Academic journal article International Journal of Psychology and Psychological Therapy

A Comparison of Posthypnotic Amnesia and the Simulation of Amnesia through Brain Injury

Academic journal article International Journal of Psychology and Psychological Therapy

A Comparison of Posthypnotic Amnesia and the Simulation of Amnesia through Brain Injury

Article excerpt

Since the early days of hypnosis claims have been made that, in a variety of situations, people who have been hypnotised and given suggestions for amnesia can be made amnesic for what they have done or what has happened to them. For example, it has been alleged that a hypnotised person given a suggestion for amnesia may commit a crime, including murder, and afterwards remain unaware that he or she has done so, or may be a victim of rape without his or her knowledge (Laurence and Perry, 1988; Gibson, 1992; Mottahedin, 1992). However, insight into these cases is made difficult by the fact that, within the academic literature, the issue of whether people can be made amnesic against their will remains unresolved.

In a typical laboratory demonstration of suggested posthypnotic amnesia, before or during hypnosis, participants are given a series of suggestions to perform, or a list of items to remember. During hypnosis they are then given a suggestion that, when they 'wake-up', they will find it difficult to remember what has happened or what they learned, until they hear reversal cue from the hypnotist such as, 'now you can remember everything'. In general, experimental results show that many subjects will show an initial decrement in recall and recognition which is subsequently dissipated by the reversal cue; moreover, this 'amnesia reversal' is not simply a consequence of repeated retrieval attempts (see for example, Bowers, 1983; Coe, 1989; Cooper, 1972; Kihlstrom and Evans, 1976; McConkey and Sheehan, 1981; McConkey, Sheehan and Cross, 1980; Nace, Orne and Hammer, 1974; Williamson, Johnson and Ericksen, 1965).

According to the dissociationist interpretation of hypnosis, suggested hypnotic amnesia occurs because the forgotten material is dissociated from awareness, and cannot be accessed until the hypnotist issues the signal (reversal cue) for normal control to be resumed. Moreover, because executive control over memory is largely or entirely bypassed in susceptible individuals under hypnosis, this temporary dissociation is allegedly so profound that, until a reversal cue is given by the hypnotist, hypnotised participants cannot access the forgotten material no matter how hard they try (Bowers, 1983; Bowers and Woody, 1996; Evans, 1991; Hilgard, 1986; Kihlstrom, 1978, 1983; Kihlstrom, Evans, Orne and Orne, 1980; Sheehan and McConkey, 1982). In contrast, other theorists have argued that hypnotic amnesia is primarily a consequence of volitional strategies in response to task demands such as distraction, divided attention, and voluntarily withholding responses to give the appearance of amnesia until the experimental demands (the reversal cue) indicate otherwise (Coe, 1978, 1989; Spanos, 1986, 1991; Wagstaff, 1977, 1981, 1986, 1991).

As evidence in support of the latter interpretation, it has been noted that whilst hypnotically amnesic participants will readily show temporary deficits in recall and recognition, performance on measures of memory such as savings in relearning and proactive and retroactive inhibition remains relatively unimpaired (Barber, 1969; Gregg, 1979; Kihlstrom, 1985, 1998; Wagstaff, 1981). According to a response suppression interpretation, these findings occur because suggestions for hypnotic amnesia only work on those aspects of memory that are amenable to deliberate conscious suppression or are obvious to the subject in terms of task demands (Wagstaff, 1981). For instance, if one were attempting to respond to task demands, it would be relatively easy to voluntarily inhibit responses on a simple recall or recognition task, but one would only be likely to inhibit savings on relearning if one were aware of the effect, and it would be extremely difficult to inhibit proactive and retroactive interference effects even if one were aware of them.

However, dissociationists such as Kihlstrom (1998) have argued that these results do not indicate that amnesic participants are employing any kind of conscious suppression; they simply attest to a dissociation between two kinds of memory in hypnosis. …

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