeasiires and the Metric System,
1906, 256). In this statement, the measurement is qualified, tirst by reference
to temperature, and secondly by a statement of the range of variability; a
micron is a millionth of a metre. A measure that is correct to one five-
millionth is, to all intents and purposes, a constant ; it would be to all intents
and purposes a constant if the variation were far greater. In strictness,
however, it is a variable.
- See, for instance, S. P. Langley, Energy and Vision, Philosophical Maga-
zine, xxvii., 1S89, I.
§ 65- Just Noticeable Difference as Unit of Measurement 2\}^
a couple of hours of methodical work will settle the question from
what height a leaden shot of a given weight must fall upon a glass
Fig. 26. Acoumeter for determining tlie Stimulus Limen of Noise. ^SS, set-
i'Crews (two of the three are shown), supporting a wooden platform. M, mi-
crometer screw at the centre of the platform, with scale beside it. FF, spring for-
ceps, lying on the head of M, and carrying a small shot for dropping on the glass
plate above W. The sliot rebounds, and falls noiselessly into a padded trough.
plate if the noise is to be just audible to an observer seated 10 m.
away. Results of this kind are useful, as means of comparison,
but have no general scientific value. ^
§ 65. The Just Noticeable Difference as the TTnit of Meas-
urement. — We defined the liminal stimulus, or the just
noticeable stimulus, as that magnitude of stimulus which
evokes a sensation in one-half of a long series of obser-
vations, while in the remaining one-half the result is nega-
tive or doubtful. If, now, we take a second stimulus of
the same magnitude, and gradually increase its intensity
by very small amounts ; and if, at every step of this
progression, we compare the sensations set up by the
two stimuli : then we shall presently arrive at a stimulus-
difference which behaves in the same way as the liminal
214 The Intensity of Sensation
stimulus itself. We shall, that is, come to a difference
which is perceived as a difference in one-half of a long
series of observations, while in the remaining one-half
there is no perceptible difference, or the observer is in
doubt. And the procedure may be repeated, again and
again, until we have traversed the whole or a large part
of the intensive scale.
It has been suggested that this difference, which is
known as the just noticeable difference of stimuli, or as
the differential limen of sensation, may be regarded as the
natural unit of the scale of sensible intensity. The zero-
point of the scale is given with the liminal stimulus, or (as
it is called, with reference to sensation) the stimulus limen.
The end-point of the scale is given with the terminal
stimulus. The units of the scale will then be given
with the series of just noticeable differences as defined
above. For, it is said, the just noticeable differences cor-
respond to least distances upon the sense-scale, minima
of sensible distance. Now least distances, being the
smallest possible distances at which sensations can be
distinguished, are necessarily equal distances ; and equal
distances are the very things that we are in search of,
to furnish the subdivisions of our mental scale.
Logically, however, this argument is not sound. It is
by no means self-evident that least steps, at various parts
of the sense-scale, should also be equal steps. A given
difference between sensations might be the least per-
ceptible difference, and yet, as compared with another
least perceptible difference from another part of the scale,
might be larger or smaller. The equality of just notice-
able differences must, then, be proved ; it cannot be as
sumed. The appeal lies to the results of experiment.
§ 66. Weber'' s Law 215
We shall see in the next § 66 that the results of experiment
are ambiguous. Nevertheless, the preponderance of the experi-
mental evidence is, in the writer's judgment, very definitely in
favour of the equality of the just noticeable differences ; the dis-
crepant results can be accounted for in terms of known sources
of error. We return to the point later.
In the meantime : Why, it may be asked, should we not appeal
to introspection? Why should we not directly compare two just
noticeable differences, from different regions of the intensive
scale, and see if they are alike or different? — For the simple
reason that they are the results of measurement. If mere ob-
servation were enough, we should not need to measure at all,
in any field of science. If we could estimate the sixtieths of a
circle, it would not be necessary to mark off the clock-face into
minutes ; if we could estimate spaces of so many feet, it would
not be necessary to secure architects' plans before we built a
house. The just noticeable difference is not determined by a
single introspective observation, and cannot be carried in the
head as a standard of magnitude : it is the calculated result of
a long series of introspective observations, and stands for a most
probable or representative value. The whole object of measure-
ment is to carry accuracy into fields in which mere observation,
simple estimation, is inaccurate.
§ 66. Weber's Law. — If we determine a series of just
noticeable differences, in the middle region of the inten-
sive scale, we find a very simple relation between change
of sensation and increase of stimulus. At the beginning,
where the stimuli are relatively weak, only a small addition
is required to effect a noticeable increase in the intensity
of sensation ; as the series progresses, the additions become
larger and larger; and towards the end, where the stimuli
are relatively strong, the largest additions are needed.
And this progressive increase of the stimulus-increment
is uniform : so that, in general, the series of least sense-
2i6 The Intensity of Sensation
distances corresponds to a series of stimulus-increments
that are, approximately, equal fractions of the original
stimulus. Thus, if we start with the stimulus lo, and find
a just noticeable difference with the stimulus ii, then
when we come to 20 we shall find a difference with 22,
when we come to 30 we shall find it with 33, and so on.
If, therefore, we could regard all just noticeable differ-
ences as equal, — all least sense-distances as equal sense-
distances, — we could sum up the results of our experiment
by saying that an arithmetical series of sense-distances
corresponds to a geometrical series of stimulus-values.
We should have, on the side of sensation, a series of in-
tensities o^, I, 2, 3, 4, . . ., lying at points equidistant
upon the intensive scale ; and we should have on the side
of stimulus a progression of the order R, R{\ -\- r),
R{i -h rf, R(i+ry, . . ., where R is the first stimulus
taken (here the stimulus 10, correlated with the sensible
intensity o), and r is a certain fractional part of R (here,
one-tenth).
We can put the question to the test of experiment. Let
us take, for instance, the case of sensations of light. We
know, from many investigations, that a succession of just
noticeable differences of light-sensation is paralleled by a
geometrical series of physical light-stimuli. Now we have
recourse to larger, supraliminal differences of light-sensa-
tion. We set up on the colour-mixer (Fig. 4) three com-
pound discs of black and white paper. The two outer
discs are adjusted to give on rotation a dark and a light
1 This O is not, of course, the zero-point of intensity of sensation at large:
it is only the zero-point of our arbitrarily selected scale, and therefore stands
for the intensity of sensation with which the experiments begin. — If we are
measuring a table with a foot-rule, we begin with o, in just the same way;
but we do not mean that space at large begins where our rule begins.
§ 66. Weber s Law 217
grey respectively ; they remain constant throughout the
experiment. The proportion of black and white in the
middle disc is varied, until a grey is obtained which lies,
for sensation, midway between the extremes. Our three
rotating discs then show two equal sense-distances, of
much more than liminal extent. What of the stimuli .'' The
stimuli, measured by means of the photometer, prove to
form a geometrical series ; their photometric values differ,
not by equal amounts, but by relatively equal amounts.
Here, however, is the answer to our question. Here we
have an arithmetical series of sense-distances, two succes-
sive distances guaranteed equal by introspection, corre-
sponding to a geometrical series of light-stimuli. Since,
then, we found a geometrical series of stimuli correspond-
ing to our series of just noticeable differences of sensa-
tion, it follows that these just noticeable differences must
themselves be psychologically equal. The just noticeable
difference may be accepted as the unit of the intensive
scale.
A strictly methodical procedure is as necessary in this case as
it was in the case of the just noticeable difference : we do not dis-
cover the equality of the two sense-distances by direct introspec-
tion, but we calculate the most probable point of equality from a
long series of introspective observations. The difference m the
two experiments is this : that in the determination of the just
noticeable difference the observer reports the likeness or differ-
ence of two sensations, whereas in the present experiment he
reports the likeness or difference of two sense-distances. Hence
we have, with supraliminal differences, an introspective control
that is lacking for the liminal.
At the same time, the change from comparison of sensations to
comparison of sense-distances may have a decided influence upon
the observer's judgment. We said above ''^ 65) that the results
2i8 The Intensity of Sensation
of experiment were ambiguous. As a matter of fact, several recent
investigations have led to the result that equal supraliminal dis-
tances, determined in the way just described, do not contain —
as on our view they should — equal numbers of just noticeable
differences, but that, on the contrary, the higher of the two con-
tains fewer just noticeable differences than the lower.^ And this
result has been interpreted to mean that the just noticeable differ-
ence is a magnitude that increases with increase of stimulus, so
that it cannot serve as the unit of measurement. However,
another interpretation is possible. The upper distance, which
contains the fewer just noticeable differences, may in reality be
shorter than the lower ; the observer's judgment that the two dis-
tances are equal may be erroneous. For one very dangerous
source of error, in experiments upon the comparison of supra-
liminal sense-distances, is that the observer tends to judge, not in
terms of sensation, but in terms of stimulus. He thinks, not of
the light-sensations, but of the grey papers ; not of the sounds
heard, but of the heights from which the balls must have fallen to
give those sounds (§ 62). If this error, which is known techni-
cally as the stimulus-error, creeps into the observations, then the
stimuli which delimit the two sense-distances are hkely to form,
not a geometrical, but an arithmetical series. The consequence
is plain. The upper distance must now contain fewer just notice-
able differences than the lower ; it is not psychologically, but only
physically, equal to the lower. The observer, who was called
upon to space out intensities of sensation, has really spaced out,
in the light of his everyday experience, characters or properties
of material things ; and his spacing has, naturally, led to an
approximate physical equality. — This, in general, is the writer's
explanation of the discrepancies in the experimental results.
The law that equal sense-distances correspond to rela-
tively equal differences of stimulus is known as Weber's
Law. It has been found to hold, at least approximately
1 See, e.g., W. Ament, Ueber das Verhaltnis der ehenmerklichen zu den
iibermerklichen Unterschieden bei Licht- und Schallintensiidien, in Wundt's
Philosophische Studicn, xvi., 1 900, 135.
§ 66. Weber's Law
219
and within a certain middle
region of the intensive scale,
for intensities of noise and
tone, of light, of pressure,
of various kinaesthetic com-
plexes (lifted weights, move-
ments of the arm, movements
of the eyes), and of smell.
Its validity in the fields of
taste and of temperature is
doubtful. It may possibly
hold for affection (§ 73), as
well as for sensation ; but
no experimental test in the
sphere of feeling has as yet
been made.
Fig. 27. Generalised representation of
the relation between S and jR formu-
lated in Weber's Law. Equal sense-
steps are marked off as abscissas,
and the corresponding /?-values are
entered as ordinates.
In 1834 the German physiolo-
gist E. H. Weber (i 795-1878)
performed some experiments with weights and visual distances
which seemed to establish a constancy of the relative differ-
ential limen. Pie accord-
ingly concluded that " what
we perceive, when we are
discriminating between ob-
jects, is not their absolute
difference, but rather the
proportion which the differ-
ence bears to their magni-
tude." G.T. Fechner(I8oI-
I887) gave the law a precise
phrasing, and put it to elabo-
rate experimental test. Al-
though Fechner's modesty
led him to name it after
Fig. 28. Pair of black-and-white discs for
the demonstration of Weber's Law. The
brightness of the left-hand disc increases,
from the centre towards the periphery, in
geometrical progression ; that of the right-
hand disc increases in arithmetical pro-
gression. — A. Kirschmann, American
Journal of Psychology, vii., 1896, 386 ff. ;
E. C. Sanford, A Course in. Experimental
Psychology, 1898, 335 f.
220 The Intensity of Sensation
Weber, we might more correctly term it Fechner's Law or the
Weber-Fechner Law.
Fechner formulated the law in the equation S=c log R, where
S stands for intensity of sensation, R for stimulus, and c for a
constant factor. Fechner's understanding of the formula was
wrong ; he fell into the very common error which we discussed
in § 62. The formula itself, however, may be retained. Here
is its derivation in terms of supraliminal sense-distances.
We know, from our experimental results, that the magnitude of
a sense-distance is dependent upon the quotient of the two R that
limit it. Let the dependence be expressed by the mathematical
sign of function, f. Then we have, for two successive sense-
distances, the equations :
Adding these equations, we get :
55=/(t)+/(f
But we know, again from our experiments, that :
and, of course.
Ar) \r\' r]
We have, then, finally :
/(|)-/(t)=/(|)-(|
Now the only continuous function that can satisfy an equation of
this form is, as we learn from the mathematical text-books, a
logarithmic function. Hence we may write (inserting a constant
factor, c, to indicate our choice of some particular logarithmic
system) •
§ 6/. Theory of Weber's Law 221
S-iS^ = c log -p^
^'s^'s = ^ log — ^
Or, in general, if ^o and ^o denote the S and R with which we
start, and S and R themselves denote any other sensation and its
corresponding stimulus-value :
^^o = '^log -^.
And, lastly, if we denote the intensive ^'-distances reckoned from
an initial -So by S, and the ^^-intensities calculated in terms of the
corresponding R^ by R, we have simply :
S = ^ log R.
The formula may also be derived, though not without help from
the calculus, in terms of liminal sense-distances or just noticeable
differences.
§ 67. Theory of Weber's Law. — Every sense-organ, we
said in § 64, offers a certain amount of frictional resistance
to stimulus ; it is this resistance that explains the fact- of
the stimulus limen. There can be no doubt that the dif-
ferential limen is a fact of the same order, to be explained
in the same way. Whatever the present state of the
sense-organ may be, whatever excitatory processes are
already in progress within it and within the connected
parts of the central nervous system, the same sort of re-
sistance is offered to an incoming stimulus. When the
nervous machine has once been started, it will continue to
work, without interruption, so long as adequate stimulation
is continued : or, in other words, when sensation has once
been set up, it will follow, continuously, the changes of
stimulus. But if the stimulus cease for a moment to act
222 The Intensity of Sensation
the machine becomes inert, and must be started up again
as if it had completely run down.
Intrinsically, therefore, the relation between sense-dis-
tance and stimulus-difference, which is expressed in
Weber's Law, is a continuous relation; intensity of sen-
sation is a continuous function of intensity of stimulus.
In this sense, Weber's Law explains the facts of sensible
intensity just as Hering's theory of vision or Helmholtz'
theory of audition explains the facts of sensible quality.
Weber's Law is itself the theory of sensible intensity.
But the continuous function is changed, under certain con-
ditions, into a discontinuous function ; we have to explain
the limens. And we explain them, stimulus limen and
differential hmen alike, by reference to the inertia of the
nervous mechanism.
An illustration may help to make things clearer. If a magnetic
needle is suspended at die centre of a circular coil of wire, and an
electric current is sent through the wire, the needle is deflected
from its position of rest. The angle of deflection is, however, not
directly proportional to the strength of current. As the strength
of current is increased, by equal amounts, the deflection of the
needle becomes progressively smaller and smaller. The mathe-
matical expression of the relation is very simple. If ^ is the num-
ber of amperes in the current, k a constant, and the angle of
deflection, then a = k tan 6. — Here is an expression that is very
like the S = c log R of Weber's Law ; and both formulas are the
expression of a continuous function.
Now suppose that the needle is hanging steady, whether at the
zero-point of its scale or at any other point at which it is held by
the current in the coil, and that we increase the current very
slowly. At first we get no movement at all. Presently, however,
when the current has been increased by a certaui amount, the
needle goes with a little jump to the position which the formula
requires. In this case, we have two phenomena before us. On
§ Gy. Theory of Weber's Law 223
the one hand, the needle is a magnetic needle, and the amount
of its deflection is a continuous function of the current in the coil.
On the other hand, the needle does not move, from any position
of rest, without friction ; so that under the conditions of our
second experiment we observe, not a continuous movement, but a
series of jerks. In just the same way, we have for intensity of
sensation the continuous function expressed in Weber's Law ; but
we also have the stimulus and the differential limens as facts of
friction. —
From the point of view of experimental psychology, Vv'eber's
Law has a very special significance, as summing up the results of
the first successful attempt at mental measurement (§ 63). At
the present time, methods of measurement, — metric methods, as
they are technically called, — have been employed in many other
fields of the mental life. Indeed, while little has been done in
comparison with what still remains to do, there is no doubt that,
in principle, every single problem that can now be set in psycho-
logy may be set in quantitative form. The psychological text-
books of the next century will be as full of formulas as the text-
books of physics are to-day.
The Law is also of great importance in our daily life, since
wherever it is valid we are governed, not by the differences, but
by the quotients of the intensive stimuli that affect us. It is be-
cause Weber's Law holds for a middle range of light-intensities
that we are able to ignore the manifold changes of illumination to
which we are exposed in the course of the daylight hours. It is
for the same reason that the painter, who cannot at all reproduce
by his pigments the absolute intensities of light in nature, can
nevertheless furnish a recognisably true copy of any natural scene.
And again, it is because Weber's Law holds for a middle range of
sound-intensities that a large block of seats in the concert-room,
at a moderate distance from the stage, can all be sold at the same
prices and all have equal advantages for hearing.
224 The Intensity of Sensation
References for Further Reading
§§ 62-67. A general account of the problems of mental mer^urement
is given in the author's Experimental Psychology, II., i., 1905, Intro-
duction ; and an historical sketch of the course of experiment, ibid., II.,
ii., 1905, Introduction : The Rise and Progress of Quantitative Psy-
chology. References of especial importance are : E. H. Weber, Der
Tastsinn und das Gemeitigefuhl, an article in R. Wagner's Handwort^
erbuch der Physiologic, iii., 2, 1846, 481 (also published separately,
1849, 1 851); G. T. Fechner, Element e der Psychophysik, 2 vols., i860
(1889, 1907), esp. i., chs. vi.-x. ; G. E. Muller, Zur Grundlegung der
Psychophysik, 1878 ; Die Gesichtspunkte und die Tatsachen der psycho-
physischen Methodik, 1904 (also in L. Asher and K. Spiro, Ergebnisse
der Physiologic, II., ii., 266); J. D^^hotni, Elements de psychophysique
generate et speciale, 1883 ; Examen critique de la hi psychophysique, sa
base et sa signification, 1883; H. Ebbinghaus, Ueber negative Empfin-
duttgswerte, Zeitschrift f Psychologic u. Physiologic d. Sinnesorgane, i.,
1890, 320, 463; W. Wundt, Grundz'uge d. physiologischen Psychologic,
i., 1908, 525.
AFFECTION
§ 68. Feeling and Affection. — The word 'feeling' is used
in a great variety of meanings. A thing feels rough of
smooth, hard or soft, sharp or blunt, firm or shaky, warm
or cold, elastic or brittle, thick or thin, clammy or oily.
We ourselves feel hungry or thirsty, fresh or tired, ener-
getic or lazy, strong or weak, well or ill. We also feel com-
fortable or uncomfortable, we feel at home or strange, at
ease or ill at ease, natural or constrained ; we feel happy,
cheerful, restless, angry, irritable, eager, calm. We feel
hopeful, despondent, grieved, hurt, injured, relieved, con-
tented, gloomy, anxious, annoyed. We feel indifferent,
and we feel sympathetic ; we feel the difficulty of an objec-
tion, the truth of an argument, the nobility of a character,
the sacredness of a belief. ' Feel ' and ' feeling ' seem,
indeed, to be psychological maids of all work ; they can do,
in the sentence, practically anything that a verb and a sub-
stantive can be called upon to do. There is little hope, one
would think, of turning them to strict psychological ac-
count, and of giving them a place in a list of technical
terms.
Let us see what happens, however, if we contrast feeling
with sensation. Suppose that I say to you : The organ-
ism not only senses, but also feels ; consciousness is made
up, not of sensations alone, but of sensations and feel-
ings. Here, surely, there is a hint or suggestion, vague
though it may be, of the true psychological meaning of
Q 325
226 Affection
' feel ' and ' feeling.' You realise that stimuli do something
more than arouse sensation ; they give rise to processes of
a different kind, to 'feelings' in a special sense; we do
not merely take the impressions as they come, but we
are affected by them, we feel them ; and what we feel is
their agreeableness or disagreeableness, their pleasantness
or unpleasantness. Colours and tones, tastes and smells,
may be pleasing or unpleasing just as obviously and
just as directly as they are red or c, bitter or musky ;
and their pleasant or unpleasant character is a matter of
feeling.
We have gained something, then, by contrasting feeling
with sensation ; we have found a fairly definite meaning
for the term, and we have marked off a new field of mind
for further study. At this point, unfortunately, the views
of modern psychologists begin to differ ; the psychology of
feeling is still, in large measure, a psychology of personal
opinion and belief. The writer holds that there is an ele-
mentary affective process, a feeling-element, which in our
own minds is coordinate with sensation and distinguishable
from it, but which is nevertheless akin to sensation and is
derived from the same source, made (so to speak) out of
the same kind of primitive mental material : this elemen-
tary process is termed affection. He holds, further, that
there are only two kinds or qualities of affection, pleasant-
ness and unpleasantness. The principal reasons for and
against this view are set forth in the following sections.
If we look carefully at a list of ' feelings,' such as that given at
the beginning of this § 68, we find that the experiences in question
fall into three main groups. We have, in the first place, certain
perceptions of touch : hardness, roughness, soliditv, etc. We
have, secondly, certain complexes of organic sensations : hunger,
§ 68. Feeling and Affection 227
fatigue, etc. And we have, thirdly, a number of mental processes
which differ markedly in various ways, but which are all character-
ised by the predominance of pleasantness or unpleasantness : joy,
sorrow, anger, difficulty, etc.
In ordinary speech, we oppose ' feeling ' to * intellect' ; the man
who is swayed by feeling is contrasted with the man who acts
coolly and deliberately, by reasoned judgment. This use of the
term is so natural and so habitual that we shall do well to keep it
in psychology. ' Feeling ' will then be the general name for all
sorts of pleasant-unpleasant experience, for every form of emotion,
mood, sentiment and passion. All the items in the third division
of our list will be rightly called feelings.
But ' feeling ' is also used, in psychology, in a narrower and
more technical sense. It denotes a simple connection of sensa-
tion and affection, in which the affection preponderates. Hunger,
for instance, is a sensation. But we may speak of a feeling of
hunger if we mean a jolly hunger or a gnawing hunger ; if, that is,
we mean a pleasantly stimulating or an unpleasantly insistent
hunger. Pain, again, is a sensation ; and it is a sensation that, at
different intensities and under different circumstances, may be
pleasant, indifferent, or unpleasant. Usually it is unpleasant, and
strongly unpleasant. When this is the case, we speak in psy-
chology of a feeling of pain. And in just the same way we may
speak of a feeling of fatigue, of nausea, of drowsiness, of freshness,
of bodily strength. All the items in the second division of our
list are rightly called feelings, in this narrower meaning of the
term, provided that the sense-quality is accompanied by an inten-
sive affection, pleasant or unpleasant. They are feelings proper,
or sense-feelings.
The items of the first division are not feelings at all, but
perceptions ; and they are termed perceptions, as well as feelings,
in the language of everyday life. In their case, psychology has
no choice ; the name ' feelings ' must be given up. We shall,
however, have something further to say about them in § 69. —
In summary, then, we have the following terms. Affection is
an elementary mental process. Affection is the characteristic ele-
ment in emotion, in love and hate, joy and sorrow, just as sensa-
228 Affection
tion is the characteristic element in perception, and image the
characteristic element in idea (§ lo). Feelijig in the narrowei
meaning of the word, sense-feeUng, is a simple connection of affec-
tion and sensation, in which the affective element predominates :
in this sense we are said to feel sleepy, tired, hungry, rested.
Feeling, in the wider meaning of the word, is the general name
for the affective side of our mental life : in this sense we are said
to feel glad or sorry, worried or hopeful, proud or ashamed.
There is no reason why the two meanings of ' feeling ' should
lead to confusion, and we shall be careful not to confuse them in
this book.
§ 69. Affection and Sensation. — We have now to enquire
into the nature of affection, considered as an element of
mind ; to ask how it resembles and how it differs from
sensation. We will take the resemblances first.
Sensation was defined, in § 12, as an elementary mental
process which is constituted of at least four attributes, —
quality, intensity, clearness and duration. Now affection
has three of these attributes, — quality, intensity, and
duration ; it thus appears as a process of the same general
kind as sensation, and it may be defined on the same lines,
by reference to attributes which are common to both.
Affection has qualities : it has at least the two qualities of
pleasantness and unpleasantness, and (as we shall see in
§ 72) some psychologists believe that it has many more.
Affection shows differences of intensity : an experience
may be mildly pleasant, slightly disagreeable, or wonder-
fully pleasant, unbearably disagreeable. And affection
shows differences of duration : pleasure may be momentary,
or may persist as a permanent mood ; and unpleasantness
behaves in the same way. So far, then, there is a general
resemblance between affection and sensation.
Again : we have seen that certain sensations show the
§ 6g. Ajfection and Sensation 229
phenomenon of adaptation. In many departments of sense
— in pressure, in temperature, in smell, in taste — a sensa-
tion may disappear, fade out of consciousness, if the stimu-
lus is continued. Sight, too, obeys the law of adaptation.
We do not, it is true, become blind under visual stimula-
tion ; but our vision is reduced to a neutral grey, the
quality of the persistent central excitation (§ 18). Pre-
cisely the same phenomenon of adaptation appears in the
case of affection. If we are exposed for a long time
together to the same stimulus, we may cease to be affected
by it at all. The cookery of a foreign country is, when we
first make acquaintance with it, distinctly pleasant or
unpleasant ; but in either case it quickly becomes indiffer-
ent. Dwellers in the country do not find the pleasure in
country sights and odours that the townsman does ; they
have grown used to their surroundings. The whir of a
sewing machine in the room above that in which we are
working may at first be extremely annoying ; but as we
become accustomed to it, its unpleasantness disappears.
There is, indeed, no region of mind in which this law of
affective adaptation fails to manifest itself. During the
first few weeks of our stay in a beautiful neighbourhood
we may be continually delighted with the colours and
forms of the landscape. But we soon grow indifferent
to them : fields and hills and streams are seen as clearly
as ever, but they have ceased to excite pleasure. On the
other hand, a piece of vulgarity which at first offends us
may be taken as a matter of course if constantly repeated
among those in whose company we are thrown. Here is a
second point of likeness between affection and sensation.
The fact of affective adaptation seems to show as clearly, in
these instances, as the fact of olfactory adaptation showed in the
230 Affection
instances of § 32. Nevertheless, it has been disputed ; some
psychologists explain the phenomena in terms of sensory adapta-
tion. It is, they say, the cookery and the landscape that we grow
accustomed to, not the disagreeableness of the dishes and the
beauty of the landscape. There are, that is, as many possibilities
of sensory adaptation as there are attributes of sensation ; we
may become adapted to intensity and clearness and duration,
precisely as we become adapted to quality. If a friend asks us :
"Doesn't that sewing machine annoy you?" we shall be likely to
reply : " No ! it would if I heard it, but I simply don't hear it any
more." And the answer, these psychologists say, is correct ; we
have become adapted, not to the quality of the noise, but to its
intensity and clearness ; we have ceased to attend to it ; it is no
longer effective as a stimulus, and so its original disagreeableness
has naturally lapsed. We have grown used, not to the disturbance,
but to the noise \ and the noise is now, as a result of our adapta-
tion, both weak and obscure.
In the case of the sewing machine, this explanation is possible.
But it is not convincing ; for we may very well have become
adapted both to the sensation and to the affection ; the two adap-
tations may have gone along side by side. And in other cases, in
which the stimulus is not continuous but intermittent (mealtimes,
country walks, the behaviour of acquaintances), affective adapta-
tion seems obvious. I may be keenly aware of the odour of
garlic, and yet be entirely indifferent to it. I may take sharp
note of the fact that the person with whom I am talking begins
to use his toothpick, and yet have no feeling of disgust. We shall
see, in § 78, that it is possible to attend without feeling ; and if
it is, if the sensation that fills the chief place in consciousness may
be indifferent, then affective adaptation is certain. The objection
shows, however, — what we have already insisted on, — that it is
hardly possible to take a single step in the psychology of feeling
without meeting contradiction and conflict of opinion.
Thirdly, the processes of pleasantness and unpleasant-
ness show a strong introspective resemblance to organic
sensations. Pleasantness seems akin to health, drowsiness,
§ 6g. Affection and Sensation 231
bodily comfort, repletion; unpleasantness seems akin to
pain, bodily discomfort, over-fatigue, lassitude. No doubt
these experiences, as they present themselves in everyday
life, are more than sensations ; they are sense-feelings,
complexes of affection and sensation ; the total conscious
experience that we call health, for instance, contains a
pleasant affection along with various, kinaesthetic and
other, sensory processes. Still, if we analyse repletion
or fatigue, and so far as possible set off the affective
element from the constituent sensations, the resemblance
appears to persist. Affection is like organic sensation in
much the same sense in which sensations of taste are like
sensations of smell (§§ 29, 36).
In fine, affection resembles sensation in the nature of
its attributes and in its behaviour when a stimulus is long
continued, while the qualities of affection, pleasantness
and unpleasantness, show an intrinsic likeness to the
qualities of organic sensation. What, now, are the differ-
ences
The first difference is this: that affection lacks the attri-
bute of clearness. Pleasantness and unpleasantness may
be intensive and lasting, but they are never clear. This
means, if we put it in the language of popular psychology,
that it is impossible to attend to an affection. The more
closely we attend to a sensation, the clearer does it be-
come, and the longer and more accurately do we remem-
ber it. But we cannot attend to an affection at all ; if we
attempt to do so, the pleasantness or unpleasantness at
once eludes us and disappears, and we find ourselves con-
templating some obtrusive sensation or image which we
had no desire to observe. If we want to get pleasure from
a concert or a picture, we must attend to what we hear
232 Affection
and what we see ; so soon as we try to attend to the
pleasure itself, the pleasure is gone.
The lack of the attribute of clearness is sufficient, in
itself, to differentiate affection from sensation ; a process
that cannot be made the object of attention is radically
different, and must play a radically different part in con-
sciousness, from a process which is held and enhanced by
attention. And it should be noted that lack of clearness
distinguishes affection from organic sensation as definitely
as from sensations of sight or hearing ; we have no diffi-
culty in attending to the sensory components of hunger
and thirst and fatigue.
There is, however, a further difference. Pleasantness
and unpleasantness are, what their names imply them to
be, opposites. The opposition is not a matter of contrast,
as this term is used in the psychology of sensation, al-
though it is often referred to as contrast: it is rather a
matter of incompatibility in consciousness. There is no
similar opposition of sensory qualities.
It was said in § 26 that tones are intrinsically harmonious,
colours intrinsically antagonistic. This statement means that the
nervous processes underlying visual sensation are aoitagonistic, and
that colours themselves offset one another, show one another up ;
whereas the nervous processes aroused by the sympathetic vibra-
tion of the basilar fibres are confluent, synergic, and tones them-
selves show a tendency to blend or fuse with one another. It
must, however, be understood that the antagonism of visual sensa-
tions is not at all the same thing as the incompatibility of pleasant-
ness and unpleasantness : for, first, the antagonistic qualities of
black and white are actually connected by the series of greys, due
to the admixture of the central grey ; and we might, with similar
aid from the centre, obtain series of sense-qualities connecting R
with G) and B with Y. Pleasantness, on the other hand, is con-
§ 69. Affection and Sensation 233
sciously at odds with unpleasantness ; the opposition of the two
processes belongs to the essence of them as experienced. And
secondly, there is no such thing as affective contrast, in the strict
meaning of the term ; the pleasure of convalescence is not en-
hanced by the unpleasantness of past suffering, as red is enhanced
by green. Convalescent comfort is itself the opposite, the con-
scious antithesis, of the discomfort of sickness ; but it is not in-
fluenced by that discomfort.
It is true, however, that we often speak loosely of contrast when
we are referring to affective opposition. An ordinary man, seen
by the side of a dwarf, looks unusually large ; the same man, seen
by the side of a giant, looks unusually small. We say that he
looks large and small by contrast. The fact is that we feel a sort
of contemptuous pity for the dwarf, and a surprised admiration
for the man beside him ; and again, a contempt for the man and
an admiration for the giant. What we have laid to the account of
a spatial contrast is really due to affective opposition. —
It is worth noting that this affective opposition is reflected in
certain of the cutaneous perceptions that in ordinary speech are
termed feehngs (§ 68). We oppose warmth and cold, — not as
sensory qualities, for they belong to different senses ; but as
pleasant and unpleasant. On the whole and in general, warm and
smooth and soft things are pleasant to the touch, and cold and
rough and hard things are unpleasant. Indeed, whenever we find
in consciousness an opposition of this sort, we may be sure that it
is an opposition due to the presence of affective processes along-
side of the sensations. And in so far as we oppose warmth to
cold, smoothness to roughness, for affective reasons, in so far there
is some justification for giving these processes the name of feel-
ings.
Other Distinguishing Characters of Affection. — We have dis-
tinguished affection from sensation on the negative ground of lack
of clearness, and on the positive ground of qualitative opposition.
It has been urged, further, that sensations are the objective and
affections the subjective elements of consciousness. No one,
however, has found a satisfactory psychological definition of these
terms. We may, perhaps, call sensations objective in the sense
234 Affection
that iKey can stand alone in consciousness, independently of affec-
tion ; and we may call affections subjective in the sense that they
never appear alone, but always and of necessity as the companions
of sensation. But this is itself a disputed point. Again, it is urged
that all sensations may be locahsed in space, while affection is not
localisable. But it is argued, on the other side, that tones and
odours sometimes resist all our efforts to place them ; while the
pleasantness of a sweet taste, and the unpleasantness of an
organic pain, are localised along with the taste and the pain
themselves. Yet again, it is urged that the sensation is nor-
mally more intensive than the image, the perception than the
idea ; but that the affection which accompanies the idea is nor-
mally more intensive than that which accompanies the perception.
But, if one psychologist informs us that " only the very highest
degrees of sensory agreeableness and sensory disagreeableness are
now able to overpower the ' higher ' feelings," another asserts,
just as positively, that " ideal pains and pleasures are not com-
parable in mere intensity with sensuous pains and pleasures."
Contradiction could hardly be flatter !
In all these controversies, the writer leans to the affirmative
side, the side which affirms a difference between affection and
sensation. He does not believe, for instance, that a purely af-
fective process may enter consciousness alone, as the herald of a
coming sensory process, or that it may lag behind in consciousness
alone, after its sensory companions have disappeared, — although
both these statements are freely made. Pie finds a sort of flimsi-
ness or softness or yieldingness in the texture of pleasantness and
unpleasantness ; their quality is like that of certain organic sensa-
tions, but they are less hard, less stable, less self-supporting. This
difference, which is difficult to express in words, is probably con-
nected with the presence or absence of the attribute of clearness ;
but there is no reason why it should not be termed a difference of
objective and subjective. Again, the writer believes that affec-
tions are always coextensive with consciousness, diffused over all the
sensory contents present at the time ; and that, if the pleasantness
of a taste is localised in the mouth, that is simply because con-
sciousness itself, under the experimental conditions, has beeo
§ 69- Affection and Sensation 235
narrowed down to a taste-consciousness. Finally, there seems to
be no doubt that, in the adult human mind, the ideal feelings are
usually stronger than the sensuous. I fall down on a slippery
path, and hurt myself; but niy first thought is " How stupid of me
to slip ! " I sit in a draughty concert hall with the certainty of a
neuralgia; but I am afraid of making myself ridiculous, and so I
remain in my chair. It is a raw evening, and I have a Httle cold ;
but I go to see ray friend, because I do not want to disappoint
him. Were it worth while, illustrations of this kind could be
multiplied a hundredfold. It is not worth while, because the
question at issue cannot be decided by casual observation. Di-
vergence of opinion is inevitable, until the experimental method
has been brought to bear, systematically, upon the problems of
feeling. In tTie meantime, we must be content to mark off affec-
tion from sensation by the two salient characters described in the
text.
The Question of Mixed Feelings. — It would seem that, if
pleasantness and unpleasantness are opposite and incompatible,
they cannot coexist in the same consciousness, — that we cannot
feel pleased and feel displeased at one and the same moment. A
consciousness, however, is a very complicated affair ; it is made
up of a large number of elementary processes ; and there is no
doubt that the nervous system may be exposed, in different
quarters, to stimuli some of which, if felt by themselves, would
be felt pleasantly and some of which, if felt alone, would be felt
unpleasantly. Hence it becomes a question of fact whether these
various stimuli, acting together at the same time, give rise to a
single resultant affection, either pleasant or unpleasant ; or
whether every stimulus sets up its own localised affection, so that
consciousness may be a mosaic of separate pleasantnesses and
unpleasantnesses.
Language favours the second alternative. We go back to school
after the holidays with mixed feelings ; we visit our old home,
after a long absence, with mixed feelings ; there is, indeed, hardly
anything that we may not look upon, or look back or forward to,
with mixed feelings. Juliet tells us that parting is sweet sorrow,
a pleasant unpleasantness ; and Tennyson's Geraint watches the
236 Affection
mowers, whose dinner he has just eaten, with humorous ruth, that
is, with a pleasantly unpleasant feeling. There is no pleasure, we
are told, without its alloy of pain ; there is no despair so dark that
it is not lightened by a ray of hope. Popular psychology makes
no question about mixed feelings ; and a psychologist of standing
writes that " almost all mental states which are marked by strong
feeling in the case of developed minds are mixed feelings."
On the other hand we know that a single trifling annoyance
may colour our whole mood. When Othello behaves unkindly
to Desdemona, she excuses him on the ground that he is worried
by affairs of state; "for let our finger ache," she says, "and it
indues our other healthful members ev'n to that sense of pain."
We know, too, that if we are in a particularly good temper we
take everything good-temperedly ; we may even ask pardon of
the man who has trodden on our corns. And there is really no
proof that the pleasantness and unpleasantness of the mixed
feeling are strictly coincident : Juliet may be alternately glad
and sorry ; sorry now to part from Romeo, but glad the next
moment that he is there, as her lover, to be parted from, and
glad a moment after in the thought of seeing him again. How
quickly the pendulum of feeling may swing we see in the case
of the child, who is crying bitterly at its hurt and then, within
a few seconds, is smiling over a lump of sugar.
The final appeal lies, of course, to experiment. Unfortunately,
but few experiments have so far been made, and the results of
these few are not wholly clear. It is safe to say, however, that
the tendency of the experimental evidence is decidedly negative ;
mixed feelings are, in the laboratory, the exception and not the
rule ; and the exceptional cases are themselves not above sus-
picion. The writer has never found, in his own experience, a
definite and unmistakable case of mixed feeling.
§ 70. Other Views of Affection. — Affection, as we have
described it, is an elementary mental process that is both
like and unlike sensation. The resemblance is so great
ihat the two processes are evidently derived from a com-
§ 70- Other Views of Affection 237
mon mental ancestor ; the difference is so great that we
have no choice but to rank affection, in human psychology,
as a second type of mental element, distinct from sensa-
tion.
There are, however, many psychologists who would re-
fuse to accept these statements. Some look upon affection
as an attribute of sensation, on a level with quahty or in-
tensity ; they speak of the feeling-tone or the affective tone
of sensation, and not of a separate affective process. Others
identify affection with a certain kind of sensation ; pleas-
antness, they say, is a diffuse sensation of tickling, or a
weak sensation of lust ; unpleasantness is a low intensity of
cutaneous or organic pain. Others, again, think that the
same processes may appear sometimes as organic sensations
and sometimes as affections, according as they are isolated
in consciousness, analysed out by attention, or are given in
a mixed medley of unanalysed experience.
The first view, that affection is an attribute of sensation,
is easily disposed of. For affection has attributes of its
own, — quahty, intensity, duration ; whereas the attributes
of sensation are ultimate phases of an elementary mental
process, and cannot by any effort of abstraction be factor-
ised into simpler components. Moreover, if any single
attribute of sensation is reduced to zero, the sensation dis-
appears : a sensation that has no quality, or no intensity, or
no duration, is not a sensation at all ; it is nothing. But a
sensation may be non-affective, perfectly indifferent, and
still be far removed from disappearance. This view, then,
may be dismissed from consideration.
Nor does the second view seem to be more tenable. All
these sensations, tickling and lust and pain, may become
clear, may be made the object of attention; Indeed, they
238 Affection
are, so to say, naturally clear, precisely the sort of sensa
tions that we are obliged to attend to. But we cannot at-
tend to affection. Again, all three sensations have their
own quality as sensations. We have not fully described
tickling or lust when we have dubbed it pleasant ; we have
not fully described pain when we have dubbed it unpleasant.
Tickling has a ticklish quality, that is peculiar to it as
sensation ; lust has a specific quality, which differentiates
it from tickling ; pain has a pecuHar quality of itch or ache
or thrill. An experience which is both ticklish and pleas-
ant, or is both itchy and unpleasant, cannot be identified
with pleasantness or unpleasantness ; it is something more.
And finally, tickling and lust may, with change of cir-
cumstances, be either pleasant or unpleasant, and the same
thing holds of pain ; the scratching of an irritated area of
the skin may be at once painful and distinctly pleasant.
While, however, these arguments appear unanswerable,
it is nevertheless true that the theory which they oppose
is held by a large number of modern psychologists.
The third view tries to reconcile the belief that affection
is a second form of elementary process with the belief that
it is only a certain sort of sensation. We have, it says, vari-
ous obscure and confused experiences which, ordinarily,
we take as they come, without asking what they are made
up of. So long as we do this, the experiences present them-
selves as pleasantness or unpleasantness ; but if we scruti-
nise them, and analyse them into their elements, then they
reveal themselves as complexes of organic sensation. The
reply is, surely, that experiences which may be analysed
into organic sensations are complexes of organic sensations,
and nothing more or less ; but that, if an experience is
pleasant or unpleasant, then the pleasantness or unpleas-
§ 70- Other Views of Affection 239
antness remains, no matter how many organic sensations
are found along with it. Unless affection is organic sen-
sation, — and we have declined to admit that affection is a
sensation of any kind, — the third view is untenable.
It is impossible here to discuss or even to mention all the views
that have been held by psychologists concerning the nature of
affective experience. Affection has been described, for instance,
as a relation, whether between sensations or between a particular
sensation and all the rest of consciousness. There is some ground
for both opinions. Certain combinations of tones are pleasing,
certain others displeasing; certain architectural proportions are
beautiful, certain others are ugly. These facts tell in favour of the
first theory. Again, a sensation that now enters consciousness
enters into relation with all the contents of consciousness, and must,
so to say, make its terms with those contents. If it fits in easily
among them, it will probably be pleasant ; if it disturbs or sup-
presses them, it will probably be unpleasant. All this tells in
favour of the second theory. Nevertheless, both theories alike
are to be rejected. Against the first we must urge that affection
is not always dependent upon the relation between sensations, but
may attach to a single sensation ; and, besides, that affection, even
if dependent upon sense-relations, need not on that account be
itself a relation. Against the second we must urge, in the same
way, that the fitting-in of the new sensation, or its reverse, is purely
a matter of the behaviour of sensation ; it is not necessarily ac-
companied by affection; still less is it to be identified with
affection.
Affection has also been described in terms of mental attitude.
It has been defined as such an attitude : affective experience, we
are told, is made up of one's own attitudes, and sensory experience
of the impressions that one receives : and it has been defined as a
character of mental process that depends upon and represents
one's personal attitude. In its cruder forms, this theory implies
the existence of that permanent mind, that mind-substance or
mind-animal, which we rejected in § 3. But even at the best we
240 Affection
may well enquire whether it does not put the cart before the horse.
Does feeling represent our mental attitude, or is our mental atti-
tude the expression of feeling?
§71. The Methods of Investigating Affection. — There are
two chief difficulties in the way of an experimental treat-
ment of the affective processes. We cannot attend to
pleasantness or unpleasantness; and we can describe our
affective experience only in a roundabout way. The first
of these difficulties needs no further discussion ; we have
seen that affections lack the attribute of clearness. The
second difficulty arises from the fact that spoken language
is a language not of feeling but of idea. If I say ' I am
very angry,' you know that I am angry ; I have given you
the idea of my anger ; but I have, after all, merely indicated
my feeling, and not described it. And even if I should
attempt a detailed description, my account — so far as it
referred to the pleasantness or unpleasantness of the
anger — would still be an account at second hand ; I should
be obliged to translate my affection into an idea of affection.
There is, it is true, a language of feeling : the language of
exclamation and gesture. But we have learned, in the
course of civihsation, to repress our emotions ; we rarely
use this language ; if on occasion we wish to do so, we
are apt to make ourselves ridiculous ; and the language
itself is but little developed in comparison with speech.
Partly on account of these difficulties, and partly for
other and historical reasons, experimental psychology has,
until recently, neglected the study of affection. The prob-
lems that were at first attacked in the psychological labora-
tory were suggested by physics and physiology and
astronomy : the problems of mental measurement (§ 63), of
§ 71' T^^ Methods of Investigating Affection 241
the number and nature of the sensory quahtiesand of their
relation to the organs of sense (§ § 14 ff.). ^-^d of the duration
of mental processes. Feeling had no place in the pro-
gramme. Now, however, that psychology has gone far
enough to experiment on its own behalf, without suggestion
from its neighbours, the study of feeling has begun. There
are two experimental methods at present in use : the method
of impression and the method of expression.
(i) The method of impression has taken various forms,
the most promising of which is the method of paired com-
parisons. In this, a series of similar stimuli is laid out,
and the stimuli are presented to the observer two at a time ;
care is taken that every member of the series is paired
with every other member. We may have, for instance, a
series of squares of differently coloured paper, numbered
in order i to 50. We cut two square windows in a sheet of
neutral grey cardboard, and show the colours in these win-
dows ; the series of observations is so arranged that colour
I shall be shown along with 2, 3, 4, . . . up to 50 ; colour 2
with 3, 4, 5, ... ; and so on. In a first experiment, the
observer may be asked, as the successive pairs are exhibited :
Which of the two colours is the more pleasant.-' In the
next experiment : Which of the two is the more unpleasant ?
And the series may be repeated as often as seems necessary.
The introspective task is extremely simple : the observer
has merely to be passive, to let himself go, to allow the
stimuli to take affective possession of him. He need not
even speak ; all that he has to do is to point towards the
window which contains the more pleasant or the more un-
pleasant colour ; and the experimenter then records his
choice.
At the end of an experiment, every colour has received a
242 Affection
certain number of choices, proportional to its affective value,
a very agreeable or very disagreeable colour will have been
preferred many times over, a colour that is hardly more
than indifferent will have been chosen but rarely. If, now,
the names or numbers of the colours are arranged in order,
I to 50, along a base line, and the number of preferences
is indicated in every case by the length of a vertical line
erected upon this base, then the smooth curve which joins
the tops of the verticals may be termed the affective curve
for the particular observer ; it is a curve whose course
directly expresses his affective response to colour stimuU.
The method may be put to various uses : here is an illustration.
We have argued, in § 69, that pleasantness and unpleasantness are
opposite and incompatible. If we have recourse to the method
of paired comparisons, we can prove that they are opposite. Ex-
periments made with series of coloured papers, series of musical
tones, and series of rhythms (rates of metronome beats) give affec-
tive curves for pleasantness that are just the reverse of the same
observers' affective curves for unpleasantness : stimuli that receive
a large number of choices in the experiment on pleasantness re-
ceive a correspondingly small number in the experiment on unpleao-
antness. To prove a thing like this may look like proving the
obvious. But, in fact, nobody knew for certain, until these experi-
ments had been made, that pleasantness and unpleasantness were
opposite ; psychologists might believe, but they did not know.
And besides, things that look obvious are oftentimes, in science,
the things that very particularly call for proof.
The method may also be used to measure the individual differ-
ences in affective response to stimuH. We say that there is no
disputing about tastes ; and we tend to think, in general, that sen-
sations are experienced in the same way by all normal person?, but
that affections are experienced differently, individually, personally.
In reality, sensations are less stable and affections are more stable
than we suppose. For sensations are changed and shifted by the
§71- T]ie Methods of Investigating Affection 243
varying conditions of adaptation, contrast, attention ; while the
affective curves of a number of different observers are sufficiently
alike to show that, under the same circumstances, all normal per-
sons react affectively in very much the same way.
The method of impression can do us further service
The simple introspective task which it sets is repeated
over and over again ; the introspective experience ac
quired during a series is cumulative, all of the same kind
Hence the observer is able, in the intervals between sue
cessive series, to make a full report upon the affective con
sciousness : he can describe the course of the sense-feeling
take note of anything like a mixed feeling, state whether
the agreeableness or disagreeableness of the stimuli was
always of the same kind or showed differences of quality,
and so on. It is, indeed, to this method that we must
mainly look for a settlement of the vexed questions of
affective psychology. The work is laborious, and con-
sumes a great deal of time. But the method offers the
advantage of a twofold control : an external control by the
affective curve, the objective record of the distribution of
preferences; and an internal or subjective control by the
accompanying introspection.
(2) The method of expression seeks to record the bodily
changes which accompany the passage of an affection
through consciousness. Just as we express emotion by
smiling or frowning, by laughter or tears, by clapping the
hands or shrugging the shoulders, so do we express the
simplest affective experience by a change of various bodily
functions. Tests have been made of pulse, respiration,
the volume of a limb, involuntary movement, muscular
strength, and the response of the bodily tissues to the elec-
tric current.
244 Affection
Physiology has long been in possession of instruments that fur-
nish the records required, and psychology has borrowed these
instruments and has adapted them to its own purpose. Take
pulse, for instance. We know that the pulse can easily be felt in
the wrist, over the radial artery. Now suppose that a small tin
funnel is covered, at the wide end, by thin rubber sheeting ; and
that the sheeting is laid over the artery, and the funnel tied to the
wrist. At every beat of the pulse, the rubber will be lifted, and a
puff of air will be sent out from the small end of the funnel. Con-
nect this end, by a piece of stiff-walled rubber tubing, to the small
end of another funnel, whose wide end is similarly covered with
rubber sheeting. Hinge to the lip of the second funnel a light
splinter of bamboo ; let the splinter lie across the rubber sheeting.
Fig. 29. Marey tambour (rubber-faced funnel) with writing lever, rubber tub-
ing, and air-cock. The tubing is continued from the air-cock to the tambour on
the wrist.
and let it rest in the middle on a tiny disc of cork cemented to
the rubber. Whenever a puff of air is sent from the first funnel,
by the pulse beat, the cork disc of the second funnel will be lifted,
and the splinter will rise with it. Now take a piece of glass, that
has been smoked over a gas flame, and set it up, in the vertical
position, so that the free end of the splinter rests lightly against it.
It is clear that, as the pulse rises and falls, the bamboo point will
rise and fall on the glass, and will trace a clear line in the soot.
And if the glass be drawn slowly forward at a constant rate, a
pulse-curve will be traced which shows the rate and the heiglit of
the successive beats. Then the glass may be sprayed with varnish,
and we have a permanent pulse record.
This is a rough indication of what is called the graphic method.
In practice, the instruments are much more complicated and in-
§71. TJie Methods of Investigatiiig Affection 245
genious. The bodily change may be
transmitted to the bamboo stylus not
by air but by a system of rigid levers,
or by the electric current. And in
place of the glass plate we use a kymo-
graph, a brass drum covered with
smoked paper, which may be revolved
at varying rates. To ensure accuracy
in the interpretation of the curve, time-
markers are employed, which trace a
time curve (in seconds, or half sec-
onds, or fifths of a second, or even in
much smaller units) below the curve of
pulse or breathing. In principle, how-
ever, the tin funnels and the smoked
glass plate represent the method.
The instrument which registers the
height and rate of pulse is termed the
sphygmograph. Similar instruments,
tied round the chest or abdomen,
register the course of thoracic and abdominal breathing : they are
called pneumographs. Volume is registered by the plethysmo-
graph, a large glass jar, partly filled with warm water, in which
the hand and forearm of the subject are placed. A glass tubule
leads off from the jar,
by way of rubber tubing,
to the recording funnel
or tambour ; as the arm
swells, the water in the
jar rises, the air above
it is compressed, and
the stylus is thrown up.
Involuntary movement
is registered by the auto-
matograph, a form of
FIG. 31. Franck's Volumetric Sphygmograph ^^^ planchette or ouija-
(mechanical transmission by means of a sys- ^ •'
tern of levers). board which still figures
Fig. 30. Clockwork Kymo-
graph.
246
Affection
Fig. 32. Pneumograph.
largely in spiritistic seances. A board is slung from the ceiling, so
that it lies horizontally just over the surface of a table ; a pointed
glass rod stands vertically in a hole
pierced at its forward end. On the
table, under the point of the rod, is
spread a sheet of smoked paper. If
the arm is laid carefully on the board,
and left to itself, the glass point traces
on the paper the record of its involun-
tary movements. Muscular strength is
registered by the dynamograph or ergo-
graph : in the former, the hand grips a
steel spring, the compression of which
sends a puff of air through the trans-
mitting system to the stylus ; in the latter, the finger pulls re-
peatedly against a weight or a spring, and the cord upon which
it pulls carries a stylus which writes directly upon the kymographic
surface. Lastly, in order to measure what has been termed the
psychogalvanic reflex, two electrodes, which are connected with a
battery giving a constant current and with a
sensitive galvanometer, are apphed to the hands
or to other cutaneous surfaces ; an affective
stimulus is then presented to the subject, and
the resulting deflection of the needle of the
galvanometer is recorded.
In every case, the procedure of the experi-
ments is the same. First of all, a normal
reading is taken from the instruments : the
experimenter assures himself that the subject
is in an indifferent frame of mind, and without
applying any stimulus takes a curve of pulse,
breathing, or volume ; or allows the stylus of
the automatograph to record the involuntary
tremor of the arm ; or obtains an ergographic
record ; or notes the constant position of the
galvanometer needle. Then he applies some agreeable or dis-
agreeable stimulus, and the record is made while the sense-feehng
Fig. 33. Franck's
Plethysniograph.
§71. The Methods of Investigating- Affection 247
is running its course. The experiments are repeated again and
again ; and finally the experimenter tries to discover, from his
tracings and notes, the
exact correlation be-
tween affective quality
and the bodily change
which expresses it.
The method of
expression was
introduced into ex-
perimental psy-
chology with great
expectations ; and
the results of the
first experiments
seemed clear and
definite. All the
bodily functions were heightened and strengthened in pleas-
ure, and all were weakened and depressed in unpleas-
FlG. 34. Automatograph.
Fig. 35. Mosso's Ergograph.
ant states of mind. A leading psychologist compared
the method to * an extraordinarily delicate chemical rea-
248
Affection
gent' for the detection of pleasantness and unpleasantness.
Very soon, however, these dreams were dispelled. The
Fig. 36. Part of a tracing obtained with the Franck plethysmograph, one-
third actual size. The small waves indicate pulse, the large waves breathing.
Change of volume is indicated by tiie varying height, above the time-line, of the
entire tracing. An unpleasant stimulus was applied at the moment marked by the
left-hand cross, and removed at that marked by the right-hand cross. The unit of
the time-line is i sec,
changes in the curves are not correlated, unambiguously,
with changes of affective experience : they depend in part
upon purely physiological factors, and in part upon other
psychological processes, — for instance, upon attention.
Fig. 37. Von Frey's Sphygmograph. The entire apparatus is bcund upon the
wrist, the button at the extreme right resting on the artery. The movements of the
writing-lever are recorded on a very small, light drum, driven by a clockwork which
is housed in the square box to the left. The clockwork also actuates a time-
marker, shown in the Fig. at the lower edge of the drum.
Indeed, the simple application of even a weak stimulus
appears to throw the whole body, as it were, into reverbera-
tion ; you cannot show the observer a wall-paper pattern
without by that very fact disturbing his respiration and
§ 7i« The MetJiods of Investigating Affection 24^
circulation. If the autoraatograph proves that the organ>
ism involuntarily expands, reaches out, in pleasure, and
involuntarily withdraws, shrinks back, from the disagree-
able, it proves also that you reach out when you think of
a house across the street, and shrink back when you think
of the person behind you. There may be a general rule
that pleasantness goes with quick and shallow breathing
and slowed pulse, unpleasantness with slow and deep
breathing and quickened pulse; such an antagonism would
well express the opposition of the affective qualities. But
there can be no doubt that these changes in pulse and
respiration may be otherwise occasioned, and that the
appearance of the affective correlation depends upon con-
ditions that are, as yet, only imperfectly understood. Pulse,
for instance, has been found to quicken when the stimulus
is a pleasant taste, and to slow when it is a pleasant tone
or colour ; and breathing appears to vary in its behaviour
with different individuals.
So far, therefore, we have gained little from the method
except a number of divergent results, and the conviction
that, before these results can be psychologically inter-
preted, we must know a great deal more than we d(> of
the bodily functions involved.
It has recently been suggested that the methods of impression
and expression might profitably be combined, the registration of
physical expression serving as an objective check upon the observ-
er's introspective report, and the introspection in its turn being
used for the interpretation of the objective record. It is, of course,
feasible to register the course of pulse or breathing during an
entire series of experiments by the method of paired comparisons.
But the registration would hardly be worth while, unless the intro-
spective task set to the observer were greatly complicated ; and
then we should lose one of the chief advantages of the method.
250
Affection
It therefore seems best to continue work by the method in its
present form, and to wait patiently for the time when increased
knowledge shall give us the required understanding of the physi-
ological processes.
It may be added that the psychogalvanic method, though in
prmciple it dates from 1888, has only within a year or two been
brought into the psychological laboratory. Hence we can hardly
judge of its merit or promise as a means of affective investigation,
though the indications are that it will offer the same difficulties as
the other forms of the expressive method.
§ 72. The Tridimensional Theory of Feeling. — In 1896,
Wundt propounded a theory of feeling that differs radi-
cally from the view
taken in this book.
Pleasantness and un-
pleasantness, he de-
clared, are not simple
affective qualities, but
general names for a
very large number of
different qualities. And
even so, the terms pleas-
ant and unpleasant are
not adequate as intro
spective descriptions of
our affective experi-
ence. That experience
is, so to say, tridimen-
sional. F'eeling moves,
first, between the oppo-
FlG. 38. Diagram representing the course of a
typical sense-feeling, according to Wundt's
theory. The feeling sets in as a mixture of
excitement and unpleasantness, to which ten-
sion is soon added. It then drops into the
region of pleasantness and calm, takes on a
tinge of relaxation, and so ends at the indif-
ference-point from which it started.
site poles of pleasantness and unpleasantness ; secondly,
between excitement and depression ; and thirdly, bet\\ een
§ 72. The Tridimensional Theory of Feeling 251
tension and relaxation. Excitement and depression, ten-
sion and relaxation are, again, general names for a very
large number of ultimately different affections. Indeed,
the full list of affective qualities, distinguishable under
the six headings, is far longer than the total list of
sensations.
This theory has found many adherents, and has natu-
rally also aroused a great deal of controversy. It must
evidently be met, if our own two-quality view is to be
maintained. Let us see, then, what is to be said for and
against it.
The first thing to ask about a scientific theory is whether
it is logically constructed. Wundt assumes three catego-
ries or dimensions of feeling. Pleasantness and unpleas-
antness depend, he says, upon the intensity of the stimuli
that affect us : a moderate amount of stimulation is pleas-
ant, while too much or too little is unpleasant. Excite-
ment and depression depend, similarly, upon the quality
of stimulus. Finally, tension and relaxation depend upon
time, upon the temporal aspects of stimulus; as we wait
and expect, we become tense, and when the event happens,
we relax. In other words, our sensory experience varies
in degree, varies in kind, and varies in time : and every
such variation corresponds to a distinct category of affec-
tion. But now the critical question arises : Does not our
sensory experience also vary in space.'' Do not spatial
perceptions and spatial ideas bulk as large in conscious-
ness as intensive or qualitative or spatial.-' Is not the
world of space as native and as important to us as the
world of time.'' And if this is the case, as it undoubtedly
is, then Wundt's theory is illogical. There should be four
affective dimensions, t^ot three; and the fourth sort of
252 Affection
feelings should depend upon the spatial aspects of stimu-
lus. The objection is, indeed, more than logical; it is also
psychological; for a view of feeling which ignores the
part played by space in our mental life must be psycho-
logically inadequate.
Now consider a second point. Pleasantness and un-
pleasantness are opposite, in name and in nature. But
relaxation is hardly, in the same way, the opposite of
tension ; relaxation is rather the minimum, the zero point,
of tension. And what is the opposite of excitement.^
Sometimes Wundt says depression; sometimes calm;
sometimes arrest. But these three feehngs are surely
different: to feel depressed is not the same thing as to
feel calmed down, and to feel calmed down is not the
same thing as to feel checked or baffled. Logically, the
pairs excitement-depression and tension-relaxation are not
of the same order as the pair pleasantness-unpleasantness.
And again the objection is more than logical; for the
direct opposition that is felt in pleasantness-unpleasant-
ness cannot be felt in the other two cases.
It appears, then, that the new theory is not logically
constructed. More than that, its logical weaknesses point,
pretty clearly, to psychological defects. Psychology, how-
ever, may now speak for itself: and the first thing it has
to say is this, — ^that excitement and depression, tension
and relaxation, are never simple, elementary processes ;
they are, on the contrary, experiences of some complexity;
and they invariably contain organic (especially kinaesthetic)
sensations. On the sensory side, they represent — to put it
roughly — different muscular attitudes ; on the affective
side, they may be either pleasant or unpleasant. Pleas-
urable excitement may be the opposite of depressed mel-
§ "Jl. The Tridimensional Theory of Feeling 253
ancholy, or as eager expectancy the opposite of baffled
failure ; anxious excitement is the opposite of soothing
calm. Similarly, a disagreeable tension is the opposite of
a pleasant relaxation, but an alert preparedness is the
opposite of a despondent unreadiness. The sensory dif-
ferences may, by the concurrence of pleasantness-un-
pleasantness, be turned into affective oppositions ; without
pleasantness-unpleasantness there is no opposition. It is
noteworthy that Wundt, in his works upon psychology,
strangely neglects the organic sensations : in the present
instance, the neglect has led him to transform into simple
affections what are, evidently, complexes of organic sen-
sations.
In the last resort, the theory must be put to the test
of experiment. Wundt himself appeals to the results of
both experimental methods. The method of expression
has, we must admit, appeared in a few cases to confirm the
theory. Thus, an investigation published in 1907 states
the correlation found between the Wandtian categories,
on the one hand, and the changes in pulse and breathing,
on the other, in the following table :
slowed
strengthened weakened
Pleasantness Tension Calm
.1 i I
quickened slowed
weakened
Pulse
strengthened
1
Excitement
I
quickened
I
Breathing
quickened
Relaxation
strengthened
1
weakened
I
Unpleasantness
I
slowed
All that can be said is that results of this neat and clean-
cut character are flatly negatived by those of other, equally
careful experimenters. '\^^e saw in § 71 that the pulse
254
Affection
has often been found to slow (though not to slow and
strengthen) in pleasantness, but that this change varies
with the sense-organ to which the stimulus is applied.
We saw, too, that respiration often grows quick and shal-
low in pleasantness, but that its changes vary with the
individual ; it may, for instance, grow quick and deep, and
it may grow slow and shallow ! It is, plainly, too early to
draw any positive inference from the results of the method
of expression.
If we turn to the method of impression, we find results
that tell very strongly
against the theory.
The stimuli — colours
or tones or rhythms
— are presented in
pairs, in the usual
way, and the observ-
ers are asked to say,
in successive series,
which of the two is
the more pleasant or
unpleasant, the more
exciting or depress-
ing, the more strain-
ing or relaxing. Now,
in the first place, the
affective curves for
excitement, depres-
sion, tension and re-
laxation are always
identical with the curve of pleasantness or unpleasant-
ness ; there is no special curve, no novel distribution
44 60 60 76 92 108 120 132-144 152 160 176 192 20
Fig. 39. Curves of tension ( T) and of unpleas-
antness (U), showing that the distribution of
judgments under the two headings is practically
identical. The stimuli were metronome-beats,
given at the rates marked along the horizontal
line : 44, 50, ... in the i min. The figures on
the vertical line denote the number of choices.
It will be seen that the least straining were also
the least unpleasant stimuli (76, 92), while the
most straining were also the most unpleasant
(176, 192, 208).
§ 72. TJie Tridimensional Theory of Feeling 255
of preferences, corresponding to excitement, etc. More-
over, the different observers put different interpretations
upon these terms : if excitement is taken to mean anx-
ious, nervous excitement, its curve agrees with that of
unpleasantness ; if it is taken to mean eager, expectant
excitement, its curve agrees with that of pleasantness.
Similarly, if relaxation is taken to mean comfortable rest-
fulness, its curve is that of pleasantness ; if it is taken
to mean a despondent giving-up, the curve is that of
unpleasantness. Objectively, then, in the course of the
curves, there is no evidence of new affective dimensions.
And secondly, the introspective report of the observers
bears out the objective testimony of the curves; excitement
and depression, tension and relaxation are always described
as complexes of affection (pleasantness-unpleasantness)
and organic sensation. What Wundt has to appeal to is
nothing more than casual observation of his own ; system-
atic work by the method of paired comparisons has brought
no support to his theory. —
So far, we have simply discussed the three main cat-
egories or dimensions of feeling. Wundt, it will be
remembered, believes that each one of these dimensions
comprises a very large number of ultimate affective qual-
ities. We need concern ourselves only with pleasantness
and unpleasantness: but we have still to ask whether there
is just one sort of pleasantness and one of unpleasantness,
or whether there are varieties of agreeableness under the
common name of pleasantness, and varieties of disagree-
ableness under the common name of unpleasantness.
To this question no final answer can be given. The
experimental evidence is both scanty and conflicting. A
distinction has been drawn, for instance, between the local-
256 Affection
ised pleasantness of a taste, while the sweet substance is
in the mouth, and the diffused pleasantness which remains
after it has been swallowed. But in the former case con-
sciousness as a whole is narrowed down to a taste-in-the-
mouth (§ 69); and the pleasantness is diffused over that
narrow consciousness just as, a moment later, it is diffused
over a wider consciousness. Moreover, if the observer
is told that he may keep the sweet substance in the mouth,
as a matter of convenience, but that he is to observe his
feeling as soon as he has tasted, — that he is not to hold his
attention continuously upon the course of the sensation of
taste, — then he reports that the pleasantness is not local-
ised, but spread broadly over everything. And in any
case a localised pleasantness need not differ in kind, in
quality, from a diffused pleasantness : that difference has
still to be proved. The writer has never found, in his own
experience, the qualitative differences that Wundt assumes.
Wundt has on more than one occasion called attention, on
behalf of his theory, to the feeling of the chord c-e-g. Tones, he
says, usually bring out affective processes of the two dimensions
pleasantness-unpleasantness and excitement-depression. Each
one of the three tones c, e, g will therefore give rise to what we
may call a quiet cheerfulness of a specific kind : there will be six
affections for the three sensations. But, further, a simple affective
quality may accompany a complex of sensations : so that we have
three more affections for the complexes c-e, e-g, c-g, and yet another
— probably the dominant — affection for the whole chord c-e-g.
In sum, our affective experience of the chord is the resultant of
no less than ten affective qualities. In the writer's introspection
there is no evidence of this compounding; the sense-feeling
entirely lacks the depth, the richness, the solidity that on the
theory it ought to possess ; the affective character of the chord
seems to be adequately described in the terms * slightly pleasant,'
'moderately agreeable.' —
In spite of all that can be urged against this and similar theories
§ TZ- TJie Dependence of Affection npon Stimulus 257
of a plurality of affective qualities, the alternative position may
still seem barren and repellent. We have been so carefully
taught to distinguish the higher from the lower pleasures that
the denial of any differences of kind, within pleasantness and
within unpleasantness, may come with something of a shock. Is
it really true that the pleasure of a good dinner is identical with
the pleasure of a good action ?
Well ! remember always that affective psychology is in the trial
stage, and that no one can dogmatise on the question. But in
the writer's belief it is true. A good dinner and a good action
seem to him to differ — not in their pleasantness : that is precisely
where they are ahke ; but — in practically everything else. The
good dinner and the good action have been set apart, in popular
psychology, by reference to their one point of resemblance. And
if this sounds paradoxical, remember again that popular psy-
chology does not analyse. For it, the good dinner and the good
action are both matters of feeling, of enjoyment or satisfaction :
if, then, tiiey differ, they must differ as feelings : and if they differ
as feelings, they must differ as the lower pleasure differs from the
higher. The conclusion follows only if you accept an uncritical
use of the term feeling, and shirk the task of psychological analysis.
§ 73. The Dependence of Affection upon Stimulus. — When
we were discussing the different kinds of sensation, we
sought in every instance to connect the mental with the
physical, to refer a certain attribute of sensation to a cer-
tain phase or aspect of stimulus. We found, for example,
in § 15, that in general the wave-length, wave-amplitude
and wave-form of light correspond to the three qualitative
attributes of visual sensation, — hue, tint and chroma ;
although, in detail, the relation between visual stimulus
and visual sensation is very far from simple. We have
now to attack the same problem in regard to affection.
How are pleasantness and unpleasantness related to the
various aspects of stimulus ?
258 Affection
The question has been much debated, and the answei
is exceedingly difficult. If we could not discover a simple,
one-to-one correlation in the case of sensation, we can hardly
expect to discover it in the case of affection. For we
have taken the position — not, it is true, as demonstrated
beyond the reach of doubt, but at any rate as the most
tenable in the present state of psychology — that there are
but two qualities of affection, and that these are incompati-
ble in consciousness. Hence the affection of any given
moment is, so to say, the algebraical sum of the affections
attaching to all the various sensory processes that consti-
tute our mind at that moment. Or rather, since conscious-
ness is not a mosaic but a system,^ the affection of any
given moment depends upon the interplay or concurrence
of sensory processes that are combined in a certain conscious
pattern ; affection depends, primarily, upon the total dis-
position or arrangement of consciousness.
Might we not, however, secure an indifferent frame of
mind in our observer, and then subject him to stimuli of
different qualities, of different durations, of different degrees
of intensity, — and note how he is affected by them .-' Truly,
if the indifferent frame of mind would remain indifferent.
But the action of the stimulus may be sufficient to shake
consciousness out of its indifference, and to set up a wholly
new, and perhaps highly affective, conscious pattern: pre-
cisely as the very slightest touch upon the kaleidoscope
will throw the bits of coloured glass into a new arrange-
ment. We have seen (§ 60) that even a weak stimulus
arouses a general bodily reverberation ; and in the same
way a single incoming stimulus may touch off a complete
consciousness, so that its own special affective value is
^ Cf. the discus, n of the taste-blends, p. 134 above.
§ 73- The Dependence of Affection upon Stimulus 259
masked and obscured by the affective resultant of the
system.
Nevertheless, so much seems clear : that affection
depends less upon the several and separate attributes of
stimulus than upon their combination. We noted in § 12
the existence of sensory attributes of the second order ;
and we gave as illustration the aggressiveness or insist-
ence or importunity of sensation that results fr-^m the
connection of clearness with intensity, or clearness with
quality, or what not. It is this secondary attribute L-f
aggressiveness that appears to determine the arousal of
affection ; and the higher degrees of it appear to arouse
unpleasantness, the lower degrees pleasantness. We can
hardly with confidence say more ; and in saying this we
must remember that affection is extremely liable to adap-
tation, so that the insistence of a particular stimulus may
quickly disappear.
Wundt connects the dimension of pleasantness-unpleasantness
with the intensity of our experience (§ 72) ; and it must be
admitted that intensity is one of the commonest and one of the
most dominant factors in what we have termed insistence. But
there are qualities that are similarly aggressive : bitter, for instance,
or tickling. It is hardly possible to make a strict comparison be-
tween the intensities of different qualities ; but it will probably be
agreed that bitter is unpleasant at an intensity at which sweet is
still indifferent, and tickling unpleasant at an intensity at which
pressure is indifferent. And in general, sensations of taste and
smell seem to be more insistent, and are certainly more affective,
than sensations of sight and hearing.
There is some little evidence that affection, on its intensive
side, obeys Weber's Law (§ 66). While the lower degrees of
insistence are pleasant, and the higher degrees unpleasant, a
progressive increase of insistence within either region of the scale
will give us, of course, an increasing pleasantness or an increasing
26o Affection
unpleasantness. Now we have seen that intensity of stimulus is
oftentimes the dominant factor in insistence. Where this is the
case, it seems probable that, if the intensity of affection is to pro-
gress by equal steps or intervals, then the intensity of stimulus
must increase by relatively equal amounts. At any rate, it is true
as a general rule that what gives us pleasure or displeasure is
roughly proportional to our income, our age and status, our ambi-
tion, our standard of comfort. If I am starting a library with a
hundred volumes, and a single book is given me, I am as pleased
— other things being equal — as I should be by the addition of
ten volumes to a library of a thousand. The stamp which com-
pletes the set in the schoolboy's album gives him as much pleasure
as the acquisition of the last farm which completes the ring-fence
gives the wealthy landed proprietor. All these things sadly need
experimental confirmation ; but there seems no reason why affec-
tive intensity should not, and there seems to be some evidence
that in fact it does, follow the same law as the intensity of sensation.
§ 74. The Bodily Conditions of Affection. — If we know
but little of the affective processes themselves, we know
still less about their bodily conditions. The suggestions
that follow are, therefore, entirely hypothetical.
It is natural to suppose that the material of conscious-
ness, the stuff out of which mind is made, was originally
homogeneous, all of a piece : so that sensations and affec-
tions are simply different species of the same genus. We
have seen, indeed, that there is positive evidence for this
view ; there are fundamental resemblances between the
two elementary processes, which point to their derivation
from a common mental ancestor. If, then, we adopt it as
a working hypothesis, the affections appear — not exactly
as undeveloped sensations, for an undeveloped sensation is
still a sensation — but at any rate as mental processes of
the same general kind as sensations, and as mental pro-
§ 74- ^-^^^ Bodily Conditions of Affection 261
cesses that might, in more favourable circumstances, have
developed into sensations. The writer liazards the guess
that the peripheral organs of affection are the free afferent
nerve-endings — what are ordinarily called the free sen-
sory nerve-endings — distributed through the various tis-
sues of the body ; and he takes these free endings to
represent a lower level of organic development than the
specialised receptive organs, or organs of sense. Had
mental development been carried further, pleasantness
and unpleasantness might have become sensations : in all
likelihood would have been differentiated, each of them,
into a number of sensory qualities. Had our physical
evolution been carried further, we might have had a cor-
responding increase in the number of internal sense-organs.
It was said in § 42 that the free nerve-endings of the epidermis
are probably to be regarded as the terminal organs of pain. If
this hypothesis is correct, we might perhaps assume, as some
psychologists do, that there is a close genetic kinship between the
sensation of pain and unpleasurable affection. Pain would then
appear as a specialised sensory derivative from unpleasantness,
and would still retain an end-organ of the affective type.
On the other hand, we have to remember that the cutaneous
pain-sense has three qualities, itch, prick, and pain proper, and
that these qualities are by no means necessarily unpleasant. In-
tensive pains are unpleasant ; but so are bitter tastes, and so are
rank and foul and nauseous odours. Besides, we know very little
about the cutaneous sense-organs, aside from pressure, and we
know nothing at all of the organs of the dull, deep-seated pain
that seems to be different from the bright and thriUing pain at the
surface of the body (§§ 41, 56). The pains proceeding from
muscular tissue and from the peritoneum probably have special-
ised organs. On the whole, therefore, it is best to leave pain out
of account. If the free endings of the epidermis are not organs
of pain, the physiological evidence for the connection of pain with
262 Affection
unpleasantness falls to the ground. If they are, it is still possible
that their exposed position and consequent liability to injury allovf
them to function as sense-organs, while they are replaced in the
interior of the body by more highly specialised structures ; or it is
possible that they have become adapted, in some unknown way,
to the reception of sensory stimuli. No opinion can be more
than a conjecture.
This theory of the bodily conditions of affection ex-
plains, first, the lack of the attribute of clearness. Affec-
tive processes are processes whose development has been
arrested; they have not attained, and now they never
can attain, to clear consciousness. Affective experience
is the obscure, indiscriminable correlate of a medley of
widely diffused nervous excitations. The theory explains,
secondly, the movement of affective processes between
opposites ; for the nervous excitations will vary with the
tone of the bodily systems in which they are set up, and
that tone can itself vary only in two opposite ways. It
explains, thirdly, the introspective resemblance of affection
to certain organic sensations ; genetically, the two sets of
processes are near akin, and it is natural that they should
be alike in experience. And it explains, fourthly, the
apathy or lack of feeling that comes with visceral anaes-
thesia (§ 56); for if the specialised nerve-terminals, the
sense-organs of the viscera are paralysed, it is to be ex-
pected that the unspecialised free endings, occurring in
the same tissues, should share their fate. Finally, the
theory is non-committal on the questions of mixed feeling
and of a differentiation of qualities within pleasantness-
unpleasantness. It thus serves well enough for the pres-
ent state of our psychological knowledge. It is, neverthe-
less, simply a guess.
References for Further Reading 263
Many other guesses have been made with regard to the bodily
conditions of affection, both peripheral and central. Under the
latter heading it has been conjectured, for instance, that the
affections are indices of the state of nutrition of the cerebral
cortex ; that they are symptoms of the readiness of motor dis-
charge ; and that they are connected with the activity of a special
cortical centre. Each one of these hypotheses has a certain
plausibility, but none is within measurable distance of proof. —
When physiology leaves us in this perplexity, it is but natural
that we should make appeal to the wider science of biology. Can
biology help us to a psychology of feeling? Well ! a great deal
has been written about the biological significance of pleasantness
and unpleasantness. The pleasurable, we are told, corresponds to
the useful, and the disagreeable to the harmful ; pleasant ex-
periences are good and unpleasant experiences are bad for the
organism. And this means that pleasantness is felt when the
activity of a bodily organ is in balance, outgo of energy equalling
intake of nourishment; and that unpleasantness is felt when the
organ is out of balance, either overworked or overnourished.
But, first, the general law of correlation, pleasant-useful and un-
pleasant-harmful, cannot be made out : there are gross and obvi-
ous exceptions. Moreover, if it could be made out, it would
not aid our psychology ; for useful and harmful mean nothing until
they are translated into psychological and physiological terms ;
and as soon as the translation has been made, we can dispense
with biology altogether. Secondly, the theories of organic balance
are as conjectural as the rest, and are very difficult to apply in
detail. It is hardly worth while, therefore, to devote further
space to biological considerations.
References for Further Reading
§§ 68-74. Wundt's tridimensional theory is set forth in his Outlines
of Psychology, igoy • or, at greater length, in the G^'iindziige der physi-
ologischen Psychologies ii., 1902, 263. For a theory which identifies affec-
tion with sensation, see C. Stumpf, Ueber Gefuhlsenipfindungen^ in the
Zeitschrift f. Psychologic, xliv., 1906, i. A critique of these theories,
and a discussion of the differences between sensation and affection, wiU
264 Affection
be found in the author's Lectures on the Elementary Psychology of FeeU
ing and Attention^ 1908, Lectures II.-IV.
For the method of impression, see S. P. Hayes, A Study of the Affec-
tive Qualities, in American fournal of Psychology, xvii., 1906, 358. For
the method of expression, see J. R. Angell and H. B. Thompson, A
Study of the Relations between Certain Orgatiic Processes and Con-
sciousness, in Psychological Review, vi., 1899, 32; P. ZonefF and E.
iVIeumann, Ueber Begleiterscheinungeft psychischer Vorgange in Athetn
und Puis, in Wundt's Philosophische Studien, xviii., 1903, i ; M. Kelch-
ner. Die Abhdngigkeit der Atein- und Pulsveranderung vom Reiz und
vom Gefilhl, in Archiv f d. gesainte Psychologic, v., 1905, i ; N. Alech-
sieff, Die Grundformen der Gefiihle, in Wundt's Psychologische Studien,
iii., 1907. 156; P. Salow, Z'^r Gefuhlscharakter einiger rhyth7nischer
ScJiallfornien in seiner respiratorischen Aeusserung, ibid., iv., 1908.
iff.; F. Peterson and C. G. Jung, Psycho-Physical hivestigations with
the Gahinuoiiieter and Piieuniograph in Normal and Insane Individ-
uals, in Brain, xxx., 1907, 153.
On the biological significance of feeling, see H. Spencer, Principles
of Psychology, i., 1881, pt. ii., ch. ix. ; H. Ebbinghaus, Grundzi'ige der
Psychologic, i., 1905, 568 ; D. C. Nadejde, Die biologische Theorie der
Ltist und Unlust, i., 1908. A genetic theory of feeling, in some
respects akin to that of the text, but differing from it on important
points, is worked out by J. M. Baldwin, Mental Development in the
Child and the Race: Methods and Processes, 1895, 481 ff. ; 1906, 457 ff.
ATTENTION
§75. The Attentive Consciousness. — The word 'atten-
tion/ like the word ' feehng,' has been employed in the
history of psychology to denote very different things.
Attention has been regarded, at various times, as a peculiar
power or capacity, the faculty of concentration, the ability
to restrict at will the field of consciousness : as a peculiar
form of mental activity, an effort that one puts forth or an
initiative that one takes, radically different from the passiv'
ity with which impressions are received : as a state of the
whole consciousness, a state of clear apprehension and of
effective thought : as a feeling or emotion : and, finally, as
a complex of sensations, and more especially of kinaes-
thetic sensations.
It is plain that not all these views can be correct, though
every one of them can find a certain support in the facts
of observation. When I am so deeply sunk in a scientific
problem that I forget my headache, or fail to hear the
dinner bell, I seem, pretty clearly, to be exercising the
power of concentration. When I force myself to go to
work, in face of the temptation to finish an interesting
novel, I seem to be exerting a spontaneous activity, to be
myself determining my world rather than determined by
it. When, again, I wish thoroughly to understand a
thing, to make myself master of it, I give it my full atten-
tion : attention is, then, that state of consciousness, that
degree of being conscious, which guarantees the best
2fT,
266 Atientiou
results of mental labour. When I am keenly attending,
I am also keenly interested; and interest is a mode of
affective experience. Lastly, when I am trying to attend,
I invariably find myself frowning, wrinkling my forehead,
holding the breath, setting the body in some definite and
rigid attitude. All such sets and movements give rise to
characteristic complexes of cutaneous and kinaesthetic
sensations. Why should not these sensations represent,
in psychology, what we popularly call attention .■'
The appeal lies to experimental introspection : and our
rule must be here as it has been elsewhere, that if the
experimental results come into conflict with our precon-
ceived opinions, the opinions are to be igiven up. But
before we enter upon the experimental study of attention,
let us try a bit of straightforward analysis ; let us look at
a typical attentive consciousness, and see whether our
schooling in psychological method helps us to dissect it.
The most promising case will be a case of suddenly
aroused attention. Suppose, then, that I am working or
reading quietly, and that a telephone message or the
entrance of a visitor suddenly demands my attention.
The first thing that happens is that there is a redistribu-
tion of the entire contents of consciousness. The incom-
ing ideas — my friend's business or the subject of the
message — drive to the centre, and everything else, my
previous occupation as well as my sensory surroundings,
are banished to the outskirts. Consciousness, in attention,
is patterned or arranged into focus and margin, foreground
and background, centre and periphery. And the differ-
ence between the processes at the focus and the processes
in the margin is, essentially, a difference of clearness : the
central area of consciousness hes clear, the more remote
§ 75- 1^^^^ Attentive Consciousness 267
regions are obscure. In this fact we have, indeed, the
key to the whole problem of attention. In the last resort,
and in its simplest terms, attention is identical with sen-
sory clearness.
However, w^e must confine ourselves to observation, and
not anticipate. The attentive consciousness is arranged as
clear and obscure : so much is evident. Is the conscious-
ness affective.'' Not necessarily. We may greet our friend
with an absorbed interest, with pleasurable concern or with
foreboding of unpleasantness ; but we may also give him a
perfunctory and mechanical attention, which leaves us
wholly unaffected. Is the consciousness kinaesthetic .''
Again, not necessarily. There may be a wide-spread
arousal of kinaesthetic sensations, or there may be no
sensible change in the muscular system : it depends upon
circumstances. So that it appears, even to unaided intro-
spection, that the redistribution of contents into the groups
of clear and obscure is the one universal and characteristic
feature of the attentive consciousness.
It should hardly be necessary to repeat here that modern
psychology knows nothing of a permanent mind, or of faculties
or activities or manifestations of such a mind (§ 3). Whatever
attention is, it must be described in terms of mental processes,
sensations and images and affections, and explained by reference
to its physiological conditions. On the other hand, attention
offers itself as an admirable touchstone by which the views of
modern psychology may be tested. For the whole situation in
attention seems, at first sight, to imply a selective and spontaneuus
mental activity. As I lean back in my chair to think out a psy-
chological problem, I am subject to all sorts of sensory stimuh ;
the temperature of the room, the pressure of my clothes, the sight
of various pieces of furniture, sounds from house and street, scents
coming from the room itself or borne in through the open window,
268 Attention
organic excitations of different kinds. I could easily lapse into a
reminiscent mood, letting these impressions suggest to me scenes
from my past life. I could easily give the rein to my imagination,
thinking of the further business of the day, anticipating some event
that is to happen in the near or distant future. But I am, in fact,
perfectly well able to ignore all distractions, and to devote myself
entirely to a single self-chosen idea, — the idea of the problem
that awaits solution. It is true, then, that this idea is clear and
central, while all the other conscious processes of the moment are
obscure and marginal. But it seems to be true, also, that the
clearness of the idea is rather a matter of the mind's own concen-
tration than of any character of the idea itself. Besides, I can
turn my mind, if I like, to something entirely different; I can give
up the problem whenever I feel disposed.
That is the situation in attention, as popular psychology sees
it. We must take up the implied challenge, and see whether our
own methods can throw any further Hght upon the question.
§ 'j^. The Development of Attention. — Attention, as the
term is popularly understood, has two forms. It may be
passive and involuntary, or it may be active and voluntary.
These forms are, in fact, characteristic of different stages
in mental development ; they differ simply in complexity,
as earlier and later ; they show us the same type of con-
sciousness, but at different periods of our mental growth. It
will, however, clear the ground if we now enquire wherein
their difference consists, and what are the conditions ot
their occurrence.
There is, in the first place, an attention that we are
compelled to give and are powerless to prevent. Or, to
put the same thing in other words, there are impressions
that we cannot help attending to, that take consciousness
by storm. Intensive stimuli belong to this class. Loud
sounds, bright lights, strong tastes and smells, severe
§ 76. TJie Development of Attention 269
pressures, extreme temperatures, intense pains, — all these
are clear in virtue of their intensity ; they attract our
attention, as the phrase goes, in spite of ourselves ; they
force their way to the focus of consciousness, whatever the
obstacles that they have to overcome. In the same way,
there are certain qualities that irresistibly draw the atten-
tion : here belong in the writer's experience — though
there are very considerable differences between individu-
als — the taste of bitter, the smell of musk, the sight of
yellow. A stimulus that is repeated, again and again, is
likely to attract the attention, even if at first it is entirely
unremarked. Sudden stimuli, and sudden changes of stim-
ulus, have the same effect. So with movement: the ani-
mal or bird that crosses the landscape, the melody that
rises and falls to a steady, uniform accompaniment, the
insect that crawls over our hand as we lie upon the grass,
these things constrain us to attend to them. Novelty,
too, arrests the attention. The novel impression is, in
psychological terms, the impression that finds no associ-
ates when it enters consciousness; that stands alone, in
isolation. Such an impression, if it is at all intensive,
becomes clear in its own right; it is startling, just as the
sudden stimulus is surprising and the moving stimulus is
disturbing. And lastly, paradoxical as it sounds, impres-
sions that are in a sense the reverse of novel claim the
attention, — impressions that fit in with, are associated to,
the present trend of consciousness. The collector, the in-
ventor, the expert are roused to keen attention by stimuli
which the rest of the world pass without notice. Most of
the striking coincidences in life are accounted for by this
law: you are thinking about certain things, and something
happens that, because you are thus thinking and because
270 Attention
it is akin to the subject of your thought, captures your
attention. What a remarkable coincidence ! you cry : but
if you had been thinking of something else, there would
have been no coincidence. The man in Mr. Kipling's
story who wondered, years after the event, how in the
world he could have written such good stuff as that, had
written under this same law of attention; for when you
are thoroughly absorbed in a topic, relevant facts and
ideas crowd in upon consciousness; the mind stands wide
open to them, while it is fast locked against the irrelevant;
and you surpass yourself.
Here, then, is a fairly long list. Intensity, quality, repe-
tition, suddenness, movement, novelty, congruity with the
present contents of consciousness, are one and all deter-
minants of attention. When they appear, we have to
attend to them, even if we have grounds for attending
elsewhere. Attention thus determined, attention at the
first stage, is usually termed passive or involuntary atten-
tion. Unfortunately, a passive implies an active ; and
active attention is, as we shall see, a misnomer. Other
names have been suggested ; but we shall do best to
speak simply, in this connection, of primary attention.
It is worth noting that all the members of our list are of a kind
to produce a powerful effect upon the nervous system. Intensive
stimuli naturally set up intensive nervous excitations ; and inten-
sive excitations will not be easily checked or obscured by rival
excitations. The qualitative stimuli that compel attention appeal
to some peculiar susceptibility of the nervous system. Repeated
stimuli have a cumulative influence. Sudden stimuli impinge
upon nervous elements that have recently been free from stimu-
lation of their particular kind, that is, upon elements of a high
degree of excitability; and it is also probable that the excitations
which they arouse suffer less dispersion and diffusion, within the
§ ^6. The Development of Attention 271
nervous system, than those set up by the gradual application of
stimulus. Moving stimuli affect different nervous elements in
quick succession ; there is no possibility of fatigue or of sensory
adaptation ; in a way, therefore, the action of the moving stimu-
lus is cumulative. Novel stimuli, being isolated stimuli, arouse
excitations which are not interfered with by others ; their action
is akin to that of sudden stimuH. As for the effect of congruity
with consciousness, it is clear that the more nearly an incoming
excitation coincides with an excitation already in progress, the
more easily will it make its way within the nervous system, and
the more dominant will it become. The novel and the familiar
may thus have a similar excitatory value.
Primary attention, however, represents a genetic stage, the ear-
liest stage of attentional development. Hence it is not enough to
look at its determinants physiologically ; we must also view them
biologically. And if we do this, some of them at any rate take
on a new significance. Any nervous system will be powerfully
impressed by intensive stimuli ; any organism that has risen high
enough in the scale of evolution to have a consciousness made up
in part of ideas, of memories and imaginations, will be power-
fully impressed by stimuli that are congruent with those ideas : it
is precisely to such stimuli that the gates of the nervous system
lie open. But what of novelty and suddenness and movement?
These have a special biological meaning : for the new and the sud-
den and the moving are probable sources of danger, and the crea-
ture that failed to attend to them would soon have ceased to exist.
There are, however, many occasions when, so far from
the impression's drawing and riveting our attention, it
seems that we are holding our attention by main force
upon the impression. A problem in geometry does not
appeal to us as a thunder-clap does. The thunder-clap
takes unquestioned possession of consciousness. The
problem has only a divided claim upon us : there is con-
stant temptation to wander away from it and to attend to
something else. We continue attending ; but we have to
2/2 Attention
make ourselves attend. In many of the psychological
experiments that we have described, the object of atten-
tion — an obscure organic sensation, a minute qualitative
difference — is something which of itself, so far from at-
tracting notice, would seem to be eminently fitted to escape
it. Attention to such an object is usually termed active
or voluntary attention ; we shall call it secondary attention.
For it is not really active attention, if the adjective im-
plies anything like a special and spontaneous mental activ-
ity. It is simply the resultant of a conflict of primary
attentions. There are rival claimants for the chief place
in consciousness, and the standing-room is limited. So
the attention, as we say, is divided ; or perhaps it oscillates
between the various impressions presented. Secondary
attention is attention under difficulties, attention in face of
competitors, attention with distraction. But that is its
whole secret ; it has no novel feature.
Secondary attention is a necessary consequence of a complicated
nervous organisation. Let us take an imaginary case : the case
of an animal endowed with two sense-organs, an eye and an ear.
Suppose that such an animal is exposed, at the same moment, to
two different stimuli, a bright light in front of it and a loud sound
at its side. It cannot afford to neglect either. Hence it will
attend, first, to the stimulus which has the greater attractive force ;
but then, having attended to that, it will at once turn its attention
to the other : and so there will be a seesaw of light and sound at
the focus of consciousness, a quick succession of primary atten-
tions. This, as we shall see presently, is not all of the psychologi-
cal story ; but it is the essential point.
Now take a case that lies nearer home. Suppose that 3'ou are
in your room, preparing for to-morrow's examination, and that you
hear an alarm of fire in a neighbouring street. Both ideas, the
idea of examination and the idea of fire, are imperative; there is
a conflict. The cortex is set in one part for work : and this set-
§ 76- The Development of Attention 273
ting is reinforced by a large number of associated excitations, — ■
the nervous processes corresponding to ideas of tlie examination
mark, the consequences of failure, and so on. The cortex is set
in another part for going to the fire : and this setting is similarly
reinforced, by the processes corresponding to the ideas of a run
in the fresh air, an exciting scene, a possible rescue, and so on.
The struggle may last some little time, and its effects may persist
for a while after you have made your choice. So long as there is
any trace of it, your attention is secondary or ' active ' attention.
There is yet a third stage in the development of atten-
tion ; and this consists in nothing else than a relapse into
primary attention. As we work at our problem in geome-
try, we gradually become interested and absorbed ; and
presently the problem gains the same forcible hold over
us that the thunder-clap has from the moment of its ap-
pearance in consciousness. The difficulties have been
overcome ; the competitors have been vanquished ; the
distraction has disappeared. There could hardly be a
stronger proof of the growth of secondary out of primary
attention than this fact, of everyday experience, that sec-
ondary attention is continually reverting to the primary
form.
We spoke just now of making a choice between work for the
examination and going to the fire. The making of a choice means,
of course, that the stronger of the two conflicting forces, the rival
excitatory processes, has won the day; and the traces of the
struggle that persist after the choice has been made mean that
the victory has not been absolutely complete. If experiences of
the sort are often repeated, so that a habit is set up, — a habit of
work or a habit of play, — then the struggle is brief, and second-
ary attention is quickly replaced by primary.
The mention of habit leads us to a further, and a very impor-
tant point. This nervous system of ours, which is the scene of
2/4 Attention
the conflict in secondary attention, has a long evolutionary his-
tory. We are not all born equal ; we are born with nervous sys-
tems that bear upon them a certain hereditary stamp, that already
have within them lines of less and lines of greater functional re-
sistance. The poet, we say, is born and not made ; and to a
certain extent, if the phrase is permitted, we are all of u-s born
and not made. On the other hand, the child's nervous system
is exceedingly plastic and impressionable ; it is easily moulded
by education ; so that, to quote another current saying, habit
may become second nature. The leanings and aptitudes and
predilections that we show in adult life are, then, the resultant
of two influences, heredity and education, nature and nurture.
Now the important point in the present connection is this : that
the side which finally proves to be the stronger, in the struggle
of secondary attention, need not necessarily be the consciously
stronger. The conflict between working and going to the fire
may lead to a victory for work, in spite of the fact that conscious-
ness is more fully occupied by fire-ideas than it is by work-ideas.
The nervous system, in virtue of its own bias or leaning, has
brought up further reinforcements on the side of work, and these
reinforcements have directed or guided consciousness although
they are not themselves represented in consciousness.
The guiding influence of nervous bias is not a matter of infer-
ence, still less a matter of speculation ; it can be demonstrated
in the psychological laboratory. Suppose that we are measuring
the time required to reply to a spoken word by another word of
the same class or kind : to associate dog to cat, table to chair,
and so on. The experimenter prepares a long list of words : cat,
chair, and so forth. Then he explains to the observer the precise
nature of the experiment : I shall call out certain words, he says,
and you are to reply, as quickly as you can, with words of the
same class ; if I say horse, you will mention some other animal,
and if I say pen, you will mention something else that has to
do with writing. The observer understands, and the experiment
begins. Suppose, further, that the experiments have been contin-
ued for some days. The experimenter has no need to repeat his
explanation at every sitting ; the observer takes it for granted that
§ 7^. TJie Development of Attention 275
he is still to- reply with a coordinate word. And suppose, finally,
that some day, after a week's work, the experimenter interrupts
the series, and asks : Are you thinking about what I told you to
do? The observer, fearing that he has made some error, and
feeling very repentant, will say : No ! to tell the truth I had
absolutely forgotten all about it ; it had gone altogether out of
my mind; have I done anything wrong? He had not done any-
thing wrong ; but his answer shows that a certain tendency, im-
pressed upon his nervous system by the experimenter's original
explanation, has been effective to direct the course of his ideas
long after its conscious correlate has disappeared. And what
happens here, in the laboratory, happens every day of our lives
in the wider experience outside the laboratory.
In summary, then, attention appears in the human
mind at three stages of development: as primary atten-
tion, determined by various influences that are able to
produce a powerful effect upon the nervous system ; as sec-
ondary attention, during which the centre of conscious-
ness is held by a certain perception or idea, but is held
in face of opposition ; and lastly as derived primary
attention, when this perception or idea has gained an
undisputed ascendency over its rivals. The attentive con-
sciousness is at first simple; it then becomes complex, —
reaching, indeed, in cases of hesitation and deliberation,
a very high degree of complexity ; and then it simplifies
again. Looking at life in the large, we may say that the
period of training or education is a period of secondary
attention, and that the following period of achievement
and mastery is a period of derived primary attention.
Looking at experience more in detail, we see that educa-
tion itself consists, psychologically, in the alternation of
the two attentions : habit is made the basis of further
acquisition, and acquisition — gained with pains — passes
2/6 Attention
in its turn into habit ; the cycle recurs, so long as the
organism retains its nervous plasticity. Secondary atten-
tion thus appears, everywhere, as a stage of transition, of
conflict, of waste of nervous energy, though it appears at
the same time as the necessary preliminary to a stage of
real knowledge.
We may now return to our analytical study of the atten-
tive consciousness. There are three stages of attention,
but there is only one type of attentive consciousness ; the
three stages show differences of complexity, but not dif-
ferences of kind.
In the meantime, it may prevent a possible misunderstanding
if we say, explicitly, that the greater complexity of consciousness
in secondary attention does not necessarily mean a greater num-
ber of constituent mental processes. The single object of pri-
mary attention may be extremely complex ; the competing objects
of secondary attention may be relatively simple. The complexit}'^,
then, is a complexity, not necessarily of conscious contents, but
rather of conscious pattern, of the disposition of the contents.
In primary attention, consciousness flows smoothly within a
definite channel ; in secondary attention, its course is zigzag,
meandering through various channels. The number of mental
processes given in secondary attention may be, and often is,
much larger than the number given in primary attention ; but
the characteristic difference between the two consciousnesses lies
elsewhere. Consciousness in primary attention may be repre-
sented by a series of parallel straight lines, each standing for some
mental process that enjoys its full normal duration ; conscious-
ness in secondary attention must be represented by a pattern of
shorter and variously directed oblique lines, each standing for
some mental process whose progress has been arrested by the
advent of a rival.
§ yj. The Two Levels of Consciousness. — The rough
analysis of § 75 led us to conclude that the attentive
^77- '^^'-^ Tzuo Levels of Consciousness 277
consciousness is always arranged in a dual pattern of clear
and obscure, focus and margin. We might represent it
by means of two con-
centric circles, the inner
and smaller bounding
the region of clearness,
or containing what is
called the object of at-
t
F'IG. 40. Diagram of the Attentive Conscious-
ness. The stream of consciousness, outhned
by the thin Hne of the Fig., is supposed to be
moving towards you from the plane of the
paper; the thick Hnes represent the neural
channel in which the stream is flowing.
tention, and the outer
and larger bounding
the region of obscurity
or of inattention. A
more serviceable dia-
gram, however, is one that represents the stream of con-
sciousness as running at two different levels, the higher
that of the clear and the lower that of the obscure pro-
cesses in consciousness. We shall make use of this dia-
gram in what follows.
Let us begin by making an observation for ourselves.
Figure 41 is a puzzle picture; it is a drawing of the left
hemisphere of the brain, but it is something else also.
Look at it, and try to find what it conceals. While you
are searching, the whole drawing is at the upper level of
consciousness, and the rest of your experience is at the
lower level. Suddenly you find what you are looking for :
and what happens.? Why, the moment you do so, the
picture of the brain drops clean away from the upper level :
the concealed outlines stand out with all imaginable clear-
ness, and the form of the brain is no clearer than the feel
of the book in your hand. The first two-level consciousness
has been replaced by a second, and the drop of the original
object of attention from crest to base of the attention-wave
is very striking.
2/8
Attention
In one respect, this observation is not typical. When you
have solved the puzzle, you experience a keen satisfaction ; and
affective processes are not always found in the attentive conscious-
ness. In all other respects, the observation appears to the writer
to be typical. The object of attention does not glide, by slow
degrees, to the higher level, but rises at a single step \ now you
are attending to one thing, and now you find yourself attending to
another. It should be said, however, that this view is disputed.
Some psychologists believe that the attentive consciousness shows,
'-- 1 /i
Fig. 41. Drawn by R. Gudden, Frankfurt a. M.
not two different levels, but a single rising and falhng slope; they
believe, that is, that processes of all possible degrees of clear-
ness may coexist in the same consciousness. Others believe that
there are more than two levels, — three, for instance : the levels
of attention, of inattention, and of a still deeper, subconscious
obscurity. We return to the matter again on pp. 290, 302.
The main characteristic of the processes at the upper
conscious level is their high degree of clearness. We
mentioned clearness, in § 12, among the attributes of
sensation, and the term carries its meaning with it. A
§ 77. The Tzvo Levels of Consciousness 279
process is clear or vivid when it is at its best, when it is
making the most of itself in experience. Clearness is an
intensive attribute, in the sense that it shows degrees of
more and less ; but it is altogether different from intensity
proper. When, for instance, you are listening to a very
faint sound, the sensation of noise may be the clearest
thing in consciousness, although its intensity is minimal.
Indeed, there is no difficulty whatsoever, after a little prac-
tice, in distinguishing introspectively between the clearness
and the intensity of any given mental process.
It is, however, a much debated question whether clear-
ness and intensity, though distinct attributes of sensation,
are not always connected in experience. Does not a rise
in clearness mean also a rise in intensity } The very faint
sound may be clear, in spite of its weakness : but is it as
weak as it would be if it were less clear ? In popular
phrasing, does not attention intensify its object .-* We find
every possible answer to these questions. Some psycholo-
gists believe that change in clearness makes no difference
in intensity. Others beheve that it makes only an apparent
difference. Increase in clearness, they say, means a more
independent status in consciousness ; and this indepen-
dence, this freedom from interference, allows the other
attributes of sensation to come to their full conscious
lights. Intensity thus makes all the effect that it has in
it to make ; it appears to be increased, whereas in reality
it is simply getting — what without clearness it could not
get — fair play in consciousness. Others, again, think that
clearness does bring with it an increase of intensity ; and
yet others assert that it means a decrease. In the writer's
judgment, the third of these views, that intensity is raised
along with clearness, is the most probable.
28o Attention
The belief that change in clearness makes no difference in in*
tensity rests upon facts of everyday observation : your surround-
ings do not brighten up as you attend to the lamp, the clock does
not begin to tick more loudly as you listen to it. But, first, this
sort of observation is very unreliable ; if you try it for yourself,
you will find how far you are from any real comparison of the
more clear and the less clear process. And secondly there are
facts on the other side : you can hear, with attention, a faint sound
that you cannot hear if you do not attend. The next hypothesis,
that the change in intensity is only apparent, contains an element
of truth ; but in so far as it is an attempt to reconcile the first and
the third, it will not come into account until the third has been
disposed of. The issue lies, therefore, between the third and the
fourth views, that attention intensifies and that attention weakens
its object ; and the test is experiment. There is evidence on both
sides ; but it appears to the writer that the evidence for weakening
is ambiguous, and the evidence for intensification clear and deci-
sive. Suppose, for instance, that two sounds, a weaker and a
stronger, are presented to the observer in quick succession ; and
suppose that he gives full attention to the weaker, but that his
attention is diverted from the stronger by some interfering
stimulus, for instance, by a strong odour. If he judges that the
two sounds are of equal intensity, still more if he judges that the
objectively weaker sound is the more intensive of the two, we
have an increase of intensity with attention or (what is the same
thing) a decrease of intensity with distraction. And this is what
happens.
It is not at all surprising that we should find an intimate relation
between clearness and intensity; for, as we said in § 76, all the
conditions of a high degree of clearness are also conditions for
the powerful impression of the nervous system. Nor does the
connection of the two attributes affect anything that we have said
in §§ 62 ff. : for the intensities which obey Weber's Law are, of
course, intensities at maximal clearness. —
It does not seem probable that clearness brings with it any
change in extent or duration. Processes, however, that would
ordinarily be curtailed, swamped by stronger processes, may — if
§ yS. Factors in the Attentive Consciousness 281
they are clear — be followed for a longer time in their course
through consciousness, and may thus be apparently lengthened.
We may now interpret Fig. 40 to mean that the pro-
cesses at the crest of the attention-wave are both clearer
and stronger than the processes at the lower level of con-
sciousness. These are the attributes that give the object
of attention its special value for memory and imagination
and thought.
§ 78. The Kinaesthetic and the Affective Factors in the At-
tentive Consciousness. — We may assume that attention, in
its beginnings, was a definitely determined reaction of the
whole organism — sensory, affective, motor — upon a single
stimulus. The strong or sudden or novel or moving thing
was perceived, as sight or sound or touch. It was also, as
we have said (§ 76), felt as startling or disturbing or sur-
prising. The affective element in the experience ex-
pressed itself in a change of the great bodily functions.
At the same time the animal took up an attitude to the
stimulus, in the literal sense ; faced it, as peering and
listening and frightened animals face such stimuli to-day.
At this stage, then, the redistribution of the sensory pro-
cesses in consciousness, the clearing of some and the
obscuring of others, was accompanied both by affection,
and by kinaesthetic sensations due to internal bodily
changes and to muscular attitude.
Secondary attention has its origin in a conflict of pri-
mary attentions: in the rivalry of clear perceptions and in
the struggle of incompatible motor attitudes. The percep-
tions may be either pleasant or unpleasant; the motor
restlessness will be unpleasant, reflected in an affective un-
easiness. We have, now, a survival of this primitive state
282 Attention
of affairs in the effort which always comes with secondary
attention. We naturally dislike to work ; work of any sort
means effort. And effort is itself a sense-feeling, made up
of unpleasantness, and of a complex of kinaesthetic and
organic sensations. Experiments by the method of ex-
pression show that breathing in secondary attention is
likely to be inhibited, to become shallow; and there are
other bodily changes, correlated in part with the unpleas-
ant affection, in part with the motor restlessness.
As the nervous system developed, image supervened
upon sensation, and conflict and rivalry were largely trans-
ferred to the field of ideas. Congruity with consciousness
now took its place among the determinants of primary at-
tention. There was a radical change in the make-up of
consciousness ; and one aspect of the change was the
weakening of the kinaesthetic and affective factors in at-
tention. The effort that we make when we sit down to
work, and the difficulty that we feel for the first few
minutes of working, are the direct descendants of the older
uneasiness and the older motor restlessness, but they are
degenerate descendants, mere echoes of the primitive ex-
periences. So degenerate are they, that some psychologists
refuse to regard effort as a sense-feeling: VVundt makes
tension a simple affection, and others see in it a new kind
of mental element, a conative element or elementary
process of will. There is no introspective warrant for
either view. Effort, in whatever context we take it,
proves to be analy sable ; it reduces to affection and
sensation.
The last stage in this development is given with the
passage from secondary to derived primary attention. We
began with an affective sensorimotor reaction, the reaction
§ 78. Factors in the Attentive Consciousness 283
of the whole organism upon a single stimukis. From that
we passed to sensorimotor conflicts, still strongly affective.
Then images come in, and separate the sensory from the
motor, the reception of stimulus from the movement of re-
sponse. Henceforward secondary attention may be con-
cerned mainly with the stimulus (receptive attention), or
mainly with ideas (elaborative attention), or mainly with
movements (executive attention) : being secondary atten-
tion, being, that is, attention under difficulties, it is always
tinged with effort. Finally, secondary passes over into
derived primary attention; and when it does, affection and
kinaesthetic sensation cease to be necessary factors in the
attentive consciousness. Thus, to begin with receptive at-
tention, we may open our morning's mail with keen excite-
ment, or we may attend to it with no change either of
affective or of kinaesthetic experience. We may, in elab-
orative attention, be absorbedly interested in an argument,
and allow the body to grow stiff and cramped; or we may
take the argument quietly and indifferently. We may, in
executive attention, be wholly bent upon the successful
performance of a skilled action, and may tire ourselves out
in attempting it; or we may make the movements easily
and as a matter of course. What we call habitual, me-
chanical, perfunctory attention involves the two conscious
levels of clearness and obscurity, but does not involve either
affection or kinaesthesis.
It must be remembered that attention is not something rare
and occasional in the mental life, but is the normal state of our
consciousnesses. When we charge other persons with inattention,
we do not mean that they are, literally, non-attentive ; we charge
them with inattention to a particular topic ; and this inattention
meanSj simply, that they are attending to something else. A
284 Attention
strictly one-level consciousness is certainly abnormal^ and prob-
ably never occurs in the normal waking state ; though it may be
realised, or at least approximated, in idiocy (lower level) and in
profound hypnosis (upper level) . But if attention is thus the rule
and not the exception, there is nothing surprising in its becoming
a matter of habit, in its leaving us — in both senses of the word —
unmoved.
The occurrence of kinaesthetic sensations as the object of atten-
tion (for instance, of the executive type) must, of course, be care-
fully distinguished from their arousal by the motor attitude of the
organism in attention. It is the second sort of kinaesthesis whose
weakening and disappearance we have traced.
§ 79. The Experimental Investigation of Attention. — In
taking up the study of sensation, experimental psychology
was greatly helped by physics and physiology. Instru-
ments and methods of research were at hand, and needed
but little modification to render them serviceable ; and a
large body of observations, scattered through the physical
and physiological journals, could be transferred directly
to their proper place in the new science. Hence, from
the very outset, the problems of the quality and intensity
of sensation were attacked with good hope of success;
and although, as is always the case, all sorts of unforeseen
difficulties arose, our knowledge of these attributes has
steadily advanced.
The experimental study of affection began much later.
Here, therefore, we have to make up for lost time. Still,
we are entering on the work in the light of all the experi-
ence that we have gained with sensation, and physiology
has again come to our aid with the instruments needed
by the expressive method. Another ten years will proba-
bly suffice to lay the foundations of a stable affective
psychology.
§ 79- 'I^^'-^ Experimental hivestigatioji of Attetttiojt 285
Interest in attention goes further back. As soon as the
work upon sensation had been fairly started, experimental
psychology turned to the investigation of attention. Here,
however, it found no outside assistance ; physics and
physiology had nothing to offer ; there was only a popular
psychology to build upon. And so the experimentalists
made the mistake — natural, almost inevitable, but still a
mistake — of grappling with the total attentive conscious-
ness, all at once, instead of beginning with a psychology
of clearness, and developing it on the lines of the psychol-
ogy of intensity and quality. The consequence is that we
know less about attention than we should ; a good many
of the earlier studies have to be done over again, little bit
by bit; the problems have to be split up, and made more
manageable. Even so, the experimenter of to-day is ham-
pered by the past ; he wishes to keep all the results of
previous work that can be kept, and therefore, while he
makes his problems as narrow and definite as possible, he
shapes them in accordance with psychological tradition.
But science must set out from the simple, and move gradu-
ally to the complex. A total consciousness is the most
complicated thing that psychology has to deal with, and
its treatment should come last of all. If we want to
understand attention, we must begin at the other end,
with an exhaustive study of the attribute of sensory
clearness.
A few names and dates may be given in illustration. The psy-
chology of intensity is connected especially with the name of
Fechner, who published his Elemente der Psychophysik in i860.
The psychology of quality is connected, similarly, with the name
of Helmholtz, who published the Handbuch der physiologischen
Optik in 1 85 6-1 86 7, and the Ziir Lehre von den Tonempfindiingen
286 Attention
in 1863. The experimental study of attention may be dated from
1 86 1, when Wundt {Beitrdge zur Theorie der Shitieswahrnehmung,
1862 ; Human and Animal Psychology, 1896, 270) began the series
of researches that have culminated in his doctrine of apperception.
The experimental study of affection may be dated, in the same
rough way, from the appearance in 1892 of A. Lehmann's Die
Hauptgesetze des vienschlichen Gefiihlslebens, which took the prize
offered by the Royal Danish Academy of Sciences in 1887 for a
scientific work upon the feelings.
In the meantime, a glance at Fig. 40 will show that the
attentive consciousness sets a number of experimental
problems. There is, for instance, the problem of the area
of the attentive-wave, or of the range of attention. The
question : How many things can we attend to at once .''
has often been asked, and has been very variously an-
swered. A busy man will tell you, if you interrupt him,
that he can't possibly attend to more than one thing at a
time. On the other hand, it is related that Julius Caesar
and the first Napoleon could carry in their heads the topics
of a dozen despatches, and could dictate them without con-
fusion to as many secretaries. There is also the problem
of the length of the attentive-wave, or of the duration of
attention. For how long a time can attention be main-
tained } In everyday experience, the object of attention
is continually changing. Does attention lapse, as we pass
from object to object.'* Then there is the problem of the
height of the attention-wave, or of the degree of attention.
How many different degrees can be distinguished, and
how can they be measured } We speak roughly of close
or rapt or absorbed or concentrated attention, and we con-
trast it with wandering or fitful or divided attention. But
this, after all, is much like saying that our sensations of
§ 8o. Tlie Range of Attention 287
light are black, white and grey ; we want a more exact
statement, and if possible a statement in numerical terms.
The present condition of our knowledge, on these and
kindred topics, is briefly set forth in the following sections.
§ 80. The Range of Attention. — Our problem is to
determine how many impressions can be attended to
together, without decrease of the clearness which each one
of them would possess if the attention were directed
to it alone. We can approach the problem in two ways,
by a simultaneous and a successive method. Thus, we
may present a number of stimuli to a sense-organ at the
same time, and gradually add to them, until it becomes
impossible to attend to all at once. In the case of sight,
for instance, we may show the observer a number of dots,
lines, letters, numerals, simple geometrical figures, bands
of colour, etc., laid upon the same background. Or we
may give the stimuli in succession, gradually increasing
their number till the point is reached at which the iirst
drops into obscurity as the last is given. This method
answers best with auditory stimuli. In both forms of the
experiment, the object of enquiry is the same ; we wish
to determine the limit of complexity at which the attention
becomes unable to cope with the stimuli offered to a parti-
cular sense-organ. And in both the same result is reached ;
the attention is able to embrace six, simultaneous or suc-
cessive impressions, of a relatively simple kind and of
unitary character.
Method of Sbnultaneous Stimuli. — Experiments are made by
means of the tachistoscope, an instrument which, as its name
implies, permits the exposure of a limited field for very brief
periods of time. The time of exposure must be short, since
288
Attejition
otherwise the eye may sweep rapidly over the stimuli, leaving
some to be remem-
bered while others
are directly attended
to ; in this case we
should be dealing,
not with the grasp of
a single attention, but
with a series of atten-
tions. And the ex-
posed field must be
so small that it is
readily taken in by
the eye at a glance,
without eye-move-
ment, since otherwise
the obscurity of the
outlying stimuli may
be a matter, not of
the limit of attention,
but of indirect vision
(§ 20).
If letters are em-
ployed as stimuli, they
must form a meaning-
less series, such as
RKZT. It has been
found that a lamiliar
word of three or four
letters can be appre-
hended by the atten-
tion as if it were a
single letter or geo-
metrical figure ; it is
attended to, not as a
series of letters, but
as a single impression.
v'*''lG. 42. Demonstrational Tachistoscope. A black cur-
tain, mounted on strong spring rollers, is stretched
behind a square opening in a black wooden screen.
The upper Fig. (front) shows the curtain and the
white fixation-mark. The lower Fig. (back) has the
card-carrier thrown back to show the square open-
ing in the curtain itself.
§ 8o. The Range of Attention 289
For the same reason, the attention can deal with numerals better
than with disconnected letters ; any combination of numerals
means something, makes sense.
The maximal range of the visual attention, for a practised
observer, comprises six impressions ; individual ranges differ
between the limits of four and six. Experiments with simul-
taneous impressions of touch have given a like result ; a practised
observer is able to localise six scattered points correctly. This
observation, however, needs confirmation.^
Method of Successive Stimuli. — The running weight upon the
tongue of a bell-metronome is set for two hundred beats in the
minute. The experimenter marks off two series of beats by
sounding the bell simultaneously with the first beat of each series.
The observer is required to say whether the two successive series
are equal or unequal. He must not count, of course ; counting
would mean that a separate attention was given to every beat.
Accurate judgment is impossible in the case of series which
consist of more than six impressions. And if the metronome
could be run very slowly, — say, at fifteen in the minute, — the
range of attention would be no more than six single beats. But
just as in the previous experiment a short word was equivalent,
for the attention, to a single letter, so here a group of beats may,
under certain conditions, be equivalent for the attention to si
single beat. As the rate of the metronome is increased, we can-
not help reading into the succession of strokes a more or less
complicated rhythm. At first, with rates that are still fairly slow,
the beats group themselves into twos or threes, and the attention
is still adequate to six impressions, — six rhythmical units of two
1 It is natural to recall, in this connection, that the point-characters of the
Braille and the New York Point alphabets for the blind both alike ring the
changes on a single symmetrical arrangement of six dots; and it is tempting
to suppose that the limit of six was set by the limit of the range of tactual
attention. But, as a matter of fact, the suggestion of the sixfold unit came
from visual memory of the double-six domino : no preliminary experiments
were made on touch. It also seems certain that blind readers do not, in
general, distinguish the separate dots, but apprehend the total form of the
letter, as if the dotted lines were continuous.
290
Attention
beats (twelve beats in all) or six rhythmical units of three beats
(eighteen beats in all). Finally, at the rate specified above, the
attention can cover only five impressions, five rhythmical units :
but these may now consist of eight or even, it is said, of twenty-
four single beats ; so that the series of five impressions consists
of forty or even of one hundred and twenty metronome strokes.
The groups of eight and of twenty-four are apprehended as units,
akin to the short word of the previous method.
This result agrees very well with the canons of musical and
poetical practice. The musical phrase never contains more than
six measures, the poetical verse or line never contains more than
six feet ; a seven-measured phrase or a seven-footed line falls to
pieces, ceases to be unitary. And the rhythmical wholes of
a higher order, the period in music and the stanza or strophe
in poetry, never contain more than five phrases or verses; as
a rule, neither contains more than four.
Minor Differences of Clearness at the Upper Conscious Level. —
We have seen that the short word, the complexes of geometrical
figures, and the rhythmical unit have, for the attention, the value
of single impressions. Since they stand at the upper level of con-
sciousness, their component parts are all clear. But they are by
no means equally clear. Think, for instance, of a simple rhythmi-
cal unit, such as we might read, in music, ONE — and two — and
th7-ee — and four — and. Here the first member is the strongest
and clearest, the fifth stands next in order, and the second, fourth,
sixth and eighth are relatively weak and obscure. This means
that the upper level of the attentive consciousness is, as a rule,
wrinkled into smaller waves, and not smooth, as it is drawn in
Fig. 40. There are degrees of clearness within the clear. And
this, again, may account for the belief, held by some psychologists
(§ 77), that all possible degrees of clearness may coexist in the
same consciousness. See, however, p. 302.
Whether there are, in the same way, degrees of obscurity within
the obscure, wrinkles or wavelets at the lower level of Fig. 40, is
still uncertain. In any event, these minor waves at the two levels
are quite shallow, and cannot mask the gross difference between
the levels themselves.
§ 8 1. TJie Duration of Attention 291
§ 81. The Duration of Attention. — If, ten years ago, an
experimental psychologist had been asked for how long a
time a single wave of attention could last, he would have
replied without hesitation : For a few seconds only. Many
experiments have been made, he would have said, and all
have led to the same result : that attention is not persistent,
but intermittent, — rising and falling, waxing and waning,
at very short intervals. If you attend as closely as you
can to a simple sense-impression, it does not remain clear,
but becomes alternately clear and obscure ; the attention
fluctuates.
If the same question is asked to-day, the reply must be
that, while we know a good deal more about the general
subject, we do not know how long attention may continue.
It may, undoubtedly, remain constant for two or three
minutes. In the writer's judgment, it may remain con-
stant for much longer periods.
It has been customary to work with minimal stimuli, — stimuli
so small, or so weak, or so little different from their surroundings,
that the least slip of attention, the slightest loss of clearness, will
mean the disappearance of their sensations from consciousness ;
for it is far easier to say that we do or do not hear or see some-
thing than it is to be sure that what we see or hear has grown
more or less clear. Visual, auditory and cutaneous stimuli have
been employed : light and colour, tone and noise, mechanical
pressure and the interrupted current. You may picture the experi-
ment by imagining yourself as seated at a table, gazing fixedly at
a little disc of light grey on a white ground, or listening with all
your ears to the faint hissing of a stream of fine sand, while your
hand rests upon a pneumatic key, the pressure of which records
the moments of disappearance and reappearance of the sensation
upon a kymograph in the next room.
For the sensation does, at least in certain cases, disappear and
reappear. The earlier experimenters found this fluctuation in all
292
Attention
three of the sense-departments mentioned, and they found it with
images as well as with sensations. They accordingly assumed that
it must be due to some common
factor, and — naturally enough — ■
ascribed it to the intermittence of
attention. There were, it is true,
objectors, who pointed out that
the attention need not be involved.
The eye has a mechanism of a(a-
commodation in the lens and its
muscular attachments, and the ear
has a similar mechanism in the
muscle known as the tensor tym-
pani, which pulls upon the drum-
skin : why might not the intermit-
tence of the minimal sensation be
due to peripheral changes, to shifts
of accommodation ? But the reply
seemed conclusive : visual fluctu-
ation was observed during tempo-
rary paralysis of the muscles of
accommodation, and even in the
case of aphacic subjects, patients whose eyes had lost the lens ;
and auditory fluctuation was proved to occur despite the lack of
a tympanic membrane. The theory of an intermittent attention
had apparently won the day.
Nevertheless, the peripheral theory would not down. New ex-
periments were made on touch ; and it was found that the mini-
mal sensations set up by tiny weights and by a weak electric
current do not fluctuate at all. If there is no outside disturbance,
no itching or tingling or movement of the skin, the sensations run
their course without interruption, until they fade out by adaptation.
During these experiments it was observed that a steady attention
might be kept up for at least two or three minutes. New experi-
ments were also made on vision ; and it was found that visual
sensations, too, tend to fade out into their background by adapta-
tion, but that the course of adaptation in their case is interrupted,
Fig. 43. Masson's Disc. The broken
radius, painted blaclc on white, gives
rise, when the disc is rotated, to a
series of grey rings, which grow
h'ghter and lighter towards the per-
iphery. The observer follows the
grey out from the centre, and stead-
ily fixates some point upon the
outermost ring that he can distin-
guish.
§ 82. TJie Degree of Attejttion 293
— interrupted by involuntary eye-movement. The involuntary
movements were timed, their direction was noted, and their extent
was measured : in all three respects there was agreement between
occurrence of movement and disappearance of sensation. Reap-
pearance is due in part to the recovery of the retinal elements
during movement, in part to the faulty adjustment of the eye ; the
eyeball does not return after movement to precisely the position
that it had before movement, and the stimulus may therefore affect
retinal elements which have not as yet been exposed to adapta-
tion. It was found, further, that the negative after-image, the
after-effect of local adaptation (§ 18), behaves in precisely the
same way as the primary sensation ; intrinsically, the course of
the after-image is continuous, but it is interrupted when and in so
far as eye-movement takes place.
So far, then, there is no need to invoke the attention, in order
to explain fluctuation ; we must suppose that the older observers
were misled by preconceived opinion, or perhaps fell into errors
of technique. But what, now, of tone and noise? Well, the
fluctuation of tone and noise is still under discussion. Some
observers have failed to get fluctuation with either; others get
fluctuation with both. The reason for this difference of result
may, possibly, be physical : it is extraordinarily difficult to main-
tain either a tone or a noise at absolutely uniform intensity ; and
a very slight change in objective intensity will, of course, bring a
faint tone or noise to complete disappearance.
Here we are, for the present, at a standstill. We do not know
how long a single wave of attention, carrying a single sensation of
sight or sound or touch, may continue. Nor do we know for how
long a steady level of attention may be maintained under the
conditions of everyday life, where the object of attention is con-
stantly changing. The single wave may continue at least for two
or three minutes ; the writer would not be surprised if it should
turn out that the steady level may be maintained for two or three
hours.
§ 82. The Degree of Attention. — The measurement of
attention is one of the most pressing problems in experi-
294 Attention
mental psychology. If we could measure a man's ca-
pacity of attention, and could discover at any moment
what proportion of that capacity he was using : if, that is,
we could determine the greatest possible height of the
attention-wave, in Fig. 40, and could find out its actual
height in the case before us : then we should have a re-
sult of the greatest scientific importance and of the utmost
practical value. Many experiments have been made, but
the problem is still far from solution.
One difficulty has grown out of the popular use of the
word attention. When the term is used without qualifica-
tion, we naturally think of it as secondary attention ; we
think of the attention that the teacher enjoins on the pu-
pil, of the effort of attention. Primary attention, whether
original or derived, is so natural an attitude, so much a
matter of course, that we hardly notice it : at most, when
we see it in others, we say that so-and-so is absent-minded,
or is in a brown study. This mistake, of identifying atten-
tion with secondary attention, is especially natural to the
man of science, who is always puzzling and searching.
So it comes about that psychologists have proposed to
measure the degree of attention by measuring the degree
of effort which accompanies it. We can measure sensa-
tion ; kinaesthetic sensations indicate the degree of atten-
tion ; hence, if we measure them, we have also measured
attention.
The argument is fallacious, for the simple reason that
the higher degrees of attention do not involve effort.
When we have reached the stage of derived primary
attention, effort has disappeared. The kinaesthetic sen-
sations indicate, not degree of attention, but rather inertia
of attention ; strained attention is, as we have seen, atten-
§ 82. The Degree of Attention 295
tion under difficulties; the very fact that we try to attend
means that we are not giving full attention. It would,
accordingly, be nearer the truth to say that, the more pro-
nounced the effort, the lower is the degree of attention.
Whether this statement is strictly true is, however, a moot ques=
tion. Everyday observation shows that we attend best under
slight distraction. If we are too comfortable, if the conditions
are, so to speak, too favourable for attention, we do not attend ;
we let our mind wander. Now experiment shows that observers
in the laboratory also do their best under slight distraction ; a
modicum of effort, a little bit of resistance to overcome, calls out
their full powers. If the two observations are parallel, then we
must say that effort is neither directly nor inversely proportional
to the height of the attention-wave ; the relation of effort to
degree of attention is equivocal. There would be nothing to sur-
prise us in this result ; consciousness is exceedingly complex, and
the nervous system upon which consciousness depends is exceed-
ingly complicated. But are the observations parallel ? The
laboratory observers will not, in any case, give more than second-
ary attention ; and the slight distraction, thrown in by the experi-
menter, may help them because it standardises the difficulties
under which they attend ; they are henceforth working against a
single, constant difficulty, instead of meeting all sorts of distracting
influences. On the other hand, a chair that is too luxurious to
work in is a chair that favours primary attention, and letting the
mind wander is simply a form of primary attention, — it is atten-
tion to ideas that fit in with the present contents of consciousness.
On the whole, then, these observations do not appear to contradict
the statement that, the greater the effort, the lower is the degree
of attention. Still, this statement does not, of itself, bring us
appreciably nearer to a measurement of attention.
In theory, the most promising method of measuring
the attention would seem to be this : to determine, intro-
spectively, how many degrees of clearness can be distin-
296 Attention
guished in the various departments of sense, and then to
bring every degree of clearness into relation with a definite
sort and amount of distraction. We should thus have
degree of clearness correlated with intensity of distracting
stimulus ; in other words, we should know the highest
degree of attention attainable with a given amount of dis-
traction ; and we might accordingly use the numerical
value of the distractor as a measure of the degree of atten-
tion. If we knew, for instance, that a certain sensation
may exist in ten different degrees of clearness : and if we
had at our disposal ten stimuli which, introduced by way
of distraction, would reduce this sensation from the corre-
sponding degree of clearness to total obscurity : then we
might calculate, from the effect of a particular distractor
in the particular case, what fraction of maximal attention
the observer was giving to the matter in hand. The
method is cumbrous, and difficult to work out; but the
writer believes that it may, some day, be successfully
applied.
In the meantime, many rough tests of degree of attention have
been devised for practical purposes. It is plain, for instance, that
uniformity of performance, the maintenance of a steady level of
achievement without marked variation from the average in either
direction, indicates sustained attention, while the alternation of
very good and very poor work indicates a vacillating attention.
Tests of this kind are valuable so far as they go ; but they cannot
take the place of an exact psychological determination,
§ 83. Accommodation and Inertia of Attention. — We saw
in § ^6 that congruity with the contents of consciousness
is one of the determinants of primary attention. It follows
from this fact that, if two stimuli are presented for atten-
tion at the same time, the one of which is and the other is
§ 83. Accommodation and Inertia of Attention 297
not congruent with ideas already present, they will reach
the crest of the attention-wave, not together, but in suc-
cession ; the stimulus which fits in with the general trend
of consciousness will outstrip its rival. We speak, in such
cases, of a predisposition or accommodation of attention to
a certain impression.
The fact of accommodation of attention may be illustrated by
means of the arrangement shown in Fig. 44. A bell-metronome
is fitted with a cardboard arc,
whose radius is the length / , \
of the pendulum. Scale di-
visions of 5° are laid off
upon the circumference, the
zero-point corresponding to
the vertical position of the
pendulum ; an arrow-head
of red paper serves as a
pointer. The metronome is
set to the rate of, say, 72 in
the minute, and the bell
rings at every complete os-
cillation. In the instrument used by the writer, the bell sounds
when the pointer is at 22°.
The pendulum is released, and the observer is asked to say how
far the pointer has travelled when the bell rings. In a first obser-
vation, he is directed to attend to the moving pointer ; the sound
of the bell is secondary, — it floats, so to speak, upon the main
current of visual change. Under these conditions, the pointer
carries the bell out ; the sound is not heard, on the average, until
the pendulum points to 30°. In a second observation, he is
directed to attend to the bell ; the movement of the pointer is
now secondary, — the expected bell-2t:okes stand out upon an
indifferent shifting field. Under these conditions, the region of
subjective coincidence lies between 10° and 15°. It is evident
that, when the pointer is the main object of attention, the bell
Fig. 44.
?98 Attention
stroke lags behind ; and that, when the bell is the object of atten-
tion, the pointer lags behind. In the first case, the pointer gets
to 30° before the bell (which rang at 22°) is heard; in the second,
the bell is heard (at 22°) when the observed position of the
pointer is only some 15°. The special accommodation of the
attention may separate the two impressions by as much as 10° of
the scale.
The same result appears even if no special directions are given
to the observer. A dial is furnished with a circular scale, and a
pointer is made to revolve before it, very much as a clock-hand
revolves before the face of the clock. Once in every revolution,
when the pointer has reached a certain scale-mark, a bell-stroke
sounds. The observer is asked to say where the pointer is when
the bell rings : no further instruction is given. He accordingly
follows the course of the pointer with his eye, and in the first
revolution refers the sound to some region of the circle. The
second revolution narrows this region ; the third narrows it still
more ; until finally there are only a few scale divisions with which
the bell appears to coincide. In the meantime, attention has been
sharpening to the sound ; an accommodation of attention has
taken place ; the observer is predisposed to hear the bell at a cer-
tain instant. The instant comes ; the bell-stroke rises at once to
the higher conscious level ; and there goes along with it the visual
impression, not of the scale-mark with which it was objectively co-
incident, but of a scale-mark that the pointer had already trav-
ersed when the hammer struck the gong. It is as if there were
a race to the top of consciousness, and the sound, outstripping the
sight with which it started from the scratch, finishes abreast of a
sight that had been given a certain handicap. The time- allow-
ance that the sight receives is offset by the advantage accruing to
the sound through accommodation of attention.
The time required for the accommodation of attention
is about one and a half seconds. Hence, whenever quick
and accurate observation is required in the psychological
laboratory, it is customary to give a signal to the observer
§ 84. TJie Bodily Conditions of Attention 299
a short two seconds before the stimulus is presented.
This is the rule when a single accommodation is required.
If the stimuli are frequently repeated, the attention is able,
within certain fairly wide Hmits, to adapt itself to their
rate of succession. It is possible, for instance, to read a
rhythmical form into sounds that are as little as a fifth of a
second and as much as three seconds apart (§ 80). The
attention can accommodate itself to any rate between
these extremes.
Accommodation implies inertia ; and we find, in fact, that
it is easier to continue a certain direction of attention than it
is to strike out on a new path. You can follow the move-
ment of a single instrument in the orchestra better, when
there has been solo-playing before, than when the whole
group of instruments begin together ; you can finish a con-
versation, once begun, at a distance that would render the
words of an unexpected question altogether inaudible ;
you can trace the upward course of a fire-balloon to a point
at which it would otherwise be invisible. In the same
way, it is difficult to break away from a current train of
thought, and to give your full attention to a letter or a
caller ; and it is difficult to settle down again to your work
after such an interruption. The description of inertia of
attention must, unfortunately, be left in these general
terms ; no special investigation of its laws has as yet been
made.
§ 84. The Bodily Conditions of Attention. — Theories of
attention are as plentiful as theories of affection. Some
of them have been worked out with great ingenuity of
detail. Since, however, all alike are in large measure
speculative, we shall here simply indicate, in bare outline.
r-
300 Attention
what seems to be the most reasonable explanation of the
attentive consciousness.
Neurologists are agreed that one nervous excitation may
influence another in two opposite ways : by helping and
by hindering, or, in technical terms, by facilitation and by
inhibition. We may take an elementary illustration in
each case. If a weak cutaneous stimulus is applied to
the hind foot of a decerebrised frog, there is no visible
effect ; the limb remains passive. But if at the same time
a light is flashed into the eye, the leg-muscles may re-
spond by a strong contraction. Here we must suppose
that the two excitations, the cutaneous and the visual,
have in some way reinforced each other; there is nervous
facilitation. Again, a pressure applied to one part of the
frog's body will touch off a croak ; a strong pressure ap-
plied to a different part will touch off a muscular contrac-
tion. But if the two pressures are applied together, the
frog does not both croak and move ; he does nothing at
all; there is no response to the stimuli. Here we must
suppose that the two excitations interfere with each other ;
there is nervous inhibition.
It seems plain that the conditions of the attentive con-
sciousness are of these two kinds. The clear processes,
at the crest of the attention-wave, are processes whose
underlying excitations have been facilitated. Similarly,
the obscure processes, at the lower level of consciousness,
are processes whose underlying excitations have been in-
hibited. The attentive consciousness is thus conditioned
upon the interplay of cortical facilitation and cortical
inhibition.
When, however, we ask for further details ; when we
try to form a picture of what is really going on in the
§ 84- The Bodily Conditions of Attention 301
cortex when facilitation and inhibition are at work ; then
we are thrown back upon speculation, Wundt, for in-
stance, believes that there is a special cortical centre, in
the frontal lobes, from which the inhibitions proceed.^
His opinion carries great weight, and is supported by a
very considerable body of evidence. Nevertheless, the
action of what he terms the apperception centre is con-
fessedly hypothetical. Other psychologists beheve that
the processes of facilitation and inhibition are diffused
more or less widely over the entire cortex. But their
agreement extends no further. One recent theory main-
tains, for example, that the clearness or vividness of a
sensation is due to the complexity of cortical organisation,
— to the numerous interconnections of the nervous ele-
ments, the extreme variability of the resistances which
they offer, and the number of alternative paths that may
be opened in turn to the excitation-process. Another lays
equal stress upon this complexity of organisation, but uses
it in precisely the opposite way : a sensation is clear when
its excitation-process is strictly local, and obscure when
the excitation-process is spread abroad into many cross-
paths and over many systems of nervous elements. No
one can say which is right and which is wrong ; no one
can say, for that matter, if either is right or if both are
wrong. We must therefore suspend judgment, until more
is known of the physiological mechanism of inhibition and
facilitation.
^ Wundt explains attention in terms of inhibition only, not of inhibition
and facilitation.
302 Attention
References for Further Reading
§§ 75-84. Special works dealing with the psychology of attention
are W. B. Pillsbury, Attention, 1908 ; E. Dlirr, Die Lehre von der Anf-
merksamkeit, 1907; T. Ribot, The Psychology of Attention, (1888)
1890. The first of these books gives a general account of the place
of attention in the mental life; the second is written principally in the
interests of education; the third offers a 'motor theory' of attention,
which is worked out in improved form by J. M. Baldwin, Mental Deii el-
op ment in the Child and the Race : Methods and Processes, 1906, ch. xv.
A brief review of experimental investigations will be found in the au-
thor's Lectures on the Elementary Psychology of Feeling and Atte/ition,
1908, Lects. v.-vii.
F^' Wundfs doctrine of attention, see Grundziige der physiologischen
Psycfiologie, iii., 1903, ch. xviii. ; for his theory of a special brain-centre
for attention, Principles of Physiological Psychology, i., 1904, 315 ff.
Other physiological theories are given by H. Ebbinghaus, Grundsuge
der Psychologie, i., 1905, 628 ff. ; W. McDougall, The Physiological
Factors of the Attention-Process, in Mind, N.S. xi., 1902, 316; xii.,
1903, 289, 473 ; xv., 1906, 329.
Important references are, further, G. T. Fechner, Eleinentc der Psy-
chophysik, ii., (i860) 1907. ch. xlii. ; G. E. Miiller, Zier Theorie der
sinnlichen Aufmerksanikeit, 1878; T. Lipps, GriindtatsacJien des See-
lenlebens, 1883, 125, 151 ; W. James, Principles of Psychology, i., 1890,
ch. xi. ; W. Wirth, Die experinientelle Analyse der Bewiisstseinsphatto-
mene, 1908.
Recent work seems to show that there are two different types of the
attentive consciousness. Some observers find that it always has the
dual formation discussed in the text ; others declare, just as definitely,
that they can distinguish three or four simultaneous degrees of clearness.
The results need confirmation ; it appears, however, that the author,
who belongs to the two-level type, has fallen in § ']'] into the common
psychological mistake of generalising his individual experience. It is
some consolation that the multi-level modes of attention were first
observed, under experimental conditions, in his own laboratory. Cf.
L. R. Geissler, The Afeasurement of Attention, in Amer. Jonrn. Psych.,
XX., 1909, 524 ff.
Since § 82 was written, a first attempt at the measurement of atten-
tion by the prescribed method has been made, with success, by L. R
Geissler, op. at., 475 ff.
PERCEPTION
SPATIAL PERCEPTIONS
§ 85. The Sensory Attribute of Extent. ^ We said in § 12
that visual and cutaneous sensations are spread out, areally,
into length and breadth ; they appear as spatial extents.
This elementary character of outspread or expanse is the
foundation upon which all the forms of spatial conscious-
ness, dehcate and refined as they are, have been built up.
To realise it, we must go behind our adult modes of space-
perception. The words ' area ' and ' extent ' naturally sug-
gest to us some well-known surface, field or wall or table ;
and the surface has a definite form, a definite size, a definite
distance, a definite position within the spatial field ; its per-
ception implies a whole space-psychology. We are now
dealing, however, with extent of a more primitive kind : an
extent that is merely expanse, without particular form,
without recognised magnitude, without relation to other
extents, neither near nor far, — an extent that is present
as extended, and that is all. We can, perhaps, get the
best idea of it by closing the eyes and observing the dark
field : here is an outspread of black, or of dark red, but it
is an outspread with no definite size or shape, and it lies
neither on the eyeballs nor out in space. We get an ap-
proximation to it when we open the eyes in a completely
dark room, or face a bank of thick fog, or gaze through
half-shut lids at the blue sky, though in these cases the
effort to abstract from what we know of space is greater
and oftentimes less successful.
303
304 spatial Perceptions
We may imagine, then, that the untrained eye sees the
landscape as we ourselves see the field of the closed eyes.
But the landscape is not uniform : there is usually a marked
difference between what is above and what is below the
horizon ; and the lower portion is variegated, made up of
patches of colour which, at least in many cases, contrast
with one another. The landscape is also, to a certain de-
gree, in movement : clouds travel across the sky, and living
creatures move about beneath the sky. Visual expanse,
as the world of spatial stimuli is constituted, thus contains
within itself the cues to localisation ; colours are not only
spread out, but they are also spread out here and there,
spread out now here and now there. The perceptions of
form and magnitude, and the perception of place or posi-
tion, have their root in one and the same datum of extent.
Psychology has, unfortunately, been occupied rather with theo-
ries of the origin and growth of space-perception than with the
introspective study of psychological space itself. And we find,
accordingly, the most radical disagreement among authorities. At
the one extreme stand the statements that a certain roominess or
volume "is discernible in each and every sensation, though more
developed in some than in others,"^ and that " the accompaniment
of a local sign or local characteristic is common to all sensa-
tions " ; ^ at the other, the statement that spatiality cannot be
" an original attribute of the elements themselves, in any such
way as intensity and quality of sensations are original attributes " ;
space implies the " arrangement of sensations," so that a sensa-
tion with a spatial attribute is " psychologically impossible."^ The
position taken in the text lies between these extremes. It grants
^ W. James, Principles of Psychology, ii., 1S90, 135. We recur to the
question of the third dimension in § 86 ; cf. supra, pp. 51, 94 f.
2 M. von Frey, Die Gefiihle und ihr Verh'dltnis zu den Empfindungen^
1894, 12.
* W. Wundt, Outlines 0/ Psychology, 1907, 114.
§ 85. The Sensory Attribute of Extent 305
to some sensations an original character of spatial outspread, and
it makes localisation of these sensations a necessary consequence
of qualitative differences within the total bidimensional field.
What sensations, then, have the attribute of extent!
From his own introspection, the author would reply, witb
out hesitation, that visual sensations and sensations oi
cutaneous pressure are spatial, and that sensations of hea^
ing and of smell are spaceless. He inclines to believe,
further, that the other cutaneous sensations (warmth, cold^
pain), the organic pressures and pains, and all the senr
sations of the kinaesthetic senses are endowed with the
spatial attribute, although they play parts of very varying
importance in space-perception. Experiments on this mat
ter are sorely needed ; in particular, it seems impossible
to say, from unaided observation, whether the taste-quali-
ties are extended or whether their spatial appearance i^
due to concomitant pressure.
A psychological field of space, a varied mental expanse
that compels localisation, is furnished primarily by eye and
skin (§§ 39, 50), the two organs whose physical extent liea
open to the simultaneous operation of a number of spatial
stimuli. How it comes about that the sensations from
these sensitive surfaces are ordered and arranged in cor-
respondence with their external stimuli, we do not know.
The suggestion has been made that the arrangement is,
in the last resort, a matter of habit : like impression?
usually come together and are thus approximated in p(;r.
ception ; unlike impressions usually come at a distance
from one another and are thus separated in perception.
Not only, that is, do qualitative differences within the
total field give the general cue to localisation, but the run-
ning together of like qualities and the holding apart of
3o6 Spatial Perceptions
diverse qualities is also, in itself, localisation of a primitive
and undeveloped sort. However this may be, the original
psychological fields are those of sight and pressure. The
visual field is the more homogeneous ; indeed, it has been
doubted whether the skin ever supplies a single field, —
whether it does not rather give a number of heterogeneous,
partial, though partially overlapping fields. Yet if you ob-
serve yourself, not too analytically, as you lie comfortably
in bed, breathing easily and free from organic disturbance,
you may get the impression of a flattened, bidimensional
field of pressure, astonishingly indefinite in form and size,
but still unitary and single.^
§ 86. The Third Dimension. — How, now, do we acquire
the perception of depth, of distance away from us, of a
third spatial dimension .'' This question must be asked
and answered separately for the two great groups of
spatial sensations, the cutaneous and the visual.
(i) Tactual Space. — In its first form, then, our question
runs : Could an organism, of like origin and descent with
man, but lacking eyes, perceive all three of the dimensions
of space .'' And the answer seems to be that it could :
primarily, because the skin can move, in all three objective
dimensions, both upon external objects and upon itself.
The blind organism of which we are speaking is, by
1 Stumpf raises the question ( Ueber deti psychologischen L'rsprung der
Raumvorstellung, 1873, 283) whether an observer who is entirely naive in
matters of space-perception — as he puts it, a new-born baby — would per-
ceive the pressure of a finger run round his body as a straight line or as a ring.
Stumpf thinks that he would perceive it as a ring of pressure in three dimen-
sions ; Ebbinghaus (^Grundzuge Jer Psychologie, i., 1905,453) that he would
get a large ring in two dimensions. The author, in the light of his own ex-
periences of an unitary field of pressure, is disposed to believe that the per-
ception would be that of two closely apposed lines (possibly fusing at their
extremities), or perhaps of a single broad line, traversed in opposite directions.
§ 86. TJie Third Dimensio7i 307
hypothesis, a moving organism. Hence the bidimensional
field of pressure, which forms its stationary equipment of
spatial consciousness, will be transformed into a bidimen-
sional field of active touch ; some preferred part of the
skin — hand, finger-tips — will be used for the exploration
of external objects ; and as^ in all such movement, the
cutaneous impression is connected with complexes of artic-
ular sensations, the right-left and up-down dimensions will
be reduced in conciousness to a common spatial denomina-
tor, and will be represented in terms of the sensations
aroused by movement. But the organism has freedom of
movement in the third or back-forth dimension as well ; so
that it gains a third set of experiences, of the same general
kind as the other two, and yet distinguishable from them ;
it learns to perceive depth or distance away.
The shift of spatial emphasis from skin to joint, from
cutaneous to articular pressure, would hardly be possible
unless, as we suppose, the articular sensations are them-
selves spatial in character. The general transition, from
bidimensional to tridimensional space, must be favoured
by the organism's ability to move and fold the skin upon
itself : arms and legs may be crossed ; the hand may be
passed around as well as across the head or leg or arm ;
or the one hand may explore, in any direction, an object
held by the other hand against the body. Moreover, the
total movements of the organism, movements of locomotion,
involve the third dimension of objective space; and their
conscious representation may be derived, not only from the
skin and the complex of joint, tendon, and muscle, but also
from the kinaesthetic organs of the inner ear.
We have spoken as if the three dimensions of space were, in the
world of stimuli, sharply distinct. In reality, they are conventional.
3o8 Spatial Perceptiotis
It is possible to draw, through a given point, only three straight
lines that lie at right angles to one another ; and it has proved
convenient to work out the science of geometry on the basis of
this threefold system of coordinates. In the same way, it is con-
venient, when we are dealing with space-perception, to think of the
organism as set in a space of three dimensions ; and it is natural to
consider two of these dimensions, the vertical and the horizontal
(up-down and right-left), as lying in a frontal plane, and the third,
the dimension of distance (back- forth), as lying in a sagittal plane.
But the organism itself need know nothing of geometry ; in per-
ceiving the third dimension, it simply perceives objects as near or
remote. And it must be remembered that the dimensions change,
psychc'logically, with every change of front executed by the organ-
ism : turn to your left, and what was length becomes distance ;
lie on your back, and what was height becomes distance. This
constant interchange of objective dimensions has undoubtedly
helped towards the perception of tridimensional space.
At any rate, our view is that this perception of a third dimension
is due to analogy. The two original dimensions of cutaneous
space are translated into characteristic complexes of articular sen-
sations ; and a third characteristic complex of articular sensations
gives rise — by help of the skin's movement upon itself — to a
third perceived dimension. It is in some such way that the con-
genitally blind achieve their direct perception of a tridimen-
sional space (§ 90). They are, however, at a disadvantage as
compared with our imaginary organism ; for the central nervous
mechanism which in man subserves space-perception is essentially
a visual mechanism ; sight-space dominates touch-space ; and the
human being who is deprived of sight is therefore deprived of much
more than his eyes ; he loses also no small portion of his brain.
(2) Visual Space. — If you fix your eyes steadily upon
some object in the field of \dsion, — a tree, let us say, seen
through the open door, — the surrounding objects appear
in their proper shapes and places ; the space-values of the
field are entirely normal. But if, now, you hold up a pen-
§ 86. Tlie Third Dimension 309
cil, at arm's length, between the eyes and the point of fixa-
tion, you find that it doubles, that you see two pencils.
And if, after this experience, you consider the field of
vision somewhat more carefully, you will find that it shows
a good deal of doubling : the tip of the cigar in your mouth
splits into two, the edge of the open door wavers into two,
the ropes of the swing, the telegraph pole, the stem of an-
other, nearer tree, are all doubled. So long, that is, as
the eyes are at rest, only certain objects in the field are
seen single ; the rest are seen double.^ The images of the
former fall upon what are called corresponding retinal
points ; those of the latter upon non-corresponding or dis-
parate points.
Think of the two retinas as slipped, the one over the other, and
as held together by a pin driven through the superimposed foveas
(p. ?>d>). The two pin-holes then represent corresponding points,
the retinal points stimulated by the point in objective space which
the eyes, at any given moment, are fixating. Let other pins be
driven, vertically, through the two retinas, at any points round
about the fovea : in the rough, every pair of pinholes will repre-
sent a pair of corresponding points. Now it is clear, if you work
the matter out by help-of diagrams, that, when the eyes are in
a certain fixed position, only a certain number of the points
in objective space can be imaged upon corresponding retinal
points. The sum-total of these, singly seen and correspond-
ingly imaged, objective points is called the horopter. If, for
instance, the eyes are directed straight forward to the horizon, the
1 Our habitual disregard of double images is one of the curiosities of binocu-
lar vision. It is due in part to the fact that the eyes are in constant movement,
so that the various objects in the field are successively fixated ; in part to the
indefiniteness of indirect vision (p. 83) ; in part to the suppression of the one
or the other image by retinal rivalry (p. 320). Apart, however, from these
peripheral factors, it is due, perhaps mainly, to cortical set or adjustment ; we
mean, expect, are disposed to see singly things that are objectively singlei
Cf. pp. 274 f., 464.
310
Spatial Perceptions
horopter may be a plane surface which is practically identical with
the surface of the ground upon which the observer stands ; if they
are directed upon a point at finite distance in the median plane,
it may consist, in theoretical construction, of a horizontal circle
which passes through the two eyes, and of a vertical straight line
which lies in the median plane
and passes through the fixation-
point.
Suppose, now, that the
images of some object in
external space fall upon
retinal points that are al-
most, but not quite, in cor-
respondence. The object
is seen as single ; for the
corresponding points are
not points in the mathe-
matical sense ; a point on
the one retina corresponds
to a small area on the other.
Suppose, again, that the
images fall on retinal points
that are just a little further
removed from correspon-
dence. The object is still
seen as single ; but it is now seen as extending in the
third dimension. That is to say, tridimensional vision,
the vision of the object as solid, is a sort of halfway
house between single and double vision ; to see a thing
solid is a compromise between seeing it as spatially one
and seeing it as spatially two.
But why should this combination of disparate retinal
images take place at all .'' Why should not disparity of
Fig. 45. Horopter Model, showing
the horopter as a horizontal circle and
a vertical through the fixation-point.
§ 86. The Third Dimension 31I
images mean, at once and always, that we see the object
double ? These are difficult questions ; and we can no
more answer them, in any ultimate sense, than we can say,
for instance, why light of a certain wave-length is seen as
red and not as blue. But we can at all events give a prox-
imate answer; we can show under what conditions the
combination of the disparate images is effected. Human
vision is binocular vision ; the two eyes work together as a
single organ. Now the two eyes are like two separate
observers, who view the objects in the spatial field from
somewhat different standpoints ; so that, within certain
limits of distance, the one eye sees a given object some-
what differently from the other eye (binocular parallax).
There can be no cooperation between them unless their
separate views are reconciled and combined; and recon-
ciliation is, consists in, tridimensional vision.
Draw upon a piece of transparent celluloid the two pairs of
vertical lines shown in Fig. 46. Let the distance between the
left-hand members of the pairs be 64 mm. ;
this is the average interocular distance, or
distance from centre to centre of the pupils
when the eyes are directed straight forward to
the horizon.^ Look steadily at some distant
point, and bring up the transparent slide
before the eyes, in such a way that the mid-
dle points of the left-hand lines fall upon the
foveas. These two lines are then imaged
upon corresponding points, and are seen as one line. The right-
hand lines are imaged upon disparate points ; they are, however,
1 It would, perhaps, be better to say the ' conventional' than the 'aver-
age ' interocular distance, since a distance of 64 mm., though commonly given
as the average, is probably somewhat too high (Nagel's Handbuck d. Physiol.,
iii., 1905, 292). It is best of all to make the measurement afresh in every in-
dividual case (Titchener, Exper. Psydzol., I., ii,, 1901, 245).
3i2 spatial Perceptions
seen as a single line, standing nearer to you than the other. The
combination of disparate images gives the perception of depth.—
Now, if you hold up two pencils before the eyes, that in the left
hand at arm's length, that in the right a little to the right of the
other, and a little nearer ; and if you observe the pair of pencils
first with the left and then with the right eye alone, you will find
that the left-eye view is represented by the left-hand pair of lines
in the figure and the right-eye view by the right-hand pair (binoc-
ular parallax).
Draw upon another slide the pair of lines shown in Fig. 47.
Look at a distant point, and bring up the slide in such a way that
the middle points of the two lines are imaged on the
foveas. You see a single line, the lower half of
which stretches away, while the upper half inclines
towards you. Set up a pencil in this position, and
note the images formed in the two eyes.
Disparity of retinal images thus accounts
for the fact that an object in external space
is seen as solid. But the object is also seen as
distant from oneself, as lying so many metres
away : the point iixated is localised in the third
Fig. 47. dimension, just as definitely as the points
imaged on disparate retinal areas. How do
we localise the fixation-point.''
It is possible, of course, that we localise it, too, in terms
of retinal disparity. What is now the point of fixation,
imaged on corresponding retinal points, has been in the
past, and will be in the future, a point that is imaged on
disparate retinal points : that is to say, it has been and will
be localised, by retinal disparity, in relation to other fixation-
points. In time, then, every point in objective space will
acquire what we may call a relative position in visual space ;
and it is a well-known law of psychology that the frequent
occurrence of a relative character tends to transform it, for
§ 86. The Third Dimension 313
perception, into an absolute character; we speak in absolute
terms of a heavy child, a light travelling bag, a strong voice,
a good light, without any conscious reference or comparison.
The transformation might be greatly assisted, in the case
of visual space-perception, by associations derived from
tactual space : what we can easily reach would be seen as
absolutely near, and so on. Or again, it is possible that
we localise the fixation-point by the help of secondary
criteria. On the whole, however, it seems probable that
absolute localisation is effected by way of muscular sensa-
tions, the sensations aroused by movements of accommoda-
tion and convergence.
The indirect or secondary aids to localisation in depth may be
summed up as follows : linear perspective, the course of contour
lines in the field of vision ; aerial perspective, relative clearness of
outline and distinctness of hue ; the distribution of light and shade ;
interposition, the partial covering of far by nearer objects ; apparent
magnitude, — -a criterion that is especially valuable in the case of
familiar objects ; movement of objects in the field of vision ; and
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 direction.
No doubt all of these aids have had their share in the formation
of our visual space-perceptions ; but it is questionable whether any
one of them is essential.
A like question may be raised with regard to eye-movement :
it is, in fact, a matter of keen controversy whether the movements
of accommodation and convergence are constitutive factors in
space-perception, or whether they are, like the movements of head
and body, of merely secondary importance, — e.g., as aids to fixation.
On the physiological side we have the fact that the two eyes form
a single motor organ ; they move together, automatically, under all
the conditions of a possible fixation. If the fixation-point is very
314 spatial P eixeptions
remote, and lies in the median plane, the lines of regard are parallel ;
and they remain thus parallel for remote fixation at any part of the
field. If the fixation-point lies nearer, in the median plane, the
lines of regard become symmetrically convergent ; the eyes, which
before were directed straight forward at the horizon, turn inward
through equal angles. If the new fixation-point does not lie in the
median plane, the lines of regard become asymmetrically convergent;
in this case, either the two eyes turn inward, through unequal angles,
or the one eye turns in while the other, through a smaller angle,
turns out. These two types of convergence are maintained, again,
for the fixation of points at any part — up, down, right, left — of
the field of vision. In short, wherever the eyes can act together,
for purposes of binocular vision, they do act together ; and the one
thing that they cannot do is to act separately against binocular
vision ; it is impossible, with normal eyes, for the lines of regard to
diverge.
On the psychological side we have a long series of experimental
studies, whose results are not easily harmonised. Psychological
opinion is, in the main, unfavourable to the connection of the depth-
perception with sensations of eye-movement ; and it must be granted
that our discrimination of distance is far more delicate than we
should expect it to be, were it mediated solely by muscular sensa-
tions. Nevertheless, it seems certain that these sensations can furnish
the data for localisation. Recent experiments, carried out with
all precautions, lead to the conclusion that in monocular vision the
sensations of accommodation, and in binocular vision the sensations
of convergence, give fairly accurate cues to the position of objects
in external space. The sensations are not always discoverable by
introspection ; the perception of distance may come to conscious-
ness directly. This, however, is not surprising ; space is so familiar
to us, and the cortical set or adjustment for the perception of space
must be so entirely habitual, that the immediacy of the spatial
attitude is only natural; the surprising thing is, rather, that the
sensations in many cases are discoverable, that the peripheral cues
do persist in consciousness. At the same time it must be re-
membered that sensations of movement, in vision as in touch, are
only secondarily, by analogy, the source of our perception of the
§ 86. TJie Thh'd Dimension 3^5
third dimension ; they are, as we have put it, cues to this perception.
They may get their spatial significance either from the relative
depth-perception due to disparity of retinal images (if that is re-
garded as primary), or by a more direct association with the tridi-
mensional space of touch.
There is, as we have intimated above, a monocular perception of
depth. One-eyed persons have no difficulty 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. In all such
cases, the observer can change his position with regard to sur-
rounding objects ; the objects themselves may change their
positions, with regard to him and to one another; and various
other secondary criteria of distance are still available. As direct
cues to the perception of depth there are, first, the sensations of
accommodation already mentioned ; and secondly, within certain
Umits, — though this factor has been disputed, — the parallax of
indirect vision : the relative position of the retinal images of
objects seen by the same eye in indirect vision changes, if ac-
commodation is changed, or if the eye or the object moves \ and it is
supposed that this shift of position may play a part, in monocular
vision, similar to that played in binocular vision by the disparity of
retinal images. But, whatever its resources may be, monocular
localisation is normally very far from accurate. If a curtain ring
is suspended in the median plane of the observer's body, and he
is given a pencil and required, with one eye closed, to thrust the
pencil through the ring, the pencil will pass at surprising distances
before or behind it.^
All the direct criteria of depth-perception have a limited range
of effectiveness. Accommodation can hardly come into account
for objects more than 2 m. away, and the parallax o^ indirect
vision is of appreciable importance only for objects that lie at arm's
^You may often see connoisseurs looking at a picture monocularly, through
the curved hand. The hand serves as a tube, whose walls shut out dis-
tracting impressions. The main advantage of monocular vision is that the
plane of the picture is less evident to it than to binocular vision, so that the
secondary indications of distance, upon which the artist mus*' rely for his depth-
values, have a better chance to produce their effect.
3i6 Spatial Perceptions
length in the lower portion of the field of vision. Convergence, if
experiments are to be trusted, becomes useless at a distance of
15 to 20 m. Retinal disparity may work, in theory, up to a dis-
tance of some 2700 m. (p. 325) : but in practice it is replaced, long
before this point is reached, by the indirect or secondary criteria of
the depth perception.
§ Zy. The Stereoscope. — If the visual perception of depth
is due to disparity of the retinal images formed by a
single object, then the conditions of tridimensional vision
can be synthetised, artificially reproduced, without our
having recourse to more than two dimensions of objective
space. For the two slightly different pictures taken by
the two retinas are plane pictures, and not themselves
solid facsimiles of the object. Suppose, then, that we
make on paper two drawings of one and the same thing, —
a figure of the thing as it looks to the right eye, and a
figure of it as it looks to the left, — and that we present
each drawing to its appropriate eye. The two drawings,
reversals of the two retinal images of a single object seen
in perspective, must combine to form the representation
of such an object; that is, they must give us the illusion,
or rather the synthesis, of the third dimension. They do,
in fact, combine in this manner; they show what is called
stereoscopic relief . The experiment may be performed in
a great variety of ways : there are, however, two instru-
ments that have an especial importance, — Wheatstone's
reflecting stereoscope and Brewster's refracting stereo-
scope.
An early form of Wheatstone's stereoscope is shown in Fig. 4S.
Two plane mirrors, into which the two eyes look, are so adjusted
that their backs form an angle of 90 °. The diagrams slip into
grooves in two vertical panels, which move in and out on slides
^ 8y. TJie Stereoscope
31;
along two flat wooden arms. The arms themselves turn about a
common centre, which lies in the projection of the line of junction
of the mirrors. The rays reflected from the mirrors fall upon the
eyes as if they came from a single solid object immediately in
\
Fig. 48. Wheatstone's Reflecting Stereoscope. — C. Wheatsone, Phil. Trans, of the
Royal Soc. of London, 1852, pt. i., 3.
front ; or, in other words, the eyes see the combined (virtual)
image of the two figures as if through and behind the mirrors.
The manipulation of the instrument is simple. The diagrams
to be combined are slipped into the grooves. The arms are set in
the same straight line, and theslides are pushed well out upon them,
at equal distances from the mirrors. The panels are placed at an
angle of 45° to the mir-
rors. The observer sits, '\ ,'\ i\
looking into the mirrors, ,' '>' \/ ',
and slowly moves the ends
of the arms outwards, away
from him, until the images
combine. Seen for the
first time, the stereoscopic
effect is surprising in its
tridimensional reality.^
Brewster's refracting
stereoscope, although
scientifically a less valu-
able instrument, has by its cheapness and compactness driven
the reflecting stereoscope out of general use. In its modern form,
the stereoscope is furnished with a light wooden hood, fitting
^ It must be remembered that the use of mirrors involves a left-right con-
version of the stereograms.
Fig. 49. Plan of Wheatstone's Stereoscope.
3i8
Spatial Perceptions
closely over forehead and nose, which serves to exclude lateral
light.^ The eyes look at the stereograms through lenticular prisms
(double convex semi-lenses) : the prisms bring it about that,
despite the convergence of the lines of regard, the stereograms
are imaged on the retinas approximately as if the lines of regard
were parallel ; the rounding of the prism-surfaces renders the
binocular image both larger and more distinct than it would
otherwise be. The long bar, upon which the stereographic card
sHdes, allows of the adjustment of the carrier for eyes of different
focal lengths. The stereograms usually
,'^ supplied with the instrument are paired
_/ \ photographs, taken by cameras whose
lenses are — or should be — separated by
the average interocular distance. If the
cameras are set still farther apart, the
binocular (enlarged, virtual) image shows an
exaggeration of perspective, and the land-
scape or building seen in relief has the
appearance of a model.
It might be supposed, at first thought,
that the stereoscope would settle the con-
troversy regarding eye-movement (p. 313).
There are, however, various reasons why it
cannot. For one thing, it does not permit
of a rigorous control of the conditions of
observation ; the secondary criteria of dis-
tance can never be entirely ruled out. Thus it is possible,
in the Wheatstone stereoscope, to vary the degree of convergence
while the magnitude of the retinal images remains unchanged
(this by pushing the arms still farther out, after perspective vision
has been attained, and then by bringing them back again
into the same straight line), and to vary the size of the images
while convergence remains unchanged (this by moving the
slides in and out, nearer to and farther from the mirrors) ; but the
chief result — in the first case, change of apparent magnitude of
Fig. 50. Plan of Brew-
ster's Refracting Stereo-
scope, old model. — D.
Brewster, The Stereo-
scope, its History, T/ieoiy
and Construction, 1856.
^ The hood-stereoscope was devised by O. W. Holw-^^ in 1S61
§ 8/. TJie Stereoscope
319
the binocular image ; and in the second, change of its apparent
distance — proves very clearly that the perception is largely de-
termined by cortical set ; the observer is influenced by his knowledge
of tridimensional space. For another thing, though we may exclude
eye-movement proper, we can never exclude the motor disposi-
tions of the eye ; and these, on the eye-movement theory, may
take the place of movements actually performed.
Figure 51 shows a simple instrument which embodies the princi-
ple of three more special apparatus. It consists, besides rods and
Fig, 51. Demonstrational Stereoscope, Telestereoscope and Pseudoscope.
clamps, of the hood of a refracting stereoscope (with the prisms
removed), two hand-mirrors, and two pocket-mirrors. If stereo-
grams are placed in clips at the back of the hand-mirrors, we have
a Wheatstone stereoscope. If the instrument is set on a window-
sill, with the hand-mirrors parallel to the pocket-mirrors and
facing the landscape, we have Helmholtz' telestereoscope : the
interocular distance is, to all intents, increased to the distance
between the large mirrors, and the perception of depth is enhanced.
Finally, if the left-hand small mirror and the right-hand large
mirror are thrown down, and the remaining mirrors set, facing each
other, at an angle of 45° to the median plane of the observer, we
320 spatial Pejxeptions
have Stratton's form of Mach's mirror pseudoscope : the left eye
looks directly at its object, while the right eye sees the same ob-
ject twice reflected ; hence the right eye is, so to say, displaced to
the left of the left eye, and the distance-relations of the object are
inverted ; near becomes far, and far, near.
Retinal Rivalry and Binocular Colour- J7iixture. — So far, we
have used the stereoscope for the combination of disparate images
of a single object. We may also employ it for the imaging of
different objects upon corresponding retinal areas. What happens,
if we present to the two eyes pictures of identical shape, size, and
position, but of varied content ?
By far the most frequent result is the phenomenon known as
retinal rivalry. Cut a card to the size of a stereoscopic slide
(refracting stereoscope), and paste on it, at the right distance
apart, two i-cm. squares of red and green paper, the one crossed
by vertical and the other by horizontal black lines. Try to com-
bine the two images in the stereoscope. You will find that they
oscillate : now the red and now the green will appear ; now the
one colour 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. A steady binocular
image is not obtained. Whether the one or the other image can
be held by the attention (which, in this case, means the cortical
set underlying the observer's intention to see red or to see green,
and the eye-movements aroused in the effort to hold, follow,
or find a disappearing image) is a matter of dispute. It seems,
however, that long practice may overcome the rivalry; for ex-
pert microscopists rarely close the unoccupied eye while they are
observing.
Under certain conditions, the phenomenon of retinal rivalry is
replaced by that of binocular lustre. Suppose that you are looking
at a dead-finished surface, which is smooth over its whole extent,
but is not quite even : then the one eye may be in the direction
of the reflected light, so that to it the surface looks bright, while
the other may not be in this direction, so that to it the surf^ice
looks dull, or shows the reflection of some coloured object. Such
a surface, seen inordinary binocular vision, appears lustrous. If,
§
The Perception of Space: Locality 321
then, we place in the stereoscope two pictures of the same object,
the one white and the other coloured, — still better, if the one is
white and the other black, — we shall get the perception of sheen
or lustre. The binocular image of Fig. 52 does, in fact, show a
graphite-like polish,
although, for most
observers, traces of
rivalry also persist.
Lastly, the phe-
nomenon of rivalry
may be replaced by
that of a binocular
Fig. 52.
colour-mixture.
The existence of this mixture has, again, been keenly disputed,
but there can be no question of its occurrence. In the author's
experience, the best way to secure it by aid of the stereoscope is
to combine two small fields of dull and unsaturated colour. The
paper squares must be pasted with extreme
accuracy upon the cardboard slide ; and
the observation should be made with the
images a Uttle out of focus, so that the
contours of the fields are blurred. Some
observers, however, succeed most easily
with identical contours of considerable
complexity : trials may be made with
differently coloured postage stamps.
Where the mixture is attained, the re-
sultant colour is the same as in ordinary
colour-mixture, but its brightness is the
mean of those of the combined colours.
§ 88. The Perception of Space :
Locality. — Our visual perception of
place or position is very highly-
organised ; stimuli that are dis-
tinguished as spatially different, in
daylight vision, are also definitely
Fig. 53. Hering's Binocular
Colour Mixer. L, R, the
two eyes ; b, dark box ; ^g' ,
coloured glasses (red and
blue) ; //, supporting plate
of clear glass ; sss, squares
of white paper. — Her-
mann's Hdbch. d. Physiol.,
iii., I, 1879, 593-
Y
322 Spatial Perceptions
placed in relation to one another.^ With the skin it is other-
wise ; the cutaneous perception of locality is less developed ;
and we are able, in the course of a single experiment, to bring
out various modes and degrees of localisation. Suppose, for
instance, that a pair of compasses, having delicately rounded
points of hard rubber, is set down upon the skin of the fore-
arm, with the points i mm. apart. We perceive, with eyes
closed, a single, sharp pressure upon the forearm. Locali-
sation may be effected in several ways : we may feel an im-
pulse to move the hand of the opposite side towards the part
touched, or we may have a visual picture of the arm and
of the point resting upon it, or the pressure may touch off
at once some form of words (" Halfway up the arm, in
the middle"). The visual picture and the words are, of
course, secondary criteria of cutaneous position, and the
feel of the localising movement, though much more nearly
primitive, is also, if we may trust the conclusions of § 85, in
the last resort of secondary character. Here, then, is what
we may call the absolute perception of cutaneous locality,
the perception of the position of a single pressure. Now
let us consider the relative perception : let the compass
points be gradually separated, by small steps, and let us
note the results. We get, first of all, a larger, blunt point ;
this gradually passes into a small surface of oval form :
then comes a thickish line ; then the perception of two
sharp points, with a faint linear connection between them ;
1 This statement is true as a first approximation to the facts. We ought,
by rights, to take account of indirect as well as of direct vision, of vision of
luminous points in the dark as well as of vision in the daylight, of pathologi-
cal states of the retina, of the action of the ocular muscles in normal and
abnormal conditions, of the position of the head. But if all the details wer<
discussed, the psychology of space-perception would require a large book to
itself!
§ 88. The Perception of Space : Locality 323
and then the two points stand out separate and distinct.
But all this while there has been no perception of the
direction in which the lines or points lie; not, perhaps, till
the compass-points are 25 mm. apart, can the observer say
' longitudinal ' or * transverse.' Our perception begins as
that of an absolutely localised, undifferentiated, cutaneous
expanse ; the expanse presently shows relative spatial dif-
ference, but a difference that cannot be expressed in terms
of direction ; next appears the indefinite perception of
spatial duality, of two disconnected extents ; and, finally,
the relation of these extents becomes definite, and the
perception of relative or directional position is complete.
The testing of the skin by means of the aesthesiometric com-
passes is one of the oldest psychological experiments. E. H.
Weber (p. 219) published in 1834 the results of an exploration
of the entire bodily surface ; he found that the perception of
spatial difference is keenest for the tip of the tongue and fingers,
dullest for the upper arm, thigh, and back. Weber supposed that
he was thus measuring the space limen, the just noticeable magni-
tude of cutaneous space. In fact, however, there is no necessary
relation between spatial duality (difference of localisation) and
spatial magnitude (extension, length of line between points). The
discrimination of magnitudes, with or without the perception of
direction, is a subject for special investigation. We discuss it in
the following § 89.
If two juxtaposed pressure-spots (p. 146) are stimulated at one
and the same moment, the pressure sensations blend, to give a
single, stronger sensation ; there is no spatial distinction. The
determination of spatial duality by the simultaneous stimulation of
pressure-spots is difficult, and the results are variable : they de-
pend, not only on the tendency of the separate sensations to
blend, but also on the intensity of the stimuli used, and especially
on the general disposition (cortical set) of the observer. If, on
the other hand, neighbouring spots are successively stimulated, at
an interval of about i sec, their sensations are distinguished : the
324 spatial Perceptions
difference is at first indefinite, — the pressures are different, and
that is all ; but after several repetitions of the observation it may
become a difference of perceived position.
As regards simultaneous stimulation, the resting eye behaves
in the same way as the skin. The cones have, at the fovea, an
average diameter of 3 /a (i /a = o.ooi mm.). Points in space
can be distinguished if the distance be-
tween them subtends a visual angle of a
little less than i', or, in other words, if the
distance between their retinal images is 4 /a :
this distance just leaves room for an un-
stimulated cone between those upon which
the images are formed. Beyond the fovea,
in indirect vision, the separation of ob-
FiG. 54. A field of cones jective points necessary to their separate
(shown schematically as localisation rapidly increases. Whether
hexagons) is stimulated ^ -'
by a sheet of half-white juxtaposed cones give the perception of
and half-black paper. \Q(^2i\ difference when successively stimu-
The sheet has been
cut through along the lated, the author does not know.
horizontal line, and the jf the resting eye is required, not to
upper portion has been ,.. ., . ^ . ■> . . ^ ^i.
shifted a trifle to the distmguish pomts m space, but to note the
right. The black of this relative displacement of lines or edges of
upper portion now leaves g^.f^^es, localisation is far more accurate.
unstimulated cones which '
are still affected by the Two Straight lines placed end to end are
black of the lower por- perceived to lie apart under a visual angle
tion. Hence the dis- ^
placement is perceived, of only 5", or, in Other words, when the
— E. Hering, Ber. d. distance between their retinal images is less
math.-phys. Klasse d. k. 111 i •
sacks. Geseiischaft d. than 0.5 /a. The most probable explanation
Wisse7ischaften, li., 3, of this fact is given in Fig. 54.
^ ^^' ^ ■ Precisely the same disparity of retinal
images is sufficient, in binocular vision, to give a noticeable differ-
ence of depth. The classical experiment is as follows : three fine
needles are set up, in the transverse plane, at a short distance from
the eyes ; the two outer needles are fixed in position, while the
middle needle is moved, in successive observations, back or forth in
the median plane, until the difference in depth is remarked. In a
particular case (interocular distance, 66 mm.), the needles were 0.7
§ 88. TJie Perception of Space : Locality 325
mm. in diameter, and were set up 3 mm. or 5' apart at a distance of
2 m. The limen of depth was reached when the middle needle
was moved 1.5 mm. toward or away from the observer. This
amount of displacement means a difference of 5" in the position
of the retinal images of the two eyes.^
The Law of Identical Visual Direction. — The intimate cooper-
ation of the two eyes in binocular vision is well shown by the fol-
lowing experiment. Place yourself before a window from which
you can see, in the distance, two sahent objects — say a tree and
a chimney — not too far apart. Make an inkspot on the window,
for a fixation-point, and stand in such a position that the spot,
fixated by the one eye alone, covers the tree, and fixated by the
other eye, without change of the position of the head, covers the
chimney. Now fixate the spot with both eyes ; you see the tree and
the chimney — in rivalry, of course — directly behind the fixation-
point. Inkspot, tree, and chimney have the same direction, lie in
the same straight line ; and this line, if prolonged to the observer's
face, would pass between the eyes, or, as Hering puts it, would
strike the fovea of a single, cyclopean eye, set midway between the
actual eyes.
Internal Localisation. — A special question which belongs to
this Section is that of internal localisation (§ 57). How do we
localise the organic sensations? It may be noted, first, that if
the sensations are at all intensive there is a tendency to move the
hand over the skin of chest or abdomen. Whenever this explora-
tory pressure sets up, diminishes, enhances, or puts an end to an
internal sensation, a cue to localisation is given. Secondly, how-
ever, certain organic sensations are regularly connected with other
localised sensations. Thus, hunger and intestinal pain may get
their place-reference from attendant contraction of the diaphragm,
or from distension and contraction of the abdominal wall ; stuffiness
1 The further limit of depth-perception, the limit beyond which no dif-
ference of depth can be perceived in terms of retinal disparity, lies at the
point at which the interocular distance itself is viewed under the smallest
visual angle that permits of depth-discrimination. As the average interocular
distance is taken as 64 mm., and the visual angle in question is 5", the limit
must be placed, approximately, at 2700 m. (p. 316).
326 spatial Perceptions
and exhilaration may be referred to chest or head through associ-
ated contractions of the chest muscles, or constriction and relaxa-
tion of the nasal passages and respiratory entrances. Here would
fall, also, the cases of reflex reference (pp. 184, 186). Thirdly,
in minds of visual constitution, organic sensations are directly
localised by help of visual images. The author has a definite
mental picture of the course of a draught of cold water through
the alimentary canal, though he must confess that the picture is
accurate neither in scale nor in directions. Visual association is
probably responsible, also, for the general tendency to localise
organic sensations towards the front of the body (p. 187). Alto-
gether, then, organic localisation is an indirect affair, due to pal-
pation, to connection with localised sensations, to visual associa-
tions, and influenced, no doubt, by more or less accurate know-
ledge of the position of the principal organs of the body.
§ 89. The Perception of Space: Magnitude. — The cutane-
ous perception of magnitude may be determined either by
linear stimuli or by point-distances. It is especially in-
teresting to compare point-distances at different parts of
the body. If the one distance is kept constant, and the
other varied from observation to observation, we shall pres-
ently arrive at subjective equality: it has been found, for
instance, that a distance of 5 mm. on the finger-tip is the
equivalent of a distance of some 16 mm. on the wrist. In
general, as this instance shows, point-distances are perceived
as larger at parts of the skin which have the more delicate
discrimination of locality ; so that the points of a pair of
compasses, drawn across the face above and below the lips.
or drawn down the inside of the arm from shoulder to finger-
tips, seem to diverge and converge according to the local
sensitivity of the regions traversed. There is, however, no
direct proportionality between the two perceptions. More-
over, if the point-distances are relatively large, local dif-
§ 89. The Perception of Space: Magnitude 327
ferencestend to disappear, and subjective tends to coincide
with objective equality. Here we have evidence of the
dominance of visual over cutaneous space; vision has in-
formed us of the actual size of the areas stimulated, and
we equate the stimuli by what we know rather than by
what we feel.
Very many experiments have been made upon the com-
parison of point-distances by the eye. The results show
that, at any rate for stimuli of a middle range of magnitude,
the differential limen is alwavs the same fraction of the
distances compared ; in other words, the visual perception
of magnitude obeys Weber's Law. Hence it is natural to
suppose (and, indeed, there is introspective warrant for the
hypothesis) that the distances are compared in terms of
the sensations aroused by eye-movement; the greater the
intensity of these sensations, the greater is the distance for
perception (p. 219).
It is worth remarking that we get differences of perceived
extent by the stimulation, at various intensities, of a single pres-
sure-spot, and of a single retinal cone. Further : we have two
cutaneous limens, for the perception of linear magnitude, whether
we work with linear stimuli or with point-distances ; for the per-
ception of linear extent, as such, appears earlier than the percep-
tion of its direction upon the skin.
The Perception of Form. — The cutaneous perception of form is,
in general, very inaccurate. At the parts of greatest local sensi-
tivity we find small liminal values : thus, the end of a glass tube
pressed down upon the tip of the tongue or of the middle finger
will be perceived as circular if the glass is 0.5 mm. thick and the
outside diameter of the tube is 2 or 3 mm. There can be little
doubt, however, that this perception is indirect, based chiefly upon
visual association.
Contour lines are followed most easily by the eye if they are
continuous, by the moving finger (active touch) if they are broken.
328
Spatial Perceptions
You may test the latter statement by trying to read, with the
finger-tips, two sentences, the one printed in ordinary raised print,
the other in the dotted bUnd-print.
The Blind Spot. — The bUnd spot (p. ZZ) does not interfere
with our perception of visual magnitude ; points whose retinal
images he on either side of it do not run together, but retain their
normal separation. Two factors appear to have contributed to
this result. First, there is no blind spot in binocular vision ; the
part of the combined field to which the one eye is blind is seen
by the other. But secondly, and more importantly, the eyes are
constantly in motion;
and the moving eyes
give us the perception
of spatial continuity.
Primarily, therefore,
points are localised and
magnitudes are esti-
mated in direct vision,
and the habit of direct
vision — save under
special experimental
conditions — is carried
over to indirect vision. Our habitual disregard of double images
(p. 309) is a fact of the same kind.
As to what happens at the blind spot itself, opinions are divided.
Some psychologists think that the area which it occupies is filled,
in the field of vision, either by irradiation from the light and
coloured surfaces which surround it, or by imagination : in look-
ing at a patterned wall-paper, e.g., we carry an image of the
pattern over the blank space which represents the projection of
the blind spot. Others declare that the blind spot is simply and
literally blind ; we see nothing at that part of the field ; but, if we
see nothing, we cannot see a gap or blank. The field is, then, in
fact, continuous, although localisation, for the reasons given above,
takes account of the existence of the blind area.
It has recently been asserted that if one looks suddenly, with a
single eye, at some uniform and brightly illuminated surface, one
a
Fig. 55. Blind Spot of the author's left eye, plane pro-
jection. Reduced from a large diagram, in which
the distance from the inner edge of the fixation-
mark a to the inner edge of the blind spot was
54.5 cm. The distance of the fixation-mark from
the eye, in the experiments, was 2.2 m.
§ 89. The Perception of Space: Magnitude 329
sees the projection of the blind spot as a faint grey patch (the
central grey, p. 90).
The Various Psychological Spaces. — Geometry and the physical
sciences know of only one space, which is always and everywhere
the same (p. 7). It is clear that a like statement cannot be made
of psychology. We have already said something of four psycho-
logical spaces : the bidimensional fields of the skin and the resting
eye, and the tridimensional spaces of active touch and of the
moving double-eye. But there are incongruities, again, within
these four systems, for finger-space is not back-space, and the
space of direct vision is not that of indirect vision ; it would, in-
deed, be difficult to say how many psychological spaces can be
distinguished. At all events, instances ofspatial conflict are not far
to seek. The cavity of a hollow tooth seems larger to the explor-
ing tongue than to the passively pressing finger ; to both, it seems
larger than it does to the eye. If you bite far out over the lower lip,
the upper jaw seems narrow and small as compared with the
tongue's report of it, The sight of the back of one's head in a
mirror is — to a man, at any rate — curiously disconcerting, so
different is the visual magnitude from the magnitude registered
by the hollow hand.
Plainly, then, some sort of reconciliation or compromise is
required. Reconciliation is possible, because the attribute of
sensory extent, the fundamental spatial datum, is identical for all
the spaces. A first practical step towards it is taken in the prefer-
ence given to the spot of clearest vision and the spots of clearest
touch, to the fovea and the finger-tips : the other spaces are
usually ignored. But these two residual spaces are themselves not
in accord. Which of them takes precedence of the other?
Helmholtz declares for touch. " We are continually controlling
and correcting the notions of locality derived from the eye by the
help of the sense of touch, and always accept the impressions on
the latter sense as decisive." The author, if he were compelled
to make a choice, would, despite the authority of Helmholtz, pro-
nounce in favour of sight. In the daylight, our space world is
surely, for all practical purposes, a world of space seen ; and even
in the dark most of us, probably, visualise our way about. Really,
330 Spatial Perceptions
however, the issue is not drawn in these terms. We build up, in
course of time, a composite idea of space, partly from data of
visual, partly from data of tactual experience, but more especially
from what we learn of measured, physical or mathematical space.
This composite idea rarely appears as a whole, clear and well-
defined, in consciousness ; often, indeed, the nervous mechanism,
inherited and acquired, works automatically, without consciousness
at all ; but often, again, and perhaps as a rule, our generalised or
standardised space-experiences show as a total conscious attitude
(§ 138). Then, in any given case, the attitude is particularised
as circumstances determine ; we apply now this and now that
partial and temporary standard ; we may act as if on the principle
that seeing is behaving, or as if on the opposite principle that ap-
pearances are deceptive ; we trust our eyes, or our fingers, or
neither, or both. We follow the path laid out for us, not by sight
or touch, but by the present trend and tendency of the cortex.
§ 90. Secondary Spatial Perceptions. — Odours and sounds,
although they do not possess the attribute of extent, may
yet be localised. They have their physical origin at some
point in objective space, and if we can get any cue to this
point of origin, we can place the sensations in the visual
or tactual field.
Odours may sometimes be referred to a certain direction
in space by a process of elimination : we get the scent if
we hold the head in a certain way, and we lose it if we
turn our face in any other direction. Where this direct
cue fails, we rely upon intensity ; we move to and fro,
sniffing, in the hope that an unusually strong whiff of the
odour will give us our bearings. But the quest is uncer-
tain ; the sense-organ soon becomes adapted (p. 124); and
if the scent is weak, or the stimulus has had time to diffuse,
localisation is impossible.
Soimds, on the other hand, are as a rule localised readily
§ 90- Secondary Spatial Perceptiojis 331
and with considerable accuracy. Under experimental con-
ditions, localisation appears to depend on the cooperation
of three principal factors. The first of these is the rela-
tive intensity of the sound as heard by the two ears : it is
difficult to distinguish front and back, in the median plane,
and localisation is poor where changes in the binaural
ratio are slight, e.g., at the sides, in the region of the axis
of the ears. The second is absolute intensity : there are
characteristic differences in intensity when the sound
comes from different directions. And the third is com-
plexity: musical tones, the human voice, complex noises,
can be localised far more accurately than pure tones. At
the same time it is not difficult to arrange conditions,
whether for monaural or for binaural hearing, such that
localisation of the auditory stimulus is impossible.
We saw, in § 86, that the congenitally blind might achieve the
direct perception of tridimensional space. There is, however, no
doubt that they live, very largely, in the secondary space of hear-
ing. We have the testimony of a blind author that the blind
idea of space " depends far more upon hearing than upon the sense
of touch," and that the tactual idea of plasticity, of solidity, i»
only an occasional factor in the blind space-consciousness.
It has been suggested that what is known as the ' warning sense '
of the blind — their perception of the presence of some solid
object in their near neighbourhood — may also be due, either
directly or indirectly, to hearing. The perception may be aroused
directly by the reflection of sound-waves from the surface of the
object; or the auditory stimuli may react upon the kinaesthetic
organs of the inner ear, and the perception may be based upon
vestibular sensations which, in the seeing, are unremarked (§ 54).
Since, however, the warning sense is present in deaf patients, and
in patients with normal hearing whose ears are stopped, it seems
that in these cases a change in temperature, or in the pressure
of the air, is responsible for the perception ; the sense is, in fact,
332 Spatial Perceptions
referred by the blind to the face. There is, of course, no reason to
think that the warning sense is confined to a single sense-organ ;
cochlea, vestibule, pressure-spot and temperature-spot may all, OD
occasion, be pressed into the service of space-perception.
§ 91. Illusory Spatial Perceptions. — In a certain sense,
most of our space-perceptions are illusory. Distance, for
instance, very soon closes up on itself ; if we try to stop,
halfway, a friend who is walking down a long corridor,
we shall be likely to call out before he has gone more than
a third of its length; at a little distance from the eyes,
tridimensional space is perceived as a shallow relief. Mag-
nitude, too, is illusory; the size of the moon in the sky is
that of a pea held close to the eyes. Form is illusory ;
how often do we see a square table as square .'* Only di-
rection is adequately perceived. Yet we do not, somehow,
think of all these things as illusions : they represent the
natural and normal way in which space is perceived ; we
are used to them, and can correct them, make allowance
for them.
There are, on the other hand, certain simple arrange-
ments of dots and lines that yield, in perception, a result
markedly different from the result which measurement
would lead us to expect. These figures, grouped together
under the purely descriptive name of the geometrical illu-
sions of sight, have in recent years been made the subject
of detailed study : our Fig. i (p. 7) has, in particular,
been repeatedly discussed and variously explained. The
simplicity of the forms is, in fact, misleading ; explanation
is very difficult ; and there is no present prospect of agree-
ment among investigators. Three types of theory have
emerged from the discussion : we may illustrate them by
reference to Fig. i.
^ 9^' Illiisojy Spatial P erceptiojis 333
Theories of the first type explain the illusions in terms
of the physiological mechanism of perception. It is pos-
sible, for example, to explain the illusion of Fig. i by refer-
ence to eye-movement. We are to compare the main
lines of the figure, and we move the eyes
along them with this comparison in view.
But in the upper half of the figure the
eyes are tempted to continue their move-
ment beyond the proper point, from the
shaft to the feathers of the arrow ; in the
lower half their movement is checked
by the enclosing arrow-heads. Hence
the upper vertical appears longer than
the lower.
Theories of the second type declare
that illusion is due to the associative sup-
plementing of the perception ; ideas are
read into the figures. Thus, according to
one authority, v/e tend, just because we
are human beings, to humanise the forms ^ ^ , „, ^,. ,
^ ' F[G. 56. Ebbinghaus
about us; a column seems, according to Swallow Figure,
showing that the il-
its proportions, to stretch up easily to its lusion of theMuiier-
load, or to plant itself doggedly under a ^--yer Figure, \\g. i
^ °'^ J does not disappear u
too heavy pressure, — precisely as a we read into it (in
, the S6iise of the
man might do. So we read ourselves, or second type of
feel ourselves, into the lines of the "-"^""'^^ ^^^^^^ t'^^'
are opposed to the
figure ; the upper vertical has room to direction of illusion.
1 ,, , . , , — H. Ebbingliaus,
expand, the lower is cramped and con- Gnindznge d. Psy-
fined. The illusion of length results. ^/J^/^^-^.-.ii., 1908, 96.
Theories of the third type emphasise our own general
attitude to the object of perception. If we take the figure
as a whole, we get a pronounced illusion : the large open
334
Spatial Perceptions
area above, and the closed diamond-shaped area below,
strike the attention ; we say, from total impression, that
the upper vertical is the longer. If, however, we take the
figure critically, analytically, limiting our attention to the
two verticals and disregarding the oblique lines, the illusion
is greatly reduced, and may, with practice, entirely dis-
appear.
There is no doubt that perception may be modified both by
associated ideas and by general disposition (cortical set). The
author remembers a vaudeville performance
in which a professional strong man was mer-
cilessly hissed ; the man had gilded his dumb-
bells, in honour of some holiday, and the
audience took them for tinsel; only when he
sent the mass of iron crashing through the
nearest row of seats did the hissing change to
applause. So with disposition ; we are con-
tinually misreading the headlines of the news-
FiG. 57. Mach's Book, papers because we are prepared, predisposed,
-Y..M^z\ Deitrage ^^^ ^^^^^ ^^ ^ certain sort. We may grant,
zur Analyse aer Kmp- _ j ^
findu7igen, 1886, 97; then, that these factors are operative. Never-
Popuiar Scientific Lee- theless, in the author's opinion, the eve-
hires, [1867] 1S95, 80. ' ' '
movement theory goes to the heart 01 the
matter. It is supported by many lines of evidence, and not
least by the fact that actual record of eye-movement proves
the eyes to move differently according as the observer is or
is not subject to the illusion. Tt has the further advantage
of bringing into line a series of illusions known as the illusions
of reversible perspective. Thus, Fig. 57 shows an open book.
Is the back or the front of the book turned towards you?
Fixate the middle line, or move the eyes from its extremities out-
ward, and you see the back ; fixate an outer line, or move the eyes
from its extremities inward, and you see the front. And, if you
think that the book reverses when you expect it or mean it tc
reverse (cortical set), you will find — such, at least, is the author's
§ 92. Theories of Space-Perception 335
uniform experience — that, as a matter of fact, the fixation-point
has also shifted. All these points, however, are still, so far as
detailed explanation is concerned, matters of controversy.
Page 336 contains a number of the more familiar illusion- figures;
the reader should try to explain them for himself.^ The cutaneous
and tactual spaces show similar illusions ; but the results vary
greatly, both with variation of the experimental conditions and with
the observer's attitude, so that no unitary principle of explanation
can be offered.
§ 92. Theories of Space-Perception, — The psychological
theories of space-perception range between two extremes.
On the one side we have theories which derive, or generate,
the perception of space from the intimate connection of
sensations, though these are themselves considered to be
entirely spaceless. On the other side we have theories
which endow the individual sensation with all the funda-
mental spatial characters. The theory implied in the fore-
going §§85 ff. takes a middle position : it makes extent an
attribute of certain classes of sensations, regards localisa-
tion as a corollary of extent, and tries to find definite,
secondary conditions for the perception of depth.
As an illustration of theories of the first class, the genetic theo-
ries, we may take Wundt's account of the origin of spatial ideas.
Every point upon the skin, Wundt says, gives to its sensation of
pressure, however evoked, a peculiar qualitative colouring, which
may be called a local sign. But, in passing from a sensation of local
sign a to one of local sign b, we experience the movement-sen-
sation B ; whereas, in passing from a to the more different e, we
1 The three squares at the top of the page are known as Helmholtz'
squares; the two horizontal figures below as Oppel's lines. The large diagram
to the left, below the lines, is Zollner's pattern; that to the right is Poggen-
dorfPs figure. The single diagram below these is called Lipps' parallels. The
broken circle to the left, at the bottom of the page, is Miiller-Lyer's circle; the
diagram to the right shows Miiller-Lyer's semicircles.
336
Spatial Perceptions
\
\
\
§ 92. Theories of Space-P erception 337
get the stronger movement-sensation C. The fusion of pressure-
sensations and their quahtatively graded local signs with intensively
graded movement-sensations furnishes, as its resultant, a bidimen-
sional touch-space. It is then not difficult, if we grant qualitative
local signs to the articular sensations, to pass to tridimensional
perception. Wundt adds that the limbs tend to move in straight
lines to and from objects in the field ; hence the dimensions of
space are naturally regarded as rectilinear. Similarly, every point
upon the retina gives to its sensation, whatever that may be, a
quaUtative local sign, and this fuses with the intensively graded
sensations of movement which serve to bring the stimuli upon the
fovea : the result is a bidimensional sight-space. The perception
of depth requires no additional factors. For, if the eyes move
from a \o b '\xi the same transverse plane, the change in local sign
and the movement-sensation are ahke in both ; whereas, if they
move from a farther a to a nearer b, the retinal images of a move
to the right in the left eye, to the left in the right eye, and the
right eye itself turns to the left, the left eye to the right. The
elements of space-perception are thus unchanged, but the special
way in which they are united is entirely different in bidimensional
and in tridimensional vision.
As an illustration of theories of the second class, the nativistic
theories, we may take Hering's account of visual space-perception.
Every retinal point, according to Hering, furnishes, besides its
sensations of light and colour, three space-sensations, those of
height, breadth and depth. The two former are identical at cor-
responding retinal points ; they give us, taken together, the percep-
tion of direction. The sensations of depth are also identical at
corresponding points, but are of opposite sign, — positive in the
one eye, negative in the other ; they are identical and of the same
sign at symmetrically situated retinal points ; they are, in fact, posi-
tive (mean greater distance) on the outer halves of the retinas,
and they are negative (mean less distance) on the inner halves.
Every binocular perception of an object imaged on corresponding
points has, then, the average direction and the average depth-value
of all these space-sensations. But the average depth- value is zero ;
the depth-sensations are of opposite sign ; so that all such percep-
338 spatial Perceptions
tions are localised, by a simple act of sensation, in a plane, Her-
ing's nuclear plane, which has no depth-value at all. Let the
point in this plane which corresponds to the two foveas be made
the centre of a system of coordinates, such that the height and
breadth coordinates lie in the plane itself, and the depth coordinate
lies at right angles to it : then we have a geometrical construction
which, subject to empirical correction, is adequate to space-percep-
tion. Since the observer's body is included in this tridimensional
space, the distance of objects from the eye is taken account of in
the construction.
What is to be said in criticism ? Against Wundt, principally
this : that the theory does not explain. To say that space results
from the fusion of quality and intensity, however plausibly the
statement be made, is to leave us with a mystery ; nowhere else,
over the whole range of psychology, does the concurrence of
attributes (pp. 54 f.) give rise to an absolutely new form of con-
sciousness. And against Hering, this : that the theory is psy-
chologically impossible. Sensations of height and breadth might
pass muster, if we mean by them qualitative local signs, but a'
sensation of depth is an impossibility : depth has no specific quality
that can be seen, and, if it had, we have no sense-organ where-
with to see it. Here is, of course, only the barest outline of a
criticism ; we have no room for details. It may be added, how-
ever, that the congenitally Wind, to whom sight has been restored
by operation, see the world at once as a manifold of two dimen-
sions ; neither is surface generated by eye-movement, nor is there
any primal perception of depth.
References for Further Reading
§§85-92. General references are : H. L. F. von Helmholtz, Hand-
buch dcr physioloi^ischen Optik, 1896, 613 ff. ; B. Bourdon, La percep-
tion visuelle de I'espace, 1902 ; O. Zoth, Aies^enbcweguiigen und Geskhts-
-ivahrnehmungen, in Nagel's Handbuch, iii., 1905, 283 ff. ; H. Ebbing-
haus, Grundzuge der Psychologies i., 1905, 432 ff . ; ii., 1908. 37 ff. ;
W. Wundt, GrimdzYige der physiologischen Psychologic, ii., 1910, chs.
xiii., xiv.
References for Further Reading 339
§ 87. An historical sketch of stereoscopy and pseudoscopy will be
found in the author's Experh/ietttal Psychology, I., ii., 1901, 257 flf.
§ 90. D. Starch, Feri)netry of tlie Localisation of Sound, in Univer-
sity of Iowa Studies in Psychology, iv., 1905 ; v., 1908 (Psychological
Review Monograph Supplements, 28, 38). On the warning sense of
the blind, see a series of articles in \ht Zeits. f. experiment. Paedagogik,
iii., 1906 flf. ; also L. Truschel, Das Problem des sogenatmien sechste?i
Sinus der Blinden, in Arch. f. d. gesa/nte Psychol., xiv., 1909, 133.
§91. W. Wundt, Die geometrisch-optischen Tduschiingen, 1898;
T. Lipps, Raiimaesthetik iind geonietrisch-optische Tdnschungen, 1897;
V. Benussi, Z2ir Psychologie des Gestaltcrfassens, in A. Meinong, Unter-
suchungen Z7ir Gegenstandstheorie und Psychologie, 1904, 303 flf. A
select bibliography of works upon optical illusion is given by the author,
Exper. Psychol., I., ii., 1901, 305 ff. ; a shorter list by Ebbinghaus,
Psychologie, ii., 1908, 51 f. For eye-movements, see C. H. Judd and
others, in Yale Psychological Studies, N. S., i., 1905 (Psychological
Review Monograph Supplement, 29); for perspective illusions, J. E.
W. Wallin, Optical Illusions of Reversible Perspective, 1905.
§ 92. A brief account of Wundt's theory will be found in W. Wundt,
Outlines of Psychology, tr. 1907, 113 flf.; of Hering's, in E. Hering,
Beitrdge zur Physiologic, Heft 5, 1864, § 124.
TEMPORAL PERCEPTIONS
§93. The Sensory Attribute of Duration. — All sensa-
tions have the attribute of duration ; all, even the briefest,
may be observed as courses in consciousness, as mental
processes. And all sensations may be localised in time,
as occurring before or after some given sensation. The
attribute of duration is, in the author's view, primitive and
ultimate, like that of spatial extent ; it corresponds, in
consciousness, to the rise, poise and fall of the excitatory
nervous process. Localisation in time may also, perhaps,
be regarded as analogous to localisation in space. The
conscious present (p. 19) varies greatly in objective dura-
tion ; but there can be no doubt that it may last for a
considerable period of time : it is ' now ' during the whole
hour that we spend in the dentist's chair, or during the
whole morning that we devote to some baffling problem.
Within these longer mental presents, at any rate, there
will be occasion for the running together of like and the
setting apart of diverse qualitative experiences ; and the
conscious grouping and separation may not only give the
cue to temporal localisation, but may itself be localisation
of a crude sort. Duration, the moving extension of a
time-field, thus appears as the foundation upon which all
forms of temporal consciousness are built up.
Time is usually regarded as a linear extension, a one-dimen-
sional manifold. To the author, it seems that psychological time
is rather a surface, a bidimensional manifold, and that its two
dimensions are simultaneity and succession. It is true that simul-
340
§ 93- ^-^^^ Sensory Attribute of Duration 341
taneous sensations go on ' at the same time ' ; but this same time,
in which they go on, is physical time ; psychologically, each one
of them goes on in its own time. There are thus a number of
linear times proceeding side by side ; and lines generate a sur-
face. The great difference between bidimensional time and
bidimensional space is that the latter is given once for all,
and is simply articulated in the course of our experience, while
time is made as we live ; the time-field is constantly extending.
The existence of a conscious time-field, an extended present, is
vouched for by our perception of melody, of rhythm (p. 289), of
a polysyllabic word. Under laboratory conditions, this mental
present reduces to a period of a couple of seconds : durations
themselves are most accurately estimated at about 0.6 sec. ; the
natural rhythmical unit occupies i sec. ; accommodation of atten-
tion (p. 298) requires 1.5 sec. ; the accuracy with which two suc-
cessive stimuli can be compared increases up to a limit of 2 sec.
after the presentation of the second stimulus. Nevertheless, as
the following figures will show, even the least of these fields per-
mits of temporal localisation ; and it may be added that certain
experiments seem to indicate a mental present of 6 sec. duration.
What, then, is the lower limit of temporal localisation? If
stimuli follow one another with great rapidity, we have a con-
tinuous and uniform sensation ; if they come at a lesser rapidity,
we have continuity without uniformity, — in vision, shimmer or
flicker ; in tones, harshness ; in noises, rustle or rattle ; in touch,
roughness. If the rate of succession is still further reduced, we
get a true temporal discontinuity, with the distinction of before
and after; this appears, in rough average, for sight at an objective
interval of ^^g- or -^-^ sec. (dark and light adaptation), for touch at
^^ sec, and for hearing at, perhaps, ^\-^ sec. (noise). It is clear,
therefore, that a conscious present of no more than 0.6 sec. still
gives full scope for localisation.
While, however, these results are important, as showing that the
conscious present is always a time-field, and not a time-point, it is
to the longer presents of everyday life that we must look for the
cues to temporal localisation. The two or three hours of steady
attention (p. 293), the whole hour during which a young child
342 Temporal Perceptions
amuses itself with a new toy, the evening devoted to a cram
before examination, — periods of this sort, with their diversity of
quahtative content and their succession of focal experiences, rep-
resent the time-fields within which events are dated.
Tetnporal Discrimination. — A great deal of work has been
done upon the comparison of durations. Unfortunately, it was
supposed, at the outset, that the simplest time-experience is the
interval of ' empty ' time between two limiting stimuh. In fact,
of course, there is no such thing as an empty mental time ; the
interval enclosed between two clicks or taps is the duration of
something, e.g., of some organic sensation ; and the simplest
time-experience is the ' filled ' time, the duration of a tone or
colour or pressure, of some overt and obvious mental content.
It has been found, accordingly, that the comparison of intervals is
a complicated matter ; it is differently grounded for intervals up
to about 0.6 sec, for intervals between this and 4 or 5 sec,
and for intervals of still longer duration. Short intervals are com-
pared, not as spaces of time between limiting stimuli, but by
reference to the stimuli themselves ; every stimulus has its own
duration, its time-halo ; and the comparison is based upon the
total temporal impression made by the two pairs of stimuh.
Long intervals, again, are compared indirectly, by the help of
secondary criteria, and principally by reference to the number
of mental processes that run their course within the two stimulus-
periods. The middle intervals, from 0.5 to 5 sec, are compared
as durations, as spaces of time. Since the differential hmen is
approximately constant, so that the comparison of the intervals
falls under Weber's Law, it is natural to suppose that the internal
sensations which here carry the time are qualitatively constant and
intensively variable ; and introspection points to sensations of
strain, whether due to the expectant attitude of the whole body
or, more particularly, to the adjustment of the sense-organ to
which the limiting stimuli are addressed, as the vehicles of the
temporal judgment.
Temporal Illusions. — We are subject to gross illusion regarding
the rate at which time passes (p. 7). A period that is rich in ex-
periences is short in the Hving, and long in memory ; as it passes,
§ 93- The Sensory Attribute of Dicration 343
we have no time to attend to its time-value ; when it has passed,
we judge it to have been long by the number of experiences it
embraced. There are moments, again, when time appears to stand
still ; and there are also, if the author may trust his own observation,
occasions when time appears to be running backward : when, e.g.,
one is retracing, in profound absorption, the steps that have led
to a conclusion which one desires to explicate or to justify. These
are everyday illusions, due to a great complication of conditions.
But illusions are found, also, under the stricter control of the
laboratory.
Thus, within certain limits, an interval that is filled by a discon-
tinuous series of sensations appears longer than an empty interval of
the same objective length (cf. p. 336, line 2). Or again : when we
listen to a rapid series of taps or clicks, we find ourselves forced, as
it were, to accent some more strongly than others ; the sounds fall
into a rhythm. Suppose that we have three clicks, i.e., two inter-
vals. If we accent the first click, the first interval appears the
longer ; if the second, the second ; if the third, the first again : the
effect of accent is to lengthen the following and to shorten the
preceding interval. If the series of clicks really increases in loud-
ness, the intervals seem to grow shorter ; if it decreases, they grow
longer.
The Index of Change. — There are two great groups of temporal
perceptions, the continuative and the discrete. Typical of the
latter is the perception of rhythm, which we discuss in the follow-
ing Section ; typical of the former is the perception of change,
which appears in three distinguishable modes. We may perceive
change, first, by the aid of secondary criteria, and especially by
kinaesthesis (inhibition of breathing, the swell of inspiration, eye-
movement, etc.). We may perceive it, secondly, as a specific
pattern of the connection of elementary processes, a temporal over-
lapping of qualities or intensities within the conscious present.
And we may perceive it, thirdly, by what has been termed the in-
dex of change : a peculiar modification of quality or intensity such
that the attribute under observation shows confusedly, not as a
point upon the sensory scale, but rather as something that can be
referred only to a region or a section of the scale. The physio-
344 Temporal Perceptions
logical basis of this modification is to be sought in the overlapping
of the excitatory processes in sense-organ and nervous system.
§ 94. The Perception of Rhythm. — When we walk or run,
we have a fairly regular alternation of stronger and weaker
sensory complexes. The legs are pendulums, swinging
from their point of attachment to the trunk ; but the motor
functions of the body are ordinarily asymmetrical, — we are
right- or left-handed, as we say ; and the superior muscular
development of the one (usually the right) side means that,
in the course of the double pace, the one foot comes down
more energetically and swings more quickly than the other.
The accent thus introduced into movements of locomotion
is reinforced by the sympathetic swing and jerk of the arms.
In the movements of walking, of dancing, of speech and
song, we have a tactual basis for the perception of rhythm.
It is probable that this basis is primary, though we are now
inclined to think of the rhythmical perception rather as
auditory than as kinaesthetic ; speech and song imply hear-
ing, and even the rhythm of marching and dancing may
come to consciousness most emphatically in auditory terms.
Sounds are, indeed, the better material for the perception
of rhythm : for the limbs, being fixed to the trunk, can give
only the most rudimentary, duple rhythms, while sounds,
whose stimuli are free, can be divided into groups of any
perceivable complexity. Nevertheless, the kinaesthetic
component persists. We mark time, beat time, as we listen
to music, by free movements of head or foot or hand ; and
we manage, by spacing or reversing the movements, to
imitate in kinaesthesis the compHcated rhythms of audition.
It is a moot point whether the perception of rhythm may appear
in complete independence of kinaesthesis. In the case of speech
and song we have, of course, not only the muscular adjustments of
§ 94- "^^^^ Perception of Rhythm 345
the larynx, but also the rhythmical play of the respiratory muscles.
The author was formerly disposed to attribute a separate rhythmi-
cal perception to hearing, but recent observation has convinced
him of the existence of kinaesthetic sensations due to the contrac-
tion of the tensor tytnpani of the middle ear. It is true that
change of pitch may determine the character of an auditory
rhythm. But pitch may here be regarded as a substitute for, or
as itself the equivalent of, intensity : the former, if it arouses asso-
ciations which, referred to their ultimate ground, are of an inten-
sive character ; the latter, if strain sensations are evoked both by
intensity and by quality of the sound stimulus.
Auditory rhythm may, in fact, be obtained by subjective accen-
tuation (pp. 289 f., 343), and by variation of the duration, tem-
poral separation, intensity, and pitch of the stimuli employed.
Subjective accent is a matter of the insistence (p. 55) of certain
elements in the stimulus complex ; it is favoured by the observer's
general attitude, and is oftentimes supported by large organic
fluctuations (respiration, swing of the whole trunk). The primi-
tive form or material of rhythm — for the level from which the
perception of rhythm may be dated is still in dispute — is a dis-
crete series of equally intensive impressions, whose members are
separated by equal pauses : one finds it, e.g., in the syllabic reading
of young children. Out of this grows, first the duple rhythm,
probably in the order spondee, trochee, iambus, though the prior-
ity of the trochee is disputed ; and then the triple rhythm, probably
in the order dactyl, anapaest, amphibrach. The hmits of rhythmi-
cal complexity have beeri discussed above, pp. 289 f.
The perception of rhythm may be aroused by visual impressions,
whether by simple series of discrete stimuli, presented under lab-
oratory conditions, or by the sight of rafters on a corridor ceiling,
or of the recurring ornaments on a facade. In the author's
opinion, this rhythm is always kinaesthetic, based upon eye-
movement, upon slight movements which tick off the successive
impressions, or upon some other form of intermittent kinaesthesis.
Even those writers who believe in a purely visual rhythm acknowl-
edge that kinaesthetic associates are almost invariably present, and
are exceedingly difficult to suppress.
346 Temporal Perceptions
§ 95. Theories of Time-Perception. — In principle, we
have in the case of time the same divergence of psycho-
logical theory that we noted in that of space. There are
psychologists who derive, or generate, time from the in-
timate connection of processes that are themselves consid-
ered to be timeless. There are also psychologists who
make the two great temporal characters, duration and order,
ultimate and irreducible. We have ourselves followed the
lines laid down for a theory of space-perception ; we have
assumed that duration is an attribute of all sensations, and
have regarded temporal localisation as a corollary of
duration.
As illustrative of the genetic theories, we may take Wundt's ac-
count of the origin of temporal ideas. " A sensation thought of
by itself," Wundt declares, " can no more have temporal than it
could have spatial attributes." The fundamental datum, in time
as in space, is order, arrangement ; duration, like extent, is for
Wundt a secondary formation. Sensations are ordered in time
by the help of temporal signs, just as they are ordered in space
by the help of local signs. The temporal signs are fusions of af-
fective with sensory elements : the affective qualities of tension
and relaxation (p. 250) blend with the intensively graded series
of kinaesthetic (especially strain) sensations. The time-percep-
tion is thus " a fusion of the two kinds of temporal signs [the inten-
sive and the quaUtative] with each other and with the objective sen-
sations arranged in the temporal form." The fixation-point of time,
the ' now ' of consciousness, is determined primarily by affective
processes ; since these change, the fixation-point is constantly
changing ; and this change of fixation-point is what we mean when
we speak of the flow of time.
As illustrative of the nativistic theories, we may take Ebbinghaus'
account of temporal perceptions. Sensations, according to Ebbing-
haus, have two classes of attributes : the individual or specific, and
the general or common. In the latter class he includes space
References for Further Reading 347
and time (extent and duration), movement and change, likeness
and difference, unity and multiplicity. Rhythm falls under the
heading of unity and multiplicity. Temporal order, succession, is
merely discreteness of duration, the alternation of 'duration ' and
'interval' ; and the distinction of duration and interval is itself
merely a matter of direction of attention ; we call the temporal
attribute ' duration ' when we are attending to some attribute of the
durable process, and ' interval ' when we are indifferent to this
process, but attentive to its limiting impressions.
Wundt's theory is open to the objection urged against his the-
ory of space. The blending of affective process with sensation
means, elsewhere in the mental hfe, not time but feeling; and we
cannot understand how, in this particular case, the new product
should arise. Ebbinghaus' category of general or common sense-
attributes seems to the author to take too much for granted ; we
are bound to push our analysis as far as it will go. Ebbinghaus
appears, as regards both temporal localisation and the percep-
tion of rhythm, to halt before he has reached the psychological
goal.
All theories of time recognise the importance of secondary
criteria, whether of duration or of localisation. Length of time
may be estimated by number and variety of experiences, by our
boredom, by the strain of expectation, by reference to a familiar
time-standard ; the date of an experience may be settled by range
and particularity of memory, by reference to some salient event,
by verbal association, and so on. These things have, however,
nothing to do with the specific perception of time.
References for Further Reading
§§ 93-95- Wundt, Physiol. Psychologic, iii., 1903, i ff. ; Ebbinghaus,
Psychologic, i., 1905, 432 ff., 480 ff., 504 ff. A brief account of Wundt's
theory will be found in his Outlines, tr. 1907, 170 ff.
A bibliography of the work done upon temporal discrimination is
given in the author's Experijuental Psychology, II., ii., 1905, 393 ff.
For the perception of rhythm, see ibid., I., ii., 1901, 337 ff- ; R-
MacDougall, The Strtictiire of Simple Rhythm Forms, in Harvard
Ps_ychological Studies, i., 1903, 309 ff. (Psychological Review Monograph
348 Temporal Perceptions
Supplement, 17); C. R. Squire, A Genetic Study of Rhythm, in Ameri-
ca7t Jourftal of Psychology, xii., 1901, 492 flF. ; K. Koffka, Experimental-
Untersuchungen zur Lehre vom Rhythnnis, in Zeits. f. Psychol., lii.,
1909, 1 ff. For the mental present, see L. W. Stern, Psychische Priisenz-
zeit, ibid., xiii., 1897, 325 ff. ; for the perception of change, the same
author's Psychologic der Verdnderungsauffassung, 1898.
QUALITATIVE PERCEPTIONS
§ 96. Qualitative Perceptions. — We have had instances
of qualitative perception in the musical or compound tone
(§ 25), in the various taste-blends (§ 34), in the touch-blends
(§ 50), and in certain organic complexes, such as nausea
and hunger (p. 188). It is characteristic of all these ex-
periences, first, that the component qualities blend, fuse,
run together, so that the perception appears simple, or at
least unitary ; but, secondly, that the components can still
be identified, so that the perception may be analysed, under
rigorous scrutiny, into a number of elementary processes.
It follows from the sensory blending that the qualitative
perception may become focal in consciousness as a whole.
A recent writer has declared that the ' texture ' of qualita-
tive perception, due to the 'massing' of its sensory ele-
ments, — it is difficult to find words to indicate precisely
what is meant, — may, in certain spheres, be as important
in creating apparent qualitative differences as is the quality
of the single sensation ; ^ and James, in a well-known pas-
sage, has argued that the taste of lemonade comes to us,
at first, as a simple quahty.^ This fact, then, is important :
that we may attend to the perception as a whole, and that
the blending may be so complete as to give us the illusion
of quaHtative simplicity. But the other fact, that system-
atic observation always reveals the complexity of the
perception, is of no less importance. We may attend
separately to the separate components ; and, if we take
1 E. Murray, Organic Sensation, in American Journal of Psychology, xx.,
1909, 446. "^ W. James, Principles of Psychology, ii,, 1890, 2.
349
350 Qualitative Perceptions
this attitude, the perception breaks up into a number ot
really simple, sensory qualities. Thus, an observer who
has never tasted limes will, if he is versed in introspection,
distinguish the cold, the peculiar aroma, and the sweet,
sour and bitter of limade, while his non-psychological host,
who has put the ingredients together, will regard the
' taste ' as a simple and single experience. The writer just
quoted remarks, in another connection, that " many of the
differences regarded at first sight as ultimate resolve them-
selves, on analysis, into differences in the consolidation and
coordination of the component sensations," and adds that
" the dissection here carried out is not purely hypothetical, but
was effected in almost every case directly by introspection." ^
James warns us here against two erroneous inferences. The
one is " that because we gradually learn to analyse so many qual-
ities we ought to conclude that there are no really indecomposable
feelings ^ in the mind." We have spoken of this matter above, pp.
50 f. The other is " that because the processes that produce our
sensations are multiple, the sensations regarded as subjective facts
must also be compound." We referred to this source of error,
the stimulus-error, on p. 218. In some cases, the stimulus-error
is ruled out by the observer's ignorance of the conditions under
which the mental process laid before him for analysis is produced ;
in general, however, it can be overcome only by long training. A
third inference, which is certainly as dangerous as the two men-
tioned, is this : that the psychological elements, just because they
are elementary, are chronologically the first things in mind, so
that perceptions grow, are formed, by the interconnection of orig-
inally separate sensations. The elements are, as we have seen
(pp. 37 f.), the results of analysis; the perceptions are the original
^ E. Murray, A Qualitative Analysis of Tickling: its Relation to Cutaneous
and Organic Sensation, in American Journal of Psycliology, xix., 1908, 315 ff.
'^'Feelings' here mean 'mental processes'; 'sensations,' in the next
quoted sentence, mean any cognitive processes that give us bare acquaintance
with a fact.
§ 97* Tonal Fusions
351
things, and the sensations are found in them by observation ; per-
ceptions are given us, and we discover that they are analysable.
Misunderstanding here is fatal to the student of psychology, for it
means misapprehension of the central psychological problem.
§ 97. Tonal Fusions. — The classical instance of the
qualitative perception is the tonal fusion. We saw in § 25
that the musical tone is a complex of fundamental and
overtones, and that its wave-train may be analysed into
simple waves whose vibration-ratios are i : 2, 3, 4, etc. In
other words, the musical tone is a tonal fusion. It is, how-
ever, a fusion of a complicated kind ; for the overtones
vary in intensity, and are present (p. 102) in some numbers.
We get tonal fusion at its purest by sounding together
two simple tones at the same intensity. Under these con-
ditions, we find that there are degrees of fusion. The fol-
lowing Table shows the observed facts.
Degree of Fusion
Illustrative
Tones
Vibration-ratio
OF Stimuli
0)
Octave .....
C,C^
I
2
(2)
Fifth
c,g
2
3
(3)
Fourth
c,f
3
4
(4)
Major third
c, e
4
5
Minor third
c,e t?
5
6
Major sixth
c, a
3
5
Minor sixth
c,a'rf
5
8
(5)
Subminor fifth .
^,S 9 -
5
7
Subminor seventh
c,b \^ -
4
7
(6)
Major second .
c, d
8
9
Minor second .
c,d\;
15
16
Major seventh .
c,b
8
15
Minor seventh .
c,b\;
9
16
These results, obtained both with simple and with musical
tones, have been confirmed both by the individual judg-
352 Qualitative Perceptions
ments of trained observers and by the collective observations
of untrained persons. They mean that the tones of the
octave, when all secondary criteria have been ruled out,
are heard as a blend, whose unitariness is nearly akin to
the simplicity of a tonal sensation, while the tones, e.g.^ of
the major seventh fall apart as they are heard. Recogni-
tion of the component tones makes no difference to the
degree of fusion ; we may know that an octave is sounding,
and may be able to identify the tones that compose it ; but
so long as we are listening to the octave, so long as the
fusion itself is focal, we still hear the unitary tone-blend.
The phenomena of tonal fusion have been studied in great de-
tail, — with assemblages of more than two tones, with varying in-
tensities of the components, with distribution of the stimuli to
the two ears, in intervals beyond the octave, in mistuned musical
intervals. For our purposes, however, it is unnecessary to go fur-
ther. The essential thing is to grasp the twofold character of
the fusion : its relative unitariness, and its recognisable complexity.
The unitariness is given, sensibly, as we hear it ; analysis leaves
it as unitary as it was before. Yet the unitariness is never that
of a chemical transformation ; analysis, for the normal ear and
after practice, is always possible.
§ 98. Theories of Qualitative Perception. — When we are
looking for the physiological conditions of extent and
duration, our problem is to discover some property of the
sense-organs that can bring them into correspondence
with the spatial and temporal aspects of stimuli. Physical
objects lie in physical space ; physical events occur in
physical time. Hence the explanation of extent and dura-
tion is of the same general kind as the explanation of
quality and intensity ; the various aspects of the stimulus
must be correlated with certain modes of sensory excita-
tion. Our present problem is of a different kind. We
§ 98. Theories of Qualitative Perception 353
have to discover the physiological conditions both of the
unitariness of the qualitative perception and of the possi-
bility of its analysis. We begin with tonal fusion.
Stumpf, to whom we are chiefly indebted for our know-
ledge of the facts of tonal fusion, thinks that analysis is
conditioned by peripheral, fusion by central factors ; the
ear analyses, if we may so phrase it, and the brain blends.
He ascribes the blending to a specific synergy of the nerve-
centres, to a determinate mode of cooperation between
the nervous structures affected by the tonal excitations.
In the present state of brain physiology, this theory, as
Stumpf admits, is little better than a form of words ; it
simply warns us that v;e shall fail to find in the ear a
mechanism for the appearance of fusion. Ebbinghaus,
on the other hand, believes that fusion can be explained in
terms of the peripheral mechanism ; the Helmholtz theory
is adequate both to analysis and to blending.
We know that, according to the Helmholtz theory (§ 26), the
ear is an analyser : let us see how the theory accounts for fusioa
We may begin with the simplest case, that of the octave. Sup-
pose that two tones, whose pitch-numbers are 300 and 600 re-
spectively, are sounding together. They will set into vibration
the basilar fibres whose normal vibration-rates are 300 and 600 in
the I sec. But they will also, Ebbinghaus says, set in vibration
the harmonic undertone fibres ; nodes will be formed, and the
fractional parts of the undertone fibres will take on the rhythm of
the primaries. Thus,
the 300-stimulus causes the fol- the 6oo-stimulus causes the fol-
lowing fibres to vibrate at the lowing fibres to vibrate at the
rates shown : rates shown :
300 X I 600 X I
150 X 2 300 X 2
100 X 3 200 X 3
75 X 4 150 X 4
2A
354 Qualitative Perceptions
and so on. It is clear that the 300-fibre is asked to vibrate both
as a whole (X i) and in halves ( X 2), the 150-fibre both in halves
and in quarters. The fibre takes up the easier, that is, the slower
vibration, and ignores the other, so that the higher tone, that of
600, loses some of its body ; the lower tone steals from it. Con-
sequently, the upper tone becomes a mere shadowy parasite of the
lower tone, and we have the fusion of the octave. It is matter of
observation that in duple fusions the lower tone carries or domi-
nates the fusion.
Now consider the tones 300 and 480, a minor sixth. The
fibres stimulated will be
300 XI 480 X I
150 X 2 240 X 2
100 X 3 160 X 3
75 X 4 120 X 4
60 X 5 96 X 5
and so on. Here there is no identity of fibres in the two columns ;
but 150 stands near to 160, and 100 to 120. Since the basilar
membrane vibrates, not in single fibres, but in narrow strips (p.
Ill), the 160- and 120-fibres will be hampered in their vibration.
The lower tone again steals from the upper, though less cleanly
and to a less extent than in the instance of the octave.
It should be added that Ebbinghaus does not deny the possi-
bility of a central factor in fusion ; he is concerned only to show
that the peripheral mechanism affords a plausible explanation.
There is, however, one point of observation upon which he and
Stumpf are sharply at variance. Stumpf declares that fusion re-
mains the same, whether the tones are heard under the ordinary
conditions of binaural hearing, or are heard separately by the two
ears, or are represented in imagination ; and it would be curious,
he says, if in the first of these cases the fusion should be a pe-
ripheral, and in the others a central matter. Ebbinghaus main-
tains that, if very weak and fairly low tones, say, of 400 and 600
vs., are heard binaurally, the higher tone is practically lost in the
lower ; whereas, if the tones are carried separately to the two ears,
they are heard " with perfect clearness and distinctness side by
side."
Referejices for Further Reading 355
Whether Ebbinghaus has made his point is a question
that will be answered differently by different psychologists ;
he has at all events given a theory that is definite in outline
and that appeals to known physical principles. Yet it
seems that qualitative perception in general must be re-
ferred to central, and not to peripheral conditions. Where
the fusion occurs between qualities of separate senses, as
in the taste-blends, this conclusion cannot be escaped.
But even in the case of the touch-blends there is evidence
that the blending depends, not upon peripheral irradiation,
but upon processes within the nervous system. What
these processes are, and how it is possible that now the
total perception and now its sensory constituents may be-
come focal in consciousness, we do not know.
References for Further Reading
^§ 96-98. C. Stumpf, Tonpsycliologie, ii., 1890, 127 ff., 184 fF. ; H.
Ebbinghaus, Psychologies i., 1905, 318 f., 344 ff. Wundt gives a psy-
chological theory of fusion in the Physiol. Psychol.., ii., 1910, 116 ff.,
430 ff-
COMPOSITE PERCEPTIONS
§ 99. Simple and Composite Perceptions. — The percep-
tions that we have so far discussed may be termed simple
perceptions, since they rest upon a single sensory basis,
upon the sense-attribute of extent or duration, or upon the
concurrence of sensory qualities. There are also various
types of composite perception. Thus, the perception of a
movement in the field of vision or of touch is both temporal
and spatial; the movement has duration, and it has at the
same time extension (spatial magnitude) and direction.
The perception of melody is both qualitative and temporal.
The perception of a thing, an object, is qualitative and
spatial ; the perception of a scene, a situation, an event, is
qualitative, spatial and temporal.
It is not necessary to take up all these composite percep-
tions in detail ; for the most part, their analysis follows at
once from that of the simple perceptions. We must, how-
ever, say something of the perceptions of movement and of
melody.
§ 100. The Perception of Movement. — We need not dis-
cuss how a moving object is localised, or how we perceive
the magnitude, direction and duration of the movement;
these questions have already been answered. The difficult
thing about movement is its continuity ; and the difficulty
is resolved in the alternative ways, by nativistic and
genetic theories. Some pyschologists regard the specific
experience of movement as ultimate and irreducibb; they
even speak of sensations of movement, not in the familiar
356
§ lOO. The Perception of Movement 357
sense of the sensations aroused by movement of the body
or limbs, but in the literal sense ; they believe that the
moving stimulus arouses a sensation of moving, what we
might call a travel-sensation. Other psychologists find
the sensory basis of continuity in the positive after-image
(p. 68), the persistence of sensation after the cessation of
stimulus. By help of this after-image, they say, we are
able, within the mental present, to see or feel a stimulus
as extended over the whole space between the point which
it has just left and the point to which it has just come ; the
tailing-off of the after-image, its gradual loss of intensity,
forbids us to perceive this extension as a spatial extent
pure and simple ; and the recognition of the moving object
as less extended than its path, and as identical at all points
of its course, clinches the perception of movement. The
author inclines to accept the genetic view, though there
are certain observations which it has, so far, failed to
explain.
A good deal of work has been done upon the quantitative as-
pects of the perception of movement, — the minimal and maximal
rates at which movement may be perceived, the differential Hmen
of rate, and so on. We notice only two points. The first, which
indicates the insistent character of the moving stimulus (p. 269),
has to do with the extensive limen of movement. In direct vision
a moving stimulus, to be perceived as moving, must traverse a dis-
tance sensibly equal to that which permits of the local distinction
of two stationary points : the limen of spatial duality and the ex-
tensive limen of movement are practically identical. But in in-
direct vision, and in the cutaneous space-field, the stimulus is
perceived as moving when it has traversed only about a quarter
of the distance required for the perception of duality. It is
clear that, as we said above (p. 271), movement makes a very
special appeal to the organism. The second point is that the
358 Composite Perceptions
discrimination of rates of visual movement is, within certain limitSj
subject to Weber's Law ; it seems, then, that kinaesthetic sensa-
tions play the same part here that they play in the discrimination
of the moderate time-intervals (§ 93).
On the side of extent, the perception of movement is simply a
mode of the perception of spatial magnitude. It may be worth
while to remark — though the fact is implied in previous discus-
sions — that estimation in terms of eye-movement is very un-
certain, unless there is somewhere in the field of vision a fixed
point of reference. Movements of the eyes, to and fro, are con-
tinually going on, and are rarely remarked.
Illusions of Movement. — We can, again, notice only a few
typical illusions. If a stimulus moves over the skin at uniform rate,
we take the movement to be quicker where localisation is more
accurate, slower where it is less accurate (cf. p. 326). Illusions of
visual movement are very frequent, and are due to a great variety
of conditions. It is a general rule, e^g., that a fixated object is
seen at rest. Hence, if we fixate a tree from the window of a
moving train, the tree itself appears to standstill, while the objects
on this side of it move backwards, and those beyond it move with
the train forwards. Yet the moon, seen between moving clouds,
seems to move, and the clouds seem to stand still ! Some other
principle is evidently at work : possibly the principle that small
objects are more likely to move than large.
The Synthesis of Movement. — The perception of movement may
be synthetised by means of the stroboscope, in which discrete
phases of some objective movement are thrown in rapid succes-
sion upon the retina : the instrument is familiar as a toy, and
is popularly known as the zootrope. The stroboscopic effect has
usually been referred to the persistence of sensation in the pos-
itive after-image. But the cylinder may be turned so slowly that
the bridging of the gaps by after-images is out of the question, and
the perception of movement still continues. It follows that
ci?n5=cious predisposition (cortical set) is of great importance for
the perception of movement, — a fact which seriously complicates
the problem set us bv certain movement-illusions.
In the stroboscope, ou/- vision of the pictures is periodically
§ 100. The Perception of Movement
359
interrupted by the solid parts
of the cyUnder-wall, between
the sHts ; if it were not for
this interruption, the pictures
and their background would
run together into a meaning-
less blur. For the same
reason, the photographic rib-
bon of the kinematograph, or
moving-picture machine, is
passed before the lens of the
projection lantern not con-
tinuously, but by jerks ; every
picture is allowed to remain
stationary for a moment before
Fig. 59. James' Aitificial Waterfall.
— VV. James, Mind, O. S. xii., 1887,
517; Principles of Psychology, ii.,
1890, 245.
Very striking after-images may be
obtained bv the slow rotation, on the
colour-mixer, of a white disc upon
which has been painted in black an
Archimedean spiral. — E. Mach,
Grundlinien d. Lehre von d. Bezve-
gungsempfindungen, 1875, 59.
Fig. 58. B. Bourdon, La perception visit-
elle de I'espace, 1902, 194.
it is displaced by the next succeed-
ing picture.
T]ie Effect of Conscious Predis-
position. — If two like objects ap-
pear in succession, at different
points in space, under conditions
which do not preclude the idea
of movement, we almost inevitably
perceive the movement of a single
object. Figure 58 represents a
white disc, upon which a series of
similar figures A, B have been
painted in black ; before the disc
stands a screen with a small win-
dow for observation. Let the disc
rotate, in the direction of the ar-
row, at such a speed that an in-
terval of some quarter-second
elapses between the appearances
of two nfc,ghbouring figures. As
the figure is drawn, A has already
passed the window, and B is com-
ing into view. But B does not
360 Composite Perceptions
rise from below ; at the moment indicated, the observer has the
distinct perception of an abrupt descent of A. The succession
A-B is perceived as the movement of a single A.
After-images of Movement . — If we look for a while at the water
over the side of a moving vessel, or gaze at a waterfall, or keep
our eyes upon the moving roll in a piano-player, and then turn to
the planks of the deck, or the banks of the stream, or the name-
plate on the cover of the instrument, we get the perception of a
reversed movement, a sort of negative after-image of the original.
This after-effect cannot be referred to involuntary movements of
the eyes, since it appears only at that part of the field which was
occupied by the stimulus. The most plausible explanation, on a
genetic theory, is this. The moving object leaves in the eyes a
mass of shifting and fading after-images, which, if seen for them-
selves, would simply continue the perception of movement in the
original direction. Their qualitative character is, however, merged
and lost in the qualities of the field upon which they are projected.
Since, nevertheless, they still sufifice to give a cue to the percep-
tion of movement, their passage over the field must arouse the
illusion that this is itself in motion, and in the opposite direction.
The explanation is not altogether satisfactory, and it must be con-
fessed that, in this matter, a nativistic theory of the perception of
movement has the advantage.
§ loi. The Perception of Melody. — As movement is both
temporal and spatial, so melody is both temporal and
qualitative. It presupposes rhythm ; and it presupposes the
formation of a musical scale, and the classification of the
intervals of this scale as consonant and dissonant.
Rhythm we have already discussed. The conditions that
led to the discovery and the selection of melodic intervals
are still obscure; Stumpf refers melody to the fact of
fusion, while Wundt distinguishes a number of factors,
chief among which is what he terms the direct relationship
of the compound tones.
§ lOi. The Perception of Melody 361
According to Stumpf, consonance depends on fusion, and de-
gree of consonance upon degree of fusion. And fusion is operative
in the case of successive, as it is in that of simultaneous, tones ; the
second tone fuses with the image (§61) of the first, or, if both
tones have ceased, the image of the one fuses with the image of
the other. Homophonic and polyphonic music, melody and har-
mony, thus have their common root in tonal fusion.
Here, however, an objection arises. Was not primitive music
homophonic? And could the hearing of successive tones bring
the differences of fusion- degree so clearly to consciousness that a
musical scale should result? Stumpf replies that primitive music
was not wholly homophonic. Men and women, or men and
boys, chanted together, and the difference of register would give
the intervals, at any rate, of the octave and the fifth ; untrained
singers, who think that they are singing in unison, will sing, ac-
cording to the compass of their voices, in unison, in octaves, or in
fifths. Moreover, musical instruments are a very early invention ;
and the fusion-degree of the fourth, the thirds, etc., occurring by
chance, might strike the fancy of the primitive musician, and so the
intervals might be fixed and employed. Finally, the addition of a
drone-bass, vocal or instrumental, would help to keep the singer
within certain tonal limits. — It may be added that, while we are ac-
customed to think of a scale as beginning in the bass and contin-
uing upwards to the treble, primitive scales, at least in very many
instances, run from treble to bass. The earliest melody was
probably somewhat like our recitative ; and the voice naturally
falls at the end of a sentence. Now the descending fourth is the
ordinary drop of the voice in speaking, as the ascending fifth is its
ordinary rise in questioning. It seems, then, that the interval of
the fourth may have been fixed, in primitive music, as early as the
octave and the fifth, but fixed in the descending direction.
According to Wundt, consonance derives from four principal
sources, two of which are metric and two phonic. In the first place,
the most consonant tones are those which, given together, arouse
the fewest difference-tones, — the tones of the octave and the fifth.
These intervals, fixed by group-singing, set the limits within which
the single voice or instrument is to move. Secondly, the ear is
362 Composite P erceptiotis
able, within certain limits, to compare and to equate tonal distances
(cf. p. 209) ; and, as the absolute sensible discrimination is here
constant, the octave is thus bisected into fifth and fourth, the fifth
itself into major and minor thirds. Thirdly, to pass to the phonic
principles, we find that consonance depends upon the direct and
indirect relationship of the compound tones ; that is to say, upon
the number and intensity of their common overtones, and upon the
nearness of their relation to a common fundamental. Fourthly,
consonances are characterised by a peculiar mode of fusion : the
fusion is less intimate than, e.g., in the prime, or the continuative
noise (p. 97) ; it is a 'distinct' fusion, a fusion of discriminate
elements, as contrasted with the ' diffuse ' fusion of the noise ; and
it is a fusion whose dominating tone owes this dominance, not to
any characteristic of its own, but to the concurrence of the three
conditions of consonance which we have already mentioned.
These four factors in the perception of consonance combine,
under different circumstances, in different ways. The succession
of pure tones in a melody depends upon the metric principles and
upon indirect relationship ; the succession of compound tones de-
pends almost entirely upon the phonic principles, and especially
upon direct relationship.' Both in harmony and in melody, con-
sonance is, for Wundt, primary, and tonal fusion only secondary.
A choice between the rival theories is, at the best, very difficult.
The questions involved are, for the most part, beyond the reach of
experiment, while our knowledge of primitive music, as it exists
in the world to-day, is imperfect, and the results so far obtained
have not been systematised. Where experiments are possible,
their outcome is often rendered uncertain by the musical training
of the observers ; aesthetics may cut across psychology. We
shall therefore do well to suspend judgment.
It is natural that, as the scale becomes complex, the rules of
melody become precise ; but these rules, as well as the aflfective
aspects of rhythm and interval, lie beyond our present horizon. The
unit of our modern scale is, of course, the semitone ; and it is
1 Stumpf does not deny the influence of direct relationship upon the primi-
'c? perception of melodv, but he confines it to the intervals of octave and fifth.
References for Fiirther Reading 363
worth noting that this, while it is by no means the least difference
of pitch that the ear can distinguish (p. 98), is the least difference
that can be accurately sung. The larynx is the earliest musical
instrument, and the singing of grace-notes, with a just noticeable
difference of laryngeal adjustment, may be responsible for the final
form of the musical scale.
References for Further Reading
§ 100. B. Bourdon, La perception visuelle de Vespace^ 1902, 176 ff. ;
H. Ebbinghaus, Psychologie, i., 1905, 489 ff . ; W. Wundt, Physiol.
Psychol., ii., 1910, 611 ff.
§ loi. C. H. H. Parry, The Evolution of the Art of Music, 1896;
H. L. F. von Helmhohz, Ofi the Sensations of Tone, 1895, 234 ff. ; C.
Stumpf, Konsonanz unci Dissonans, in Beitr'dge zur Akustik 7ind Mnsik-
wissenschaft, i., 1898, i ff. ; W. Wundt, Physiol. Psychol., ii., 1910,
440 ff . ; iii., 1903, 138. A 'motor' theory of melody is outlined by
W. V. D. Bingham, Studies in Melody, 1910 (Psychological Review
Monograph Supplement, 50) ; here may also be found references to the
work of the most recent investigators of the subject.
THE PSYCHOLOGY OF PERCEPTION
§ I02. Pure and Mixed Perceptions. — Let us assume for
the moment that any perception may be analysed, without
remainder, into a number of sensations. It would still be
true that the mere enumeration of these sensations is not
an adequate account of the perception. For the sensations
which we find, in the particular case, form a group ; they
have been selected, singled out, marked off, from the other
contents of consciousness. Their fewness is due to the
limited range of attention (§ 80), and their present appear-
ance as a group at the conscious focus depends upon con-
ditions which we have already discussed (p. 270). The
grouping itself, the special mode of connection of the sen-
sations, we have tried to explain in the preceding Sections,
The simplest kind of perception, then, — what we may
call the pure perception, — implies the grouping of sensa-
tions under the laws of attention. But it is clear that
perceptions are, as a rule, not made up solely of sensa-
tions ; we see and hear and feel more than is presented to
eye and ear and skin ; the given sensations are supple-
mented by images. Most of our perceptions are mixed per-
ceptions, complexes of sensory and imaginal elements ; and
the life of perception is, far more than one is apt to sup-
pose, a life of imagination.
We may have at any rate an approximation to the pure percep-
tion (of. pp. 50 f.) both in the laboratory and in everyday life.
When, e.g., we are comparing two linear extensions by eye, or
when we are listening to a tonal fusion, with secondary criteria so
364
§ 102. Pure attd Mixed P erceptions 365
far as possible ruled out, consciousness is practically restricted to
the sensation-group. So, if we are unpacking the parts of a new
and complicated instrument, and come upon something the use
of which is not immediately apparent, the few seconds of intent
scrutiny are taken up with a pure perception. The author was
once shown a photograph, which consisted of a circular field
scrawled all over with random and zigzag marks, and was asked
what it was. Here was a pure perception ; there was no supple-
menting by images. Then the suggestion came : Look at the
back ! On the back was a date, and the date was that of a great
earthquake. The perception at once became mixed ; the photo-
graph was a seismogram.
Ordinarily, however, our perceptions come to us as mixed. To
realise how inevitably they are mixed, devote a couple of days to
the following observation : whenever any casual object strikes
your attention, do not be content to pass it by with a hasty identi-
fication, but go up to it and examine it. You will find that the
bit of glass in the grass is really a bit of grey limestone upon which
the sun is shining ; that the twig which caught your eye because
it seemed to move did move — and is a caterpillar ; that the
enamelled bowl in which a careless servant has left the water is
dry and empty. You will, in a word, be amazed to find how little
you ' perceive ' and how much you ' imagine.' We have touched
on this point above (p. 199), and have suggested that the general
reliability of perception may be due, in part, to the different set-
ting in consciousness of sensation and image, in part to an in-
trinsic difference in the conscious stuff of which the two processes
are made. We may now add that, where the image is incorpo-
rated in the perception, it obeys the same laws as sensation, and
that this likeness of behaviour, while in certain cases it favours
illusion, must also on the whole favour an adequate apprehension
of stimuli. It is hardly too much to say that the occurrence of
illusions is a guarantee of general reliability : glass in the grass
does look like that, things that grow on shrubs are twigs, water
left in the bowl would give this appearance. We return to the
matter in § 118.
The images tiiat supplement the pure perception are different in
366 The Psychology of Perception
different m'nds. In general, they seem to be of three principal
sorts: visual, auditory-kinaesthetic (verbal), and kinaesthetic. In
minds of a certain type, all tactual perceptions are visually supple-
mented : a touch upon the skin calls up a mental picture of the
part stimulated (§ 88), or — as when we bump against something
in the dark — a visual picture of the stimulating object. Silent
reading, again, is almost invariably accompanied by internal
speech; very few persons, and these only after special practice,
can read by eye alone, without arousing a train of auditory-
kinaesthetic word-ideas. General kinaesthetic supplements,
derived from our experiences of handling objects, are also exceed-
ingly common : things look heavy gr light, sound heavy or light,
precisely as they look or sound here or there, near or far (§ 91).
The Doctrine of Apperctption. — The two points to which we
have called attention in this Section, the selective grouping of the
sensory constituents of perception, and the supplementing of the
sense-group by images, are the cardinal points of the doctrine of
apperception in the systems of Wundt and Herbart.^ According
to Wundt, " the state which accompanies the clear grasp of any
psychical contentj and is characteiised by a special feeling [the
feehng of activity, a compound of tension and excitement (§ 72 )], we
call attention. The process through which any content is brought to
clear comprehension we call apperception."^ According to Herbart,
"as soon as any considerable number of Jdeas, connected in various
ways, is present to the mind, every ne-rt perception must act as a
stimulus, by which some of the existing ideas are checked, others
heightened and reinforced, and some trains of ideas are disturbed,
others set in motion. But the new perception itself, as soon as its
initial stimulation has worked, is assimilated, in a passive way, to
the older ideas, since these, in virtue of their interconnections, are
much stronger than the single intruder " : " the incoming percep-
1 See especially Ebbinghaus, G>-u>idd'ige der Ps\ Jiologie, ii., 190S, 29 ff.
2 W. Wundt, Outlines of Psychology, tr. 1907, 2.^3. The student should
read the whole of § 15, on Consciousness and Attention. The chapter is by
no means easy, but should be intelligible in the light c.f our own discussion.
3 J. F. Herbart, Lehrbuch zur Psychologic [1S16, 1S34, reprinted in the
S'dmmtliche Werke\, % 39. The translation has been somewhat condensed. —
§ 103. Meaning 367
tion is apperceived by the preexisting ideas, the apperceiving
masses. The doctrine of apperception, in some form more or less
closely resembling that of Wundt or Herbart, figures in many
psychologies. It is a question, however, whether there is any
real gain in the introduction of the term.
§ 103, Meaning. — Perceptions are selected groups of
sensations, in which images are incorporated as an integral
part of the whole process. But that is not all : the essen-
tial thing about them has still to be named : and it is this,
— that perceptions have meaning. No sensation means ;
a sensation simply goes on in various attributive ways,
intensively, clearly, spatially, and so forth. All perceptions
mean ; they go on, also, in various attributive ways ; but
they go on meaningly. What then, psychologically, is
meaning .?
Meaning, psychologically, is always context ; one mental
process is the meaning of another mental process if it is
that other's context. And context, in this sense, is simply
the mental process which accrues to the given process
through the situation in which the organism finds itself.
Originally, the situation is physical, external ; and, origi-
nally, meaning is kinaesthesis ; the organism faces the
situation by some bodily attitude, and the characteristic
sensations which the attitude arouses give meaning to the
process which stands at the conscious focus, are psycho-
logically the meaning of that process. For ourselves, the
situation may be either external or internal, either physical
or mental, either a group of adequate stimuli or a constel-
lation of ideas ; image has now supervened upon sensation,
and meaning can be carried in imaginal terms. For us,
A popular account of the Herbartian psychology is given by J. Adams, The
Herbartian Psychology applied to Education, 1898, ch. iii.
368 The Psychology of Perception
therefore, meaning may be mainly a matter of sensations of
the special senses, or of images, or of kinaesthetic or other
organic sensations, as the nature of the situation demands.
Of all its possible forms, however, two appear to be of
especial importance : kinaesthesis and verbal images. We
are locomotor organisms, and change of bodily attitude is
of constant occurrence in our experience ; so that typical
kinaesthetic patterns become, so to say, ingrained in our
consciousness. And words themselves, let us remember,
were at first bodily attitudes, gestures, kinaesthetic con-
texts : complicated, of course, by sound, but still essentially
akin to the gross bodily attitudes of which we have been
speaking. The fact that words are thus originally con-
textual, and the fact that they nevertheless as sound, and
later as sight, possess and acquire a content-character, —
these facts render language preeminently available as the
vehicle of meaning. The words that we read are both
perception and context of perception ; the auditory-
kinaesthetic idea is the meaning of the visual symbols.
And it is obvious that all sorts of sensory and imaginal
complexes receive their meaning from some mode of verbal
representation : we understand a thing, place a thing, as
soon as we have named it.
Hence, in minds of a certain constitution, it may well be
that all conscious meaning is carried by total kinaesthetic
attitude or by words. As a matter of fact, however, men-
tal constitution is widely varied, and meaning is carried by
all sorts of sensory and imaginal processes.
The gist of this account is that it takes at least two sensations
to make a meaning. If an animal has a sensation of light, and
nothing more, there is no meaning in consciousness. If the sen-
sation of light is accompanied by a strain, it becomes forthwith a
§ 103. Meaning 369
perception of light, with meaning ; it is now * that bright some-
thing ' ; and it owes the ' that something ' to its strain-context.
Simple enough ! — only be clear that the account is not genetic,
but analytic. We have no reason to believe that mind began with
meaningless sensations, and progressed to meaningful perceptions.
On the contrary, we must suppose that mind was meaningful from
the very outset. We find, by our analysis (§ 96), that sensation
does not mean ; and we find, in synthesis, that the context which
accrues from the situation, however simple or however complex
the context may be, makes it mean, is its meaning.
What, then, precisely, is a situation ? The physical or external
situation is the whole external world as an organism, at any given
moment, takes it ; it consists of those stimuli to which the organ-
ism, by virtue of its inherited organisation and its present
disposition, is responsive, — which it selects, unifies, focalises,
supplements, and, if need be, acts upon. The mental or internal
situation is, in like manner, some imaginative or memorial com-
plex which is fitted, under the conditions obtaining in the nervous
system, to dominate consciousness, to maintain itself in the focus
of attention, to serve as the starting-point for further ideas or for
action. To put the definition in a word, a situation is the mean-
ingful experience of a conscious present.
But is meaning always conscious meaning ? Surely not:
meaning may be carried in purely physiological terms. In
rapid reading, the skimming of pages in quick succession ;
in the rendering of a musical composition, without hesita-
tion or reflection, in a particular key ; in shifting from one
language to another as you turn to your right- or left-hand
neighbour at a dinner-table : in these and similar cases
meaning has, time and time again, no discoverable repre-
sentation in consciousness." The course and connection of
ideas may be determined beforehand and from without ; a
word, an expression of face, an inflection of the voice, a
bodily attitude, presses the nervous button, and conscious-
2B
370 The Psychology of Perception
ness is switched, automatically, into new channels. We
find here an illustration of an universal law of mind, of
which we shall have more to say when we come to deal
with Action : the law that all conscious formations, as the
life of the organism proceeds, show like phenomena of rise
and fall, increase and decrease in complexity, expansion
and reduction ; so that, in the extreme case, what was
originally a focal experience may presently lapse altogether.
We learned our French and German with pains and labour ;
the conscious context that gave meaning to words and
sentences was elaborate ; but now all this context has dis-
appeared, and a certain set of the nervous system, itself
not accompanied by consciousness, gives the sounds that fall
upon our ears a French-meaning, or changes us into
German-speakers.
This predetermination of consciousness by influences that, during
the course of consciousness, are not themselves conscious, is a fact
of extreme psychological importance, and the reader should verify
it from his own experience. It has a threefold bearing upon the
psychological system. First, it reminds us that consciousness is a
temporal affair, to be studied in longitudinal as well as in transverse
section. It is part of the direct business of psychology to trace
the fate of meaning from its full and complete conscious represen-
tation, through all the stages of its degeneration, to its final disap-
pearance. Secondly, our psychology is to be explanatory, and our
explanations are to be physiological (§ 9). To explain the way in
which consciousness runs, the definite line that it takes, we must
have recourse to physiological organisation ; and the tracing of the
stages of mental decay helps us to follow and understand the or-
ganising process. Thirdly, if we lose sight of nervous predisposi-
tion, we shall make grave mistakes in our psychological analysis ;
we shall read into mental processes characters that, in fact, they
do not possess. Turn back to the simple instance given on pp.
274 f. Here we must either say that the meaning of the experi-
§ 104- The Form of Combination 371
ment, after the week's work, is carried for the observer in purely
physiological, non-conscious terms ; or we must say that his obser-
vation is untrustworthy, that there is a mental context which he
has overlooked. But if we take this latter alternative, we shall be
constructing mind as the naturalist in the story constructed the
camel ; we shall be inventing, not describing.
§ 104. The Form of Combination. — Our account of the
psychology of perception is now, in the author's view,
complete. It has embraced four principal points. First,
under the general laws of attention and the special laws of
sensory connection, sensations are welded together, con-
solidated, incorporated into a group. Secondly, this group
of sensations is supplemented by images. Thirdly, the
supplemented group has a fringe, a background, a con-
text ; and this context is the psychological equivalent of
its logical meaning. Fourthly, meaning may lapse from
consciousness, and conscious context may be replaced by a
non-conscious nervous set. If we translate this account
into genetic terras, we have, as the earliest form of percep-
tion, some sensory complex in a kinaesthetic setting. Then
comes the invasion of consciousness by images, which mod-
ify both complex and setting, and may, in course of time,
largely replace the sensory elements of the one and actu-
ally displace the other. The images themselves are very
far from stable ; they shrink and decay ; they tend, more
especially, to reduce to a common denominator, to verbal
ideas ; a sort of symbolic shorthand supersedes the earlier
picture-writing of mind. Finally, the central complex may
appear as a mere skeleton of its former self, a mere indica-
tion of its primal complexity, and the setting may not
appear at all ; meaning may be carried in terms of physio-
logical organisation.
372 The Psychology of Perception
There are, however, some psychologists who would not
regard the account as complete. A square, they say, is
more than four linear extensions, sensibly of the same
length, and occupying certain relative positions in the vis-
ual field ; a square is square ; and squareness is a new
character, common to all squares, but not to be explained
by attention, or by the laws of sensory connection, or by
those of imaginal supplementing. A melody, again, is
more than rhythm and consonance and scale ; a melody is
melodic ; we recognise its melodic nature as such ; the
melodic character is something new and unique, common
to all melodies, but not found elsewhere. Hence they find
it necessary to postulate " a form of combination as a dis-
tinct mental element." " The presentation of a form of
synthesis," they argue, "is as distinct from the presenta-
tion of the elements combined, considered apart from their
union, as the presentation of red is distinct from the pres-
entation of green." ^
In the author's judgment, this attitude betrays a confu^
sion of the analytic and the genetic points of view. We
cannot generate the square from lines, or the melody from
rhythm and scale ; but neither is that what we try to do.
The square and the melody are given, as perceptions. Our
psychological task is to analyse these given perceptions, to
discover their elements, and to formulate the laws under
which the elementary processes combine. That done, we
can write, for * square' and 'melody,' 'these and these ele
ments connected in these and these uniform ways,' and
we can go on to search for physiological conditions (§ 9).
We have solved our problem in analytical terms ; we have
not first defined the terms, and then put them together to
1 G. F. Stout, Analytic Psychology, ii., 1909, 48. Cf. i., 1896, ch. iiL
References for Further Reading 373
produce something that was not contained in the definition.
— The author cannot, in his own introspection, identify the
form of combination as a distinct mental element. It is,
however, only right to say that the belief in a new mental
content, or new mental character, peculiar to perception, is
shared by many psychologists of standing.
References for Further Reading
§§ 102-104. On the general topic, see W. James, Principles of
Psychology, i., 1890, ch. xiii. ; ii., chs. xvii., xix. ; H. Ebbinghaus, Psy-
chologies ii., 1908, § 70. On the psychology of meaning, see the author's
Lectures on the Experimental Psychology of the Thoiight-processes, 1 909,
Lect. V. On the form of combination, see I. M. Bentley, The Psy-
chology of Mental Arrangement, in American Journal of Psychology,
xiii., 1902, 269 fF.
ASSOCIATION
§ 105. The Doctrine of Association. — It often happens
that we wish to recall something that we are sure we know,
but that at the moment escapes us. Aristotle, in his tract
On Memory and Reminiscence, suggests a mode of proce-
dure for such cases : we should start out from something
that is similar to the idea we want, or that is its opposite,
or that has been contiguous with it in space or time.^
Aristotle writes as if these ways of arousing memory were
entirely familiar to his readers ; and so, no doubt, they
were ; popular psychology is full of just such maxims (p.
286). Nevertheless, the Aristotelian rules proved to be
immensely important for the future history of psychology.
They were gradually transformed into laws of the associ-
ation of ideas; and the association of ideas itself came
to be the guiding principle of the British school of
empirical psychology. So well did it work, as an in-
strument of psychological analysis and interpretation, that
Hume compared it to the law of gravitation in physics :
"here," he said, "is a kind of attraction which in the
mental world will be found to have as extraordinary effects
as in the natural, and to show itself in as many and as
various forms. "^ All the great names in British psychology,
from Hobbes down to Bain, are connected with this doctrine
of the association of ideas. ^
^ W. A. Hammond, Aristo/Ie's Psyc/iologv, 1902, 2015.
2 D. Hume, A Treatise of Human Nature, [1739] bk. i., pt. 1., § 4.
3 Let the roll be called ! Thomas Hobbes, John Locke (who introduced
the phrase 'association of ideas'), George Berkeley, David Hume, David
Hartley (the founder of modern associationism), Thomas Brown, James Mill
374
§ 105. TJie Doctrine of Association 375
There are, then, four traditional laws of association. An idea
calls up or suggests another idea by similarity, by contrast, by
temporal or spatial contiguity. " A picture naturally leads our
thoughts to the original" (Hume) : here is association by similar-
ity. " The palace and the cottage, the cradle and the grave, the
extremes of indigence and of luxurious splendour, arise, in ready
succession, to the observer of either " (Brown) : here is association
by contrast, " From St. Andrew the mind runneth to St. Peter,
because their names are read together ; from St. Peter to a stone,
for the same cause ; from stone to foundation, because we see
them together" (Hobbes) : here is association by spatial and
temporal coexistence. '' A musician used to any tune will find
that, let it but once begin in his head, the ideas of the several notes
of it will follow one another orderly in his understanding" (Locke) :
here is association by temporal succession.
The tendency has been, however, to reduce these four laws to
two, or even to one. The law of contrast, especially, has been
merged in that of similarity; if things contrast, it is argued, they
must be similar, at least to the extent that they belong to the same
general class ; black calls up white and not sour ; sour calls up
sweet and not black ; so that association by contrast is really associ-
ation by similarity. To this reduction there are two objections.
First, the argument is logical and not psychological ; the interven-
tion of the class-idea is not attested by introspection. And,
secondly, the contrast referred to in the one law is not on a par
with the similarity referred to in the other ; the contrast is, as we
have already seen (pp. 232 f.), an affective opposition, whereas the
similarity is ideational. Nevertheless, we can do away with the
law of contrast. The cases that fall under it are simply cases ir\
which the extremes of our experience meet, cases of contiguity.
Such cases are very common : letters are printed black on white,
(the typical representative of the school), John Stuart Mill, Alexander Bain,
Herbert Spencer (these three no longer pure associationists). References
will be found in the arts. Association (^of ideas) and Associationism, in the
Dictionary of Philosophy and Psychology, i., 1901, 78, 80. All these men are
worthy of study; only let the student beware of the fatal error that, because
they read easily, they are easy reading.
376 Association
the most brilliant lights give the deepest shadows, we are hungry
and we eat, we feel cold and we make haste to get warm, we
come to the palace through streets of mean houses, and so on.
There is no need of a special law of contrast.
Again, coexistence in space means coexistence in time. Hence
there is no need, either, of a special law of association by spatial
contiguity ; temporal contiguity, simultaneous or successive,
covers all the cases. The four laws thus become two, those of
similarity and of temporal contiguity. Efforts have been made to
carry the reduction still further ; we return to the point in § 107.
§ 106. The Idea. — According to the teaching of this
book, an idea differs from a perception only by the fact
that it is made up wholly of images (p. 48). Look across
the room, and you perceive the table ; shut your eyes, ctnd
you ideate the table. The psychology of ideas is, therefore,
so far as this difference allows, the counterpart of the
psychology of perceptions. Ideas are simple or composite ;
they are subject to the law of growth and decay ; they get
t.heir meaning from their context, and the context may
consist of other ideas, or may be carried in physiological
terms.
Now it needs but little reflection to see that these ideas
are not at all the same thing as the ideas of the preceding
Section. The ideas which we ourselves are defining are
fluid, changeable processes, which derive their meaning
from conscious context or from cortical set. The ideas
which are associated, in the traditional doctrine of the
association of ideas, are already meanings : the idea of the
painting's original is the idea which means that original,
the idea of St. Peter is the idea that means St. Peter : or
rather, if one may put it clumsily for the sake of clearness,
the former idea is just the man-/>ainfcd-mQa.mng, and the
latter idea is the St.-Peter-mQa.mng. Meaning here is not
§ io6. The Idea 377
the context of the idea, nor is it an external predetermina-
tion of the consciousness in which the idea occurs ; mean-
ing is idea, idea is meaning. And since meaning is stable
and permanent, since the man-painted is always the same
man, and St. Peter is always that identical St. Peter, the
psychologists of association naturally treated the ideas also
as stable and permanent ; the ideas were bits of meaning,
separate and impenetrable as physical atoms. It is hardly
a caricature if we say that ideas were like beads, strung
on the thread of association, or like steel blocks, held in
certain arrangements by the magnetic force of association.
There are, in fact, two uses of the term * association,' which are
both confused and confusing in the writers of the associationist
school. On the one hand, association is the gentle force of
attraction inherent in an idea, the affinity of idea for idea, the
tendency of one idea to suggest another ; the steel blocks are
magnetised from the outset. On the other hand, association is
the principle of connection among ideas, is that which ties, binds,
conjoins, links, couples idea with idea ; and this something may
be found either in the nature of the mind (the magnet) or in the
nature of the brain (the string for the beads). The last concep-
tion comes very near our own ; ^ but mark the difference ! Per-
ception is, for us, primarily, a group of sensations, — or, better,
perception is such and so-many sensations found uniformly to-
gether in such-and-such ways. Association, then, will also be, for
us, a group of ideas, — or, better, association will be such and so-
many ideas found uniformly together in such-and-such ways.
The explanation of association, like that of perception, must be
1 It is because many of the conceptions of associationism are very like
those of modern psychology, because the terminology is largely the same,
because the writers' attitude is oftentimes, as if in despite of their associa-
tionism, the attitude of modern psychology itself, and because, nevertheless,
the taint of logical construction pervades the whole of their work, — it is for
these reasons that the student must read warily, with all his psychological
wits about him.
378 Association
sought in the nervous system. But the underlying nervous
processes do not cement or string the ideas together ; the ideas
are found together, and the conditions under which they are found
together are nervous. This is the difference.
We shall have much to say, in what follows, of the na-
ture and behaviour of the idea. It is sufficient, just now,
to have indicated its general character as a mental process,
and to have shown how it differs from the idea of asso-
ciationism.
§ 107. The Law of Association. — The traditional laws
of the association of ideas are, after all, not descriptive
formulas, as scientific laws must always be (p. 5), but
attempts at explanation. If we say that the idea of Julius
Caesar calls up the idea of 'Alexander the Great by simi-
larity, we are offering the similarity of the ideas as an
explanation of their concurrence in consciousness ; and
that road leads nowhere (p. 39). Let us try, however, to
get a descriptive formula for the facts which the doctrine
of association aims to explain. We then find this : that,
whenever a sensory or imaginal process occurs in con-
sciousness, there are likely to appear with it (of course, in
imaginal terms) all those sensory and imaginal processes
which occurred together with it in any earher conscious
present. This we may term the law of association.
That is the text : now follows the commentary. Note, first,
that we have confined the sphere of tlie law to sensory and imaginal
processes, to perceptions and ideas. Some psychologists believe
that it should be extended to include the atifective processes. There
is, truly, no question that feelings (in the widest sense, p. 2 28)
play a large part in the associative consciousness ; only, in the
author's opinion, they play this part by virtue of their sensory and
imaginal components, and not in their affective character. How-
§ lo/. The Law of Association 379
ever, so little is known about the psychology of feeling that the
reader will do best to suspend judgment.
Secondly, the law has said nothing about attention. In the
author's opinion, association always implies a high degree of clear-
ness ; the processes that were together in the conscious present
must have been attentively together, if the law is to hold. But,
again, the point is disputed, and the experimental evidence is not
conclusive.
Thirdly, the law must be amplified in the following way. It
is not necessary, for the reinstatement of a previous consciousness,
that one of its terms should literally be repeated, in the sense of
p. 19 ; it is enough that a process appear which is like one or other
of its terms. If I meet my friend to-day, I am at once reminded
of the conversation that we had at our last meeting, a month ago.
But if some one shows me to-day a recent portrait of my friend, the
same thing happens : ' A good picture,' I say; ' I saw him a month
ago, and we had a very interesting talk.' This extension of the
law of association, from psychological identity to psychological
similarity, is clearly seen in young children, who call all the men of
their acquaintance ' papa,' and call every animal — live animal, toy,
or picture — by the first animal-name that they have learned. It
must be accounted for on the hypothesis that tlie nervous conditions
of similar ideas are in part the same, and that, the more alike the
ideas, the more nearly identical are their conditions.
This mention of similarity brings us back to the discussion of
§ 105. Efforts have been made, we said, to reduce the two laws
of contiguity and similarity to one. Now the law of contiguity
can, with a little forcing, be translated into our own general law of
association. Let the translation be made, and the law stands.
What, then, of the law of similarity? This, be it remembered, is
very different from our own amplified or extended lavv of associa-
tion. We say that ideas may be started on the same track from
similar beginnings ; the old law of similarity says that the course of
ideas ends with similars, that mental like attracts like. No doubt
this statements holds, in the rough, of a great many instances of
association : the idea of Julius Caesar does bring in its train the
idea of Alexander the Great ; and we have noted congruity with
380 Association
the present contents of consciousness as one of the determinants
of attention (p. 270). Nevertheless, all cases of similarity prove,
on examination, to involve contiguity. Caesar suggests Alexander,
not — it is true — by way of the class-idea ' great commander,'
but simply because some component of the idea of Caesar has
previously been together, in a conscious present, with that of Alex-
ander. We may, then, if we like, say that all associations reduce
to associations by contiguity, — being careful, in our own thought,
to translate this law into psychological terms. On the whole, how-
ever, it is advisable to drop the traditional laws, and to retain only
the formula of the text; there is a risk in pouring the new wine
into the old bottle.
§ 108. The Experimental Study of Association. — The
ideas of associationism are meanings ; and meanings, from
our point of view, are conscious contexts or nervous deter-
minations of consciousness. Whichever they are, they sadly
complicate enquiry into the conditions of association. We
have a general law ; but we want to know how it comes
about, in the particular case, that this and not that idea
arises on the recurrence of the other, that Caesar suggests
now Alexander and now Napoleon. We want to get to the
bare essentials of the association.
Some twenty-five years ago, Ebbinghaus solved this prob-
lem by the introduction of nonsense syllables. He made
up over 2000 meaningless 'words,' all consisting of a vowel
or diphthongbetween two consonants; the German language
uses these combinations far less than the English. Here,
then, were pure perceptions, sights and sounds that had no
meaning and no associates ; here was material so varied and
yet so simple, so rich and yet so uniform, that experiments
could be made under laboratory conditions, and the results
of one experiment could be compared, directly, with the
results of another. It is not too much to say that the re-
§ io8. The Experimental Study of Association 381
course to nonsense syllables, as means to the study of asso-
elation, marks the most considerable advance, in this chapter
of psychology, since the time of Aristotle.
It must not be supposed that the nonsense syllables work auto-
matically. We are inveterately given to meaning ; and the ob-
server who sits down to learn a series for the first time shows a
terrible ingenuity in reading sense into what by hypothesis is non-
FlG. 60. Apparatus for the Serial Exposure of Nonsense Syllables. The syllables
are printed upon the periphery of a cardboard disc, which is placed in the box to
the right, and are viewed through the radial slit in the lid. The movement of the
disc is governed by the metronome ; as the pendulum swings, and electrical
contact is made between the platinum strips and the mercury pools at the base of
the instrument, the disc turns, with a jerk, just so far as to expose a new syllable.
At the end of the series, the mechanism may be arrested by opening the key to
the left. The two wires at the bottom of the figure are led to a battery. — P. Ransch-
burg, Monatsschr. f. Psyckiatr. u. Neurol., x., 1901, 321.
sense. A recent writer quotes, as a typical set of English nonsense
syllables, the series : leb, rit, mon, yup, kig, des, wer, zara. But
rit suggests writ, mon is Scotch for man, yup suggests yap or yelp,
kig — if you have a cold — is king, wer is obviously were. And
if you know anything of German, leb, des, wer, zam are directly
suggestive of meaning. The series is, very certainly, not the kind
of series for the beginner, who is constantly hunting about for
meaningful connections. Ebbinghaus reports that the syllables
dosch pam feur lot were connected by the meaning das Brot
382 Association
[Fr. pain !] Feuer loscht, the bread puts out fire. Indeed, here,
as in most psychological experiments, the novice is hkely to do
anything rather than what is required of him j he will search for
meanings, stress the position of syllables, mark the rhythm, shift his
imagery (§ 114). There are great individual differences; but, in
general, it is only after a good deal of practice that the observer be-
comes the sheer mechanical associator ; and it is therefore neces-
sary to make a careful choice of material even within the sphere of
the directly meaningless. However, the observer may be trained.
And methods have been worked out, for the study of association
by means of nonsense syllables, that are as rigorous as those em-
ployed for the study of the intensity or quality of sensation.
Nevertheless, we cannot stop short w^ith these nonsense
syllables. The results derived from meaningless material,
while they are essential to our analysis of the more com-
plicated results from words, pictures, etc., must themselves
be scrutinised in the light of the ordinary meaningful as-
sociations of everyday life ; ^ they are fundamental, but
they are also artificial ; until further test, they hold only
for the restricted conditions under which they are obtained.
However, this work of comparison, of mutual control, offers
no special difficulties ; indeed, the rules discovered in the
laboratory have already been applied, with success, to cer-
tain practical problems.
§ 109. Results : the Conditions of Impression. — Suppose
that you read through a list of nonsense syllables, again
and again, until you can recite it without error. The read-
ing will have established a number of associative connections
between the terms of the series. But it has also, plainly,
established the terms themselves. These terms have, as
stimuli, impressed the nervous system, imprinted themselves
on it, stamped it in a determinate way.
1 We return to this part of the subject in § 123 below.
§ 109. Results: The Conditions of Impression 383
The correct recitation depends, then, not only upon as-
sociative connections, but also upon impression. A terra
may be but weakly associated to its preceding term, and
yet, if it has made a strong impression, — if, as we may say
figuratively, its idea is almost ready to appear of itself, —
may be brought to consciousness by the weak associative
tendency; and, conversely, a term may be but weakly im-
pressed upon the nervous system, and yet may be brought
to consciousness by a strong associative tendency. It is
impossible, in experiments of the sort under discussion, to
separate the two factors in the result ; the conditions of
impression are also the conditions of association. We may
say, however, that impression depends upon the length of
the series, the position of the terms within it, the rate of
succession of the terms, their grouping into complex units,
the number and distribution of the readings, the active
participation of the observer, and the mode (total or partial)
of repetition.
Attention, we may remind the reader, is presupposed. Impres-
sion then depends, first, on the length of the series. While 6 or 7
syllables can be recited correctly after a single reading, a larger
number throws the observer into confusion. The first and last
terms of the series have the advantage over the others ; they may.
indeed, be the only terms that can be recited after a single read-
ing of a 12-syllable series. The impression is deepest if the syl-
lables are first presented at a moderate rate (perhaps 2 in the i sec),
and if this rate is slowly increased as the readings proceed. It
is of assistance to introduce a subjective rhythm. Impression
deepens, further, with repetition. The first reading is more im-
portant than any single later reading ; after that, there is for a
while little if any improvement ; then the results take a sudden
step up ; and thenceforward progress is fairly steady until the
limit of the experiment is reached. The distribution of the read-
384 Association
ings in time is also of great importance : thus, it is better to dis-
tribute 24 readings in pairs to 12 days than to take them in fours
on 6 days ; and it is, again, better to do this than to take them in
eights on 3 days.
The same rules hold, with the necessary changes, for meaning-
ful material. While 8 or 9 one-syllable words, and 10 or 12 figures,
can be recited correctly after a single reading, a larger number
brings confusion. We return to this point later (p. 387). The
rate of presentation may be much quicker : in the reading of poetry,
e.g., 140 to 150 iambic measures in the i min. (4 or 5 syllables in
the I sec). The grouping of the material is given, not only by
rhythm, but by the meaning of the successive passages.
There remain the two factors which we have called the active
participation of the observer and the mode of repetition. It is
found that a recitation is far more effective for impression than a
reading. The reason may be, in part, that attention is greater ; in
part, that the auditory and kinaesthetic stimuli reinforce the visual.
It seems to the author, however, that the chief effect of the reci-
tation is to equalise the attentions ; every term in the series must
be brought out sharply and clearly ; the observer discovers his
weaknesses, and has the opportunity to overcome them. Finally,
it is found that connected, meaningful material is most impressive
if it is read as a whole, from end to end, in the successive repeti-
tions, while nonsense syllables and disconnected meaningful ma-
terial (dates of events, words of foreign languages) are best taken
discretely, read over and over a little at a time. —
The nervous modification which we have here named * impres-
sion ' is, clearly, the first term in the series of nervous changes which
condition the process of learning. If we read the list of syllables
again and again until we can recite it correctly, we have learned it.
Learning, however, is a very complex affair, depending upon im-
pression, upon associative tendency, upon the retentiveness of
nerve-substance, and upon cortical set. Hence we have avoided
the use of the word in the present Section.
§110. Results: the Conditions of Associative Tendency. —
Anything that makes for the impression of two stimuli,
§110. Results : Conditions of Associative Tendency 385
during the conscious present, will also serve to establish
an associative tendency between them ; so that the recur-
rence of the one, whether as perception or idea, will be
likely to arouse the idea of the other. The impressing of
our series of syllables has, accordingly, established certain
associative tendencies. The strongest of these, as might
be supposed, is that which leads from term to term in the
order of presentation ; but there is good reason to believe
that every term is, in some measure, connected with every
other term of the series.
We find in the experimental results cases of association, not
only of immediately successive ideas (direct association), but also
of ideas separated, within the conscious present, by other ideas
(remote association) ; this latter is relatively weak, but it is still
definitely discoverable. To put the matter in terms of the alpha-
bet, we find associations, not only of a and b, of b and c, oi y and z,
but also of ^ and d, oiv and z. And, what is more important, we
find that the associative tendencies may work retroactively ; there
are associations of z with y, of z with x, and so forth. The series
of syllables has therefore been impressed, not as an interrupted
series, but as a very complicated meshwork, functionally inter-
connected through all its parts.
There is yet a further complication. The series is impressed
upon a brain which is already the seat of a vast concourse of as-
sociative tendencies ; and the incoming stimuli may thus excite to
full or partial activity some preexisting tendency whose arousal was
neither expected nor intended. The observers not infrequently re-
port, e.g., associations of position, of the place of a syllable in the
series; the cue may be given, according to the circumstances of
the experiment, by a verbal idea of number, by the spatial arrange-
ment of the syllables, by inflection of the voice. Under certain
conditions, the subarousal of such a tendency determines an as-
sociation, while the place-idea does not itself appear in conscious-
ness. Suppose that a is associated to b, a. to y8, and that both
pairs of letters have been associated to the place-ideas first, second.
386 Association
Then, in the given case, the sight of a may suggest the idea of ^
although the observer has not thought of 'first.'
Mediate Association. — Some psychologists believe that an asso-
ciation may be set up, originated, by unconscious (purely physio-
logical) intermediaries. I examine a picture, we will say, which
the artist has signed ; my eyes travel over the signature, but I fail
entirely to remark it. At some later time I am examining another
picture, signed in the same way by the same artist ; again my eyes
travel over the signature, but again I fail to remark it. Neverthe-
less, the second picture suggests the first ; the signature has im-
pressed my brain, although it has not aroused a perception ; the
ideas of the two pictures are connected by this unconscious link.
Here is a case of mediate association.
The question has been put to the trial of experiment, and the
results are mainly negative ; it is, however, so difficult to meet the
conditions of a crucial test, that difference of opinion is natural
and justifiable. In the author's judgment, association requires
attention (p. 379) ; mediate association, of the kind described,
does not occur. The alleged instances may be interpreted as
associations whose conscious mediation (odour, organic sensation)
has been overlooked, or as remote associations, or as associations
due, in the way just described, to the subarousal of associative
tendencies already estabhshed. A fourth possibility will be dis-
cussed later (p. 400).
If, now, a series of nonsense syllables establishes this
complicated network of associative tendencies, a stanza of
poetry or a paragraph of prose must set up excitations of
far greater complexity. And the pattern of the excitations
will vary, according as the meaningful material is familiar,
and therefore throws into play a total cortical disposition,
or is unfamiliar, and therefore starts up only partial and
fragmentary associations. We cannot trace these effects
in detail ; but we have evidence both of the mutual rein-
forcement and of the mutual interference of associative
tendencies.
§ no. Results: Conditions of Associative Tejidency })%y
We have had an instance of interference in the confusion that fol-
lows the first reading of a long series of words or syllables (pp. 383f,).
So long as we are within the range of attention (§ 80), there is no
difficulty. But when we pass beyond it, the law of retroactive
inhibition comes into effect. The associative tendencies need a
certain time to establish themselves, to settle down ; and if this time
is not allowed, but stimulus treads on the heels of stimulus, there
is no impression of a pattern, and no associations are formed. A
recently acquired association may even be abolished — as most of
us know to our cost — by intensive occupation with an entirely
different topic. You have just got to your point, to the phrasing,
the insight, the argument, that will clinch things ; you are dis-
tracted by some irrelevant business ; and when you come back to
your work, the point has gone. So nicely balanced and so easily
disturbed are the associative tendencies, that you may never re-
cover it ; try as you will to reinstate the conditions, you cannot
get the exact pattern back again. The compensation is that the
tendencies, left to themselves, fall into their own patterns. School-
boys, with a keen sense for economy of effort, learn their lessons
only partly overnight, and trust to a hasty review in the morning ;
the associative tendencies work while their owners sleep. Here,
too, is the secret of the practised speech-maker. Knowing that
he has to talk on a certain subject at a certain date, he runs over
his present ideas in ten minutes of concentrated attention, and
drops them ; then, on the appointed day, he finds that the associa-
tive tendencies have prepared his address.
With meaningful material, interference may arise in other ways.
Take the alphabet, again : a is connected with b through the fre-
quent repetition of abc, but is also connected with z by the phrase
'a to 2.' Let a appear in consciousness ; what happens? It
may be promptly followed by d or z; the one of these ideas may,
as we have expressed it, be more nearly ' ready ' than the other.
If the terms of the two associations are complex, the incoming
idea may derive from both of them : a may, so to say, call up an
idea that is partly b and partly z. But, if the <2;-tendency and the
2-tendency are of approximately equal strength, they will cancel
each other, and there will be no association. A question often
388 Association
leaves you dumb, not because you have no answer, but because
you have so many answers that no one of them can force through
to expression.
This sort of interference is known as terminal inhibition, in con-
tradistinction to another kind, which is called initial inhibition.
If a is already connected with b, then it is difficult to connect it
with k ; b gets in the way. You have some particular fault of style,
or you have fallen into the habit of spelling wrongly some particu-
lar word ; you want to correct the fault, to spell aright. But every
time that you are off guard, the mistake recurs; the existing asso-
ciation a-b heads off the desired association a~k. This law, then,
cuts across the law of remote association. The first impression
of the alphabet sets up, it is true, not only the direct association
a~b, but also the remote association a-k. As, however, the alpha-
bet is more and more often repeated, the direct association more
and more strongly inhibits the remote, so that it presently requires
more readings to establish the connection a-k than were needed
for the original connection a-b.
On the other hand, the associative tendencies may reinforce one
another. Association may be convergent ; a whole constellation or
complex of tendencies may work together in the interests of a single
idea, and this complex, as we have repeatedly seen {e.g., p. 274),
need not by any means appear as a whole in consciousness. Chil-
dren who are brought up to speak two languages rarely mix their
words ; as they have begun, so do they continue, a sentence ; the
first utterance has behind it the directive pressure of a multitude of
cooperating tendencies. More than this, association may be at
first divergent, and then convergent. A perception may stir into
activity a number of tendencies, or a number of constellations ;
and these may, in their turn, all converge upon a single idea.
Here we get a glimpse into the physiological basis of conscious
context, of psychological meaning (§ 103). The words of a sen-
tence, the sentences of a paragraph, the paragraphs of a chapter,
the chapters of a book, arouse innumerable tendencies in the
nervous system of the reader. Sometimes a special constellation
gains the upper hand, and the reader is sidetracked by his own
ideas ; in general, the writer has his way, and the divergent ten-
§ III. The Associative Consciousness 389
dencies are continually recombined. However, this is not the
whole story of meaning ; the reader's total attitude is also of great
importance (§141).
§111. The Associative Consciousness. — There are as many
modes or forms of association as there are ways of being
together within a conscious present. What these ways are,
we already know ; they have been outlined in our discussion
of perception. We may say, then, that there are as many
forms of association as there are forms of perception and
idea ; the pattern of the associative conscioussness may be
spatial, temporal, qualitative, or mixed. The pure percep-
tion is itself an association of sensations, and the idea is an
association of images.
But is there no psychological difference between percep-
tion and idea, on the one side, and the association on the
other .'' Not, certainly, in composition : the elementary
processes that analysis reveals are the same in both, —
sensations and images. Not, necessarily, in complexity :
many of the instances of association given in the text-books
are simpler, contain fewer elementary processes, than the
more complicated perceptions. Not, again, in mode of
connection of the elements : the laws governing connec-
tion are the same throughout. And not, necessarily, in
closeness of this connection : the names of familiar things
are as closely bound up with their perceptions as the sensory
elements in the perceptions are bound together. The differ-
ence is, in fact, rather a psychologist's than a psychological
difference. We must build up a psychology by stages, in
orderly fashion ; and it is convenient to distinguish, first,
the bare elements, sensations and images ; next the con-
nection of the bare elements, perceptions and ideas ; and
then, later, the connections of elements that have already
390 Association
been connected, the associations of ideas. If we may use
a figure, which roughly expresses the truth, we can say that
the elements of the perception have never been together
before, while the elements of the association have manifold
habits of connection already upon them.
The doctrine of association has, however, played so im-
portant a part in the history of psychology, and the influence
of tradition is so strong, that many psychologists tend, as if
instinctively, to differentiate the idea from the association of
ideas. The tendency shows itself in two ways : first, in the
overemphasis of successive, as compared with simultaneous
association ; and secondly, in the attempt to classify and
tabulate the various forms of association.
Most students of psychology, if they hear the phrase 'association
of ideas,' think at once of the successive association ; and this, by
its very nature as a train or succession, is more complex and more
variable in its course than is the idea. Yet it is certain that the
simultaneous association is the typical association, and that the
successive association, as illustrated in the books, is of rare occur-
rence, a limiting case of association at large. " In a discourse of
our present civil war," wrote Hobbes in 165 1, "what could seem
more impertinent than to ask, as one did, what was the value of a
Roman penny? Yet the coherence to me was manifest enough.
For the thought of the war introduced the thought of delivering up
the king to his enemies ; the thought of that brought in the thought
of the delivering up of Christ ; and that, again, the thought of the
thirty pence, which was the price of that treason. And thence
easily followed that malicious question." Here, no doubt, Hobbes
has his finger on the coherence, the context. But there is just as
little doubt that the psychology of the situation was widely different
from his conception of it ; there was no simple sequence of thought
upon thought, idea upon idea. Let the reader observe for him-
self!
We shall not here enter upon the question of classification. The
§ III. The Associative Co7isciousness 391
various authors who have drawn up tables of associations have based
their arrangement, ahnost without exception, upon logical principles,
upon the meaning of the associated ideas ; they have referred the
associations to certain logical categories, such as subordination,
coordination, cause and effect, means and end. The results may
be of value for a psychology of individual differences ; they have
no place in a general, descriptive psychology. Moreover, associa-
tions vary with circumstances. It has been found, under experi-
mental conditions, where a stimulus-word is given and the observer
has to reply at once by naming the first word which occurs to him,
that substantives are associated to substantives, adjectives to
adjectives, numbers to numbers ; and that the association is nearly
always formed within a single sense-department, so that red calls
up green, and hard, soft. But if the conditions are changed, and a
little more time is allowed the observer, the character of the asso-
ciated ideas is also radically changed. Fatigue, again, may bring
out purely mechanical associations (snow — ball, fish — dish) which
are ordinarily foreign to the observer's consciousness.
Introspective Analysis. — If a familiar visual stimulus (word,
simple picture) is presented to the observer, with the instruction
that he shall receive it passively and report the consequent course
of his mental processes, the following results appear. First, there
is a simultaneous association of stimulus and internal speech ; the
word or the pictured object is named. Thereupon follows an
associative complex, which may assume any one of three principal
forms, (i) The stimulus arouses, either at once or very shortly
after the named perception has become clear in consciousness,
and either as a whole or by way of some part or aspect, an affective
process, a feeling in the widest sense (p. 228). The feeling, in
turn, calls forth an associated idea, which may subsist for a time
alongside of the original perception, but soon replaces it. Thus,
a word printed in very small letters upon a large ground aroused
the feeling of loneliness ; a word printed in red, the feeling of ex-
citement ; the word 'blinding,' the feeling of a blinding light; and
then the feeling itself (or, in the author's view, the kinaesthetic and
other organic components of the feeling) brought up an idea which
supplanted the meaning of the stimulus-word. (2) In other cases
392 Association
the named perception is either supplemented or replaced by the
idea of some object or picture previously seen. Thus, an outline
drawing of a face may suggest the idea of a friend, whose features
are then, so to speak, read into the drawing ; the perception is
lost or merged in a simultaneous association. Or the word 'Tell,'
printed on a blue ground, calls up a familiar picture of William
Tell springing from a boat to the rocks ; the blue of the background
becomes the blue sky of the painting. There are many intermediate
forms between these extremes, as there are also between this group
of associations and the next. (3) Here the stimulus arouses an
idea which, at first thought, appears to be separate and detached ;
we have the traditional pattern of the successive association. And,
occasionally, we cannot go behind that pattern ; the named per-
ception and the idea seem to be mechanically linked ; we are in
presence of the limiting case. Usually, however, introspection
takes us farther. Thus, the outline drawing of a tent called forth
the idea of a certain city market ; and for a moment the observer
could simply report the bare succession of the experiences. But
then he found the cue : he had ridden through the market, on his
bicycle, in much the same attitude in which he now sat ; a massive
complex of organic sensations was common to the two situations. —
Observations of this sort make it quite clear that the type of associa-
tion is the simultaneous association, and that successive asso-
ciations — to put the matter a little paradoxically — are simply
simultaneous associations drawn out in time.
If we keep strictly to the observed facts, we can find
no psychological difference between the idea and the
association of ideas. Still, the practical difference remains
that our ideas come ready-made, whereas we can establish
new associations. May not introspection show the con-
scious mechanism of this novel grouping 't and may we
not thus get fresh light on the nature of the mixed per-
ception, and of the idea itself .''
Wundt has answered these questions in the affirmative.
He believes that associations are always established in the
§ III. T]ie Associative Consciousness 393
same way, and that the machinery can be laid bare by
experiment. All association, he says, is connection of
elementary processes ; the phrase ' association of ideas,'
if it means that the ideas connect as such, is a misnomer.
And the connection of elements is itself a twofold process.
When a perception or idea is effective for association, its
elements first arouse images that are like themselves ; there
is a fusion of like with like. But the terms of this fusion
have been together, in former conscious presents, with
other, unUke elements ; the fusion is, therefore, at once
supplemented ; the homogeneous nucleus is surrounded
by all sorts of connected processes. If the association is
simultaneous, this is a full account of the matter. If it
is successive, then some element in the cluster of associates
about the original nucleus arouses its like ; a new fusion
is formed ; and so the process is repeated.
Wundt's first proposition, that only the elementary components
of perception and idea can enter into associative connection, iif
based partly upon the nature of the idea, and partly upon facts
of observation. The idea is fluid, variable, instable ; it does not
stand still to be connected ; it has no solidity, so to say, that
should allow it to be coupled with another, equally solid idea.
And if we observe associations under experimental conditions, we
find that they hinge, in reality, not upon the ideas as wholes, but
upon some simple constituent of the ideas.
This point established, we may go on to the mode of elementary
connection. The first stage, the fusion of like with like, be-
comes clear if we translate it into physiological terms. When a
complex stimulus is presented to the organism, it arouses a com-
plex excitation in the brain. But some at least of the component
stimuli have impressed the brain in the past. These stimuli, then,,
running into the paths of previous impression, reexcite a previous
brain-activity; the other, new stimuli have to make their im-
pression for themselves. Now, if we retranslate, we have the
394 Association
conscious fact of fusion. The incoming sensation or image, if it
has been in consciousness before, — and otherwise it could not
be effective for association, — blends with its own image, with its
rearoused self. Since the terms of this fusion are quahtatively
alike, the conscious resultant is merely the element itself, given at
increased intensity and with a high degree of clearness ; we
know, Wundt says, that the familiar elements in a complex
situation stand out strongly and clearly, while the unfamihar
elements are weaker and more obscure ; here, then, is evidence
of the nuclear fusion. The second stage presents no difficulty.
The reinforced central element, just because it has been in con-
sciousness before, and is therefore fitted to arouse the nuclear
fusion, must also stand in connection with many other elementary
processes ; and it is merely a matter of circumstances which of
these shall actually be evoked.
What is to be said of this analysis? First, that it is by no
means to be confused with the traditional doctrine of association.
Wundt's fusion of like with like is not association by similarity ;
and his cluster of associates is not association by contiguity.
Every case of associates, whether 'by similarity' or 'by conti-
guity,' involves, according to Wundt, both of the elementary con-
nections : the rearousal of the like and its supplementing by the
unlike. Secondly, that the analysis is, as it professes to be, an
analysis of observed occurrence ; it differs from the older 'laws of
association,' not only in form and content, but also in derivation ;
it is not a product of logic, of reflection. The author offers only
two criticisms. The one is, that Wundt has placed the whole
mechanism of association in the realm of consciousness, whereas
there seems to be no question that, in many instances, the mech-
anism or a good part of it is purely physiological, and finds no
conscious representation at all. And the other is, that the fusion
of the incoming process with its imaginal twin, while as an hypoth-
esis it is adequate to the facts, is nevertheless not directly attested
by introspection. We might, perhaps, speak of a reinstatement
of the like, rather than of a fusion of like with like ; the concur-
rence of the present excitation with the preexisting impressional
tendency would then be a physiological process, to which the
References for Further Reading 395
emergence of the single element, strong and clear, would directly
correspond ; there would be no rearousal of the mental double.
The law of association (§ 107) will now operate as follows.
Two nonsense syllables, let us say, are given within the same con-
scious present. Later, the one of them is presented alone. The
single syllable, or that aspect of it (visual, auditory, kinaesthetic)
which was prominent in consciousness at the time of its earlier
presentation, reinstates itself; the previous impression of the
nervous system makes the path of excitation easy, and the per-
ception is clear and intensive. Along with reinstatement comes
associative supplementing : the other syllable appears in imaginal
form. So we have what appears to be a typical case of ' associa-
tion by contiguity ' ; but we also see the danger (p. 380) of identi-
fying the traditional law of contiguity with our own general law of
association.
A final word of caution ! We have spoken of impression, and
of associative tendency, as if these things were real physiological
characters. So, in one sense, they are : the nervous system
behaves in certain definite ways which we are in duty bound to rec-
ognise and to name. But it must be remembered that our know-
ledge is altogether indirect, drawn from the results of psychological
experiments. What the impression and what the associative ten-
dency are, in themselves, — what goes on in the nervous system
when a stimulus is impressed and an associative tendency estab-
lished, — of all this we know nothing. The physiological explana-
tion of association is, therefore, a problem for the future.
References for Further Reading
§§ 105-111. H. Ebbinghaus, Ueber das Ged'dchtnis, 1885; PsycJiol-
ogie, i., 1905, 633 ff. ; E. Claparede, L''associatio7i des idees, 1903 ;
W. Wundt, Physiol. Psychol., iii., 1903, 518 flf. For experimental
methods, C. S. Myers, A Text-book of Experimental Psychology., 1909,
144 ff. Discussions of association which have permanent value, but
which the authors would probably modify if they were writing to-day,
will be found in W. James, Principles of Psychol.., i., 1890, 550 ff. ;
O. Kiilpe, Outlines of Psychol.., [1^93] 1909? 169 ff.
MEMORY AND IMAGINATION
§ 112. Retention: the Course of the Image. — An impres-
sion made upon a plastic substance persists, for some
length of time, after the removal of the impressing object;
the substance retains the impression. Suppose, then, that
a stimulus has impressed the brain : the nervous substance
will retain this impression after the stimulus has ceased to
act. The sensation or perception will be followed by an
image or idea which — if nothing interferes with it — will
remain in consciousness so long as the impression retains
a certain depth. What happens to it in the meanwhile,
during the gradual obliteration of the impression ?
The question is not easy to answer. We saw in § 60
that every stimulus of moderate intensity arouses a wide-
spread reaction; and it is equally true that every image,
auditory or visual or what not, appears in a complex
mental setting. When we are dealing with sensation, our
organic attitude is determined and maintained by the stim-
ulus, which further serves to guide and correct our asso-
ciations ; consciousness is in relatively stable equilibrium.
But, when we are dealing with image, the organic attitude
is likely to vary, and the associations, being of the same
mental stuff as the image, are likely to influence it in vari-
ous ways. Besides, the course of an image can hardly be
followed, even under the most favourable experimental
conditions, for any length of time. Some new impression
is sure to stamp out the old, or some new stimulus to re-
arouse the preexisting tendencies of the part of the brain im-
pressed, and the image is thus cut across and interfered with.
396
§ 112. Retention: The Course of the Image 397
However, if we put together the results of investigations
so far made, we may say that an image or image-complex
is subject to three distinguishable modes of change : it may
die away, it may approach a type, or it may be incorpo-
rated, whole or part, in new imaginal formations.
We often read of the fading and decaying of images, though we
do not so often find a description of the process. If we consider
the attributes of the image, it seems that those which suffer directly
by lapse of time are intensity and duration ; loud images become
faint, bright images (p. 204) become dull, and all images flit
through consciousness the more hurriedly, the farther back the
original experiences lie. These are intrinsic changes, due to the
weakening of the nervous impression.
Other factors, however, are at work. Thus the quality of the
visual image is definitely affected by the nature of the objective
illumination to which the retina is subjected : images of colours
and greys tend to lighten in the light and to darken in the dark.
Tonal images tend to flat, possibly because the accompanying kin-
aesthetic image of laryngeal adjustment tends to weaken. More
important is the gradual shift from individual quality to regional
or type quaHty. We saw in § 107 that an association may be
aroused, not only by the recurrence of a familiar idea, but also by
the occurrence of a novel but similar idea ; the nervous conditions
of like ideas are partially the same. It appears, now, that the
nervous conditions of neighbouring sensory qualities are in part
the same, or at least that the impression of any one subarouses
the impressions of the others. For, if a particular colour or tone
is impressed, the observer soon grows doubtful of its identity ; when
he seeks to call it up, he may image a quality that lies at some
little distance from it on the scale of colours or tones ; when a
shghtly different colour or tone is presented, he may be misled by
his image into pronouncing it the same. The image is, of course,
always an individual quality, but its quaUty is no longer strictly
correlated with that of the primary sensation.
The same result may be brought about, indirectly, by verbal
398 Memory and Imagination
association. We may remember a colour as red, a light as dark
grey, a tone as high. If we then try, at some later time, to imag^
the colour or the hght or the tone, we may image that special
quaUty which, under the conditions of the moment, is the nearest
representative of the class red, dark grey, high ; that is, the qual-
ity whose image is ' readiest,' most easily evoked by the associa-
tive tendencies of the verbal idea. In such cases we may travel
very far from the proper image of the primary sensation. Or,
again, we may remember the original quaUty by absolute impres-
sion (p. 313). As our experience grows, we form in all depart-
ments ideas hke the composite and standardised idea of space to
which we referred in § 89 ; and these ideas may, like that, lapse
into unconsciousness and be replaced by a cortical set, or may
show only as total conscious attitudes, or may be represented on
the particular occasion in some partial and fragmentary way. On
its spatial side, e.g., the image is mainly determined by absolute
impression, so that small extensions become still smaller, and large
still larger, in the corresponding images. The same influence may
be traced in the case of intensity ^ and duration. So with quality :
if the colour strikes us as a beautiful red, the light as an unusually
dark grey, the tone as excruciatingly high, we shall be likely, later
on, to confuse the imaged qualities with those of other, similarly
impressive stimuli.
^ The attribute of intensity has often been denied to the image. "The idea
of the brightest radiance does not shine, that of the intensest noise does not
sound" (H. Lotze, Outlines of Psychology, tr. 1886, 28); "the ideas of the
slightest rustling and of the loudest thunder exhibit no difference in intensity
whatever" (T. Z\e^:\er\, Introd. to Physiol. Psychol.,U. 1895, 154). The author
believes that such statements betray a form of the stimulus-error (p. 218).
At all events, there is no doubt — since the experimental evidence is positive
— that images have intensity. If now the image of the thunder is of long
standing, and the image of rustling is recent; and if the underlying nervous
impressions are allowed to fade out undisturbed ; then there may come a time
when the intensities are equally weak. Only under these exceptional condi-
tions, however, can Ziehen's remark be true. And, as a rule, the image of
thunder will always, whatever its age, be stronger than the image of rustling,
because thunder makes on us the absolute impression of a typically loud sound,
and rustling that of a typically faint, stealthy sound.
§ 112. Retention: The Course of the Image 399
We have spoken of ' remembering ' the original colour or tone
by means of the class-name and the absolute impression. A dis-
cussion of the memory consciousness is not yet in place. Notice,
however, that in this process of remembering the image may have
disappeared altogether ; it is only by accident that it can recur;
in the great majority of cases it has been ousted by another image.
Most images, indeed, are not allowed to live out their lives ; the
incoming stimuli and the preexisting tendencies of the nervous
system are too much for them.
Instructive observations on the career of imaginal complexes
may be made as follows. The observer draws on paper, from a
copy or an object, some fairly simple figure : a fleur-de-lys, an
heraldic animal. A week later, he is asked to repeat his drawing
from the image of the previous drawing; a week later the same
request is made, and so on. It is found that certain features of
the image may disappear entirely, and that oftentimes the re-
peated figure tends to approach a schematic type ; these results
are already familiar to us. It is also found, however, that the fig-
ure may be transformed : certain principal lines of the original
drop out, while certain secondary lines form associations of their
own, and become dominant ; so that, in course of time, the fleur-
de-lys has changed, e.g., into a Greek cross. The method does
not permit of detailed interpretation, but it shows that an image
may persist, unsuspected, in consciousness, through incorporation
in a number of successive ideas.
The Memory After-image. — Most observers find no difficulty in
passing directly — that is, after a very brief interval (p. 298) — from
sensation to image ; even in the case of vision, conditions may be
arranged which prevent interference by after-images (pp. 68, 72).
Sometimes, however, the sensation is followed by a process, lasting
perhaps from 5 to 10 sec, which Fechner called the memory
after-image. This is not an after-image proper : for it depends, as
the image does but the after-image does not, upon the clearness
of the primary sensation ; it appears only if, like an image, it is
sought for, called up ; it is stronger and clearer after a brief
observation, while the after-image is better when stimulation is pro-
longed ; and it repeats the lights and colours of the original at a
400 Memory and Imagination
time when the after-image, were it present, would be complement-
ary. The memory after-image is, in fact, a sort of instantaneous
photograph of the sensation or perception. It is reported by
observers who have a very poor general furniture of visual imagery,
and doubtless plays a larger part in the imageless than in the
imaginal mind (§ 141) ; but many minds of the latter type possess
it. We shall attempt an explanation later (§ 118).
The Perseverative Tendeticy. — Images themselves seem, at times,
to crop up of their own accord ; we are haunted by tunes, by tags
of verse, by a picture, by the face of a drowned man ; and ideas
occur to us in the most incongruous way. Experiments on verbal
association (pp. 274 f.) show the same phenomenon; the ob-
server will repeat a word again and again, in his series of responses,
without realising that he is obsessed by this particular associate.
Grouping all these facts together, certain psychologists have con-
cluded that the brain is the seat of what they term perseverative
tendencies. The impression does not fade out steadily, but re-
covers itself, so to speak, from time to time and under favourable
conditions, so that the idea may surge back spontaneously into
consciousness.
If this hypothesis is correct, we have to distinguish three sets of
nervous tendencies. First, we have the impressional tendency,
which represents the ' readiness ' of an idea to emerge, the dis-
tance below the conscious limen at which its excitatory process is
now going on. Secondly, we have the associative tendency, which
represents the strength of the connection between one impression
and another, or the degree of excitation that will accrue to the one
when the other is reexcited. Thirdly, we have the perseverative
tendency, which is a sort of rhythm imposed on the impressional
tendency, such that the idea does, now and again, emerge with-
out the aid of the associative tendencies.
Why, then, should we separate impressional and perseverative
tendency? Why should we not say, at once, that the impressional
tendency varies, oscillates, fluctuates? Because the status of the
impressional tendency, as we have defined it, is fairly well assured,
whereas the status of the perseverative tendency is doubtful. All
these hauntings and recurrences may, in fact, be accounted for in
§ 113- Retention: The Process of Dissociation 401
one or other of the three ways outUned on p. 386, and accounted
for more satisfactorily than on the assumption of perseverative ten-
dency. Perseveration is strongest under two, somewhat contradic-
tory conditions : immediately after the original perception, and
during the onset of fatigue. In the former event, both the im-
pressional and associative tendencies will be strong, so that there is
little to choose between the alternative explanations. But in the
second case, of fatigue, it is not easy to see how the perseverative
tendency should be set in operation, whereas it is natural that the
more ingrained, more permanent associative tendencies should
alone remain active, and that the range of consciousness should thus
be restricted.
There is, then, no harm in keeping the terms ' perseveration ' and
'perseverative tendency' to designate a certain mode of behaviour
of images and a certain part-problem of nervous retention. But
there is, in the author's opinion, no positive evidence that the
behaviour is unique, or the problem insoluble by appeal to impres-
sional and associative tendencies.
§ 113. Retention: The Process of Dissociation. — The as-
sociation, like the image, is retained for a time ; the associ-
ative tendencies persist along with the impressions. But
an association, if left to itself, soon begins to break up ; the
associative tendencies weaken, at first quickly, then more
and more slowly, until finally they cease, so far as conscious-
ness is concerned, to act at all. It is possible, by means of
nonsense syllables, to trace out this process of dissociation,
and it is also possible to determine, by variation of the
experimental conditions, what are the principal influences
that make for permanent retention.
The use of nonsense syllables permits us to follow the associa-
tive tendencies from their first establishment to their final decay ;
there is practically no danger of reinforcement or of inhibition in
the intervals of the experiment. It seems certain that these
limited and clean-cut tendencies do, in time, disappear ; they die
402 Memory and Imagination
of old age. The much more complicated tendencies established
by meaningful material seem, on the other hand, to persist, below
the limen of consciousness, for very long periods, possibly
throughout the individual life. We learn poems, in childhood,
which we may never think of again until we find our own chil-
dren learning them twenty or thirty years later. We try our
memory, and discover that, except for a tag here and a tag there,
we have forgotten everything. Nevertheless, if we sit down to
memorise one of these old poems and another, new poem of
the same length, the same metrical form, and the same level of
imagination, we regain the old with considerably fewer readings
than must be given to the new ; the associative tendencies were
there, in subliminal degree, although the associations had long
since vanished. Childhood, of course, is a plastic period; the
original impressions were deep, and the original associations were
little interfered with. But even if the experiment is transferred to
adult life, the associative tendencies show an extraordinary per-
sistence. Ebbinghaus learned some stanzas of Byron's " Don Juan "
in his thirty-sixth year, and did not look at them again for
twenty-two years. He had completely forgotten them, but he found
evidence that the associative tendencies had not died out.
It has been shown, by the experiments with nonsense syllables,
that, if two associative tendencies are of the same strength but of
different ages, a repetition of the association has the greater value
for the older-established tendencies. Hence the advantage of
distributing in time the readings of the material to be memorised
(§ 109) ; the associations that are strengthened by the successive
readings are older than they would be were the readings massed
together. The explanation appears to be as follows. Remote
and retroactive associations disappear more quickly than direct
associations. The successive readings will therefore sustain and
reinforce the direct associations, while they may have actually to
reestablish the others ; the benefit of the readings will fall mainly
to the eiirect associations. Distribution in time thus plays directly
into the hands of the law of initial inhibition. Contrariwise, the
massing of the readings will keep the secondary associations alive,
and in so far will delay the action of the law.
§ 1 14- Reteiitio7i : Individual Differences 403
§ 114. Retention: Individual Differences. — The image is
a later development than the sensation, and we may ex-
pect, accordingly, that it will show a greater individual
variation. The psychology of sensation is concerned
primarily with uniformities ; all those who possess normal
sense-organs have the same general endowment of sensa-
tions ; and we refer striking peculiarities like colour-blind-
ness, tone deafness, insensitivity to pitch differences, — we
refer these peculiarities, when they appear, to some abnor-
mality of the organ. The psychology of the image, on
the other hand, is essentially an individual psychology.
The normal brain is a much more variable thing than the
normal sense-organ, and the ideas of different minds are
constituted in very different ways.
Attempts have been made to reduce these differences
to order, and to classify observers in terms of their imagi-
nal type. Four principal modes of ideation have thus
been distinguished : the visual, the auditory-kinaesthetic,
the kinaesthetic, and the mixed. The visually minded ob-
server, for instance, retains his experiences in terms of vis-
ual imagery ; his perceptions, of whatever kind, are trans-
lated into visual ideas. An observer of the mixed type
repeats in image what he has received in sensation, though
he will probably have a certain leaning towards a particu-
lar class of images. It seems that there is no pure audi-
tory type, and no visual-kin aesthetic type ; at any rate,
these cases are exceptional. Words are retained in simi-
larly characteristic forms : as visual, and as auditory-kinaes-
thetic images. It is probable, again, that the auditory-
kinaesthetic elements do not occur separately, although the
emphasis may be preponderantly upon the one or the
other.
404 Memory and Imagination
While, however, these gross differences undoubtedly ex-
ist, generalisation must not be pushed too far. Thus, we
cannot argue from verbal to total type ; a man may image
words as auditory-kinaesthetic, and yet be, on the whole,
visually minded. Indeed, it may be questioned whether,
apart from the mixed mode of imagery, a total type can be
said to exist at all ; the imagery of a given observer will
vary both with the manner of presentation of the original
material, and with the purpose or intention with which the
material is approached. We might, perhaps, sum up the
situation by saying that individuals are predisposed for
different kinds of imagery ; that, as a rule, the predispo-
sition represents a line of naturally least resistance, but
does not prevent the opening of other lines (by the nature
of the stimulus, by special cortical set) ; and that, in certain
cases, the predisposition is exclusive and supreme.
We made a brief reference to imaginal type on p. 199. The
subject is, evidently, of great importance for education as well as
for psychology ; it has therefore received much attention, and
many methods for the determination of type have been devised
and applied. The principal result of the investigations is the
proof that type is far more variable and more complex than had
at first been supposed. Two points, in particular, may here be
mentioned. The first is that the presence of imagery does not
necessarily imply the use of imagery ; my mind may be full,
e.^., of visual images, and yet I may habitually mean and under-
stand, think and remember, in other than visual terms. And
the second is that a man's talent, or his choice of a profession, is
no indication of his imaginal type. " I should have thought," re-
marks Galton, " that the faculty [of visualisation] would be com-
mon among geometricians, but many of the highest seem able
somehow to get on without much of it." " I am myself a good
draughtsman," says James, " and have a very lively interest in
pictures, statues, architecture, and decoration. But I am an ex-
§ 1 14. Retention : Individual Differences 405
tremely poor visualiser " ; and Galton tells us that " men who de-
clare themselves entirely deficient in the power of seeing mental
pictures can become painters " of acknowledged rank. The
author knows a musician who has no tonal images whatever ; ask
him to go to the piano and play a certain composition, and he will
do so ; ask him if he can imagine what he is going to play, and he
will reply, ' No ! but I am going to play it.' On the other hand,
the author himself, who is no musician, is rarely if ever free from
musical imagery.
While these cautions are in place, it should be added that the
trend of imaginal type shows itself in various, fairly obvious ways.
The attitude of attention is different, according as one is visual
or auditory-kinaesthetic ; and the mode of recitation differs, being
slow and systematic in the former case, quick and impulsive in the
latter, while the mistakes made are in both instances characteristic.
A preponderant type may be traced in an author's style ; and it has
been suggested that the cardinal doctrines of the traditional British
psychology (§ 105) are to be explained by the fact, evident from
their books, that the writers were predominantly visual-minded.
There are also marked individual differences of associa-
tion. Observers in the psychological laboratory fall, as do
children in the schoolroom, into two great groups : the
quick learners and the slow learners. Popular psychology
has been all on the side of the slow pupil ; if he is slow, he
is also sure ; his knowledge is solidly established ; while his
more active-minded companion is pronounced shallow ; his
knowledge goes as easily as it comes. Retention, we have
no need to insist, is a very complicated matter, and there
may very well be conditions under which popular psychol-
ogy is right. Experiments seem to show, however, that
at least under certain circumstances it is definitely wrong.
The quick learner appears to retain as well as the slow ;
he has the advantage at the start, and he loses nothing by
lapse of time.
4o6 Memory and Imagination
The results of these experiments throw some light on the nature
of cramming, which has for the most part been roundly condemned
by educators. Against cramming it may be urged that the hasty
impression of a mass of heterogeneous material cannot be lasting ;
the law of retroactive inhibition will come into play, to weaken the
associative tendencies. The student who crams trusts to recency
of experience to carry him through ; he hopes that a certain
amount of his reading will cling to him just for the day or two
that he needs it. "Speedy oblivion," says James, " is the almost
inevitable fate of all that is committed to memory in this simple
way."
Even so, one might rejoin that speedy oblivion is not in itself a
disadvantage \ a good deal that we are obhged to learn at school
is better forgotten. But, that aside, the argument against cram-
ming misses the point that there are two kinds of cramming, a
good as well as a bad. If we wish to remember, we must submit
to the laws of memory ; and bad cramming simply ignores those
laws. Good cramming, on the other hand, is a very valuable
asset of the quick learner. It is " the rapid acquisition of a series
of facts, the vigorous getting up of a case, in order to exhibit well-
trained powers of comprehension" ;^ it is precisely the thing that
the lawyer, the lecturer, the teacher, the politician, the adminis-
trator find necessary to success. Moreover, good cramming is
itself of two kinds : we may cram with intent to remember, and
we may cram with intent to forget. Both forms are useful, e.g., to
the teacher : the one provides him with the expert's knowledge of
the details of his subject ; the other prevents his teaching from
becoming cut and dried.
As with cramming, so with skimming : it is generally repro-
bated. Yet it is surprising how accurate a knowledge may be
acquired by hurried, selective reading, if only one has had sufficient
practice. The predisposition to quick learning must, of course,
be present. What that is, in physiological terras, we do not know ;
but it is, at any rate, a gift, like mathematical ability or a singing
voice, and should be utilised rather than disparaged.
1 W. S. Jevons, Cram, in Mind, O. S. ii., 1877, 193 ff.
§ 115- TJie Recognitive Consciousness 407
§ 115. The Recognitive Consciousness. — Suppose that
you are entering a street-car. As you enter, you run your
eyes over the line of faces before you. The first half dozen of
your fellow-passengers are strangers ; their faces arouse no
interest, do not arrest your gaze. At the end of the car,
however, you see someone whom you know ; you recognise
him. A sudden change occurs in consciousness : you call
him by name, take a seat at his side, and begin to converse
with him. What was it, now, that happened in consciousness
at the moment of recognition 1 What are the conscious pro-
cesses involved in recognising }
To answer these questions we must recur to facts that
we already know. The first is the fact that every sensory
stimulus of moderate intensity arouses a widespread organic
reaction (§ 60); an illustration is given on p. 194. The
second is the fact that the organism not only senses, but
also feels ; sensory stimuli do more than arouse the sensation
and the associative and organic reaction ; they set up feel-
ings as well (§ 68). These secondary effects of stimulation
give us the key to the psychology of recognition. The re-
peated stimulus is felt otherwise than the novel stimulus,
and the feeling of familiarity, as we may call it, is the essen-
tial factor in recognising ; whenever it appears, we recog-
nise ; where it does not appear, we fail to recognise. The
sensations and ideas of the associative and organic reac-
tion then serve to make the recognition definite ; the per-
ception comes to us, not merely as familiar, but with the es-
pecial familiarity of a named, placed, and dated experience.
The reaction set up by a stimulus consists in part of associated
ideas, in part of kinaesthetic and other organic complexes. It is
tempting to suppose that the associated ideas help to constitute
recognition. They may, indeed, as we shall see in a moment, be
408 Memory and Imagination
the means to recognition ; and some of them — more particularly
the direct verbal associate, the name — seem oftentimes to be
bound up with the actual process of recognising. Nevertheless,
the experimental evidence is against them. Recognition is possible
in the absence of any associated idea whatsoever ; and a perception
may call up objectively correct associates and still not be recognised.
In the case of the organic complexes, decision is more difficult.
We have introspective warrant for believing that they enable us to
recognise the perception as that special perception. Whether
they enter into the process of recognising is difficult to say, be-
cause they blend with the organic complexes comprised in the
feeling of familiarity. So far as it goes, the evidence is also against
them ; recognition, as such, seems to be wholly a matter of the
feeling.
What, then, is this feeling ? In experiments upon recognition
it is variously reported as a glow of warmth, a sense of ownership,
a feeling of intimacy, a sense of being at home, a feehng of ease,
a comfortable feeling. It is a feelingin the narrower sense (p. 228),
pleasurable in its affective quality, diffusively organic in its
sensory character. That is all that analysis can tell us about
it. If we allow ourselves to speculate, we may go further,
and find a genetic sanction for its peculiar warmth and diffusion ;
we may suppose that it is a weakened survival of the emotion
of relief, of fear unfulfilled. To an animal so defenceless
as was primitive man, the strange must always have been cause for
anxiety ; ' fear ' is, by its etymology, the emotion of the ' farer,' of
the traveller away from home. The bodily attitude which ex-
presses recognition is, on this view, still the attitude of relief from
tension, of ease and confidence.'
1 Speculations of this sort are permissible in psychology, but must be ad-
mitted only very cautiously into one's psychological thinking ; their value de-
pends partly upon their explanatory power, partly upon their agreement with
what we know, or on other grounds can infer, of the nature of primitive mind;
they are always speculations. It is clear that they involve the great question
of biological heredity, into which it is here impossible to enter. The author
can do no more than point out that they do not necessarily involve the direct
transmission of mind, or of mental traits, from generation to generation; still
less, the transmission of acquired characters.
§ 115. The Recognitive Consciotisness 409
It must be added that some psychologists refuse to recognise
the feeUng of familiarity as a feeling, and regard it rather as a form
of combination (§ 104), an ultimate and underivable mental
character ; they speak of it as the quahty of familiarity. There are,
indeed, border-line experiences between recognition proper and
direct apprehension (which we discuss below), where analysis is
well-nigh impossible. But the author has read many thousands of
introspective reports upon recognition, and has never yet found
an observer to whom the feeling of familiarity appealed as unana-
lysable.
Definite and Indefinite Recognition. — Recognition appears in
two typical forms, which nevertheless grade into each other
through various intermediate stages. It is indefinite when the
feeling of familiarity comes up alone; when, e.g., we pass some
one in the street, and say to our companion, ' I'm sure I know
that face ! ' Somewhat more definite are the cases of recogni-
tion in which the feeling of familiarity expresses itself by a general
classificatory term. As we glance down the line of strangers in
the street-car, we may think to ourselves, ' Doctor, — farmer, —
commercial traveller.' Lastly, recognition may be definite : the
reinstatement of the organic reaction, or the arousal of a group of
associated ideas, or both of these supplements together, may refer
the present experience, unequivocally, to an incident of the past.
In the gross recognitions of everyday life there is usually some
constellation of associated ideas that is evoked by the perception ;
in the recognitions of the laboratory, the recurrence of the organic
reaction makes the stimulus — as the reports phrase it — 'stand
out,' makes it ' easy to grasp,' gives it a direct ' appeal ' to con-
sciousness ; it is then identified as the stimulus that was presented
before.
Direct and Indirect Recognition. — When we classify recognitions
as definite and indefinite, we are thinking of them as already
completed. If we look at their temporal course, the way in which
they are effected, we get a new ground of classification. Recog-
nition is direct or immediate when the perception at once, of
itself, calls up the recognitive feeling. Recognition is indirect or
mediate when the feeling attaches, not directly to the perception.
4IO Memory and Imagination
but to some associate of the perception. We pass a stranger on
the street ; but we are suddenly hailed by a familiar voice, and
the stranger is himself recognised as an old friend. We try to
find our host's face in a group-photograph of schoolboys, and we
are wholly puzzled to identify him. The face is pointed out, and
recognition follows ; the photograph grows more and more hke,
the more closely we examine it. In many instances of this sort
the recognitive consciousness shows a high degree of complexity.
Thus, we may be quite sure that the stranger is our old friend,
and yet continue to recognise nothing about him but his voice ;
the feeling of famiharity alternates with the feeling of strange-
ness, and the play of association becomes extremely complicated.
In principle, however, the conscious mechanism of recognition
is the same throughout.
Lack of Recognition. — Failure to recognise is not a mere ab-
sence of recognition, a conscious blank ; it is a positive expe-
rience. The unfamiliar perception, like the familiar, stands out
clear in the focus of consciousness, but its setting is different. It
is not easy to grasp, and it makes no appeal ; it is accompanied
by a feeling of strangeness, and by a general attitude of conscious-
ness which we may call the attitude of search or enquiry. We
may guess that the feeling of strangeness is the modern represent-
ative of primitive man's anxiety in face of the unknown ; it is an
uneasy restlessness, distinctly unpleasant (p. 269). The conscious
attitudes will occupy us later (§ 141).
§ 1 1 6. Recognition and Direct Apprehension. — The ner-
vous system as a whole, no less than the various sense-
organs, adapts itself to repeated stimuli. Affective pro-
cesses, as we know (§ 69), show this phenomenon of
adaptation ; pleasantness and unpleasantness fade out into
indifference. And the organic stir aroused by an affective
stimulus is more and more reduced, until it disappears
altogether.
It is not to be expected, then, that the feeling of famil-
iarity will persist unchanged, as perceptions are repeated.
§ ii6. Recognition and Direct Apprehension 411
We can, in fact, hardly be said to recognise the clothes
that we put on every morning, or the pen with which
we are accustomed to write ; we take them for granted.
When familiarity has gone thus far, when the familiar has
ceased to evoke an organic reaction and to be pleasant, we
say that recognition has passed into direct apprehension.
We have here an instance of the operation of a psychological
law to which reference was made in § 103, the universal law of
mental growth and decay. Just as meaning may cease to be
conscious, and may be carried in purely physiological terms, so
may recognition be reduced from a conscious process to an un-
conscious cortical set. Between the two extremes there are,
naturally, many intermediates. The feeling of familiarity, the
feeling of being at home, changes first to something that is still
feeling, though much weaker on the affective and much less clear
upon the sensory side, — to what we may describe as an 'of
course ' feeling, which is still some distance removed from sheer
indifference. As time goes on, this of-course feeling itself dies
out ; the affective adaptation reaches its term, and the perception
fails to arouse any organic reaction.
• In the author's opinion, the shift from consciousness to uncon-
sciousness may be complete. Some psychologists, however, be-
lieve that direct apprehension always involves consciousness. We
not only perceive objects by eye or ear ; we move to them, turn
to them, stand or sit to them, handle them. Hence, although the
feeling of familiarity has disappeared, the sight or sound will
throw us into a certain bodily attitude, whose sensory or imaginal
representation constitutes our apprehension of the object. That
is the theory. The author's principal objection to it is that it
appears to confuse recognition with meaning. The essential
thing in recognition, as experiments prove, is a feeling, the feeling
of familiarity ; the associated sensations arising from bodily atti-
tude, from action upon the object, may help to render recognition
definite, but do not constitute recognition. We can hardly argue^
then, that these sensations constitute recognition (direct appre-
412 Memory and Imagination
prehension) after the loss of the feeling. Kinaesthetic contexts
are common vehicles of meaning ; they may constitute an object
a pen, or even — in a certain sense — my pen; they cannot con-
stitute it my familiar pen. It is not difficult to make the objection
concrete. An old suit of clothes goes to the cleaner, an old type-
writer goes to the repairer. We say, on their return, that the
clothes must be ours, because they slip on so easily, and that the
machine must be ours, because we work it so readily ; but, we
add, we should never have recognised them as ours. That is, the
kinaesthetic complexes give them meaning, even a definite refer-
ence to our own past; but they do not, of necessity, involve
recognition. And if that is true, there is no reason why they
should involve or constitute direct apprehension, which, by
hypothesis, is the descendant of recognition. The theory implies
that, when the feeling of familiarity is gone, nothing but meaning
remains ; the author holds that direct apprehension is not identical
with meaning.
Another and more general objection is that there are many per-
ceptions in which kinaesthesis is not noticeably concerned. I see
the same landscape every day from my bedroom window, and I
apprehend it directly as that same landscape. It is true that I
look at it, turn to it ; but I look at it from many angles, with head
and eyes in various positions, so that the kinaesthetic components
must, at the best, be extremely variable ; and, as a matter of fact,
the eye-movements are rarely conscious, and the sensations due
to movements of head and body are usually incorporated in other
perceptions. It seems impossible that a kinaesthetic complex can
constitute my direct apprehension of the landscape. Moreover,
there are cases of direct apprehension, under laboratory conditions,
in which no trace of kinaesthesis can be discovered.
Disturbance of Apprehension. — It is interesting to note what
happens in consciousness if direct apprehension is for some reason
prevented. We look at our inkstand, and find that the pen which
we always keep in it has disappeared ; or we glance round the
breakfast room, and discover that a picture which always hangs on
a certain wall is absent. We have not been in the habit of recognis-
ing pen and picture ; they are too familiar. But now that they are
§ 11/. The Memory Consciousness 413
gone, the situation jars upon us ; we have a feeUng of helplessness
or of unpleasant surprise. This observation is itself important : it
shows that, when the organism has become adapted to a certain
complex of stimuli, the maintenance of adaptation depends upon
the persistence of the complex ; a negative change, a subtraction
of stimuh, creates a new situation, to which the organism reacts as
a whole. There is, however, another side to the case which is,
perhaps, still more important. At the moment of conscious dis-
turbance, before the unpleasant feeling has arisen, the of-course
feeling springs up in unusual strength ; it is as if, for a brief space,
we reverted in imagination to a recognition of the missing object.
The feeling is not intensive if measured by any absolute standard,
not as strong as the feeling of familiarity proper ; but it is more
pronounced than in the ordinary intermediate forms that connect
recognition with direct apprehension. Here, then, is opportunity
for the introspection of an elusive process, the conditions of whose
appearance are otherwise not easy to arrange.
§ 117. The Memory Consciousness. — Hitherto we have
said nothing of the conscious side of memory. We have
spoken of impression, associative tendency, retention, and
we have spoken of image, idea, and the association of ideas ;
but no image or idea is intrinsically a memory-image or a
memory-idea, and no association necessarily wears the
stamp of memory. An idea comes to us as remembered
only if it comes to us as consciously familiar. And the
memory consciousness is, in fact, the recognitive conscious-
ness over again, with the sole difference that the focal
process, the process remembered, is an idea and not a per-
ception. An idea is a memory if it is accompanied by
the feeling of familiarity ; and an idea is specifically re-
membered if it is placed and dated by the organic reaction
and by associated ideas.
The consciousness in which the memory-idea is set may
show the pattern either of primary or of secondary atten-
414 Memory and Imagination
tion (pp. 275 f.), and we speak accordingly of passive
memory or remembrance, and of active memory or recol-
lection. Both types of consciousness are discursive; that
is, are characterised by wandering of attention, shift of
imagery, variable play of association. Remembrance
shades off into day-dreaming or reverie, and thus into
imagination ; recollection shades off into search or enquiry,
and thus into thought. Between the two lies a long series
of intermediate forms.
The introduction of nonsense syllables, while it led us back from
logical meaning to psychological fact, and so helped to break up
the schematism of the traditional psychology of association, has
nevertheless done psychology a certain disservice. It has tended
to place the emphasis rather upon organism than upon mind ;
investigation has been directed to the question of what the ner-
vous system does rather than to that of what the memory con-
sciousness is. The knowledge thus acquired is, no doubt, of high
psychological importance, and we have taken account of it in
preceding Sections. But the definiteness of result, the fascination
of tracing the criss-cross of associative tendencies, and the possibil-
ity of throwing the results into quantitative form, — these things
have forced into the background of current interest the more
immediately psychological problem of a description of the
memory consciousness. Introspective studies are comparatively
few, and generalisation must be premature.
However, something may be said. If we take, first, the pattern
of consciousness in recollection, we find what may be figuratively
described as a reconstruction along the line of least resistance.
Thus, in trying to recall a group of meaningless visual forms, and
to draw them from memory, the observer does not start out with a
ready-made image. He may begin with a mere fragment of
imagery, or with no imagery at all. As he begins to draw, the
recognitive feeling at once appears, rejecting here and accepting
there ; and it remains in consciousness to determine the whole
course of recall and the nature of the final product, as well as to
§ 117- The Memory Consciousness 415
react upon that product when present in perceptual form. Another
very promment feature of the recollecting consciousness is the
emotive attitude of expected ease or difficulty of recall; this also
may intervene as soon as the first clue, such as an indefinite visual
image of position, has arisen. The drawing, then, is not a repro-
duction, a copy of the original perception, mediated by retention ;
it is a reconstruction, a construction of a particular result that is
accepted in place of the original.
If the figures to be recalled are pictures of familiar objects, the
gross clue to the recollection may be given by a visual image. But
the details are again worked out by a process of reconstruction.
The criteria of acceptance are direct recognition of an image ;
relative clearness of imagery (though this is ineffective as against
even a very weak recognitive feeling) ; absence of rival imagery ;
and the observer's general knowledge of the objects pictured.
Here, too, we are far removed from a simple reproduction.
Nevertheless, the reconstruction follows the line of least nervous
resistance. There is a tendency, so far as mental constitution per-
mits, to recall in kind : visual perception by visual imagery, audi-
tory perception by auditory imagery. Familiar verbal associations,
especially names, are used as aids to. recall. Familiar sounds are
recalled by way of the kinaesthetic processes aroused in their imita-
tion. The image tends to lose its specificity and to approach a
type or mean : a voice, at first imaged in its individual timbre, is
presently called up as bass or tenor only. In the recall of pictures,
the observer falls into a form of the stimulus-error, and replaces the
imagery of the picture by that of the object pictured.
This account, fragmentary as it is, will suffice both to indicate
the general character of consciousness in recollection, and to illustrate
the difficulty of adequate introspection. The observer has to
describe processes of extreme complexity, and will naturally turn
first to what is most emphatic or to what he is most confidently ex-
pecting. The field must be raked over again and yet again before
we can be sure that we have gathered up the full introspective
yield. Moreover, the observer has to report complexes that are
hurrying through consciousness and changing as they go ; he is
therefore likely to report in large, general terms ; he has no time
4i6 Memory mid Imagination
for analysis ; he points a verbal finger at the retreating process,
and therewith turns to its successor. But then every one of these,
largely designated processes must be made the topic of a special
analysis ; so that a memory study may really set more problems
than it solves. There is, indeed, a vast range of work, directly in
view, that still remains to be done.
As regards the pattern of consciousness in remembrance, our
data are yet more scanty. There seems to be, behind the recog-
nitive feeling, a general emotive attitude that holds us, so to say,
to the same objective situation, to the same empirical context.
This attitude serves as conscious background for processes of extra-
ordinary instability. Attention is labile and fluid ; the focus of
consciousness is occupied now by visual or other imagery, now by
scraps of kinaesthesis, now by personal references, organic or
verbal ; consciousness itself contracts and expands, pauses and hur-
ries, and shows the most abrupt changes of direction. The
author is well aware that this description is both figurative and
conventional. It will, however, be a long time before psychologists
can offer a composite photograph of the total consciousness in re-
membrance.
§ 1 1 8. The Memory-image and the Image of Imagination. — •
In minds of the visual type, imaginal complexes, of the
same general degree of complexity as perceptions, are of
common occurrence, and may readily be aroused under
experimental conditions. These complexes fall into two
great groups. Some of them have a personal reference,
and represent definite incidents of the observer's past ex-
perience ; others lack the personal reference, and have no
associations either of time or of place. The former, in
other words, are what would ordinarily be termed memory-
images ; the latter are images of imagination.
The two kinds of images present marked differences to
introspection, but the differences are precisely the reverse
of what, under the influence of popular psychology, we
§ ii8. Memoiy-iniage and Image of Imagination 417
might expect. Popular psychology regards the memory-
image as a stable copy of past perception, and the image
of imagination as subject to kaleidoscopic change. In
fact, it is the memory-image that varies, and the image of
imagination that is stable.
The observer is placed, as he prefers, in a dark room, or in the
light, facing a blank wall, and is asked to report his images as
they appear ; words or sentences are spoken by the experimenter,
as cues for the arousal of memory and imagination. It is found
that the memory-images are filmy and vaporous, that they show
little or no relief and little or no diversity of light and shade, and
that they are often colourless, while the images of imagination are
substantial, extend into the third dimension, and are often highly
coloured. The memory-images develope slowly, are liable to
continual change, and last but a short time ; the images of imagi-
nation present themselves at once and as wholes, change but little,
if at all, and are persistent. The memory-images involve roving
eye-movements and general motor restlessness ; the images of im-
agination involve steady fixation and motor quiescence. Both
images are accompanied by, or interfused with, kinaesthetic and
other organic processes, but the character of the processes is
different. Kinaesthesis comes in to fill out the gaps and blanks in
the memory-image ; the observer sometimes remarks that he can't
say what he sees and what he feels. This filling or supplementing
is always of an imitative sort, repeating certain phases of the
original experience. In imagination, on the other hand, the
organic factors are empathic : ^ thus, with the image of a fish, an
observer reported " cool, pleasant sensations all up my arms ; slip-
pery feeling in my throat ; coolness in my eyes ; the object spreads
all over me and I over it ; it is not referred to me, but I belong to it."
Finally, the image of memory brings with it the pleasurable recog-
nitive feeling, whereas the image of imagination is set upon a
background of feeling which the observers variously describe
^ Empathy (a word formed on the analogy of sympathy) is the name given
to that process of humanising objects, of reading or feeling ourselves into
them, which we described on p. t^t^t^.
2 E
41 8 Memory and Imagination
as a feeling of strangeness, of novelty, of personal detachment, of
creepiness, of weirdness, of unordinariness, of peculiar discomfort
The same phenomena recur with auditory and olfactory images.
Auditory memory-images involve movements of the larynx, and
olfactory memory-images involve tvvitchings of the nostrils, which
are not found with images of imagination. In both cases, the
memory-images are less substantial than the images of imagination,
and run a different temporal course. The characteristic feelings,
of familiarity and strangeness, appear as they do with visual
images.
These are the extreme forms of the imaginal complex, the
typical memory-image and the typical image of imagination.
There are many intermediate forms, which seem to contain both
memory and imaginative elements. In particular, the imaginal
complexes which represent objects in daily use, or objects of a
familiar environment, appear to pass from the memory to the
imaginative form ; they become stable and persistent ; but they
are then wholly indifferent, felt neither as familiar nor as strange.
We may regard them as corresponding, in image, to the direct
apprehension of perception. The author is, indeed, disposed to
believe that this observation may be generaUsed; that all direct
apprehension, in remembrance and recollection, occurs in imagina-
tive rather than in memory terms. When we solve a geometrical
problem by help of a remembered figure, or of some previous re-
sult, the figure or the result comes to us as a whole, clearly and
substantially, almost as if it were a perception. There is here, of
course, a danger of confusing fact with meaning ; of supposing that,
because the meaning of the older work is clear and permanent,
therefore its representation in consciousness is also stable and sub-
stantial. Nevertheless, it seems to the author that the conscious
stuff of most habitual memories is not that of the t3^pical memory-
image, but much more nearly resembles the material of the image
of imagination.
Is it not something of a paradox that the memory-image
should be thus variable and instable .-* At first thought,
yes : because we are ready to accept, from popular psychol-
§ Ii8. Memory-image and Image of Imagination 419
ogy, the notion that an image is a memory-image of itself,
in its own right ; and if that were the case, the image must
of necessity copy or reproduce the perception. On reflec-
tion, no : because the image is, after all, made into a mem-
ory-image by the feeling of familiarity. So there is no
reason in the world why it should copy the original experi-
ence. All it has to do — if we may ourselves talk a popu-
lar psychology — is to mean that experience (the meaning
is given as the context of associated ideas and attitude) and
to be recognised as meaning it. Suppose for a moment
that memory-images were just weaker copies of the earlier
perceptions, and nothing less or more : our mental life
would, so far as we can imagine it, be an inextricable con-
fusion of photographically accurate records. It is, in reality,
because the image breaks up, because nervous impressions
are telescoped, short-circuited, interchanged, suppressed,
that memory, as we have memory, is at all possible. The
remark has often been made that, if we did not forget, we
could not remember. That is true. But we may go farther
and say that, if the mental image could not decay, it could
not either be the conscious vehicle of memory.
On the other hand, if there is to be such a thing as im-
agination, then the image of imagination must be persistent
and substantial. An image is, psychologically, made into
an image of imagination by the feeling of strangeness.
But that the image should simply mean 'something new'
is not enough ; it must be something new; it must stay to
be looked at, to be described, to be expressed in artistic
form; poet and painter and sculptor would be in sorry case
if their minds were whirligigs of changing imagery. Why,
then, do we not have the inextricable confusion of which
we spoke just now .? Because the image of imagination,
420 Memory and hnagination
being new, has no associations ; it stands singly at the focus
of consciousness, as objects do that we perceive for the
first time ; and if it should, presently, remind us of some-
thing, the associates will be memory-images, and not other
images of imagination. Besides, the image of imagina-
tion is not persistent in the sense of those weaker copies
of perception with which the popular psychology of mem-
ory operates. In this respect, too, it resembles perception :
it is persistent and substantial under its own conditions ;
but if it has once gone, it must either be rebuilt, or recalled
as an image of memory.
All through this chapter of psychology we see the danger of
arguing from a preconceived theory, instead of appealing directly,
introspectively, to mind itself. The associationist doctrine is that
recognition implies the comparison of past image with present
perception ; identification follows. But that is not what happens
in recognition. We are taught, similarly, that the memory-image
copies the original experience. It may ; but as a rule, again, it
does not. We are taught that the image of imagination is a rest-
less, irresponsible thing, always in the throes of dissolution and re-
combination J but it is not. We are taught that mind moves, as
if on stepping-stones, from idea to idea ; once more, it does not.
The contents of the preceding Sections are, indeed, a strong testi-
monial to the value of the experimental method. But for that,
we should still be repeating the traditional formulas. And if the
Sections are scrappy, and their generalisations uncertain, this is
not the fault of the method, but merely of its recency of application.
Let us return to the images. It is clear, from what we have
learned of the imaginal complexes in memory and imagination,
that the elementary imaginal process, the image of § 6i, has two
distinct forms. On the one side stands the image that may be
confused with sensation. This image appears in perception, in
the memory after-image, in synaesthesia, in hallucination, in the
image of imagination, in habitual memories ; it moves with move-
ments of the eyes, and may leave an after-image. On the other
§ 1 19- TJie Imaginative Consciousness 42 1
side stands the image that is of fihnier texture than sensation ; it
appears in the memory-image, does not move with eye-movement,
and leaves no after-image. To explain the occurrence of the two
forms, we must assume either that there are two modes of cortical
function, or that the stable image somehow involves sensory
stimulation, while the instable image is wholly of central origin.
The former of these alternatives is possible ; we know very Httle
of the modes of cortical behaviour ; but the second appears to the
author to be, on the whole, the more probable. A recent writer
has suggested that the stable image is really a secondary sensation ;
the stimulus which acts upon a sense-organ directly arouses its
corresponding sensation ; but the excitation irradiates in the cortex,
spreads to other sensory areas, and thus indirectly arouses other
sensations. We have here, then, a theory which might replace
the theory of synaesthesia outlined on p. 197. It is, however, not
easy to see why the secondary sensation, which itself corresponds
not to a process of peripheral stimulation but to a central excita-
tion, and is therefore aroused in the same manner as the instable
image, should appear as sensation ; and it is especially difficult to
see why it should retain the sensory character when — as in the
case of habitual memories, or of certain images of imagination —
there is no peripheral stimulus' of any kind. The author suggests
that the sensory character of the stable image may be due to an ac-
tual stimulation of the sense-organ by way of the centrifugal sen-
sory conduction-paths, — though the suggestion is worth little, so
long as the conditions under which these paths are thrown into
function remain obscure.
§ 119. The Imaginative Consciousness. — A great deal has
been written about the imagination ; but, as a matter of
fact, we know very little indeed of the imaginative conscious-
ness. Most of the psychological accounts are couched in
terms of some psychological theory, and most of the in-
trospective descriptions published in support of theory were
obtained from untrained observers and without sufficient
control of the conditions of observation.
422 Memory and Imagination
It seems clear that an idea comes to us as imagined only
if it comes as consciously unfamiliar, with the feeling of
novelty or strangeness upon it ; this feeling of strangeness
is as characteristic of imagination as the feeling of famil-
iarity is of memory. The consciousness in which the idea
of imagination is set may then show the pattern either of
primary or of secondary attention (pp. 275 f.), and we
speak accordingly of passive or reproductive, and of active,
creative or constructive imagination. Both types of con-
sciousness are integrative rather than discursive ; the sphere
of attention is limited, the play of association regulated.
Creative imagination shades off into thought, and thus
completes the psychological circle of p. 414.
Two hypotheses of the nature of the imaginative consciousness
are sharply opposed in current discussion. According to the one,
the imaginative idea or constellation comes as if from without, by
inspiration ; the poem sings itself, the painting groups and colours
itself, to the mental ear and eye ; imagination is a native gift or
endowment that finds rather than seeks expression. According
to the other, the imaginative consciousness is profusely imaginal ;
associations throng about the focal process; and the product of
imagination is the result of choice and arrangement of these
associated ideas. On the former hypothesis, the imaginatively
gifted individual is the dreamer of dreams and the seer of visions ;
on the latter, he is the planner, the moulder, the constructor. So
imagination appears now as the typically passive and now as the
typically active temperament : precisely as genius is described now
as the capacity of doing great things without effort, and now as
the capacity for taking infinite pains. And witnesses can be brought
on both sides.
We have not the data for a final characterisation. To the author,
however, the psychology of imagination takes shape somewhat as
follows. Behind everything lies a cortical set, a nervous bias,
perhaps inherited and permanent, perhaps acquired and temporary.
§ 119- The Imaginative Consciousness 423
This background may not appear in consciousness at all ; or it may
appear as a vague, conscious attitude (passive imagination), or
again as a more or less definite plan, aim, ambition, intention
(active imagination). Whether conscious or not, the nervous dis-
position determines the course of consciousness. It also helps
to initiate the imaginative complex, the first concrete clue to which
usually comes, in fact, as an inspiration, a happy thought : some
external situation, or some group of associative tendencies that is
active at the moment, touches off the disposition, and the initial
idea flashes into consciousness. Whether the idea is crude or
complete, and whether the following consciousness is narrow or
broad, concentrated or richly imaginal, these things depend al-
together upon circumstances. If we are dealing with active imag-
ination, the subsequent stage, in which the idea is worked up and
worked over, — while, no doubt, it may be relieved here and there
by other happy thoughts, — is essentially a stage of skilled labour,
of secondary attention, that ends only with the expression of the
idea in objective terms. Meanwhile, consciousness has been
variously emotive. The imaginative ideas bring with them the
feeling of strangeness. But just as the pleasantness of recognition
may be lost in the stronger unpleasantness of the recognised object,
so may the strangeness of imagination be lost in the pleasure of
success, or merged in the stronger unpleasantness of failure ; and
these feelings may themselves alternate, so that consciousness
swings between the poles of affective experience. Meanwhile, also,
all sorts of empathic complexes have formed about the focal pro-
cesses, vivifying and personalising the partial products of the construc-
tive effort. Whatever happens, the total consciousness is directed
and regulated by the underlying nervous disposition. In memory,
the observer is always within a certain universe of discourse; there
are limits, set by the fixity of the past occurrence, which he may
not transgress; but within this breadth of context he can move at
will; consciousness is discursive. In imagination, consciousness
proceeds, as a whole, from the fountain-head of disposition ; there
are no limits of any kind, save those of individual capacity and
experience ; but the stream, whatever its volume, flows always in a
determinate direction ; consciousness, as we have said, is integrative.
424 Memory and Imagination
But what are the focal processes? One is tempted to sa}', off-
hand, — images. And the answer is probably correct, if one ma)
define the term 'image.' Oftentimes, of course, there are images
in the literal sense, visual, auditory-kinaesthetic, kinaesthetic. Often-
times there are verbal images. But the name must also be ex-
tended to processes that merely symbolise perceptual experience,
and are no more like perception than the printed report of an operatic
performance is like the performance. When we trace the images
of imagination beyond the stage of perceptual complexity (§ 118),
we find that they undergo translation and reduction : translation
out of one sense-department, along the line of least nervous resist-
ance, into another ; and reduction from explicit representation to
symbolism. Reduction does not mean approximation to a type;
what takes place is that a mere schema, or part-aspect, or fragment
of the complex comes to do shorthand service for the whole. This
seems to be the truth in the text-book statements that the images
of imagination tend to grow vague, general, abstract, to become
shadows of their original selves. They never grow vague, in the
ordinary sense of the word ; on the contrary, all of them, images
proper, words, and reductions, are sensory in their reality and sub-
stantialness ; that is a point that we have already emphasised, and
that we must by no means lose sight of; but they do become
simple and conventionahsed, they do tend to symbolise rather than
to represent. —
The reader may be reminded that this account is tentative, and
far outruns the experimental data. It has the merit of reconciling
the two hypotheses mentioned at the outset, and it accords with
such introspective observations as we have. It may, however, be
very seriously modified by future investigation.
§ 120. Illusions of Recognition and Memory. — Illusory
memories and recognitions are of two kinds. We may re-
member or recognise something which is really, objectively
unfamiliar to us, and we may fail to recognise or remember
something which once formed part of our experience.
Both types of illusion are quite common.
§ I20. Illusions of Recognition and Memory 425
Most persons, perhaps, have had occasional experience of what
is called paramnesia or false recognition, a ' feeling that all this has
happened before,' which persists for a few seconds in spite of the
knowledge that the experience is novel. Various explanations have
been offered of the phenomenon. It occurs most frequently after
periods of emotional stress, or in the state of extreme mental fatigue ;
that is, at a time when the associative tendencies are abnormally-
weak. And it seems to depend, essentially, upon a disjunction of
processes that are normally held together in a conscious present.
Suppose the following case : you are about to cross a crowded street,
and you take a hasty glance in both directions, to make sure of a
safe passage. Now your attention is caught, for a moment, by the
contents of a shop window ; and you pause, though only for a
moment, to survey the window before you actually cross the street.
Paramnesia would then appear as the feeling that you had already
crossed ; the preliminary glance, which naturally connects with
the crossing in a single, total experience, is disjoined from the
crossing, through the abnormal weakness of the associative ten-
dencies, and comes to consciousness separately as the memory of
a previous passage. As you cross, you think, ' Why, I crossed this
street just now ; ' your nervous condition has severed two phases of
a single consciousness ; the one is referred to the past ; and the
other, under the regular laws of memory, arouses the feeling of
familiarity.
The same weakening of the associative tendencies may bring it
about that a familiar, meaningful word stands out as novel and
meaningless. The experience is very unpleasant ; but it loses its
strangeness if we synthetise it experimentally. Repeat a word
over and over again, with sustained attention to the auditory-kin-
aesthetic complex. The word soon becomes meaningless ; the
direction of attention has given a sort of hypnotic narrowness to
consciousness, the associative context of the word is cut off, and
the bare perception remains.
This loss of meaning, once more, may appear on the grand scale
in the Etate known as depersonalisation. There are moments of
unusual depression or lassitude or fatigue, when the whole world
about us seems new and strange, though rather negatively than
426 Memory and Imagination
positively, — new and strange as a shadowy dream-world, where
things are pictures, and men are pictured automata, and we hear
and contemplate our own voice and action as foreign and indif-
ferent spectators. Here the normal context and the normal feel-
ing of familiarity are entirely lacking j the kinaesthetic and other
organic reactions have lapsed j the cortical set that adjusts us to
a world of external reality has disintegrated. We know nothing
in detail of the physiological conditions of depersonalisation, but it
is evidently related to the apparently opposite phenomenon of
false recognition.
Other illusions of memory, which follow naturally from the
course of the image and the structure of the memory conscious-
ness, need not here be specified.
References for Further Reading
§§112-120. H. Ebbinghaus, Psychologies i., 1905, 633 fF. ; W.
Wundt, Physiol. Psychol., iii., 1903, 581 if., 628 ff. ; Die Kimst, 1908.
§ 112. On the course of the image, J. Philippe, Sur les transforma-
tions de nos images mentales, in Revue philosophique, xliii., Mai 1897,
481 ff. On the memory after-image, G. T. Fechner, Elemente der Psy-
chophysik, ii., 1907, ch. xliv. {b). On perseverative tendency, G. E.
Miiller and A. Pilzecker, Experimetitelle Beitrdge zur Lehre vom
Gediichiniss, 1900, 58 ff.
§ 114. F. Galton, Inquiries into Hufuati Faculty and its DevelopH
ment, 1883 (reprinted as no. 263 of Everyman's Library) ; E. B.
Titchener, Experimental Psychology, I., ii., 1901, 387 ff . ; A. Eraser,
Visualisation as a Chief Source of the Psychology of Hobbes, Locke,
Berkeley and Hume, in American fournal of Psychology, iv., 1891, 230 ff.
§ 115. E. A. McC. Gamble and M. W. Calkins, Die reproduzierte
Vorstellung beim Wiedererkennen und beim Vergleichen, in Zeits. f.
Psychol., xxxii., 1903, 177 ff. ; xxxiii., 1903, 161 ff.
§ 117. Cf. a series of articles by F. Kuhlmann, in American Journal
of Psychology, xvi., 1905, 337 ff. ; Psychol. Rev., xiii., 1906, 316 ff. ; Journ.
Philos. Psychol. Sci. Meth., iv., 1907, 5 ff. ; American Journal of Psy-
chology, xviii., 1907, 389 ff. ; xx., 1909, 194 ff.
§ 118. References to current investigation, and an account of the
experiments upon which this Section is chiefly based, wiU be found
in an article by C. W. Perky, Atnerican Journal of Psychology, y.yi\., 1910,
4.22 ff. On secondary sensations, see B. Sidis, Psycho^- Rev., x-- 1908,
References for Further Reading 427
44 ff., 106 ff. On centrifugal sensory conduction-paths, W. Wundt,
Frinc. of Physiol. Psychol.., i., tr. 1904, 151, 159, 182, 184, 186, 189.
§ iig. T. Ribot, Essay on the Creative I/nagijiatiofi, tr. 1906;
E. Lucka, Die Phantasie, eine psycliologische Untersuchmig, 1908.
§ 120. G. Heymans, Eifie Etiquete i'lber Depersotialisation und
' Fausse Reconnaissance^ in Zeits. f. Psychol. ., xxxvi., 1904, 321 ff . 5
xliii., 1906, I ff. ; J. Linwurzky, Zmn Problem des falschen IVieders
kennens {deja vit), in Arch. f. d. ges. Psychol.., xv., 1909, 256 ft>
ACTION
§ 121. The Reaction Experiment. — In the year 1796,
the astronomer in charge of the Greenwich Observatory ^
found himself obhged to dismiss an otherwise competent
assistant, who, in the preceding year, had fallen into the
habit of recording stellar transits some half second too
late, and had now increased his error to almost a whole
second. The assistant disappeared ; but the error, after
passing without further notice for a quarter of a century,
became the topic of prolonged scientific discussion, and as
the 'personal difference ' or * personal equation ' gave rise
to the psychological study of reaction times.
A reaction, in the technical sense in which we are here
using the term, is a movement made in response to an
external stimulus. A simple reaction is a movement made
in direct response to such a stimulus. In the reaction
experiment, we subject the observer to some prearranged
form of stimulation (say, a flash of light), to which he has
to reply by some prearranged movement (say, the sHpping
of the forefinger from the button of a telegraph key).
Instruments are employed which permit us to measure the
time elapsing between the exhibition of the stimulus and
the performance of the answering movement. This time
is named the reaction time, and, in the case of direct
response, the simple reaction time.
The experiment may be made more complicated, both
^ N. Maskelyne, Astronomical Observations made at the Royal Observatory
at Greettwick, 1795, pt. iii., 339.
428
§ 121. The Reaction Experiment
429
on the side of stimulus and on that of mode of reaction.
We then have various forms of compound reaction, with
the corresponding compound reaction times.
The passage of a star across the meridian was formerly deter-
mined by means of the eye and ear method. The field of the
telescope is divided up, let us say, by five fine w^ires, set vertically
and at equal distances. The middle wire corresponds to the
meridian. Before putting his eye to the instrument, the observer
reads off the time from a clock, and then counts the beats of the
pendulum as he watches the progress of the star. He notes its
position at the last beat before, and the first beat after, it crosses
the middle wire, and thus estimates the time of the actual cross-
ing. Thus, if the star is at a when the
twelfth beat is counted, and at b when the
thirteenth is counted, the time of transit,
estimated in tenths of a second, will be
so many hours, so many minutes, 12.7
seconds.
It is in estimations of this sort that the
personal difference appeared. The phrase
'personal equation ' arose from the custom-
ary statement of the difference in com-
parative terms. Thus, A — B^= 0.8 sec. means that the observer
A records a transit, on the average, 0.8 sec. later than observer B.
Here the one observer, probably the more skilled of the two, is
made the standard of reference for the other. The equation evi-
dently has only a relative value ; the magnitude of ^'s error is not
determined.
The discussion of the personal difference led directly to the
experiments on accommodation of attention described in § 83.
It also led, indirectly, to the experiments on reaction time. For
these may be regarded as absolute determinations of the error of
the observer : MA responds to the flash of light in 290 o- (i a- =
ToVo sec), and ^ in 180 o-, then we may not only write A—B =
iioo-, which expresses the personal equation, but may also say,
absolutely, that A and B have postdated the flash of light by the
•
h
»
X
S\v
^\
*
Fig. 61.
430
Action
amount of their respective reaction times. Nor are we bound to
the technique of the experiment as it is given in the text ; the con-
ditions of astronomical observation may be exactly repeated ; an
artificial star may register its own passage across the hne of the
meridian, and the observer may react as he would do in the case
of a real transit, recorded
by the eye and ear method.
We cannot here trace
the history of the reaction
experiment. It must suf-
fice to say that, as astronomy
perfected its own methods,
the experiment passed into
the service of physiology,
and was used for the deter-
mination of the velocity of
the nervous impulse. The
assumption was, in the
rough, that if two parts of
the body, at different dis-
tances from the brain, are
stimulated in the same way,
and the reaction times com-
pared, the difference in
these times will correspond
to the difference in the
length of the sensory nerve-
trunks involved, and will
thus show the rate of af-
ferent nervous conduction.
Fig. 62. Hipp's Chronoscope, an electrical
clock whose unit is i <r : commonly em-
ployed in the reaction experiment.
It was found, however, that the method was not suited to the
problem. The experiment was then transferred, as a quantitative
experiment, to the psychological laboratory, and was employed,
in various forms, to measure the duration of certain mental
processes. But psychology knew so Httle of the mental pro-
cesses comprised within the reaction time, that the assignment
§ 121. The Reaction Experiment
431
of duration was altogether speculative. And so the experiment
has now come to be, in essentials, a qualitative experiment. It
allows us to repeat, over and over again, a particular type of con-
sciousness ; it allows
us to vary this type,
in manifold ways, and
still to repeat our ob-
servations as often as
is necessary to their
Fig. 63. Wundt's Sound Hammer, often used as complete analysis ' it
stimulator in the reaction experiment. The wires of , ff A ' A '
the chronoscope circuit are led to the posts i, 2; the ^nUS attords an admi-
posts 3, 4 of the electro-magnet are in connection with rable COntrol of intro-
a separate battery and key. Spection. The reac-
tion times are then valuable, not in themselves, but as checks upon
the observer. If the times of simple reaction to light are, for
two normal observers and under the same conditions, 290 cr and
180 o- respectively, it is clear that we are dealing with different con-
sciousnesses ; the observers are not doing the same thing. To
find out, by variation of conditions, precisely what they havi?
been doing is a psychological problem of considerable impor-
tance, —
The technique of the reaction experiment is described in thi?
manuals of laboratory practice, and need not here be repeated.
The necessary instruments are a stimulator, a reaction key, and
some form of time-measuring apparatus. Stimulators have been
devised which set up a sensation in the various departments of
sense, which exhibit more complex stimuli (words, geometrical
Fig. 64. Finger Key, modelled upon the ordinary telegraph
key : commonly used as break-key in the reaction experiment.
432
Action
figures), and which give a succession of varying stimuli (colours,
noises of different intensity). Keys have been constructed foi
movements of the finger, foot, lips, throat, eyelid, and for selec-
tive responses, e.g., for movement for any one of the ten fingers.
The time-measuring apparatus ranges from the stop-watch, whose
unit is \ sec, through instruments of increasing accuracy, up to the
electrical chronoscope, whose unit is i o-.
§ 122. The Analysis of the Simple Reaction. — In 1887 and
1888, two investigators made the independent discovery
that the length of the simple reaction time differs, according
as the attention of the reactor is directed to the stimulus
which is to release the reaction movement, or to that move-
ment itself. Since the latter date, it has been customary to
distinguish three types of simple reaction : the sensory, the
muscular, and the mixed, — this last representing the nat-
ural attitude of a reacton whose attention is fixed prepon-
derantly neither upon sensory stimulus nor upon movement
of response, but is either distributed more or less evenly to
both, or turns in quick succession from the one to the
other.
The approximate times for the two extreme modes of reaction
are as follows (time-unit = i o-) : —
Muscular
Sensory
Light
Sound .....
Electrical cutaneous stimulus
180
120
105
290
225
210
The range of variation (p. 211) is, for moderately practised reac-
tors, about jIq of the total sensory time, and about -^ of the total
muscular time. The times for warmth and cold are largely depend-
ent upon the conditions of the experiment. We may say, however,
that on a rough average those for warmth approximate the times
§ 122. The Analysis of the Simple Reaction 433
for light, and those for cold the times for sound. The times for
taste, smell and pain have not yet been standardised. The times
of the mixed reaction lie between those of the extreme forms,
tending to be longer or shorter according as the predisposition of
the observer or the circumstances of the experiment tip the scale
of attention on the side of stimulus or of movement.
The distinction of the three types of reaction is valid.
But analysis has shown that the phrase ' direction of
attention ' is ambiguous. The course of consciousness
depends entirely upon the attitude which the reactor takes
to the experiment ; and this attitude depends upon his
understanding of the instruction given by the experimenter.
Evidently, then, the instruction must be clear-cut; it must
limit and restrict as well as positively command. If I say
to the reactor : ' React as soon as you see the white card ;
keep your attention, all through, upon the card ; never
mind about the movement, but let that follow of itself '
— if I say this, I have given instruction for the sensory
type of reaction. Nevertheless, the instruction is am-
biguous. For the words * as soon as ' have suggested to
the reactor that he is to react as quickly as possible ; and
if he reacts as quickly as possible, he will tend to slur
the perception of the white card, and to react upon the
least perceptive cue. As the experiments proceed, he will
tend, also, to prepare more and more completely for the
responsive movement : and so, simply through the fault of
instruction, he will shift from the sensory to the muscular
form of reaction. If, again, I say to the reactor : ' React
as soon as you see the white card ; but keep your atten-
tion, all through, upon the movement,' my instruction is
ambiguous in the opposite way. The words ' as soon as '
suggest that the reaction is to follow as quickly as possible
3F
434 Action
upon the appearance of the stimulus, but the phrase
' attend to the movement ' may negative that suggestion ;
the reactor, instead of getting the movement ready, may
try to hold it clearly in consciousness, and so the response
may be delayed.
It follows that the instruction must be very carefully
worded ; it must be brief, in order that it may be grasped
as a whole; yet it must be explicit, both as to what the
reactor is to do and as to what he is not to do. Moreover,
it must be repeated, over and over, as the experiment
proceeds, in order that the mode of reaction may not
change, without the reactor's knowledge or intention, from
one type to another.
The reaction experiment, as a psychological unit, may be
divided into three periods : the fore-period, extending from the
prehminary signal to the exhibition of the stimulus ; the mid-
period, extending from the appearance of the stimulus to the
performance of the reaction movement ; and the after-period,
following upon the movement, during which the reactor makes
his introspective report. The fore-period is dominated by the
instruction, which may come to consciousness in very various
ways. Our analyses are still far from complete ; we must often
be content, as in the description of memory and imagination,
barely to indicate some elusive and time-worn process, whose
observation demands special conditions ; but the following account
will suffice for a general understanding of the reaction conscious-
ness.
We begin with the muscular reaction. In its extremest form,
the instructions are represented, simply and solely, by kinaes-
thetic (principally strain) sensations in the reacting member (prin-
cipally in the finger). These sensations appear as a contextual
complex, which carries the meaning ' You are to react as quickly
as possible ' ; they have been termed, accordingly, ' sensations of
intended movement.' . This restriction of consciousness, to the
§ 122. TJie Analysis of the Simple Reaction 435
apprehension of the stimulator and a kinaesthetic context, is rare.
In the typical form of the muscular reaction, the sensations of
intended movement are again prominent. But there are also
present a conscious reference to the expected stimulus (carried by
fixation of the stimulator), and a conscious connection of the
expected stimulus with the intended movement. In another form,
the kinaesthetic sensations are replaced by some imaginal process :
a visual image of the moving finger, the word ' movement ' in
internal speech ; while there is still a conscious reference to the
expected stimulus. In a fourth form, kinaesthetic sensations and
internal speech are both in evidence, but the reference to the
expected stimulus may be so clear as to approximate the sensory
type. Lastly, the kinaesthetic sensations and the reference to
stimulus may be accompanied by ' as quickly as possible ' in inter-
nal speech : the reactor intends to make the movement, as
nearly as he can, simultaneous with the appearance of the stimulus.
In the extremest form of the sensory reaction, the instructions
are represented, simply and solely, by the expectation (without
image) of the coming stimulus. This restriction of consciousness,
to the apprehension of the stimulator and an expectation context,
is rare. In the typical form of the reaction, expectation of
stimulus is combined with a conscious reference to the intended
movement ; there are, however, no sensations of intended move-
ment. In another form, the expectation takes imaginal shape as
a visual image of the stimulus, or ' now it's coming ' in internal
speech. The conscious reference to the intended movement is
again present, but there are still no sensations of intended move-
ment. In a fourth form, the expectation and the conscious refer-
ence are accompanied by kinaesthetic sensations in the reacting
member, around the eyes, etc. ; here is an approximation to the
muscular type. Lastly, the expectation and the reference may be
given together with ' as quickly as possible ' in internal speech :
the reactor intends to make the movement, as nearly as he can,
simultaneous with the appearance of the stimulus. Sometimes
this temporal set is represented by the visual image, e.g., of a
swinging pendulum.
436 Action
Both kinds of instruction may, on occasion, set up conscious«
nesses of the pattern which they are designed to prevent : the
muscular instruction may prompt to a sensory preparation, the
sensory to a muscular. So flagrant a miscarriage of instruction is,
of course, rare ; that it occurs at all is sufficient proof of ambi-
guity. Since, in fact, it is not a simple ' direction of attention ' that
differentiates the reactions, but the reactor's attitude as conditioned
on instruction, we may drop the names ' sensory' and ' muscular' al-
together, and substitute for them the purely descriptive terms 'com-
plete ' and ' abbreviated.' The correct instruction for the abbreviated
form would then run somewhat in this way : ' You will see a white
card ; react as soon as you see it ; react as quickly as possible.'
For the complete form : ' You will see a white card \ react when
you see it ; do not react till you see it clearly.' And for the
natural form : ' You will see a white card ; react when you see it.'
The first instruction definitely suggests the preparation of the
responsive movement ; the second as definitely suggests the clear
perception of the stimulus, while it heads off the auto-sugges-
tion that the movement is to be made as quickly as possible ; the
third leaves the reactor to his own devices.
When the course of consciousness has once been deter-
mined, by the reactor's acceptance of the instruction, the
experiment proceeds smoothly to its conclusion. It has
been suggested that the sensory reaction breaks apart;
that, after the apprehension of stimulus, there is a distinct
conscious impulse to move the finger ; whereas, in the
muscular reaction, the movement follows directly upon
the perception. Introspection shows, however, that this
sundering of the reaction consciousness occurs, if at all,
only in the earliest stage of practice ; as a rule, the finger
moves as directly in the sensory as it moves in the muscu-
lar type of experiment. The difference between the two
reactions is rather this : that, in the sensory, the stimulus
is apprehended in its proper quality, as ' something white,'
§ 123- Compound Reactions 437
and that, in the muscular, it is apprehended merely as a
visual stimulus of indeterminate quality or, still more
baldly, as ' something different.' The physiological condi-
tions of this difference can only be guessed at.
The reinstatement, in the few minutes of the after-period, of the
consciousness of the two preceding periods, has been ascribed to
the operation of perseverative tendencies. We have seen, how-
ever, that the assumption of these tendencies is unnecessary
(p. 400).
The simple reaction experiment can be varied in many ways.
Thus, we may investigate the influence of intensity and quality of
stimulus, of variation of the time allowed for accommodation of
attention, of the omission of a preliminary signal, of the presence
of distracting stimuli, of fatigue, of drugs. Unfortunately, the main
emphasis in all this work has been laid upon the time of reaction.
Since we have temporal norms for the three most accessible sense-
departments (p. 432), and since our psychological analysis of the
sensory and muscular reactions affords a general survey of the
reaction consciousness, it is possible, by comparison of results, to
estimate the effect of the changed conditions and also to trace,
with some degree of probability, the changes in consciousness
itself. Here as everywhere, however, we are bound, sooner or later,
to face the psychological problem in detail, to push our special
analyses to the bitter end. For the past two thousand years, psy-
chology has been resting upon plausibilities and probabilities.
Now that we are beginning to have a psychology of facts, it is both
honesty and policy to state where the facts end and where specu-
lative construction begins.
§123. Compound Reactions. — The simple reaction ex-
periment may be most easily complicated by substituting
for the single stimulus a number of similar stimuli. The
reactor is told, for instance, that he will be shown either a
black or a white card, and that he is to react when he has
apprehended the white as white or the black as black ; he
438 Action
does not know which of the two qualities will be presented
in any given experiment. Or he may be told that he will
be shown a black, white, grey, or coloured card, and that
he is to react when he has apprehended the particular
stimulus in its proper quality. The first of these is termed,
technically, the discriminative reaction, on the ground that
the reactor discriminates between the two known stimuli.
The second is known as the cognitive reaction, on the
ground that the reactor directly apprehends — cognises
rather than recognises ^ the quality of the unknown stim-
ulus. In fact, however, the reactor's attitude, under the
two forms of instruction, is essentially the same.
In the fore-period of the discriminative reaction, the reactor's
coiisciousness consists, primarily, of the perception of the stimula-
tor and of the intention to wait, to give the stimulus full time.
Sometimes the names of the stimuli * black, white ' appear in in-
ternal speech ; sometimes the intention is itself carried in verbal
terms, — * black, white ; make sure ; react.' In the mid-period,
the clear apprehension of the stimulus may be attended by a feel-
ing of assent or acknowledgment, as well as by the assurance that
the finger may now be moved; or the two processes may run to-
gether, as the assurance that this is the thing that was expected
and that was to be reacted upon : movement then follows at once.
In the fore-period of the cognitive reaction, consciousness
again consists, primarily, of the perception of the stimulator and
the intention to give the stimulus full time ; sometimes, however,
there is diffused strain about the eyes and the upper part of the
body, and a repetition of the instruction in internal speech, — ■
' grey, colour ; react quickly.' In the mid-period, the clear ap-
prehension of the stimulus may bring with it the feeling of assent,
with or without the specific name of the light or colour in inter-
nal speech ; or a stimulus may be apprehended — in the precise
terms of the instruction — as 'coloured' ; or, again, it may be ap-
prehended as the thing to react upon ; or, finally, towards the end
§ 123- Compound Reactions 439
of a series, as that familiar thing. Here, as in the discriminative
reaction, movement follows at once upon this complex apprehen*
sion. The two modes of reaction may evidently be bracketed
together.
Another method of complicating the simple reaction ex-
periment is to vary the responsive movement. Thus, the
reactor is told that he will be shown either black or white,
and that he is to react only when he has apprehended the
black as black or the white as white. So far the instruction
is the same at that for the discriminative reaction. But
further, he is to react to black by a movement of the right
hand, and to white by a movement of the left hand. Or,
he is to react to black by a movement of the right hand,
but is not to react to white at all.
Once more : the reactor is told that he will be shown a
light or a colour, and that he is to react only when he has
apprehended its specific quality. So far, the instruction is
the same as that for the cognitive reaction. But further,
he is to react by naming the perception : that is, the re-
sponsive movement is to be different for every stimulus.
Or, he is to react to the colours by naming them, but is
not to react to the lights at all.
All these forms are termed, technically, choice reactions,
on the ground that the reactor is called upon to make a
choice, either between two different movements, or between
movement and quiescence. In fact, however, the observer's
attitude, under the two forms of instruction, may be widely
different, and it is more than doubtful if either instruction
arouses the process of choice.
It is. again, unfortunate that investigators have so far been con-
cerned rather with the recording of times than with an analysis of
44^ Action
the reaction coilsciousness. The times themselves have been ob-
tained under varying experimental conditions, so that their norma
cannot be stated. The analytical material is very scanty.
In a series of cognitive choice reactions (white to be reacted
upon, other stimuh to be disregarded), the fore-period opened
with the words ' react to white ; make sure ' or ' right away ; react
to white ' in internal speech ; the word ' white ' carried the mean-
ing * white and nothing else.' Later, the fixation of the stimulator
set up intensive strains about the eyes, and the instruction was
present to consciousness only as a general intention. If the white
stimulus appeared, the mid-period showed a brief pause, culminat-
ing in the reactor's assurance that ' that's what I was waiting for,'
or ' that's white all right,' whereupon the reaction movement fol-
lowed at once. If some other stimulus appeared, its apprehen-
sion might connect directly with the assurance that it was not to be
reacted upon; then the reactor took it quite quietly. Or — if the
card was a printed card, with a white ground — sensations of in-
tended movement might arise at the first glimpse of white, to be
inhibited later, by a stronger pressure on the key, when the letters
came into view.
In a series of discriminative choice reactions (visual or auditory
presentation of vowels or consonants, each one of which is corre-
lated with movement of a particular finger), the fore-period showed
two main forms of conscious preparation, the sensory and the
associative. The purely sensory preparation consists in attentive
perception of the stimulator, with definitely directed (but image-
less) expectation. This simple disposition of consciousness may
be complicated either by sensations of intended movement in arms
and fingers, or by the appearance of a complex visual image, a
sort of monogram of the letters used as stimuli. If the reactor
has not already practised the correlation, his preparation is associa-
tive : there is repetition of the instructions in internal speech, ' E
right, O left.' Consciousness may again be complicated, either
by visual images, or by sensations of intended movement. It is
noteworthy that these kinaesthetic sensations may appear, with the
meaning ' right ' and ' left,' not only in the corresponding arm and
§ 123- Compound Reactions 441
fingers, but also about the eyes. We have seen that they do not
necessarily lead to movement ; we now find that they are not con-
fined to the reacting member. They are, of course, the sensations
which have often been described as sensations of innervation (§ 49) .
In the mid- period, the unpractised observer first apprehends
the stimulus, then repeats the fitting instruction (' right,' * left,' etc.)
in internal speech, and then reacts in reponse to this associated
idea. As practice advances, the associative term drops out of
consciousness. Nevertheless, the reaction does not, for a long
time, follow directly upon the apprehension of the stimulus ; there
is, as the reactors put it, a certain resistance to be overcome before
the movement can be made. This resistance has not been
adequately described ; Wundt regards it as a phenomenon of motor
inhibition. The movement itself is, as we said above, frequently
prepared for by the sensations of intended movement, which some-
times last over into the mid-period. They are especially marked if,
at the moment of apprehension of the stimulus, there is a tendency
to move the wrong finger ; they are then characterised as an
urgency or impulse to move in a certain way. The stimulus, how-
ever, touches off the right movement, without arousing a second
kinaesthetic complex in the correlated finger. —
A word must now be said with regard to the sensations of in-
tended movement. We have called them kinaesthetic sensations ;
they appear in consciousness as a mode of kinaesthesis ; often-
times they are referred to organs whose muscles are obviously in
contraction. But there is something to be added. Their inten-
sity may be out of all proportion to the degree of actual muscular
contraction ; they may be referred to a muscle-group which, at
the time, is sensibly quiescent, and whose later contraction sets
up kinaesthesis of a distinguishably different kind. When they
occur about the eyes, the observers insist that they are intro-
spectively different from the kinaesthetic sensations of attentional
adjustment (§ 78). Their place may be taken, in the reaction
consciousness, by imaginal processes, by visual images or internal
speech. It looks, then, as if they were themselves, at least in part,
images rather than sensations, but images of that stable sort which
442 Action
may be confused with sensations. We cannot here appeal to cen-
trifugal sensory paths (§ 1 18) ; but we may, following Wundt, make
the following tentative hypothesis regarding their central origin.
Consider, first, the ordinary mode of arousal of kinaesthetic
sensations. A motor centre sends out excitations to the peripheral
motor apparatus with which it is connected ; the changes thus set
up at the periphery stimulate the kinaesthetic organs ; excitations
proceed from these to the correlated sensory centres ; sensation re-
sults. Now suppose that the motor centre stands in direct functional
connection with the sensory centres. The excitation, instead of
taking the roundabout path to the periphery and back again, may
take the straight path from motor to sensory centre ; the periph-
eral apparatus need not be disturbed. But the sensory centre,
accustomed to respond to excitation by kinaesthetic sensation,
will do so under the conditions of this direct excitation \ kinaes-
thesis, of the stable sensory kind, will appear in consciousness.
Ordinarily, the roundabout and the direct paths are both traversed
by excitatory processes ; in the case of the sensations of intended
movement, only the direct path need be involved.
It must be clearly understood that the names given to
these compound reactions — discriminative, cognitive, choice
— are merely conventional. Discrimination and choice re-
fer to the external arrangement of the experiment, and to
that alone ; in the discriminative reaction we do not dis-
criminate, in the choice reaction we may do various things,
but we do not choose. Cognition, direct apprehension, is
implied in all reactions, simple and compound alike ; even
in the muscular reaction we cognise 'something different.'
The names were given, speculatively, at a time in the his-
tory of psychology when experiment was new and analysis
still a matter for the future. They have persisted, as
names will; it is as difficult to dispossess them as it is to
banish the terms ' active ' and ' passive ' from the doctrine
of attention ; but the reader must take them simply ^%
§ 123. Compound Reactions 443
labels for certain historical forms of the reaction experi-
ment, not as psychological rubrics.
Everything depends, we said above (p. 433), on the attitude
which the reactor takes to the experiment ; and this attitude itself
depends on his understanding of instructions. We must now add
that the carrying out of instructions, as understood, depends upon
practice ; the time of an elaborately planned choice reaction may,
if the coordination of stimulus and movement has been sufficiently
practised, be the same as that of the simple sensory reaction. It
follows from these considerations that the compound reactions are
not built up, piece by piece, from the simple ; the discriminative
and cognitive reactions are not sensory reactions 'zngthened by the
times of discrimination and cognition ; the choice reactions are
not discriminative reactions lengthened by the time of choice. In
other words, we cannot derive the time of discrimination by sub-
tracting the sensory from the discriminative reaction time, or the
time of choice by subtracting the discriminative from the choice
reaction time. This procedure is often followed ; the times of
discrimination, cognition, choice are often to be found in the text-
books ; but there is, in fact, no truth in the underlying assumption
that the reaction is a chain of separate processes, to which separate
links may be added at will ; the reaction is a single conscious
event, conditioned as a whole upon the understanding of instruc-
tions at a given stage of practice.
A third way of complicating the simple reaction experi-
ment is to connect the responsive movement, not directly
with the stimulus, but indirectly with some associated idea
aroused by the stimulus. Thus, the reactor may be told
that he will be shown a printed word, and that he is to re-
act by pronouncing the first word suggested to him by the
stimulus (free association). Or he may be instructed to
reply in a more definite way : by naming a subordinate
idea, an instance that would fall under the stimulus-word ;
or a coordinate idea; or a superordinate idea, a class of
444 Action
which the object denoted by the stimulus-word is a mem-
ber ; by associating part to whole, attribute to object, effect
to cause, and so on (partially constrained associations).
Or, finally, he may be instructed to reply still more defi-
nitely : to give the Latin equivalents of the English
words shown, to name the capital cities of the countries,
and so forth (constrained associations). It is clear that
any phase of the associative consciousness may, by a
fitting arrangement of the experiment, be represented in
terms of objective or physical time. The reaction times
have proved to be valuable both scientifically, as indi-
cating the strength of associative tendencies, and also
practically, as indicating the existence of associative con-
nections which the reactor desires to conceal. Observation
of the reaction consciousness has also thrown welcome
light on the process of thought.
It would seem that here, if anywhere, the subtractive procedure
is allowable ; that we might, with a high degree of probability, de-
termine the time required for association by subtracting the simple
sensory from the associative reaction time. The facts are other-
wise. The instruction to associate dominates the whole course
of consciousness, and the two reactions are therefore incomparable.
The fore-period of the associative reaction shows the characters
with which we are already familiar : attentive fixation of the
stimulator, a high degree of expectation (strain sensations about
the eyes and forehead and in the upper part of the body, together
with holding of the breath, compression of the lips, etc.), and a
representation of the instructions, usually in verbal form. The
reactors also report a variety of emotive attitudes — curiosity,
difficulty, impatience, coolness in the emergency — which we
may ascribe to the meaningful nature of the stimuli. The mid-
period of the reaction shows the characters that we have enumer-
ated in §111, though it shows them with differences. Here, e.g.,
the observer stands under the pressure of the coming reaction,
§ 123- Compound Reactiotis 445
so that the course of consciousness is hurried and its processes
are crowded together. From one point of view, this disposition
of consciousness is a disadvantage ; there is too much material
and there is too little time for adequate introspection ; the re-
actor falls into the way of indicating or naming large complexes
that he is unable to describe. From another point of view, how-
ever, it is a distinct advantage. The observer who works under
the conditions of §111 has plenty of time for analysis, and reports
his consciousness in analytical terms ; there is a chance that he
fail to see the wood for the trees. The observer in the associa-
tive reaction, since he has no time to describe the trees, must be
content to indicate clumps and coppices ; but by this very limita-
tion he calls our attention to the fact that there are clumps and
coppices, unitary complexes of manifold degrees and patterns ;
and these, once indicated, can be taken up for analysis under
more favourable conditions.
The most important facts revealed by the associative reaction
are, perhaps, those that bear upon the reactor's attitude to in-
struction. In the first place, the instruction, clearly conscious at
the outset, presently drops out of consciousness altogether, and
thenceforward directs the course of mental processes as an uncon-
scious nervous disposition. This is, in fact, the fate of all instruc-
tions — of all suggestions, commands, cues, directions, prescriptions
— to which we make habitual response (pp. 274 f.). Secondly,
the instruction, if given vaguely and in general terms, is specialised,
narrowed by the reactor. Though he is told to reply by the first
word that crops up in his mind, he will draw his associates from
those that make sense with the stimulus-word ; if a meaningless
associate appears, he will reject it in favour of a word whose
meaning connects it with the stimulus ; he has interpreted ' first
word ' as ' first sensible word.' Though, again, he is told that sub-
stantives will be shown, and that he is to reply by the first adjec-
tive that occurs to him, he will reply only by suitable adjectives ;
' first adjective ' becomes 'first fitting adjective.' It is as if we
were set, or adjusted, for a world of sense, just as we are set or
adjusted for a world of objective reality ; to talk and think
446 Action
nonsense is far less easy than we are apt to imagine. And, thirdly,
— - a point of great methodological interest, — the instruction to
observe, to attend and report (§ 6), is eminently favourable to the
review of consciousness in the after-period. If the old objection
held, that introspection necessarily interferes with the very pro-
cess that we are trying to observe, the observer who lay under the
double instruction to associate and to introspect would be divided
against himself; he would associate hesitatingly, and he would
observe interruptedly. As a matter of fact, the two instructions
run together, and the observer sets himself to associate as atten-
tively and single-mindedly as he can, with the result that the
course of events is clearly apprehended, and finds ready expres-
sion in words.
It has been found, in work with nonsense syllables, that those
pairs have the quicker association times whose associative tenden-
cies are the stronger and more durable, — whence it follows that,
other things equal, the length of the associative reaction is an in-
verse measure of the strength of associative tendency. There is
one case, where other things are decidedly not equal, in which
this rule shows a very conspicuous breach. It has been found in
work with ordinary verbal associations that, if the stimulus-word
touch off what is technically called a ' complex,' either that particu-
lar reaction or the next following will show a decided lengthening.
A ' complex,' in this special meaning, is the impression left upon
the organism by some strongly emotive experience ; it is a group
of impressional and associative tendencies, which may or may not
find present representation (general or partial) in consciousness,
but is readily actualisable if it is not at the moment consciously
actual, and whose correlated ideas tend on arousal to become
focal, and to reinstate the emotion of the original experience. If,
e.g., I have done something of which I am ashamed, and if the
stimulus- word touches off the complex of this ' deed of which I am
ashamed,' then my reaction time is lengthened. This discovery
is evidently of practical value, though a complete statement of the
facts would require a great deal of conditioning and qualifying for
which we here have no space.
§ 124. Action 447
In experiments of still greater complexity, the responsive move-
ment may follow, not upon an associated idea, but upon a judg-
ment of comparison, a literary appreciation, etc. Here, however,
the times become extremely variable, and have little significance ;
the reaction experiment loses its distinctive character, and is
merely a convenient setting for certain exercises in introspection.
§124. Action. — In the early days of the reaction experi-
ment, there was little said of its psychological status, of its
place in a system of psychology. The experiment was
useful as measuring the objective duration of certain men-
tal processes ; but it thus appeared as a means, not as an
end. Since it plainly involved a sequence of perceptions
or ideas, — since the perception of one's own movement
followed on that of the stimulus, or followed on an idea
associated to the perception of stimulus, — it might be
treated in the same chapter with association, and might
be considered as a form of successive association. That
settled, the writer's attention was directed to the times,
not to the preparation and content of the reaction con-
sciousness. Hence we have historical precedent for intro-
ducing the reaction, without psychological preface, simply
as one of the classical experiments of experimental psy-
chology. But we have not discussed reaction times ; we
have discussed the reaction. And now the question arises ;
What, psychologically, is this reaction }
The answer, obvious as it is, was given only in the early
nineties of the last century, and still has a good deal of
prejudice to overcome. The reaction is an action ; it be-
longs to the same group of facts as reflex action, voluntary
action, instinctive action. It is an action reduced, in the
simple reaction experiment, to skeleton form ; and it is an
artificial action, made up for study under experimental con-
448 Action
ditions. But it is still an action, and the consciousness
which we have found to characterise it is an action con-
sciousness.
In its most general meaning, an action is an organised
movement ; less generally, it is a movement of a locomotor
organism ; for psychological purposes (p. i6), it is prima-
rily a human movement with some sort and degree of
representation in consciousness. The qualifying words
* some sort and degree ' are used advisedly ; for the action
consciousness is one of the most changeable and variable
that we know ; nowhere, perhaps, is psychology more
plainly dependent upon physiology for the coherence and
continuity of its descriptions (p. 40). If, however, on the
ground of the foregoing analyses, we try to construct a
typical action consciousness, we get something like this :
a preliminary phase, in which the prominent things are
kinaesthesis and the idea of end or result ; a central phase,
in which some object is apprehended in relation to, in the
sense of, the idea of end ; and a final phase, in which the
perception of result is set on a background of kinaesthesis,
of the sensations aroused by the actual movement. Each
one of these phases may be coloured by feeling, which may
itself be of either quality, pleasant or unpleasant, and of
any degree of sensory or imaginal complexity.
The first phase corresponds to the fore-period of the reaction
experiment. The kinaesthetic contents are, in the main, the sen-
sations of intended movement ; there may also be kinaesthetic
sensations from actual, anticipatory movements, and there may
possibly be kinaesthetic memories. The idea of end, or idea of
result, takes the place of the conscious representation of instruc-
tion in the reaction consciousness ; it may be carried in visual
images, in internal speech, etc. The second phase corresponds to
§ 124- Action 449
the mid-period, in which movement is released, in the sense oi
the instruction, on the perception of the stimulus (perception of
object). The third phase differs from the introspective after-
period ; the perception of result, with its kinaesthetic halo, is at
once the terminus of the action consciousness and the starting-
point of some new consciousness, emotive or other.
The characteristic feature of the action consciousness, as
distinguished from the consciousnesses so far considered, is
its predetermination in the sense of the idea of end. The
presentation of the object arouses associative tendencies in
the usual way ; but only those tendencies are realised which
lie in the line of suggestion, of the meaning of the idea of
end. We translate this fact into physiology by saying that
the excitatory processes underlying the idea of end set up
determining tendencies ; they open certain nervous chan-
nels, as it were, and close others ; so that the consequent
excitations find their path laid out for them. Determin-
ing tendencies thus take their place alongside of impres-
sion and of associative tendencies as nervous correlates of
consciousness. We know nothing of their intimate nature ;
but we have ample evidence of their existence, and we name
them as best we may. They are nervous coordinations and
integrations, in part common to the race and transmitted
from one generation to another, in part acquired in the in-
dividual lifetime, either by way of habit or under stress of
some salient experience. Their influence is by no means
confined to the determination of action, though here, where
they find direct physiological expression in a bodily move-
ment, it is most easily observed and traced.
We are now able to give a definition of the term * suggestion.'
It is not difficult to find a paraphrase : a suggestion is an instruction,
something that comes to us with the force of a command. But
2a
450 Action
psychologists have always found it difficult to frame a definition,
because there seemed to be no difference, psychologically, between
the suggestive idea and any other idea. And, indeed, there is no
difference ; suggestion is, for us, not a descriptive, but an explana-
tory term ; its definition is to be sought, not in psychology, but
in physiology. A suggestion is any stimulus, external or internal
(p. 56), accompanied or unaccompanied by consciousness, which
touches oif a determining tendency. The instruction to react, in
the reaction experiment, sets up the determining tendency which,
carrying over into the mid-period, releases the reaction movement.
What sets up the readiness to accept instruction ? A foregone sug-
gestion : the observer comes into the laboratory in order to be in-
structed, prepared to take orders. What brings him into the
laboratory ? Another foregone suggestion : the desire to learn psy-
chology, the fact that some of his friends have decided to come in.
What led him to choose the particular course that includes psy-
chology at the university? What led him to choose this particular
university? What led him to enter any university? All these
results are due to suggestion, to some stimulus or situation that
starts up determining tendencies. The nervous system, plastic as it
is, can take a set ; indeed, the taking of a set is as natural to it as
its general plasticity. Dr. Johnson is said to have met the argu-
ments for idealism by kicking a stone. His action expressed a
nervous set which seems to be native to the brain, a part of our
endowment as human beings : the set which determines us to take
the world of perception as a world of external objects, of real
things. Between such tendencies as this and the passing tendency
set up by the instruction of the reaction experiment there are all
degrees of persistence and of specialisation.
§ 125. The Genesis of Action. — We have just offered a
rough analysis of a typical action. Perhaps we should
rather have called it a schematic action. For the typical
action must be a sort of norm or standard, to which all
actions approach and from which they fall away ; and, in
order to describe it, we must have arranged, in the order of
§ 125. The Genesis of Action 451
their relationship, the various actions that we discover in
experience. Now any attempt to classify actions leads us
from analysis to genesis. The action which, by its conscious
representation, forms part of the subject-matter of psychol-
ogy is simply a phase in a course of conscious transforma-
tion; all actions change, as conscious events, with repetition.
Moreover, since the mechanism of bodily movement is in
part inherited and only in part acquired, the classification
of actions, if it is to be complete, takes us beyond individ-
ual development to racial evolution. We are here on very
slippery ground ; but it is ground which, in the present
state of psychology, we are bound to traverse.
What, then, was the character of the earliest organic
movements .'' There are two answers in current psychology
and biology. The first is that consciousness is as old as
animal life (p. 27), and that the first movements of the first
organisms were conscious movements. This is the answer
which the author accepts. The other is that consciousness
appeared later than life, and that the earliest movements
were accordingly unconscious movements, of the nature of
the physiological reflex.
It is very important that the issue here involved be correctly
understood. The alternatives are : movement with consciousness,
movement without consciousness. They are not — as they are
often stated to be — conscious action, mechanical reflex. All
actions, biologically regarded, are ' mechanical ' ; all, that is, may
by hypothesis be explained (and in all probabiUty will, some day,
be explained) in physico-chemical terms. The antithesis of the
conscious is not the mechanical, but the unconscious action ; the
antithesis of the reflex is not the conscious or voluntary action, but
the complex, coordinated action. A great deal of controversy
would have been avoided if this elementary point had been kept
clear.
452 Action
The author, then, beUeves, with Wundt ^ and Ward ^ and Cope,^
that the earhest movements were conscious movements, and that
all the unconscious movements of the human organism, even the
automatic movements of heart and intestines, are the descendants
of past conscious movements. What is the evidence ?
There is, first of all, the argument from the analogy of the in-
dividual hfetime. We learn to swim, to bicycle, to typewrite, to
play a musical instrument, with conscious intent and with a constant
accompaniment of consciousness ; later on, if we practise enough,
we do these things unconsciously. If, however, what are called
* voluntary actions ' may degenerate into ' secondary reflexes ' in
the course of a few weeks or months or years, it is at least possible
that the ingrained physiological reflexes may have a conscious
ancestry in the history of the race. Secondly, there seem to be no
reflexes, secondary or primary, that may not, under certain favour-
able conditions, be brought under cortical control and thus con-
nected with conscious intent and accompaniment ; we can all arrest
our breathing, but some of us can do much more, — can modify
heart-beat, expand or contract the pupil, quicken or slow the
peristaltic movements. This state of things is intelligible if we
interpret it as a return to a previous state, akin to the conscious
direction of a' bicycle, or the conscious control of movement in
swimming ; it is not easy to explain, if we regard the reflexes as
prior to consciousness. Thirdly, there are certain reflex move-
ments, movements that express emotion, which would be altogether
unintelligible unless we could posit for them a remote conscious
ancestry. The face of proud contempt reflexly ' curves a contume-
lious lip.' Why? " Our semi- human progenitors uncovered their
canine teeth when prepared for battle, as we still do when feeling
ferocious, or when merely sneering at or defying someone, without
1 W. Wundt, Physiol. Psychol., iii., 1903, 279; Outlines, tr. 1907, 213 ff.
Cf. Die Entivickhatg ties Willens, in Essays, 1906, 318 ff.
2 J. Ward, art. " Psycholog)'," in Encycl. Brit., xx., 18S6, 43.
3 E. D. Cope, The Origin of the Fittest, 18S7, 395. 413, 447. Cope's
essays are the more interesting, as he seems to have worked out his ideas strictly
from the biological standpoint, without reference to contemporary psychology.
Their biological derivation does not here concern us.
§ 125- The Genesis of Action 453
any intention of making a real attack with our teeth " ; the sneer
is the late and weakened form of the snarl, which meant a ripping
bite at an opponent.^ The thrusting forward of the head and body
is a common gesture of the enraged, and appears paradoxical —
since it exposes the head to a blow — unless we accept Darwin's
suggestion that this, too, is a remnant of attack with the teeth.
Instances of the sort might easily be multiplied. Fourthly, we
may note that the primary resemble the secondary reflexes in their
character as movements ; they are definite, clean-cut, precise.
But if this character comes in the one case with lapse of conscious-
ness, it may have come by the same road in the other.
Here, then, is evidence from various sources : evidence that
may, no doubt, be differently appreciated, but that, taken all
together, makes out a fair case. On the opposite side there has
been little attempt to gather special arguments. It seems natural
and obvious that the simplest form of movement — the physiological
reflex — should also be the earliest ; it seems natural that mind,
the crown and flower of life, should appear later in the history of
the world than life itself; and this seeming naturalness has passed
into theory as matter of fact. The view that life and mind are
coeval arose, indeed, as a protest against the unproved but dominant
view of the priority of unconscious movement, and the represent-
atives of this latter standpoint have not even yet taken the challenge
very seriously. If they do offer evidence for their conviction, they
are hkely to say that mind appeared at some time of stress, when
neural tension was at its highest and neural processes were hesitant.
Aside, however, from the objection that the phrases ' neural ten-
sion ' and 'neural hesitation' are metaphorical onlyj and aside
from the fact that mental processes may be exceedingly intensive
on occasions when the organism is in no sort of perplexity (think
of the plunge into cool water on a hot day ; of the enjoyment of
music after long aesthetic starvation ; of our grief at the loss of a
dear friend), — aside from these considerations, the question at
once comes up : Whence does the organism get its capacity for
^ C. Darwin, The Expression of the Emotions in Man and Animals, ch,
X. (1890, 264). The reader may be reminded of the footnote, p. 408.
454 Action
changing, under stress, from a physiological to a psychophysical
organism? The organic machine has run, for a certain time,
without consciousness ; it is now in difficulties ; it surmounts them
by a neural readjustment, which is paralleled by consciousness.
Must not consciousness have been present, potentially or germi-
nally, before the difficulties appeared ?
We may, of course, carry our appeal to the child and the primi-
tive organism, and try to interpret their movements in the light of
our own ; this direct appeal is, indeed, imperative. But we must
not expect a speedy verdict. The human infant, in particular, as
the incomplete form of a very highly developed organism, em-
bodies two courses of development, a phylogenetic and an onto-
genetic, in their most complex modes. The new-born child hangs
to your finger, supporting its full weight upon its arms ; the boy,
a few years later, will hang in like manner from the horizontal
bar. Is the conscious gymnastic exercise genetically related to
the first reflex grip ? Yes, in some measure ; both the baby and
the boy are, by descent, little monkeys. But the boy does not
keep the baby's reflex, and import consciousness into it ; the
reflex lapses, giving way to other forms of movement, — an older
baby, if you give him your finger, puts it in his mouth ; the boy's
action is due to suggestion. So, while both performances are
conditioned on racial inheritance, the later is not the direct out-
growth of the earlier, and we should go widely astray if we argued
from Hkeness of form to continuity in ontogenesis.
Recent studies of the behaviour of the lowest organisms have
led to widely divergent results, according as the investigator has
made the stimulus or the organism, so to say, the unit of his work.
If he keeps his attention on the stimulus, and tries to ascertain
the direct effect upon movement of light, heat, gravitation, the
organism may appear as a bundle of tropisms, of direct and uniform
motor responses. If he keeps his attention on the organism,
starts out from its total behaviour, and tries to reduce this total
to a number of elementary responses, he finds that " these lower
organisms furnish problems which do not differ in kind from
what we find in higher animals. To the same stimuli different
§ 12 5- TJie Genesis of Action 455
organisms react differently ; different individuals of the same
species react differently ; and even the same individual reacts
differently at different times." ^ The analytical method, which
proceeds from total behaviour to elementary reaction, is with-
out question, as a method of first attack, more reliable than
the synthetic method, which attempts to build up a complex be-
haviour out of simplest elements ; and we may therefore conclude
that observation of the lowest organisms is at least not unfavour-
able to our own theory of action.
This theory finds, however, a special difficulty in the problem
of the first movement of the first moving organism, — the first
vital movement that was made upon the planet. By hypothesis,
that movement was conscious : but how was the organism sug-
gestible ? It is the first organism ; it has had no past ; conscious-
ness comes into being with its birth ; how can it * reply ' or
'respond' to stimulation? We can only guess. But we may
guess that a fallacy lurks in the seemingly innocent statement
that the organism has had no past. We must believe that the
organic arises from the inorganic, that life is derived from the
not-living ; but we are not bound to believe that the transition
was abrupt. On the contrary, it is probable that nature (if
we may speak metaphorically) made many essays at life before a
stable, self-sustaining life was struck out ; that there were many
intermediate stages between the non-vital and the vital, many
imperfect modes of half-life, part-hfe, which were instable and
therefore transient, but which none the less bridged the gulf
between the inanimate and the animate worlds. Hence the
first living thing would have had a past, a half-vital ancestry ;
and this past would have moulded it, given it direction, rendered
it susceptible on some sides and resistant on others ; in a word,
would have done for it, in a crude way, precisely what our ancestry
does, in an indefinitely more complicated way, for ourselves.
So the difficulty is met — speculatively, it is true, but by a specula-
^ H. S. Jennings, Diverse Ideals and Divergent Conclusions in the Study of
Behaviour in Lower Organisms, in American Journal of Psychology, xxi.,
1910, 368.
456 Action
tion which does not conflict with the general doctrine of organic
evolution, and by speculation at all only because there is no other
means of meeting it.
Let us accept the view that the first movements of the
first organisms were conscious movements. What happens
to the action consciousness in the course of evolution ?
An examination of our own actions shows that, in the
course of the individual lifetime, this consciousness takes
two different roads. On the one hand, we are continually
enlarging our sphere of action ; conduct grows more
complex ; there is a tendency towards more and more com-
plicated and specific coordination of movements ; and the
realisation of this tendency is always accompanied by
increasing complexity of consciousness, by the mental
processes and attitudes known as choice, resolve, delibera-
tion, comparison, judgment, doubt. On the other hand,
there is a tendency toward the simplification of movement,
and the realisation of this tendency is accompanied by
lapse of consciousness. Plasticity, that is, subsists along-
side of fixity.
If, now, this analogy is to be trusted, we should expect
to find the same combination, of plasticity and fixity of re-
action, all through the animal kingdom. But we should
expect to find the two tendencies combined in unequal
measure. Man is preeminently plastic, educable in a
supreme degree. We should expect that, perhaps at the
other end of the organic scale, rapid fixation of movement
leaves but a small margin of plasticity. We find, in fact,
something much more interesting ; we find that the line
of animal descent bifurcates, the one branch leading to
fixity with a minimum of plasticity, the other leading to
§ 125. The Genesis of Action 457
plasticity with a minimum of fixity. The action conscious
ness thus appears to have a double history, whose parallel
chapters throw welcome light, the one upon the other.
Zoologists divide the animal kingdom into two great groups,
whose lines of descent are distinct as far down as the fiat-worms.
The one of these leads through the unsegmented and segmented
worms to the insects, spiders and crustaceans ; the other leads
through various invertebrate forms, largely extinct, to the verte-
brates, and so finally to man. Students of animal behaviour abo
divide the animals into two great groups, those that are markedly
plastic in their responses to stimulation, and those that are mark-
edly fixed. The interesting point to us is that these groupings
coincide. It has been seriously argued, e.g., that ants and bees
are pure automata, mindless reflex machines ; and though this ex-
tieme position is not generally taken, it is agreed that the popular
ascription of intelHgence to these creatures falls wide of the mark.
In the author's view, we have here a confirmation of the theory
that consciousness is as old as life. The action consciousness
persists, as it were in equilibrium, from the protozoa to the flat-
worms. There its path diverges : on the one side lie neural fixity
and unconscious response, on the other lie neural plasticity and
conscious response. But these alternatives are not absolute ;
survival requires both fixity and plasticity; the divergence, as we
might expect from the common path that precedes it, is a diver-
gence of emphasis, not a complete separation.
Further details — the probable proportion of fixity and plasticity
in particular forms, the reason for the extinction of the interme-
diate types in the vertebrate line — cannot here be discussed. But
a word of caution may be added. The lowest organisms that
exist to-day have, we must remember, an ancestry that is presum-
ably as long as that of man. They may have remained what, by
the theory, they originally were, psychophysical organisms ; but
they may also have lost the flicker of mind that they at first pos-
sessed, and have hardened into unconscious machines. If proof
could be brought that all the present protozoa are unconscious, —
458 Action
the assumption is on all accounts improbable, but we make it for
argument's sake, — if this proof could be brought, our theory
would still be unshaken ; for the fact would simply mean that, in
the course of ages, the protozoa had travelled the whole distance
from plasticity to fixity, and had thus lost an original animal char-
acteristic.
§ 126. The Classification of Action. — Our discussion of
the genesis of action, while it has shown that the instabil-
ity of the action consciousness is a native and universal
character, racial and individual alike, has for that very
reason failed to provide us with a typical pattern. We
cannot, perhaps, do better than recur to the schematic ac-
tion of p. 448 : the consciousness whose predetermination
is represented by the idea of end and the kinaesthesis that
means ' You are to move' ; which culminates in the appre-
hension of some object under the influence of the idea of
end ; and which concludes with the perception of result
and the sensations aroused by movement. Such a con-
sciousness, singly determined, and rounding its course from
idea of end or result to perception of result, and from an-
ticipatory kinaesthesis to the kinaesthetic accompaniment
of movement made, may be termed an impulse.
Impulsive action then degenerates, first, to ideomotor or
sensorimotor action, in which the predetermination is un-
conscious, and the idea or perception of the object at once
touches off the movement. Some one says to us, ' There's
a caterpillar on your hair! ' and we raise our hand and brush
the caterpillar away. Or we are talking interestedly and,
without interruption of the thought, pass a hand over our
hair. Finding a caterpillar there, we may say, ' Ah ! I
thought I felt something,' and fling it away. From this
level the descent continues to the level of the secondary
§ 126. TJie Classification of Action 459
reflex. The author has evidence that he has made a
locahsing movement, and flicked an insect off his knee,
without knowing that he was going to move, that he had
moved, that the insect had settled, or that he had re-
moved it.
The impulse may also travel in the opposite direction,
towards complication of consciousness. An action may be
subject to more than one determination ; it may be the
expression of a hierarchy of determinations. And it may
result from a conflict of impulses, just as secondary atten-
tion results from a conflict of primary attentions (p. 272).
We then have what is ordinarily termed voluntary action,
— though this name is so variously employed that we shall
do best to avoid it, and to speak of selective action. This,
in its turn, degenerates ; first, into ideomotor or sensorimotor
action, and then into a reflex. The skilled pianist reads
off a musical score at sight ; the thought of mail time sends
us downstairs with our letters. Or, at the lowest level,
our fingers move over the keyboard of the typewriter auto-
matically, while attention is wholly occupied with the mat-
ter to be written.
In § 76 we illustrated the development of secondary attention by
appeal to an imaginary animal, endowed with two sense-organs.
The conflict of impulses may be illustrated, at all its stages, from
actual experience. When a young child comes face to face with
a strange dog, it behaves as if pulled back and forth by strings;
it goes up to the dog, runs back to its father, approaches the dog
again, and so on. It has happened to the author, in presence of
the two impulses to shut a door on the right and to seat himself
at a desk on the left, to begin a right-hand movement towards the
door, and then all at once to slue round to the desk, without
having closed it. Here we have the conflict of impulses at its
nakedest. The case is very different — though the extremes are
460 Action
connected by a host of intermediate consciousnesses — when the
impulses derive from a number of determining and associative
tendencies, and when the object is a complex situation. Here
psychology is sorely in need of further analyses. We can say,
however, from the results of experiments upon the compound re-
actions, that consciousness need be neither so full nor so logical
as the psychologies usually represent it ; determinations may be
carried in very fragmentary terms, and a wide range of reflective
consideration may be packed into a conscious attitude.
The mechanism of selective action is, in principle, understood.
It is different with what we may call volitional action, in which an
impulse comes into conflict, not with another impulse, but with
some associative constellation that has no motor reference. I hear
my alarum-clock, and have the impulse to get out of bed ; but
the impulse is definitely opposed by the idea of another half-hour's
sleep. If I get up, I perform a volitional action. What has
happened? And what happens if I do not get up?
In the scanty analyses of the cognitive choice reaction that we
possess, the reaction in which white was to be reacted upon and
other stimuli disregarded (p. 440), the negative instruction came to
consciousness either as an ' assurance ' that the given stimulus was
not to be replied to, or as a felt inhibition of movement, i.e., an
unusually strong pressure upon the key from which the finger was
slipped in the movement of reaction. Experiments upon the
associative reaction, in which a negative instruction was given,
have recently been reported : pictures were exposed, and the re-
actor was required to speak the first word that occurred to him,
unless it were the name of the object pictured ; the name was not
to be uttered. Unfortunately, there was no systematic introspection
during the fore-period. The mid-period showed various types of
consciousness. Thus the name may appear, in internal speech,
with a tendency to its utterance ; then come the ' thought ' that it
must not be spoken, and a ' locking ' of the throat muscles ; and
then tlie fitting association is given. Sometimes the thought
alone, sometimes the locking alone, is enough to guide the reaction.
Or the thought of the instruction may prevent even the appearance
§ 126. TJie Classification of Action 461
of the name, after the object has been apprehended. Or, again,
the reactor changes the instruction from negative to positive ; he
observes the details of the picture, asks himself what might be
done with the object, and so specialises the association. Finally,
we have sheer automatism; the name may appear in internal
speech, but it is at once suppressed, without conscious represen-
tation of the suppression ; or, in extreme cases, the apprehension
of the picture touches off directly the appropriate association.
These results are interesting in themselves ; they show us some
of tlie conscious aspects of the suppression of one determining
tendency by another. They also help us to understand the
volitional action. A positiv^e instruction, we may suppose, opens
certain nervous channels, but at the same time blocks other
channels ; it acts not only positively, by facilitation, but also
negatively, by inhibition (p. 300). So a negative instruction
blocks certain channels, but at the same time opens others; it,
too, acts positively as well as negatively. My alarum-clock, then,
not only opens the getting-up channels, but interferes with the
nervous set — whatever that may be — which keeps me lying still ;
while the idea of another half-hour's sleep means not only the
reinforcement of this nervous set, but also a positive blocking of
the suggestion from the clock. The notion of the cortical mech-
anism as of this double-faced, positive-negative kind does away
with the mystery of the conflict in volitional action, though we
must add the usual caution, that nothing in detail is known of the
subject. ^ — ■
We remarked in § 103 that words are originally gestures ; the
word consciousness is therefore an action consciousness. Speech
and writing are, in fact, symbolic actions; and they may be
selective or volitional, or they may appear in the ideomotor and
reflex forms. The signing of my name to a deed is the expression
of a highly complex determination ; under other circumstances,
if I have a pen in my hand and paper before me during a com-
mittee meeting, I may write my name again and again, quite
unconsciously. The study of gesture in general is a study in the
history of symbolic actions ; and the symbolism may, at any
462 Action
moment, reappear ; a particular hand-shake, or the doffing of the
hat to a certain acquaintance, may imply reconciliation or social
recognition, and may thus be as complex in its determination as
the signing of the deed. All this means — what may have been
obvious to the reader long ago, and what follows from our insist-
ence upon the fact of determination — that the bodily movement
is, in so comphcated an organism as man, no index to the action
consciousness. To say that 'signing one's name is a voluntary
action ' is to say what may or may not be true ; it may be a
highly elaborate selective action, or it may be a secondary reflex.
There remain the actions which bring into play an in-
herited mechanism, or express an inherited nervous dis-
position : the physiological reflexes and the instinctive
movements. The former we believe to have had a racial
history that parallels the individual history of the second-
ary reflexes. The latter include a great variety of move-
ments, from complex or serial reflexes up to massive
reactions that are accompanied by a highly insistent con-
sciousness. No agreement has so far been reached, as
regards either the definition of instinct or its place in the
hierarchy of human actions ; but it seems safe to say that
the instinctive movement, whatever else it may be, is
always initiated by the release of an inherited disposition ;
that the instinctive consciousness resembles the impulsive,
but is richer in organic components ; and that there is a
very close connection between instinctive and emotive
reactions.
Instinct has long been one of the catchwords of popular
psychology ; even now it stands next only to ' feeling ' in loose-
ness of usage and multiplicity of application ; and it does scientific
harm, where feeling is innocent, by its profession to explain, to
name the cause of action ; animals act ' on instinct,' while man,
at any rate in his specially human moods, acts * by reason.' There
§ 126. The Classification of Action 463
is some excuse for this laxity and confusion, for the phenomena of
instinct are of wide range and great complexity. We must,
however, ourselves be clear ; and we shall achieve clearness most
easily by calling to mind the two great branches of the animal
kingdom, with their opposed characters of predominating fixity
and predominating plasticity. Fixity of response means response
by way of an inherited nervous mechanism, purely instinctive
response ; and it is, in fact, among the insects that we find what
are probably the most striking examples of purely instinctive
action. Plasticity of response means response by way of an ac-
quired nervous mechanism ; and it is in man that we find the
most numerous, the most varied and the most complicated ex-
amples of non-instinctive action. On the other hand, as we saw
no ground for supposing that, in the one line of descent, fixity
has entirely replaced plasticity, so we have no ground for denying
that, in the other, plasticity is based upon an underlying fixity.
Apart from the logical absurdity of an absolute plasticity, we come,
again and again, upon evidence that our own determining ten-
dencies are inherited. In so far as this is the case, our actions
are instinctive.
As to thelbxistence of an instinctive consciousness, opinions
differ. " The idea of consciousness must be rigidly excluded
from any definition of instinct ; " " any definition of instinctive
action that does not insist upon its psychical aspect is misleading ; "
so the authorities ! It is better to appeal to the facts. And the
facts show us that actions which proceed from inherited deter-
mination (the physiological reflexes excluded) are in this respect
like other actions ; they show all stages, from full consciousness to
complete unconsciousness. There can, however, be no question
that the instinctive action, in the middle of its career, is attended
by a consciousness of characteristic pattern and of a high degree
of complexity.
If we try to work out a rough classification of instincts, we find
at the lower end of the scale a number of movements that grade
off into the reflex, — such things as coughing, smiling, sneezing,
swallowing, threading our way on the street, beating time to
464 Action
music ; or, in the human infant, such things as sucking, biting,
clasping, turning the head aside, standing, creeping, walking, cry-
ing, vocaHsing. These are definite responses to particular stimuli.
At the upper end of the scale, we find large, general tendencies :
the tendency that makes us take the world of perception as a world
of real things ; the empathic tendency that makes us humanise our
surroundings, animate and inanimate alike ; the social tendency
that makes us imitative and credulous (' suggestible ' in a narrower
sense : cf. p. 449) ; the tendency to dual division, closely connected
with the polar opposition of pleasantness-unpleasantness, which
makes us classify the world by pairs, good-bad, active-passive,
etc. ; the tendency to try things out, which is largely responsible for
play, and the tendency to let things be, which is largely responsible
for the laziness of a life of routine : — these and other tendencies,
which represent total directive pressures laid upon the organism,
more strongly upon some individuals and more weakly upon
others, but in some measure upon all ; and which are realised or
expressed on very various occasions, and with very varying accom-
paniment of consciousness. Between these extremes he what we
may term the instincts proper : fear, love, jealousy, rivalry, curios-
ity, pugnacity, repulsion, self-abasement, self-assert^n, and so on.
No complete list, with verifiable terms, has as yet been made out ;
and no adequate analysis of the instinctive consciousness has been
undertaken. In general, the consciousness is of the action type ;
it differs from the impulsive consciousness in comprising massive
complexes of oiganic sensation; it changes as the action is
repeated, thinning out into sensorimotor forms, or enrichin-^ itself
by association, according to circumstances _; it passes over, without
any sharp line of division, into emotion. On the physiological
side, the instinctive reaction is a reaction of the whole organism,
not of some organ or member. The determining tendencies
which underlie it may be touched off, not only by their proper
stimuli, but by other, like stimuli (§ 107) ; they are often transi-
tory, ripening at a definite period of the individual lifetime, and
then decaying again; they are subject to inhibition and reintorce-
ment, both by other determining and by associative tendencies.
§ 126. TJcC Classification of Action 465
so that their expression in movement is extremely variable ;
and, like the tendencies set up by instruction (p. 449), they are
liable to specialisation, to become " systematically organised
about certain objects or ideas."
All this must, unfortunately, be left in general terms, though the
plan and programme of a psychology of instinct seem clear enough.
The term is common to two distinct sciences, psychology and
biology; and the result of this community has been that the
psychologists are tempted to write a speculative biology, and the
biologists to manufacture a psychology of instinct. The mutual
recrimination that has ensued is a doubtful gain to science. What
we have to do is to leave biology to formulate its own problem,
and to accept its solution of that problem, while we ourselves, as
psychologists, describe and explain the instinctive consciousness.
Our classification is herewith complete ; we have made out
a family tree for action, and have assigned the various types
to their genetic places in it. Let the reader now be warned
not to take the classification too seriously ! At the best,
classification — whether of perceptions, or of associations,
or of actions or of anything else — is not psychology, but
only a more or less useful preliminary to psychology. And,
in the present instance, we have an unfortunate disjunction
of psychological analysis and classification. Analysis has
begun, rightly enough, with the reaction experiment ; but
the reactions to be analysed have not been shaped in accord-
ance with current classifications of action ; the analysis has
rather proceeded, on the old hnes, from the simple to the
compound reaction, as if the reaction experiment were a
thing apart. Our classifications, on the other hand, are
the product of a reflective, non-experimental psychology ;
we have no introspective guarantee of their adequacy. So
we are in this curious position : that we possess a fairly
large body of observations of the action consciousness, and
2H
466 Action
a number of professedly complete classifications of action,
and nevertheless are unable to bring the two together. In
such circumstances, we shall be wise to accept the observa-
tions, and not to commit ourselves positively to any system
of classification.
§ 127. Will. — The familiar division of mental pheno-
mena into those of intellect, feeling and will is a legacy from
the psychology of the eighteenth century. The terms are
still in use as class-names : intellect for the experiences
based on sensation and image, feeling for the whole of our
affective experience (p. 228), and will for the facts of atten-
tion and action. Their definition is, however, extremely
fluctuating. Thus, imagination is treated, in recent books,
under all three headings; and will is sometimes restricted
to secondary attention and selective and volitional action,
sometimes divorced from attention altogether.
It would, then, be unnecessary to devote a special Section
to will, were it not that there is a specific will conscious-
ness. The observers in the reaction experiment report,
without hesitation, that their response was or was not willed
The essential factor in this will consciousness appears to be.
a conscious ' acceptance ' of the instruction.
If a foreign stimulus is introduced into a series of muscular re-
actions, the reactor, who is prepared by the suggestion 'as quickly
as possible,' moves in response to it, but is clear that the action
was not willed. If a stimulus of the same general kind as the reg-
ular stimulus is introduced, e.g., a red in place of a white card, the
reactor may be in doubt whether the action was willed or not. In
general, any consciousness which is consciously referred to an in-
struction accepted by the reactor is reported as a will conscious-
ness. Will thus differs, introspectively, on the one hand from
the purely associative consciousness, based upon the play of
associative tendencies ; and, on the other hand, from the
§ 127- Will 467
consciousness of command, where there is determination, but not
an ' acceptance ' of determination. So far as analysis has gone,
this acceptance appears as an organic set which carries the mean-
ing ' I agree.' Both terms in the meaning are emphatic ; there
is a reference to the psychological self, and there is an intention to
yield, to acquiesce.^ It is rarely, however, that the will attitude be-
comes either explicit or focal. As a rule it is, so to say, incor-
porated in the total reaction consciousness ; the organic sensations
which constitute it are blended with the other conscious contents ;
the reactor does not know that he is willing, but if questioned
afterwards declares that he did will. With repetition of the action,
and in default of renewed instruction, it disappears altogether.
We shall have more to say of the will attitude when we come to
deal with the conscious attitudes in general (pp. 519 f).
Conation. — The Dictiona?'y of PJiilosopiiy and PsycJiology writes
of conation as follows : "the theoretical active element of conscious-
ness, showing itself in tendencies, impulses, desires and acts of
volition. Stated in its most general form, conation is unrest. It
exists when and so far as a present state of consciousness tends by
its intrinsic nature to develope into something else." These
sentences seem to mean that consciousnesses like impulse and
desire contain an elementary process of unrest, which cannot be
isolated and examined for itself, but the assumption of which is
necessary to a full description ; and that such consciousnesses, in
virtue of the interfused unrest, are themselves restless, actively
transitory, and travel of their own accord to their own extinction.
The question of the existence of an active element of unrest can
be decided only by appeal to experimental introspection. Wundt,
as we have seen, posits an elementary excitement and an elemen-
tary tension ; but these processes are, for him, affections. The
investigators of the reaction consciousness, in all their hundreds
1 An illustration may, perhaps, be helpful. An observer reports : " Akt
der Zustimmung wesentlich motorischer Natur (unrnittelbar auf der Ichseite
erlebt) " : an act of acceptance, of essentially kinaesthetic character, felt as
belonging to the self-side of experience. The latter phrase means that the
reactor felt h'mself in the attitude of acceptance, irrespectively of the actual,
physical attitude of the body.
468 Action
of reports, do not discover an active element ; unrest, effort, urgency
appear in organic, especially in kinaesthetic terms. The time has
gone by for reflective psychologising in the study ; if the champions
of the active element wish to be taken seriously, they must either
experiment themselves or must propose crucial experiments for
others — and must then abide by results. Nothing is easier than
to manufacture mental elements (p. 49) ; but the penalty should be
six months of introspective labour under laboratory conditions.
The latter part of the definition impHes a view of mind that we
cannot accept. " Mental activity exists when and so far as process
in consciousness is the direct outcome of previous process
in consciousness." ^ If that is the case, the author can only reply
that it does not exist at all. The direction of a present conscious-
ness may be predetermined by a suggestion which was itself rep-
resented in consciousness ; but to say that the present consciousness
is the direct outcome of the foregoing suggestion- consciousness is
either to say, simply, that the one immediately follows the other,
or is to make consciousness a form of energy (p. 11). And when
we read of a ' tendency ' of consciousness ' by its intrinsic nature to
develope into something else,' we surely have before us nothing
more than a figurative expression drawn from popular biology.
The Motivation 0/ Action by Affection. — We referred on p. 263
to the doctrine that pleasantness and unpleasantness are sympto-
matic of a normal and abnormal mode of life ; and we dismissed it
as unproved and irrelevant. This doctrine is often found in con-
nection with another, which gives pleasantness and unpleasantness
an active role in the mental life ; they are incentives to and deter-
rents from action, they guide the vital functions, they stimulate
the organism's activity for ends. Pleasantness is thus the sign
that we are well ; but it also prompts us to act in such a way that
we remain well. Unpleasantness is the sign that we are unwell;
but it also prompts us to refrain from acting in such a way that we
become unwell.
There are various ways in which this position may be met. We
might question the correlation, as we did before. We might ask
^ G. F. Stout, Analytic Psychology, i., 1S96, I4S.
References for Further Reading 469
how it is that a mental process can incite or deter, 'stamp in ' this
and ' stamp out ' that mode of reaction. All that is necessary,
however, is to appeal to the facts. Movement follows on sugges-
tion ; and the conscious aspect of suggestion may be pleasurable,
unpleasurable or indifferent. Kiilpe wrote, in 1893, that "the in-
centives to vohmtary activity may be of exceedingly different kinds,"
so far as they are conscious, and that volition may be " partially de-
termined by unconscious incentives." Thorndike, in 1905, declares
that " any mental state whatever may be the antecedent of an in-
tentional act." This position, extreme as it is, squares far better
with the introspections of the reaction experiments than does the
traditional doctrine of motivation by pleasure-pain.
References for Further Reading
§§ 121-127. W. Wundt, Physiol. Psychol., iii., 1903, 242 ff. ; Out-
lines of Psychol., tr. 1907, 203 fif. ; W. James, Prific. of Psychol., ii.,
1890, 486 ff.
§ 121. E. C. Sanford, Personal Equation, in American Journal
of Psychology, ii., 1888-89, 3, 271, 403. For the history and technique
of the reaction experiment, E. B. Titchener, Expe.r. Psychol., II., i..
1905, 141 ff. ; ii., 326 ff., 356 ff.
§ 122. Wundt, Physiol. Psychol., iii., 1903, 410 ff. The analysis
follows N. Ach, Ueber die Willenstdtigkeit und das Denken, 1905; but,
so far as these simple reactions are concerned, it has been repeated and
verified in the author's laboratory.
§ 123. Wundt, op. cit., 450 ff. ; also ii., 1910, 38 ; Ach, op. cit. For
the subtractive procedure, Wundt, iii., 450 ff. ; Ach, 156 ff. ; O. Kiilpe,
Outlines of Psychol., 1909, 410 ff. For the psychology of instruction,
Titchener, Lectures on the Exper. Psychol, of the Thought-processes,
1909, index under Problem. For the diagnostic association experiment,
C. G. Jung, The Association Hfethod, in American Journal of Psy-
chology, xxi., 1 910, 219 ff.
§ 124. Kiilpe, op. cit., [1893] 1909, 409, 415. For determining ten-
dencies, Ach, op. cit., esp. 191 ff. ; Titchener, op. cit., index under
Tendencies. For suggestion, J. M. Baldwin, Mental Development in
the Child and the Race: Methods and Processes, 1906, 100 ff.
§ 125. Titchener, Were the Earliest Organic Movanents Conscious
or Ujiconscious? in Pop. Set. Monthly, Ix., 1901-2, 458 ff . ; cf. Feel-
470 Action
zng and Attention, 1908, 387; C. J. Herrick, The Evolution of Intelli-
gence and its Organs, in Science, N. S. xxxi., 1910, 7 ff. ; Baldwin,
op. cit., 197 ff., 349 ff.
§ 126, For the negative instruction, H. S. Langfeld, Suggestion
with Negative Instruction, in Psychol. Bulletin, vii., 1910, 200 ff. For
instinct, James, as quoted in the text ; W. McDougall, Ati Introdttctioti
to Social Psychology, 1908.
§ 127. Ach, 230 ff. ; A. Messer, Experimentell-psychologische Unter-
suchtingen Ytber das Denken, in Archiv f. d. gesanite Psychol., viii..
1906, 203. In support of a conative element, G. T. Ladd, Psychol.
Descriptive and Explanatory, 1894, 211 ff. On motivation, Kiilpe,
op. cit., 445 ff. ; E. L. Thorndike, The Elements of Psychology, 1905,
282 ff. ; D. C. Nadejde, Die biologische Theorie der Lust und Unlust,
1908.
EMOTION
§ 128. The .Nature of Emotion. — Suppose that you are
sitting at your desk, busy in your regular way, and ob-
scurely conscious of a rumble of a car that is passing down
the street ; and suppose that the rumble is suddenly inter-
rupted by a shrill scream. You leap up, as if the scream
were a personal signal that you had been expecting; you
dash out of doors, as if your presence on the street were a
matter of imperative necessity. As you run, you have
fragmentary ideas: 'a child,' perhaps, in internal speech;
a visual flash of some previous accident; a scrap of kinaes-
thesis that carries your whole attitude to the city car-
system. But you have, also, a mass of insistent organic
sensation : you choke, you draw your breath in gasps, for
all the hurry you are in a cold sweat, you have a horrible
nausea; and yet, in spite of the intense unpleasantness
that floods your consciousness, you have no choice but to
go on. In describing the experience, later, you would say
that you were horrified by hearing a child scream; the
mental processes that we have just named make up the
emotion of horror.
An emotion is thus a temporal process, a course of con-
sciousness, and it is also, characteristically, a suddenly
initiated consciousness; it begins abruptly, and dies down
gradually. It is a highly complex consciousness, since its
stimulus is not an object, a perceptive stimulus, but some
total situation or predicament. It is through and through
an affective consciousness, since both the situation itself
471
472 Emotion
and the organic sensations of the emotive reaction are def-
initely pleasant or unpleasant. It is an insistently organic
consciousness, although the proportion of organic to idea-
tional constituents varies greatly from emotion to emotion
and from individual to individual. And, finally, it is
always a predetermined consciousness, proceeding in the
given case to a natural terminus ; although here, too, there
is great variability, since the determining tendencies to
which the situation appeals may be almost wholly instinc-
tive, or may be partly instinctive and partly acquired.
We have very elaborate accounts of the 'expression' of emotion,
and we have elaborate diagrams, so to speak, of the emotive con-
sciousness ; but, so far as the author is aware, we have no system-
atic description of emotion, taken under standard conditions. In
other words, we have no first-hand analytical psychology of
emotion ; and it is this lack that makes the chapter on
emotion in the text-books the dreary reading that it is. Two
reasons are usually given for the deficiency : first, that it is im-
possible to bring emotion into the laboratory ; the emotions there
setup are artificial, washed-out, insipid affairs; and secondly that
we have no method for the study of emotion, since attention to
affection defeats its own object (p. 231). Neither reason is valid.
It is not difficult, with a little ingenuity, to arrange situations in
the laboratory that shall arouse a fairly wide range of emotions.
If these emotions are net of the very intensest, neither are the
ordinary emotions of everyday life ; and if they tend to disappear
with repetition of the situations, our everyday emotions do the
same thing. Besides, the laboratory offers the very great advan-
tage of isolation; we can get the emotion pure, and without
interruption from extraneous processes. On the other hand, it is
not necessary to affective introspection that attention be directed
upon the affection. Recent work has shown that, if attention
is directed upon the stimulus, the situation, an affective judgment
comes directly, of itself; the quality and intensity of the affection
touch off the corresponding expression or report. Nothing more
§ 128. TJie Nature of Emotion 473
is required than that the observers shall be fittingly instructed,
affectively predisposed. When the predisposition to express the
feelings has been set up, it is this that is actuaUsed by the pres-
entation of stimulus, and that dictates the introspective report.
The observer has no impulse to describe the situation in sensory
terms, focal as these terms were. What, now, this predisposition
is ; how far (if at all) it interferes with the impression of the stim-
ulus on the sensory side ; with what degree of constancy it may be
induced, and how widely it varies from one observer to another :
of all these things we are still ignorant. But there can be no
question that the mechanism of affective introspection is as it is here
described.
The reason, then, that our descriptive psychology of emotion is
schematic rather than analytical is, simply, that experimental psy-
chology has so far found neither the time nor the courage to take
emotion into the laboratory. But we shall presently have analyses
of this, as we are beginning to get analyses of the action con-
sciousness.
Feeling ajid Emotion. — It seems almost self-evident that there
is a close connection between the sense-feeling (p. 227) and the
emotion, that — to put it roughly — a feehng is a simpler emotion,
an emotion a more complex feeling. And the assumption of this
connection is justified if, as we explained on p. 408, an emotion
may degenerate into a feeling. Nevertheless, certain psychologists
draw a sharp line of distinction between the two experiences ; feel-
ing is, for them, a passive and receptive matter, emotion is feeling-
attitude, a reaction of the whole conscious organism upon the
situation.^ We can all understand what this distinction means, and
we can all think of cases in which it is introspectively attested.
But we can also, very certainly, think of intermediate cases, in
which the sense-feeling passes into emotion, and the emotion into
sense-feeling, without sensible break. The author cannot but
think that the majority is in this case right, and that feeling and
emotion are species of the same mental genus.
1 D. Irons, The Nature of Emoiion,\ry Philos. Review, vi., 1897, 242;
C. Stumpf, Ueber Gejilhlsempjindungen, in Zeits.f. Psychol,, xliv., 1906, 7;
G. F. Stout, A Manual of Psychology, 1907, 63 f.
474 Emotion
§ 129. The ' James-Lange Theory ' of Emotion. — In 1884,
James propounded the rather paradoxical theory that what
had ordinarily been regarded as the ' expression ' of an
emotion is, in reality, the source of emotion as a conscious
process. It is worth while to quote the critical passages.
" Our natural way of thinking about the emotions is that the
mental perception of some fact excites the mental affection called
the emotion, and that this latter state of mind gives rise to the
bodily expression. My thesis on the contrary is that the bodily
changes follow directly the PERCEPTION of the exciting fact,
and that our feeling of the same changes as they occur IS the etnotion.
Common sense says, we lose our fortune, are sorry and weep ; we
meet a bear, are frightened and run ; we are insulted by a rival,
are angry and strike. The hypothesis here to be defended says
that this order of sequence is incorrect, that the one mental state
is not immediately induced by the other, that the bodily manifesta-
tions must first be interposed between, and that the more rational
statement is that we feel sorry because we cry, angry because we
strike, afraid because we tremble, and not that we cry, strike, or
tremble, because we are sorry, angry, or fearful, as the case may
be." 1
No one, James continues, " will be inclined to doubt the fact that
objects do excite bodily changes by a preorganised mechanism, or the
farther fact that the changes are so indefinitely numerous and subtle
that the entire organism may be called a sounding-board, which
every change of consciousness, however slight, may make rever-
berate. . . . Eveij one of the bodily changes, whatsoever it is, is
YYA-jT, acutely or obscurely, the momejit it occurs. . . . Each emo-
tion is the resultant of a sum of elements, and ... the elements
are all organic changes, and each of them is the reflex effect of the
exciting object." ^
1 W. James, JF/iai 7S an Emofion ? in Mind, O. S. ix., 18S4, 1 89 f. The
first sentence of the quotation has been verbally modified. See also Prittc.
of Psychol., ii., 1890, 449 f.
^ Princ. of Psychol., ii., 4c;o ff. James is writing as an advocate, and
has — naturally enough — forgotten for the moment the fact of the limen.
§ 129. The ^jaiutS'J,u:?^e Theory'' of Emotion 475
Emotion, then, is on this view r, group of reflexly excited
organic sensations, clustered about a perception. There is
no special affective moment in emotion ; the whole experi-
ence is reducible, psychologically, to reflexly aroused
organic sensations.
The theory, which was vigorously and persuasively
stated, received a further impetus by the publication, in
1885, of a tract by C. Lange, professor of medicine in
Copenhagen. Lange comes independently to a conclusion
which, in principle, is the same as that of James, though it
is more narrowly formulated. He says :
" It is the vasomotor system that we have to thank for the whole
emotional aspect of our mental life, for our joys and sorrows, oui
hours of happiness and misery. If the objects that affect our
senses had not the power to throw this system into action, we
should travel through life indifferent and dispassionate ; the im-
pressions from the outside world would enrich our experience,
would increase our knowledge, but that is all ; they would neither
rouse us to joy nor goad us to anger, neither bow us in care nor
overwhelm us with terror."
An emotion thus consists, for Lange, of two factors :
first, of what he calls the ' cause,' a sense-impression which
operates, as a rule, by way of a remembrance or an asso-
ciated idea, and secondly of the ' effect,' namely, the reflexly
aroused vasomotor changes (changes in the blood supply
of the various organs and members of the body) and the
changes, mental and bodily, that depend upon them.
There is no affective intermediary between these two
terms. -^
which he remembers, e.g., 526 «., 535. No bodily change can be felt (the
reader will be on his guard for the differences of terminology between
James' book and the present work) unless it has attained a certain degree
irxt Danish work of 1885, Ont Sitidsbevcegeher, was translated into Ger*
man in 1887 under the title Ueber Gemuthsbewegungen : see pp. 47, 50, 76.
476 Emotion
Affection as Reflexly Excited Sensation. — In § 70 we gave a
brief account of some of the ways in which affection is regarded by
modern psychologists. The James-Lange theory of emotion sug-
gests yet another view : that the processes which, aroused by the
regular channels of adequate stimulation, appear as organic sen-
sations appear, when reflexly aroused, as affections. Mtinsterberg,
in fact, represents this view. " James, Lange and others have
taught us to regard the emotions as the mental effects of reflexly
excited peripheral processes. . . . We may extend this principle
of explanation from emotion to the simple feelings, and may
affirm that reflexly excited extensions and flexions are the condi-
tions of the conscious processes that we term pleasantness and
unpleasantness." What appears under the ordinary conditions of
stimulation as kinaesthesis or ' muscular sensation,' appears under
the conditions of reflex arousal as affection.^
Miinsterberg's theory of affection thus furnishes an affective
basis for the James-Lange theory of emotion ; the bodily rever-
beration of emotion would be affective, and not sensational, be-
cause it is set up directly, reflexly, through a preorganised nervous
mechanism. It must, however, be added that any such idea of
the transforming character of reflex excitation seems to have been
foreign to James' own thought ; the nervous processes upon which
emotions are conditioned are spoken of by him as ' sensational '
processes, without qualification. The theory itself has the obscurity
of all genetic (as opposed to nativistic) theories; it fails to
show us how the physiological fact of reflex excitation can change
the mental process correlated with muscular contraction from sen-
sation to affection.
§ 130. The ' James-Lange Theory ■' : Criticism and Modifica-
tion. — The theory of emotion outlined in the previous
Section has been preeminently successful in ' getting itself
discussed.' Some psychologists hailed it as the ligbt of
a new psychological dispensation ; others as vigorously re-
^ H. Miinsterberg, Beiirage zur experiinentellen Psychologie, iv., 1S92, 227 ;
Grundzuge der Psychologie, i , 1900, 293.
§ 130. Criticism and Modification 477
jected it ; yet others, and they the wisest, went critically
to work upon it, examining arguments, weighing evidences,
considering objections. There can be no doubt that it has
exerted a profound influence upon current psychology,
though there can, in the author's opinion, be no doubt,
either, that its original formulation was one-sided and
exaggerated.
An obvious objection, for instance, is that the bodily
changes to which James refers may appear identically in
very different emotions. There are tears of joy and tears
of rage, as well as tears of sorrow ; we may strike in fear
or in cruelty, as well as in anger ; we may run as hard to
overtake a friend as we run from the pursuing bear ; we
may tremble from eagerness or from a maudlin sentimen-
tality, as well as from fright. This objection is fatal, if
we take James' earlier statements at their face value. In
replying to it and to other criticisms, James has offered a
revised version of his theory, whose divergence from the
original text is very variously estimated, but which seems
to the author to mark a definite retreat from an untenable
position.
There are two principal points to be noted. The first is
that James now admits the affective character of the per-
ception which initiates the emotion. He grants a pleasant-
ness or unpleasantness which seems immediately to inhere
in the sensible qualities of the perception, which is ' beaten
up together [with it] in our consciousness ' ; and while he
finds, in his own case, that this affection is a 'very mild
and, so to say, platonic affair,' he writes that "the primary
GefiiJilston [affective tone] may vary enormously in distinct-
ness [or, as we should say, in intensity] in different men."
It is not the affective character of emotion, therefore, that
478 Emotion
derives from the reflexly excited organic sensations, but
rather its specifically emotive character as a general seiz-
ure of excitement.-^ Secondly, James explains that the
perception which initiates the emotion is not the bare per-
ception of an object, but is the apprehension of 'a total
situation.
" ' Objects ' are certainly the primitive arousers of instinctive
reflex movements. But they take their place, as experience goes
on, as elements in total ' situations,' the other elements of which
may prompt to movements of an entirely different sort. As soon
as the object has become thus familiar and suggestive, its emotional
consequences . . . must start rather from the total situation which
it suggests than from its own naked presence." -
The object which starts the emotion is thus a great deal
more than a simple stimulus, transformed by a preorgan-
ised nervous mechanism into a secondar}^ or reflected
afferent discharge ; it is a total situation, to which the
organism responds along the line of acquired as well as of
congenital tendencies.
How far these two acknowledgments, of a primary af-
fection attaching to the perception, and of the situational
nature of the perception itself, — how far these admissions
alter the theory, the reader must decide. What remain to
constitute it are, first, the assignment of an instinctive basis
to the emotional reaction, and secondly the insistence on
organic sensations as the vehicle of a 'rank excitement.'
The James-Lange theory undoubtedly owes much of its vogue,
among English-speaking psychologists, to the manner of its pro-
pounding. The accounts of emotion in the psychological text-
1 W. James, The Physical Basis of Emotiou, in Psychol. Pci'iew, i.. 1S94,
523 ff. A like ' primary and immediate pleasure ' is accredited to the subtler
(moral, intellectual, aesthetic) emotions in Priiic. of Psychol., ii., 468; of. the
article iust quoted, 524.
^Ibid., 518.
§ 130. Criticism and Modificatioti 479
books had become too academic, too conventionalised, and James
brought us back to the crude and the raw of actual experience.
Nevertheless, it would be quite wrong — as well as being a poor
compliment to James and Lange — to suppose that the theory had
in it anything absolutely novel. Lange himself points out that his
vasomotor hypothesis had been anticipated, in a curiously complete
way, by Malebranche.^ And the emphasis on the organic constit-
uents of emotion is, in reality, as old as systematic psychology.
" In reply to the question : What is anger? " Aristotle writes, " the
speculative philosopher says it is the desire of retaliation or some-
thing of that sort, the naturalist says it is the seething of the peri-
cordial blood or heat. Which of these now, is the real physical
philosopher? I answer, it is the man who combines both of these
characters." ' There are passages in Descartes^ and Spinoza'* that
look in the same direction. In the first half of the nineteenth
century, the anatomist Henle defines emotions as " ideas in con-
nection with the bodily changes that they arouse, changes which
manifest themselves in consciousness either as sensations or as
dispositions \_Sti)nmu9ige?i] of the muscular system." ^ There is a
page of Lotze's Medicinische Psychologic that might have been
written by James in support of his theory,® and Maudsley, in 1867,
^ Ueber Gemuthsbewegi0igen, 88 ff. ; N. Malebranche, De la recherche de la
verite, [1674-5] tr. 1694, bk. v., ch. iii.
2 W. A. Hammond, Aristotle's Psychology, 1902, 8 (the translation has been
somewhat condensed); of. the whole passage, 6 ff., and also 211 f. ; H. Sie-
beck, Geschichte der Psychologie, I., ii., 1884, 89 f.
3 R. Descartes, Les passions de Came, 1649, arts. 27, 29, 33, 36-38, 46, etc.
Cf. D. Irons, Descartes and Modern Theories of E?notion, in Philos. Review,
iv., 1895, 291 ff.
* B. de Spinoza, Opera Posthiima, 1677 ; Ethic, tr. 1883 and later, pt. iii.,
def. 3. " By emotion I understand the affections of the body, by which the
power of acting of the body itself is increased, diminished, helped or hindered,
together with the idea of these affections." This conception underlies the
whole of the analytical treatment of emotion in pt. iii.
5 F. G. J. Henle, Handbuch der rationellen Pathologie, 1846, 257 ; cf. An-
thropologische Vortrage,\., 1876,64 (emotion is "ideation with nerve-sympa-
thies," that is, with organic sensations).
6 R. H, Lotze, Medicinische Psychologie oder Physiologic der Seek, 1852,
SI8.
480 Emotioii
lays stress both upon the organic basis of emotion and upon its
relation to instinct.^ This list of names might, without injustice
to James and Lange, be very greatly lengthened, while the psy-
chological parentage of the theory cannot, without injustice to
psychology, be entirely passed over. There was no James-Lange
theory before James and Lange ; but the originality of the theory
lies more in its formulation and — if one may so put things — in
its timehness than in its content.
The instinctive nature of the emotive reaction was clearly in-
dicated, in 1880, by Schneider,- — -who, again, had his predecessors.
It has been worked out recently, in systematic form, by McDougall.^
" Each of the principal instincts conditions some one kind of
emotional excitement whose quality is specific or peculiar to it."
McDougall couples in this way the following instincts and emotions
(the first member of every pair is the instinct, the second the cor-
responding emotion) : flight and fear, repulsion and disgust, curiosity
and wonder, pugnacity and anger, self-abasement and subjection;
self-assertion and elation, parental instinct and tender emotion.
The principle upon which this list is based, the principle that every
emotive situation appeals to preexisting determining tendencies,
is undoubtedly correct ; but the list itself is, just as certainly, a
matter of individual preference rather than of scientific finality.
Anger, e.g., cannot always be referred to pugnacity ; tender emo-
tion may be referred to other instincts than the parental. McDougall
mentions, further, a number of instincts with less well-defined emo-
tive reaction : the instinct of reproduction, the gregarious instinct,
the instincts of acquisition and construction. Yet there are well-
marked emotions of sexual love, of security or self-expansion, of
possession or self-extension, of success ; and if the names of these
latter emotions are strange, so are those of subjection and elation,
which McDougall admits among the primary emotions. But no
1 H. Maudsley, The Physiology \^and Patholog\^'\ </ J//;/(/, [1S67] 1S76,
348 ff.
'^ G. H. Schneider, Der thierische Wille, iSSo, 66, 96. 146. etc.
* W. McDougall, An Introduction to Social Psychology, 1908, 46 ff.; ci
Physiological Psychology, 1905, loS fi.
§ !3r. The Organic Reaction as Constitutive 481
ctassiftcalion of this sort can be complete until we have a psycho-
logical analysis of the various emotive consciousnesses.
§ 1 3 1 „ The Organic Reaction as Constitutive of Emotion. —
In the firsi form of his theory, in which emotion is identified
outright wkh organic sensation, James relied upon two
principal arguments. The one is that " if we fancy some
strong emotion, tind then try to abstract from our conscious-
ness of it all the feelings of its bodily symptoms, we find
we have nothing left behind, no ' mind-stuff ' out of which
the emotion can be constituted." The other is that there
are many pathological cases in which emotion is objectless ;
if, then, we accept the thcvory, we are able to bring these
pathological, unmotived emotions under a common scheme
with the normal emotions. The arguments are, of course,
strong or weak in themselves, and not in their relation to
any theory ; and we must accordingly examine the evidence
upon which they rest.
The first argument is logically inconclusive. I cannot, for in-
stance, fancy a sensation that is devoid of intensity ; yet the intensity
is not identical with the sensation. So the organic sensations might
be an integral part of the emotion, and yet not be the emotion.
James' appeal to cases of generalised anaesthesia, in which loss of
organic sensation is accompanied by apathy, does not help him ;
for a complete organic anaesthesia, without impairment of the
higher mental processes, is neither known nor, indeed, so far as our
present knowledge goes, conceivable.
The second argument depends upon the proof that there are, in
fact, wholly unmotived emotions. And this proof depends, again,
in very large measure, upon our definition of emotion and our stren-
uousness in seeking the motive. James declares that the organic
sensations of difficult breathing, fluttering heart, precordial anxiety,
crouching posture, etc., make up, in combination, the emotion of
morbid fear. But did not this complex, the first few times that it
21
482 Emotion
appeared, arouse what the medical dictionaries call the ' sense of
impending death ' ? And might not this motived fear leave behind
it a predisposition, which later on, when the active fear of death
had passed, would throw the organic sensations into the emotive
pattern? So with the "absolutely unmotived fear, anger, mel-
ancholy, or conceit " that we see in the asylums : they may be
interpreted as the unmotived descendants of motived emotions, as
due to an emotive predisposition ; they yield no evidence that an
organic complex is, in itself, an emotion. Normal experience here
throws light upon the abnormal. Some contrariety of experience
makes us sulky : we know that we are sulky, and know that we are
silly, but we go on sulking ; not, surely, in the sense that the mere
organic sensations of sulkiness persist, but in the further sense that
we take everything sulkily, are predisposed to be injured and to
brood over the injury.
It may be objected to the two arguments, on the positive side,
that a group of organic sensations is, after all, a group of organic
sensations ; palpitation of the heart is not, in itself, the emotion of
dread, and blushing is not, in itself, the emotion of shame. Since,
however, this objection can be met by the reference to reflex ex-
citation, it is necessary to scrutinise the organic sensations in more
detail. And it then appears that, so far as unaided observation takes
us, there is no necessary correspondence between emotion and organic
reaction either in intensity or in quality, either in time of appear-
ance or in duration. As regards intensity : there are a quiet joy and
a boisterous joy, a cool anger and an explosive anger ; the intensity
of emotion may be the same, but the organic reaction varies with
what we call temperament or mental constitution. The critic,
the connoisseur, the scholar, is usually a man of 'quiet enjoyment,'
— but there is no evidence that his enjoyment is less than that
of the Sunday tripper. As regards quality : the organic reaction
of an unexpected joy and a violent anger are, to a considerable ex-
tent, the same, while the emotions themselves are widely different.
James, it is true, has argued that extremes of emotion not only
express themselves in similar ways, but also — as his theory de-
mands — feel alike. In default of any systematic analysis, a state-
§ 131- TJie Organic Reaction as Constitutive 483
ment of this sort leaves us helpless. The author can only say that,
in so far as he has been privileged to experience extreme emotions,
they have felt very distinguishably different. As regards time : the
organic reaction may precede the emotion, as when we are fright-
ened, and shrink back before the feeling of fear arises ; it may
outlast the emotion, as when we reaUse that there is nothing to be
frightened about, but the breathlessness and trembling still persist ;
and it may come after the emotion, as when sorrow finds vent in
tears. All these observations lack precision ; but then so do the
arguments against which they are directed.
We conclude that the sensations of the organic reaction
cannot be identified with the emotion. They are, it is true,
an integral part of the typical emotive consciousness, — but
only because the emotion is, essentially, an affective re-
sponse to a situation which appeals to the organism's
instinctive tendencies. Looking at the emotion in this
broader light, we can understand the occurrence of its two
truncated forms. If an affective predisposition, on the
basis of instinctive tendencies, has been set up in the past,
then a present group of organic sensations may mean or
stand for the complete emotion. And if an emotion has
previously run its complete course, inclusive of the organic
sensations, then the inhibition or deferment of the organic
reaction, later on, does not of necessity destroy the emotion ;
the primary feeling, the affectively toned situation, may
now, in its turn, mean or stand for the complete emotion.
We are in presence of that process of mental reduction
which we found to be especially characteristic of the action
consciousness (§ 126).
The importance of organic sensations as factors in emotion is
shown in many current words and phrases which designate emotive
consciousnesses. We are oppressed by care ; we cannot bear
certain people; we are cast down by bad fortune, tickled by a
484 Emotion
comic incident, rubbed the wrong way by trifling annoyances,
under a great strain of anxiety ; we are heart-broken by sorrow,
our blood boils in anger, our heart sinks in fear. The heart, in-
deed, crops up in all sorts of emotive contexts : we do a thing to
our heart's content, we eat out our heart, we have our heart in
our mouth, we lay a matter to heart, we set our heart on something,
we take heart of grace, we wear our heart upon our sleeve. Ety-
mology takes us farther still. We are mortified, that is, bruised
or pounded, by some bit of behaviour; we are exasperated, that
is, roughened, by a friend's conduct. Anger means a choking or
strangling, — a group of organic sensations that we now attribute
rather to baffled or impotent anger than to anger itself; fear we
have already mentioned (p. 408) ; grief and sadness both mean
heaviness. With reminders like these, it should not be easy for
psychology to overlook the organic elements in emotion.
§ 132. The Organic Reaction as Expressive of Emotion. — ■
Since the core of every emotion is a feeling, we shall ex-
pect to find in emotion all the bodily manifestations of the
simple affection ; and we find, as a matter of fact, that
every emotion brings with it changes in pulse, respiration,
volume, involuntary movement and muscular strength. But
the situation which arouses emotion is a far more serious
matter to the organism than the single stimulus ; and the
bodily changes set up directly by the change in the nervous
system are therefore more intensive and far-reaching. In
particular, the organic reaction now extends to the secre-
tory organs. In fear, for instance, the salivary glands
cease to act, so that mouth and throat become dry ; the
body is bathed in a cold sweat ; there is a tendency to uri-
nation and diarrhoea. In the emotion of impotent rage
there is often a derangement of the liver ; in grief, an
excessive stimulation of the lachrymal glands. Here,
then, is a first kind of emotive reaction, which repeats,
§ 132. TJie Organic Reaction as Expressive 485
in intensified and extended form, the affective reaction
of § 71.
Again, the organism has to face the situation by way of
a bodily attitude, and the reasons for the special forms of
this attitude must be sought from biology. The frightened
animal, as we know, crouches down, the angry animal at-
tacks the object of its anger, the startled animal leaps
away from the unexpected impression. In the civilised
life of man, some of these actions have become unneces-
sary, and others are partially inhibited by acquired ten-
dencies. Nevertheless, the association of a definite group
of organic sensations to the perceived and felt situation
still persists. Although we do not crouch down, as if ac-
tually to hide ourselves from a stronger opponent, we do
shrink into ourselves when we are expecting censure or
bad news ; although we do not attack when we are angry,
we do clench the fist and brace ourselves as if in prepara-
tion for attack ; and although we do not leap away, we do
jump or start when we are surprised. In the wince and
brace and start we have survivals of the primitive adjust-
ment by which the organism faced certain typical situa-
tions ; ^ and our own emotion is not complete until the
organic sensations aroused by them have been added to
the perception and ideas comprised in the central feeling.
Here is a second kind of organic reaction, which has an
evolutionary sanction.
When, however, we speak in ordinary conversation of
'expression,' we mean the expression of the face. The
facial muscles are arranged about three very important
sense-organs, those of vision, smell and taste, and their
1 Once more, for caution's sake, the reader may be referred to the foi-oote
on p. 408.
486 Emotion
adjustment forms part of the total bodily adjustment to the
many situations that appeal to those senses. But that is
not all. It is a remarkable fact that the facial muscles con-
tribute to the expression of emotions in which they are not
directly concerned. Thus, the injured man looks bitter,
looks as he would look were an unpleasant morsel placed
upon his tongue ; the disappointed man looks sour ; the
wooed maiden looks sweet. Here is a third kind of organic
reaction, which is not as readily explicable as that which we
have just discussed.
Again, however, there seems to be an evolutionary
reason for the expression. Primitive language was essen-
tially concrete and partial, or — as we should now say — ■
metaphorical. And since the one thing necessary, in a
primitive society, is food, we may suppose that primitive
metaphors would derive, to a large extent, from the
preparing and obtaining of food, from cooking and hunt-
ing. So the first association to be aroused in a man's
mind under pleasant circumstances might very well have
been an idea of sweet or palatable food ; and the first as-
sociation, under unpleasant circumstances, an idea of some-
thing sour or bitter. Even now we speak of the sweets of
love and of revenge, of tainted money, of tasting success,
of going on to the bitter end. But whenever a situation
brings one of these metaphors to consciousness, the corre-
lated movements of the facial muscles will also be aroused ;
and when, with the growth of language and the genesis of
abstract terms, the metaphor has lapsed, the expressive
movements may still persist. In a word, we must suppose
that some part-process in the central feeling is connected
with the facial reflex by a nerve-path which, originally
leading through the associated metaphor, now runs straight
from term to term.
§ 132. The Organic Reaction as Expressive 487
The classification, under general principles, of the various forms
of emotive expression has been a favourite task with psychologists
since Darwin published, in 1872, his work on The Expression of
Emotion in Alan and Animals. Any discussion must be largely
hypothetical ; and most discussions assume that actions are
motived and clinched by pleasantness and unpleasantness. We
shall not go into details ; the reader who desires to follow the sub-
ject will find references on p. 504 : but we may take advantage of
Darwin's classification to call attention to a common misunder-
standing.
Darwin's first principle, of 'serviceable associated habits,' covers
the instances given under our second heading. His second
principle, of ' antithesis,' is formulated as follows : " Certain states
of the mind lead to certain habitual actions, which are of service,
as under our first principle. Now when a directly opposite state
of mind is induced, there is a strong and involuntary tendency to
the performance of movements of a directly opposite nature, al-
though they are of no use ; and such movements are in some
cases highly expressive." This purely negative principle has re-
ceived short shrift from critics, although many of them have them-
selves been guilty of the misunderstanding referred to above.
There is a widespread tendency to regard the fundamental animal
impulses as of two distinct kinds : the impulse towards, and the im-
pulse away from, the positive and the negative impulse. Yet the
adoption of this position leads to nothing but perplexity. It is
clear that the distinction cannot be made for man ; we run in the
same way to escape from a pursuing bull and to catch a train ;
we dance for joy and for vexation ; the movement of approach may
signify welcome or rage. But neither can it be made for the
lower animals. The animal meets a situation by its most deeply
ingrained instinctive reaction ; if the reaction is inadequate, it does
something else ; and if that, too, proves inadequate, it does some-
thing else again : this is the procedure that has come to be known,
of late years, as the ' method of trial and error.' Should it appear
that the- creature has but two reactions at its disposal, a seeking
and an avoiding reaction, we should have found an extreme case
of the stereotyping of instinctive tendencies ; but we should be
488 Emotion
unwise to generalise from it. The instinctive temptation to classify
by pairs is very great (p. 464) ; let us realise that it may also be
very misleading.
The Law of Dynamogenesis. — We frequently find in psycho-
logical text-books a statement to the effect that " every state of
consciousness tends to reahse itself in an appropriate muscular
movement " ; ^ that " every possible feeHng produces a movement,
and that the movement is a movement of the entire organism,
and of each and all its parts " " ; that " every change in experience,
whether it is initiated by a change in the sensory stimulus or by
some internal cause, is accompanied by changes in muscular ten-
sion." ^ The formulations of this law of dynamogenesis, as it is
called, are usually sweeping, and do not always tally. In general,
however, they carry two implications : that the reflex arc is the
unit, the typical unit of function, of the human nervous system ;
and that psychology must take account, not only of the afferent
process which is correlated with sensation, but also of the
efferent process which prompts the organism's response to stimu-
lation.
There can, now, be no doubt that on the whole, and apart from
special theories, modern psychology has tended to one-sidedness
in its references to the body ; it has been too easily satisfied with
appeal to the organs of sense and to the doctrine of cerebral local-
isation. This state of things is changing, and changing rapidly.
Along with the analysis of the kinaesthetic complexes has come
the recognition that consciousness is limited, shaped, directed,
modified by physiological factors hitherto overlooked by an ex-
planatory psychology. We are coming, e.g., to speak and think
more and more in terms of such concepts as facilitation, inhibition,
preparation, sensory and motor attitude or predisposition, cortical
set ; and we are beginning to realise that our knowledge of the
1 J. M. Baldwin, Handbook of Psychology : Feeling and Will, 1891, 281;
Mental Development in the Child and the Race : Methods and Processes, 1906,
157. Cf. the ' law of diffusion ' as stated by A. Bain, Emotions and Will,
1880, 4.
2 W. James, Principles of Psychology, ii., 1890, 372.
3 C. H. Judd, Psychology, 1 907, 1S6.
§ 133- The Foiins of Eviotion 489
motor mechanisms of the organism must be as exact and detailed
as our knowledge of the sensory.
While, however, the author freely grants that, to this extent, the
insistence on the efferent nervous process is timely and warranted,
he is not convinced that we may speak, in any but a very circum-
scribed way, of a law of dynamogenesis. Let us write for ' move-
ment ' the phrase ' muscular tension,' so that movement includes
inhibition ; let us extend the meaning of muscular tension to cover
glandular activities ; and let us leave out of account the fact of the
liraen. Still it remains doubtful whether every excitation that cor-
responds to sensation or image tends to a motor conclusion.
There may perfectly well be a diffusion within the central nervous
system itself, so that the terminus of the excitatory process is a
neural rather than a muscular ' tension.' The assumption that the
reflex arc is the unit of nerve-function evidently makes the brain
nothing more, in principle, than a mass of superposed reflex arcs ;
the central is assimilated to the peripheral nervous mechanism;
the ofBce of the brain is to receive, to couple up, and to send out.
But this view, that the nervous system is a system of conduction,
a sort of glorified telephone exchange, is in the author's opinion
wholly inadequate to explain the phenomena of mind. The theory
of conduction, with obstacles or easements between cell and cell,
must, he believes, be replaced by a theory of intracellular change,
of change within the cell-body ; and if this is the case, the cortex
may be regarded rather as a disjunction of the reflex arc than as a
switchboard for the manifold connection of afferent with efferent
process.
Facts are facts ; it would be worse than useless to deny the fact
of the organic reaction. But speculations are also speculations ;
and we have no right to generalise the facts, in the interests of a
reflex theory, beyond the range of observation. The law of dyna-
mogenesis has a known degree and form of validity ; there is no
proof that it is a fundamental and universal law of explanatory
psychology.
, § 133. The Forms of Emotion. ^ Very many attempts
have been made to classify the emotions, to group them
490 Emotion
in accordance with some principle that shall show their
genesis and relationship. No attempt has been, and no
attempt can be, more than partially successful. Emotions
are processes of complex structure and of variable course ;
their analysis is yet in its first beginnings ; the names by
which we know them are, as a rule, class names, drawn
from popular usage, and not terms of any scientific pre-
cision. All that can be done at present, therefore, is to
indicate one or two of the ways in which classification
might be tried, without prospect of any final result.
An emotion appears when a situation or predicament
arises. If, then, we could ascertain the typical situations
which an organism placed in the world of nature must
face, the simplest and most inevitable situations of the
physical world, we might perhaps determine the funda-
mental emotions. It is more probable, however, that we
should end with some sort of biological schema of food
emotions, chase emotions, sex emotions, and so forth, —
a schema that would embody our own reflective interpre-
tation of the situations, rather than a psychological classi-
fication of the situations themselves.
All emotions are coloured by the organic sensations set
up during the adjustment of the physical organism to the
situation. If, then, we could find typical groups of organic
sensations — lung, heart, secretory sensations — appearing
in the various emotions, we could, again, determine the
fundamental forms. So far, however, we have neither
physiological nor psychological data for working out a
classification upon this basis.^
Emotions fall into two great groups according as the
1 E. Murray, Organic Sensation, in American Journal of Psychology, xx..
1909, 421,
§ 133- The Fonns of Emotion 49 1
situations that arouse them are immediately insistent, or
reach a cHmax of emotional appeal only in course of time.
Joy and sorrow may be taken as typical of the former
group ; they are emotions that may be set up, for instance,
by the receipt of a telegram. Hope and fear may be
taken as typical of the second group ; it may be many
days before we venture to hope for the recovery of a
friend from a serious illness or operation, or before we let
ourselves fear that something has happened to the acquaint-
ance from whom no news has come.
We said in § 128 that it was characteristic of an emotion to
begin suddenly, and to die down slowly. What, then, of hope and
fear? Do Ihey not begin gradually, and die down quickly? It
is as the reader chooses ; it all depends upon our definition of
emotion. To the author it seems best to reserve the term emo-
tion for the domination of consciousness by an affective situation
(primary attention) ; and, from his own observation, he believes
that this domination occurs abruptly, — that there is a particular
moment at which hope or fear takes possession of the mind, —
and that both hope and fear, if left to themselves, pass by slow
degrees into indifference. There are, of course, many things to
be taken into account : the ambiguity of language, the possible
resolution of hope and fear upon disappointment or relief, the re-
currence of emotion after a first disappearance. And it should be
said that Wundt, who speaks with authority on the matter, distin-
guishes no less than four modes of the emotive course : the irrup-
tive, which rises quickly and falls slowly ; the gradual, which rises
slowly and falls relatively quickly ; the remittent, which is the
normal mode of any persistent emotion ; and the oscillatory,
which shows an alternation of pleasurable and unpleasurable feeling.
Lastly, emotions fall into two great groups according as
they are pleasant or unpleasant. The opposition of affect-
ive quality (p. 232) affords a true psychological basis for
classification, though it does not carry us very far. It is
492 Emotion
responsible for the triads of emotive terms that we find in
the dictionaries: joy, composure, sorrow; like, unconcern,
dislike ; sympathy, apathy, antipathy ; attraction, insensi-
bility, repulsion. Experience shows that some men are
strongly moved by events that leave others unmoved, and
language has accordingly coined terms both for the emo-
tions proper and for the corresponding states of indifference.
It has often been said that language is richer in words for un-
pleasant than for pleasant emotions ; and Wundt has explained
this difference on the ground that "the joyous emotions appear
to be more uniform, less variously coloured, than the sorrowful."
The author is disposed to doubt both statements. Memory is
very untrustworthy at the best, as anyone may convince himself by
trying to inventory, from memory, the contents of a f^irailiar room.
And memory is strongly influenced by predisposition ; if we try
to make out a list of words, with the idea that the tale of un-
pleasant emotions is the longer, we shall find what we expected.
Systematic study of a condensed dictionary, in any of the principal
modern languages, reveals a wealth of terms for the pleasurable
emotions ; and the terms, as they come, have their specific
emotive feels upon them.
Composite Emotions. — There are, no doubt, composite emo-
tions, as there are composite perceptions ; a situation may contain
in it the stimuli to two or more emotions, and the concurrence of
these stimuli will make itself felt in the resultant consciousness.
Some psychologists regard the resultant as a mode of psychical
fusion : contempt, e.^., is a binary compound of disgust and ela-
tion, scorn a ternary compound of anger, disgust and elation ;
loathing is a compound of fear and disgust, fascination a compound
of loathing and wonder. It seems evident, however, that this
analysis is logical and inferential, rather than introspective ; the
emotions are regarded as fixed experiences, with hard and fast
boundary lines ; the several stimuli are supposed to arouse each
its own definite emotion. The fusion, where it occurs, will
surely go deeper down; it will be physiological, a fusion of excita-
§ 134- Emotive Menioy 493
tory processes. And we have no reason to suppose that the term
' fusion ' covers the ground ; there may be inhibition and suppres-
sion, oscillation and alternation, as well as mixture. The whole
subject still awaits experimental enquiry.
§ 134. Emotive Memory. — It is a familiar fact of our
everyday experience, and it has been confirmed by experi-
ment, that the memory of past events is, for some persons,
accompanied by the affective processes that coloured
the events themselves, while for others it is entirely cold
and colourless, no matter how intensive the pleasantness or
unpleasantness of the original situation may have been.
Hence it has been suggested that psychology must recog-
nise, not only the various types of sense-memory (§ 114),
but also an affective or emotive memory-type. The French
psychologist Ribot, who is the protagonist of this doctrine,
sum.s up his position as follows : ^
" (i) The emotional memory is ;;// in the majority of people.
(2) In others, there is a half intellectual, half emotional memory,
i.e., the emotional elements are only revived partially, and with
difficulty, by help of the intellectual states associated with them.
(3) Others, and these the least numerous, have a true — i.e., com-
plete — emotional memory ; the intellectual element being only
a means of revival which is rapidly effaced."
Here, as so often in psychology, there is no dispute about
the facts ; the question is, how the facts are to be inter-
preted. In the author's opinion, the two extreme types
of observer are distinguished, not by the power or lack of
power to image an affection, — for there is no such thing
as an affective image, — but by the presence or absence,
in memory-complexes, of organic, and more especially of
visceral sensations. When a boy is flogged at school, he
has, besides the immediate pain of the flogging, all sorts of
^ T. Ribot, The Psychology of the Emotions, tr. 1897, *7^«
494 Emotion
anticipatory and subsequent stirs of organic sensation, —
flutterings, sinkings, ciiokings, breath-catchings, nauseas.
If, when he recalls the flogging in later life, the cortical ex-
citations that underlie his memory-ideas revive the splanch-
nic and other excitations that constitute the stimuli to or-
ganic sensations, then the scene comes back to him with
its affective colouring upon it. If, on the other hand, he
merely images or symboHses the scene, and the organic
sensations are not set up afresh with the process of recall,
then the memory is purely ' intellectual,' untinged by
emotion. These gross differences undoubtedly exist ; but
to speak of an emotive memory, and thus to suggest the
occurrence of an affective image, is seriously misleading.
It is clear, nevertheless, that on the James-Lange theory of
emotion, according to which the organic sensations are blended into
a feeling of rank excitement, the phrase ' emotive memory' may be
technically correct. In the author's belief, pleasantness and un-
pleasantness are distinct from sensation ; and, as they have not risen
to the levelof sensory clearness (pp. 260 f.), so they are not paralleled
by any purely central process of the niiaginal kind. Affection, as the
technical term goes, is always ' actual ' ; it appears always in the
same form ; it has no substitute or surrogate, as sensation has in
the image. If, however, the organic stirs are themselves affective,
then — in so far as we admit, from our own point of view, the
possibility of an organic image — affective memory is psychologi-
cally possible ; consciousness would consist of organic images and
the recognitive mood. But we have seen (p. 200) that organic
images are rare ; ^ so that, at least in the great majority of cases,
the organic stirs will also be actual ; the idea of the flogging will
call up, not images of the fluttering and choking, but fluttering and
choking sensations ; weaker, no doubt, than the originals, but of
the same actual sort. Such a reexperience or reinstatement of
1 An exception should, perhaps, be made for kinaesthesis; most observers
report the frequent occurrence of kinaesthetic images. At the same time,
these images, too, are commonly blended with weak kinaesthetic sensations.
§ 134- Emotive Memory 495
organic sensation, in sensory and not in imaginal terms, is assumed
in the account just given. Only, then, if the James-Lange theory
is accepted, and only if the observer is endowed above his fellows
with what we should call organic images, only under these circum-
stances can it be correct to speak of an emotive memory. And
since the presence or absence of organic commotion is characteris-
tic, not merely of the memory consciousness, but of all the other
intellectual processes as well, it is better to generalise the difference,
and to speak of cold and warm temperament, or of emotional and
unemotional mental constitution.
Affective Expansion and Affective Transfer. — The organic re-
action seems, further, to supply an explanation of two phenomena
which have been much discussed, but of which we have no thorough-
going analysis : the phenomena of affective expansion and affective
transfer. The former appears when the pleasantness or unpleasant-
ness of some isolated perception or some single event spreads over
the entire situation in which the perception is given, or extends to
the subsequent consciousnesses ; the latter appears when, e.g., the
pleasure that at first attached to something considered as a means
becomes transferred to the same thing considered as an end. A
casual remark overheard may spoil a whole day's enjoyment ;
the miser begins to amass his money in order that he may have
it to spend, and continues to amass it that he may have it to
keep.
What happens, in the first case, is that the remark sets up a
complex of unpleasantly toned organic sensations, and that this
organic feehng — reinforced by associations, sustained by affective
predisposition — persists and recurs until some stronger complex
of associative and determining tendencies throws the organism into
a new attitude. What happens in the second case is that the
pleasurable organic feeling, which at the beginning accompanied
the idea of money to spend, is later attached to the idea of money
to keep ; the organic reaction persists, although the situation is
only in part the same. These statements give, of course, only a
rough indication of the actual course of consciousness. They
show, however, — and this is the important point, — that there is
496 Emotion
no affective expansion or affective transfer, in any literal sense ;
the mechanism of both phenomena is sensory (cf. p. 378).
Affective Illusions. — We may speak of an affective illusion in
two senses : first, when we are mistaken as to the source of a feel-
ing, and, secondly, when we are mistaken as to the intensity or
quality of feeling itself. Illusions of the former kind are liable to
occur whenever affective expansion or affective transfer occurs ; we
may magnify some trifling annoyance into the occasion of our ill-
temper, when in reahty the ill-temper was there beforehand (ex-
pansion) ; and we may regard the present situation as the origina-
tor of a feeling which, in reality, has been carried over from a
widely different situation (transfer). These illusions may, as a rule,
be easily corrected by retrospection.
Illusions of the second kind are more interesting, and more dif-
ficult to explain. You think that you are deeply attached to a
friend ; he goes to another part of the world, and you find that his
absence is a matter of entire indifference. You think that 5'ou
have no particular liking for so-and-so ; he goes away, and you
miss him dreadfully. You are looking forward eagerly to a certain
event ; circumstances prevent your taking part in it, and you are
surprised to discover that you are relieved. You are oppressed
and gloomy in the anticipation of another event ; circumstances
hold you off from that, and you are surprised at your disappoint-
ment. How are these things to be accomited for? We can only
guess. For one thing, we must suppose that the situation as im-
agined rarely tallies exactly with the situation as presented ; and
we must remember that there is no possibility of their direct com-
parison ; we have to wait the event. For another thing, we all
have a tendency to overestimate the stability of our affective life.
This tendency may very possibl 
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