INFORMATION, REDUNDANCY AND GESTALT PSYCHOLOGY: AN HISTORICAL NOTE AND TRANSLATION

BRENDAN MAHER

Harvard University

Nearly all references to the introduction of the concepts of information and redundancy into psychology begin with the paper by Shannon (1948). Miller’s sum- mary of the basics of information theory in the American Psychologist (A.liller, 1953) may be taken as one of the early formal introductions of these concepts into the published psychological literature. Cherry’s (1951) history of the theory of in- formation makes no mention of any prior work by psychologists in this area.

However, the Danish Gestalt psychologist, Edgar Rubin, had been conducting investigations into the phenomena of rcdundancy and information in human spcech in his Copenhagen laboratories for some years before Shannon’s first papers. Publi- cation of these experiments was quite informal and the record of them consists largely of lecture notes taken by Rubin’s students from time to time. It appears from these notes that Rubin conceived of redundancy in language as being the inevitable outcome of a process whereby safety margins are built into systems that may be placed under varying and unpredictable demands in operation. The process whereby i t is possible to hear a message correctly and completely even when trans- mission has been distorted and only partially complete can be seen, therefore, as analogous to the processes in visual perception whereby completion or closure of figure is achieved even when the stimulus input is less than complete. It seems probable that Rubin conceptualized redundancy in language in terms very closely related to the Gestalt concept of closure.

For the historian of the behavioral sciences, this work may be of some interest, indicating as i t does a relationship between communication theory and Gestalt psychology that has not been widely recognized. The remainder of this paper con- sists of a translation from the Danish of Rubin’s account of his work on redundancy, together with the notes of Professor Edgar Tranekjaer Rasmussen, (now retired from the University of Copenhagen) who served as Rubin’s assistant in this work.

ON REDUNDANCY AND OVERDETERMINATION BY

EDGAR RUBIN’

The process of comprehension of what someone else is saying seems simple and obvious: we do not reflect consciously on what is taking place. It seems very difficult, however, to give a scientific account of what happens and to analyze what is in- volved in the comprehension of human speech.

1This paper is based upon a set of lecture notes transcribed and organized by Prof. Gerhard Niel- sen. These were later published under the title Om forstaaetighedsreserven og om overbestemthed. In G. Nielsen (Ed.), Ti1 minde om Edgar Rubin. Nordisk Psykologi, monografserie, 1956 No. 8, 28-37. The present translation and abridgment by Brendan Maher is made with grateful acknowledgment of the help of Professor Nielsen who corrected many errors. Professor E. Tranekjaer Kasmussen kindly provided his own notes and discussion of Rubin’s work on this topic. Rubin’s research on redundancy began in 1922 and led to a series of experiments in the 1930’s and 1940’s.

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Unfortunately for us, the comprehension of speech probably depends upon varying combinations of factors in such a fashion that we cannot specify unambigu- ously what the comprehension of speech comprises. However, to develop attempts to solve this problem we must, from time to time, vary our tactics: but this demands a certain kind of insight into what the comprehension of speech may consist of. What- ever our various tactics might be, the following propositions may be self-evident.

Let us assume a situation the elements of which are that somebody is talking and addresses himself to one or more other people in a straightforward manner, not using words to conceal his thoughts. We assume that, in the ordinary course of events, he wishes to be understood and that the person or persons being addressed are interested in understanding him. One could point to cases where a lecturer is essentially interested only in delivering his lecture, and one can point to people for whom the situation is an opportunity to chatter. . . . When one is speaking, one is normally interested in being understood by the person to whom one speaks. Now we say a t the outset that one unconsciously adapts the volume of one’s voice, articulation and rate of speech to the circumstances in which the listeners are pre- sumed to be, and that one does this also with pronunciation and finally in considering the choice of word and sentence structure to use. One talks in a particular way to a foreigner, one talks in a special. way to a little child or a dog (most people firmly believe that dogs understand %his special dogtalk). Some Danes sound a little Swedish when they are talking to2Swedes and by the same token, Swedes adapt their language towards Danish when talking to Danes.

If I give a lecture to a group of people frormdiffering backgrounds, and I do not wish to speak in some special manner for prestige purposes, then I adjust my style of speech to the requirements of the group as a whole. I adapt myseIf towards whatever is average (that is, my impression of this, whatever that may be) normal or typical for the group. When the topics are concerned with matters in which we are well versed then we comprehend everything said in our native tongue and can, to some extent, achieve excellent comprehension even under poor conditions : in- distinct speech, great distances, bad acoustics, simultaneous noise and distortion on the telephone, radio and phonograph do not prevent this comprehension. But when the talk is concerned with an area that we have not mastered, difficult condi- tions of this kind will interfere with Comprehension. These disadvantageous condi- tions will often hamper comprehension of a foreign language where they would give no trouble to a native-born speaker of the tongue. For example, while we talk quite easily over the telephone in our native language i t can be very difficult to understand people talking in a foreign language even though we understand them quite well when talking face to face. This suggests that, under normal conditions, we have a surplus of comprehension a t our disposal which acts, within certain limits, like a “reserve” and can be made available to us under difficult conditions. This re- dundancyZ receives a crucial contribution from the structure of the language itself. That is to say that i t is a general feature of spoken language that it does not confine itself to the minimum necessary for comprehension. Spoken language is, itself, only a part of the totality of what is involved in communication, i.e., emotional ex-

*Rubin here uses the Danish word Fo~stmebesreserve which might be translated literally as “comprehension-reserve,” but which is best rendered as “redundancy,” as will be evident from the situations which he selects as examples of its operation.

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pressions, facial expression and gestures and also, sometimes, direct overt behavior. It a person goes out cycling with someone else and says, “We are riding,” this is contributed to by the information given by the action of riding itself.

This kind of situation is found quite frequently where people who are good team-mates work together in a complex activity. In these circumstances, involving rapid and precise cooperation, actions can, for the experienced individual, become so expressive themselves that the interaction is carried on with a minimum of spoken communication.

As already mentioned comprehension is facilitated by differences in the sound elements of words; however, these sound elements differ more than absolutely necessary to distinguish between them. Thus, it is the case that many spoken expressions are over-determined. In corresponding fashion a command or a request are over-determined both through word structure, tone of voice, and the content of the words, word-melody, word-order, suffixes, inflections and elements. It can be shown that each of these often duplicates what has already been communicated by some other route. The way in which this over-determination is produced varies from language to language. In any given language i t changes from sentence to sentence, with differing over-determinations. But, by and large, over-determination is a very frequent phenomenon.

I n one sentence, many words can communicate the same plural. In the sentence ‘(Du bist mein Freund, ” or “You are my friend,” there are several expressions for (Ldul’ or “you.” I n saying, “I tell you, you are my friend,” the two “you’s’’ do not constitute an exact duplication but there is a more subtle repetition in which a ‘(you” atmosphere in the first part of the sentence seems to appear also in the latter part. The repetition does not occur in, “I tell you, he is my friend.”

In addition to the ways that we have mentioned, redundancy may be created by several other methods. We say in Danish-or at least it is permissible to say- “Hesten, den aeder sin F+de,” “Manden, han spiser sin Mad.”3 Not only the first word in the sentences but also the words “aede-spise” and “F4de-Mad” make it evident that the first example refers to an animal and the second to a human. In French, to say, “to bring along” (at medbringe) indicates not only that something is being brought but also, by the use of the words “apporter” and “amener” respective- ly, whether or not an object or a person is being referred to.

There is a specific form of redundancy where a single word is repeated. This would be so with “Oui, oui” or even “Oui, oui, oui.” Some people habitually say, “Goddag, goddag,” or “Farvel, farvel.” I am not counting here the particular kind of repetition where repetition has a special importance, as for example, when an angry man says, “Go, go,” or when Hamlet says, “Words, words, words. . . .”

A more common form of this redundancy is the repetition not of single words but of entire sentences or paragraphs-not word-by-word repetition-but repetition that more or less preserves meaning. In a scientific discussion by a clear and ex- cellent speaker I have noticed that he repeated, SO to speak, every single thing at least Once in slightly different words. In certain cases, repetition can be disruptive and where an individual continues with it, it becomes tiring. But another situation,

%itera1 translations would be “The horse, it eats its foqd,” and “The man, he eats his food.” In Danish the verb “to eat” and the noun“food” vary according to whether or not one is referring to an animal or a person.

INFORMATION, REDUNDANCY AND GESTALT PSYCHOLOGY 79

with which I am familiar from written language can also occur. With certain com- plex ideas Kant often repeated an item in slightly different words. Here, when trying to get to the bottom of the whole thing, repetition creates a special difficulty for one may try to understand the first formulation and then the second and finally realize that they cover the same theme. Here the labor of comprehension would have been easiest if Kant had disciplined himself to give the single, best, possible formula- tion. One discovers, when one first becomes interested in it, how overwhelmingly common repetition of meaning is in spoken language. The reasons for this, which may operate in combination, can be various. When a statement has been completed but one has not completed the thought, it is as if the idea/thought itself tries to get expressed again.

It can also be the case that one uses repetitions to maintain and dwell on an idea. Compare the role of silent speech in thinking and problem solving (a phe- nomenon outside the present topic, however). The reason can also be that one is not completely satisfied with the first formulation. The motives mentioned here are relevant only to the speaker, himself, but it can also be that he wishes the listeners to dwell on the topic so that it will make an impression on them and they will reflect on it and remember it. Finally, the reason that one repeats and uses alternative words is to assist the listener to a better comprehension. In the many varieties of reason that we have enumerated-without any claim to completeness-there is a little clue to the correctness of our position that repetition is not necessarily to make compre- hension easier or to contribute to an understanding reserve, but repetition can, never- theless, work to that end quite independently of the motive to do so.

There are a great many factors involved in the comprehension of speech, one or more of which may become distorted so that when the change has become sufficiently great, speech is incomprehensible. The distortion factors can affect either the stimulus output or the stimulus input. The speaker can speak more and more softly, or more and more indistinctly or more and more ungrammatically. Speech can be deformed more and more through bad telephone connections, etc., simiIarly, the subject’s hearing can be weaker (e.g., increasing deafness).

It is generally the case that these factors can change in part in detrimental directions without this having any perceptible effect on comprehensibility. We have characterized this state of affairs by the use of the word Forstaaelighedreserue (lit. “reserve of understanding,” or redundancy). Redundancy is thus the term to denote the fact that certain factors can become distorted without having any perceptible effect upon comprehension. Thus one can talk somewhat more softly and less dis- tinctly than usual without having any appreciable effect upon comprehension.

The Reserve Principle-A General Phenomenon There are certain systems which are sufficient for us if they operate effectively

a percentage of the time. It is not necessary in hunting or war that every shot should hit. When distributing advertising leaflets, it is not necessary that every leaflet should create a customer.

For other systems it is necessary that for practical purposes nothing ever goes wrong. A bridge must not be such that it disintegrates from time to time and cars fall below. A large business, a bank, for example, must always have money at its disposal so that it can pay the demands that are made on it. In a case where there

SO BRENDAN MAHER

must never be a failure then one purposely builds in a reserve so that i t cannot go wrong even in the event of a series of untoward circumstances coinciding. In the bank, one estimates the largest probable total of withdrawals and then takes care to have a substantially larger sum a t hand. In the case of the bridge, one considers how big might be the greatest load that might be applied and designs the bridge so that it can withstand a substantially larger weight.

Let us look a t some other examples of reserve. In a hospital the patient must never be given poison instead of medicine. Therefore, a special poison label is placed on the bottles; additionally, there is a label which lists the contents, the appearance of the contents and also the eventual smell. Further, there is the painstaking in- struction and training of the personnel and access to the key is possible only to supervisors and sharpens the feeling of responsibility with unpleasant consequences for those who break the rules.

On the railway there is a very complicated system designed to ensure that one train does not collide with another; from our point of view this is related to the example from the safekeeping of poisons.

In this last example, together with the examples of the bridge and the bank, the reserve has been created by increasing the magnitude of one factor; time, material strength or cash supplies. In the other instances, the reserve comprises a series of factors each of which is calculated to safeguard the goal. This leads to a condition which I have called (in a lecture to the Society for Philosophy and Psychology) multviatik4

One can talk in a more figurative sense about a reserve-nature’s reserve- meaning that nature operates with a reserve without our assuming this to be created with specific intention, e.g., the millions of young of the codfish. Where people are concerned, we find nature-reserves that are not created with that specific intention either and we find-in the psychological region-something which has arisen pur- posefully and also a transition development. What we call redundancy is just such a development.

In a speaking situation there is both a speaker and listeners. At the outset, the reserve can consist of the fact that the speaker and/or the listener contribute a surplus of meaning above and beyond the threshold for comprehension. Secondly, the reserve includes the fact that if conditions develop that militate against com- prehension it is possible for both the speaker and the listener to mobilize additional resources to aid understanding.

Where conditions make comprehension difficult i t can be achieved by straining to pay close attention. This happens, for example, when one is listening to a lecture in a foreign language-as long as one makes an effort one can understand what is being said-but if one tires or relaxes the whole thing, more or less, goes over one’s head.

We have no precise description of how these efforts are made and we know nothing of their psychophysiological mechanisms. For our purposes here it is sufficient t o state that we know that comprehension can be obtained by exertion where it would otherwise fail. However, we should note that attention often adapts itself to the demands of a situation. Involuntarily, we concentrate more where

4Presumably coined to mean “many ways.”

INFORMATION, REDUNDANCY AND GESTALT PSYCHOLOGY 81

comprehension is difficult than where i t is not. This concentration is not a general arousal of attention but is focused and directed a t understanding the speaker and excluding disturbing factors.

If we imply a concept of energy here we should make it clear that “energy” in this sense does not mean the same thing that i t does in physics: i t is intended as a broad analogy. If the listener cannot make available the energy that is necessary for understanding, for one reason or another, then comprehension will not be achieved.

The difference between the maximum effort that can be applied and the effort that actually is applied a t any given moment reflects the role played by effort (energy) in creating redundancy. When a person is preoccupied with something and is suddenly spoken to there will often be a low initial level of comprehension: the necessary effort is not being applied. Part of the technique of conversational speech is influenced by this. One begins with some casual cliche phrase because its eon- ventional and stereotyped nature makes it easily understood. “Be so good as to tell me . , .” or “There is something I would like to say to you. . . .” This technique may also be used when addressing a large audience. When there is something that one considers particularly important for the listeners t o understand, then one tries to ensure that they attend to it by beginning with, “There is something I would like to emphasize . . .” or by opening with a rhetorical question. In some cases one can assume in advance that there will be a high level of attention, e.g., when a superior talks to an inferior: here i t is not necessary to use these techniques. We may assume that speech habits that are evoked by special situations have been influenced by the emotional aspects of the total situation.

I n all comprehension of speech and redundancy learning plays a very great part. Ability to do something, and to do i t well, can only be acquired by practice. The acquisition of extraordinary skill implies that one can be proficient not only under favorable conditions but also in situations in which several handicapping factors may be operating.

Perception of Words. When we have begun to learn but do not yet know a foreign language the production of a word in i t is achieved by acoustic-phonetic processes different from those we use later when we have mastered the language. It is clear that i t sounds differently to us, but it is hard to characterize the difference in detail. We ask a foreigner t o repeat a word that he speaks not only because we cannot get clear how we should reproduce the word but also because we feel that we have not acquired the right sounds ourselves, which, due to the fact that they are not familiar to us appear as indistinct, undifferentiated and vague. We have ac- quired only the gross features and not the nuances. Likewise, I have sometimes observed that occasionally sound stimuli may produce related but different per- ceptions for a native-born listener while to a foreigner the same set of stimuli produce but a single perception. When a Frenchman corrects us and says that we should pronounce something thus, and not SO, we are helpless and uncomprehending because we cannot hear the differences in the cues. Finally, after many repetitions and care- ful listening differentiation begins. By the same token, long statements in a foreign language may appear to be poorly arranged into words and sentences and to be con- fused syllabically. This is associated perhaps with the fact that speech in a foreign tongue seems to go faster than in one’s mother-tongue, and that a passage spoken in foreign language seems shorter than in one’s own language.

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Rate of Speech. When speech is being uttered a t a particular speed, attentional monitoring of it is being carried on at the same speed. If the speaker is very slow one becomes impatient: it seems as though the speaker will never get t o the point and one has a continual struggle with oneself to avoid escaping into thinking about something else. Keeping pace with the tempo of the speaker can be a con- tinuous and irritating strain. There is a well known physician’s remark, where he asks the patient, “Please talk more quickly or I can’t follow you.” For an activity to be pleasing then it must engage one’s attention to an acceptable degree: the frus- tration caused by someone’s speaking too slowly can be due to a feeling that one is wasting time on something that could be going more rapidly.

In the case of rate of speech we can not assign exactly the same factors as those that have been discussed above, for rate of speech cannot ordinarily vary indepen- dently of comprehensibility. When the rate becomes too fast the speech becomes in- comprehensible. If one speaks rapidly one gabbles-speaks indistinctly, stumbles over words and so forth and this is a very powerful factor in generating incompre- hensibility. If a phonograph record of speech is played with increasing speed the pitch becomes higher and higher, distorting the signal and producing incompre- hensibility.

One can talk with variable distinctness even though the content and rate of speech are constant. Distinctness seems to be a factor that can vary quite indepen- dently of other factors, even though it does not always do so. Here we need be clear only about the overall processes. As a rule one can talk less distinctly without falling below the threshold of comprehension. One can say, therefore, that there is a surplus of distinctness and that this surplus contributes to redundancy.

Related to the fact that speech can become less and less distinct with variations in speaking are the distortions that develop when speech is conducted over the tele- phone, radio or gramophone. It is well-known that when these technical distortions become very great, speech becomes incomprehensible; but there can be quite sizeable distortions in a detrimental direction without necessarily reducing comprehension to the threshold level. Under these circumstances one seems to get the meaning through one or more other factors that have contributed to redundancy.

But i t is difficult to be more precise about this phenomenon, because certain technical distortions can, to some extent, be almost beneficial for comprehension- certain distortions can be beneficial a t the beginning but later change in a detrimental direction when the distortion exceeds a given magnitude. It is uncertain, for ex- ample, that the volume control on the radio always gives the best possible com- prehensibility when i t is set in the position equivalent to natural speech while ignoring the other noise factors that very with this.

Similar considerations exist as for those that applied in the case of technical distortions. It is certain that great magnitudes of resonance can make speech unintelligible but it is not therefore certain that speech alters in a detrimental way with lower degrees or resonance.

Under the heading of distinctness can also be included intonation, pauses and speech melodies. We shall list these factors under the single heading of articulation. The correct use of these has important implications for understanding and for propoganda effects. Example: It is told of an English politician that, one evening, in Parliament he made a contribution to the debate using a well worked-out con-

A second kind of distortion occurs with resonance.

83 INFORMATION, REDUNDANCY AND GESTALT PSYCHOLOGY

elusion without making any impression. His voice was thin and his articulation was bad. With his approval another politician used the same peroration the following evening and won great applause. The proper use of articulation has had great effect in propaganda operations. But it also has great relevance for proper under- standing. I shall read but a few lines for you quite monotonously and you will notice how difficult it is to understand me. It is the correct division into sentences, and their relation to one another that is hard to grasp. When one can, nevertheless understand a monotonous text, articulation gives a contribution to redundancy.

ON EDGAR RUBIN’S “CONCEPT OF RESERVE” BY EDGAR TRANEKJAER RASMUSSEN

When, in 1936, I became E. Rubin’s assistant, he worked among other things with a series of psychoacoustic experiments. Some of his interests and some of the results that he obtained in these experiments were related to his theories of the concept of reserve on which he had worked for several years, as it is described in the preceding article.

I n one experiment he constructed a “contact drum” which when rotating could alternately connect and disconnect a microphone so that only segments of the signal were transmitted.

The drum was divided diagonally into two halves one of which was covered with metal and the other with some insulated material. At one end of the drum, then, the entire surface was of metal and at the opposite end it was covered with insulated material. A contact could be moved along the drum to produce shorter or longer contacts extending from total contact in the one end of the drum to total lack of contact in the other end. The speed of rotation could also be varied so that the cycle of contact/no-contact could be controlled in two ways: one by the ratio of conduction to insulation (the position of the contact) and the other by the temporal frequency of the interruptions (the speed of rotation).

With this apparatus, Rubin could control the threshold for interruption of transmitted speech without causing incomprehension.

It was quite amazing that within a reasonable frequency of interruption (ranging from approximately 20 to approximately 50 rotations pr. second), a con- siderable part of the signal could be cut off (in certain instances more than half of the transmission) without seriously impairing the understanding of speech. The subject listening to the transmission had the experience of hearing comprehensible speech accompanied only by a disturbing noise. He had to overcome this disturbance somehow through an effort very much like the one described in the preceding article by Rubin. None of the subjects perceived that a part of the signal was actually eliminated.

With this technique it was impossible however to schedule the disconnections in the stream of speech in any specific location. We can only say that the disruptions were located randomly, from which follows that it could not have been meaningful elements ((‘betydningsbaerende fonems”) which were transmitted systematically to ensure comprehension. In other words, this implies that we do not use total input in ordinary comprehension of speech; we can dispense with part of it. I n normal circumstances, the ear receives the total input of transmitted stimulation; but not

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all of this is fully used in the subsequent nervous processes. The unused part of the input forms, then, some kind of “reserve” at our disposal. In an optimal situation we do not utilize the reserve; under certain circumstances, however, we may need to.

When subjects listened to foreign languages which they understood such as English or German in the experiment on disconnection of transmitted speech, i t was not possible to cut off as much of the input as when they listened to Danish, without causing impaired comprehension. It seems fair to conclude, therefore, that in listen- ing to a foreign language one has to utilize the reserve even though one is fairly familiar with the language and much more so than is necessary when listening to one’s own language.

At the Fourth International Congress of Linguists in 1936 in Copenhagen, the well-known phonetician Paul Menzerath demonstrated his experiments to Rubin who became highly interested in them and related them to his own research. Both Menzerath’s and Rubin’s experiments showed that Gestalt phenomena play a role in the comprehension of speech just as within other areas, and that a Gestalt may be created by very different kinds of stimulus.

Another of Rubin’s studies also derived from his concept of “reserve” consisted of an experiment on competing voices (dichotic listening) : two persons read aloud from individual texts a t the same time, so that the listener heard two competing voices. In some of the experiments, the readers were in the same room as the subject. In other experiments, the readers were placed in different rooms and their voices were transmitted by means of a microphone and a loud-speaker to a third room in which the subject was. In the latter case, the subject heard the voices over two loudspeakers or just one, or he listened to them on a set of earphones.

The subject was instructed to follow one of the voices in such a way that he could understand what was being said and a t the same time he was asked to follow the other voice as much as possible.

At first, Rubin was mostly interested in the subjects’ descriptions of the second voice. The descriptions could be grouped in the following categories: the subjects experienced the second voice (1) as a mechanical noise; (2) as human vocal noise; (3) as incomprehensible speech sounding Danish; and (4) as fully understandable Danish. There were several nuances among these categories.

Based on these descriptions Rubin formulated the following hypothesis: the nervous processes responsible for the fourth type of experiences are more complica- tive and extensive that the processes occurring in connection with the first type of phenomena. He spoke of higher and lower nervous processes and related these also to his figure and ground studies in which he thought that the perception of the figure was due to a higher nervous process than the experience of the background.

Although this may sound reasonable, it was difficult for Rubin to give the terminology “higher” and “lower” a more exact meaning. He worked on the problem for a number of years and the difficulties he met were, no doubt, the reason why he never published his studies. At one point, it seems as if he imagined a way out of the difficulty by relating these phenomena to his concept of “reserve.”

When Rubin spoke of “energy” as in the preceding article, he meant that it seemed to require more mental energy to process stimulus input into “understand- able speech” than to process the same stimuli into another phenomenon such as “vocal noise.” Rubin hypothesized that the subject used so much energy in listening

INFORMATION, REDUNDANCY AND GESTALT PSYCHOLOGY 85

to one of the voices that not enough energy remained to process the input of the second voice into “understandable speech.” Through a special effort, the subject managed to some degree to compensate for this, and when the experiments were repeated and the subject became more familiar with the source texts used by the readers he might even learn to understand both voices equally well. Familiarity with the text then functioned as a “forstaaelsesresevre71 in analogy to what is described in the preceding chapter.

Rubin extended his concept of reserve to other areas of psychology. It seemed impressive to him that an individual’s perceptual environment in general appears to be broader and richer in detail than the individual requires for his immediate purposes, and Rubin spoke in this connection about a “perceptual reserve.” Under certain circumstances, when unforseen difficulties emerge, the individual may need this reserve. If he is under pressure or governed by strong affects and emotions, however, his perceptual field is usually restricted.

Closely related to all this, Rubin worked on his “multiviatic” principle. It refers to his observation that many biological functions are preserved by the exis- tence of several alternative processes (multi via). Depth perception, for example, is achieved by a variety of different processes-retinal disparity, perspective, etc. Even in this example we are dealing with reserves which are, however, of a different nature than the reserves of which Rubin spoke in connection with his discussion of energy reserves. No doubt, Rubin wanted to combine all this into a general theory of reserve. This he never succeeded in doing, and hence it led him to withhold publi- cation of his ideas. Still, he spoke about his ideas in lectures to students, on some occasion when he lectured to an audience of Danish linguists, and also in conversa- tions with friends of his who were themselves distinguished psychologists. I know for example that he presented his ideas to the late David Katz who became very interested in them; they must have inspired him to his Presidential Address “The Psychology of the Margin of Safety” a t the 13. International Congress of Psy- chology in Stockholm, 1951.

In his ideas on reserve or redundancy, Rubin was ahead of his time. His experi- ments anticipated recent work on dichotic listening, redundancy and other concepts that have become well-known through their development by information theroists.

REFERENCES CHERRY, E. C . A history of the theory of information. Proceedings of the Institute of Electrical Eng-

MILLER, G. A. What is information measurement? American Psychologist, 1953, 8, 3-11. SHANNON, C. E. A mathematical theory of communication. Bell System Technical Journal, 1948,

ineers, 1951, 98, 383-393.

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