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All rights reserved 

Copyright, 1896, 1897, 1899, 

Set up and electrotyped. Published July, 1896. 

Revised Edition Under New Titxk 

Copyright, 1909, 1910, 


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. 




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 

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. 




§ 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 


§ 10. 
§ 12. 

§ 14- 

§ 16. 


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^ 


xii Contents 


§ 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 


§ 23. The Auditory Qualities 93 

§ 24. The Dependence of Auditory Sensation upon Wave-number of 



§ 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 


§ 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 


§ 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 


§ 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 



§ 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 



§ 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 





References for Further Reading 224 


§ 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 . 




§ 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 




Contents xv 


Spatial Pekceptions 


§ 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 


xvi Contents 



§ 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 


§ 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 


§ 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 


§128. The Nature of Emotion 471 

§ 129. The 'James-Lange Theory' of Emotion . . « . . 474 


XV] 1 

§ 130. 
§ 131- 
§ 132- 
§ 133- 
§ 134- 
§ 135- 
§ 136. 


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 

§ 139- 
§ 140. 
§ 141. 
§ 142. 
§ 143- 
§ 144- 
§ 145- 
§ 146. 
§ 147- 
§ 148. 


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 . 








§ 149, The Status of Psychology ........ 550 

References for Further Reading ....... 552 

Index of Names 553 

Index of Subjects ...>....... 556 



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 



Index of Figures 


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) 





§ 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 

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- 

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 

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 

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 

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., 


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 

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 

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- 

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 

§ 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 

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- 

§ 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 

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 

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, 

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- 


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. 


§ 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- 


§ 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 

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- 

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 

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 

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, 


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." 


§ 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 


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 

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 


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. 


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. 

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 


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 

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 


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 

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- 

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 


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. 


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 


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 

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 

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 


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, 

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 

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 

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 

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 

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. 


§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 


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 


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, 




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 


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 



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 


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. 



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 

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 

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. 


§ 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 


§ 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 

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 

§ 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, 


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 

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 

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 


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 



— 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 

§ 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. 


§ 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 

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- 

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 

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 

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- 

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 

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. 


§ 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. 


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 

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 

146 Cutaneous Senses 

the other side, it will be possible by introspective reference to 
follow the accounts given by authors who employ a different 

§ 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 

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 

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 .' 






§ 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 


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. 


§ 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. 


§ 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' 

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 

§ 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 

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 


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 

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- 

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. 


§ 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, 


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 

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 

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 

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 

§ 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. 


§ 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 


§ 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 

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. 


§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 

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 

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 

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 

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 

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 

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, 

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 

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 


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 : 


But we know, again from our experiments, that : 

and, of course. 

Ar) \r\' r] 

We have, then, finally : 


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 

§ 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. 


§ 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 

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 

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- 


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- 

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 

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 

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- 

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 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 

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- 



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 

§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- 



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. 



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 

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- 

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 : 


strengthened weakened 

Pleasantness Tension Calm 

.1 i I 

quickened 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 



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 

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. 


§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 


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 

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- 


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. 



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 

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 

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 — 

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 

§ 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 

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 



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. 



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 

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 



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- 

§ 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 

§ 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 

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 

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 

§ 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. 


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 

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 

^ 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. 



§ 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. 


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. 


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- 

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 

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- 

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 


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. 


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 


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 

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. 


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- 

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 

§ 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. 


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 


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 


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- 

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. 


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. 


§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- 


§ 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 

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 

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 

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 

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. 


§ 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. 


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 


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 


OF Stimuli 


Octave ..... 















Major third 

c, e 



Minor third 

c,e t? 



Major sixth 

c, a 



Minor sixth 





Subminor fifth . 

^,S 9 - 



Subminor seventh 

c,b \^ - 




Major second . 

c, d 



Minor second . 




Major seventh . 




Minor seventh . 




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 


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 

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- 


§ 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 

§ 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 


§ 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 

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 


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. 


§ 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 


§ 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- 


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 

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. 


§ 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 


§ 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 

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- 

§ 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 

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 

§ 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- 

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 

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. 


§ 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. 


§ 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 

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 

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 

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 

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- 

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 

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 

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- 

§ 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 

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 

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> 


§ 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. 


§ 121. The Reaction Experiment 


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 

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 

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 







Fig. 61. 



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 


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. 



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 

The approximate times for the two extreme modes of reaction 
are as follows (time-unit = i o-) : — 




Sound ..... 
Electrical cutaneous stimulus 



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 


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- 

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 

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- 

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 

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 

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- 

§ 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 

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 


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, 


§ 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 


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 

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- 

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 

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 

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 

" ' 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, 

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 


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- 

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- 

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 

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 

, § 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 

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 th