Chapter III: Part 3

Do you see that man on the street approaching us at an even gait? Now he is ten yards away, and presently five. What do you say about his size at the two distances? That five yards away it was practically the same as ten yards off? But that is impossible! A simple consideration of geometrical optics will tell you that during the man’s approach his height must have doubled and his breadth too, so that his total size must have become four times the amount it was at ten yards. We transfer the observation from the street into the laboratory. Here I have two cardboard rectangles. The sides of the first have a length of two and three inches, those of the second are six and nine. If now I hold the first before you at a distance of one yard and the second at three yards, you will admit that, optically, they must have the same size approximately, since their linear dimensions vary exactly as do their distances. But you tell me that the further rectangle appears much larger to you than the nearer one? There you have it! Yours cannot be a statement about actual sensory experience. A slight change of conditions will make you realize that my opinion is right. Look through the opening of this screen, which will show you the two rectangles on a homogeneous background, but no more of their surroundings. Do they look different now? Still a little. Then we shall be even more cautious. I darken the room; then I turn the light on, allowing you to make your observation through the screen, only for a small fraction of a second, so that practically no eye-movements can occur during that time. Now both rectangles have the same size, do they not? After some practice you will be able, perhaps, to see them as equally large even without the help of my screen and the short exposure, as soon as you look upon them in the proper way--which is the method of introspection for obtaining pure sensory experience. If you do not accept my demonstration, you might even go so far as to believe that the after-image of an object changes its size according to the distance from which you “project” it upon a screen, because in untrained observation it certainly seems to change considerably, according to the distance of your fixation point. But that is absurd. How could it really change, if the area of the retinal after-effect remain constant?

My second example may be regarded as a natural consequence of the first. When dining with your friends, what forms do the plates have in your experience, those to the left, to the right, and opposite you? They are circular, you say, as is your own plate? Impossible again! They must be elliptical, as you will admit after you have once thought about their projection upon your retina; some of them must even be very flat ellipses, and even your own plate will become an ellipse as soon as your eye does not look down upon it vertically. It will be worth while to apply to this case a procedure similar to the one we used in the first example. On this plane which, as you see, is oblique to the direction of your eye I fix a circle; on this other plane, at right angles to the direction of your eye, I fix an ellipse, whose shape is chosen in such a manner that from its place it is projected upon your retina in the same form as the circle is from its oblique plane. Though you describe the first as a circle and the second as an ellipse, they are two almost identical ellipses in actual sensory experience. Take this screen with two holes in it, which lets you see both forms, but excludes, however, the data by which the angles of the planes became known to you at first. Both forms look alike now? All right. After a short while you will be able to see correctly without the screen, providing you adopt the attitude of introspection. Once more, the corresponding observation on an after-image of a given form, “projected” upon planes of different oblique positions with respect to your line of vision, will elucidate the case completely. Its form seems to vary according to the positions of the plane, though the retinal after-effect has the same form throughout. This being absurd, you see the importance of observing genuine sensory experience by way of introspection.

A similar paradox has been much discussed since Helmholtz wrote his _Physiologische Optik_. Here on this desk near the window, and parallel to it, a vertical screen is fastened. On the window side of the screen I place a black paper on the desk, and in the shadow of the screen, a white paper. These papers are selected in a special manner: the dark one exposed to the direct illumination from the window reflects the same amount of light as the white paper reflects under its low intensity of illumination. You call the first one “black” and the second “white”? Then again you have experiences which are not to be trusted, because under these circumstances the images projected upon your retina are both of them equally intense. So the sensations, i.e., brightnesses, of both must also be the same. Moreover this can be demonstrated. Take this piece of gray cardboard and look through the two holes in it so that one of them is filled by a section of the “black,” and the other by a section of the “white” paper. Now, as the surroundings of the papers are excluded from vision, and thus you have pure sensations before you, their approximate equality is obvious. Again, with a little practice--most painters observe objects this way--you will be able, without the cardboard, to destroy the illusion of their difference--just by looking at the papers in the attitude of introspection.

All these observations are of an illusory sort, then, the purification of which exhibits the true sensory facts. In this and other respects they are comparable to a great many well-known “optical illusions,” the diagrams of which fill many pages in our textbooks. Take the famous Müller-Lyer figures! When you observe them often and try to pick the main line out of its surroundings, you will find the illusion become unstable, and finally it may even disappear. It was not, then, a true sensory fact. The same thing may be shown in another manner. Accurately draw the two figures, one above the other. If now you fix your attention carefully upon the two left ends of the two main lines, you will find the one vertically above the other. Repeating the same observation with the right ends, you find the same result. It follows that both lines have the same length.[10] Similarly you will find all the other illusions variable, according to the attitude of the observer, and avoidable by practice. Therefore they cannot be classed as genuine sensory experience.

Recently, stroboscopic movement has been investigated by some German and American psychologists. Under appropriate conditions successive stimulation by two lights at two points not too distant from each other produces an experience of movement from the first to the second. But if in making your observation in the attitude of introspection, you find nothing but a “gray flash,” must we not be very careful, indeed, before accepting the report of “movement”? Did not the observers of Benussi[11] report similar experiences when their skin was touched successively at two different points? But in their description the movement did not usually occur upon the skin; it formed a curve through empty space touching the skin only at those points. Evidently, such an experience cannot belong to the world of touch alone; it is no genuine sensory fact, then.

If all these are examples of illusions which, for psychological purposes, have to be corrected by introspection, something must transform pure sensory experience so that for untrained people it assumes an illusory character. This is the case indeed, and in most of our examples we can discover that “something” easily enough.

The man approaching us on the street does not grow larger, as for simple optical reasons he should. The circle observed on the oblique plane does not become an ellipse; it seems to remain a circle after its retinal image has become a very flat ellipse. The white object in the shadow remains white, the black paper remains black in full light, though the first may reflect much less light than the second. These three examples have one common property: the physical object _as such_ remaining constant, while actual stimulation varies according to more or less accidental conditions (of distance, of position, of illumination), our experience agrees with the constancy of the physical object much better than with the varying stimulation produced by it. From this fact we draw the simple conclusion that all such apparent constancy in experience is the product of _learning_. Since our early childhood we have observed that a distant object is much bigger, “really,” when we come near to it. In the same way we have learnt that an object situated obliquely in relation to our glance has quite another “real” form when we look at it vertically. Again in the same manner we have observed that an object which we see under abnormal conditions of illumination will show quite another “real” brightness or darkness as soon as conditions become normal. As these observations have been repeated millions of times, our knowledge of the “real” size, the “real” form, the “real” brightness, has become so intimately connected with what we see, that with time we seem to _see_ those constant “real” properties instead of the ever changing ones corresponding to varying stimulation. In short, those facts, though strange at first, are explained by _meaning_, and then completely fit into our scientific system.

We have already seen that probably no experience escapes from the influence of meaning. Hence we do not here introduce a new hypothesis. If untrained people seem to “see” what from this viewpoint is a product only of past learning, that again is an illusion, to be found generally wherever we discover the indirect origin of the experience. Remember the symbol +, which _looks_ like the sign for addition. Furthermore, meaning as an after-effect of past observations must be _reproduced_ and reproduction presupposes reproducing factors in the actual situation. Obviously, then, if we do not see the distances, the oblique positions and the degrees of illumination, no reproduction of the “normal” size, form and brightness will be possible. It is precisely this which happens when the given objects are observed through holes in a screen: since, under these conditions, the surroundings of the objects and, with them, their _actual_ distance, position and illumination are excluded from vision, corresponding reproductions are made impossible. The objects must now be experienced exactly as, in pure sensation, they have been the whole time. The same proof is given by introspection. In our terms this procedure means an isolation of local size, form and brightness from their context in an actual situation. Thus it separates them from the factors determining the reproduction of “meanings,” and under these conditions of isolation the effect is that of pure sensation determined by the actual stimulation.

If in the case of size and form, after-images show a surprising variation with the relative distance and position of the background, this also is a direct consequence of our explanation. After-images are localized upon the background. If the distance and the position of this background operate as factors of reproduction, as in the previous case, the same after-image will take on a great many apparently different sizes and forms, relative to the changes of the background in distance and position.

Finally, in terms of our explanation we can understand why, under extreme conditions, there is no “constancy of size,” etc. Ten yards away a man is scarcely smaller than at a distance of five yards; but fifty yards off he looks smaller, and 1,000 yards away he usually becomes a tiny object, indeed. During most of our life we are interested in objects rather near to us; so we learn little about things far off and the consequence is that with increasing distance the relation between the true sensory experience and the meaning changes, to the advantage of the former. In all these arguments there is great persuasive force and cogency. Most psychologists do not for a moment doubt the truth of the explanation in terms of “meaning.” It also seems to correspond to a very natural tendency in human thinking. Physicists who have never studied psychology will tend to give the same explanation, as soon as they become acquainted with the facts we are considering. And if you demonstrate the phenomena to a freshman, he will give the “meaning theory” at once.

The importance of this theory is not less considerable on this account. There is practically no field of vision which does not exhibit some of the facts we are discussing. When we open our eyes we behold sizes, forms and brightnesses, and, of these appearances, only a very few will be exempted from the verdict which, from the viewpoint of introspection, must be imposed upon them. The facts themselves are not exceptional; only the demonstration of their surprising deviation from what one should expect them to be is something unusual. This demonstration is a matter of psychological, one might almost say, of laboratory, sophistication; the facts themselves are affairs of every moment and of everybody.

Though the extent of objective experience which shall not be trusted thus increases in scope, we have not yet reached its limits. The simple localization of objects manifests similar properties. Looking at a point before me I see the objects around it in different places, corresponding to the different places which their images occupy on my retina. If I now fixate another point, the same objects ought to appear in other places according to the new positions of their retinal images. But actually the objects do not seem to have moved. Their localization in space is again relatively independent of retinal position. Or take the speed of seen movement: the same physical movement may be seen from many different distances. When I am ten yards away from the moving object, retinal speed will be one-half of what it is at a distance of five yards. In direct experience, however, there is no appreciable difference of speed between the two cases of movement.[12] Obviously, the same explanation can be given here which has heretofore been applied to the constancy of size, form and brightness. Once more we are dealing with meaning. And ultimately we recall that first illustration, and indeed the most general case of the illusory character of direct experience: if we seem to perceive “objects” in our visual field, even those “objects,” from the standpoint of introspection, must also be products of learning: _meaning transforms sensations into “things.”_[13]

From this it follows that of all objective experience, as both layman and psychologist enjoy it in the visual field of everyday life, very little is left as pure and genuine sensory fact. That such is the consequence we must accept, if we go the ways of introspectionism, will become clearer to us now at every step.

Introspection, however, draws a much more serious conclusion from the foregoing analysis. Not only shall all those experiences which are supposed to be influenced by meaning not be treated as primary sensory experiences; but, in addition, they shall be excluded from the subject-matter of psychology. Some introspectionists may hesitate to acknowledge explicitly such a radical principle, but in their researches most of them proceed as though they had completely accepted it. After they have classified a given experience as one that must be explained by the effects of meaning, they rest satisfied, and are no longer any more interested in it than if it were found to belong to astronomy. This means that most objective experience is excluded from the introspectionist’s psychology as soon as he has found it susceptible to his explanation in terms of meaning. In the following chapters we shall see that wherever we touch upon a somewhat unusual and therefore interesting observation, the introspectionist will offer us this same explanation, and we shall always be urged to _discard_ the observation because meaning is involved. Whether the explanation is right or wrong, we continually face in common life the kind of first-hand objective experience which is discarded by introspectionism. Toward it all our interests are directed. There are millions of people who will never transform the “objects” of their environments into “true” sensations, who will always react to sizes, brightnesses and speeds as they find them naïvely, who will like and dislike forms as they appear to them in their objective world without recourse to introspection, and what are held to be the true sensory facts will never play an appreciable rôle in their lives. As long as the introspectionist’s attitude prevails, however, psychology will never seriously study those experiences which form the matrix of our whole life. Instead, it will observe and discuss the properties of rare and unusual experiences which, though they are supposed to be continually present beneath our naïve experiences, seem to be so well hidden most of the time that their existence has nothing to do with life as we actually experience it. Even the best introspectionist will not find or state these experiences unless he assumes the special attitude which--fortunately for him--he does not assume except in the laboratory. The enterprise of psychological observation is thus undertaken, removed so far from common experience, that if we should ever learn the laws of pure sensory process, all of them together would not lead us back to the psychological world we live in; because this world is one of direct and naïve experience, and utterly foreign to these laws of pure sensory process. If, therefore, the introspectionist’s psychology does not treat the facts we have to deal with in life, if most of these facts are exiled from his science, he cannot complain about his own fate. It is only to be expected that such a psychology would not satisfy people for long. If you condemn interest in the experience of daily life and define genuine experience as a rare something only found by artificial procedure, it is inevitable that your professional as well as your lay audience will tell you that they do not care for your kind of psychology. And they will not stop there. Since you have asserted that your experience is the only genuine one, they will interpret your procedure as the only possible scientific approach to the problems of experience. Thus they will condemn _all_ direct experience as material of psychology, after you have given away the greater part of it for the artefacts of sophisticated and sterile introspection. This reaction had to come. It has come in the form of behaviorism.

I do not feel justified in calling those artefacts _unreal_. When I apply the introspectionist’s methods I myself can get those special experiences which corroborate his findings. But I do not attribute to them a rare value as though they were worth more, as though they were more “true” than everyday experience. If that common experience involves meaning, the experiences given by introspection depend upon the attitude of introspecting and cannot be shown to exist without it, as we shall see later on. Moreover, for actual life, common experience is found to be incalculably more important than any of the introspectionist’s “true sensations.” Let us grant for a moment that all the facts mentioned above are what they are for us because of the influence of meaning. Do they become less real or less significant psychologically because of this genesis? Is a certain amount of H_{2}O which I have before me no real chemical substance because I know that it has been formed by the oxidation of hydrogen? Would that hydrogen be a “true” chemical substance, but not the water? Is the water not worth the chemist’s investigation? I do not see why an experience which contains acquired meaning should be less interesting and important for psychology than experiences not so composed. Take the case of the symbol +, which every one will agree is a product of meaning. When seen between figures it _looks_ like “plus,” i.e., _its meaning appears localized in the visual field_. A strange fact, indeed, which may entail some very important questions! Why should such problems not be investigated in psychology? It is the same situation with regard to all the other cases which are explained by meaning. Why should we lose our interest in the problems they engender, because the fatal word “meaning” has been uttered?

Furthermore there is positive reason why, instead, we should examine these problems with particular attention. We have to discriminate between two types of cases among the examples considered. One, represented by the symbol +, is distinguished by the fact that child psychology offers an adequate account of the growth of meaning in this concrete case. For the second type, represented by most of the other cases, such an account has not yet been given. It has been in no way demonstrated that the objectivity of things, the localization of weights, the constancy of size, form, speed, localization and brightness, the variation of after-images, and so forth, are really produced by the influence of meaning. It may seem extremely plausible to most of us that such is the case, but none of the experiments and observations I have mentioned in this connection can be regarded by an unprejudiced psychologist as satisfactory proof. In our present situation it is merely an hypothesis that the second group of facts quite properly belongs together with the first class, and as an hypothesis it is to be treated.

The customary thing to do with an hypothesis is to test it. Does introspectionism test this hypothesis? Quite the contrary, since all interest in the experiences which it is intended to explain, is destroyed for the introspectionist by the explanation itself. Thus we have before us an assumption which would never be examined at all, if all psychologists were extreme introspectionists. If this be strange, it becomes the more surprising when you realize that at this point most psychologists would not listen calmly to our discussion of “meaning theory” as an hypothesis. At first they might express only an incredulous smile, as though they had been asked to believe something fantastical; but if you insisted upon this point they would grow impatient, because in their opinion you were disturbing the sound basis of careful science by an obtrusive paradox.

When a scientific argument tends to become rather emotional it undoubtedly prods some deep-rooted presupposition, the discussion of which is felt to be offensive. No one enjoys the discussion of what for him is secure beyond discussion. In the face of this exhibition of temper, the more calmly should we realize that the attitude of introspectionism, if taken so piously, becomes a real danger. Let us suppose for a moment that in the cases of objectivity, size, form, speed, localization, brightness, etc., the explanation by meaning is incorrect. We should then immediately draw the conclusion that all the facts in question are a part of genuine sensory experience. But these facts would tell quite a different story about sensory experience than that given by the introspectionists. Hence it would follow that what we learn about “true” sensations from them has to be regarded as distorted truth. Whether or not this be really the case, depends therefore upon the validity of the general explanation by meaning. And this explanation is not to be tested; it _shall_ not even be examined! It will be obvious then that, used by the introspectionist in this manner, _the meaning theory serves as a defensive bulwark for his quite definite and special ideas about sensory facts_.

This makes us suspicious of the meaning theory. Introspectionists may be so utterly convinced of it, not because independently it is particularly attractive in itself, but because their prior firm belief about the nature of sensory facts will not permit them to acknowledge certain experiences. If these “irregular” experiences can be explained away by meaning, the belief will be reassured.

In order to show that such is the case, we have only to consider the arguments brought forward in favor of the meaning theory. They have little indeed to do with meaning, but very much with convictions about the world of pure sensory experience.

Take the “constancy of brightness” as an example. A white paper in the shadow appears as white, a black one in bright illumination as black, though the white may reflect less light actually than the black. Is there anything in this experience, in the white and the black _as such_, which tells us directly that we have to do with an effect of meaning? Nothing at all. The argument is of an indirect kind, viz., our observation in this case cannot be reduced to “pure sensation”; it must, therefore, be a product of meaning.

First of all, one can _change_ the experience by looking at the papers in a special manner. Therefore, it is not a true sensory experience. A primitive conviction, then, which paradoxically both needs and supports the meaning theory is this: _True sensory facts are independent of changes in subjective attitude_. Evidently, however, such a statement is not a sufficient support of the theory. If, in the attitude of introspection, I can transform the apparent white into a dark shade, and the apparent black into a rather bright nuance, the opposite change will occur spontaneously as soon as I forsake that attitude and behold the papers as other people do. From the viewpoint of experience the “true” brightnesses, appearing during the period of my experimental attitude, are as changeable, then, as those which I had before and which I customarily have. Logically, I might as well condemn the experiences found during “introspection” and refuse to call them “true,” because they disappear whenever I return to the everyday attitude. The introspectionist, however, is far from treating both experiences with the same measure. He thinks that what he experiences in his special manner is true experience, that, hidden somehow, it ever exists behind the veil of meaning whenever he falls back into a more naïve attitude. Thus it becomes clear that there is still another belief which makes him prefer his special and rare experiences.

His other belief is easy to find. Why should we be surprised by all these observations on size, form, localization, speed, brightness, etc.? Why not take them quietly and as a matter of course? Obviously, because under the given experimental conditions of stimulation we expect to have experiences quite different from those which we really have. Naturally, we say, seen size should be proportional to retinal size, to changes in retinal form there should correspond changes in seen form, localization in the visual field should vary with retinal localization, seen speed with retinal speed, and seen brightness should follow the variations of retinal intensity. While the everyday experience of the layman contradicts these expectations in the most shocking manner, the special attitude cultivated by introspectionism succeeds in obtaining precisely those other experiences which, according to the introspectionist, we ought “naturally” to have always; or we at least _approach_ that state of affairs which our understanding considers the appropriate one. _This_ is the fact which makes the introspectionist prefer the special and rare experiences found by an artificial attitude, and which also makes him believe in a permanent, though hidden, existence of these “pure sensations” under the opaque cover of naïve experience. It becomes apparent, then, that the procedure and the results of introspection acquire a special sanction through their agreement with definite presuppositions about the relation between stimulation and sensory experience. The same suppositions lead to the condemnation of everyday experience. No one can understand the scientific trend of introspectionism who has not discovered, who does not see, this decisive point. How many times, as a student, have I read and heard that the Müller-Lyer phenomenon does not represent a “true” sensory fact, because by analytical observation and practice we can destroy the “illusion”! If this be taken as a proof, obviously one kind of experience is given a _higher value_ than another. If you ask, why? you will ultimately get no other reason than the one already stated: that one experience agrees with the properties of peripheral stimulation whereas the other does not. Those that do not are discarded with the aid of the meaning theory.

A second fundamental conviction, then, underlying this theory and the whole scientific viewpoint of introspectionism is this: _The main properties of “true” sensory experiences follow the corresponding properties of peripheral stimulation._

The introspectionist’s belief takes a form still more concrete. How did he proceed in order to find the true sensory facts in the case of brightness, for instance? He tried to isolate the white and the black paper under observation so that they were taken out of their context as far as possible. The same thing is done by those who try to destroy the Müller-Lyer illusion, and similarly in all the other cases. Such an analytical and isolating attitude will have effects similar to those of a perforated screen, which, concealing the particular surroundings of the objects, gives them a new _homogeneous_ environment. If now the “illusions” disappear, this effect of isolation is explained in terms of the exclusion of all those secondary factors, and in particular meaning, which before had distorted the true sensory experience. But the possibilities of pertinent explanation are not exhausted with this. The effect produced by isolation proves at least that objective experience in one part of the field does not develop, independently of its neighborhood, as a function of local stimulation alone. If this be taken as a description of facts, we may explain the facts in one of two ways: (1) _Either_ “true” experience depends upon local stimulation exclusively, whereas the meaning which almost always adheres to it depends upon (is reproduced by) the properties of the environing field; (2) _Or_ natural sensory experience _itself_ is not determined locally; i.e., the properties of any one part of the field depend normally upon the conditions given in the whole field, or, at least, in a larger area of it. In _both_ cases isolation, or the introduction of a homogeneous environment, would make local experience correspond better to local stimulation. The introspectionist, however, does not consider the alternative. He only seems to see that one horn of the dilemma, according to which isolation gives the “true” sensation, and naïve experience is a product of meaning. Again we find him partial to an astounding degree; he _prefers_ that hypothesis (although unwilling to regard it _as such_) which gives him local sensory facts determined by local stimulation. In a well-known example, when our subjects make eye-movements along the main lines of the Müller-Lyer figures, these movements are shown to have different extents for the two figures, corresponding to the difference of their apparent lengths. There you have it, we are told! The illusion is not an optical fact; it is produced by the accompanying motor phenomena, or at least by innervation tendencies if overt movements do not occur. This is an altogether partial statement because, supposing that the two lines _have_ different lengths in “true” vision, nothing would be more natural than that the eye-movements should be different correspondingly. Only by prejudice can the fact in question be interpreted as though it proved the indirect genesis of the Müller-Lyer effect. It may prove instead that sensory experience is influenced by stimulation in a larger area and that, therefore, eye-movements, depending upon sensory experience, will also vary when surroundings are changed.

Recapitulating the foregoing analysis, we may conclude that: _A decisive motive in introspectionism is the belief that true sensations are independent of subjective attitude and depend only upon local stimulation as purely local experiences._[14] This is the only rule which helps us to understand on what occasions the introspectionist begins to introspect. Very seldom will you find him introspecting where, without any technique, he obtains certain simple relations between local stimulation and experience. But where these relations do not seem to exist _prima vista_, you will find him taking recourse simultaneously to the introspective procedure and to the theory of meaning.

Here is the remarkable result of our inquiry. The whole procedure of present introspectionism seems at first to be in full contrast to behaviorism’s purely physiological viewpoint. If the introspectionist is not the advocate of direct experience, who else should be able to play that rôle? But we have found that there is some restriction upon his enthusiasm for direct experience. A foreign judge has the chair. He examines direct experience beforehand, convicts most of it, and sends it away for correction by a special procedure. This judge is a _physiologist!_ His ideas about the sensory part of the nervous system are extremely definite. When the introspectionist mentions physiology, he seems to talk about a helpful servant; but when we look at the facts, the servant rules the introspectionist.

If introspectionism is much less guided by direct experience than by definite physiological principles which decide what shall be called “true” sensations, its viewpoint is not so very far from that of behaviorism. And this similarity of general ideas becomes even more striking if we compare in detail the physiological creed of introspectionism with that of behaviorism.

The main concepts of behaviorism are those of reflex and conditioned reflex. What is the characteristic trait of reflex action? That from a definite receptor organ nervous excitation is conducted along a definite path, through definite “centers” and along other definite paths towards a definite effector organ. The _order_ of organic reactions in their dependence upon definite stimulation is explained by this conception: a preëxisting arrangement of more or less isolated conductors enforces that order. It is true that behaviorists do not suppose the anatomical arrangements to be _absolutely_ rigid and constant. But, though a certain “irradiation” of excitation is admitted, almost the only biological value attributed to this plasticity consists in the fact that, if some other factor can make the connections practically rigid, this other factor will have a certain range of different possibilities to work upon. Hence, order of functions is enforced fundamentally in the reflex arc, but, at a higher level of the nervous system, connections may be built (or blocked) by another factor. This other factor is “conditioning.”

If now we consider the definite physiological ideas which silently determine introspectionism’s criteria for “true” sensory experience, we find the following two: _First_, local sensation depends upon local stimulation; it does not depend upon other processes in the nervous system, not even upon those issuing from neighboring points in the same sense organ. There is only one physiological assumption which would explain such an independence of local sensation, namely isolated conduction from one point of the sense organ toward one point of that region the activity of which is accompanied by sensory experience. This, however, is nothing but the first half of a reflex arc, so that in this respect introspectionism agrees completely with behaviorism. If experience does not seem to obey this principle universally, that is because we have a _second_ principle: At a higher level of the nervous system at least, connections may be built during development, which did not exist originally at birth. A corollary of this principle is: that certain experiences will be followed and accompanied by others, or by reproduced material corresponding to them, in the form of “meaning.” Though this term sounds a trifle more refined than “conditioning,” in the physiological considerations of most introspectionists it means the automatic formation of new conducting connections, just as conditioning does for behaviorists. Again there is no real difference between the one viewpoint and the other.

During their lively controversy over whether introspection, or the objective observation of behavior, is the true procedure, it does not occur to either party that some other theme might be more important and urgent, namely, that concerning their common convictions as to the basic type of nervous process underlying experience or behavior. This assumed basis appears self-evident to both of them. And since so much is taken for granted by both, we should not be surprised to find the same conservatism in introspectionism which is so striking in behaviorism.

That psychology is a very young science and that therefore its future and its progress will probably depend upon discoveries unsuspected at the present time, seems not to be realized by most introspectionists. In sensory experience, at least, the essential traits of all possible and acceptable observations are fixed for them before they begin to observe. Consequently, they show an almost negativistic attitude whenever an observation does not agree with that preëstablished truth; and their experimentation tends to become a rather defensive and critical procedure. If others point to some new observation that does not exactly conform to the fundamental concepts mentioned above, they are eager to quell the disturbance, and to dismiss it by appropriate introspection and discussion. I admit that criticism of new observations is a healthy procedure in science; yet I have known introspectionists who spend their scientific lives in a critical defense of what they believe to be unquestionably true. In these circumstances one cannot expect them to have a youthful interest in free observation and naïve discovery. If the main points are already established, and if further observation cannot give us essentially new hints, why should we strain our eyes in the chaos of a large world behind which, anyway, the old truth _must_ be hidden everywhere? As William James would say, whatever happens is a “nothing else but” for them; it can be reduced to an old story. In this attitude again there is no real difference between behaviorism and introspectionism, though each defends its conservatism by different methods. But there is a real difference between preferring to be at rest upon preëstablished ground or preferring adventure and intellectual curiosity which take you full-sail into the open sea of experience. If you choose the latter, perplexity will be your usual feeling, and a glimpse of clear-shaped coasts a rare reward on some Sunday of research. But the next generation will have more Sundays as a result of your exploration. Certainly, neither this nor the next generation is needed in psychology, if we stay at home and know beforehand that no other sites can be found in the future.

I do not see, then, why introspectionism should be preferred to behaviorism, or vice versa. They are so much alike in their fundamental opinions and in their general attitudes, that all their wrangling seems like a family quarrel to the onlooker. And it is among precisely those themes, over which they do not quarrel, that we shall find the problems of _gestalt_ psychology. For the present, however, we shall pursue this question: Is it true that the processes underlying experience and behavior are determined mainly by the connections of given nerve-paths, and that some change in the conductivity of these connections is the secret of an individual’s development?

BIBLIOGRAPHY

M. Bentley: _The Field of Psychology_. 1924.

K. Koffka: _Gestalt Psychology_. The Psychological Bulletin. 1922.

D. Katz: _Die Erscheinungsweisen der Farben_. Ergänzungsband 7 der
Zeitschr. f. Psychol. 1911.

W. Köhler: _Uber unbemerkte Empfindungen und Urteilstäuschungen_.
Zeitschr. f. Psychol., 63. 1913.

W. Köhler: _Akustische Untersuchungen_ III. Zeitschr. f. Psychol.,
72. 1915.

IV

_Dynamics as Opposed to Machine Theory_

SOMETIMES people are conservative and right at the same time. Still it seems highly improbable that in our very young science conservative opinions should be right, opinions which are opposed to almost all experience, and which have scarcely been examined, because they have been protected by the “meaning theory.”

Some of the physiological presuppositions lurking behind introspection are hardly convincing if they are once examined critically. In one of our examples, apparent movement, produced by touching successively two different points on the subject’s skin, is not admitted as a “true” sensory fact because usually it forms a curve through empty space, only the ends of which are felt on the skin (cf. p. 79). But why should all the experiences which depend physiologically upon the stimulation of a sense organ be localized in the same place where that sense organ is localized as an experience? In vision, this is not the case; forms or colors are not seen at the place where we feel our eyes. Neither are sounds heard generally where we localize our ears. Behind the introspectionist’s argument there seems to be some primitive confusion of the peripheral processes produced by stimulation with sensory experiences depending upon them of the physiological locus of the first with the sensory localization of the second.

I think this case is typical because it shows that the apparent self-evidence of the argument from physiology prevents a critical consideration of it, whereas any examination of the case would efface the self-evidence of the assumption. In this chapter I shall try to show that even the main assumptions of introspective psychology and behaviorism are by no means axiomatic, though they agree with a common prejudice which is thousands of years old.

We have seen that those assumptions are utterly dependent upon the explanatory force of the meaning theory. Unprotected by this theory those assumptions would be destroyed by any observations which contradicted them. Recent experimental work on some of the experiences discussed as examples in the last chapter bears upon the explanation of those experiences in terms of meaning. In order to _learn_ that sometimes white is black and vice versa, an individual needs time and _much_ experience, largely because he has to learn it so thoroughly that finally the products of learning will be “projected” into his field of vision as definite nuances of brightness instead of the “true” ones. We should expect, then, that young or primitive subjects would not show the “constancy of brightness” to any considerable degree. But when the experiment was made with young chicks under very severe conditions, they were found to possess approximately as good a “constancy of brightness” as I do.[15] Similar experiments made on the “constancy of size” with children (from two years up), and with young apes, also gave positive results.[16] Though it is difficult to exclude slight influences of meaning upon the phenomena in question, it seems altogether unlikely, even without further work, that _in principle_ these phenomena are produced by meaning. I do not deny that objective experience is imbued with acquired meaning in many respects. But, as has been said before, where this influence is not demonstrated in the history of individuals, or somehow demonstrated independently, no indirect argument is strong enough to be accepted in lieu of such a demonstration.

Since in these instances the meaning theory begins to relinquish the field, a radical change in fundamental principles becomes unavoidable. The phenomena we have here discussed, such as constancy of size, form, localization, speed and brightness, the stroboscopic movement, the well-known illusions and so forth, become just as decisive in our understanding of genuine sensory experience as the so-called “normal” cases of introspection, i.e., as the observations that at a given distance and on a homogeneous background seen size depends mainly upon retinal size; that (apart from contrast and other exceptions) in a given illumination seen brightness depends upon retinal intensity, and so on. In these cases, usually regarded as normal, size, brightness, etc., are found to vary with the properties of local stimulation, because conditions of surrounding stimulation are practically constant. For the same reason, by assuming the introspective attitude, we may find experiences corresponding to local stimulation even in those other cases where _naïve_ experience shows the contrary, because by an analytical attitude the influence of surrounding conditions temporarily can be suppressed to a high degree.

But we do not suppose such isolation to be the normal state of affairs. If in all the examples given we accept direct experience at its face-value, our fundamental assumption about the processes underlying experience and behavior must be opposite to the assumptions of both introspectionists and behaviorists; i.e., instead of reacting to local stimuli by local and mutually independent events, the organism reacts to an actual _constellation_ of stimuli by a total process which, as a functional whole, is its response to the whole situation. This is the only viewpoint which can explain how to a given local stimulus there may correspond altogether different experiences as soon as surrounding stimulation is changed. We face this dilemma: _Either_ we take the traditional horn, in which case direct experience and everyday behavior are irrelevant to our psychological analysis, _or_ we trust all kinds of experience impartially, in which case we have to accept the suggested radical change in physiological theory.

“Total process” and “functional whole” are, however, terms which sound rather vague, or even mystical, to most scientists. It would be well to present our physiological assumption in more definite detail. This may be done. And at the same time we shall obtain a more general view of our problem if we ask ourselves just why the prevailing viewpoint should have appeared so utterly convincing to the last generations.

The chief reason seems to be that sensory experience is in most cases quite orderly, and that the behavior, which accompanies it, is no less orderly. Now since the early days of European science man has been deeply convinced that the processes of nature, if they are left to their own “blind” play, will never produce anything like order. Why should they? Does not the accidental intercourse of inorganic natural forces around us produce chaos and destruction everywhere? We have been able to formulate some of the rules according to which isolated processes occur in nature necessarily, but where many processes influence each other without control, no reason is apparent why confusion and general disorder should be avoided or why the whole complex should develop toward an orderly distribution. _Without control_--this appears to me to be the decisive point. For as soon as man began to restrict the possibilities of natural processes by appropriate rigid arrangements, the same forces which apparently would have produced chaos, destruction or disorder without control were guided toward orderly function in the service of mankind. This has been man’s conception of nature for thousands of years; in modern times the engineer still enforces in the same manner the functional order in his machines. The “blind” forces of nature are allowed to make the machines _move_, but the _order_ of the movement is enforced by those special arrangements which are the essential traits of the machines and the pride of their inventors.

From this viewpoint, which prevails even in current theory, a young science will tend to presuppose the existence of “special arrangements” wherever the distribution of forces or processes in nature is found to be orderly. Aristotelian astronomy is a good example. The movements of stars in the sky maintain a remarkable order, so different from what one would expect to occur in “free” nature, that something special must control those celestial events. Obviously, the possibility of a star running wild or a planet going astray must be excluded by rigid arrangements. Therefore, in Aristotelian theory, the stars are fixed upon those famous crystal spheres, the turning of which forces the stars to move in their apparently regular orbits. There are even engineers, viz., the stellar deities, who watch and control the machinery. Three hundred years ago this conception was still entertained in pious awe. The functional value of its crystal spheres in the orderly sky, however, was precisely the same as that of any rigid arrangement enforcing orderly processes in our machines. There is a deep longing for rest and safety in man. Early in history it was satisfied by such a primitive belief, the content of which may appear crude, narrow and absurd to modern eyes. What was so shocking in Galileo’s astronomical discoveries? That there was so much going on in the sky and the astronomical order was so much less definite than one could happily believe before! If the heavens begin to show a lack of rigid institutions, similar to the flexibilities we observe on this planet, who can feel secure in his most important beliefs? There was much exceedingly human, miserable fear in the furious attacks directed against Galileo by the Aristotelians of his time, and the fear was evoked by the amount of change and dynamics Galileo found in the world as the home of mankind. One may well suppose that the excitement produced by Harvey’s discovery of the circulation of the blood contained a similar element of fear, because the conception of man as a rigid structure was suddenly disturbed by the idea of internal unrest, accompanied by the possibility of its fatal cessation at any moment.

In any case the same general motive expresses itself in the well-known tendency of early biological thought to explain all remarkable properties of organic life, and most of all its orderly course, by special arrangements enforcing order. In the time of Descartes, his so-called mechanical interpretation of organic functions may have been bold enough; still he was absolutely conservative in assuming without a moment’s hesitation that--apart from the influence of one engineer, the soul--all delicate, vital processes were enforced by special arrangements, connections and channels throughout the whole body of man. Figuratively, the organism was for him what the sky had been for Aristotle--full of crystal spheres. He did not know the laws of dynamics, it is true. But though we know much more about them since his time, the main changes in biological theory seem to have been refinements of his type of thinking rather than discoveries of new general concepts about organic order. Even in our own day, though doubting the validity of that machine-conception as a satisfactory explanation of _all_ organic order, biologists do not give us any other clear general principle whereby to understand the orderliness of organic function.

We shall see at once what the possibilities of alternative explanation are, if we try to get a more concrete picture of the characteristic trait in Aristotelian and biological machine theory.

In physical processes we find two sorts of factors determining events at every moment. In the first class belong the actual forces of the process itself; they represent the _dynamical_ side of it. In the second class we have those properties of the system which may be regarded as _constant conditions_ of its events. So, at the present time, the elementary charge of one electron seems to be an unchangeable condition of all physical events. In a conducting wire the specific conductivity of its material will be regarded as such a given condition. On the other hand, the electrostatic forces of the current itself driving an electron along that wire are an example of a dynamical factor. But among the constant conditions two further classes may be discriminated. In the case of electric current it is one given condition that all moving charges have the amount of electronic charge or multiples of it. Another condition of the current is given by the mode of the distribution, the connections and the spatial order of the conducting material, i.e., a network of wires.

Immediately the fact becomes clear that, whereas in all systems of nature, in addition to their own dynamical forces, processes depend upon conditions of the first class, the influence of special conditions of the second class may dominate in one case and be at a minimum in another. When we consider the play of electrons in an atom or the integration of atoms forming a molecule, we do not find a special topography laid down beforehand which determines those processes. At every moment, in addition to constant properties of the material (first class of conditions), the actual _dynamical_ situation develops the next event out of itself. If we wish to refer to the second class of conditions in such a case, it would be to point out that the topographical situation consists of physical space without any special determining or limiting feature in it. On the other hand, the equilibrated distribution of electric charge on the surface of a conductor depends upon the rigidly given form of that conductor as a limiting topographical condition; and in a steam-engine the piston can move only one definite way, determined by the rigid walls of the cylinder.