The Principles of Psychology, Vols. 1-2

To illustrate, how does one learn to distinguish claret from burgundy? Probably they have been drunk on different occasions. When we first drank claret we heard it called by that name, we were eating such and such a dinner, etc. Next time we drink it, a dim reminder of all those things chimes through us as we get the taste of the wine. When we try burgundy our first impression is that it is a kind of claret ; but something falls short of full iden tification, and presently we hear it called burgundy. Dur ing the next few experiences, the discrimination may stil] be uncertain — " which," we ask ourselves, " of the two wines is this present specimen ?" But at last the claret-flavor re calls pretty distinctly its own name, ' claret,' " that wine I drank at So-and-so's table," etc. ; and the burgundy -flavor recalls the name burgundy and some one else's table. And only when this different SETTING has come to each is our dis crimination betiveen the two flavors solid and stable. After a while the tables and other parts of the setting, besides the name, grow so multifarious as not to come up distinctly into consciousness ; but pari passu with this, the adhesion of each wine with its own name becomes more and more in veterate, and at last each flavor suggests instantly and cer tainly its own name and nothing else. The names differ far more than the flavors, and help to stretch these latter farther apart. Some such process as this must go on in all our experience. Beef and mutton, strawberries and rasp berries, odor of rose and odor of violet, contract different adhesions which reinforce the differences already felt in the terms.

The reader may say that this has nothing to do with making us feel the difference between the two uerms. It is merely fixing, identifying, and so to speak substantializing, the terms. But what we feel as their difference, we should feel, even though we were unable to name or otherwise identify the terms. To which I reply that I believe that the difference is always concreted and made to seem more substantial by rec ognizing the terms. I went out for instance the other day and found that the snow just fallen had a very odd look, different from the common appearance of snow. I presently called it a ' micaceous ' look ; and it seemed to me as if, the moment I did so, the difference grew more distinct and fixed than it was before. The other connotations of the word 'micaceous' dragged the snow farther away from ordinary snow and seemed even to aggravate the peculiar look in question. I think some such effect as this on our way of feeling a difference will be very generally admitted to follow from naming the terms between Avhich it obtains ; although I admit myself that it is difficult to show coercively that naming or otherwise identifying any given pair of hardly distinguishable terms is essential to their being felt as different at first*

* The explanation I offer presupposes that a difference too faint to have any direct effect in the way of makiug the miud notice it per se will never theless be strong enough to keep its ' terms ' from calling up identical associates. It seems probable from many observations that this is the case. All the facts of ' unconscious ' inference are proofs of it. We say a painting ' looks ' like the work of a certain artist, though we cannot name the characteristic differentiae. We see by a man's face that he is sincere, though we can give no definite reason for our faith. The facts of senseperception quoted from Helmholtz a few pages below will be additional examples. Here is another good one, though it will perhaps be easier understood after reading the chapter on Space-perception than now. Take two stereoscopic slides and represent on each half-slide a pair of spots, a and b, but make their distances such that the a's are equidistant on both slides, whilst the b's are nearer together on slide 1 than on slide 2. Make moreover the distance ab = db'" and the distance ab' = ab" Then

look successively at the two slides stereoscopically. so that the a's in both are directly fixated (that fc fall on the two foveae, or centres of distinct- I offer the explanation only as a partial one : it certainly is not complete. Take the way in which practice refines our local discrimination on the skin, for example. Two compass-points touching the palm of the hand must be kept, say, half an inch asunder in order not to be mistaken for one point. But at the end of an hour or so of practice with them we can distinguish them as two, even when less than a quarter of an inch apart. If the same two regions of the skin were constantly touched, in this experience, the explanation we have been considering would perfectly apply. Suppose a line abed e/of points upon the skin. Suppose the local difference of feeling between a and f to be so strong as to be instantly recognized when the points are simultaneously touched, but suppose that between c and d to be at first too small for this purpose. If we began by putting the compasses on a and f and gradually contracted their opening, the strong doubleness recognized at first would still be suggested, as the compass-points approached the positions c and d ; for the point e would be so near/, and so like it, as not to be aroused without/also coming to mind. Similarly d would recall e and, more remotely,/. In such wise c — d would no longer be bare c — d, but something more like abc — def, — palpably differing impressions. But in ac tual experience the education can take place in a much less methodical way, and we learn at last to discriminate c and d without any constant adhesion being contracted between

est vision). The «'s will then appear single, and so probably will the b's. But the now single-seeming & on slide 1 will look nearer, whilst that on slide 2 will look farther than the a. But, if the diagrams are rightly drawn, ft and V" imv4 affect 'identical' spots, spots equally far to the right of the fovea, ft in the left eye and ft'" in the right eye. The same is true of ft' and ft". Identical spots are spots whose sensations cannot possibly be discriminated as such. Since in these two observations, however, they give rise to such opposite perceptions of distance, and prompt such op posite tendencies to movement (since in slide 1 we converge in looking from a to ft, whilst in slide 2 we diverge], it follows that two processes which occasion feelings quite indistinguishable to direct consciousness may never theless be each allied with disparate associates both of a sensorial and of a motor kind. Cf. Donders, Archiv f. Ophthalmologie, Bd. 13 (1807). The basis of his essay is that we cannot feel on which eye any particular ele. ment of a compound picture falls, but its effects on our total perception differ in the two eyes.

one of these spots and aft, and the other and ef. Volkmann s experiments show this. He and Fechner, prompted by Czermak's observation that the skin of the blind was twice as discriminative as that of seeing folks, sought by experi ment to show the effects of practice upon themselves. They discovered that even within the limits of a single sitting the distances at which points were felt double might fall at the end to considerably less than half of their magnitude at the beginning ; and that some, though not all, of this improved sensibility was retained next day. But they also found that exercising one part of the skin in this way improved the discrimination not only of the corresponding part of the opposite side of the body, but of the neighbor ing parts as well. Thus, at the beginning of an experimen tal sitting, the compass-points had to be a Paris line asun der, in order to be distinguished by the little-finger-tip. But after exercising the other fingers, it was found that the little-finger-tip could discriminate points only half a line apart.* The same relation existed betwixt divers points of the arm and hand.f

Here it is clear that the cause which I first suggested fails to apply, and that we must invoke another. What are the exact experimental phenomena? The spots, as such, are not distinctly located, and the difference, as such, between their feelings, is not distinctly felt, until the interval is greater than the minimum required for the mere perception of their doubleness. What we first feel is a bluntness, then a suspicion of doubleness, which presently becomes a distinct doubleness, and at last two differentfeeling and differently placed spots with a definite tract of space between them. Some of the places we try give us this latest stage of the perception immediately ; some only give us the earliest ; and between them are intermediary places. But as soon as the image of the doubleness as it is felt in the more discriminative places gets lodged in our memory, it helps us to find its like in places where other wise we might have missed it, much as the recent hearing of

an ' overtone ' helps us to detect the latter in a compound sound (supra, pp. 439-40). A dim doubleness grows clearer by being assimilated to the image of a distincter doubleness felt a moment before. It is interpreted by means of the latter. And so is any difference, like any other sort of im pression, more easily perceived when we carry in our rnind to meet it a distinct image of what sort of a thing we are to look for, of what its nature is likely to be.*

These two processes, the reinforcement of the terms by disparate associates, and the tilling of the memory with past differences, of similar direction with the present one, but of more conspicuous amount, are the only explanations I can offer of the effects of education in this line. What is accomplished by both processes is essentially the same thing : they make small differences affect us as if they were large ones — that large differences should affect us as they do remains an inexplicable fact. In principle these two pro cesses ought to be sufficient to account for all possible cases. Whether in fact they are sufficient, whether there be no residual factor which we have failed to detect and analyze out, I will not presume to decide.

It will be remembered that on page 509 personal inter est was named as a sharpener of discrimination alongside of practice. But personal interest probably acts through attention and not in any immediate or specific way. A distinction in which we have a practical stake is one which we concentrate our minds upon and which we are on the look-out for. AVe draw it frequently, and we get all the benefits of so doing, benefits which have just been ex plained. Where, on the other hand, a distinction has no practical interest, where we gain nothing by analyzing a feature from out of the compound total of which it forms a

* Professor Lipps accounts for the tactile discrimination of the blind in a way which (divested of its < mythological ' assumptions) seems to me essentially to agree with this. Stronger ideas are supposed to raise weaker ones over the threshold of consciousness by fusing w'th them, the tenden cy to fuse being proportional to the similarity of the ideas Cf. Grmidtiit sachen, etc., pp. 233-3 ; also pp. 118, 492, 52G-7. part, we contract a habit of leaving it unnoticed, and at last grow callous to its presence. Helmholtz was the first psy chologist who dwelt on these facts as emphatically as they deserve, and I can do no better than quote his very words.

"We are accustomed," he says, " in a large number of cases where sensations of different kinds, or in different parts of the body, exist simultaneously, to recognize that they are distinct as soon as they are perceived, and to direct our attention at will to any one of them sepa rately. Thus at any moment we can be separately conscious of what we see, of what we hear, of what we feel ; and distinguish what we feel in a finger or in the great toe, whether pressure, gentle touch, or warmth. So also in the field of vision. Indeed, as I shall endeavor to show in what follows, we readily distinguish our sensations from one another when we have a precise knowledge that they are composite, as, for example, when we have become certain, by frequently repeated and invariable experience, that our present sensation arises from the simul taneous action of many independent stimuli, each of which usually ex cites an equally well-known individual sensation."

This, it will be observed, is only another statement of our law, that the only individual components which we can pick out of compounds are those of which we have inde pendent knowledge in a separate form. ' ' This induces us to think that nothing can be easier, when a num ber of different sensations are simultaneously excited, than to distin guish them individually from each other, and that this is an innate faculty of our minds. "Thus we find, among other things, that it is quite a matter of course to hear separately the different musical tones which come to our senses collectively; and we expect that in every case when two of them occur together, we shall be able to do the like.

' ' The matter becomes very different when we set to workto investi gate the more unusual cases of perception, and seek more completely to understand the conditions under which the above-mentioned distinction can or cannot be made, as is the case in the physiology of the senses. We then become aware that two different kinds or grades must be dis tinguished in our becoming conscious of a sensation. The lower grade of this consciousness is that in which the influence of the sensation in question makes itself felt only in the conceptions we form of external things and processes, and assists in determining them. This can take place without our needing, or indeed being able, to ascertain to what particular part of our sensations we owe this or that circumstance ia our perceptions. In this case we will say that the impression of ttw sensation in question is perceived synthetically. The second higher grade is when we immediately distinguish the sensation in question a?.

an existing part of the sum of the sensations excited in us. We will say, then, that the sensation is perceived analytically. The two cases must be carefully distinguished from each other." * By the sensation being perceived synthetically, Helmholtz means that it is not discriminated at all, but only felt in a mass with other simultaneous sensations. That it is felt there he thinks is proved by the fact that our judg ment of the total will change if anything occurs to alter the outer cause of the sensation. f The following pages from an earlier edition show what the concrete cases of synthetic perception and what those of analytic perception are wont to be :

" In the use of our senses, practice and experience play a much larger part than we ordinarily suppose. Our sensations are in the first in stance important only in so far as they enable us to judge rightly of the world about us ; and our practice in discriminating between them usually goes only just far enough to meet this end. We are, however, too much disposed to think that we must be immediately conscious of every ingredient of our sensations. This natural prejudice is due to the fact that we are indeed conscious, immediately and without effort, of everything in our sensations which has a bearing upon those practi cal purposes, for the sake of which we wish to know the outer world. Daily and hourly, during our whole life, we keep our senses in training for this end exclusively, and for its sake our experiences are accumu lated. But even within the sphere of these sensations, which do corre spond to outer things, training and practice make themselves felt. It is well known how much finer and quicker the painter is in discriminating colors and illuminations than one whose eye is not trained in these matters ; how the musician and the musical-instrument maker perceive with ease and certainty differences of pitch and tone which for the car of the layman do not exist ; and how even in the inferior realms of cookery and wine-judging it takes a long habit of comparing to make a master. But more strikingly still is seen the effect of practice when we pass to sensations which depend only on inner conditions of oui organs, and which, not corresponding at all to outer things or to their effects upon us, are therefore of no value in giving us information about the outer world.

The physiology of the sense-organs has, in n times, made us acquainted with a number of such phenomena, discov ered partly in consequence of theoretic speculations and questionings, partly by individuals, like Goethe and Purkinje, specially endowed ^ by nature with talent for this sort of observation. These so-called subjec- f Compare as to this, however, what 1 said above, Chapter V, pp tive phenomena are extraordinarily hard to find ; and when they are once found, special aids for the attention are almost ahrays required to observe them. It is usually hard to notice the phenomenon again even when one knows already the description of the first observer. Th< reason is that we are not only unpractised in singling out these subjec tive sensations, but that we are, on the contrary, most thoroughly trained in abstracting our attention from them, because they would only hinder us in observing the outer world. Only when their inten sity is so strong as actually to hinder us in observing the outer world do we begin to notice them ; or they may sometimes, in dreaming and delirium, form the starting point of hallucinations.

" Let me give a few well-known cases, taken from physiological optics, as examples. Every eye probably contains muscce, volttantes, so called ; these are fibres, granules, etc., floating in the vitreous humor, throwing their shadows on the retina, and appearing in the field of vision as little dark moving spots. They are most easily detected by looking at tentively at a broad, bright, blank surface like the sky. Most persons who have not had their attention expressly called to the existence of these figures are apt to notice them for the first time when some ail ment befalls their eyes and attracts their attention to the subjective state of these organs. The usual complaint then is that the muscce volitantes came in with the malady ; and this often makes the patients very anxious about these harmless things, and attentive to all their peculiarities. It is then hard work to make them believe that these figures have existed throughout all their previous life, and that all healthy eyes contain them. I knew an old gentleman who once had occasion to cover one of his eyes which had accidentally become dis eased, and who was then in no small degree shocked at finding that his other eye was totally blind ; with a sort of blindness, moreover, which must have lasted years, and yet he never was aware of it.

" Who, besides, would believe without performing the appropriate ex periments, that when one of his eyes is closed there is a great gap, the socalled ' blind spot,' not far from the middle of the field of the open eye, in which he sees nothing at all, but which he fills out with his imagination ? Mariotte, who was led by theoretic speculations to discover this phenomenon, awakened no small surprise when he showed it at the court of Charles II. of England. The experiment was at that time repeated with many variations, and became a fashioaable amusement. The gap is, in fact, so large that seven full moons alongside of each other would not cover its diameter, and that a man's face 6 or 7 feet off disappears within it. In our ordinary use of vision this great hole in the field fails utterly to be noticed ; because our eyes are constantly wandering, and the moment an object interests us we turn them full upon it. So it follows that the object which at any actual moment excites our attention never happens to fall upon this gap, and thus it is that we never grow conscious of the blind spot in the field. In order to notice it, we must first purposely rivet our gaze upon one object and

then move about a second object in the neighborhood of the blind spot, striving meanwhile to attend to this latter without moving the direction of our gaze from the first object. This runs counter to all our habits, and is therefore a difficult thing to accomplish. With some people it is even an impossibility. But only when it is accomplished do we see the second object vanish and convince ourselves of the existence of this gap. "Finally, let me refer to the double images of ordinary binocular vision. Whenever we look at a point with both eyes, all objects on this side of it or beyond it appear double. It takes but a moderate effort of observation to ascertain this fact ; and from this we may conclude that we have been seeing the far greater part of the external world double all our lives, although numbers of persons are unaware of it, and are in the highest degree astonished when it is brought to their attention. As a matter of fact, we never have seen in this double fashion any particular object upon which our attention was directed at the time ; for upon such objects we always converge both eyes. In the habitual use of our eyes, our attention is always withdrawn from such objects as give us double images at the time ; this is the reason why we so seldom learn that these images exist. In order to find them we must set our attention a new and unusual task ; we must make it explore the lateral parts of the field of vision, not, as usual, to find what objects are there, but to analyze our sensations. Then only do we notice this phenomenon.*

" The same difficulty which is found in the observation of subjective sensations to which no external object corresponds is found also in the analysis of compound sensations which correspond to a single object. Of this sort are many of our sensations of sound. When the sound of a violin, no matter how often we hear it, excites over and over again in our ear the same sum of partial tones, the result is that our feeling of this sum of tones ends by becoming for our mind a mere sign for the voice of the violin. Another combination of partial tones becomes the sensible sign of the voice of a clarionet, etc. And the oftener any such combination is heard, the more accustomed we grow to perceiving it as an integral total, and the harder it becomes to analyze it by immediate observation. I believe that this is one of the principal reasons why the analysis of the notes of the human voice in singing is relatively so

* When a person squints, double images are formed in the centre of the field. As a matter of fact, most squinters are found blind of one eye, or almost so ; and it has long been supposed amongst ophthalmologists that the blindness is a secondary affection superinduced by the voluntary sup pression of one of the sets of double images, in other words by the positive and persistent refusal to use one of the eyes. This explanation of the blindness has, however, been called in question of late years. See, for a brief account of the matter, O. F. Wadsworth in Boston Med. and Surg. Journ., cxvi. 49 (Jan. 20, '87), and the replies by Derby and others a little later.— W. J.

difficult. Such fusions of many sensations into what, to conscious perception, seems a simple whole, abound in all our senses. "Physiological optics affords other interesting examples. The per ception of the bodily form of a near object comes about through the combination of two diverse pictures which the eyes severally receive from it, and whose diversity is due to the different position of each eye, altering the perspective view of what is before it. Before the invention of the stereoscope this explanation could only be assumed hypothetically ; but it can now be proved at any moment by the use of the instrument. Into the stereoscope we insert two flat drawings, representing the two perspective views of the two eyes, in such a manner that each eye sees its own view in the proper place ; and we obtain, in consequence, the perception of a single extended solid, as complete and vivid as if we had the real object before us.

" Now we can, it is true, by shutting one eye after the other and at tending to the point, recognize the difference in the pictures — at least when it is not too small. But, for the stereoscopic perception of solidity, pictures suffice whose difference is so extraordinarily slight as hardly to be recognized by the most careful comparison ; and it is certain that, in our ordinary careless observing of bodily objects, we never dream that the perception is due to two perspective views fused into one, be cause it is an entirely different kind of perception from that of either flat perspective view by itself. It is certain, therefore, that two different sensations of our two eyes fuse into a third perception entirely different from either. Just as partial tones fuse into the perception of a certain instrument's voice ; and just as we learn to separate the partial tones of a vibrating string by pinching a nodal point and letting them sound in isolation ; so we learn to separate the images on the two eyes by opening and closing them alternately.

"There are other much more complex instances of the way in which many sensations may combine to serve as the basis of a quite simple perception. When, for example we perceive an object in a certain direction, we must somehow be impressed by the fact that certain of our optic nerve-fibres, and no others, are impressed by its light. Fur thermore, we must rightly judge the position of our eyes in our head, and of our head upon our body, by means of feelings in our eye-muscles and our neck-muscles respectively. If any of these processes is dis turbed we get a false perception of the object's position. The nervefibres can be changed by a prism before the eye; or the eyeball's position changed by pressing the organ towards one side; and such experiments show that, for the simple seeing of the position of an object, sensations of these two sorts must concur. But it would be quite impossible to gather this directly from the sensible impression which the object makes. Even when we have made experiments and convinced ourselves in every possible manner that such must be the fact, it still remains hidden from our immediate introspective observation.

"These examples" [of 'synthetic perception,' perception in which each contributory sensation is felt in the whole, and is a co-determinant of what the whole shall be, but does not attract the attention to its separate self] " may suffice to show the vital part which the direction of attention and practice in observing play in sense-perception. To apply this now to the ear. The ordinary task which our ear has to solve when many sounds assail it at once is to discern the voices of the several sounding bodies or instruments engaged ; beyond this it has no objective interest in analyzing. We wish to know, when many men are speaking together, what each one says, when many instruments and voices combine, which melody is executed by each. Any deeper analysis, such as that of each separate note into its partial tones (although it might be performed by the same means and faculty of hearing as the first analysis) would tell us nothing new about the sources of sound actually present, but might lead us astray as to their number. For this reason we confine our attention in analyzing a mass of sound to the several instruments' voices, and expressly abstain, as it were, from discriminating the elementary components of the latter. In this last sort of discrimination we are as unpractised as we are, on the contrary, well trained in the former kind." *

* Tonempfindungen, Dritte Auflage, pp. 102-107.— The reader who has assimilated the contents of our Chapter V, above, will doubtless have remarked that the illustrious physiologist has fallen, in these para graphs, into that sort of interpretation of the facts which we there tried to prove erroneous. Helmholtz, however, is no more careless than most psychologists in confounding together the object perceived, the organic conditions of the perception, and the sensations which would be excited by the several parts of the object, or by the several organic conditions, provided they came into action separately or were separately attended to, and in assuming that what is true of any one of these sorts of fact must be true of the other sorts also. If each organic condition or part of the object is there, its sensation, he thinks, must be there also, only in a ' synthetic ' — which is indistinguishable from what the authors whom we formerly reviewed called an ' unconscious ' — state. I will not repeat argu ments sufficiently detailed in the earlier chapter (see especially pp. 170-176), but simply say that what he calls the ' fusion of many sensations into one ' is really the production of one sensation by the co-operation of many organic conditions; and that what perception fails to discriminate (when it is ' synthetic') is not sensations already existent but not singled out, but new objective/acte, judged truer than the facts already synthetically perceived — two views of the solid body, many harmonic tones, instead of one view and one tone, states of the eyeball-muscles thitherto unknown, and the like. These new facts, when first discovered, are known in states of conscious ness never till that moment exactly realized before, states of consciousness which at the same time judge them to be determinations of the same matter of fact which was previously realized.

All that Helmholtz says of the conditions which hinder and further analysis applies just as naturally to the analysis, through the advent of new feelings, of objects into their ele After all we have said, no comment seems called for upon these interesting and important facts and reflections of Helrnholtz. ments, as to the analysis of aggregate feelings into elementary feelings sup posed to have been hidden in them all the while. The reader can himself apply this criticism to the following passages from Lotze and Sttimpf respectively, which I quote because they are the ablest expressions of the view opposed to my own. Both authors, it seems to me, commit the psychologist's fallacy, and allow their later knowledge of the things felt to be foisted into their account of the primitive way of feeling them.

Lotze says: "It is indubitable that the simultaneous assault of a variety of different stimuli on different senses, or even on the same sense, puts us into a state of confused general feeling in which we are certainly not conscious of clearly distinguishing the different impressions. Still it does not follow that in such a case we have a positive perception of an actual unity of the contents of our ideas, arising from their mixture ; our state of mind seems rather to consist in (1) the consciousness of our inabil ity to separate what really has remained diverse, and (2) in the general feeling of the disturbance produced in the economy of our body by the simultaneous assault of the stimuli. . . . Not that the sensations melt into one another, but simply that the act of distinguishing them is absent; and this again certainly not so far that the fact of the difference remains entirely unperceived, but only so far as to prevent us from determining the amount of the difference, and from apprehending other relations between the different impressions. Anyone who is annoyed at one and the same time by glowing heat, dazzling light, deafening noise, and an offensive smell, will certainly not fuse these disparate sensations into a single one with a single content which could be sensuously perceived ; they remain for him in separation, and he merely finds it impossible to be conscious of one of them apart from the others. But, further, he will have a feeling of discomfort — what I mentioned above as the second constituent of his whole state.

For every stimulus which produces in consciousness a definite con tent of sensation is also a definite degree of disturbance, and therefore makes a call upon the forces of the nerves ; and the sum of these little changes, which in their character as disturbances are not so diverse as the contents of consciousness they give rise to, produce the general feeling which, added to the inability to distinguish, deludes us into the belief in an actual absence of diversity in our sensations. It is only in some such way as this, again, that I can imagine that state which is sometimes de scribed as the beginning of our whole education, a state which in itself is supposed to be simple, and to be afterwards divided into different sensa tions by an activity of separation. No activity of separation in the world could establish differences where no real diversity existed ; for it would have nothing to guide it to the places where it was to establish them, or to indicate the width it was to give them.'' (Metaphysic, §260, English translation.)