Chapter V: Part 5

But the reader says: Of course, you are somehow talking about realities. Still, something may be real psychologically without belonging to sensory experience proper. How can you forget for a moment that a piece of paper, a pencil, a cigarette, are objects known by use! You have handled them during many years and so you had more opportunity than you needed for learning that they _behave_ practically as units. This previous experience being projected into your field of vision, why do you lay so much stress upon a simple fact which is widely known and well explained, and which has been accounted for ever since, or probably even before, Aristotle wrote his textbook of psychology. My answer will be more extensive than this argument. Until we are able to prevent such superficial applications of the meaning principle, there can be little agreement about the most elementary problems of _gestalt_ psychology. Who in the world would deny that a piece of paper, a pencil, and so on, are well-known objects? That I know their uses and their names by previous experience and that hence they are full of “meaning,” shall also be granted without hesitation. But from these facts there is a large step to the statement that neither the paper nor the pencil would exist _as segregated units_ in my visual field without that previous knowledge about their practical behavior and use. It may be that before I had that knowledge the same things occurred in the sensory field as units, unknown and unnamed, but still as segregated wholes. When I see a _green_ object, I can tell the name of the color immediately; furthermore I know that green is used as a signal on railroad tracks and also as a symbol of hope. But I do not believe that, therefore, the color green _as such_ must be explained by meaning. Existing independently it has acquired several secondary properties in my lifetime and I agree with the reader in praising all the advantages which this kind of learning holds for all of us. In exactly the same manner, sensory units may have acquired names and may have become richly symbolic in the context of our knowledge, while existing, nevertheless, as segregated units in the sensory field prior to such accretions. Such is the conception which _gestalt_ psychology offers to defend. It even goes so far as to hold that it is precisely the original organization and segregation of circumscribed wholes which make it possible for the sensory world to appear so utterly imbued with meaning to the adult, because, in its gradual entrance into the sensory field, meaning follows the lines drawn by natural organization. It usually enters into segregated wholes.

If the explanation by meaning were correct, wholes should be segregated in the field only insofar as they are recognized as definite known objects. But this is not the case. Looking into a dark corner or walking through mist in the evening, the reader will frequently have found before him an unknown something, detached from its environment as one whole, the use or the meaning of which he did not discover until after a more detailed observation. Walking through an unknown country at night, I have often had such an unrecognized whole in the field for several minutes. It is evident to me, therefore, that my knowledge about the practical behavior of things does not determine their existence as detached units. The same argument may be restated in a more general form. Whenever we say to ourselves or others: Now, look here! What may that something there be, at the foot of that hill, just to the right of the next tree, between those two houses, and so on?--we ask about the meaning or the use of that something, demonstrating by our very question that segregation is independent of knowledge and meaning. As, in physics, a molecule is segregated as a functional unit, so definite wholes seem to be dynamically detached in the sensory field.

But so fond are we of our empiristic convictions that, in this predicament, the explanation by meaning will immediately assume another form. Your unknown whole, seen in the mist, so the reader will say, appears as something separate, because it is darker, for instance, than the gray mist around. I admit that no _special_ knowledge about this definite group of sensations, as meaning a particular object through past experience, is needed for unifying and segregating it. But you under-rate the wonderful achievements of previous experience if you restrict its effects to particular cases. We have always observed that a set of adjacent sensations, possessing almost the same quality, different from that of the environment, “behave together,” i.e., move and are moved, appear and disappear, at the same time. This is the case with stones, with papers, with hats, with boots, with many animals, with leaves. As physical objects they are bound together, so that physically they move as units. It is only one example of the well-known generalizing power of memory if now we treat as units and even believe we _see_ as units _all_ groups of adjacent sensations which are more or less homogeneously colored and sufficiently different from their surroundings. So we must not be astonished by the fact that, in the mist for instance, an area of darker nuance is seen as one individual something, though we may be unable to tell its _special_ use or meaning.

I am not satisfied, however, by this form of the theory either. Units are formed and segregated in the field in a great many cases where this rather bold explanation does not apply. Take all units consisting of separate parts! If we look up at the sky on a clear night, some constellations of stars are seen immediately as belonging together and as detached from their environment. Cassiopeia is an example, the Dipper is another. In past ages people saw the same groups as belonging together and at the present time children do not need instruction in order to perceive them as units. In Fig. 1 the reader has before him two definite groups of patches. Why not merely six patches? Or two other groups? Or three groups of two members each? Looking passively at the figure every one beholds those particular groups in the field, two units being segregated, each containing three definite patches. What about generalized meaning in these cases? No previous experience could separate Cassiopeia from the other fixed stars around it. As far as everyday experience goes, they all move together. And no hint at the generalizing properties of memory will help here. We cannot possibly assert that we have _learnt_ to see a number of separate patches, similar to each other and different from the environment, as one thing or one group, because they move together regularly. They are very far from doing that. On the desk in my room are sitting five flies which are five black dots as I see them from where I am. These dots begin to move separately and to move in different directions. So do three yellow leaves which a breeze lifts from the ground separately; so again three stones which my hand moves, one after the other. My general experience is that, at least as often as not, similar members of a group, which are separated by the common background, are movable and move _independently_. If, nevertheless, in this case definite groups are formed and segregated, this happens despite our general previous knowledge about the behavior of their members.

Investigating _which_ separate “patches” tend to become included in one group, we find that, among other factors, their equality or similarity and their common difference from other “patches,” favor their becoming grouped together and their segregation from others. So we see that in the case of separate members the same rule holds, without the influence of meaning, which was said to explain unknown _continuous_ wholes under the influence of generalized previous knowledge (cf. p. 153). Consequently, in this latter case, the indirect genesis of groupings through previous experience is not needed any more than it is where separate members form groups. The grouping of separate members is used in one of our tests for color-blindness: A rectangular field is filled with dots at equal distances from each other. For the normal eye certain groups of them belong together and are seen segregated from the rest at once, and since these groups form written numbers, normal persons will read the numbers without difficulty. The dots in question have similar chroma and are sufficiently different from the others to appear as one group which, as a whole, is recognized immediately. But for those color-blind people who do not perceive the given differences of chroma, no group will be segregated spontaneously, so that they do not see and cannot read the numbers. In this example, the general acquaintance with numbers is the same for both normal and color-blind subjects. Therefore, the striking difference as to grouping depends directly upon sensory conditions.

Groups consisting of separate members have a special interest for theory insofar as they also prove that one unit segregated in the field may at the same time belong to a larger unit. One dot in our last example represents a continuous detached area; still it is a member of a larger whole, the number, which as a larger unit is again segregated in the whole field. There is nothing peculiar or mystical in such a subordination, since, in physics, a molecule as a larger functional whole contains several atoms as subordinate wholes. The atoms belong to the molecule functionally; still they do not altogether lose their functional individuality in that dynamical whole.

Following the casual observations of others, Wertheimer was the first to see the fundamental importance of spontaneous grouping in sensory fields and to demonstrate, by a great many examples, the main principles upon which it depends. Most of his illustrations entail the grouping of separate dots or lines, because, by using meaningless constellations in this manner, it is easier to guard the demonstration against disturbing arguments and criticism in terms of previous knowledge. He has pointed out most clearly, however, that the same principles may hold for all formation and segregation of wholes. I do not know a better introduction to these problems than is given by Wertheimer’s paper of 1923.[26] The reader is asked to make himself acquainted with them by studying it. Some of the principles are easy to understand. We have already considered one of them, which claims that the equal and the similar tend to form units separated from what is dissimilar to them. Where we have no differences of quality, or other properties, among the members, relative distance will often be decisive. In one of our examples _two_ groups (of three members each) are formed, because among the six patches some distances are small as compared with others, those patches, the distances separating which are relatively small, belonging together in one group. In some cases, perhaps the most interesting ones, it seems more natural to define the rule of grouping not by given conditions, but by the tendency toward certain results. As the physicist is accustomed to say that surface tension works in the line of reduction of surface, so in the sensory field grouping will produce certain wholes rather than others. We may say that simple and regular wholes, or closed areas, are formed more easily and more generally than irregular, or “broken,” and open wholes. It becomes evident here that, in contrast to the indifferent mosaic of sensations assumed in older theory, this order of the field shows a strong “predilection” for certain general kinds of organization as against others, exactly as the formation of molecules and the working of surface forces in physics operates in certain definite directions.[27]

Recently the nature of grouping as a sensory and elementary fact has been demonstrated in the most convincing manner by experiments which Hertz has made on birds (_Garrulus glandarius_).[28] A number of little flower-pots are put upon the ground upside down. If the rather tame bird, sitting high up on a branch, sees that the experimenter puts some food under one of the pots, he will come down very soon, lift the pot and take the food. This is a simple form of “delayed reaction” as Hunter investigated it years ago. In these experiments, however, the main point was not the _delay_ of reaction as such, but its dependence upon the actual constitution of the field. The bird reacts without difficulty if there is one pot only. But when there is more than one everything depends upon whether the “right” pot in some way stands out from the rest in the aggregate. If it is put in a regular line with the others so that, for human vision, it becomes absorbed as one indifferent member in a series, the bird lifts one pot or another in a haphazard way, even if the distances between them are as large as 25 cm. As soon, however, as, by grouping, the right pot becomes something strikingly apart, i.e., segregated from the rest for the human observer, the bird selects the right object at once. So in the case of Fig. 2, in which the right pot is physically only 10 cm. apart from a straight line of other pots, it is chosen at once. Obviously, here, the line of other pots is a well-bound whole and the one pot a segregated thing by itself for the bird as it is for man. Even in the situation of Fig. 3, where the right object is 6 cm. from the next and this 2 cm. from the last, grouping is definite enough to allow an accurate reaction. But in the case of Fig. 4, where the right object is 3 cm. apart from the next and this 2 cm. from the last, reactions become a matter of chance. The bird cannot keep the right pot apart before reacting, unless definite grouping helps him to do so. If the grouping is very well determined for man, however, the bird will have no difficulties at all, though the right object may be in immediate contact with its next neighbor. In the situation of Fig. 5, 12 pots are arranged so that they form a closed ellipse for human vision. The right pot is put close to one of the other twelve. The human observer will have before him one closed whole and one object outside. The bird chooses the right one at once. This example seems to me particularly valuable, because it shows that single objective distances as such are not decisive, but rather the grouping which results from the _total_ constellation. How Hertz was able to demonstrate similar effects by the application of other principles, as, for instance, differences in size or chroma, may be better appreciated by reading the original paper. To me these experiments seem to open an altogether new field of research in animal psychology, providing we give up our somewhat conservative and negativistic mood in this branch of science, and begin to believe in the possibility of new problems. But as that negativism has not yet disappeared completely, I should remark that, if grouping is demonstrated in these birds as a “sensory fact,” it does not imply “consciousness” in the animals. From our viewpoint, it is true, this does not matter very much (cf. above Chapter II). One thing is proved, however, that grouping occurs in sensory processes.

By further experimentation it must be possible to find out how far birds and other animals see _continuous_ wholes, segregated in the field, as man does; though even now it would be difficult to understand the behavior of those birds, and their reactions to grouping, if the pots themselves were not detached units in their field. In any case the elementary nature of continuous wholes is demonstrated by certain observations on the first reactions of congenitally blind persons after they have been operated upon. Generally, the problems most interesting to the ophthalmologist in those cases are those of visual depth and of an original similarity between forms in vision and forms in touch. Results have been discussed in several ways, but in most of the cases one side of the observed facts is not given adequate attention. It is generally true that when the patient is asked about an object, known by touch from previous life, but given him the first time optically and without the help of touch, there is no satisfactory answer; with a very few exceptions the patient does not recognize those forms directly. Still there is something very positive in his reactions: When asked about “that something” which he has before him, _he understands the question_. Obviously he has before him some thing as a segregated unit, to which he refers the question and which he tries to name. At least, if the object is a simple and compact form, the patient does not have to _learn_ what “aggregate of sensations” he shall “treat as one thing.” Thus elementary organization is an original sensory fact.

In Wertheimer’s paper on sensory grouping one finds the same problem discussed in the case of wholes of a somewhat different sort. As we experience _time_, it has some properties in common with space, particularly with one dimension of it, namely its sagittal axis with man as the center. Therefore, words referring to relations on this axis are used as terms for temporal relations everywhere and in all languages. In English we have something “before” or “behind” us in both meanings; we look “forward” in space as in time, and death will come “nearer” in time, as one place is nearer to me in space than another. Perhaps, physiologically, there is a corresponding similarity between the two, because, with respect to the organization and segregation of extended units, we find the same general principles determining temporal order which are known to us from the visual field in a state of rest. By approaching my hand now and then for two-second intervals to the opening of an organ pipe which is sounding continually, I can lower the pitch slightly. In hearing, the effect will be a segregation of the corresponding number of auditory units, the constant tone appearing as general background and the somewhat different notes as so many “patches” singled out from it. Of course, there are no such units in the physical stimulation. Physically we have thousands of waves of equal or different wave-length, all of them following each other indifferently. It hardly needs to be mentioned that in the same manner an appropriate succession of visual stimuli will be found to result in temporal unification and segregation. The same thing is true of touch and other senses. Again, “temporal dots” will readily form “temporal groups” in all these cases, the groups containing the dots as subordinate units and so forth.

It is in these _groups_ that the principles of temporal organization are recognized most easily. With my finger I tap on the desk three times at very short intervals and, after waiting for a second, I repeat the tapping. People who hear this sequence for a while get groups in time. Physically each sound is indifferent to every other; they are independent events as the stars of Cassiopeia are practically independent. Logically, other forms of grouping are quite possible which do not occur, however, in the experience of an observer who is listening calmly. Therefore, the groups, as we observe them, represent an example of physiological or, if one likes, psychological organization. The principle determining it in this case is relative distance in time exactly as relative distance in space was a principle of grouping in the simultaneously presented visual field. If all the intervals are made equal, we still get groups when introducing differences of intensity or quality in the series, especially when the tapping is done according to a simple regular scheme. In temporal sequences equality or similarity plays the same rôle as against differences of properties, which we have found in the visual field.

In the most general case of sensory organization both space and time are involved in the same experience of grouping. A simple example will show what is meant: In a dark room we move a lamp hidden in a box, so that one bright point is the only thing visible on the dark ground. Let us suppose that the point moves in the following form without a change in speed: _vide_ Fig. 6. A naïve observer will describe what he has seen as three curious figures, or three movements (I, II, III); perhaps he will correct himself after a while and say that there were seven movements (1, I, 2, II, 3, III, 4). But he will not say that he saw 53 or 16 or 29 movements! Now, as applied to the number of optical stimuli which impinge serially upon his retinæ as quite independent events, there is no reason why one of the larger numbers should be less correct than three or seven. But, in experience, instead of an indifferent series we again find a definite product of organization. The reader will have realized already that with respect to a more complex experience such as I may have if I see some one “nodding twice” or “shaking his head a few times,” there is much in the experience that is not covered by our present discussion; but, neglecting the meaning of those particular movements, he will also realize that there is a sensory organization of the given movements into “two” or “a few” sub-wholes.

This seems to be an appropriate place to mention an indirect explanation of organization and grouping, preferred by some of the best psychologists in America. If I understand them rightly, a few of them claim that the overt movements which we make when responding to stimuli will produce the facts in question. Others would say that one particular kind of experience, namely, the kinesthesis occurring during such movements, is responsible for organization and grouping. In order to answer certain obvious objections, the first will say that in adults mere _tendencies_ to movement will suffice instead of the overt movements which occurred originally. Similarly, the other hypothesis assumes that even faint reproductions of past kinesthetic experiences will be sufficient to explain organization of other (e.g., visual) experiences in the adult.

In either case, whether the tendency toward movement, or kinesthetic experience, is taken as decisive, the fundamental question will be how these factors produce a definite organization, apparent in the visual field, or elsewhere. As far as I can see the only answers are, in the first case, that our overt movements are organized in exactly the same manner physiologically which, to naïve observation, is plainly given, for instance, in the visual field; or, in the second case, that kinesthetic experiences, and perhaps their reproductions, exhibit that organization. Whatever the process may be, by which organization is supposed to be introduced into the chief sensory field, which for most persons is that of vision, it cannot be imported without existing beforehand in whichever region it is said to have its origin. As long as we consider peripheral movements or sequences of kinesthetic experiences as a series of instantaneous events which follow each other independently and indifferently, it will hardly be possible to use them to explain the occurrence of definite segregated wholes and groups anywhere. Let us take the bright point moving in dark space as an example. If we say that the observer talks about three or seven movements in this case, because he makes or experiences three or seven eye-movements, we are presupposing the same organization in the temporal and spatial sequence of eye-movements, or the experiences of them, which I personally seem to have in the visual field _as such_. Otherwise the observer might as well report 53 or 29 or any other number of events, for apart from organization such an enumeration would be no more arbitrary than that of three or seven parts.

I was once told that all the observations of _gestalt_ psychology are very old and have long been explained by the kinesthetic experiences which occur during eye-movements. This sounds as though a hint about the kinesthetic experiences accompanying vision were satisfactory as an explanation of the phenomena of visual organization. But we see that, instead of having solved the problem, we have only shifted it from one place to another, for now we have to solve the problem of the segregation of wholes in the temporal and spatial extension of kinesthetic experiences.

I shall not deny that the problem of organization exists in the field of movements and kinesthetic experiences. On the contrary, I am convinced that the facts in either of these fields cannot be understood rightly without taking our point of view. But why should movements and the processes underlying kinesthetic experience be the only material capable of being organized, or of being treated from the viewpoint of _gestalt_ theory? If organization is physiologically possible in one field, why not in others? In order to explain the apparent organization of visual experience by accompanying motor experiences, one must assume spatial as well as temporal organization of these motor phenomena. I do not see any reason why such organization should be excluded from optics and acoustics. If there are some more general grounds for the exclusion, I am not yet aware of them. In the meantime we shall not discuss the difficulties which would arise, were we to try to explain _concrete_ particular cases of visual organization by motor phenomena, for in the next chapter we shall again return to the question of indirect explanations of organization.

After what has been said about organization, we cannot be surprised to learn that serious lesions in the optical center of the brain may produce a kind of “blindness” in persons, who at the same time are not deprived of vision. Careful examination of such a case by Gelb and Goldstein[29] has shown that, here, the field of vision has undergone a radical change, organization having disappeared almost completely, so that the field shows a more or less chaotic character. Where he fixes his attention, the patient is able to grasp some small fraction of a line, for instance, but he can no longer see extended wholes as clear-cut forms. It is particularly interesting to observe that this patient begins spontaneously to rely to a great degree upon motor experience instead of vision. Following the fractions of contours, which are clearer to him, with movements of the eye, he is able in time to build up motor wholes and to recognize them. So, if his name is written on a blackboard, he will follow the first letters and soon guess the rest. But it is possible to exclude this procedure by a simple trick: draw a few lines, which have the same color as the letters, across the name. Since to the patient the name is never given optically as one simultaneously and well-organized whole, and since now he does not see it as one thing and the crossing lines as another pattern apart from it, he will follow parts of a letter or parts of the crossing lines indifferently. The result is that he cannot read the name under these circumstances. The example shows, by the way, how much motor function, accompanying vision, depends itself upon normal visual organization. Organization being a matter of extended regions of the field, wherever only local fractions may become organized to some degree, the _control_ which organization in a large area normally exerts upon the motor function, is made impossible, and results like those I have just mentioned become inevitable.

But why should wholes, detached by the operations of sensory dynamics, correspond so generally to objects, or things, in the practical meaning of the words? Do we have to assume that a surprising harmony is established between the laws of sensory dynamics and the area or the limits of physical things around us? No such assumption need be made, for there are exceptions to the correspondence of sensory organization and physical units. Take all the cases of groups of separate members, the constellations in the sky, the examples of dots forming definite groups (Fig. 1) above, the instances of grouping in ornaments, the parts of which are, in their physical nature, indifferent to each other, i.e., without functional interrelation. In countless cases organization is a sensory reality without there being a corresponding physical unit. Also, continuous sensory wholes may occur in the absence of an homologous physical unit. The reader himself at some time has seen a strange object, perfectly unknown to him, which later on, perhaps after some movement of his head and eyes, metamorphosed into a single well-known thing and some part of another one, these two together having been, at first, unified and segregated as one unknown whole. The same example shows that sometimes to a definite physical object there does not correspond a sensory unit, because in vision its parts have been absorbed by surrounding areas which happen to have qualities appropriate to this effect. This was the case in the puzzle-pictures which years ago amused the readers of magazines. And in the last war it became a real art to make things, guns, cars, boats, disappear at some distance by painting upon them an irregular design, the parts of which would form indifferent spots by intermingling with parts of their environment. The objects themselves are destroyed as optical realities and in their place appear meaningless patches which do not arouse military suspicion, since similar patches are produced constantly by the accidental properties of country and sea.

On the other hand, it is not difficult to explain why visual units in general correspond to physical objects. The things around us are either made by man or are products of nature. Objects of the first class are prepared for our purposes. Therefore, we give them a form and surface, etc., so that they are likely to be seen without difficulty. Without knowing the principles of sensory organization in an abstract form, man works in conformity with them, and so the physical units which are the products of his art will appear as visual units. Furthermore, it is not easy to create a somewhat compact object which, when placed in a simple environment, would not fulfill the general conditions of visual segregation. Camouflage is a difficult art.

With objects produced by nature, the situation is not altogether different. A condition fulfilled by most natural things is the presence of one class of surface properties in contact with another class of surrounding surface properties. This difference is due to the fact that the common origin of the parts of one thing will probably make them similar, whereas in the surroundings the surface properties will generally be of a different character. Therefore, one condition of visual segregation is given in the case of most things. Even if a stone lies half-embedded in the sand, which is nothing but tiny fractions of the same kind of stone, the difference of coherence, and therefore of “inner detail,” between the surface-elements of the stone and those of the sand will be sufficient in most cases to make the stone optically one thing. At least, at the boundary between a natural object and its surroundings some discontinuity of properties almost universally prevails. This discontinuity separates the environment from the interior of the object by a closed outline. Since, as a rule, that will suffice to make even a meaningless area appear as a segregated whole in the sensory field, it will certainly have that effect where the boundary of a physical object is concerned. If there are no such differences and no discontinuity whatever between the object and its surroundings, no visual unit will exist, it is true. But try to find objects which, without fulfilling any of the conditions of sensory segregation, are still plainly before you, because of the influence of meaning! You will have a hard task. Our general experience shows that wherever the conditions of visual segregation work against a unit, it will not exist in the sensory field of a naïve observer, even if it is well-known as such and is camouflaged only momentarily by special circumstances. A more detailed discussion would have to treat here the problem of visual depth and the segregation of things as three-dimensional wholes. But, though this question is of the greatest importance for the correspondence of physical units and sensory segregations, I must leave it untouched for the present, because as yet in this field experimentation as well as theory is in a rather undeveloped state.

In the last paragraphs I have laid some stress upon the fact that organization in a sensory field is something which originates as a characteristic achievement of the nervous system. This emphasis has become necessary because some psychologists have recently said that, according to _gestalt_ psychology, “_gestalten_,” i.e., segregated sensory wholes in this connection, exist outside the organism and simply extend or project themselves into it. This is so absolutely wrong that I cannot comprehend how the misunderstanding arose.[30]

But after what we have seen, it is quite another problem to ask how far sensory organization, though being a characteristic achievement of the nervous system, may have an objective value at the same time. Between the physical objects around us and our eyes waves of light are the only means of communication. These do not bring the “_gestalten_” ready-made into the organism; rather, the segregation of wholes occurs in the nervous system; but the result may tell more about some of the objective properties of the world around us than the rays of light would be able to do. We do not always learn more about an object, the nearer we approach it. For instance, when a lens is put in the way of the light reflected by a bright object, it would not be wise, for the purpose of getting a clear image of the object, to bring the screen as near as possible to the lens (and thereby the object); at a certain distance the projection tells much more about the object than nearer by. Similarly, sensory organization may give us a “truer” picture of the world around us in some respects than the rays of light, though these are the first messengers coming from the objects and sensory organization occurs later on and farther off.

Indeed, the waves of light do not contain the slightest indication of any organization or any “belonging together” which may exist among the parts of the objects by which they are reflected. Each element of the physical surface reflects light independently and, as reflectors, two elements of the surface of a sheep, for instance, have no more to do with each other than one of them has to do with a surface element in the animal’s environment. In reflection, therefore, no trace is left of those units which exist in the physical world; they are dispersed completely into an indifferent mass of rays, all equally independent of each other. By the refractory properties of our eye those rays, which come from one point in the outside world, are made to converge upon one point of the retina; also the geometrical relations of the points on the surface of an object are reconstructed here, in large measure. Still, each local stimulus thus achieved is an independent affair, and rays coming from elements of the surface of one physical object, the sheep for instance, are as indifferent to each other as they are to stimuli from the sheep’s environment. So we have no organization at all in retinal stimulation, no wholes, no groups, no segregation. It cannot be asserted, in opposition, that there is one definite area or patch on the retina as the image of the animal, for the elements of this area are as independent of each other functionally as any one of them is independent of an element outside the image. In psychology much has been said about the stimulus-error which consists in our confusing our knowledge about the physical conditions of sensory experience with experience as such. But another mistake, which I propose to call the _experience-error_, is not less unfortunate. It occurs when we unintentionally attribute certain properties of sensory experience to the actual constellation of stimuli, properties which are so very common that we tend to apply them to whatever we are thinking about. This is the case primarily, wherever we have not yet learned to see the _problem_ contained in those common properties of experience. No wonder, then, that neurologists and some psychologists still talk about “_the_ retinal process” corresponding to an object, as though there were something like a segregated functional unit on the retina. Whereas as a matter of fact the whole retina is a mosaic of indifferently related spots, and this is the case until sensory organization begins physiologically.

Once we have realized, however, that stimulation, as such, is completely unorganized, the enormous biological value of sensory organization will become apparent. Since the rules governing this organization conform to the structure of objective units, to objective divisions, to objective “belonging together,” in very many cases the result of their operation is a kind of reconstruction of those aspects of the objective physical situation which are temporarily lost on the way between the objects and the sense organ. It is true that continuous wholes are sometimes segregated, and groups of separate members are often formed, which do not correspond to objective physical units. But that is not a serious deficiency when compared with the indefinitely large number of cases in which organization is a picture of objective facts. If all the content of the sensory field were indifferent grains of sensory stuff, it would be a hard task to orientate ourselves in and to react to such a world. I am not sure that even after years of trial and error with regard to such a field, a child would _learn_ to organize it. Considering the situation impartially, we may come to the conclusion that organization of the field, as an original sensory fact, is much more important biologically than the properties of local stimulation are. Color-blind people are perfectly able to adjust to their environment although their experience has fewer nuances of stimulation than the normal. This is so because their lack is not a serious impediment with respect to the practically important similarities and differences in stimulation. Differences of chroma are usually associated with differences of brightness (cf. p. 144). That is enough for _organization_, and since most of our behavior will be determined by this property of the field, even a large deficit as to qualities does not matter very much.

Organization is no less important for the procedure of science than it is for practical life. We saw in the first chapter that, as a physicist, sensory experience is my only primary material. But what experience? The system I am investigating, the apparatus of research, its scale, the needle, and so forth, are all of them segregated wholes, or sub-units, in my sensory field. If they were not given to me in such an order of “belonging together,” physical research would be all but impossible. About this phase of “objective method” we do not hear very much, when behaviorists recommend the procedure of the natural sciences to us. But we should, since, if we consider physical research as a series of physiological events occurring in the physicist, we are still confronted with the problem of organization as an aspect of those events, which is absolutely indispensable for their success.

At the same time we can understand why the formula of “stimulus and response,” though sounding well at first, is quite misleading as long as the term “stimulus” is used as carelessly as most behaviorists do use it. One stimulus, when taken in the strict meaning of the word, is not followed by one definite reaction in a great many cases (cf. Chapters III and IV). In optics, for instance, the organism will respond to an objective constellation of millions of stimuli by developing, first of all, an organized field, many and perhaps the most essential properties of which have no physical partner among the single stimuli (cf. Chapter VI). Reactions of the effector organs may and will begin very soon, in many cases; but, as the eye-movements show, even the first of these reactions will depend upon the developing organization of the field, because the laws of optically determined eye-movements refer to the boundaries of segregated wholes, to the situation of these wholes in the field, and to lines, but not to “sensations” as such. Apart from eye-movements, what is called “acting” in man will be a reaction to a well-developed field and in most cases to some definite whole in it. If, therefore, we say that in psychology the right formula is, _Constellation of stimuli--Organization--Reaction to results of organization_, such a statement fits the facts incomparably better than the usual one. The organism is not barren functionally; it is not a box containing conductors each with a separate function; it responds to a situation, first, by dynamical events peculiar to it _as a system_ and, then, by behavior which depends upon the results of that dynamical organization and order. Suppose that somewhere in a factory HNO_{3} were produced out of its elements and that in another part of the factory the product of that chemical organization were used to dissolve silver,--would you say that the silver reacts to nitrogen, hydrogen and oxygen? You certainly would not, because what happens to the silver depends upon that chemical organization, and it cannot be understood as a reaction either to those elements separately or to the sum of them. If that is so, we should also be very careful before we refer to types of behavior as being reactions to “a stimulus” or to “some stimuli.” Even the last expression would often be quite ambiguous, because it might mean that the behavior in question is the consequence of several stimuli working independently at the same time, whereas it may depend upon a product of sensory organization.

Once I tried to convince a behaviorist that referring to “a female” as “a stimulus” for a male bird is equivalent to completely closing one’s eyes to the problem of _gestalt_ and organization. It was not possible. Though (or because?) he treats sensory experience as something without any interest for psychology, the behaviorist committed the “experience-error” so continually and pervasively that “the female bird” remained “a stimulus” for him. How often has “a mouse,” “a door,” “the experimenter” and so on been called “the stimulus” in animal psychology! Innocent though this expression may be, if it is used as an abbreviation by those who are fully aware of the problem of organization, it will hide this problem in a most unfortunate manner when used by an author who is not free from the “experience-error.”

I mentioned above the great biological value of sensory organization as a reconstruction in nervous process of objective “belonging together.” But how can it be a reconstruction if, on the way from the objects to the sense organ, the waves of light are an unorganized mass of independent events? There must be something in this transmission of rays which determines the “right” organization in most cases. We have seen, indeed, that the relations of neighborhood, of similarity and difference among the stimuli, though these are indifferent to each other dynamically, are in some respects a copy of the corresponding relations among the surface-elements of surrounding objects. Some definite relations among the stimuli as they issue from the physical object, and the preservation of these relations in transmission, seems to be an essential condition for the organization of units corresponding to objects in the outer world. But if organization of the field depends upon the relations of stimuli as these are distributed on the retinæ, we must draw the conclusion that sensory organization cannot be understood by considering independent local processes as such. Now we know that, in dynamical self-distribution, process-in-extension exists as a functional whole. So we must assume that sensory organization, as we have considered it in this chapter, is a property of such a dynamical distribution, occurring under definite conditions of stimulation. At the same time we must remember that everywhere in physics dynamics depends upon the _relations_ between given conditions. The more probable will it appear to us that sensory organization, as depending upon the relations of stimuli, is to be explained as an effect of sensory dynamics within the field. By studying organization, therefore, we may be able to discover what particular kind of dynamical events is responsible for sensory order.

_Gestalt_ psychology is said by some critics to repeat the word “whole” continually, to neglect the existence of parts and therefore to sacrifice that wonderful tool of all scientific procedure, analysis. Nothing could be a more misleading statement, as may be judged from the fact that we found it necessary to mention _segregation_ wherever we were dealing with a unit or a definite whole. In dynamical distribution, as we have seen, the functional “interwovenness” of a field is altogether compatible with dynamical segregation. We may even say that in _gestalt_ analysis we find the _genuine_ “parts” of the field as segregated wholes and groups and, in these wholes or groups, their genuine “parts” again as subordinate wholes and members, whereas the so-called sensations of introspective analysis are parts existing only in construction and theory. For this very reason analysis as a statement about “real” parts, existing in consequence of organization, is a perfectly legitimate and necessary procedure in _gestalt_ psychology, probably much more valuable than any analysis into sensations which certainly no one finds segregated in his visual field.

One remark is needed here about another kind of analysis. I may passively accept what I find before me as the sensory field. Then analysis is possible in the meaning just defined. I may, however, adopt a special attitude with regard to the field, selecting some of its members and more or less suppressing the rest. In many cases a change of organization will be the consequence of such an attitude, and hence “analysis” of this sort involves a real transformation of sensory facts in _gestalt_ psychology (cf. Chapter IV, p. 124). Of course, an analytical attitude is not the only one by which a change of organization may be produced. When we select certain members of the field, we can keep them together at the same time and so favor one special kind of “belonging together” instead of that which would prevail without our interference. Again the change produced by our attitude will be a real transformation.

From the viewpoint of _gestalt_ psychology a change of attitude involves a definite physiological stress exerted upon a sensory field by processes originating in other parts of the nervous system, and to some degree the organization of the field may yield to it. The figure 7, for instance, is seen normally as a symmetrical form. By picking out the lines marked “a” however and keeping them together I can almost see the figure 7a, the lines marked “b” being repressed. In the same way I may favor the lines marked “b” and, as it were, create the figure 7b. How concrete and real such a change is, will become apparent if we consider the point which is the center of the figure objectively. When we produce the figure 7a by favoring the “a,” that point is shifted to the right, as it also is, of course, when the lines marked “b” are not drawn at all. It is shifted to the left when we produce Fig. 7b.

In some cases sensory organization seems to change without any influence being exerted upon it from without, simply because processes which remain the same for some time in the same part of the nervous system tend to alter conditions in that part and to block their own path. We know that the same thing occurs in electrolytical cells in which the current polarizes the electrodes and thereby creates forces opposed to itself. In Fig. 8 we are confronted by a pattern formed by three narrow sectors. Looking at the center of it, most persons will suddenly see another pattern after a while. In the new shape those lines, which belong together in the first pattern as contours of one arm, belong to separate arms and vice versa. The organization is changed. By appropriate experimentation, making our subject fixate the center for a long while, we can reduce the time for either shape to a minimum value, so that the alternations follow each other very quickly.[31] If now the figure is turned around a little, so that the arms have another position, the figure becomes as stable again as it was at first, and only after some time the alternation will quicken, as in the first position. In my judgment, this fact may be taken as evidence for assuming that a local effect of organized processes itself produces the alternations of organization.

BIBLIOGRAPHY

W. Köhler: _Die physischen Gestalten_, etc. 1920.

W. Köhler: _Komplextheorie und Gestalttheorie_. Psychol. Forsch. 6,
1925.

W. Köhler: in _Psychologies of 1925_ (ed. by C. Murchison).

W. Köhler: _Bemerkungen zur Gestalttheorie_. Psychol. Forsch, 11,
1928.

M. Wertheimer: _Untersuchungen zur Lehre von der Gestalt, II_.
Psychol. Forsch. 4. 1923.

VI

_The Properties of Organized Wholes_

THE dawn of the _gestalt_ problem in modern psychology was not the idea of dynamical self-distribution as opposed to order enforced by arrangement; nor did it begin with the discovery that segregated wholes represent highly important sensory phenomena. The starting point was the observation that sensory fields are replete with qualities and properties which one neglects if one takes “sensations” as their sole content and which, indeed, may have a mysterious aspect when first viewed in this way. It was von Ehrenfels who, preceded by some casual observations of Mach, directed the attention of psychologists toward the fact that a great many, and perhaps the more important, properties of sensory fields do not fit into the scheme of concepts which is centered around the idea of “sensation.”

If it is natural for a “sensation” independently to fill its local place in the field, determined by one local stimulus alone, the characteristic and surprising feature in those other qualities (which are usually neglected) is their existence only as properties of somewhat extended regions. From this fact it seems to follow that those qualities of von Ehrenfels cannot be determined by single local stimuli; their existence, then, depends upon several stimuli having a specific effect in a certain _area as such_.

As an example we may take a glass of water in which soap is dissolved. The aspect of such a liquid is called “trübe” in German, which in English means something like “dim” or “turbid.” Now look at it through a little hole made in a piece of cardboard and you will see the hole filled with a certain hue of gray (perhaps a little bluish or reddish), but the quality of “dimness” or “turbidness” will have disappeared. It is the property of a more extended field and depends upon more than local uniform stimulation. Exactly the same is true of the dimness or diffusedness which appears as a quality of things seen in a dark corner. Again no local impression, “isolated” artificially, shows any dimness, but the extended area does so in a striking manner. “Clearness” and “definiteness” as qualities of a field or of parts of it, have the same supralocal character. I may also mention the property of a surface which we perceive by touch as “rough” (the German “rauh”). There is no character like “roughness” in purely local experience of touch. And further we see that von Ehrenfels’ peculiar qualities occur in temporal extension as well as in space in that the German word “rauh” is used for certain acoustical phenomena, as it is for “rough” surfaces. When listening to rather rapid beats or to the “R” of human speech we get that peculiar sensory quality, which seems to be intrinsically similar to the “roughness” of a surface. Again, as this quality depends upon rapid beats, if stimulation is shortened below a certain limit, it disappears, whereas other acoustical qualities will subsist. In passing we may remark that in most cases words like “homogeneity” and “continuity,” whether applied to optical or to other experiences, mean properties of extended sensory fields.

From a functional point of view, these observations are less surprising than was the general opinion at the time of von Ehrenfels’ discovery. The processes directly underlying our experience of a color will be a certain chemical reaction, i.e., certain molecules are built up or destroyed. Now the chemist may analyze such a reaction, but there is a natural limit to his analysis, because at least one whole specimen of each atom or molecule taking part in the reaction, and the whole dynamical event thus comprised, must be included. Beyond that limit what is called “this specific reaction” will lose its meaning for the chemist and, therefore, for psychophysical theory which associates one definite color with one definite kind of reaction. Therefore, even before parting with the theory of “local sensations” we are obliged to accept dynamical realities existing only in somewhat extended areas of space. If that is so in chemistry, the same fact should not frighten us when we face it in direct experience.