Reducing and reversing pseudomemories with hypnosis†

As a forensic memory enhancement tool, hypnosis is problematic because it tends to increase pseudomemory responses and inflate confidence regardless of accuracy. A variety of evidence suggests that major influences in producing these effects are expectancy and demand characteristics. However, if expectancy and demand characteristics play a role in increasing false positive responses with hypnosis, it may be possible to use the same factors to reduce false positive responses. Some have argued that the standard misinformation effect in nonhypnotic situations may be influenced by expectancy and demand characteristics. Consequently, if subjects are given misleading information followed by an instruction suggesting that hypnosis will reduce the influence of misinformation, hypnosis may reduce rather than increase false positive responses, including spurious confidence in errors. In this paper two studies are described that lend some experimental support for this hypothesis. The first showed that, when participants are not given an opportunity to commit themselves to making errors, the misinformation effect can be eliminated if hypnosis is given together with a suggestion that it will help participants discriminate between correct and incorrect information. The second study showed that a similar posthypnotic suggestion was more effective than a warning alone in reducing or reversing misinformation errors even after participants had committed themselves to reporting such errors. There was no evidence of inflated confidence with hypnosis in either study. Copyright © 2008 British Society of Experimental & Clinical Hypnosis. Published by John Wiley & Sons, Ltd.