Hypnotic Hypermnesia: Enhanced Memory Accessibility or Report Bias?

The processes responsible for the occasional positive findings have eluded identification. The present experiment assessed delayed recall for filmed material under conditions in which subjects were required to answer all questions even if they had to guess. Subjects also rated confidence in the accuracy of each response. After an initial wake-baseline forced-recall test, the subjects were randomly selected for hypnosis or waking conditions for a second forced-recall test. On the second test, both groups recalled additional correct details, but the magnitude of hypermnesia was not greater for subjects exposed to the hypnosis treatment. However, the hypnotized subjects exhibited a significantly greater increase in confidence for responses designated as "guesses" on the prior waking test. This finding was consistent with the view that hypnosis engenders a shift in the subjective criterion for what constitutes a "memory." The implications of these findings for using hypnosis in forensic situations are detailed. 3 tables, 36 references. (Author abstract modified)