The Principles of Psychology, Vols. 1-2

Stumpf writes as follows : " Of coexistent sensations there are aJ The time required for discrimination has been made a subject of experimental measurement. Wundt calls it Un- terscheidungszeit. His subjects (whose simple reaction -time — see p. 85 ft'.— had previously been determined) were re quired to make a movement, always the same, the instant they discerned which of two or more signals they received. The exact time of the signal and that of the movement were automatically registered by a galvanic chronoscope. The particular signal to be received was unknown in ad vance, and the excess of time occupied by those reactions in which its character had first to be discerned, over the simple reaction-time, measured, according to Wundt, the time required for the act of discrimination. It was found longer when four different signals were irregularly used than when only two were used. In the former case it averaged, for three observers respectively (the signals be ing the sudden appearance of a black or of a white object),

ways a large number undiscriminated in consciousness, or (if one prefer to call what is undiscriminated unconscious) in the soul. They are, how ever, not fused into a simple quality. When, on entering a room, we receive sensations of odor and warmth together, without expressly attend ing 1o either, the two qualities of sensation are not, as it were, an entirely new simple quality, which first at the moment in which attention analyti cally steps in changes into smell and warmth. ... In such cases we find ourselves in presence of an indefinable, unmiinable total of feeling. And when, after successfully analyzing this total, we call it back to memory, as it was in its unanalyzed state, and compare it with the elements we have found, the latter (as it seems to me) may be recognized as real parts con tained in the former, and the former seen to be their sum. So, for example, when we clearly perceive that the content of our sensation of oil of peppermeiit is partly a sensation of taste and partly one of temperature." (Tonpay chologie, 1. 107.)

I should prefer to say that we perceive that objective fact, known to us as the peppermint taste, to contain those other objective facts known as aromatic or sapid quality, and coldness, respectively. No ground to sup pose that the vehicle of this last very complex perception has any identity with the earlier psychosis— least of all is contained in it. In the latter case, a red and a green signal being added to the former ones, it became, for the same observers,

Later, in Wundt's Laboratory, Herr Tischer made many careful experiments after the same method, where the facts to be discriminated were the different degrees of loudness in the sound which served as a signal. I subjoin Herr Tischer's table of results, explaining that each vertical col umn after the first gives the average results obtained from a distinct individual, and that the figure in the first column stands for the number of possible loudnesses that might be expected in the particular series of reactions made. The times are expressed in thousandths of a second.

The interesting points here are the great individual varia tions, and the rapid way in which the time for discrimina tion increases with the number of possible terms to dis criminate. The individual variations are largely due to want of practice in the particular task set, but partly also to discrepancies in the psychic process. One gentleman said, for example, that in the experiments with three sounds, he kept the image of the middle one ready in his mind, and compared what he heard as either louder, lower, or the same. His discrimination among three possibilities became thus very similar to a discrimination between two. if Mr. J. M. Cattell found lie could get no results by this method,§ and reverted to one used by observers previous

§ Mind, xi. 377 if. He says: " I apparently either distinguished the impression and made the motion simultaneously, or if I tried to avoid this by waiting until I had formed a distinct impression before I began to make the motion, I added to the simple reaction, not only a perception, but a volition." — Which remark may well confirm our doubts as to the strict psychologic worth of any of these measurements. to Wundt and which Wundt had rejected. This is the einfache Wahlmethode, as Wundt calls it. The reacter awaits the signal and reacts if it is of one sort, but omits to act if it is of another sort. The reaction thus occurs after discrimination ; the motor impulse cannot be sent to the hand until the subject knows what the signal is. The nervous impulse, as Mr. Cattell says, must probably travel to the cortex and excite changes there, causing in conscious ness the perception of the signal. These changes occupy the time of discrimination (or perception-time, as it is called by Mr. C.) But then a nervous impulse must descend from the cortex to the lower motor centre which stands primed and ready to discharge ; and this, as Mr. C. says, gives a will-time as well. The total reaction-time thus includes both ' will-time ' and * discrimination-time.' But as the centrifugal and centripetal processes occupying these two times respectively are probably about the same, and the time used in the cortex is about equally divided between the perception of the signal and the preparation of the motor discharge, if we divide it equally between percep tion (discrimination) and volition, the error cannot be great.* We can moreover change the nature of the per ception without altering the will-time, and thus investigate with considerable thoroughness the length of the percep tion-time.

Guided by these principles, Prof. Cattell found the time required for distinguishing a white signal from no signal to be, in two observers : that for distinguishing one color from another was simi larly : that for distinguishing a certain color from ten other col ors : that for distinguishing the letter A in ordinary print from the letter Z : that for distinguishing a given letter from all the rest of the alphabet (not reacting until that letter appeared)

that for distinguishing a word from any of twenty-five other words, from The difference depending on the length of the words and the familiarity of the language to which they belonged. Prof. Cattell calls attention to the fact that the time for distinguishing a word is often but little more than that for distinguishing a letter : "We do not, therefore, distinguish separately the letters of which a word is composed, but the word as a whole. The application ofthis in teaching children to read is evident."

He also finds a great difference in the time with which various letters are distinguished, E being particularly bad.* I have, in describing these experiments, followed the ex ample of previous writers and spoken as if the process by which the nature of the signal determines the reaction were identical with the ordinary conscious process of discrimina tive perception and volition. I am convinced, however, that this is not the case ; and that although the results are the same, the form of consciousness is quite different. The reader will remember my contention (supra, p. 90 ff.) that the simple reaction-time (usually supposed to include a conscious pro cess of perceiving) really measures nothing but a reflex act. Anyone who will perform reactions with discrimina tion will easily convince himself that the process here also is far more like a reflex, than like a deliberate, operation. I have made, with myself and students, a large number of measurements where the signal expected was in one series a touch someivliere on the skin of the back and head, and in another series a spark somewhere in the field of view. The hand had to move as quickly as possible towards the

* For other determinations of discrimination-time by this method cf. v. Kries and Auerbach, Archiv f. Physiologic, Bd. i. p. 297 ff. (these au thors get much smaller figures); Fricdrich, Psychologische Studien, i. 39. Chapter ix of Buccola's book, Le Legge del tempo, etc., gives a full ac count of the subject. place of the touch or the spark. It did so infallibly, and sensibly instantly ; whilst both place and movement seemed to be perceived only a moment later, in memory. These ex periments were undertaken for the express purpose of ascer taining whether the movement at the sight of the spark was discharged immediately by the visual perception, or whether a * motor-idea ' had to intervene between the perception of the spark and the reaction.* The first thing that was mani fest to introspection was that no perception or idea of any sort preceded the reaction. It jumped of itself, whenever the signal came ; and perception was retrospective. We must suppose, then, that the state of eager expectancy of a certain definite range of possible discharges, innervates a whole set of paths in advance, so that when a particular sensation comes it is drafted into its appropriate motor outlet too quickly for the perceptive process to be aroused. In the experiments I describe, the conditions were most favorable for rapidity, for the connection between the signals and their movements might almost be called iiinace. It is instinctive to move the hand towards a thing seen or a skin-spot touched. But where the movement is conventionally attached to the signal, there would be more chance for delay, and the amount of practice would then determine the speed. This is well shown in Tischer's re sults, quoted on p. 524, where the most practised observer, Tischer himself, reacted in one eighth of the time needed by one of the others. f But what all investigators have aimed to determine in these experiments is the minimum time. I trust I have said enough to convince the student that this minimum time by no means measures what we consciously know as discrimination. It only measures something which, under the experimental conditions, leads

* If so, the reactions upon the spark would have to be slower than those upon the touch. The investigation was abandoned because it was found impossible to narrow down the difference between the conditions of the sight-series and those of the touch-series, to nothing more than the possible presence in the latter of the intervening motor-idea. Other dis parities could not be excluded. f Tischer gives figures from quite unpractised individuals which I have not quoted. The discrimination-time of one of them is 22 times longer than Tischer's own ! (Psychol Studieu, i. 527.)

to a similar result. But it is the bane of psychology to suppose that where results are similar, processes must be the same. Psychologists are too apt to reason as geometers would, if the latter were to say that the diameter of a circle is the same thing as its semi-circumference, because, for sooth, they terminate in the same two points.* The perception of likeness is practically very much bound up with that of difference. That is to say, the only differ ences we note as differences, and estimate quantitatively, and arrange along a scale, are those comparatively limited dif ferences which we rind between members of a common genus. The force of gravity and the color of this ink are things it never occurred to me to compare until now that I am casting about for examples of the incomparable. Similarly the elastic quality of this india-rubber band, the comfort of last night's sleep, the good that can be done with a legacy, these are things too discrepant to have ever been compared ere now. Their relation to each other is less that of difference than of mere logical negativity. To be found different, things must as a rule have some commensurability, some aspect in common, which suggests the possibility of their being treated in the same way. This is of course not a theoretic necessity — for any distinction may be called a 1 difference,' if one likes — but a practical and linguistic re mark.

The same things, th en, which arouse the perception of difference usually arouse that of resemblance also. And the analysis of them, so as to define Avherein the difference and wherein the resemblance respectively consists, is called comparison. If we start to deal with the things as simply the same or alike, we are liable to be surprised by the difference. If we start to * Compare Lipps's excellent passage to the same critical effect in bis Grundtatsaclien des Seelenlebens, pp. 390-393. — I leave my text just as it was written before tbe publication of Lange's and Mtinsterberg's results cited on pp. 92 and 432. Tbeir 'shortened' or 'muscular' times, got when the expectant attention was addressed to the possible reactions rather than to the stimulus, constitute the minimal reaction-time of which I speak, aud all that I say in the text falls beautifully into line with their results.

treat them as merely different, we are apt to discover how much they are alike. Difference, commonly so called, is thus betivecn species of a genus. And the faculty by which we perceive the resemblance upon which the genus is based, is just as ultimate and inexplicable a mental endowment as that by which we perceive the differences upon which the species depend. There is a shock of likeness when we pass from one thing to another which in the first instance we merely discriminate numerically, but, at the moment of bringing our attention to bear, perceive to be similar to the first ; just as there is a shock of difference when we pass be tween two dissimilars.* The objective extent of the like ness, just like that of the difference, determines the magni tude of the shock. The likeness may be so evanescent, or the basis of it so habitual and little liable to be attended to, that it will escape observation altogether. Where, how ever, we find it, there we make a genus of the things com pared ; and their discrepancies and incommensurabilities in other respects can then figure as the differentiae, of so many species. As ' thinkables ' or ' existents ' even the smoke of a cigarette and the worth of a dollar-bill are comparable — still more so as 'perishables,' or as ' enjoyables.'

Much, then, of what I have said of difference in the course of this chapter will apply, with a simple change of language, to resemblance as well. We go through the world, carrying on the two functions abreast, discovering differences in the like, and likenesses in the different. To abstract the ground of either difference or likeness (where it is not ultimate) demands an analysis of the given objects into their parts. So that all that was said of the depend ence of analysis upon a preliminary separate acquaintance with the character to be abstracted, and upon its having varied concomitants, finds a place in the psychology of re semblance as well as in that of difference.

But when all is said and done about the conditions which favor our perception of resemblance and our ab straction of its ground, the crude fact remains, that some people are far more sensitive to resemblances, and far more ready to point out wherein they consist, than others are. They are the wits, the poets, the inventors, the scientific men, the practical geniuses. A native talent for perceiving analogies is reckoned by Prof. Bain, and by others before and after him, as the leading fact in genius of every order. But as this chapter is already long, and as the question of genius had better wait till Chapter XXII, where its practical consequences can be discussed at the same time, I will say nothing more at present either about it or about the faculty of noting resemblances. If the reader feels that this faculty is having small justice done it at rny hands, and that it ought to be wondered at and made much more of than has been done in these last few pages, he will per haps find some compensation when that later chapter is reached. I think I emphasize it enough when I call it one of the ultimate foundation-pillars of the intellectual life, the others being Discrimination, Retentiveness, and Asso ciation.

On page 489 I spoke of differences being greater or less, and of certain groups of them being susceptible of a linear arrangement exhibiting serial increase. A series whose terms grow more and more different from the starting point is one whose terms grow less and less like it. They grow more and more like it if you read them the other way. So that likeness and unlikeness to the starting point are functions inverse to each other, of the position of any term in such a series.

Professor Stumpf introduces the word distance to de note the position of a term in any such series. The less like is the term, the more distant it is from the start ing point. The ideally regular series of this sort would be one in which the distances — the steps of resemblance or difference — between all pairs of adjacent terms were equal. This would be an evenly gradated series. And it is an interesting fact in psychology that we are able, in many departments of our sensibility, to arrange the terms without difficulty in this evenly gradated way. Dif-

ferences, in other words, between diverse pairs of terms, a and 6, for example, on the one hand, and c and d on the other,* can be judged equal or diverse in amount. The dis tances from one term to another in the series are equal. Linear magnitudes and musical notes are perhaps the im pressions which we easiest arrange in this way. Next come shades of light or color, which we have little difficulty in arranging by steps of difference of sensibly equal value. Messrs. Plateau and Delbceuf have found it fairly easy to determine what shade of gray will be judged by every one to hit the exact middle between a darker and a lighter shade, f

How now do we so readily recognize the equality of two differences between different pairs of terms? or, more briefly, how do we recognize the magnitude of a difference at all V Prof. Stumpf discusses this question in an inter esting way ; ^ and comes to the conclusion that our feeling for the size of a difference, and our perception that the terms of two diverse pairs are equally or unequally distant from each other, can be explained by no simpler mental process, but, like the shock of difference itself, must be regarded as for the present an unanalyzable endowment

* The judgment becomes easier if the two couples of terms have one member in common, if a — b and b — c, for example, are compared. This, as Stumpf says (Toupsychologie, i. 131), is probably because the introduction of the fourth term brings involuntary crosscomparisons with it, a and b with d, b with c, etc., which confuses us by withdrawing our attention from the relations we ought alone to be estimating. f J. Delbceuf : Elements de Psych ophysique (Paris, 1883), p. 64. Pla teau in Stumpf, Tonpsych., i. 125. I have noticed a curious enlargement of certain 'distances' of difference under the influence of chloroform. The jingling of the bells on the horses of a horse car passing the door, for example, and the rumbling of the vehicle itself, which to our ordinary hearing merge together very readily into a quasi-coulimious body of sound, have seemed so far apart as to require a sort of mental facing in opposite directions to get from one to the other, as if they belonged in dif ferent worlds. I am inclined to suspect, from certain data, that the ulti mate philosophy of difference and likeness will have to be built upon experiences of intoxication, especially by nitrous oxide gas, which lets MS into intuitions the subtlety whereof is denied to the waking state. Cf. B. P. Blood : The Anaesthetic Revelation, and the Gist of Philosophy (Am sterdam, N. Y., 1874). Cf. also Mind, vn. 200.

of the mind. This acute author rejects in particular the notion which would make our judgment of the distance between two sensations depend upon our mentally travers ing the intermediary steps. We may of course do so, and may often find it useful to do so, as in musical intervals, or figured lines, But we need not do so ; and nothing more is really required for a comparative judgment of the amount of a 'distance' than three or four impressions belonging to a common kind.

The vanishing of all perceptible difference between two numerically distinct things makes them qualitatively the same or equal. Equality, or qualitative (as distinguished from numerical) identity, is thus nothing but the extreme degree of likeness.* We saw above (p. 492) that some persons consider that the difference between two objects is constituted of two things, viz., their absolute identity in certain respects, plus their absolute non-identity in others. We saw that this theory would not apply to all cases (p. 493). So here any theory which would base likeness 011 identity, and not rather iden tity on likeness, must fail. It is supposed perhaps, by most people, that two resembling things owe their resemblance to their absolute identity in respect of some attribute or attributes, combined with the absolute non-identity of the rest of their being. This, which may be true of compound things, breaks down when we come to simple impressions.

" When we compare a deep, a middle, and a high note, e.g. (7, /sharp, a'", we remark immediately that the first is less like the third than the second is. The same would be true of c d e in the same region of the scale. Our very calling one of the notes a ' middle ' note is the expres sion of a judgment of this sort. But where here is the identical and where the non-identical part ? We cannot think of the overtones ; for the first-named three notes have none in common, at least not on musi cal instruments. Moreover, we might take simple tones, and still our judgment would be unhesitatingly the same, provided the tones were not chosen too close together. . . . Neither can it be said that the identity consists in their all being sounds, and not a sound, a smell, and a color, respectively. For this identical attribute comes to each of them in equal measure, whereas the first, being less like the third than the second is, ought, on the terms of the theory we are criticising, to have

less of the identical quality. . . . It thus appears impracticable to define all possible cases of likeness as partial identity plus partial disparity; and it is vain to seek in all cases for identical elements."* And as all compound resemblances are based on simple ones like these, it follows that likeness iiberhaupt must not be conceived as a special complication of identity, but rather that identity must be conceived as a special degree of likeness, according to the proposition expressed at the outset of the paragraph that precedes. Likeness and dif ference are ultimate relations perceived. As a matter of fact, no two sensations, no two objects of all those we know, are in scientific rigor identical. We call those of them identical whose difference is unperceived. Over and above this we have a conception of absolute sameness, it is true, but this, like so many of our conceptions (cf. p. 508), is an ideal construction got by following a certain direction of serial increase to its maximum supposable extreme. It plays an important part, among other permanent meanings possessed by us, in our ideal intellectual constructions. But it plays no part whatever in explaining psychologically how we perceive likenesses between simple things.

In 1860, Professor G. T. Feclmer of Leipzig, a man of great learning and subtlety of mind, published two volumes entitled ' Psychophysik,' devoted to establishing and ex plaining a law called by him the psychophysic law, which * Stumpf, pp. 1 16-7. I have omitted, so as not to make my text too intri cate, an extremely acute and conclusive paragraph, which I reproduce here : " We may generalize : Wherever a numBer of sensible impressions are apprehended as a series, there in the last instance must perceptions of sim ple likeness be found. Proof: Assume that all the terms of a series, e.g. the qualities of tone, c d efg, have something in common, — no matter what it is, call it X; then I say that the differing parts of eacli of these terms must not only be differently constituted in each, but must themselves form a series, whose existence is the ground for our apprehending the original terms in serial form. We thus get instead of the original series a b c d ef . . . the equivalent series X(r, Xft, Xy, . . . etc. What is gained ? The question immediately arises : How is a ft y known as a series? According to the theory, these elements must themselves be made up of -i part common to all, and of parts differing in each, which latter parts form a new series, and so on ad infinitum, which is absurd."

he considered to express the deepest and most elementary relation between the mental and the physical worlds. It is a formula for the connection between the amount of our sensations and the amount of their outward causes. Its simplest expression is, that when we pass from one sensa tion to a stronger one of the same kind, the sensations in crease proportionally to the logarithms of their exciting causes. Feclmer's book was the starting point of a new department of literature, which it would be perhaps impos sible to match for the qualities of thoroughness and sub tlety, but of which, in the humble opinion of the present writer, the proper psychological outcome is just nothing. The psychophysic law controversy has prompted a good many series of observations on sense-discrimination, and has made discussion of them very rigorous. It has also cleared up our ideas about the best methods for getting average results, when particular observations vary ; and beyond this it has done nothing ; but as it is a chapter in the history of our science, some account of it is here due to the reader.

Fechner's train of thought has been popularly expounded a great many times. As I have nothing new to add, it is but just that I should quote an existing account. I choose the one given by Wundt in his Yorlesungen iiber Menschen and Thierseele, 1863, omitting a good deal : "How much stronger or weaker one sensation is than another, we are never able to say. Whether the sun be a hundred or a thousand times brighter than the moon, a cannon a hundred or a thousand times louder than a pistol, is beyond our power to estimate. The natural measure of sensation which we possess enables us to judge of the equal ity, of the ' more ' and of the ' less,' but not of ' how many times more or less.' This natural measure is, therefore, as good as no measure at all, whenever it becomes a question of accurately ascertaining intensi ties in the sensational sphere. Even though it may teach us in a genera] way that with the strength of the outward physical stimulus the strength of the concomitant sensation waxes or wanes, still it leaves us without the slightest knowledge of whether the sensation varies in exactly the same proportion as the stimulus itself, or at a slower or a more rapid rate. In a word, we know by our natural sensibility nothing of the law that connects the sensation and its outward cause together. To find this law we must first find an exact measure for the sensation itself ; we must be able to s;»y : A stimulus of strength one begets a sensation

of strength one; a stimulus of strength two begets a sensation of strength two, or three, or four, etc. But to do this we must first know what a sensation two, three, or four times greater than another signifies. . . . " Space magnitudes we soon learn to determine exactly, because we only measure one space against another. The measure of mental mas mtudes is far more difficult But the problem of measuring the magnitude of sensations is the first step in the bold enterprise of mak ing mental magnitudes altogether subject to exact measurement Were our whole knowledge limited to the fact that the sensation rises when the stimulus rises, and falls when the latter falls, much would not be gained. But even immediate unaided observation teaches us certain facts which, at least in a general way, suggest the law according to which the sensations vary with their outward cause.

"Every one knows that in the stilly night we hear things unnoticed in the noise of day. The gentle ticking of the clock, the air circulating through the chimney, the cracking of the chairs in the room, and a thousand other slight noises, impress themselves upon our ear. It is equally well known that in the confused hubbub of the streets, or the clamor of a railway, we may lose not only what our neighbor says to us, but even not hear the sound of our own voice. The stars which are brightest at night are invisible by day ; and although we see the moon then, she is far paler than at night. Everyone who has luid to deal with weights knows that if to a pound in the hand a second pound be added, the difference is immediately felt ; whilst if it be added to a hundredweight, we are not aware of the difference at all. . . .