Orne, E. C., Whitehouse, W. G., Dinges, D. F., & Orne, M. T. Memory liabilities associated with hypnosis: Does low hypnotizability confer immunity? International Journal of Clinical and Experimental Hypnosis, 1996, 44, 354-369.
University of Pennsylvania School of Medicine
Abstract: Retrospective analyses of data from the authors' program of
research on hypnosis and memory are presented, with special emphasis on effects
observed among low hypnotizable individuals. In Experiment I, participants completed
seven forced-recall trials in an attempt to remember a series of pictures that
had been shown 1 week earlier. For half the participants, the middle five trials
were carried out using hypnotic procedures; the remaining participants performed
all recall attempts in a motivated waking condition. Hypnosis failed to enhance
correct recall for either high or low hypnotizable participants beyond the hypermnesia
and reminiscence effects associated with repeated retrieval attempts over time.
However, whereas high hypnotizable participants produced substantial numbers
of confident recall errors (i.e., intrusions) independent of the use of hypnosis,
low hypnotizable participants exposed to hypnotic procedures reported significantly
more intrusions than their counterparts in the waking condition. In Experiment
2, participants were asked to identify whether specific recollections, reported
during two forced-interrogatory recall tests conducted 1 week earlier, had originated
in the first or second of those tests. A general bias to misattribute previously
reported recollections to the first of two recall occasions was observed; however,
the effect was greatest among low hypnotizables who had undergone the second
recall attempt in hypnosis. The findings imply that highly hypnotizable individuals
are not unique in their vulnerability to distortions of memory induced by hypnotic
techniques. Individuals of lesser hypnotic capacity also manifest memory alterations
when exposed to such procedures.
Modern scientific studies of hypnosis routinely take into account individual differences in hypnotic responsivity when assessing the out-
Manuscript submitted November 17, 1995; final revision received May 10, 1996.
1 This research was supported in part by Grants MH19156 and MH44193 from the National Institute of Mental Health, U.S. Public Health Service; in part by Grants 82-IJ-CX- 0007 and 87-IJ-CX-0052 from the National Institute of Justice, U.S. Department of Justice; and in part by a grant from the Institute for Experimental Psychiatry Research Foundation.
2 Requests for reprints should be addressed to Emily Carota Orne, Institute for Experimental Psychiatry, 1955 Locust Street, Philadelphia, PA 19103.
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355 LOW HYPNOTIZABILITY AND MEMORY LIABILITIES
comes of hypnotic treatments. The development of psychometrically sound measures of hypnotizability has led to a better understanding of the social, motivational, and phenomenological constituents of the hypnotic response, in addition to helping to delineate the range of therapeutic benefit that may be derived from the clinical use of hypnotic procedures.
Unfortunately, emphasis on the importance of hypnotizability in hypnosis research appears to have trained a spotlight on highly hypnotizable individuals, to the virtual neglect of individuals endowed with lesser hypnotic capacity. Indeed, some hypnotic phenomena, assumed to be the province of the "hypnotic virtuoso," are often studied using only highly responsive individuals (e.g., Laurence & Perry, 1983). Low hypnotizables are typically relegated to control conditions. In some studies, they may receive the same instructions as "highs" to document the involvement of genuine hypnotic processes in the distinctive behavioral response of highly hypnotizable participants; in others, low hypnotizable individuals may be asked to simulate being hypnotized as a means to determine the degree to which contextual factors shape responses to hypnotic suggestion (Orne, 1972; Sheehan & Perry, 1976). Few studies have explicitly examined the effect that hypnotic procedures might have on relatively unhypnotizable individuals.
Nevertheless, there is ample clinical evidence that the efficacy of hypnotic procedures is often unrelated to an individual's hypnotic talent (e.g., Barber, 1991; Wadden & Anderton, 1982). This is not to say that the changes achieved necessarily rely on the same processes for persons with differing levels of hypnotizability. In some circumstances, the therapeutic benefit of a hypnotic intervention can be traced to nonspecific aspects of the therapy, yet the treatment response may be no less profound. The principal objective of this article is to provide evidence that hypnotic procedures can have an important effect on the response of even low hypnotizable individuals, particularly in circumstances where the response does not require extraordinary hypnotic talent.
Our focus is on the consequences of employing hypnosis in the service of memory retrieval. This is a common therapeutic use of hypnosis (Brown & Fromm, 1986; Orne, Dinges, & Bloom, 1995), as well as a popular forensic investigative application of the technique (Reiser, 1980). In addition, a great number of scientific studies have been carried out over the past 2 decades to clarify the mechanisms of hypnotic memory facilitation (see Orne, Whitehouse, Dinges, & Orne, 1988, for a review). The typical finding in much of this research is that what appears to be an enhancement of recall by hypnosis is actually an increase in the quantity of information reported (i.e., productivity), which consists of both new accurate and inaccurate material. In addition, the level of confidence associated with hypnotically facilitated memory reports is often escalated, and individuals exposed to hypnotic procedures may
356 EMILY CAROTA ORNE ET AL.
have increased difficulty differentiating between factual and fictional details.
By and large, these characteristics of hypnotic recall are most pronounced among highly hypnotizable persons. We here report new data distilled from two previous studies conducted by our laboratory (i.e., Dinges et al., 1992; Whitehouse, Orne, Orne, & Dinges, 1991) that document the vulnerability of even low hypnotizable persons to experiencing distorted recollection when exposed to hypnotic memory retrieval procedures. It is relevant to note that in each of these studies, the experimenter was blind to the participants' hypnotizability. Additionally, in an effort to capture the essence of applied settings, the experimenter conveyed strong positive expectations that hypnosis would provide the means to access memories that had hitherto been difficult to retrieve. In considering the implications of these findings, we will attempt to characterize sources of motivation, perceived self-efficacy, and potential phenomenological validating mechanisms that may increase hypnotic responsiveness, both in research and, perhaps to an even greater extent, in applied situations.
EXPERIMENT 1: ONE-WEEK DELAYED MULTITRIAL FORCED RECALL OF PICTORIAL STIMULI
The major findings of this experiment were previously reported by Dinges et
al. (1992). In the current article, we examine exclusively measures of cumulative
correct recall over trials and corresponding cumulative confident recall errors
(i.e., intrusions). The slope of such cumulative memory functions reflects the
amount of "new" correct or incorrect material provided on each trial
and is unaffected by failures to repeat responses on later trials. Thus, cumulative
measures provide a compre-hensive "record" of an individual's memory
productions over a period of time. Of particular interest to our present purpose
is whether the use of hypnosis with relatively unhypnotizable participants increases
cumulative correct or incorrect recall relative to that produced by low hypnotizable
individuals in a motivated waking condition.
METHOD
Participants
Out of an initial undergraduate volunteer sample of 428 individuals, 48 were selected for scoring in the extreme ranges of both the Harvard Group Scale of Hypnotic Susceptibility, Form A (HGSHS:A; Shor & Orne, 1962) and the Stanford Hypnotic Susceptibility Scale, Form C (SHSS:C; Weitzenhoffer & Hilgard, 1962). Twenty-five participants (12 male, 13 female) were classified as low hypnotizable (SHSS:C = 0-4), and 23 (10 male, 13 female) were classified as high hypnotizable (SHSS:C = 8-12).
357 LOW HYPNOTIZABILITY AND MEMORY LIABILITIES
Procedure
The initial session involved the tape-recorded administration of the HGSHS:A. Following this, participants were engaged in other activities (i.e., watching a film and completing research questionnaires), which were unrelated to the focus of the current study, while the HGSHS:A response booklets were unobtrusively scored. Participants who scored below 6 and above 8 on the HGSHS:A were invited to participate in two individual follow-up sessions, although they were informed that a computer had randomly selected them for further participation.
During the first individual session, participants were told that they would view a series of 40 slides that they would later be asked to recall. The slides were black-and-white line drawings of common objects selected from the set developed by Erdelyi and Becker (1974). Slides were presented at the rate of once every 5 seconds, and participants were asked to name aloud the object in each slide while the experimenter recorded the specific label given to every item. Immediately afterward, a 5-minute forced-recall test (R1) was administered, in which participants were given a sheet of paper consisting of 40 blank lines and were told to fill in every line with the name of one of the objects they had just seen. When they felt that they could not remember any further items, they were to draw a line under the last entry and begin to fill in the remaining blank spaces with their best guesses. If any new items occurred to them during this guessing section, they were instructed to distinguish them from guesses by placing a check mark next to those items. Following this, participants were introduced to a second experimenter, who administered the SHSS:C. To keep the motivation of low hypnotizable participants on par with that of high hypnotizables, we adopted the recommendation by Weitzenhoffer and Hilgard (1962) to terminate the test after three failed items. On completion of the SHSS:C, appointments were made for the third and final session, 1 week later.
During the final session, participants were introduced to a new experimenter, who was unaware of both the specific slides that were shown and the participants' hypnotizability scores. The experimenter explained that the purpose of the study was to investigate certain procedures that would help to refresh their memory for the pictures that were presented in the previous week's session. Following these introductory comments, participants were given instructions for completing a 5-minute forced-recall test (R2), which was identical to the prior R1 test conducted 1 week earlier.
At the conclusion of the R2 waking baseline test, the experimental treatments were introduced. Participants in the waking condition (n = 24) were told that periodically they would be engaged in a distracting activity (i.e., a visual reaction time [RT] task) that would make it easier to recall the pictures when they next tried to remember them. They were then given instructions for the 10-minute visual RT task, which was
358 EMILY CAROTA ORNE ET AL.
administered twice -- prior to the next recall attempt (R3) and again prior to R8. At other times, participants were instructed to spend time relaxed, with their eyes closed, thinking about the pictures until they were told to stop. These "think" intervals each lasted 2 minutes and occurred prior to R4, R5, R6, R7, and following the visual RT task, prior to R8.
The participants in the hypnosis condition (n = 24) were informed that hypnosis would be used to help them better remember the pictures by allowing them to focus their minds and to reexperience the previous session, seeing the slides being shown again in their minds and hearing themselves name the objects. The hypnotic induction was a modification of that used with the SHSS:C, which incorporated a number of direct suggestions for enhanced recall. The induction preceded R3 and was reinforced with deepening suggestions given prior to R4 and R6. Following R7, participants were aroused from hypnosis with suggestions that they would continue to be able to remember all of the pictures that they recalled prior to and during hypnosis. They were then given instructions for the visual RT task, which was administered for a 10-minute period and followed by a 2-minute think interval; R8 was then carried out in the waking condition.
RESULTS
Factorial analyses of variance (ANOVAs) with hypnotic ability (low vs. high) and Session 2 recall treatment (hypnosis vs. waking) as between-subjects factors, found no significant intergroup differences in correct recall on either the immediate, F(l,44) = 1.99, p > .10, or 1-week delayed (F < 1.0) baseline recall tests (i.e., R1 and R2, respectively). Similarly, the level of confidently reported incorrect recall did not differ on either of the two baseline tests (both Fs < 1). Thus, there were no baseline differences among the groups.
Table 1 summarizes the mean cumulative correct and cumulative incorrect recall levels obtained during waking trials R2 and R8, which represent pre- and posttreatment assessments, respectively. A repeated-measures ANOVA conducted on cumulative correct recall found only the expected significant main effect of trials, F(l, 44) = 358.37, p < .001, indicative of normal reminiscence across trials. There were, however, no differences due to hypnotizability, hypnosis versus waking treatment, or their interactions (Fs < 1.03).
A similar repeated-measures ANOVA carried out on the cumulative number of intrusions reported during trials R2 and R8 found a significant between-subjects main effect of hypnotic ability, F(l, 44) = 4.68, p < .05. As shown in Table 1, this effect was due to an overall greater number of intrusions reported by high hypnotizable participants than by low hypnotizables. In addition, the Hypnotizability x Trials interaction was also reliable, F(l, 44) = 5.99, p < .05, indicating that high hypnotizables
359 LOW HYPNOTIZABILITY AND MEMORY LIABILITIES
produced a larger cumulative increase in intrusions from R2 to R8 than did low hypnotizables.
Because the focus of this report concerns specifically the effect of hypnotic retrieval techniques on the recall accuracy of persons of low hypnotic ability, we also conducted a repeated-measures ANOVA to examine cumulative intrusions among low hypnotizables across trials R2 through R8 (see Figure 1). This analysis revealed significant main effects for hypnosis versus waking treatment, F(l, 23) = 4.82, p < .05, and trials, F(6, 138) = 16.97, p < .001), as well as a significant interaction of the two factors, F(6, 138) = 2.82, p < .02. Decomposition of this interaction using simple-effects tests (alpha = 0.05) showed that whereas low hypnotizables in the hypnosis and waking conditions did not differ significantly in number of intrusions reported on the R2 waking baseline trial, reliable differences were present in each trial thereafter. In particular, the introduction of hypnosis led to an immediate 144% increase in cumulative confident errors on R3, whereas the cumulative error rate of waking participants increased by only 55% for the same trial, F(l, 23) = 6.02, p < .05. This early difference was maintained throughout the remaining trials, with participants in the hypnosis condition averaging a 0.5-item trial-to-trial increase in new intrusions and those in the waking condition averaging a 0.3-item increase over successive trials.3
360 EMILY CAROTA ORNE ET AL.
DISCUSSION
The level of cumulative correct recall clearly increased across trials as a function of normal hypermnesia and reminiscence processes. However, neither hypnotizability nor the hypnosis treatment had any discernible supplementary effect on correct recall. This finding is in agreement with our earlier observation (Whitehouse, Dinges, Orne, & Orne, 1988) that when care is taken to control any possible report criterion differences between hypnotic and nonhypnotic conditions (e.g., by employing a forced-recall procedure), there is no evidence of recall enhancement unique to hypnosis.
In contrast to its benign effect on correct recall, hypnotizability was an important determinant of the number of confidently reported recall errors. Thus, high hypnotizables generated significantly more new intrusions overall, and at higher rates across trials, than did low hypnotizables. Moreover, for high hypnotizables, the effect was not confined to the hypnosis treatment. In this regard, it is possible that features of the waking condition, such as the suggestion that the visual RT task and relaxing for 2-minute "think" intervals with eyes closed would facilitate recall, and the high degree of repetition of the procedures, might have
361 LOW HYPNOTIZABILITY AND MEMORY LIABILITIES
inadvertently created an implicit “hypnotic” context for some high hypnotizable participants.
Although the number of recall errors was greater for high hypnotizables, the use of hypnosis had a distinctive effect in escalating the cumulative error rate among low hypnotizable participants. The majority of these new intrusions occurred on the very first hypnosis trial, with only modest increments thereafter, which did not differ from the error rates of waking participants, produced during subsequent trials. It is noteworthy, however, that the initial large increase in errors that occurred with the introduction of hypnosis was of the same magnitude as that produced by high hypnotizables during their first hypnosis trial. This suggests that hypnosis can induce significant memory alterations and that vulnerability to this effect may be particularly heightened, for low and high hypnotizable individuals alike, when hypnotic procedures are first introduced.
EXPERIMENT 2: ATTRIBUTIONS REGARDING THE CONTEXT OF PRIOR RECOLLECTIONS
This experiment investigated the effect of the use of hypnosis for memory retrieval on the subsequent ability of participants to discriminate whether specific recollections antedated the hypnotic intervention. This issue has particular relevance to judicial standards regarding the admissibility of hypnotically derived testimony: Recognizing the considerable scientific evidence supporting the unreliability of memories recovered using hypnosis, a number of jurisdictions have taken the position that a previously hypnotized witness is unfit to testify. An alternative, and less extreme approach adopted by a few courts, has been to allow the witness to testify only to recollections that were available prior to hypnosis. In the absence of objective documentation (e.g., an audiotaped or videotaped prehypnotic interview), however, the witness alone must bear responsibility for distinguishing between prehypnotic remembrances and information acquired during or following hypnosis.
Experiment 2 sought to determine whether individuals can make such a discrimination reliably by examining whether previously hypnotized and nonhypnotized individuals can correctly classify the temporal context of recollections they reported 1 week earlier. During the prior session, a random subset of participants answered questions about a previously viewed film once in the waking condition and a second time in hypnosis, whereas the remaining participants were questioned both times in the waking condition. The data reported here were derived from a previously published study by Whitehouse et al. (1991).
362 EMILY CAROTA ORNE ET AL.
METHOD
Participants
Eighty-one university undergraduate volunteers (34 male, 47 female) were selected from a larger sample (n = 428) for scoring consistently in the extreme ranges of the HGSHS:A (low = 0-5; high = 9-12) and the SHSS:C (low = 0-4; high =8-12). The current sample consisted of the 69 participants from Whitehouse et al. (1991) and an additional 12 participants.
Procedure
The experiment consisted of three phases. In the initial group session, the tape-recorded HGSHS:A was administered, followed by a 10-minute intermission (which permitted the HGSHS:A response booklets to be scored unobtrusively). Participants then returned to their seats to view the stimulus film -- a 15-minute color presentation on poster-making techniques titled "Posters" (distributed by AIMS Media, Van Nuys, CA) -- after which they completed a 20-item multiple-choice recognition test on its content. Those individuals who met HGSHS:A criteria for further participation were scheduled for an individual session 4-12 days later. A second copy of the 20-item multiple-choice test was completed and returned by mail 4 days after the group session.
During the second session, participants were twice asked a tape-recorded series of 40 questions (different from the 20 recognition test items given previously) about the film. The response format was a modification of the forced-recall protocol, in which participants were instructed to answer each question, by guessing if necessary, and to rate their confidence in the accuracy of each response using a 4-point scale (0 = not confident, just guessing; 3 = very confident, certain). The first such recall test (R1) was conducted in the waking condition for all participants. Following this, participants were randomly allocated to undertake the second recall test (R2) in either hypnosis (n = 46) or the waking condition (n = 35). The hypnosis treatment consisted of a 15-minute tape-recorded induction procedure that included suggestions for memory enhancement. The waking condition involved a 15-minute tape-recorded auditory signal-detection task that concluded with the same suggestions for facilitated recall given to participants in the hypnosis condition. All participants were then introduced to a second experimenter, who administered the SHSS:C (using the early termination modification previously described to promote a more positive experience with hypnosis for low hypnotizable participants), and scheduled them for a third session, 1 week later.
In the final session, participants were engaged in a series of cognitive tasks that were unrelated to the focus of the present study, followed by a comprehensive postexperimental interview. During the course of this
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interview, participants were given a questionnaire containing four of the questions about the film to which they had responded twice (during R1 and R2) in the previous week's session. Along with these questions were the specific verbal responses each participant had given on one of those two occasions; two of the responses were first mentioned during R1 and two were given for the first time during R2. Participants were asked to identify the occasion (R1 or R2) on which the particular answers were first given and to indicate their confidence (using the 0 to 3 rating scale described earlier) in these source attributions. The two responses selected from a participant's R1 protocol were matched as closely as possible to those selected from R2 on the basis of confidence ratings assigned at the time they were originally given. In addition, one response from each recall test was correct, and the other was incorrect. These precautions were taken to ensure that participants would not attribute responses to R1 or R2 on the basis of earlier confidence. In addition, participants were not informed of the proportion of responses drawn from each recall test, or that any of their answers had been incorrect.
RESULTS AND DISCUSSION
There were no differences between groups on either of the 20-item recognition tests given immediately after the film and again 4 days later (both Fs < 1.0). Nor did the groups differ in terms of correct recall produced during the baseline R1 waking recall test (F < 1.0). Similarly, both hypnosis and waking treatments were associated with an increase in correct recall (i.e., hypermnesia) from R1 to R2, F(l, 77) = 31.46, p < .001; however, the magnitude of recall improvement was comparable between the two conditions (F < 1.0), indicating no unique hypnotic hypermnesia.
Table 2 summarizes the retrospective source judgments (R1 vs. R2) that participants made regarding specific recollections they reported during the previous session 1 week earlier. A crude index of the discriminability of the source of prior recollections would be provided if we obtained mean values of 2 for both R1 and R2 (as two responses were actually selected from each recall trial). However, it is clear from an inspection of Table 2 that all groups attributed more of their prior recollections to R1 than to R2. Binomial tests confirmed a significant bias favoring the attribution of responses to the R1 waking baseline trial, both for participants who performed R2 in hypnosis (z = 4.79, p < .001) and for those who performed both recall tests in the waking condition (z = 3.46, p < .001). A factorial ANOVA, conducted on the number of attributions to R1, found neither the hypnotizability nor hypnosis versus waking treatment effects to be reliable (both Fs < 1.0); however, the Hypnotizability x Treatment interaction was significant, F(l, 77) = 8.34, p = .005. Pairwise comparisons using Fisher's LSD procedure (alpha = 0.05) revealed that low hypnotizable participants who performed R2 in hyp-
364 EMILY CAROTA ORNE ET AL.
nosis exhibited an extreme bias to overattribute recollections to Rl, differing significantly from both high hypnotizables who underwent R2 in hypnosis and low hypnotizables who experienced both trials in the waking condition. Rl attributions by high hypnotizables in the waking treatment were intermediate and did not differ significantly from any of the other groups. A similar ANOVA, carried out on the confidence ratings assigned to participants' memory source attributions, failed to identify any significant differences among groups.
The findings document a general tendency, regardless of treatment, for individuals to retrospectively overestimate the amount of information retrieved from memory on an initial recall attempt. However, when hypnosis is used in a subsequent attempt to enhance retrieval, this attributional bias appears to be significantly exaggerated among low hypnotizable individuals. Although the mechanism responsible for an enhanced metacognitive distortion of this type requires further study, it is highly noteworthy that the effect was encountered among a sample of low hypnotizable individuals, who are often presumed to be unaffected by hypnotic procedures.
GENERAL DISCUSSION
We have reported observations from two studies that document the effect of hypnotic memory retrieval procedures on relatively unhypnotizable individuals. Both studies found indications of greater memory distortion -- in the form of increased memory intrusions and recall source misattributions -- associated with hypnotic relative to nonhypnotic conditions among low hypnotizable participants. In no case, even among high hypnotizables, was hypnosis responsible for the specific enhancement of accurate recall.
How are we to account for such effects of hypnotic procedures among individuals demonstrating low hypnotic ability? One possibility is that the apparent effects of hypnosis among low hypnotizable participants actually reflect a decrement in the motivation of participants in the primary comparison group, that is, low hypnotizable participants in the
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waking condition. The viability of this explanation, however, is challenged by several findings from these studies: (a) Baseline as well as asymptotic levels of correct recall were comparable among the treatment groups; (b) the magnitude of hypermnesia observed in the two studies did not differ among groups; and (c) the tendency to overattribute recollections to the first of two recall occasions was also observed among low hypnotizable participants who experienced only the waking condition. Thus, the suggestion that low hypnotizables exposed to waking recall procedures were less motivated than low hypnotizable participants exposed to hypnotic procedures is inconsistent with the observation that both groups exhibited the same memory phenomena.
On the other hand, a likely basis for the observed differences between low hypnotizable individuals exposed to hypnotic versus waking retrieval methods was the establishment of a conducive cognitive-motivational set. In these experiments, great care was taken to minimize feedback regarding each participant's level of hypnotic skill.4 For example, administration of the SHSS:C was terminated following three failed items, as suggested by Weitzenhoffer and Hilgard (1962), in an attempt to reduce any frustration or negative self-appraisal regarding hypnotic aptitude. In addition, the experimenters who conducted the memory retrieval sessions were blind to participants' hypnotizability, and they uniformly conveyed optimistic expectations and a plausible rationale for the efficacy of the hypnotic retrieval techniques to be employed. Thus, although falling short of the use of explicit verbal or surreptitious experiential manipulations to enhance motivation and response expectancy (e.g., London & Fuhrer, 1961; Wickless & Kirsch, 1989), the current studies provided multiple sources of contextual support for a positive response to hypnosis.
Given an appropriate level of motivation and positive expectations, the use of hypnosis for enhanced recollection may produce an increase in the reporting of veridical and/ or imagined "memories" that is independent of hypnotic talent. Clearly, hypnotic proceedings often rely on suggestions and cognitive processes that are not exclusively hypnotic in character (e.g., relaxation, mental reinstatement of the context of the to-be-remembered event, imagery). To the extent that relatively unhyp-
366 EMILY CAROTA ORNE ET AL.
notizable individuals are able to achieve, and receive validation for, suggested experiences of this sort within a context of hypnosis (cf. Orne, Whitehouse, Orne, & Dinges, 1996), they will be more likely to sustain efforts to uncover previously inaccessible memories.
Therapists who employ hypnotic techniques clinically can often scale the barrier of poor hypnotic capacity in much the same way -- by tapping those cognitive resources that are available and by tailoring their procedures to the patient's personality and emotional needs (cf. Barber, 1991). Thus, even relatively unhypnotizable patients may meet therapeutic objectives if they are protected from having to confront the limits of their hypnotic skills, or if their poor response can be rationalized as a manifestation of resistance or denial. As in the case of the laboratory experiments reported here, what appears to be important is the provision of a supportive context in which low hypnotizable individuals can succeed. But as our data indicate, when hypnosis, or the pressure to employ imaginative fantasy, is used to facilitate recollection --even with less responsive individuals -- the occurrence of memory distortion, being legitimized by the hypnotic context, can be considerable. Thus, the evidence is clear that hypnotic ability cannot be used as a barometer of the accuracy of hypnotically elicited recall. In particular, it would be folly to assume that because a person proves to be relatively unhypnotizable, that information obtained using hypnotic techniques is, therefore, more likely to be accurate. Great caution should be applied in all cases where hypnosis is used clinically or forensically for the purpose of reconstructing an accurate accounting of an individual's life events. Hypnotizability may not matter for the elicitation of additional "memories" by hypnosis, but if the truth value of the material is important, such can be ascertained only by independent corroborating evidence.
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Brown, D. P., & Fromm, E. (1986). Hypnotherapy and hypnoanalysis. Hillsdale, NJ: Lawrence Erlbaum.
Dinges, D. F., Whitehouse, W. G., Orne, E. C., Powell, J. W., Orne, M. T., & Erdelyi, M. H. (1992). Evaluating hypnotic memory enhancement (hypermnesia and reminiscence) using multitrial forced recall. Journal of Experimental Psychology: Learning, Memory, and Cognition, 18, 1139-1147.
Erdelyi, M. H., & Becker, J. (1974). Hypermnesia for pictures: Incremental memory for pictures but not words in multiple recall trials. Cognitive Psychology , 6, 159-171.
Laurence, J.-R, & Perry, C. (1983). Hypnotically created memory among highly hypnotizable subjects. Science, 222, 523-524.
London, P., & Fuhrer, M. (1961). Hypnosis, motivation, and performance. Journal of Personality, 29, 321-333.
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Orne, M. T. (1972). On the simulating subject as a quasi-control group in hypnosis research: What, why, and how? In E. Fromm & R. E. Shor (Eds.), Hypnosis: Research developments and perspectives (pp. 399-443). Chicago: Aldine-Atherton.
Orne, M. T., Dinges, D. F., & Bloom, P. B. (1995). Hypnosis. In H. I. Kaplan & B. J. Sadock (Eds.), Comprehensive textbook of psychiatry (6th ed.). Baltimore: Williams & Wilkins.
Orne, M. T., Whitehouse, W. G., Dinges, D. F., & Orne, E. C. (1988). Reconstructing memory through hypnosis: Forensic and clinical implications. In H. M. Pettinati (Ed.), Hypnosis and memory (pp. 21-63). New York: Guilford.
Orne, M. T., Whitehouse, W. G., Orne, E. C. & Dinges, D. F. (1996). "Memories" of anomalous and traumatic autobiographical experiences: Validation and consolidation of fantasy through hypnosis. Psychological Inquiry, 7, 168-172.
Reiser, M. (1980). Handbook of investigative hypnosis. Los Angeles: LEHI.
Sheehan, P. W., & Perry, C. (1976). Methodologies of hypnosis: A critical appraisal of contemporary paradigms of hypnosis. Hillsdale, NJ: Lawrence Erlbaum.
Shor, R. E., & Orne, E. C. (1962). Harvard Group Scale of Hypnotic Susceptibility, Form A. Palo Alto, CA: Consulting Psychologists Press.
Wadden, T. A., & Anderton, C. H. (1982). The clinical use of hypnosis. Psychological Bulletin, 91, 215-243.
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Whitehouse, W. G., Dinges, D. F., Orne, E. C., & Orne, M. T. (1988). Hypnotic hypermnesia: Enhanced memory accessibility or report bias? Journal of Abnormal Psychology, 97, 289-295.
Whitehouse, W.G., Orne,E. C., Orne, M. T., &Dinges, D.F. (1991). Distinguishing the source of memories reported during prior waking and hypnotic recall attempts. Applied Cognitive Psychology, 5, 51-59.
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Zusammenfassung: Retrospektive Analysen der Daten unseres Untersuchungsprogrammes uber Hypnose und Gedachtnis werden prasentiert, dies erfolgt mit besonderer Betonung der Effekte, die sich bei Probanden mit geringer Hypnotisierbarkeit zeigten. Im 1. Experiment fuhrten die Probanden sieben forcierte Erinnerungs Durchgange durch, in denen sie sich an eine Serie von Bildern, die eine Woche zuvor prasentiert wurden, erinnern sallten. Fur die Halfte der Probanden wurden die mittleren funf Durchgange unter der Verwendung von Hypnosetechniken durchgefuhrt; die ubrigen Probanden fuhrten alle Erinnerungsaufgaben in einem motivierten Wachzustand aus. Hypnose konnte weder bei hoch noch bei gering Suggestiblen zu einer Verbesserung der korrekten Erinnerungsleistung beitragen, die uber die gesteigerten Gedachtnis- und Erinnerungseffekte von wiederholten Versuchen der Wiedergewinnung von Gedachtnisinhalten uber die Zeit hinausgeht. Jedoch wahrend die hochsuggestiblen Probanden unabhangig von der Anwendung von Hypnose eine erhebliche Anzahl von bewuBten Erinnerungsfehlern machten (Storungen), zeigten Geringsuggestible, die hypnotisiert wurden, signifikant mehr Fehler als ihre Gegenuber in der Wachbedin-
368 EMILY CAROTA ORNE ET AL.
gung. 1m 2. Experiment wurden die Probanden gebeten festzustellen, ob bestimmte Erinnerungen, die wahrend zweier forcierter Befragungstests, die eine Woche zuvor durchgefuhrt wurden, aus dem ersten oder aus dem zweiten Test stammten. Es zeigte sich eine generelle Tendenz die berichteten Erinnerungen falschlicherweise auf die erste der beiden Befragungen zu attribuieren. Jedoch war der Effekt bei Geringsuggestiblen, die den zweiten Erinnerungsdurchgang unter Hypnose durchfuhrten, am groBten. Die Ergebnisse lassen darauf schlieBen, daB hochsuggestible Probanden nicht einzigartig sind in ihrer Anfalligkeit fur Gedachtnisverzerrungen, die durch Hypnose ausgelost werden. Probanden mit geringerer Suggestibilitat zeigen ebenfalls deutliche Veranderungen der Gedachtnisleistungen, wenn sie solchen Verfahren ausgesetzt werden.
Resume: Des analyses retrospectives des donnees de notre programme de
recherche sur l'hypnose et la memoire sont presentees avec une emphase specifique
sur les effets observes parmi les individus ayant une susceptibilite a l'hypnose
faible. Dans l'Experience 1, les participants ont complete sept essais de rappel
force dans une tentative de rememoration d'une serie d'images qui avait ete
presentee 1 semaine auparavant. Pour la moitie des participants, les cinq essais
du milieu de la serie (2 a 6) se sont effectuees a l'aide de techniques d'hypnose;
les autres participants ont fait toutes les tentatives de rappel dans une condition
d'eveil motive. L'hypnose n'a pu ameliorer le rappel adequat au-dela de l'hypermnesie
et des effets de reminescence associes aux essais repetes de recuperation dans
le temps autant pour les participants ayant une susceptibilite a l'hypnose elevee
que faible. Toutefois, alors que les participants ayant une susceptibilite a
l'hypnose elevee ont produit un nombre appreciable d'erreurs de rappel avec
confiance (i.e., intrusion) independant de l'utilisation de l'hypnose, les participants
ayant une susceptibilite a l'hypnose faible exposes aux techniques d'hypnose,
eux, ont rapporte significativement plus d'intrusion que leurs homologues dans
les conditions d'eveil. Dans l'Experience 2, les participants devaient identifier,
si les rappels specifiques rapportes durant deux des tests de rappel, de type
interrogatoire force effectues 1 semaine auparavant, provenaient du premier
ou du second de ces tests. Un biais general a attribuer faussement des rappels
precedemment rapportes au premier des deux moments de rappel a ete observe.
Toutefois, l'effet etait plus grand parmi les participants ayant une susceptibilite
a l'hypnose faible qui avaient participe a la seconde tentative de rappel sous
hypnose. Ces resultats impliquent que les individus hautement susceptibles a
l'hypnose ne sont pas les seuls a etre vulnerables aux distorsions mnesiques
induites par les techniques d'hypnose. Les individus faiblement susceptibles
a l'hypnose manifestent aussi des alterations de la memoire lorsqu'ils sont
exposes a de telles techniques.
369 LOW HYPNOTIZABILITY AND MEMORY LIABILITIES
Resumen: Se presentaron analisis retrospectivos de datos provenientes
de nuestro programa de investigacion sobre hipnosis y memoria. En el Experimenta
1, los participantes completaron siete ensayos de recuerdos forzados en un intento
de recordar series de cuadros que les fueron mostrados una semana antes. Para
la mitad de los participantes, los cinco ensayos del medio fueron hechos utilizando
procedimientos hipnoticos; el resto de los participantes, llevo a cabo los intentos
en una condicion de motivacion conciente. La hipnosis no mejoro el recuerdo
de los participantes de alta o de baja susceptibilidad, mas alla de los efectos
de hiperamnesia y reminiscencia asociadas con repetidos intentos de recuperacion
a traves del tiempo. Sin embargo, mientras que los participantes altamente sugestionables
produjeron un numero sustancial de errores de recuerdo confiables (es decir,
intrusiones) independientemente del uso de hipnosis, los participantes de baja
susceptibilidad expuestos a procedimientos hipnoticos reportaron significativamente
mas intrusiones que sus pares del grupo de condicion conciente. En el Experimento
2, se les pidio a los participantes identificar si recolecciones especificas,
reportadas durante dos tests de interrogatorio forzado de recuerdos, efectuadas
una semana antes, se habia originado en el primero o segundo de estos tests.
Se observo un sesgo generalizado de mal atribuir a recolecciones reportadas
previamente a la primera de las dos ocasiones de recuerdo, sin embargo, el efecto
fue mayor entre los sujetos de baja sugestibilidad que atravesaron el segundo
intento de recuerdo bajo hipnosis. Estos hallazgos implican que los individuos
altamente sugestionables no son los unicos en ser vulnerables a las distorsiones
de la memoria, inducidas por las tecnicas hipnoticas. lndividuos de menor capacidad
hipnotica tambien manifestaron alteraciones de la memoria cuando fueron expuestos
a estos procedimientos.
The preceding paper is a reproduction of the following
article (Orne, E. C., Whitehouse, W. G., Dinges, D. F., & Orne, M. T. Memory
liabilities associated with hypnosis: Does low hypnotizability confer immunity?
International Journal of Clinical and Experimental Hypnosis, 1996, 44, 354-369.).
It is reproduced here with the kind permission of the Editor-in-Chief of The
International Journal of Clinical and Experimental Hypnosis.