"Some years ago I saw in England, in Kew Gardens, for the first time,

araucarias, and I walked along the beds looking at these strange

plants, with their rigid bark and compact, short, scaly leaves, of

a sombre green, whose abrupt, rough, bristling form cut in upon the

fine softly-lighted turf of the fresh grass-plat. If I now inquire

what this experience has left in me, I find, first, the sensible

representation of an araucaria; in fact, I have been able to describe

almost exactly the form and color of the plant. But there is a

difference between this representation and the former sensations, of

which it is the present echo. The internal semblance, from which I

have just made my description, is vague, and my past sensations were

precise. For, assuredly, each of the araucarias I saw then excited in

me a distinct visual sensation; there are no two absolutely similar

plants in nature; I observed perhaps twenty or thirty araucarias;

without a doubt each one of them differed from the others in size, in

girth, by the more or less obtuse angles of its branches, by the more

or less abrupt jutting out of its scales, by the style of its texture;

consequently, my twenty or thirty visual sensations were different.

But no one of these sensations has completely survived in its echo;

the twenty or thirty revivals have blunted one another; thus upset and

agglutinated by their resemblance they are confounded together, and

my present representation is their residue only. This is the product,

or rather the fragment, which is deposited in us, when we have gone

through a series of similar facts or individuals. Of our numerous

experiences there remain on the following day four or five more or

less distinct recollections, which, obliterated themselves, leave

behind in us a simple colorless, vague representation, into which

enter as components various reviving sensations, in an utterly feeble,

incomplete, and abortive state.--_But this representation is not the

general and abstract idea. It is but its accompaniment,_ and, if I may

say so, the ore from which it is extracted. For the representation,

though badly sketched, is a sketch, the sensible sketch of a distinct

individual.... But my abstract idea corresponds to the whole class; it

differs, then, from the representation of an individual.--Moreover, my

abstract idea is perfectly clear and determinate; now that I possess

it, I never fail to recognize an araucaria among the various plants

which may be shown me; it differs then from the confused and floating

representation I have of some particular araucaria."[53]

In other words, a blurred picture is just as much a single mental fact

as a sharp picture is; and _the use of either picture by the mind to

symbolize a whole class of individuals is a new mental function,_

requiring some other modification of consciousness than the mere

perception that the picture is distinct or not. I may bewail the

indistinctness of my mental image of my absent friend. That does not

prevent my thought from meaning _him_ alone, however. And I may mean

all mankind, with perhaps a very sharp image of one man in my mind's

eye. The meaning is a function of the more 'transitive' parts of

consciousness, the 'fringe' of relations which we feel surrounding the

image, be the latter sharp or dim. This was explained in a previous

place (see Vol. I, p. 473 ff., especially the note to page 477), and

I would not touch upon the matter at all here but for its historical

interest.

Our ideas or images of past sensible experiences may then be either

distinct and adequate or dim, blurred, and incomplete. It is likely

that the different degrees in which different men are able to make

them sharp and complete has had something to do with keeping up such

philosophic disputes as that of Berkeley with Locke over abstract

ideas. Locke had spoken of our possessing 'the general idea of a

triangle' which "must be neither oblique nor rectangle, neither

equilateral, equicrural, nor scalenon, but all and none of these at

once." Berkeley says:

"If any man has the faculty of framing in his mind such an idea of a

triangle as is here described, it is in vain to pretend to dispute him

out of it, nor would I go about it. All I desire is that the reader

would fully and certainly inform himself whether _he_ has such an idea

or no."[54]

Until very recent years it was supposed by all philosophers that there

was a typical human mind which all individual minds were like, and

that propositions of universal validity could be laid down about such

faculties as 'the Imagination.' Lately, however, a mass of revelations

have poured in, which make us see how false a view this is. There are

imaginations, not 'the Imagination,' and they must be studied in detail.

INDIVIDUALS DIFFER IN IMAGINATION.

The first breaker of ground in this direction was Fechner, in 1860.

Fechner was gifted with unusual talent for subjective observation, and

in chapter xliv of his 'Psychophysik' he gave the results of a most

careful comparison of his own optical after-images, with his optical

memory-pictures, together with accounts by several other individuals

of their optical memory-pictures.[55] The result was to show a great

personal diversity. "It would be interesting," he writes, "to work up

the subject statistically; and I regret that other occupations have

kept me from fulfilling my earlier intention to proceed in this way."

Flechner's intention was independently executed by Mr. Galton, the

publication of whose results in 1880 may be said to have made an era in

descriptive Psychology.

"It is not necessary," says Galton, "to trouble the reader with my

early tentative steps. After the inquiry had been fairly started it

took the form of submitting a certain number of printed questions to a

large number of persons. There is hardly any more difficult task than

that of framing questions which are not likely to be misunderstood,

which admit of easy reply, and which cover the ground of inquiry. I

did my best in these respects, without forgetting the most important

part of all--namely, to tempt my correspondents to write freely in

fuller explanation of their replies, and on cognate topics as well.

These separate letters have proved more instructive and interesting by

far than the replies to the set questions.

"The first group of the rather long series of queries related to the

illumination, definition, and coloring of the mental image, and were

framed thus:

"'Before addressing yourself to any of the Questions on the

opposite page, think of some definite object--suppose it is your

breakfast-table as you sat down to it this morning--and consider

carefully the picture that rises before your mind's eye.

"'1. _Illumination._--Is the image dim or fairly clear? Is its

brightness comparable to that of the actual scene?

"'2. _Definition._--Are all the objects pretty well defined at the

same time, or is the place of sharpest definition at any one moment

more contracted than it is in a real scene?

"'3. _Coloring._--Are the colors of the china, of the toast,

bread-crust, mustard, meat, parsley, or whatever may have been on the

table, quite distinct and natural?'

"The earliest results of my inquiry amazed me. I had begun by

questioning friends in the scientific world, as they were the most

likely class of men to give accurate answers concerning this faculty

of visualizing, to which novelists and poets continually allude,

which has left an abiding mark on the vocabularies of every language,

and which supplies the material out of which dreams and the well-known

hallucinations of sick people are built.

"To my astonishment, I found that _the great majority of the men of

science to whom I first applied protested that mental imagery was

unknown to them,_ and they looked on me as fanciful and fantastic

in supposing that the words 'mental imagery' really expressed what

I believed everybody supposed them to mean. They had no more notion

of its true nature than a color-blind man, who has not discerned his

defect, has of the nature of color. They had a mental deficiency of

which they were unaware, and naturally enough supposed that those who

affirmed they possessed it were romancing. To illustrate their mental

attitude it will be sufficient to quote a few lines from the letter of

one of my correspondents, who writes:

"'These questions presuppose assent to some sort of a proposition

regarding the "mind's eye," and the "images" which it sees.... This

points to some initial fallacy.... It is only by a figure of speech

that I can describe my recollection of a scene as a "mental image"

which I can "see" with my "mind's eye."... I do not see it... any

more than a man sees the thousand lines of Sophocles which under due

pressure he is ready to repeat. The memory possesses it,' etc.

"Much the same result followed inquiries made for me by a friend among

members of the French Institute.

"On the other hand, when I spoke to persons whom I met _in general

society_, I found an entirely different disposition to prevail.

_Many men and a yet larger number of women, and many boys and girls,

declared that they habitually saw mental imagery, and that it was

perfectly distinct to them and full of color._ The more I pressed and

crossed-questioned them, professing myself to be incredulous, the

more obvious was the truth of their first assertions. They described

their imagery in minute detail, and they spoke in a tone of surprise

at my apparent hesitation in accepting what they said. I felt that I

myself should have spoken exactly as they did if I had been describing

a scene that lay before my eyes, in broad daylight, to a blind man

who persisted in doubting the reality of vision. Reassured by this

happier experience, I recommenced to inquire among scientific men,

and soon found scattered instances of what I sought, though in by no

means the same abundance as elsewhere. I then circulated my questions

more generally among my friends and through their hands, and obtained

replies... from persons of both sexes, and of various ages, and in the

end from occasional correspondents in nearly every civilized country.

"I have also received batches of answers from various educational

establishments both in England and America, which were made after

the masters had fully explained the meaning of the questions, and

interested the boys in them. These have the merit of returns derived

from a general census, which my other data lack, because I cannot

for a moment suppose that the writers of the latter are a haphazard

proportion of those to whom they were sent. Indeed I know of some

who, disavowing all possession of the power, and of many others who,

possessing it in too faint a degree to enable them to express what

their experiences really were, in a manner satisfactory to themselves,

sent no returns at all. Considerable statistical similarity was,

however, observed between the sets of returns furnished by the

schoolboys and those sent by my separate correspondents, and I may

add that they accord in this respect with the oral information I have

elsewhere obtained. The conformity of replies from so many different

sources which was clear from the first, the fact of their apparent

trustworthiness being on the whole much increased by cross-examination

(though I could give one or two amusing instances of break-down),

and the evident effort made to give accurate answers, have convinced

me that it is a much easier matter than I had anticipated to obtain

trustworthy replies to psychological questions. Many persons,

especially women and intelligent children, take pleasure in

introspection, and strive their very best to explain their mental

processes. I think that a delight in self-dissection must be a strong

ingredient in the pleasure that many are said to take in confessing

themselves to priests.

"Here, then, are two rather notable results: the one is the proved

facility of obtaining statistical insight into the processes of other

persons' minds, whatever _a priori_ objection may have been made

as to its possibility; and the other is that scientific men, as a

class, have feeble powers of visual representation. There is no doubt

whatever on the latter point, however it may be accounted for. My own

conclusion is that an over-ready perception of sharp mental pictures

is antagonistic to the acquirement of habits of highly-generalized

and abstract thought, especially when the steps of reasoning are

carried on by words as symbols, and that if the faculty of seeing the

pictures was ever possessed by men who think hard, it is very apt

to be lost by disuse. The highest minds are probably those in which

it is not lost, but subordinated, and is ready for use on suitable

occasions. I am, however, bound to say that the missing faculty seems

to be replaced so serviceably by other modes of conception, chiefly,

I believe, connected with the incipient motor sense, not of the

eyeballs only but of the muscles generally, that _men who declare

themselves entirely deficient in the power of seeing mental pictures

can nevertheless give lifelike descriptions_ of what they have seen,

and can otherwise express themselves as if they were gifted with a

vivid visual imagination. _They can also become painters of the rank

of Royal Academicians...._[56]

"It is a mistake to suppose that sharp sight is accompanied by

clear visual memory. I have not a few instances in which the

independence of the two faculties is emphatically commented on; and

I have at least one clear case where great interest in outlines and

accurate appreciation of straightness, squareness, and the like, is

unaccompanied by the power of visualizing. Neither does the faculty go

with dreaming. I have cases where it is powerful, and at the same time

where dreams are rare and faint or altogether absent. One friend tells

me that his dreams have not the hundredth part of the vigor of his

waking fancies.

"The visualizing and the identifying powers are by no means

necessarily combined. A distinguished writer on metaphysical topics

assures me that he is exceptionally quick at recognizing a face that

he has seen before, but that he cannot call up a mental image of any

face with clearness.

"Some persons have the power of combining in a single perception more

than can be seen at any one moment by the two eyes....

"I find that a few persons can, by what they often describe as a kind

of touch-sight, visualize at the same moment all round the image of

a solid body. Many can do so nearly, but not altogether round that

of a terrestrial globe. An eminent mineralogist assures me that he

is able to imagine simultaneously all the sides of a crystal with

which he is familiar. I may be allowed to quote a curious faculty

of my own in respect to this. It is exercised only occasionally and

in dreams, or rather in nightmares, but under those circumstances

I am perfectly conscious of embracing an entire sphere in a single

perception. It appears to lie within my mental eyeball, and to be

viewed centripetally.

"This power of comprehension is practically attained in many cases

by indirect methods. It is a common feat to take in the whole

surroundings of an imagined room with such a rapid mental sweep as to

leave some doubt whether it has not been viewed simultaneously. Some

persons have the habit of viewing objects as though they were partly

transparent; thus, if they so dispose a globe in their imagination as

to see both its north and south poles at the same time, they will not

be able to see its equatorial parts. They can also perceive all the

rooms of an imaginary house by a single mental glance, the walls and

floors being as if made of glass. A fourth class of persons have the

habit of recalling scenes, not from the point of view whence they were

observed, but from a distance, and they visualize their own selves as

actors on the mental stage. By one or other of these ways, the power

of seeing the whole of an object, and not merely one aspect of it, is

possessed by many persons.

"The place where the image appears to lie differs much. Most persons

see it in an indefinable sort of way, others see it in front of the

eye, others at a distance corresponding to reality. There exists a

power which is rare naturally, but can, I believe, be acquired without

much difficulty, of projecting a mental picture upon a piece of paper,

and of holding it fast there, so that it can be outlined with a

pencil. To this I shall recur.

"Images usually do not become stronger by dwelling on them; the first

idea is commonly the most vigorous, but this is not always the case.

Sometimes the mental view of a locality is inseparably connected with

the sense of its position as regards the points of the compass, real

or imaginary. I have received full and curious descriptions from very

different sources of this strong geographical tendency, and in one or

two cases I have reason to think it allied to a considerable faculty

of geographical comprehension.

"The power of visualizing is higher in the female sex than in the

male, and is somewhat, but not much, higher in public-school boys than

in men. After maturity is reached, the further advance of age does

not seem to dim the faculty, but rather the reverse, judging from

numerous statements to that effect; but advancing years are sometimes

accompanied by a growing habit of hard abstract thinking, and in

these cases--not uncommon among those whom I have questioned--the

faculty undoubtedly becomes impaired. There is reason to believe that

it is very high in some young children, who seem to spend years of

difficulty in distinguishing between the subjective and objective

world. Language and book-learning certainly tend to dull it.

"The visualizing faculty is a natural gift, and, like all natural

gifts, has a tendency to be inherited. In this faculty the tendency to

inheritance is exceptionally strong, as I have abundant evidence to

prove, especially in respect to certain rather rare peculiarities,...

which, when they exist at all, are usually found among two, three, or

more brothers and sisters, parents, children, uncles and aunts, and

cousins.

"Since families differ so much in respect to this gift, we may suppose

that races would also differ, and there can be no doubt that such

is the case. I hardly like to refer to civilized nations, because

their natural faculties are too much modified by education to allow

of their being appraised in an off-hand fashion. I may, however,

speak of the French, who appear to possess the visualizing faculty

in a high degree. The peculiar ability they show in prearranging

ceremonials and _fêtes_ of all kinds, and their undoubted genius for

tactics and strategy, show that they are able to foresee effects with

unusual clearness. Their ingenuity in all technical contrivances is an

additional testimony in the same direction, and so is their singular

clearness of expression. Their phrase 'figurez-vous,' or 'picture to

yourself,' seems to express their dominant mode of perception. Our

equivalent of 'imagine' is ambiguous.

* * * * *

"I have many cases of persons mentally reading off scores when

playing the pianoforte, or manuscript when they are making speeches.

One statesman has assured me that a certain hesitation in utterance

which he has at times is due to his being plagued by the image of

his manuscript speech with its original erasures and corrections. He

cannot lay the ghost, and he puzzles in trying to decipher it.

"Some few persons see mentally in print every word that is uttered;

they attend to the visual equivalent and not to the sound of the

words, and they read them off usually as from a long imaginary strip

of paper, such as is unwound from telegraphic instruments."

The reader will find further details in Mr. Galton's 'Inquiries

into Human Faculty,' pp. 83-114.[57] I have myself for many years

collected from each and all of my psychology-students descriptions of

their own visual imagination; and found (together with some curious

idiosyncrasies) corroboration of all the variations which Mr. Galton

reports. As examples, I subjoin extracts from two cases near the

ends of the scale. The writers are first cousins, grandsons of a

distinguished man of science. The one who is a good visualizer says:

"This morning's breakfast-table is both dim and bright; it is dim if

I try to think of it when my eyes are open upon any object; it is

perfectly clear and bright if I think of it with my eyes closed.--All

the objects are clear at once, yet when I confine my attention to any

one object it becomes far more distinct.--I have more power to recall

color than any other one thing: if, for example, I were to recall a

plate decorated with flowers I could reproduce in a drawing the exact

tone, etc. The color of anything that was on the table is perfectly

vivid.--There is very little limitation to the extent of my images:

I can see all four sides of a room, I can see all four sides of two,

three, four, even more rooms with such distinctness that if you should

ask me what was in any particular place in any one, or ask me to count

the chairs, etc., I could do it without the least hesitation.--The

more I learn by heart the more clearly do I see images of my pages.

Even before I can recite the lines I see them so that I could give

them very slowly word for word, but my mind is so occupied in looking

at my printed image that I have no idea of what I am saying, of the

sense of it, etc. When I first found myself doing this I used to think

it was merely because I knew the lines imperfectly; but I have quite

convinced myself that I really do see an image. The strongest proof

that such is really the fact is, I think, the following:

"I can look down the mentally seen page and see the words that

_commence_ all the lines, and from any one of these words I can

continue the line. I find this much easier to do if the words begin

in a straight line than if there are breaks. Example:

_Étant fait...._

_Tous...._

_A des...._

_Que fit...._

_Céres...._

_Avec...._

_Un fleur...._

_Comme...._

(_La Fontaine_ 8. iv.)"

The poor visualizer says:

"My ability to form mental images seems, from what I have studied of

other people's images, to be defective, and somewhat peculiar. The

process by which I seem to remember any particular event is not by

a series of distinct images, but a sort of panorama, the faintest

impressions of which are perceptible through a thick fog.--I cannot

shut my eyes and get a distinct image of anyone, although I used to

be able to a few years ago, and the faculty seems to have gradually

slipped away.--In my most vivid dreams, where the events appear like

the most real facts, I am often troubled with a dimness of sight which

causes the images to appear indistinct.--To come to the question of

the breakfast-table, there is nothing definite about it. Everything

is vague. I cannot say _what_ I see. I could not possibly count the

chairs, but I happen to know that there are ten. I see nothing in

detail.--The chief thing is a general impression that I cannot tell

exactly what I do see. The coloring is about the same, as far as I can

recall it, only very much washed out. Perhaps the only color I can see

at all distinctly is that of the table-cloth, and I could probably see

the color of the wall-paper if I could remember what color it was."

A person whose visual imagination is strong finds it hard to understand

how those who are without the faculty can think at all. _Some people

undoubtedly have no visual images at all worthy of the name,_[58] and

instead of _seeing_ their breakfast-table, they tell you that they

_remember_ it or _know_ what was on it. This knowing and remembering

takes place undoubtedly by means of verbal images, as was explained

already in Chapter IX, pp. 265-6.

* * * * *

_The study of Aphasia_ (see Vol. I, p. 54) _has of late years shown how

unexpectedly great are the differences between individuals in respect

of imagination._ And at the same time the discrepancies between lesion

and symptom in different cases of the disease have been largely cleared

up. In some individuals the habitual 'thought-stuff,' if one may so

call it, is visual; in others it is auditory, articulatory, or motor;

in most, perhaps, it is evenly mixed. The same local cerebral injury

must needs work different practical results in persons who differ in

this way. In one it will throw a much-used brain-tract out of gear;

in the other it may affect an unimportant region. A particularly

instructive case was published by Charcot in 1883.[59] The patient was

Mr. X., a merchant, born in Vienna, highly educated, master of German,

Spanish, French, Greek, and Latin. Up to the beginning of the malady

which took him to Professor Charcot, he read Homer at sight. He

could, starting from any verse out of the first book of the Iliad,

repeat the following verses without hesitating, by heart. Virgil

and Horace were familiar. He also knew enough of modern Greek for

business purposes. Up to within a year (from the time Charcot saw

him) he enjoyed an exceptional _visual_ memory. He no sooner thought

of persons or things, but features, forms, and colors arose with the

same clearness, sharpness, and accuracy as if the objects stood before

him. When he tried to recall a fact or a figure in his voluminous

polyglot correspondence, the letters themselves appeared before him

with their entire content, irregularities, erasures and all. At school

he recited from a mentally seen page which he read off line by line

and letter by letter. In making computations, he ran his mental eye

down imaginary columns of figures, and performed in this way the most

varied operations of arithmetic. He could never think of a passage in

a play without the entire scene, stage, actors, and audience appearing

to him. He had been a great traveller. Being a good draughtsman, he

used to sketch views which pleased him; and his memory always brought

back the entire landscape exactly. If he thought of a conversation, a

saying, an engagement, the place, the people, the entire scene rose

before his mind.

His _auditory memory_ was always deficient, or at least secondary. He

had no taste for music.

A year and a half previous to examination, after business-anxieties,

loss of sleep, appetite, etc., he noticed suddenly one day an

extraordinary change in himself. After complete confusion, there came

a violent contrast between his old and his new state. Everything about

him seemed so new and foreign that at first he thought he must be

going mad. He was nervous and irritable. Although he saw all things

distinct, he had entirely lost his memory for forms and colors. On

ascertaining this, he became reassured as to his sanity. He soon

discovered that he could carry on his affairs by using his memory in

an altogether new way. He can now describe clearly the difference

between his two conditions.

Every time he returns to A., from which place business often calls

him, he seems to himself as if entering a strange city. He views the

monuments, houses, and streets with the same surprise as if he saw

them for the first time. Gradually, however, his memory returns, and

he finds himself at home again. When asked to describe the principal

public place of the town, he answered, "I know that it is there, but

it is impossible to imagine it, and I can tell you nothing about it."

He has often drawn the port of A. To-day he vainly tries to trace its

principal outlines. Asked to draw a minaret, he reflects, says it is a

square tower, and draws, rudely, four lines, one for ground, one for

top, and two for sides. Asked to draw an arcade, he says, "I remember

that it contains semi-circular arches, and that two of them meeting

at an angle make a vault, but how it _looks_ I am absolutely unable

to imagine." The profile of a man which he drew by request was as if

drawn by a little child; and yet he confessed that he had been helped

to draw it by looking at the bystanders. Similarly he drew a shapeless

scribble for a tree.

He can no more remember his wife's and children's faces than he can

remember the port of A. Even after being with them some time they seem

unusual to him. He forgets his own face, and once spoke to his image

in a mirror, taking it for a stranger. He complains of his loss of

feeling for colors. "My wife has black hair, this I know; but I can no

more recall its color than I can her person and features." This visual

amnesia extends to dating objects from his childhood's years--paternal

mansion, etc., forgotten.

No other disturbances but this loss of visual images. Now when he

seeks something in his correspondence, he must rummage among the

letters like other men, until he meets the passage. He can recall

only the first few verses of the Iliad, and must _grope_ to read

Homer, Virgil, and Horace. Figures which he adds he must now whisper

to himself. He realises clearly that he must help his memory out with

auditory images, which he does with effort. _The words and expressions

which he recalls seem now to echo in his ear, an altogether novel

sensation for him._ If he wishes to learn by heart anything, a series

of phrases for example, he must _read them several times aloud_, so as

to impress his ear. When later he repeats the thing in question, the

sensation of inward hearing which precedes articulation rises up in

his mind. This feeling was formerly unknown to him. He speaks French

fluently; but affirms that he can no longer think in French; but must

get his French words by translating them from Spanish or German, the

languages of his childhood. He dreams no more in visual terms, but

only in words, usually Spanish words. A certain degree of verbal

blindness affects him--he is troubled by the Greek alphabet, etc.[60]

If this patient had possessed the auditory type of imagination from the

start, it is evident that the injury, whatever it was, to his centres

for optical imagination, would have affected his practical life much

less profoundly.

"_The auditory type_," says M. A. Binet,[61] "_appears to be rarer

than the visual._ Persons of this type imagine what they think of in

the language of sound. In order to remember a lesson they impress upon

their mind, not the look of the page, but the sound of the words. They

reason, as well as remember, by ear. In performing a mental addition

they repeat verbally the names of the figures, and add, as it were,

the sounds, without any thought of the graphic signs. Imagination

also takes the auditory form. 'When I write a scene,' said Legouvé to

Scribe, 'I _hear_; but you _see_. In each phrase which I write, the

voice of the personage who speaks strikes my ear. _Vous, qui êtes le

théâtre même_, your actors walk, gesticulate before your eyes; I am

a _listener_, you a _spectator_.'--'Nothing more true,' said Scribe;

'do you know where I am when I write a piece? In the middle of the

parterre.' It is clear that the _pure audile_, seeking to develop only

a single one of his faculties, may, like the pure visualizer, perform

astounding feats of memory--Mozart, for example, noting from memory

the _Miserere_ of the Sistine Chapel after two hearings; the deaf

Beethoven, composing and inwardly repeating his enormous symphonies.

On the other hand, the man of auditory type, like the visual, is

exposed to serious dangers; for if he lose his auditory images, he is

without resource and breaks down completely.

"It is possible that persons with hallucinations of hearing, and

individuals afflicted with the mania that they are victims of

persecution, may all belong to the auditory type; and that the

predominance of a certain kind of imagination may predispose to a

certain order of hallucinations, and perhaps of delirium.

* * * * *

"The _motor type_ remains--perhaps the most interesting of all, and

certainly the one of which least is known. Persons who belong to this

type [_les moteurs_, in French, _motiles_, as Mr. Galton proposes to

call them in English] make use, in memory, reasoning, and all their

intellectual operations, of images derived from movement. In order to

understand this important point, it is enough to remember that 'all

our perceptions, and in particular the important ones, those of sight

and touch, contain as integral elements the movements of our eyes and

limbs; and that, if movement is ever an essential factor in our really

seeing an object, it must be an equally essential factor when we see

the same object in imagination' (Ribot).[62] For example, the complex

impression of a ball, which is there, in our hand, is the resultant

of optical impressions of touch, of muscular adjustments of the eye,

of the movements of our fingers, and of the muscular sensations which

these yield. When we imagine the ball, its idea must include the

images of these muscular sensations, just as it includes those of the

retinal and epidermal sensations. They form so many _motor images_.

If they were not earlier recognized to exist, that is because our

knowledge of the muscular sense is relatively so recent. In older

psychologies it never was mentioned, the number of senses being

restricted to five.

"There are persons who remember a drawing better when they have

followed its outlines with their finger. Lecoq de Boisbaudran used

this means in his artistic teaching, in order to accustom his pupils

to draw from memory. He made them follow the outlines of figures with

a pencil held in the air, forcing them thus to associate muscular with

visual memory. Galton quotes a curious corroborative fact. Colonel

Moncrieff often observed in North America young Indians who, visiting

occasionally his quarters, interested themselves greatly in the

engravings which were shown them. One of them followed with care with

the point of his knife the outline of a drawing in the Illustrated

London News, saying that this was to enable him to carve it out the

better on his return home. In this ease the motor images were to

reinforce the visual ones. The young savage was a _motor_....[63]

When one's motor images are destroyed, one loses one's remembrance of

movements, and sometimes, more curiously still, one loses the power

of executing them. Pathology gives us examples in motor aphasia,

agraphia, etc. Take the case of agraphia. An educated man, knowing how

to write, suddenly loses this power, as a result of cerebral injury.

His hand and arm are in no way paralytic, yet he cannot write. Whence

this loss of power? He tells us himself: he no longer knows how. He

has forgotten how to set about it to trace the letters, he has lost

the memory of the movements to be executed, he has no longer the motor

images which, when formerly he wrote, directed his hand.... Other

patients, affected with word-blindness, resort to these motor images

precisely to make amends for their other deficiency.... An individual

affected in this way cannot read letters which are placed before his

eyes, even although his sight be good enough for the purpose. This

loss of the power of reading by sight may, at a certain time, be the

only trouble the patient has. Individuals thus mutilated succeed in

reading by an ingenious roundabout way which they often discover

themselves: it is enough that they should trace the letters with their

finger to understand their sense. What happens in such a case? How can

the hand supply the place of the eye? The motor image gives the key to

the problem. If the patient can read, so to speak, with his fingers,

it is because in tracing the letters he gives himself a certain number

of muscular impressions which are those of writing. In one word,

the patient reads by writing (Charcot): the feeling of the graphic

movements suggests the sense of what is being written as well as sight

would."[64]

The imagination of a blind-deaf mute like Laura Bridgman must be

confined entirely to tactile and motor material. _All blind persons

must belong to the 'tactile' and 'motile' types_ of the French authors.

When the young man whose cataracts were removed by Dr. Franz was shown

different geometric figures, he said he "had not been able to form from

them the idea of a square and a disk until he perceived a sensation of

what he saw in the points of his fingers, as if he really touched the

objects."[65]

Professor Stricker of Vienna, who seems to have the motile form of

imagination developed in unusual strength, has given a very careful

analysis of his own case in a couple of monographs with which all

students should become familiar.[66] His recollections both of his

own movements and of those of other things are accompanied invariably

by distinct muscular feelings in those parts of his body which would

naturally be used in effecting or in following the movement. In

thinking of a soldier marching, for example, it is as if he were

helping the image to march by marching himself in his rear. And if he

suppresses this sympathetic feeling in his own legs, and concentrates

all his attention on the imagined soldier, the latter becomes, as it

were, paralyzed. In general his imagined movements, of whatsoever

objects, seem paralyzed the moment no feelings of movement either in

his own eyes or in his own limbs accompany them.[67] The movements of

articulate speech play a predominant part in his mental life.

"When after my experimental work I proceed to its description, as

a rule I reproduce in the first instance only words, which I had

already associated with the perception of the various details of the

observation whilst the latter was going on. For speech plays in all my

observing so important a part that I ordinarily clothe phenomena in

words as fast as I observe them."[68]

Most persons, on being asked _in what sort of terms they imagine

words_, will say 'in terms of hearing.' It is not until their attention

is expressly drawn to the point that they find it difficult to say

whether auditory images or motor images connected with the organs of

articulation predominate. A good way of bringing the difficulty to

consciousness is that proposed by Stricker: Partly open your mouth and

then imagine any word with labials or dentals in it, such as 'bubble,

'toddle.' Is your image under these conditions distinct? To most

people the image is at first 'thick,' as the sound of the word would

be if they tried to pronounce it with the lips parted. Many can never

imagine the words clearly with the mouth open; others succeed after a

few preliminary trials. The experiment proves how dependent our verbal

imagination is on actual feelings in lips, tongue, throat, larynx, etc.

"When we recall the impression of a word or sentence, if we do not

speak it out, we feel the twitter of the organs just about to come

to that point. The articulating parts--the larynx, the tongue, the

lips--are all sensibly excited; a _suppressed articulation is in fact

the material of our recollection_, the intellectual manifestation, the

_idea_ of speech."[69]

The open mouth in Stricker's experiment not only prevents actual

articulation of the labials, but our feeling of its openness keeps

us from imagining their articulation, just as a sensation of glaring

light will keep us from strongly imagining darkness. In persons

whose auditory imagination is weak, the articulatory image seems to

constitute the whole material for verbal thought. Professor Stricker

says that in his own case no auditory image enters into the words of

which he thinks.[70] Like most psychologists, however, he makes of

his personal peculiarities a rule, and says that verbal thinking is

normally and universally an exclusively motor representation. _I_

certainly get auditory images, both of vowels and of consonants, in

addition to the articulatory images or feelings on which this author

lays such stress. And I find that numbers of my students, after

repeating his experiments, come to this conclusion. There is _at first_

a difficulty due to the open mouth. That, however, soon vanishes, as

does also the difficulty of thinking of one vowel whilst continuously

sounding another. What probably remains true, however, is that most men

have a less auditory and a more articulatory verbal imagination than

they are apt to be aware of. Professor Stricker himself has acoustic

images, and can imagine the sounds of musical instruments, and the

peculiar voice of a friend. A statistical inquiry on a large scale,

into the variations of acoustic, tactile, and motor imagination, would

probably bear less fruit than Galton's inquiry into visual images. A

few monographs by competent observers, like Stricker, about their own

peculiarities, would give much more valuable information about the

diversities which prevail.[71]

_Touch-images_ are very strong in some people. The most vivid

touch-images come when we ourselves barely escape local injury, or

when we see another injured. The place may then actually tingle with

the imaginary sensation--perhaps not altogether imaginary, since

goose-flesh, paling or reddening, and other evidences of actual

muscular contraction in the spot may result.

"An educated man," says a writer who must always be quoted when it

is question of the powers of imagination,[72] "told me once that on

entering his house one day he received a shock from crushing the

finger of one of his little children in the door. At the moment of his

fright he felt a violent pain in the corresponding finger of his own

body, and this pain abode with him three days."

The same author makes the following discrimination, which probably most

men could verify:

"On the skin I easily succeed in bringing out suggested sensations

wherever I will. But because it is necessary to protract the mental

effort I can only awaken such sensations as are in their nature

prolonged, as warmth, cold, pressure. Fleeting sensations, as those

of a prick, a cut, a blow, etc., I am unable to call up, because I

cannot imagine them _ex abrupto_ with the requisite intensity. The

sensations of the former order I can excite upon any part of the skin;

and they may become so lively that, whether I will or not, I have to

pass my hand over the place just as if it were a real impression on

the skin."[73]

_Meyer's account of his own visual images_ is very interesting; and

with it we may close our survey of differences between the normal

powers of imagining in different individuals.

"With much practice," he says, "I have succeeded in making it possible

for me to call up subjective visual sensations at will. I tried all

my experiments by day or at night with closed eyes. At first it was

very difficult. In the first experiments which succeeded the whole

picture was luminous, the shadows being given in a somewhat less

strong bluish light. In later experiments I saw the objects dark, with

bright outlines, or rather I saw outline drawings of them, bright on

a dark ground. I can compare these drawings less to chalk drawings on

a blackboard than to drawings made with phosphorus on a dark wall at

night, though the phosphorus would show luminous vapors which were

absent from my lines. If I wished, for example, to see a face, without

intending that of a particular person, I saw the outline of a profile

against the dark background. When I tried to repeat an experiment

of the elder Darwin I saw only the edges of the die as bright lines

on a dark ground. Sometimes, however, I saw the die really white and

its edges black; it was then on a paler ground. I could soon at will

change between a white die with black borders on a light field, and

a black die with white borders on a dark field; and I can do this at

any moment now. After long practice ... these experiments succeeded

better still. I can now call before my eyes almost any object which

I please, as a subjective appearance, and this in its own natural

color and illumination. I see them almost always on a more or less

light or dark, mostly dimly changeable ground. Even known faces I can

see quite sharp, with the true color of hair and cheeks. It is odd

that I see these faces mostly in profile, whereas those described [in

the previous extract] were all full-face. Here are some of the final

results of these experiments:

"1) Some time after the pictures have arisen they vanish or change

into others, without my being able to prevent it.

"2) When the color does not integrally belong to the object, I cannot

always control it. A face, e.g., never seems to me blue, but always

in its natural color; a red cloth, on the other hand, I can sometimes

change to a blue one.

"3) I have sometimes succeeded in seeing pure colors without objects;

they then fill the entire field of view.

"4) I often fail to see objects which are not known to me, mere

fictions of my fancy, and instead of them there will appear familiar

objects of a similar sort; for instance, I once tried to see a brass

sword-hilt with a brass guard, instead of which the more familiar

picture of a rapier-guard appeared.

"5) Most of these subjective appearances, especially when they were

bright, left after-images behind them when the eyes were quickly

opened during their presence. For example, I thought of a silver

stirrup, and after I had looked at it a while I opened my eyes and for

a long while afterwards saw its after-image.

"These experiments succeeded best when I lay quietly on my back and

closed my eyes. I could bear no noise about me, as this kept the

vision from attaining the requisite intensity. The experiments succeed

with me now so easily that I am surprised they did not do so at

first, and I feel as though they ought to succeed with everyone. The

important point in them is to get the image sufficiently intense by

the exclusive direction of the attention upon it, and by the removal

of all disturbing impressions."[74]

_The negative after-images which succeeded upon Meyer's imagination

when he opened his eyes_ are a highly interesting, though rare,

phenomenon. So far as I know there is only one other published report

of a similar experience.[75] It would seem that in such a case the

neural process corresponding to the imagination must be the entire

tract concerned in the actual sensation, even down as far as the

retina. This leads to a new question to which we may now turn--of what

is

THE NEURAL PROCESS WHICH UNDERLIES IMAGINATION?

The commonly-received idea is that it is only a milder degree of the

same process which took place when the thing now imagined was sensibly

perceived. Professor Bain writes:

"Since a sensation in the first instance diffuses nerve-currents

through the interior of the brain outwards to the organs of expression

and movement,--the persistence of that sensation, after the outward

exciting cause is withdrawn, can be but a continuance of the same

diffusive currents, perhaps less intense, but not otherwise different.

The shock remaining in the ear and brain, after the sound of thunder,

must pass through the same circles, and operate in the same way as

during the actual sound. We can have no reason for believing that,

in this self-sustaining condition, the impression changes its seat,

or passes into some new circles that have the special property of

retaining it. Every part actuated _after_ the shock must have been

actuated _by_ the shock, only more powerfully. With this single

difference of intensity, the mode of existence of a sensation existing

after the fact is essentially the same as its mode of existence during

the fact.... Now if this be the case with impressions _persisting_

when the cause has ceased, what view are we to adopt concerning

impressions _reproduced_ by mental causes alone, or without the aid

of the original, as in ordinary recollection? What is the manner of

occupation of the brain with a resuscitated feeling of resistance,

a smell or a sound? There is only one answer that seems admissable.

_The renewed feeling occupies the very same parts, and in the same

manner, as the original feeling, and no other parts, nor in any other

assignable manner._ I imagine that if our present knowledge of the

brain had been present to the earliest speculators, this is the only

hypothesis that would have occurred to them. For where should a past

feeling be embodied, if not in the same organs as the feeling when

present? It is only in this way that its identity can be preserved; a

feeling differently embodied would be a different feeling."[76]

It is not plain from Professor Bain's text whether by the 'same

parts' he means only the same parts _inside the brain_, or the same

_peripheral_ parts also, as those occupied by the original feeling.

The examples which he himself proceeds to give are almost all cases of

imagination of _movement_, in which the peripheral organs are indeed

affected, for actual movements of a weak sort are found to accompany

the idea. This is what we should expect. All currents tend to run

forward in the brain and discharge into the muscular system; and the

idea of a movement tends to do this with peculiar facility. But the

question remains: Do currents run _backward_, so that if the optical

centres (for example) are excited by 'association' and a visual object

is imagined, a current runs _down to the retina_ also, and excites that

sympathetically with the higher tracts? In other words, _can peripheral

sense-organs be excited from above, or only from without? Are they

excited in imagination?_ Professor Bain's instances are almost silent

as to this point. All he says is this:

"We might think of a blow on the hand until the skin were actually

irritated and inflamed. The attention very much directed to any part

of the body, as the great toe, for instance, is apt to produce a

distinct feeling in the part, which we account for only by supposing a

revived nerve-current to flow there, making a sort of false sensation,

an influence from within mimicking the influences from without in

sensation proper.--(See the writings of Mr. Braid, of Manchester, on

Hypnotism, etc.)"

If I may judge from my own experience, all feelings of this sort

are consecutive upon motor currents invading the skin and producing

contraction of the muscles there, the muscles whose contraction gives

'goose-flesh' when it takes place on an extensive scale. I never

get a _feeling_ in the skin, however strongly I _imagine_ it, until

some actual change in the condition of the skin itself has occurred.

The truth seems to be that the cases where peripheral sense-organs

are directly excited in consequence of imagination are exceptional

rarities, if they exist at all. _In common cases of imagination it

would seem more natural to suppose that the seat of the process is

purely cerebral, and that the sense-organ is left out._ Reasons for

such a conclusion would be briefly these:

1) In imagination the _starting-point_ of the process must be in the

brain. Now we know that currents usually flow one way in the nervous

system; and for the peripheral sense-organs to be excited in these

cases, the current would have to flow backward.

2) There is between imagined objects and felt objects a difference of

conscious quality which may be called almost absolute. It is hardly

possible to confound the liveliest image of fancy with the weakest

real sensation. The felt object has a plastic reality and outwardness

which the imagined object wholly lacks. Moreover, as Fechner says, in

imagination the attention feels as if drawn backwards to the brain; in

sensation (even of after-images) it is directed forward towards the

sense-organ.[77] The difference between the two processes feels like

one of kind, and not like a mere 'more' or 'less' of the same.[78] If a

sensation of sound were only a strong imagination, and an imagination

a weak sensation, there ought to be a border-line of experience where

we never could tell whether we were hearing a weak sound or imagining

a strong one. In comparing a present sensation felt with a past one

imagined, it will be remembered that we often judge the imagined one

to _have been the stronger_ (see above, Vol. I p. 500, note). This is

inexplicable if the imagination be simply a weaker excitement of the

sensational process.

To these reasons the following objections may be made:

To 1): The current demonstrably _does_ flow backward down the optic

nerve in Meyer's and Féré's negative after-image. Therefore it _can_

flow backward; therefore it _may_ flow backward in some, however

slight, degree, in all imagination.[79]

To 2): The difference alleged is not absolute, and sensation and

imagination _are_ hard to discriminate where the sensation is so weak

as to be just perceptible. At night hearing a very faint striking of

the hour by a far-off clock, our imagination reproduces both rhythm

and sound, and it is often difficult to tell which was the last real

stroke. So of a baby crying in a distant part of the house, we are

uncertain whether we still hear it, or only imagine the sound. Certain

violin-players take advantage of this in diminuendo terminations.

After the pianissimo has been reached they continue to bow as if still

playing, but are careful not to touch the strings. The listener hears

in imagination a degree of sound fainter still than the preceding

pianissimo. This phenomenon is not confined to hearing:

"If we slowly approach our finger to a surface of water, we often

deceive ourselves about the moment in which the wetting occurs. The

apprehensive patient believes himself to feel the knife of the surgeon

whilst it is still at some distance."[80]

Visual perception supplies numberless instances in which the same

sensation of vision is perceived as one object or another according

to the interpretation of the mind. Many of these instances will come

before us in the course of the next two chapters; and in Chapter

XIX similar illusions will be described in the other senses. Taken

together, all these facts would force us to admit that _the subjective

difference between imagined and felt objects is less absolute than

has been claimed, and that the cortical processes which underlie

imagination and sensation are not quite as discrete as one at first is

tempted to suppose. That peripheral sensory processes are ordinarily

involved in imagination seems improbable; that they may sometimes be

aroused from the cortex downwards cannot, however, be dogmatically

denied._

* * * * *

_The imagination-process_ CAN _then pass over into the

sensation-process._ In other words, genuine sensations _can_ be

centrally originated. When we come to study hallucinations in the

chapter on Outer Perception, we shall see that this is by no

means a thing of rare occurrence. At present, however, we must admit

that _normally the two processes do_ NOT _pass over into each other_;

and we must inquire why. One of two things must be the reason. Either

1. Sensation-processes occupy a different _locality_ from

imagination-processes; or

2. Occupying the same locality, they have an _intensity_ which under

normal circumstances currents from other cortical regions are incapable

of arousing, and to produce which currents from the periphery are

required.

_It seems almost certain_ (after what was said in Chapter II. pp.

49-51) _that the imagination-process differs from the sensation-process

by its intensity rather than by its locality._ However it may be with

lower animals, the assumption that ideational and sensorial centres

are locally distinct appears to be supported by no facts drawn from

the observation of human beings. After occipital destruction, the

hemianopsia which results in man is sensorial blindness, not mere

loss of optical ideas. Were there centres for crude optical sensation

below the cortex, the patients in these cases would still feel light

and darkness. Since they do not preserve even this impression on the

lost half of the field, we must suppose that there are no centres for

vision of any sort whatever below the cortex, and that the corpora

quadrigemina and other lower optical ganglia are organs for reflex

movement of eye-muscles and not for conscious sight. Moreover there are

no facts which oblige us to think that, within the occipital cortex,

one part is connected with sensation and another with mere ideation

or imagination. The pathological cases assumed to prove this are all

better explained by disturbances of conduction between the optical and

other centres (see p. 50). In bad cases of hemianopsia the patient's

images depart from him together with his sensibility to light. They

depart so completely that he does not even know what is the matter

with him. To perceive that one is blind to the right half of the field

of view one must have an idea of that part of the field's possible

existence. But the defect in these patients has to be revealed to them

by the doctor, they themselves only knowing that there is 'something

wrong' with their eyes. What you have no idea of you cannot miss; and

their not definitely missing this great region out of their sight seems

due to the fact that their very idea and memory of it is lost along

with the sensation. A man blind of his eyes merely, sees _darkness_.

A man blind of his visual brain-centres can no more see darkness out

of the parts of his retina which are connected with the brain-lesion

than he can see it out of the skin of his back. He cannot see at all in

that part of the field; and he cannot think of the light which he ought

to be feeling _there_, for the very notion of the existence of that

particular 'there' is cut out of his mind.[81]

Now if we admit that sensation and imagination are due to the activity

of the same centres in the cortex, we can see a very good teleological

reason why they should correspond to discrete kinds of process in these

centres, and why the process which gives the sense that the object is

really there ought normally to be arousable only by currents entering

from the periphery and not by currents from the neighboring cortical

parts. We can see, in short, why _the sensational process_ OUGHT TO _be

discontinuous with all normal ideational processes, however intense_.

For, as Dr. Münsterberg justly observes:

"Were there not this peculiar arrangement we should not distinguish

reality and fantasy, our conduct would not be accommodated to the

facts about us, but would be inappropriate and senseless, and we could

not keep ourselves alive.... That our thoughts and memories should

be copies of sensations with their intensity greatly reduced is thus

a consequence deducible logically from the natural adaptation of the

cerebral mechanism to its environment."[82]

Mechanically the discontinuity between the ideational and the

sensational kinds of process must mean that when the greatest

ideational intensity has been reached, an order of _resistance_

presents itself which only a new order of force can break through. The

current from the periphery is the new order of force required; and what

happens after the resistance is overcome is the sensational process. We

may suppose that the latter consists in some new and more violent sort

of disintegration of the neural matter, which now explodes at a deeper

level than at other times.

Now how shall we conceive of the 'resistance' which prevents this

sort of disintegration from taking place, this sort of intensity in

the process from being attained, so much of the time? It must be

either an intrinsic resistance, some force of cohesion in the neural

molecules themselves; or an extrinsic influence, due to other cortical

cells. When we come to study the process of hallucination we shall

see that both factors must be taken into account. There is a degree

of inward molecular cohesion in our brain-cells which it probably

takes a sudden inrush of destructive energy to spring apart. Incoming

peripheral currents possess this energy from the outset. Currents

from neighboring cortical regions might attain to it if they could

_accumulate_ within the centre which we are supposed to be considering.

But since during waking hours every centre communicates with others

by association-paths, no such accumulation can take place. The

cortical currents which run in run right out again, awakening the next

ideas; the level of tension in the cells does not rise to the higher

explosion-point; and the latter must be gained by a sudden current from

the periphery or not at all.

* * * * *

[49] Prof. Jastrow has ascertained by statistical inquiry among the

blind that if their blindness have occurred before a period embraced

between the fifth and seventh years the visual centres seem to decay,

and visual dreams and images are gradually outgrown. If sight is lost

after the seventh year, visual imagination seems to survive through

life. See Prof. J.'s interesting article on the Dreams of the Blind, in

the New Princeton Review for January 1888.

[50] Impression means sensation for Hume.

[51] Treatise on Human Nature, part i. § vii.

[52] Huxley's Hume, pp. 92-94.

[53] On Intelligence (N. Y.), vol. ii. p. 139.

[54] Principles, Introd. § 13. Compare also the passage quoted above,

vol. I, p. 469.

[55] The differences noted by Fechner between after-images and images

of imagination proper are as follows:

_After Images._ _Imagination-images._

Feel coercive; Feel subject to our spontaneity;

Seem unsubstantial, vaporous; Have, as it were, more body;

Are sharp in outline; Are blurred;

Are bright; Are darker than even the darkest

black of the after-images;

Are almost colorless; Have lively coloration;

Are continuously enduring; Incessantly disappear, and have to

be renewed by an effort of will.

At last even this fails to revive

them.

Cannot be voluntarily changed. Can be exchanged at will for

others.

Are exact copies of originals. Cannot violate the necessary laws

of appearance of their

originals--e.g., a man cannot be

imagined from in front and behind

at once. The imagination must walk

round him, so to speak;

Are more easily got with shut than Are more easily had with open than

with open eyes; with shut eyes;

Seem to move when the head or eyes Need not follow movements of head

move; or eyes.

The field within which they appear The field is extensive in three

(with closed eyes) is dark, contracted, dimensions, and objects can be

flat, close to the eyes, in imagined in it above or behind

front, and the images have no almost as easily as in front.

perspective;

The attention seems directed forwards In imagining, the attention feels

towards the sense-organ, in as if drawn backwards towards the

observing after-images. brain.

Finally, Fechner speaks of the impossibility of attending to both

after-images and imagination-images at once, even when they are of the

same object and might be expected to combine. All these differences are

true of Fechner; but many of them would be untrue of other persons. I

quote them as a type of observation which any reader with sufficient

patience may repeat. To them may be added, as a universal proposition,

that after-images seem larger if we project them on a distant screen,

and smaller if we project them on a near one, whilst no such change

takes place in mental pictures.

[56] [I am myself a good draughtsman, and have a very lively interest

in pictures, statues, architecture and decoration, and a keen

sensibility to artistic effects. But I am an extremely poor visualizer,

and find myself often unable to reproduce in my mind's eye pictures

which I have most carefully examined.--W. J.]

[57] See also McCosh and Osborne, Princeton Review, Jan. 1884. There

are some good examples of high development of the Faculty in the London

Spectator, Dec. 28, 1878, pp. 1631, 1634, Jan. 4, 11, 25, and March 18,

1879.

[58] Take the following report from one of my students: "I am unable

to form in my mind's eye any visual likeness of the table whatever.

After many trials, I can only get a hazy surface, with nothing on it or

about it. I can see no variety in color, and no positive limitations

in extent, while I cannot see what I see well enough to determine its

position in respect to my eye, or to endow it with any quality of size.

I am in the same position as to the word _dog_. I cannot see it in my

mind's eye at all; and so cannot tell whether I should have to run my

eye along it, if I did see it."

[59] Progrès Médical, 21 juillet. I abridge from the German report of

the case in Wilbrand: Die Seelenblindheit (188).

[60] In a letter to Charcot this interesting patient adds that his

character also is changed: "I was formerly receptive, easily made

enthusiastic, and possessed a rich fancy. Now I am quiet and cold, and

fancy never carries my thoughts away.... I am much less susceptible

than formerly to anger or sorrow. I lately lost my dearly-beloved

mother; but felt far less grief at the bereavement than if I had been

able to see in my mind's eye her physiognomy and the phases of her

suffering, and especially less than if I had been able to witness in

imagination the outward effects of her untimely loss upon the members

of the family."

[61] Psychologie du Raisonnement (1886), p. 25.

[62] [I am myself a very poor visualizer, and find that I can seldom

call to mind even a single letter of the alphabet in purely retinal

terms. I must trace the letter by running my mental eye over its

contour in order that the image of it shall have any distinctness at

all. On questioning a large number of other people, mostly students,

I find that perhaps half of them say they have no such difficulty in

seeing letters mentally. Many affirm that they can see an entire word

at once, especially a short one like 'dog,' with no such feeling of

creating the letters successively by tracing them with the eye.--W. J.]

[63] It is hardly needful to say that in modern primary education, in

which the blackboard is so much used, the children are taught their

letters, etc., by all possible channels at once, sight, hearing, and

movement.

[64] See an interesting case of a similar sort, reported by Farges, in

l'Encéphale, 7me Année, p. 545.

[65] Philosophical Transactions, 1841, p. 65.

[66] Studien über die Sprachvorstellungen (1880), and Studien über die

Bewegungsvorstellungen (1882).

[67] Prof. Stricker admits that by practice he has succeeded in making

his eye-movements 'act vicariously' for his leg-movements in imagining

men walking.

[68] Bewegungsvorstellungen, p. 6.

[69] Bain: Senses and Intellect, p. 339.

[70] Studien über Sprachvorstellungen, 28, 31, etc. Cf. pp. 49-50,

etc. Against Stricker, see Stumpf, Tonpsychol., 155-162, and Revue

Philosophique, xx. 617. See also Paulhan, Rev. Philosophique, xvi.

405. Stricker replies to Paulhan in vol. xviii. p. 685. P. retorts in

vol. xix p. 118. Stricker reports that out of 100 persons questioned

he found only _one_ who had _no_ feeling in his lips when silently

thinking the letters M, B, P; and out of 60 only _two_ who were

conscious of no internal articulation whilst reading (pp. 59-60).

[71] I think it must be admitted that some people have no vivid

substantive images in _any_ department of their sensibility. One of my

students, an intelligent youth, denied so pertinaciously that there

was _anything_ in his mind _at all_ when he thought, that I was much

perplexed by his case. I myself certainly have no such vivid play of

nascent movements or motor images as Professor Stricker describes. When

I seek to represent a row of soldiers marching, all I catch is a view

of stationary legs first in one phase of movement and then in another,

and these views are extremely imperfect and momentary. Occasionally

(especially when I try to stimulate my imagination, as by repeating

Victor Hugo's lines about the regiment,

"Leur pas est si correct, sans tarder ni courir,

Qu'on croit voir des ciseaux se fermer et s'ouvrir,")

I seem to get an instantaneous glimpse of an actual movement, but it is

to the last degree dim and uncertain. All these images seem at first as

if purely retinal. I think, however, that rapid eye-movements accompany

them, though these latter give rise to such slight feelings that they

are almost impossible of detection. Absolutely no leg-movements of my

own are there; in fact, to call such up arrests my imagination of the

soldiers. My optical images are in general very dim, dark, fugitive,

and contracted. It would be utterly impossible to _draw_ from them, and

yet I perfectly well distinguish one from the other. My auditory images

are excessively inadequate reproductions of their originals. I have

_no_ images of taste or smell. Touch-imagination is fairly distinct,

but comes very little into play with most objects thought of. Neither

is all my thought verbalized; for I have shadowy schemes of relation,

as apt to terminate in a nod of the head or an expulsion of the breath

as in a definite word. On the whole, vague images or sensations of

movement inside of my head towards the various parts of space in which

the terms I am thinking of either lie or are momentarily symbolized

to lie together with movements of the breath through my pharynx and

nostrils, form a by no means inconsiderable part of my _thought-stuff_.

I doubt whether my difficulty in giving a clearer account is wholly

a matter of inferior power of introspective attention, though that

doubtless plays its part. Attention, _ceteris paribus_, must always be

inferior in proportion to the feebleness of the internal images which

are offered it to hold on to.

[72] Geo. Herm. Meyer, Untersuchungen üb. d. Physiol. d. Nervenfaser

(1843), p. 233. For other cases see Tuke's Influence of Mind upon Body,

chaps. ii. and vii.

[73] Meyer, _op. cit._ p. 238.

[74] Meyer, _op. cit._ pp. 238-41.

[75] That of Dr. Ch. Féré in the Revue Philosophique, xx. 364. Johannes

Müller's account of hypnagogic hallucinations floating before the eyes

for a few moments after these had been opened, seems to belong more to

the category of spontaneous hallucinations (see his Physiology, London,

1843, p. 1394). It is impossible to tell whether the words in Wundt's

Vorlesungen, i. 387, refer to a personal experience of his own or not;

probably not. _Il va sans dire_ that an inferior visualizer like myself

can get no such after-images. Nor have I as yet succeeded in getting

report of any from my students.

[76] Senses and Intellect, p. 338.

[77] See above, note 55.

[78] V. Kandinsky (Kritische u. klinische Betrachtungen im Gebiete der

Sinnestäuschungen (Berlin, 1885), p. 135 ff.) insists that in even the

liveliest pseudo-hallucinations (see below, Chapter XX), which may be

regarded as the intensest possible results of the imaginative process,

there is no outward objectivity perceived in the thing represented, and

that a _ganzer Abgrund_ separates these 'ideas' from true hallucination

and objective perception.

[79] It seems to also flow backwards in certain hypnotic

hallucinations. Suggest to a 'Subject' in the hypnotic trance that a

sheet of paper has a red cross upon it, then pretend to remove the

imaginary cross, whilst you tell the Subject to look fixedly at a

dot upon the paper, and he will presently tell you that he sees a

'bluish-green' cross. The genuineness of the result has been doubted,

but there seems no good reason for rejecting M. Binet's account (Le

Magnetisme Animal, 1887, p. 188). M. Binet, following M. Parinaud,

and on the faith of a certain experiment, at one time believed, the

optical brain-centres and not the retina to be the seat of ordinary

negative after-images. The experiment is this: Look fixedly, with one

eye open, at a colored spot on a white background. Then close that eye

and look fixedly with the _other_ eye at a plain surface. A negative

after-image of the colored spot will presently appear. (Psychologie

du Raisonnement, 1886, p. 45.) But Mr. Delabarre has proved (American

Journal of Psychology, ii. 326) that this after-image is due, not to a

higher cerebral process, but to the fact that the retinal process in

the _closed_ eye affects consciousness at certain moments, and that its

object is then projected into the field seen by the eye which is open.

M. Binet informs me that he is converted by the proofs given by Mr.

Delabarre.

The fact remains, however, that the negative after-images of Herr

Meyer, M. Féré, and the hypnotic subjects, form an exception to

all that we know of nerve-currents, if they are due to a refluent

centrifugal current to the retina. It may be that they will hereafter

be explained in some other way. Meanwhile we can only write them down

as a paradox. Sig. Sergi's theory that there is _always_ a refluent

wave in perception hardly merits serious consideration (Psychologie

Physiologique, pp. 99, 189). Sergi's theory has recently been

reaffirmed with almost incredible crudity by Lombroso and Ottolenghi in

the Revue Philosophique, xxix. 70 (Jan. 1890).

[80] Lotze, Med. Psych. p. 509.

[81] See an important article by Binet in the Revue Philosophique,

xxvi. 481 (1888); also Dufour, in Revue Méd. de la Suisse Romande,

1889. No. 8, cited in the Neurologisches Centralblatt, 1890. p. 48.

[82] Die Willenshandlung (1888), pp. 129-40.

CHAPTER XIX.

THE PERCEPTION OF 'THINGS.'

PERCEPTION AND SENSATION COMPARED.

A pure sensation we saw above, p. 7, to be an abstraction never

realized in adult life. Any quality of a thing which affects our

sense-organs does also more than that: it arouses processes in the

hemispheres which are due to the organization of that organ by past

experiences, and the result of which in consciousness are commonly

described as ideas which the sensation suggests. The first of these

ideas is that of the _thing_ to which the sensible quality belongs.

_The consciousness of particular material things present to sense_ is

nowadays called _perception_.[83] The consciousness of such things

may be more or less complete; it may be of the mere name of the thing

and its other essential attributes, or it may be of the thing's

various remoter relations. It is impossible to draw any sharp line of

distinction between the barer and the richer consciousness, because the

moment we get beyond the first crude sensation all our consciousness

is a matter of suggestion, and the various suggestions shade gradually

into each other, being one and all products of the same psychological

machinery of association. In the directer consciousness fewer, in the

remoter more, associative processes are brought into play.

_Perception thus differs from sensation by the consciousness of farther

facts associated with the object of the sensation:_

"When I lift my eyes from the paper on which I am writing I see the

chairs and tables and walls of my room, each of its proper shape and

at its proper distance. I see, from my window, trees and meadows, and

horses and oxen, and distant hills. I see each of its proper size, of

its proper form, and at its proper distance; and these particulars

appear as immediate informations of the eye, as the colors which I

see by means of it. Yet philosophy has ascertained that we derive

nothing from the eye whatever but sensations of color.... How, then,

is it that we receive accurate information, by the eye, of size and

shape and distance? By association merely. The colors upon a body

are different, according to its figure, its shape, and its size. But

the sensations of color and what we may here, for brevity, call the

sensations of extension, of figure, of distance, have been so often

united, felt in conjunction, that the sensation of the color is never

experienced without raising the ideas of the extension, the figure,

the distance, in such intimate union with it, that they not only

cannot be separated, but are actually supposed to be seen. The sight,

as it is called, of figure, or distance, appearing as it does a simple

sensation, is in reality a complex state of consciousness--a sequence

in which the antecedent, a sensation of color, and the consequent,

a number of ideas, are so closely combined by association that they

appear not one idea, but one sensation."

This passage from James Mill[84] gives a clear statement of the

doctrine which Berkeley in his Theory of Vision made for the first time

an integral part of Psychology. Berkeley compared our visual sensations

to the words of a language, which are but signs or occasions for our

intellects to pass to what the speaker means. As the sounds called

words have no inward affinity with the ideas they signify, so neither

have our visual sensations, according to Berkeley, any inward affinity

with the things of whose presence they make us aware. Those things

are _tangibles;_ their real properties, such as shape, size, mass,

consistency, position, reveal themselves only to touch. But the visible

signs and the tangible significates are by long custom so "closely

twisted, blended, and incorporated together, and the prejudice is so

confirmed and riveted in our thoughts by a long tract of time, by the

use of language, and want of reflection,"[85] that we think we _see_

the whole object, tangible and visible alike, in one simple indivisible

act.

_Sensational and reproductive brain-processes combined, then, are what

give us the content of our perceptions._ Every concrete particular

material thing is a conflux of sensible qualities, with which we have

become acquainted at various times. Some of these qualities, since

they are more constant, interesting, or practically important, we

regard as essential constituents of the thing. In a general way, such

are the tangible shape, size, mass, etc. Other properties, being more

fluctuating, we regard as more or less accidental or inessential. We

call the former qualities the reality, the latter its appearances.

Thus, I hear a sound, and say 'a horse-car'; but the sound is not the

horse-car, it is one of the horse-car's least important manifestations.

The real horse-car is a feelable, or at most a feelable and visible,

thing which in my imagination the sound calls up. So when I get, as

now, a brown eye-picture with lines not parallel, and with angles

unlike, and call it my big solid rectangular walnut library-table, that

picture is not the table. It is not even like the table as the table

is for vision, when rightly seen. It is a distorted perspective view

of three of the sides of what I mentally _perceive_ (more or less) in

its totality and undistorted shape. The back of the table, its square

corners, its size, its heaviness, are features of which I am conscious

when I look, almost as I am conscious of its name. The suggestion of

the name is of course due to mere custom. But no less is that of the

back, the size, weight, squareness, etc.

Nature, as Reid says, is frugal in her operations, and will not be at

the expense of a particular instinct to give us that knowledge which

experience and habit will soon produce. Reproduced sights and contacts

tied together with the present sensation in the unity of a _thing_ with

a name, these are the complex objective stuff out of which my actually

perceived table is made. Infants must go through a long education of

the eye and ear before they can perceive the realities which adults

perceive. _Every perception is an acquired perception._[86]

_Perception may then be defined_, in Mr. Sully's words, as that process

by which the mind

"supplements a sense-impression by an accompaniment or escort of

revived sensations, the whole aggregate of actual and revived

sensations being solidified or 'integrated' into the form of a

percept, that is, an apparently immediate apprehension or cognition of

an object now present in a particular locality or region of space."[87]

Every reader's mind will supply abundant examples of the process here

described; and to write them down would be therefore both unnecessary

and tedious. In the chapter on Space we have already discussed some of

the more interesting ones; for in our perceptions of shape and position

it is really difficult to decide how much of our sense of the object is

due to reproductions of past experience, and how much to the immediate

sensations of the eye. I shall accordingly confine myself in the rest

of this chapter to certain additional generalities connected with the

perceptive process.

* * * * *

The first point is relative to that 'solidification' or 'integration,'

whereof Mr. Sully speaks, of the present with the absent and merely

represented sensations. Cerebrally taken, these words mean no more

than this, that the process aroused in the sense-organ has shot into

various paths which habit has already organized in the hemispheres,

and that instead of our having the sort of consciousness which would

be correlated with the simple sensorial process, we have that which is

correlated with this more complex process. This, as it turns out, is

the consciousness of that more complex 'object,' the whole 'thing,'

instead of being the consciousness of that more simple object, the few

qualities or attributes which actually impress our peripheral nerves.

This consciousness must have the unity which every 'section' of our

stream of thought retains so long as its objective content does not

sensibly change. More than this we cannot say; we certainly ought not

to say what usually is said by psychologists, and treat the perception

as a sum of distinct psychic entities, the present sensation namely,

_plus_ a lot of images from the past, all 'integrated' together in a

way impossible to describe. The perception is one state of mind or

nothing--as I have already so often said.

In many cases it is easy to compare the psychic results of the

sensational with those of the perceptive process. We then see a marked

difference in the way in which the impressed portions of the object

are felt, in consequence of being cognized along with the reproduced

portion, in the higher state of mind. Their sensible quality changes

under our very eye. Take the already-quoted catch, _Pas de lieu Rhône

que nous_: one may read this over and over again without recognizing

the sounds to be identical with those of the words _paddle your own

canoe_. As we seize the English meaning the sound itself appears to

change. Verbal sounds are usually perceived with their meaning at the

moment of being heard. Sometimes, however, the associative irradiations

are inhibited for a few moments (the mind being preoccupied with other

thoughts) whilst the words linger on the ear as mere echoes of acoustic

sensation. Then, usually, their interpretation suddenly occurs. But at

that moment one may often surprise a change in the very _feel_ of the

word. Our own language would sound very different to us if we heard it

without understanding, as we hear a foreign tongue. Rises and falls of

voice, odd sibilants and other consonants, would fall on our ear in

a way of which we can now form no notion. Frenchmen say that English

sounds to them like the _gazouillement des oiseaux_--an impression

which it certainly makes on no native ear. Many of us English would

describe the sound of Russian in similar terms. All of us are conscious

of the strong inflections of voice and explosives and gutturals of

German speech in a way in which no German can be conscious of them.

This is probably the reason why, if we look at an isolated printed word

and repeat it long enough, it ends by assuming an entirely unnatural

aspect. Let the reader try this with any word on this page. He will

soon begin to wonder if it can possibly be the word he has been using

all his life with that meaning. It stares at him from the paper like

a glass eye, with no speculation in it. Its body is indeed there, but

its soul is fled. It is reduced, by this new way of attending to it,

to its sensational nudity. We never before attended to it in this

way, but habitually got it clad with its meaning the moment we caught

sight of it, and rapidly passed from it to the other words of the

phrase. We apprehended it, in short, with a cloud of associates, and

thus perceiving it, we felt it quite otherwise than as we feel it now

divested and alone.

Another well-known change is when we look at a landscape with our

head upside down. Perception is to a certain extent baffled by this

manœuvre; gradations of distance and other space-determinations are

made uncertain; the reproductive or associative processes, in short,

decline; and, simultaneously with their diminution, the colors grow

richer and more varied, and the contrasts of light and shade more

marked. The same thing occurs when we turn a painting bottom upward. We

lose much of its meaning, but, to compensate for the loss, we feel more

freshly the value of the mere tints and shadings, and become aware of

any lack of purely sensible harmony or balance which they may show.[88]

Just so, if we lie on the floor and look up at the mouth of a person

talking behind us. His lower lip here takes the habitual place of the

upper one upon our retina, and seems animated by the most extraordinary

and unnatural mobility, a mobility which now strikes us because (the

associative processes being disturbed by the unaccustomed point of

view) we get it as a naked sensation and not as part of a familiar

object perceived.

On a later page other instances will meet us. For the present these are

enough to prove our point. Once more we find ourselves driven to admit

that when qualities of an object impress our sense and we thereupon

perceive the object, the sensation as such of those qualities does not

still exist inside of the perception and form a constituent thereof.

The sensation is one thing and the perception another, and neither can

take place at the same time with the other, because their cerebral

conditions are not the same. They may _resemble_ each other, but in no

respect are they identical states of mind.

PERCEPTION IS OF DEFINITE AND PROBABLE THINGS.

The chief cerebral conditions of perception are the paths of

association irradiating from the sense-impression, which may have been

already formed. If a certain sensation be strongly associated with

the attributes of a certain thing, that thing is almost sure to be

perceived when we get the sensation. Examples of such things would be

familiar people, places, etc., which we recognize and name at a glance.

But _where the sensation is associated with more than one reality_, so

that either of two discrepant sets of residual properties may arise,

the perception is doubtful and vacillating, and _the most that can then

be said of it is that it will be of a_ PROBABLE _thing_, of the thing

which would most usually have given us that sensation.

In these ambiguous cases it is interesting to note that perception is

rarely abortive; _some_ perception takes place. The two discrepant sets

of associates do not neutralize each other or mix and make a blur. What

we more commonly get is first one object in its completeness, and then

the other in its completeness. In other words, _all brain-processes

are such as give rise to what we may call_ FIGURED _consciousness_. If

paths are irradiated at all, they are irradiated in consistent systems,

and occasion thoughts of definite objects, not mere hodge-podges of

elements. Even where the brain's functions are half thrown out of gear,

as in aphasia or dropping asleep, this law of figured consciousness

holds good. A person who suddenly gets sleepy whilst reading aloud will

read wrong; but instead of emitting a mere broth of syllables, he will

make such mistakes as to read 'supper-time' instead of 'sovereign,'

'overthrow' instead of 'opposite,' or indeed utter entirely imaginary

phrases, composed of several definite words, instead of phrases of the

book. So in aphasia: where the disease is mild the patient's mistakes

consist in using entire wrong words instead of right ones. Only in

the gravest lesions does he become quite inarticulate. These facts

show how subtle is the associative link; how delicate yet how strong

that connection among brain-paths which makes any number of them, once

excited together, thereafter tend to vibrate as a systematic whole. A

small group of elements, '_this_,' common to two systems, A and B, may

touch off A or B according as accident decides the next step (see Fig.

47). If it happen that a single point leading from '_this_' to B is

momentarily a little more pervious than any leading from '_this_' to A,

then that little advantage will upset the equilibrium in favor of the

entire system B. The currents will sweep first through that point and

thence into all the paths of B, each increment of advance making A more

and more impossible. The thoughts correlated with A and B, in such a

case, will have objects different, though similar. The similarity will,

however, consist in some very limited feature if the 'this' be small.

[Illustration: FIG. 47.]

_Thus the faintest sensations will give rise to the perception of

definite things if only they resemble those which the things are wont

to arouse._ In fact, a sensation must be strong and distinct in order

not to suggest an object and, if it is a nondescript feeling, really to

seem one. The auræ of epilepsy, globes of light, fiery vision, roarings

in the ears, the sensations which electric currents give rise to when

passed through the head, these are unfigured because they are strong.

Weaker feelings of the same sort would probably suggest objects. Many

years ago, after reading Maury's book, _Le Sommeil et les Rêves_, I

began for the first time to observe those ideas which faintly flit

through the mind at all times, words, visions, etc., disconnected with

the main stream of thought, but discernible to an attention on the

watch for them. A horse's head, a coil of rope, an anchor, are, for

example, ideas which have come to me unsolicited whilst I have been

writing these latter lines. They can often be explained by subtle

links of association, often not at all. But I have not a few times

been surprised, after noting some such idea, to find, on shutting

my eyes, an after-image left on the retina by some bright or dark

object recently looked at, and which had evidently suggested the idea.

'Evidently,' I say, because the general shape, size, and position of

object thought-of and of after-image were the same, although the idea

had details which the retinal image lacked. We shall probably never

know just what part retinal after-images play in determining the train

of our thoughts. Judging by my own experiences I should suspect it of

being not insignificant.[89]

ILLUSIONS.

Let us now, for brevity's sake, treat A and B in Fig. 47 as if they

stood for objects instead of brain-processes. And let us furthermore

suppose that A and B are, both of them, objects which might probably

excite the sensation which I have called '_this_,' but that on the

present occasion A and not B is the one which actually does so. If,

then, on this occasion '_this_' suggests A and not B, the result is a

_correct perception_. But if, on the contrary, 'this' suggests B and

not A, the result is a _false perception_, or, as it is technically

called, an _illusion_. But the _process_ is the same, whether the

perception be true or false.

Note that in every illusion what is false is what is inferred, not what

is immediately given. The 'this,' if it were felt by itself alone,

would be all right, it only becomes misleading by what it suggests.

If it is a sensation of sight, it may suggest a tactile object, for

example, which later tactile experiences prove to be not there. _The

so-called 'fallacy of the senses,' of which the ancient sceptics made

so much account, is not fallacy of the senses proper, but rather of the

intellect, which interprets wrongly what the senses give._[90]

* * * * *

So much premised, let us look a little closer at these illusions. They

are due to two main causes. _The wrong object is perceived either

because_

1) _Although not on this occasion the real cause, it is yet the

habitual, inveterate, or most probable cause of 'this;'_ or because

2) _The mind is temporarily full of the thought of that object, and

therefore 'this' is peculiarly prone to suggest it at this moment._

I will give briefly a number of examples under each head. The first

head is the more important, because it includes a number of constant

illusions to which all men are subject, and which can only be dispelled

by much experience.

_Illusions of the First Type._

[Illustration: FIG. 48.]

One of the oldest instances dates from Aristotle. Cross two fingers

and roll a pea, pen-holder, or other small object between them. It

will seem double. Professor Croom Robertson has given the clearest

analysis of this illusion. He observes that if the object be brought

into contact first with the forefinger and next with the second finger,

the two contacts seem to come in at different points of space. The

forefinger-touch seems higher, though the finger is really lower; the

second-finger-touch seems lower, though the finger is really higher.

"We perceive the contacts as double because we refer them to two

distinct parts of space." The touched sides of the two fingers are

normally not together in space, and customarily never do touch one

thing; the one thing which now touches them, therefore, seems in two

places, i.e. seems two things.[91]

There is a whole batch of illusions which come from optical sensations

interpreted by us in accordance with our usual rule, although they are

now produced by an unusual object. The _stereoscope_ is an example. The

eyes see a picture apiece, and the two pictures are a little disparate,

the one seen by the right eye being a view of the object taken from a

point slightly to the right of that from which the left eye's picture

is taken. Pictures thrown on the two eyes by solid objects present this

identical disparity. Whence we react on the sensation in our usual way,

and perceive a solid. If the pictures be exchanged we perceive a hollow

mould of the object, for a hollow mould would cast just such disparate

pictures as these. Wheatstone's instrument, the _pseudoscope_, allows

us to look at solid objects and see with each eye the other eye's

picture. We then perceive the solid object hollow, _if it be an object

which might probably be hollow,_ but not otherwise. A human face,

e.g., never appears hollow to the pseudoscope. In this irregularity

of reaction on different objects, some seem hollow, others not; the

perceptive process is true to its law, which is _always to react on the

sensation in a determinate and figured fashion if possible, and in as

probable a fashion as the case admits_. To couple faces and hollowness

violates all our habits of association. For the same reason it is very

easy to make an intaglio cast of a face, or the painted inside of a

pasteboard mask, look convex, instead of concave as they are.

Our sense of the _position_ of things with respect to our eye

consists in suggestions of how we must move our hand to touch them.

Certain places of the image on the retina, certain actively-produced

positions of the eyeballs, are normally linked with the sense of

every determinate position which an outer thing may come to occupy.

Hence we perceive the usual position, even if the optical sensation

be artificially brought from a different part of space. Prisms warp

the light-rays in this way, and throw upon the retina the image of

an object situated, say, at spot _a_ of space in the same manner in

which (without the prisms) an object situated at spot _b_ would cast

its image. Accordingly we feel for the object at _b_ instead of _a_.

If the prism be before one eye only we see the object at _b_ with that

eye, and in its right position _a_ with the other--in other words,

we see it double. If both eyes be armed with prisms with their angle

towards the right, we pass our hand to the right of all objects when we

try rapidly to touch them. And this illusory sense of their position

lasts until a new association is fixed, when on removing the prisms a

contrary illusion at first occurs. Passive or unintentional changes in

the position of the eyeballs seem to be no more kept account of by the

mind than prisms are; so we spontaneously make no allowance for them

in our perception of distance and movements. Press one of the eyeballs

into a strained position with the finger, and objects move and are

translocated accordingly, just as when prisms are used.

Curious _illusions of movement_ in objects occur whenever the eyeballs

move without our intending it. We shall learn in the following

chapter that the original visual feeling of movement is produced

by any image passing over the retina. Originally, however, this

sensation is definitely referred neither to the object nor to the

eyes. Such definite reference grows up later, and obeys certain simple

laws. We believe objects to move: 1) whenever we get the retinal

movement-feeling, but think our eyes are still; and 2) whenever we

think that our eyes move, but fail to get the retinal movement-feeling.

We believe objects to be still, on the contrary, 1) whenever we get

the retinal movement-feeling, but think our eyes are moving; and 2)

whenever we neither think our eyes are moving, nor get the retinal

movement-feeling. Thus the perception of the object's state of motion

or rest depends on the notion we frame of our own eye's movement. Now

many sorts of stimulation make our eyes move without our knowing it.

If we look at a waterfall, river, railroad train, or any body which

continuously passes in front of us in the same direction, it carries

our eyes with it. This movement can be noticed in our eyes by a

bystander. If the object keep passing towards our left, our eyes keep

following whatever moving bit of it may have caught their attention at

first, until that bit disappears from view. Then they jerk back to the

right again, and catch a new bit, which again they follow to the left,

and so on indefinitely. This gives them an oscillating demeanor, slow

involuntary rotations leftward alternating with rapid voluntary jerks

rightward. But _the oscillations continue_ for a while after the object

has come to a standstill, or the eyes are carried to a new object,

and this produces the illusion that things now move in the opposite

direction. For we are unaware of the slow leftward automatic movements

of our eyeballs, and think that the retinal movement-sensations thereby

aroused must be due to a rightward motion of the object seen; whilst

the rapid voluntary rightward movements of our eyeballs we interpret as

attempts to pursue and catch again those parts of the object which have

been slipping away to the left.

Exactly similar oscillations of the eyeballs are produced in

_giddiness_, with exactly similar results. Giddiness is easiest

produced by whirling on our heels. It is a feeling of the movement of

our own head and body through space, and is now pretty well understood

to be due to the irritation of the semi-circular canals of the inner

ear.[92] When, after whirling, we stop, we seem to be spinning in

the reverse direction for a few seconds, and then objects appear to

continue whirling in the same direction in which, a moment previous,

our body actually whirled. The reason is that our _eyes normally

tend to maintain_ their field of view. If we suddenly turn our head

leftwards it is hard to make the eyes follow. They roll in their

orbits rightwards, by a sort of compensating inertia. Even though we

_falsely think_ our head to be moving leftwards, this consequence

occurs, and our eyes move rightwards--as may be observed in any one

with vertigo after whirling. As these movements are unconscious, the

retinal movement-feelings which they occasion are naturally referred

to the objects seen. And the intermittent voluntary twitches of the

eyes towards the left, by which we ever and anon recover them from the

extreme rightward positions to which the reflex movement brings them,

simply confirm and intensify our impression of a leftward-whirling

field of view: we seem to ourselves to be periodically pursuing and

overtaking the objects in their leftward flight. The whole phenomenon

fades out after a few seconds. And it often ceases if we voluntarily

fix our eyes upon a given point.[93]

_Optical vertigo,_ as these illusions of objective movement are called,

results sometimes from brain-trouble, intoxications, paralysis, etc. A

man will awaken with a weakness of one of his eye-muscles. An intended

orbital rotation will then not produce its expected result in the way

of retinal movement-feeling--whence false perceptions, of which one of

the most interesting cases will fall to be discussed in later chapters.

* * * * *

There is an illusion of movement of the opposite sort, with which every

one is familiar at _railway stations_. Habitually, when we ourselves

move forward, our entire field of view glides backward over our retina.

When our movement is due to that of the windowed carriage, car, or

boat in which we sit, all stationary objects visible through the

window give us a sensation of gliding in the opposite direction. Hence,

whenever we get this sensation, of a window with _all_ objects visible

through it moving in one direction, we react upon it in our customary

way, and perceive a stationary field of view, over which the window,

and we ourselves inside of it, are passing by a motion of our own.

Consequently when another train comes alongside of ours in a station,

and fills the entire window, and, after standing still awhile, begins

to glide away, we judge that it is _our_ train which is moving, and

that the other train is still. If, however, we catch a glimpse of any

part of the station through the windows, or between the cars, of the

other train, the illusion of our own movement instantly disappears, and

we perceive the other train to be the one in motion. This, again, is

but making the usual and probable inference from our sensation.[94]

_Another illusion due to movement_ is explained by Helmholtz. Most

wayside objects, houses, trees, etc., look small when seen out of the

windows of a swift train. This is because we perceive them in the first

instance unduly near. And we perceive them unduly near because of their

extraordinarily rapid parallactic flight backwards. When we ourselves

move forward all objects glide backwards, as aforesaid; but the nearer

they are, the more rapid is this apparent translocation. Relative

rapidity of passage backwards is thus so familiarly associated with

nearness that when we feel it we perceive nearness. But with a given

size of retinal image the nearer an object is, the smaller do we judge

its actual size to be. Hence in the train, the faster we go, the nearer

do the trees and houses seem, and the nearer they seem, the smaller do

they look.[95]

* * * * *

_Other illusions are due to the feeling of convergence_ being

wrongly interpreted. When we converge our eyeballs we perceive an

_approximation_ of whatever thing we may be looking at. Whatever things

do approach whilst we look at them oblige us, so long as they are not

very distant, to converge our eyes. Hence approach of the thing is

the _probable_ objective fact when we feel our eyes converging. Now

in most persons the internal recti muscles, to which convergence is

due, are weaker than the others; and the entirely passive position of

the eyeballs, the position which they assume when covered and looking

at nothing in particular, is either that of parallelism or of slight

divergence. Make a person look with both eyes at some near object, and

then screen the object from _one_ of his eyes by a card or book. The

chances are that you will see the eye thus screened turn just a little

outwards. Remove the screen, and you will now see it turn in as it

catches sight of the object again. The other eye meanwhile keeps as it

was at first. To most persons, accordingly, all objects seem to _come

nearer_ when, after looking at them with one eye, both eyes are used;

and they seem to _recede_ during the opposite change. With persons

whose external recti muscles are insufficient, the illusions may be of

the contrary kind.

* * * * *

_The size of the retinal image_ is a fruitful source of illusions.

Normally, the retinal image grows larger as the object draws near. But

the sensation yielded by this enlargement is also given by any object

which really grows in size without changing its distance. Enlargement

of retinal image is therefore an ambiguous sign. An opera-glass

enlarges the moon. But most persons will tell you that she looks

smaller through it, only a great deal nearer and brighter. They read

the enlargement as a sign of approach; and the perception of approach

makes them actually reverse the sensation which suggests it--by an

exaggeration of our habitual custom of making allowance of the apparent

enlargement of whatever object approaches us, and reducing it in

imagination to its natural size. Similarly, in the theatre the glass

brings the stage near, but hardly seems to magnify the people on it.

The well-known increased _apparent size of the moon on the horizon_ is

a result of association and probability. It is seen through vaporous

air, and looks dimmer and duskier than when it rides on high; and it is

seen over fields, trees, hedges, streams, and the like, which break

up the intervening space and make us the better realize the latter's

extent. Both these causes make the moon seem more distant from us when

it is low; and as its visual angle grows no less, we deem that it must

be a larger body, and we so perceive it. It looks particularly enormous

when it comes up directly behind some well-known large object, as a

house or tree, distant enough to subtend an angle no larger than that

of the moon itself.[96]

* * * * *

_The feeling of accommodation_ also gives rise to false perceptions of

size. Usually we accommodate our eyes for an object as it approaches

us. Usually under these circumstances the object throws a larger

retinal image. But believing the object to remain the same, we

make allowance for this and treat the entire eye-feeling which we

receive as significant of nothing but _approach_. When we relax our

accommodation and at the same time the retinal image grows smaller,

the probable cause is always a _receding_ object. The moment we put on

convex glasses, however, the accommodation relaxes, but the retinal

image grows larger instead of less. This is what would happen if our

object, whilst receding, grew. Such a probable object we accordingly

perceive, though with a certain vacillation as to the recession, for

the growth in apparent size is also a probable sign of approach,

and is at moments interpreted accordingly.--Atropin paralyzes the

muscles of accommodation. It is possible to get a dose which will

weaken these muscles without laming them altogether. When a known near

object is then looked at we have to make the same voluntary strain to

accommodate, as if it were a great deal nearer; but as its retinal

image is not enlarged in proportion to this suggested approach, we deem

that it must have grown smaller than usual. In consequence of this

so-called _micropsy_, Aubert relates that he saw a man apparently no

larger than a photograph. But the small size again made the man seem

farther off. The real distance was two or three feet, and he seemed

against the wall of the room.[97] Of these vacillations we shall have

to speak again in the ensuing chapter.[98]

* * * * *

[Illustration: FIG. 49.]

Mrs. C. L. Franklin has recently described and explained with rare

acuteness an illusion of which the most curious thing is that it was

never noticed before. Take a single pair of crossed lines (Fig. 49),

hold them in a horizontal plane before the eyes, and look along them,

at such a distance that with the right eye shut, 1, and with the

left eye shut, 2, looks like the projection of a vertical line. Look

steadily now at the point of intersection of the lines with both eyes

open, and you will see a third line sticking up like a pin through

the paper at right angles to the plane of the two first lines. The

explanation of this illusion is very simple, but so circumstantial that

I must refer for it to Mrs. Franklin's own account.[99] Suffice it

that images of the two lines fall on 'corresponding' rows of retinal

points, and that the illusory vertical line is the only object capable

of throwing such images. A variation of the experiment is this:

"In Fig. 50 the lines are all drawn so as to pass through a common

point. With a little trouble one eye can be put into the position of

this point--it is only necessary that the paper be held so that, with

one eye shut, the other eye sees all the lines leaning neither to

the right nor to the left. After a moment one can fancy the lines to

be vertical staffs standing out of the plane of the paper.'... This

illusion [says Mrs. Franklin] I take to be of purely mental origin.

When a line lies anywhere in a plane passing through the apparent

vertical meridian of one eye, and is looked at with that eye only...

we have no very good means of knowing how it is directed in that

plane.... Now of the lines in nature which lie anywhere within such

a plane, by far the greater number are vertical lines. Hence we are

peculiarly inclined to think that a line which we perceive to be in

such a plane is a vertical line. But to see a whole lot of lines at

once, all ready to throw their images upon the vertical meridian, is a

thing that has hardly ever happened to us, except when they all have

been vertical lines. Hence when that happens we have a still stronger

tendency to think that what we see before us is a group of vertical

lines."

[Illustration: FIG. 50.]

In other words, we see, as always, the most probable object.

* * * * *

The foregoing may serve as examples of the first type of illusions

mentioned on page 86. I could cite of course many others, but it

would be tedious to enumerate all the thaumatropes and zoetropes,

dioramas, and juggler's tricks in which they are embodied. In the

chapter on Sensation we saw that many illusions commonly ranged

under this type are, physiologically considered, of another sort

altogether, and that associative processes, strictly so called, have

nothing to do with their production.

_Illusions of the Second Type._

We may now turn to illusions of the second of the two types

discriminated on page 86. In this type we perceive a wrong object

because our mind is full of the thought of it at the time, and any

sensation which is in the least degree connected with it touches off,

as it were, a train already laid, and gives us a sense that the object

is really before us. Here is a familiar example:

"If a sportsman, while shooting woodcock in cover, sees a bird about

the size and color of a woodcock get up and fly through the foliage,

not having time to see more than that it is a bird of such a size

and color, he immediately supplies by inference the other qualities

of a woodcock, and is afterwards disgusted to find that he has shot

a thrush. I have done so myself, and could hardly believe that

the thrush was the bird I had fired at, so complete was my mental

supplement to my visual perception."[100]

As with game, so with enemies, ghosts, and the like. Anyone waiting

in a dark place and expecting or fearing strongly a certain object

will interpret any abrupt sensation to mean that object's presence.

The boy playing 'I spy,' the criminal skulking from his pursuers, the

superstitious person hurrying through the woods or past the churchyard

at midnight, the man lost in the woods, the girl who tremulously

has made an evening appointment with her swain, all are subject to

illusions of sight and sound which make their hearts beat till they are

dispelled. Twenty times a day the lover, perambulating the streets with

his preoccupied fancy, will think he perceives his idol's bonnet before

him.

_The Proof-reader's Illusion_. I remember one night in Boston, whilst

waiting for a 'Mount Auburn' car to bring me to Cambridge, reading

most distinctly that name upon the signboard of a car on which (as I

afterwards learned) 'North Avenue' was painted. The illusion was so

vivid that I could hardly believe my eyes had deceived me. All reading

is more or less performed in this way.

"Practised novel- or newspaper-readers could not possibly get on so

fast if they had to see accurately every single letter of every word

in order to perceive the words. More than half of the words come out

of their mind, and hardly half from the printed page. Were this not

so, did we perceive each letter by itself, typographic errors in

well-known words would never be overlooked. Children, whose ideas

are not yet ready enough to perceive words at a glance, read them

wrong if they are printed wrong, that is, right according to the

way of printing. In a foreign language, although it may be printed

with the same letters, we read by so much the more slowly as we do

not understand, or are unable promptly to perceive the words. But

we notice misprints all the more readily. For this reason Latin and

Greek and, still better, Hebrew works are more correctly printed,

because the proofs are better corrected, than in German works. Of two

friends of mine, one knew much Hebrew, the other little; the latter,

however, gave instruction in Hebrew in a gymnasium; and when he

called the other to help correct his pupils' exercises, it turned out

that he could find out all sorts of little errors better than his

friend, because the latter's perception of the words as totals was too

swift."[101]