The Principles of Psychology, Vols. 1-2

The Proof-reader's Illusiof. 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 evei*y 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." * Testimony to personal identity is proverbially fallacious for similar reasons. A man has witnessed a rapid crime or accident, and carries away his mental image. Later he is confronted by a prisoner whom he forthwith perceives in the light of that image, and recognizes or ' identifies ' as a participant, although he may never have been near the spot. Similarly at the so-called * materializing seances' which fraudulent mediums give : in a dark room a man sees a gauze-robed figure who in a whisper tells him she is the spirit of his sister, mother, wife, or child, and falls upon his neck. The darkness, the previous forms, and the expectancy have so filled his mind with piemonitory images that it is no wonder he perceives what is suggested. These fraudulent ' seances ' would furnish most precious documents to the psychology of perception, if they could only be satisfactorily inquired into. In the hypnotic trance any suggested object is sensibly perceived. In certain subjects this happens more or less completely after waking from the trance. It would seem that under favorable conditions a somewhat similar susceptibility to suggestion may exist in certain persons who are not otherwise entranced at all.

This suggestibility is greater in the lower senses than in the higher. A German observer writes : " We know that a weak smell or taste may be very diversely interpreted by us, and that the same sensation will now be named as one thing and the next moment as another. Suppose an agreeable smell of flowers in a room : A visitor will notice it, seek to recognize what it is, *M. Lazarus: Das Leben d. Seele, ii (1857), p. 32. In the ordinary hearing of speech half the words we seem to hear are supplied out of our own head. A language with which we are perfectly familiar is understood, even when spoken in low tones and far off. An unfamiliar language is unintelligible under these conditions. If we do not get a very good seat at a foreign theatre, we fail to follow the dialogue ; and what gives trouble to most of us when abroad is not only that the natives speak so fast, but that they speak so indistinctly and so low. The verbal objects for interpreting the sounds by are not alert and ready made in our minds, as they are in our familiar mother-tongue, and do not start up at so faint a cue.

and at last perceive more and more distinctly that it is the perfume of roses — until after all he discovers a bouquet of violets. Then suddenly he recognizes the violet-smell, and wonders how he could possibly have hit upon the roses.— Just so it is with taste. Try some meat whose visible characteristics are disguised by the mode of cooking, and you will perhaps begin by taking it for venison, and end by being quite certain that it is venison, until you are told that it is mutton ; whereupon you get distinctly the mutton flavor. — In this wise one may make a person taste or smell what one will, if one only makes sure that he shall conceive it beforehand as we wish, by saying to him : ' Doesn't that taste just like, etc.?' or 'Doesn't it smell just like, etc.?' One can cheat whole companies in this way ; announce, for instance, at a meal, that the meat tastes 'high,' and almost every one who is not animated by a spirit of opposition will discover a flavor of putrescence which in reality is not there at all.

" In the sense ot feeling this phenomenon is less prominent, because we get so close to the object that our sensation of it is never incomplete. Still, examples may be adduced from this sense. On superficially feeling of a cloth, one may confidently declare it for velvet, whilst it is perhaps a long-haired cloth ; or a person may perhaps not be able to decide whether he has put on woolen or cotton stockings, and, trying to ascertain this by the feeling on the skin of the feet, he may become aware that he gets the feeling of cotton or wool according as he thinks of the one or the other. When the feeling in our fingers is somewhat blunted by cold, we notice many such phenomena, being then more exposed to confound objects of touch with one another." *

High authorities have doubted this power of imagination to falsify present impressions of sense. t Yet it unquestionably exists. Within the past fortnight I have been annoyed by a smell, faint but unpleasant, in my library. My annoyance began by an escape of gas from the furnace below stairs. This seemed to get lodged in my imagination as a sort of standard of perception; for, several days after the furnace had been rectified, I perceived the *same smell' again. It was traced this time to a new pair of India rubber shoes which had been brought in from the shop and laid on a table. It persisted in coming to me for several days, however, in spite of the fact that no other member of the family or visitor noticed anything unpleasant. My impression during part of this time was one of uncertainty whether

* G. H. Meyer, Untersuchungen, etc., pp. 242-3. t Helmholtz, P. O. 438. The question will soon come before us again in the chapter on the Perception of Space. the smell was imaginary or real ; and at last it faded out. Everyone must be able to give instances like this from the smell-sense. When we have paid the faithless plumber for pretending to mend our drains, the intellect inhibits the nose from perceiving the same unaltered odor, until perhaps several days go by. As regards the ventilation or heating of rooms, we are apt to feel for some time as we think we ought to feel. If we believe the ventilator is shut, we feel the room close. On discovering it open, the oppression disappears.

"A patient called at my oflBce one day in a state of great excitement from the effects of an offensive odor in the horse-car she had come in, and which she declared had probably emanated from some very sick person who must have been just carried in it. There could be no doubt that something had affected her seriously, for she was very pale, with nausea, diflBculty in breathing, and other evidences of bodily and mental distress. I succeeded, after some diflBculty and time, in quieting her, and she left, protesting that the smell was unlike anything she had ever before experienced and was something dreadful. Leaving my oflBce soon after, it so happened that I found her at the street-corner, waiting for a car: we thus entered the car together. She immediately called my attention to the same sickening odor which she had experienced in the other car, and began to be affected the same as before, when I pointed out to her that the smell was simply that which always emanates from the straw which has been in stables. She quickly recognized it as the same, when the unpleasant effects which arose while she was possessed with another perception of its character at once passed away." *

It is the same with touch. Everyone must have felt the sensible quality change under his hand, as sudden contact with something moist or hairy, in the dark, awoke a shock of disgust or fear which faded into calm recognition of some familiar object? Even so small a thing as a crumb of potato on the table-cloth, which we pick up, thinking it a crumb of bread, feels horrible for a few moments to our fancy, and different from what it is. Weight or muscular feeling is a sensation ; yet who has not heard the anecdote of some one to whom Sir Humphry Davy showed the metal sodium which he had just discovered? "Bless me, how heavy it is!" said the man;

showing that his idea of what metals as a class ought to be had falsified the sensation he derived from a very light substance. In the sense of hearing, similar mistakes abound. I have already mentioned the hallucinatory effect of mental images of very faint sounds, such as distant clock-strokes (above, p. IV). But even when stronger sensations of sound have been present, everyone must recall some experience in which they have altered their acoustic character as soon as the intellect referred them to a different source. The other day a friend was sitting in my room, when the clock, which has a rich low chime, began to strike. " Hollo ! " said he, "hear that hand-organ in the garden," and was surprised at finding the real source of the sound. I had myself some years ago a very striking illusion of the sort. Sitting reading late one night, I suddenly heard a most formidable noise proceeding from the upper part of the house, which it seemed to fill. It ceased, and in a moment renewed itself. I went into the hall to listen, but it came no more. Resuming my seat in the room, however, there it was again, low, mighty, alarming, like a rising flood or the avantcourier of an awful gale. It came from all space. Quite startled, I again went into the hall, but it had already ceased once more. On returning a second time to the room, I discovered that it was nothing but the breathing of a little Scotch terrier which lay asleep on the floor. The noteworthy thing is that as soon as I recognized what it was, I was compelled to think it a different sound, and could not then hear it as I had heard it a moment before.

In the anecdotes given by Delbceuf and Reid, this was probably also the case, though it is not so stated. Eeid says: " I remember that once lying abed, and having been put into a fright, I heard my own heart beat; but I took it to be one knocking at the door, and arose and opened the door oftener than once, before I discovered that the sound was in my own breast." (Inquiry, chap. iv. " The illustrious P. J. van Beneden, senior, was walking one evening with a friend along a woody hill near Chaudfontaine. ' Don't you

hear,' said the friend, ' the noise of a hunt on the mountain?' M. van Beneden listens and distinguishes in fact the giving-tongue of the dogs. They listen some time, expecting from one moment to another to see a deer bound by; but the voice of the dogs seems neither to recede nor approach. At last a countryman comes by, and they ask him who it is that can be hunting at this late hour. But he, pointing to some puddles of water near their feet, replies: ' Yonder little animals are what you hear.' And there there were in fact a number of toads of the species Bombinator igneus. . . . This batrachian emits at the pairing season a silvery or rather crystalline note. . . . Sad and pure, it is a voice in nowise resembling that of hounds giving chase." *

The sense of siglit, as we have seen in studying Space, is pregnant vrith illusions of both the types considered. No sense gives such fluctuating impressions of the same object as sight does. With no sense are we so apt to treat the sensations immediately given as mere signs ; with none is the invocation from memory of a thing, and the consequent perception of the latter, so immediate. The * thing ' which we perceive always resembles, as we have seen, the object of some absent sensation, usually another optical figure which in our mind has come to be the standard of reality; and it is this incessant reduction of our optical objects to more * real ' forms which has led some authors into the mistake of thinking that the sensations which first apprehend them are originally and natively of no from at alLf

Of accidental and occasional illusions of sight many amusing examples might be given. Two will suffice. One is a reminiscence of my own. I was lying in my berth in a steamer listening to the sailors holystone the deck outside ; when, on turning my eyes to the window, I perceived with perfect distinctness that the chief-engineer of the vessel had entered my state-room, and was standing looking through the window at the men at work upon the guards. Surprised at his intrusion, and also at his intentness and

f Compare A. W Volkmann's essay * Ueber Ursprtlngliches und Erworbenes in den Raumanschauiingen,' on p. 139 of his Untersuchungen im Gebiete der Optik ; and Chapter xiii of Hering's contribution to Her- l's Handbuch der Physiologie, vol. iii. immobility, I remained watching him and wondering how long he would stand thus. At last I spoke ; but getting no reply, sat up in my berth, and then saw that what I had taken for the engineer was my own cap and coat hanging on a peg beside the window. The illusion was complete ; the engineer was a peculiar-looking man ; and I saw him unmistakably ; but after the illusion had vanished 1 found it hard voluntarily to make the cap and coat look like him at all.

The following story, which I owe to my friend Prof. Hyatt, is of a probably not uncommon class : ** During the winter of 1858, while in Venice, I had the somewhat peculiar illusion which you request me to relate. I remember the circumstances very accurately because I have often repeated the story, and have made an effort to keep all the attendant circumstances clear of exaggeration. I was travelling with my mother, and we had taken rooms at a hotel which had been located in an old palace. The room in which I went to bed was large and lofty. The moon was shining brightly, and I remember standing before a draped window, thinking of the romantic nature of the surroundings, remnants of old stories of knights and ladies, and the possibility that even in that room itself love-scenes and sanguinary tragedies might have taken place. The night was so lovely that many of the people were strolling through the narrow lanes or so-called streets, singing as they went, and I laid aw^ake for some time listening to these patrols of serenaders, and of course finally fell asleep. I became aware that some one was leaning over me closely, and that my own breathing was being interfered with; a decided feeling of an unwelcome presence of some sort awakened me. As I opened my eyes I saw, as distinctly as I ever saw any living person, a draped head about a foot or eighteen inches to the right, and just above my bed. The horror which took possession of my young fancy was beyond anything I have ever experienced. The head was covered by a long black veil which floated out into the moonlight, the face itself was pale and beautiful, and the lower part swathed in the white band commonly worn by the nuns of Catholic orders. My hair seemed to rise up, and a profuse perspiration attested the genuineness of the terror which I felt. For a time I lay in this way, and then gradually gaining more command over my superstitious terrors, concluded to try to grapple with the apparition.

It remained perfectly distinct until I reached at it sharply with my hand, and then disappeared, to return again, however, as soon as I sank back into the pillow. The second or third grasp which I made at the head was not followed by a reappearance, and I then saw that the ghost was not a real presence, but depended upon the position of my head. If I moved my eyes either to the left or right of the original position occupied by my head when I awakened, the ghost disappeared, and by returning to about the same position, I could make it reappear with nearly the same intensity as at first. I presently satisfied myself by these experiments that the illusion arose from the effect of the imagination, aided by the actual figure made by a visual section of the moonbeams shining through the lace curtains of the window. If I had given way to the first terror of the situation and covered up my head, I should probably have believed in the reality of the apparition, since I have not by the slightest word, so far as I know, exaggerated the vividness of my feelings."

Einough has now been said to prove the general law of perception, which is this, that whilst part of what we perceive comes through our senses from the object before us, another 'part (and it may be the larger part) always comes (in Lazarus's phrase) out of our own head. At bottom this is only one case (and that the simplest case) of the general fact that our nerve-centres are an organ for reacting on sense-impressions, and that our hemispheres, in particular, are given us in order that records of our private past experience may co-operate in the reaction. Of course such a general way of stating the fact is vague ; and all those who follow the current theory of ideas will be prompt to throw this vagueness at it as a reproach. Their way of describing the process goes much more into detail. The sensation, they say, awakens ^ images ' of other sensations associated with it in the past. These images ' fuse,' or are * combined ' by the Ego with the present sensation into a new product, the percept, etc., etc. Something so indistinguishable from this in practical outcome is what really occurs, that one may seem fastidious in objecting to such a statement, specially if have no rival theory of the elementary processes to propose. And yet, if this notion of images rising and flocking and fusing be mythological (and we have all along so considered it), why should we entertain it unless confessedly as a mere figure of speech ? As such, of course, it is convenient and welcome to pass. But if we try to put an exact meaning into it, all we find is that the brain reacts by paths which previous experiences have worn, and makes us usually perceive the probable things i.e., the thing by

which on previous occasions the reaction was most frequently aroused. But we can, I think, without danger of being too speculative, be a little more exact than this, and conceive of a physiological reason why the felt quality of an object changes when, instead of being apprehended in a mere sensation, the object is perceived as a thing. All consciousness seems to depend on a certain slowness of the process in the cortical cells. The rapider currents are, the less feeling they seem to awaken. If a region A, then, be so connected with another region B that every current which enters A immediately drains off into B, we shall not be very strongly conscious of the sort of object that A can make us feel. If B, on the contrary, has no such copious channel of discharge, the excitement will linger there longer ere it diffuses itself elsewhere, and our consciousness of the sort of object that B makes us feel will be strong. Carrying this to an ideal maximum, we may say that if A offer no resistance to the transmission forward of the current, and if the current terminate in B, then, no matter what causes may initiate the current, we shall get no consciousness of the object peculiar to A, but on the contrary a vivid sensation of the object peculiar to B. And this will be true though at other times the connection between A and B might lie less open, and every current then entering A might give us a strong consciousness of A's peculiar object. In other words, just in proportion as associations are habitual, will the qualities of the suggested thing tend to substitute themselves in consciousness for those of the thing immediately there; or, more briefly, just in proportion as an experience is probable vnll it tend to he directly felt. In all such experiences the paths lie wide open from the cells first affected to those concerned with the suggested ideas.

A circular after-image on the receding wall or ceiling is actually seen as an ellipse, a square after-image of a cross there is seen as slant-legged, etc., because only in the process correlated with the vision of the latter figures do the inward currents find a pause (see the next chapter). We must remember this when, in dealing with the eye, we come to point out the erroneousness of the principle laid down by Eeid and Helmholtz that true sensationfe can never be changed by the suggestions of experience.

A certain illusion of which I have not yet spoken affords an additional illustration of this. When we vM to execute a movement and the movement for some reason does not occur, unless the sensation of the part's not moving is a strong one, we are apt to feel a^ if the movement had actually taken place. This seems habitually to be the case in anaesthesia of the moving parts. Close the patient's eyes, hold his anaesthetic arm still, and tell him to raise his hand to his head ; and when he opens his eyes he will be astonished to find that the movement has not taken place. All reports of anaesthetic cases seem to mention this illusion. Sternberg who wrote on the subject in 1885,^ lays it down as a law that the intention to move is the same thing as the feeling of the motion. We shall later see that this is false (Chapter XXV) ; but it certainly may suggest the feeling of the motion with hallucinatory intensity. Sternberg gives the following experiment, which I find succeeds with at least half of those who try it : Best your palm on the edge of the table with your forefinger hanging over in a position of extreme flexion, and then exert your will to flex it still more. The position of the other fingers makes this impossible, and yet if we do not look to see the finger, we think we feel it move. Ho quotes from Exner a similar experiment with the jaws: Puu some hard rubber or other unindentable obstacle between

* In the Proceedings of the American Society for Psychical Research, pp. 253-4. I have tried to account for some of the variations in this conscio'jfness. Out of 140 persons whom I fo'md to feel their lost foot, some did so dubiously. "Either they only feel it occasionally, or only when it pains them, or only when they try to move it; or they only feel it when they 'think a good deal about it ' and make an effort to conjure it up. When they 'grow inattentive,' the feeling 'flies back' or 'jumps back,' to the stump. Every degree of consciousness, from complete and permanent hallucination down to something hardly distinguishable from ordinary fancy, seems represented in the sense of the missing extremity which these patients say they have. Indeed I have seldom seen a more plausible lot of evidence for the view that imagination and sensation are but differences of vividness in an identical process than these confessions, taking them altogether, contain. Many patients say they can hardly tell whether thej^ feel or fancy the limb. "

your back teeth and bite hard : you think you feel the jaiv move and the front teeth approach each other, though in the nature of things no movement can occur.* — The visual suggestion of the path traversed by the finger-tip as the locus of the movement-feeling in the joint, which we discussed on page 41, is another example of this semi-hallucinatory power of the suggested thing. Amputated people, as we have learned, still feel their lost feet, etc. This is a necessary consequence of the law of specific energies, for if the central region correlated with the foot give rise to any feeling at all it must give rise to the feeling of a foot, f But the curious thing is that many of these patients can will the foot to move^ and when they have done so, distinctly /ee? the movement to occur. They can, to use their own language, * work ' or ' wiggle ' their lost toes. %

Now in all these various cases we are dealing with data which in normal life are inseparably joined. Of all possible experiences, it is hard to imagine any pair more uniformly and incessantly coupled than the volition to move, on the one hand, and the feeling of the changed position of the parts, on the other. From the earliest ancestors of ours which had feet, down to the present day, the movement of the feet must always have accompanied the will to move them ; and here, if anywhere, habit's consequences ought to be found.! The process of the willing ought, then, to pour into the process of feeling the command effected, and ought to awaken that feeling in a maximal degree provided no other positively contradictory sensation come in at the same time. In most of us, when the will fails of its efi'ect there is a contradictory sensation. We discern a resistance or the unchanged position of the limb. But neither in anaesthesia nor in amputation can there be any contradictory sensation in the foot to correct us ; so imagination has all the force of fact.

* Pflliger's Arcbiv, xxxvii. 1. f Not all patients have this additional illusion. X I ought to say that in almost all cases the volition is followed b^ actual contraction of muscles in the utump. In Germany since Herbart's time Psychology hasalwayi had a great deal to say about a process called Apperception.* The incoming ideas or sensations are said to be * apperceived ' by * masses ' of ideas already in the mind. It is plain that the process we have been describing as perception isj at this rate, an apperceptive process. So are all recognition, classing, and naming ; and passing beyond these simplest suggestions, all farther thoughts about our percepts are apperceptive processes as well. I have myself not used the word apperception because it has carried very different meanings in the history of philosophy,! and * psychic reaction,* * interpretation,' * conception,' * assimilation,' * elaboration,' or simply * thought,' are perfect synonyms for its Herbartian meaning, widely taken. It is, moreover, hardly worth while to pretend to analyze the so-called apperceptive performances beyond the first or perceptive stage, because their variations and degrees are literally innumerable. * Apperception ' is a name for the sum-total of the effects of what we have studied as association; and it is obvious that the things which a given experience will suggest to a man depend on what Mr. Lewes calls his entire psychostatical conditions, his nature and stock of ideas, or, in other words, his character, habits, memory, education, previous experience, and momentary mood. We gain no insight into what really occurs either in the mind or in the brain by calling all these things the * apperceiving mass,' though of course this may upon occasion be convenient. On the whole I am inclined to think Mr. Lewes's term of * assimilation ' the most fruitful one yet used.if

Professor H. Steinthal has analyzed apperceptive processes with a sort of detail which is simply burdensome. § t Compare the historical reviews by K. Lange : Ueber Apperception (Plauen, 1879), pp. 12-14; by Staude in Wundt's Philosophische Studien, i. 149; and by Marty in Vierteljsch. f. wiss. Phil., x. 347 ff. § See his Einleitung in die Psychologie u. Sprachwissenschaft (1881 X p. 166 n. His introduction of the matter may, however, be quoted He begins with an anecdote from a comic paper.

'* In the compartment of a railway-carriage six persons unknown to each other sit in lively conversation. It becomes a matter of regret that one of the company must alight at the next station. One of the others says that he of all things prefers such a meeting with entirely unknown persons, and that on such occasions he is accustomed neither to ask who or what his companions may be nor to tell who or what he is. Another Ghereupon says that he will undertake to decide this question, if they each and all will answer him an entirely disconnected question. They began. He drew five leaves from his note-book, wrote a question on each, and gave one to each of his companions with the request that he write the answer below. When the leaves were returned to him, he turned, after reading them, without hesitation to the others, and said to the first, * You are a man of science'; to the second, ' You are a sol dier'; to the third, 'You are a philologer'; to the fourth, ' You are a journalist'; to the fifth, 'You are a farmer.' All admitted that he was right, whereupon he got out aod left the five behind. Each wished to know what question the others had received; and behold, he had given the same question to each. It ran thus :

"To this the naturalist had answered, 'vital force'; the soldier, war'; the philologist, 'Kronos'; the publicist, 'revolution'; the farmer, 'a boar'. This anecdote, methinks, if not true, is at least splendidly well invented. Its narrator makes the journalist go on to say : ' Therein consists the joke. Each one answers the first thing that occurs to him,* and that is whatever is most newly related to his pursuit in life. Every question is a hole-drilling experiment, and the answer is an opening through which one sees into our interiors.' ... So do we all. We are all able to recognize the clergyman, the soldier, the scholar, the business man, not only by the cut of their garments and the attitude of their body, but by what they say and how they express it. We guess the place in life of men by the interest which they show and the way in which they show it, by the objects of which they speak, by the point of view from which they regard things, judge them, conceive them, in short by their mode of apperceiving , . . .

"Every man has one group of ideas which relate to his own person and interests, and another which is connected with society. Each ha^:, his group of ideas about plants, religion, law, art, etc., and more especially about the rose, epic poetry, sermons free trade, and the like Thus the mental content of every individual, even of the uneducated * One of my colleagues, asking himself the question after reading the fcnecdote, tells me that he replied * Harvard College/ the faculty of that body having voted, a few days previously, to keep back the degrees of membeio ^ the ffraduatine clais who might be disorderly on class-day night. W. J

and of children, consists of masses or circles of knowledge of whlck each lies within some larger circle, alongside of others similarly included, and of which each includes smaller circles within itself. . . . The perception of a thing like a horse ... is a process between the present horse's picture before our eyes, on the one hand, and those fused or interwoven pictures and ideas of all the horses we have ever seen, on the other; ... a process between two factors or momenta, of which one existed before the process and was an old possession of the mind (the group of ideas, or concept, namely), whilst the other is but just presented to the mind, and is the immediately supervening factor (the sense-impression). The former apperceives the latter; the latter is apperceived by the former. Out of their combination an apperceptionproduct arises: the knowledge of the perceived being as a horse. The earlier factor is relatively to the later one active and a priori ; the supervening factor is given, a posteriori^ passive. . . . We may then define Apperception as the movement of two masses of consciousness (Vorstellungsmassen) against each other so as to produce a cognition.