Enhancing visual memory: Trying hypnosis, trying imagination, and trying again

Can unconscious intentions be more effective than conscious intentions? Test of the role of metacognition in hypnotic response

While several theories assume that responses to hypnotic suggestions can be implemented without executive intentions, the metacognitive class of theories postulate that the behaviors produced by hypnotic suggestions are intended and the accompanying feeling of involuntariness is only a consequence of strategically not being aware of the intention. Cold control theory asserts that the only difference between a hypnotic and non-hypnotic response is this metacognitive one, that is, whether or not one is aware of one's intention to perform the relevant act. To test the theory, we compared the performance of highly suggestible participants in reducing the Stroop interference effect in a post-hypnotic suggestion condition (word blindness: that words will appear as a meaningless foreign script) and in a volitional condition (asking the participants to imagine the words as a meaningless foreign script). We found that participants had equivalent expectations that the posthypnotic suggestion and the volitional request would help control the conflicting information. Further, participants felt they had more control over experiencing the words as meaningless with the request rather than the suggestion; and they experienced the request largely as imagination and the suggestion largely as perception. That is, we set up the interventions we required for the experiment to constitute a test of cold control theory. Both the suggestion and the request reduced Stroop interference. Crucially, there was Bayesian evidence that the reduction in Stroop interference was the same between the suggestion and the volitional request. That is, the results support the claim that responding hypnotically does not grant a person greater first order abilities than they have non-hypnotically, consistent with cold control theory.

Experimental production of past-life memories in hypnosis

To explore the nature of past-life memories in hypnosis, 64 normal male adults aged 21 to 23 were selected using the Korean version of the Harvard Group Scale of Hypnotic Susceptibility (HGSHS:K) and a simple belief in past-life scale. They all received hypnotic past-life regression 3 times. The influence of HGSHS:K scores on the production rate of past-life memories was statistically significant; however, the influence of belief was not. The percentage of subjects who responded to hypnotic past-life regression increased with hypnotizability. Content analysis showed that cultural background and religious concepts influenced past-life memory production. Animals as past-life identities, for example, were reported whereas all past-life identities were human in a Canadian study.

Recognition hypermnesia: how to get it

Although recall hypermnesia (enhanced recall) over time with repeated testing has by now become an established empirical fact, its recognition counterpart, recognition hypermnesia, has defied clear-cut laboratory confirmation. In four studies, which relied on the retrieval component of recognition memory, it was shown that recognition memory, indexed by d', reliably improved over three successive recognition tests. The stimuli consisted of 140 cartoons, each comprising a picture and a verbal caption. Recognition memory was tested on transforms or part-forms (parts) of the original stimulus material (pictures only, verbal paraphrases of the pictures, the latent content of the cartoons, or the combination of paraphrases and latent contents). The strongest effects were obtained when the originally presented cartoons were tested on their latent (deep semantic) contents. Recognition hypermnesia for part-forms or transforms of earlier presented stimuli has potentially wide-ranging implications since real-world recognition--of faces, texts, visual scenes--usually involves recognising stimuli that are variants, not exact copies, of the originally encountered materials.

Indexing the experience of sex change in hypnosis and imagination

The authors suggested a change of sex to high hypnotizable participants in hypnosis and imagination conditions and indexed the subjects' experiences with a continuous, concurrent behavioral measure that involved them turning a dial to indicate changes in the strength of the suggested effect. In addition, the researchers indexed the participants' experiences through retrospective ratings of realness, involuntariness, and active thinking. The dial rating showed that the onset of the experience was more rapid for hypnotic than for imagination participants. Moreover, there were differences in the relationship between dial ratings and retrospective ratings across the conditions as well as across the suggestion, test, and cancellation phases of the item. The findings are discussed in terms of how the dial method provides a better understanding of suggested sex change as well as a better understanding of the private experience of hypnosis and imagination.

Eliciting autobiographical pseudomemories: the relevance of hypnosis, hypnotizability, and attributions

The authors investigated the roles of hypnosis, hypnotizability, and attributions in autobiographical pseudomemories. Experiment 1 administered a suggestion for recall of their second birthday to hypnotized high and low hypnotizable participants and nonhypnotized, high hypnotizable participants; Experiment 2 administered a similar suggestion to real and simulating participants. Recall was tested during hypnosis, after hypnosis, and after a challenge procedure. In Experiment 1, more highs than lows reported a memory during hypnosis; however, following the challenge, half the walking highs but none of the hypnosis highs retracted their memory. Notably, highs attributed their memories to reconstructions based on other birthdays. In Experiment 2, whereas an equal number of reals and simulators reported a memory of their second birthday during hypnosis and then retracted following the challenge, they made different attributions about their memories. These findings highlight the value of a closer investigation of attributional processes that reconcile believed-in autobiographical memories with conflicting evidence.

Admissibility and per se exclusion of hypnotically elicited recall in American courts of law

State v. Mack (1980) ruled that hypnotically elicited testimony is per se excluded from Minnesota law courts; this court also ruled that police could employ hypnosis in an attempt to construct an independently corroborated case. In recent years, there have been moves to rescind this exclusion; this raises a question of the probative value of such additional information when it is uncorroborated. This situation is compared with that of the polygraph as an index of deception: Like hypnosis, it is excluded per se in most American jurisdictions. Some legal decisions in Wisconsin are used to illustrate one alternative to the per se exclusion approach. Admissibility of scientific evidence in American courts of law has been based on a criterion of "general acceptability within the relevant scientific community," as first elucidated in Frye v. United States (1923). Recently, the U.S. Supreme Court overturned the Frye decision in Daubert v. Merrell Dow Pharmaceuticals, Inc. (1993), by making general acceptability but one of several admissibility criteria. Three Daubert-based decisions, one involving hypnosis and all concerned with "recovered repressed memories," indicate some problems in law posed by Daubert.

The illusion of familiarity: an alternative to the report-criterion account of hypnotic recall

Hypnosis increases the likelihood that participants will report incorrect material at higher levels of confidence. One interpretation of such data is that hypnosis induces individuals to lower the criterion they use to make memory reports. A lowered report criterion could account for the increase in items that participants are willing to report as memories but not for the increase in confidence that typically accompanies hypnotic retrieval. Although some participants may indeed lower their report criterion, this alone should not result in the highly confident confabulation so often observed. An alternative perspective is that for some participants, hypnosis alters the experience of retrieval such that items generated during retrieval attempts are more likely to have the qualities (e.g., perceptual fluency, vividness) usually associated with remembering. This illusion of familiarity would account for the higher levels of confidence that are so frequently observed in hypnotic recall, and adopting this perspective should lead to even greater caution in the use of hypnosis as an aid to retrieval.

Hypnotic hypermnesia: the empty set of hypermnesia

Although a long tradition exists suggesting that hypnosis can enhance memory (hypnotic hypermnesia), the experimental literature is quite mixed. When, however, laboratory studies are classified according to the type of stimulus and memory tests employed, a remarkable orderliness of outcomes emerges: Recall tests for high-sense stimuli (e.g., poetry, meaningful pictures) almost always produce hypermnesia, but not recognition tests for low-sense stimuli (e.g., nonsense syllables, word lists). An important methodological issue is whether the recall increments for high-sense stimuli constitute enhanced memory or enhanced reporting (laxer response criteria). Recent laboratory literatures show that, beyond response criterion effects, true memory enhancement (hypermnesia) exists. Experiments conducted over the past decade, however, demonstrate that it is repeated retrieval effort and not hypnosis that is responsible for hypermnesia: Repeated testing without hypnosis yields as much hypermnesia as with hypnosis.

The effects of cue level, hypnotizability, and state instruction on responses to leading questions

Two sessions were conducted in which independent groups of 86 high- and 85 low-susceptible subjects, responding individually under waking or hypnotic instruction, answered high- and low-cued leading questions about a video event that depicted shooting at an airport. The two sessions were separated by 1 week, and the same questions were asked in both sessions. It was predicted that highly susceptible subjects responding under hypnotic instruction would show the most evidence of accepting false information via strongly cued leading questions. Results showed general effects for leading questions and level of susceptibility but no firm support for the involvement of hypnosis. Data are discussed in terms of both the linguistic and social factors that appear to have operated on subjects in the study, results overall highlight the strong influence of level of susceptibility on subjects' acceptance of false information.

The role of expectancy in hypnotic hypermnesia: a brief communication

Previous research has yielded equivocal evidence of hypnotic memory enhancement. The present experiment assessed the effects of expectancy and hypnotizability on recall for videotaped material under waking and hypnotic conditions. Ss (N = 138) were informed of hypnotic induction either before (expectancy condition) or after (no expectancy condition) watching a videotaped enactment of a crime and completing an initial waking recall test (RI). Both groups then underwent hypnotic induction, and completed the test again (R2). Ss' raw recall scores were significantly greater under hypnotic than waking conditions, but this hypermnesia was not evident when scores were corrected for mere increase in rate of responding. Ss expecting later hypnosis scored significantly higher than Ss with no such expectations, but again, this difference was not evident in corrected scores. Hypnotizability of Ss was, however, related to corrected recall, with high hypnotizable Ss displaying the greatest increase in rate of responding from R1 to R2. No evidence for the hypothesized "suppression effect" underlying hypnotic hypermnesia was found.

Effects of hypnosis and level of processing on repeated recall of line drawings

Moderately susceptible subjects (N = 30) initially judged 30 line drawings of objects for pleasantness (deep processing) and 30 line drawings for visual complexity (shallow processing), after which they were given two immediate recall tests. Following a 48-hr delay, subjects were allocated randomly to hypnosis, simulation, or neutral control conditions and were tested four more times. Subjects produced more correct and incorrect responses over the six trials and gave a higher number of correct responses for deep items than for shallow items. Over the last four trials, hypnosis had no general facilitative effect relative to the other two treatments, but the effect of depth was strongest for hypnotized subjects, who recalled more deep items than did the controls. Finally, both hypnotized and simulating subjects rated their recall as more involuntary and their experimental treatment as more helpful than did the controls. Caution is urged in the forensic use of hypnosis as a retrieval device.