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Eyewitness memory: A comparison of guided memory and hypnotic hypermnesia techniques using a stress provoking film

1 April 1984


The area of eyewitness memory continues to .interest researchers and clinicians alike. Especially in applied forensic settings, accurate and complete recall is critical. Hypnotic retrieval techniques have been observed in case reports to be effective in enhancing recall. However, the use of such techniques in forensic investigations is controversial because of the possibility of an increased chance of memory alteration. In addition, recent experiments have not confirmed that hypnotic retrieval methods do in fact enhance memory. Subjects (N = 66 ) were initially shown a 13-minute black and white sound film of three industrial accidents, in groups of three to eight. The film, It Didn't Have To Happen, was demonstrated in earlier studies to induce high levels of both physiological and subjective stress in the viewer. Subjects returned three days later to participate in one of six experimental conditions, according to whether the subject was of high or medium hypnotic susceptibility. of three recall conditions: 1. Subjects were randomly assigned to one general recall, 2. guided memory, or 3. hypnotic hypermnesia, and given seven minutes in which to recall any details of a two-minute segment of the film. Subjects were then asked eighteen nonleading, leading and misleading questions. Dependent measures on free recall were total detail, total correct details, total error, proportion of error, total inferences, total correct inferences and proportion of incorrect inferences. Number correct, number of errors, and mean confidence ratings were scored on nine nonleading, three leading and six misleading questions. Results for free recall data indicated a tendency for subjects in the control and guided memory groups to remember more total number of details, though no differences were found for correct details or for incorrect details among the groups or between levels of hypnotic susceptibility. No differences among groups or between levels of susceptibility were found for proportion: of error. The average percent of error was 17% in free recall. Highly susceptible subjects made significantly more incorrect inferences while medium susceptible subjects made significantly more correct inferences, in all three treatment conditions. On the objective questions no significant main effects or interactions were found for either nonleading, leading, or misleading questions. On nonleading questions a tendency was found for subjects in the control group to make more correct responses than subjects in the guided .memory or hypnosis groups. Finally, medium susceptible subjects were more confident of their answers to both leading and misleading questions, than highly susceptible subjects. In this study neither the guided memory nor the hypnotic hypermnesia instructions proved to be better than the control instructions. Also, the use of hypnosis did not prove to be as generally detrimental as has been reported in the literature. However, hypnosis did not enhance memory in this study. Results are discussed in terms of specific areas of eyewitness memory and the differences between memory enhancement techniques in applied forensic settings.


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