Lets begin with objective experience. Under normal conditions, objective experience depends upon physical events which stimulate sense organs. But it also depends upon physiological events of the kind we now wish to explore:
The physicist is interested in the former fact: the dependence of objective experience upon physical events outside the organism enables him to infer from experience what those physical events are.
[We] the psychologist is interested in the latter fact: since experience depends upon physiological events in the brain, such experience ought to contain hints to the nature of these processes. In other words, we argue that if objective experience allows us to draw a picture of the physical world, it must also allow us to draw a picture of the physiological world, it must also allow us to draw a picture of the physiological world to which it is much closely related.
Obviously, however, if the characteristics of [concomitant] naturally accompanying or associated physiological processes are to be [inferred] deduced or concluded from given characteristics of experience, we need a leading principle which governs the transition. Many years ago, a certain principle of this kind was introduced by E. Hering. Its content is as follows. Experiences can be systematically ordered, if their various kinds and nuances are put together according to their similarities. The procedure is comparable to the one by which animals are ordered in zoology and plants in botany. The processes upon which experiences depend are not directly known. But if they were known, they could also be ordered according to their similarities. Between the two systematic orders, that of experiences and that of concomitant physiological processes, various relationships may be assumed to obtain. But the relation between the tow orderly systems will be simple and clear only if we postulate that both have the same form or structure qua systems. Sometimes this principle is more explicitly formulated in a number of “psychophysical axioms.” In our connection, it will suffice if we give some examples of its application.
A sound of given pitch can be produced in many degrees of experienced loudness. In geometrical terms, the natural systematic order of all these loudnesses is a straight line, because in proceeding from the softest to the loudest sounds we have the impression of moving continuously in the same direction. Now, what characteristic of accompanying brain events corresponds to experienced loudness? the principle does not give a direct answer. Rather, it postulates that whatever the characteristic in question may be, its various nuances or degrees must show exactly the same order as the loudnesses do, i.e., that of a straight line. Also, if in the system of experiences a particular loudness is situated between two other loudnesses, then in the order of related brain events the physiological factor corresponding to the first loudness must also have its place between the processes corresponding to the two others. This gives the equality of structure of the two systems to which the principle refers.
It seems that the all-or-none law does not allow us to choose “intensity of nervous activity” as the physiological correlate of experienced degrees of loudness. But the principle can be equally well applied if the frequency or density of nerve impulses is taken as the correlate of loudness.
As another example, colors may be discussed in their relation to accompanying brain processes. This relation has been considered most thoroughly by G.E. Mueller. To be sure, his assumption go beyond the principle now under discussion in that he makes hypotheses about retinal processes. The principle as such applies only to the brain processes which underlie visual experience directly. His theory is also more specific, since it includes a statement about the nature of the retinal processes as such. They are assumed to be chemical reactions. This transgression of the principle is perfectly sound for the following reason. If the system of color experiences and that of related physiological processes are to have the same structure, these physiological events must be variable in just as many directions or “dimensions” as the colors are. It is quiet possible that chemical reactions constitute the only type of process which satisfies this condition. Thus the principle of identity of system structure serves to restrict the number of facts which may be considered when more specific hypotheses are desired.
Gestalt Psychology works with a principle which is both more general and more concretely applicable than that of Hering and Mueller. These authors refer to the merely logical order of experiences which, for this purpose, are abstracted from their context and judged as to their similarities. The thesis is that when related physiological events are also taken from their context, and also compared as to their similarities, the resulting logical order must be the same as that of the experiences. In both cases, it will be seen, the order in question is the order of dead specimens as given the right places in a museum. But experience as such exhibits an order which is itself experienced. For instance, at this moment I have before me three white dots on a black surface, one in the middle of the field and and the others in symmetrical positions on both sides of the former. This is also an order; but, instead of being of the merely logical kind, it is concrete and belongs to the very facts of experience. This order, too, we assume to depend upon physiological events in the brain. And our principle refers to the relation between concrete experienced order and the underlying physiological processes. When applied to the present example, the principle claims, first, that these processes are distributed in a certain order, and secondly, that this distribution is just as symmetrical in functional terms as the group of dots is in visual terms. In the same example, one dot is seen between the two others; and this relation is just as much a part of the experience as the white of the dots is. Our principle says that something in the underlying processes must correspond to what we call “between” in vision. More particularly, it is maintained that the experience “between” goes with a functional “between” in the dynamic interrelations of accompanying brain events. When applied to all cases of experienced spatial order, the principle may be formulated as follows: Experienced order in space is always structurally identical with a functional order in the distribution of underlying brain processes.
This is the principle of psychophysical isomorphism in the particular form which it assumes in the case of spatial order. Its full significance will become clearer in the following chapters. For the present I will mention another application of the same principle. It is a frequent experience that one event lies temporally between two others. But experienced time must have a functional counterpart in brain events just as experienced space has. Our principle says that the temporal “between” in experience goes with a functional “between” in the sequence of underlying physiological events. If in this manner the principle is again generally applied we arrive at the proposition that experienced order in time is always structurally identical with a functional order in the sequence of correlated brain processes.
The field of application of the principle is not restricted to temporal and spatial orders. We experience more order than merely that of spatial and temporal relations. Certain experiences belong together in a specific fashion, whereas others do not, or belong together less intimately. Such facts are again matters of experience. The very moment I am writing this sentence, a disagreeable voice begins to sing in a neighbor’s house. My sentence is something which, though extended in time, is experienced as a certain unit to which those sharp notes do not belong. This is true even though both are experienced at the same time. In this case our principle assumes this form: units in experience go with functional units in the underlying physiological processes. In this respect also, the experienced order is supposed to be a true representation of a corresponding order in the processes upon which experience depends. This last application of the principle has perhaps the greatest importance for Gestalt Psychology. As a physiological hypothesis about sensory experiences as well as about more subtle processes, it covers practically the whole field of psychology.
I have just taken an example from outside the realm of objective experience in the strict sense of this term. A sentence which I am formulating is not a part of objective experience in the way in which a chair before me is such an experience. And yet my statement about the sentence is no less simple and obvious than were the others, which referred to order in experienced space and time. This is not always so, however. The observation of subjective experiences cannot be recommended without limitation. In the present connection, only very simple statements in this field can be regarded as sufficiently reliable. Nor need we at present transcend the realm of objective experience. We have just seen that it provides an adequate basis of operations for our immediate purpose.
In the preceding paragraphs my own experience has served as a material which suggests assumptions about the nature of otherwise unobservable constituents of behavior. Now, the only way in which I can bring my observations in this field before the scientific public is through spoken or written language which, as I understand it, refers to this experience. But we have decided that language as a sequence of physiological facts is the peripheral outcome of antecedent physiological processes, among others of those upon which my experience depends. According to our general hypothesis, the concrete order of this experience pictures the dynamic order of such processes. Thus, if to me my words represent a description of my experiences, they are at the same time objective representations of the processes which underlie these experiences. Consequently, it does not matter very much whether my words are taken as messages about experience or about these physiological facts. For, so far as the order of events is concerned, the message is the same in both cases.
If we now go back to the observation of behavior, we have to deal with language as a particular form of behavior in human subjects. Here again we may safely regard language as a message which refers to facts outside the field of language. Here again we may safely regard language as a message which refers to facts outside the field of language. Only the most superficial view would treat words merely as phonetic events. When listening to a scientific argument, the Behaviorist himself will find that he reacts not to the phonetic characteristics of speech but to its symbolic meaning. For instance, he will regard as equivalent such nouns as “experiment” and “Versuch,” “animal” and “Tier,” although in both cases the first and second words are phonetically quite different. Why should this attitude be changed when speaker happens to serve as a subject, and to give us a revealing report?
To repeat, the statements of a subject may be taken as indicative either of his experiences or of the processes which underlie these experiences. If the subject says, “This book is bigger than that other one,” his words may be interpreted as referring to a “comparison-experience” of his, but also as representative of a corresponding functional relationship between two sensory processes. Since from our point of view the same order is meant in both cases, the alternative is of no particular importance. Form the point of view of behavior psychology, the physiological interpretation must be given; but there is no reason why the other interpretation ought to be excluded. The behavior of a chick can tell me without words that he is able to react to one brightness in its relation to another. On the other hand, if in the course of an experiment a human subject tells me that one object appears to him brighter than another, the scientific import of this sentence is precisely the same as that of the chick’s behavior. Why then should language, which is one of the most instructive forms of behavior, be ignored by the experimenter?
Surely, by applying the same technique to man as we apply to the chick, we can avoid the use of language in human psychology. But why should we? The Behaviorist’s dislike of language seems to have merely historical reasons. The Introspectionists have used “verbal reports” in their attempts to dissect experience. I am ready to admit that what they have called introspection has seemed to be of limited value. Unfortunately, as a result of such mistaken efforts, Behaviorists are now negatively conditioned not only to introspection as such, but also to other, entirely innocent, things which commonly accompany introspection. Hence their dislike of language.
K. Koffka: Principles of Gestalt Psychology. 1935
W. Koehler: Dynamics in Psychology. 1940
W. Koehler: “Die methoden der psychologischen Forschung beim Affen.” Abderhaldens Handbuch der biologischen Arbeitsmethoden, VI, D. 1921.
W. Koehler: The Place of Value in a World of Facts (Ch. IV). 1938