Orne, M.T. On the mechanism of posthypnotic amnesia. International Journal of Clinical and Experimental Hypnosis, 1966, 15, 121-134.

The International Journal of Clinical and Experimental Hypnosis 1966, Vol. XIV, No. 2, 121-134



Institute of the Pennsylvania Hospital and University of Pennsylvania

Abstract: Experimental and clinical evidence about posthypnotic amnesia are reviewed. Rather than postulate any single mechanism which might account for the phenomenon, two interpretations are contrasted which seem sharply opposed. First, posthypnotic amnesia may be seen as essentially like any other hypnotically suggested experience. It can be considered as an explicitly or implicitly administered posthypnotic suggestion. On the other hand amnesia can be viewed as a form of dissociation. One possible mechanism of such dissociation may be a basic difference of the structure of thought processes involved in hypnosis compared to those of normal waking experience. In this sense amnesia should occur independently of suggestion and be different in kind from most other hypnotic phenomena. The former mechanism may occur more frequently in experimental situations and the latter in clinical contexts.

Posthypnotic amnesia is present when (a) with or without specific suggestion, the S fails to recall the events which occurred during hypnosis, and (b) these events can subsequently be recovered, either through appropriate suggestions in the waking state or through the reinduction of hypnosis. Posthypnotic amnesia is therefore distinct from simple forgetting, but these two phenomena cannot be distinguished while the amnesia itself persists. Until amnesia is lifted, both should have the same effect--failure of recall--both phenomenologically and behaviorally. However, the distinction between them can readily be made afterwards, by demonstrating the reversibility of

Paper read at Society for Clinical and Experimental Hypnosis, Los Angeles, October, 1965.

1 The laboratory studies reported in this paper were supported in part by Public Health Research Grant #MH 11028, National Institute of Mental Health, United States Public Health Service, by the Air Force Office of Scientific Research Grant #AF-AFOSR-707-65, by Contract #Nonr 4731 from the Group Psychology Branch, Office of Naval Research, and by the Institute for Experimental Psychiatry.

2 I would like to thank Ulric Neisser, Frederick J. Evans, and Emily C. Orne for their detailed critical evaluation and comments during the preparation of this paper. Appreciation for helpful suggestions is also due to my colleagues at the Unit for Experimental Psychiatry: Julio M. Dittborn, Donald N. O'Connell, Peter W. Sheehan, Ronald E. Shor, and Richard I. Thackray.




amnesia. 3 We are not concerned here with loss of memory for traumatic events. The repressive mechanism closely resembles amnesia; it is either analogous or identical.

Despite the extensive literature on hypnosis, very little has been done systematically to study posthypnotic amnesia. A review of the evidence that is available is, therefore, desirable. Rather than postulating any single mechanism which might account for amnesia, two interpretations which seem rather sharply opposed will be contrasted. First, posthypnotic amnesia may be seen as essentially like any other event hypnotically suggested. In effect, it can be considered nothing more than an explicitly or implicitly given posthypnotic suggestion. On the other hand, one may look on amnesia as a form of dissociation. One possible mechanism of such dissociation is the basic difference in structure between the thought processes involved in hypnosis and in normal waking experience. According to this viewpoint, amnesia should occur independently of suggestion, and be different in kind from most other hypnotic phenomena.

Amnesia as a Form of Suggestion

Counter-suggestions for Amnesia

We begin by examining the data, experimental and otherwise, which support the view that amnesia is due simply to suggestion. Perhaps the strongest argument is the fact that amnesia can be prevented by a counter-suggestion given in hypnosis. Under these circumstances, even Ss who are otherwise amnesic will rarely have any difficulty in recall. If a posthypnotic cue is used as the point at which memory should occur, Ss will dramatically describe a sudden awareness of events which they could not previously recall. While this does not mean that the mechanism by which amnesia occurs is due to suggestion, it does show that it can easily be manipulated by specific suggestions.


A S who is able to develop good posthypnotic amnesia will also respond to suggestions to remember events which did not actually occur. On awakening, he will fail to recall the real events of the trance and will instead recall the suggested events. If anything, this phenomenon is easier to produce than total amnesia, perhaps because it eliminates

3 This distinction is supported by Thorn's (1961) finding that amnesia (as measured by the number of hypnosis events which are not recalled later) is uncorrelated with the forgetting of nonsense syllables.



the subjective feeling of an empty space in memory. Such pseudo-memories are usually accompanied by subjective conviction. This technique has been used for the induction of artificial complexes by Luria (1932), Erickson (1952), and others. It is clear that pseudo-memories, which are obviously suggestions, are closely related to amnesia. Thus, it is never possible to induce successfully pseudo-memories in individuals who failed to develop amnesia.

Posthypnotic Challenge

In further support of the suggestion theory, consider the typical behavior of a deeply hypnotized S who has been instructed to forget all that has happened during hypnosis. Immediately upon awakening, the hypnotist may ask him to describe what happened. Typically, S answers, "I don't know," perhaps adding, "the last thing I remember is looking at the target." If he is questioned further about his experience, he may describe a peculiar inability to recall events, a discontinuity of recall which may or may not be associated with discomfort. Very rarely will S describe his experience as though he had just closed his eyes and then reopened them, with nothing intervening. As a rule, he will be aware that time has passed and feel that he ought to recall the events that must have transpired during this time, even though he does not.

What happens if the same S is interviewed immediately afterwards by another E, without removal of amnesia? Three main types of responses will be observed.

(1) Some Ss, surprisingly enough, will be able to describe everything that took place. Not only will they have clear recall for their hypnotic experiences, but they will report having had equally good recall at the time the hypnotist originally asked them. They simply felt unable to tell the hypnotist about their recall and somehow were compelled to act as if they remembered nothing. Clinically these reports are exceedingly convincing in the way Ss describe the compulsion to act as they did. The Ss are not simply humoring E; if anything, they are more puzzled by this verbal inhibition than they would have been by an actual failure to recall. It seems best, however, not to consider such cases as instances of amnesia at all.

(2) Another group of Ss will give a different report in such an interview. They did not have recall when first interrogated by the hypnotist, but in talking with the hypnotist over a period of time, or even more as they talk to the second E, the material gradually comes to mind. A typical S may say that it seems very hazy at first and only gradually becomes clearer. The "clarification" can be markedly



accelerated if E asks about specific experiences which actually happened. It may continue until S has complete recall, or he may find that only some items come to mind while others remain hazy and distant. Characteristically, he will tend to recall hypnotic events that indicate a temporary lightening of trance: early challenge suggestions which startled him and almost interrupted hypnosis, or suggestions to which he did not respond successfully.

(3) Finally, a third group will not achieve recall at all, remaining amnesic even if pushed to remember. Here again one finds a variety of responses. For example, some Ss indicate that the whole experience seems to be on the tip of their tongue like a temporarily forgotten name. Freud's (1938) classic description of parapraxis is very appropriate for this type of S. He knows that things have happened; he has an empty space in his mind for the events, but he cannot fill it in. Other Ss, a small minority, show amnesia without any empty spot in memory at all.

What happens if amnesia is tested after a prolonged interval? The frequency with which amnesia occurs depends, of course, on the criterion by which it is measured and the degree to which it is challenged. In a study of posthypnotic suggestion by Damaser (1964), Ss to whom amnesia had been suggested returned to the laboratory a week after their hypnotic experience. They were interviewed by a new E, who was a research assistant. The assistant casually and informally engaged S in conversation about the previous week's experiment. A significant percentage of Ss reported some spontaneous recall during the week. Several had been reminded of a hypnotic experience by some event in their daily lives. Often complete recall followed shortly after the first "crack" in the amnesia.

In order to challenge the amnesia in those Ss where it was maintained, the interviewer acted as though she did not know what amnesia was, or that it could conceivably happen. She would ask naively: "What do you mean you don't remember? It happened only last week." Even under these circumstances, some Ss continued to maintain amnesia. It is possible that these Ss represented a qualitatively different group from the others; their behavior lends itself to an alternative explanation to be discussed later.

Except for this group of Ss who maintained complete amnesia, the reactions described are characteristic not only of amnesia but of all posthypnotic suggestions. The degree to which Ss carry out posthypnotic suggestions over long periods of time tends to follow a similar course, and extra-hypnotic challenge will interfere with their execution in the same way.



Conditions Maximizing the Probability of Posthypnotic Amnesia

The experienced hypnotist is able to predict with a high degree of accuracy whether a given S will develop posthypnotic amnesia when it is suggested. It will rarely be found in a S who fails to respond to challenge suggestions or hallucination items, and nearly always appears in the classic somnambulist. However, the probability of obtaining posthypnotic amnesia is not merely a function of overall depth of hypnosis. It is generally recognized among clinicians working with hypnosis that the events immediately preceding the suggestion of amnesia and awakening tend to be of particular importance. A S may have failed to respond to a number of suggestions early in the session, but he may nonetheless show amnesia if, before amnesia is suggested, he is then given a series of suggestions which he can successfully follow. On the other hand, the S who has successfully carried out a wide variety of difficult suggestions but fails to carry out a particular item just before the amnesia suggestion will usually not respond to it. It is as if the critical variable were the depth of hypnosis at the time amnesia is suggested.

In a recent study in our laboratory, Field, Evans, and M. T. Orne (1965) administered two tape-recorded modifications of the Harvard Group Scale of Hypnotic Susceptibility (Shor & E. Orne, 1962), one with the items in an ascending order of difficulty, the other using a descending order of difficulty. Although the groups achieved mean scores which did not differ significantly (a curious result in itself), the group which had the easier items last showed significantly more posthypnotic amnesia than the group in which the last items were the more difficult ones. This supports the view that success and failure immediately before the amnesia suggestion can affect the probability of amnesia, independent of the total response of S.

Posthypnotic suggestions in general are similar to posthypnotic amnesia and different from many other kinds of hypnotic items in this regard. They, too, apparently depend more upon the level of hypnosis at the time than upon the general responsivity of S. The relationships among order of presentation, difficulty of items, and type of hypnotic items used, is an area which will need future elaboration.

Facilitating Amnesia

Another link between amnesia and other posthypnotic behavior is the observation that it can be facilitated by several techniques. For example, the hypnotist can tie it to another suggestion which he knows S can carry out. A S who is successful in carrying out a challenge catalepsy suggestion of his right arm may be told that his arm will



continue to remain stiff even after he awakens, and that he will be unable to recall what has happened as long as it remains stiff. Another S who has been taught to respond to a posthypnotic cue to enter hypnosis might be told, "When you awaken, you will recall nothing of what has happened. Any memory that comes to mind for any of the events which occurred during hypnosis will immediately cause you to fall asleep again." In some Ss, at least, the amnesia which is induced in this way seems similar to that found in the relatively few natural somnambulists who are amnesic the very first time hypnosis is experienced.

Specific Amnesias

Perhaps one of the most striking phenomena which would place posthypnotic amnesia in the same category as other posthypnotic suggestions is the possibility of suggested specific amnesias. Any S who shows good posthypnotic amnesia can also be told to forget a specific name or event, or a class of events, names, or objects. I have been particularly interested in the suggestion to forget a number. Thus an individual may be told that the number 3 is going to disappear from his mind and that, on awakening, he will be unable to think of the number 3 in any way, shape, or manner; it will simply not exist for him. When the S awakens, and is asked to count, he will count 1, 2, 4, 5, etc. If he is told to continue, he will count 22, 24, 25, 26, 27, 28, 29, 40, and so forth. Instructed to count the fingers of his hand, he will be troubled to find there are six rather than five. He will become incapable of doing the simplest kind of arithmetic. If asked the sum of 6 and 7, he may answer 12. When he is asked the sum of 6 and 6, he will also answer 12. By this time he will show considerable puzzlement. Continued inquiry with simple addition problems will usually lead to confusion and discomfort like that observed with any repetitive and incongruous posthypnotic suggestion. The quality of the experience described is, however, similar to that of more general posthypnotic amnesia.

I have tried this suggestion with many Ss, including some who have had very sophisticated mathematical backgrounds. They tend to become somewhat more troubled than the others, presumably because mathematical ability is more important to them.

Amnesia and Posthypnotic Suggestions

If amnesia is simply a subclass of posthypnotically suggested behavior, it should be related to performance on other hypnotic tasks. Indeed amnesia was once believed essential to obtain any posthypnotic



behavior. It is recognized today that this is not the case, but a correlation exists nonetheless. There are few Ss who show good amnesia without the ability to respond to posthypnotic suggestions, but many who carry out posthypnotic suggestions without amnesia. However, Damaser (1964) found that Ss with recall show less persistence of posthypnotic behavior than those without. Moreover, the posthypnotic behavior of Ss with recall differs from that of amnesic Ss. Instead of rationalizing their behavior, they will recall the suggestion and describe a compulsion. Sometimes Ss with good recall seem to have a temporary lapse of memory when a posthypnotic cue is given. They will carry out the suggested behavior and realize only when half-way through that it is a posthypnotic response. Thus, while there is no invariant association between amnesia and other posthypnotic behavior, some relation seems to exist.

Factor analytic studies by Thorn (1961), Hammer, Evans, and Bartlett (1963), Evans (1963; 1965) and, more recently, Hilgard (1965) have shown that there are several clusters of hypnotic responsiveness. The first cluster consists of ideomotor behavior. If S responds to one ideomotor suggestion, he will usually respond to others, but these responses do not predict their reactions to other kinds of suggestions very well. The challenge items comprise a second group: Ss who respond to one challenge suggestion will usually respond to others. Finally, a third cluster includes hallucination, posthypnotic suggestion, and amnesia. Responsivity to anyone of these is more closely correlated with the others than with response to challenge or ideomotor items.

The Retroaction Studies

A final bit of evidence for the suggestion theory derives from a line of work which was originally intended to validate the dissociation hypothesis instead. Several studies have attempted to demonstrate dissociation by using the retroactive inhibition effect in nonsense syllable learning. If a S is asked to learn List A, then learns another list, B, which contains different nonsense syllables, and is finally tested on A, there will be appreciably less recall than if List B had been omitted and S had carried out some unrelated activity for a similar period of time. It appears that learning similar material interferes retroactively with the memory of the original list. This phenomenon is familiar in language learning. An individual who knows French and subsequently learns Spanish may find that his memory for French has been seriously impaired thereby.

To test the dissociation view of posthypnotic amnesia, S may learn



List A in the waking state, List B in hypnosis (inducing amnesia for this experience) and subsequently be tested on List A in the waking state. If hypnotic amnesia is a true dissociation of states, one might expect less retroactive inhibition, and hence more recall, under these circumstances than when the interfering list is learned in the normal state. Some authors (Messerschmidt, 1927; Nagge, 1935; Takahashi, 1958) have claimed to find this effect while others have not (Huse, 1930; Mitchell, 1932). When we tested it carefully in our laboratory, we found that the advantage for the hypnotic group occurred only as a bias effect. With adequate control for bias, no blocking of retroactive inhibition due to hypnosis was found. This result need not embarrass a dissociation theory seriously, as has been argued by Hammer (1961) and by Evans (1965). After all, even material (like List B) which is not presently available to consciousness must be stored somewhere if it is recoverable, so it may well interfere with similar material that is in consciousness. But at least there is no positive evidence for anything more than suggestion in these data.

Posthypnotic Amnesia as a Qualitatively Different Event Spontaneous Amnesia

In these arguments for the suggestion theory, we have failed to distinguish between suggested posthypnotic amnesia and that which occurs spontaneously. But in many deeply hypnotized Ss, amnesia seems to appear without any explicit suggestion. Should we dismiss this observation by arguing in terms of "implicit suggestion"? Does it arise because Ss expect to be amnesic, or because some hypnotic procedures, such as the frequent reference to sleep, function as demand characteristics? This rather glib explanation does not appear to do justice to what occurs. The Ss who respond most dramatically, who seem to enter hypnosis most rapidly, and who give the strongest impression of being somehow in a special state, are the ones most likely to show spontaneous amnesia. And, while it is true that the sophisticated college students used in most laboratories know a great deal about hypnosis, much of the early work in hypnosis was done with a naive population. These early workers were the most adamant in maintaining that posthypnotic amnesia occurs spontaneously whenever deep hypnosis is induced. One can even argue that the expectations of our modern Ss have directly reduced the incidence of spontaneous amnesia. The events of the hypnotic trance may be better remembered now because they seem less alien and mysterious.

Some striking evidence in this regard is available from cross-cultural studies. Hypnosis-like states have been reported in a large number of



primitive societies. They usually serve quasi-religious or ritualistic functions, and they may provide a culturally sanctioned mechanism for the handling of otherwise unacceptable impulses. Trance and dance in Bali, voodoo in Haiti, spirit possession among the Eskimos are typical examples. In every instance, the individuals involved have amnesia for the events which occurred during the trance or "spirit possession." Similarly, in American Pentecostal Churches, when worshippers are said to "get the Holy Ghost," amnesia is the rule. The fact that trance phenomena in totally unrelated and widely separated cultures all show amnesia supports the belief that spontaneous posthypnotic amnesia should not be dismissed simply as an artifact of S expectations. It is noteworthy also that similar amnesias occur in many functional pathological states, such as multiple personality.

Sleep Suggestion

If we consider the possibility that the thought process is altered during hypnosis in some way (cf. M. T. Orne, 1959), then we have theoretical grounds for supposing that spontaneous amnesia can be something other than implicit suggestion. Perhaps suggested amnesia, with all its complexities, bears only a phenotypic and not a genotypic resemblance to the kind of amnesia which occurs spontaneously. Recent work in our laboratory bears on this possibility (Cobb, Evans, Gustafson, O'Connell, M. T. Orne, & Shor, 1965; Evans, Gustafson, O'Connell, M. T. Orne, & Shor, 1965). We have been successful in giving suggestions to naive, unhypnotized Ss during Stage 1 sleep. EEG records showed that S slept uninterruptedly while being told, say, that his nose would itch every time E would say the word "itch." In later Stage 1 periods during the same night, when "itch" and other cue words were administered, many Ss carried out the suggestions without awakening and without any modification of the sleeping EEG. The next morning they characteristically had no recall either of the suggestions or of their reaction. When these Ss were given an association test which included the cue words, there was no evidence of recognition. Further, when they returned to the laboratory for another sleep session, and the words were again presented during Stage 1 periods without repeating the suggestion, appropriate behavioral responses were elicited. This phenomenon seems to fit our definition of amnesia: there is no recall in the waking state, but the memory can be reinstituted in the original state.

These studies were not carried out in hypnosis but rather in normal, physiological sleep. We are investigating the relations between the sleep-suggestion phenomenon and hypnosis, and so far many questions



remain unanswered. These studies do provide a hint, however, that it may be possible to have evidence of recall in one state with truly spontaneous amnesia in another.

If spontaneous dissociative amnesia does occur, it may be because the thought processes in the two states are different. Such a formulation would be consistent with the finding reported by the author (1959) earlier on the trance logic of hypnotized Ss. It has been discussed by Gill and Brenman (1959) in a framework which conceptualizes hypnosis as regression in the service of the ego. The general notion that Ss with a given style of thought cannot easily recall events which they conceived in an earlier style has been best developed by Schachtel (1947), and was stressed by Reiff and Scheerer (1959). There is little laboratory research in this area, but much clinical material is relevant.

Clinical Observations

Anyone who uses hypnosis as a therapeutic tool finds that some patients recall highly meaningful, emotionally charged material during hypnosis. The more extreme the affect, the more meaningful the material, the more is the patient's tendency to "relive" rather than merely recall his experience. Typically he will be there, describing what appear to him as primary sensory perceptions. The language will be direct, simple, appropriate to the time of his life when the event occurred, and accompanied by the affect suitable to the situation. When the patient is brought back to full awareness of his surroundings and awakened, he usually has spontaneous amnesia for the dramatic episode. This happens regardless of whether he is given suggestions to forget everything or to remember everything. I have repeatedly observed patients who had excellent recall for events which took place in hypnosis with the exception of these highly charged regressive episodes. Over a period of the next few sessions, patients gradually recover, as memories, the material which they relived in hypnosis. Even though they have amnesia for the experience, the fact that it has been shared with the therapist somehow facilitates the working-through of this material.

These clinical observations are usually conceptualized in terms of repression, where it is assumed that the patient cannot tolerate certain particularly traumatic events in consciousness. Perhaps it will be more helpful to say that the events are not recallable because they have not been translated into the schemata of thinking used by the individual when awake. The additional time which the patient needs before he can really recall this material and remember "owning" it,



as it were, may be due to the difficulty of translating a primary experience into the language of current memory. Such a view would fit the observation that the memory, when it becomes fully elaborated, is described in very different terms from the original cathartic experience.

Other clinical data also support this interpretation. I have often used a technique of tape-recording interviews with patients who do not easily recall their earlier therapy sessions. These patients may return to the office between sessions and listen to the tape of the preceding session. This procedure has considerable clinical utility with patients who have difficulty establishing the continuity from session to session. As a rule, patients have no difficulty in recognizing and assimilating the material on the tape, even when the session recorded is a hypnotic one. An exception to this rule occurred with two patients who happened to undergo spontaneous regression during some of their recorded interviews. In both instances they described being unable to remember the events that they had relived during the session, even after hearing them on tape. Somehow the events were alien, and not part of their own memory. If anything, this confrontation seemed to disturb rather than facilitate the integration of this material into their current memory.

Source Amnesia

The phenomenon of "source amnesia" may also be partially understood in terms of structurally distinct modes of thought. Thorn (1960), Evans (1965), and Evans and Thorn (1963) have described this phenomenon. During hypnosis, Ss were provided with certain little-known facts, such as that amethyst turns yellow when it is heated. On awakening, some Ss who claimed to have no memory of hypnosis events still knew the facts themselves, responding correctly to questions about the color of heated amethyst. Asked how they knew, Ss resorted to rationalization, perhaps saying that they must have read it in the newspaper.

There seems to be two separate items of memory: (a) the information itself and (b) the context in which one has learned the information. It is possible to retain the information and forget where it has been obtained--an interesting effect which can lead to complications when it occurs among scientists.

The phenomenon is familiar to all of us in at least one context: much of the knowledge acquired during childhood, perhaps with a different set of schemata or a different logic, has this character. We speak English, recall when Columbus discovered America, and know



how to distinguish the sexes, all without any idea how we got the information involved (e.g. Bergson, 1911; Reiff & Scheerer, 1959).


It would be comforting to integrate this wide variety of observations under a single rubric, but it does not seem possible to do so. Many features of posthypnotic amnesia indicate that it is a particular type of posthypnotic suggestion, but others, especially those associated with very profound hypnotic experiences, do not. In these latter cases, amnesia may be due to a functional separation between different types of mental processes, though hard evidence for such a point of view is even harder to come by.

There are a number of questions in this area that seem readily answerable by empirical research. For example, we need a careful delineation of the conditions which maximize the probability of post- hypnotic amnesia along with a detailed study of the quality of amnesia induced. The relation between amnesia and normal forgetting should be studied: are the mechanisms of forgetting material unavailable to consciousness different from those involved in forgetting ordinary material? Careful studies of techniques which can be used in the waking state to bring about recall in instances of spontaneously occurring posthypnotic amnesia may prove of considerable interest and importance for an understanding of psychotherapy. While some studies of hypnotic recall have been done, these have tended to address themselves to comparing waking and hypnotic recall in quantity rather than in quality. In all such work, it is essential to discriminate between verbal inhibition and subjectively real amnesia.

I suspect that at least two vastly different processes may be involved in posthypnotic amnesia, one of which is more frequently observed in laboratory situations and the other in clinical ones. It would be misleading to dismiss the possibility of multiple mechanisms only because the evidence for one is swamped by the preponderance of the other in certain situations. Thus, until further evidence is available, it would seem judicious not to apply the law of parsimony to this phenomenon.


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Sobre los Mecanismos de la Amnesia Post-Hipnotica

Martin T. Orne

Resumen: Revisanse las evidencias clinicas y experimentales de la amnesia post-hipnotica. En lugar de postular un solo mecanismo que pudiera dar



cuenta de la existencia de este fenomeno, el autor propone dos, los cuales, a primera vista, pueden parecer contradictorios. Por una parte postula que, al igual que cualquier otra experiencia hipnotica sugerida, la amnesia tambien lo es, es decir, es el producto de una sugestion post-hipnotica implicita o explicita. Por otra parte, pastula que la amnesia podria verse como una forma de disociacion. Un mecanismo posible para explicar tal disociacion seria la diferencia fundamental existente entre la estructura del pensar en hipnosis propiamente tal y el tipo de pensar durante la vigilia. Asi las cosas, la amnesia seria un fenomena independiente de la sugestion y, por ello, diferente de casi todos los otros fenomenos observables en hipnosis. En la situacion experimental el mecanismo predominante seria el sugestivo. En la situacion clinica, el disociativo.

Uber den Mechanismus der posthypnotischen Amnesie

Martin T. Orne

Abstrakt: Klinische und experimentelle Beobachtungen uber posthypnotische Amnesie werden besprochen. Anstatt einen einzigen Mechanismus fur dieses Phanomen zu postulieren werden zwei Moglichkeiten dargestellt, die scheinbar widersprechend sind. (1) Posthypnotische Amnesie ist im wesentlichen nicht verschieden von anderen hypnotische suggerierten Erlebnissen. Das heisst, es kann als die Folge eines ausdrucklichen oder inbegriffenen hypnotischen Befehls betrachted werden. (2) Posthypnotische Amnesie kann die Folge einer Art Dissoziation sein. Ein moglicher Mechanismus von so einer Dissoziation konnte ein grundsatzlicher Unterschied in der Struktur der Denkart in der Hypnose im Gegensatz zu dem im Wachzustand sein. In diesem Sinne sollte posthypnotische Amnesie unabhangig von Suggestionen auftreten und verschieden von den meisten anderen hypnotischen Phanomenen sein. Der erste Mechanismus scheint haufiger in experimentellen Situationen vorzukommen, wahrend der zweite mehr in klinischen Situationen zu finden ist.

The preceding paper is a reproduction of the following article (Orne, M.T. On the mechanism of posthypnotic amnesia. International Journal of Clinical and Experimental Hypnosis, 1966, 14, 121-134.). It is reproduced here with the kind permission of the Editor-in-Chief of The International Journal of Clinical and experimental Hypnosis.