Eyewitness Memory Enhancement in the Police Interview: Cognitive Retrieval Mnemonics Versus Hypnosis

This research compared the effectiveness of three interview procedures for optimizing eyewitness memory performance: (a) the "cognitive interview" based on memory-retrieval mnemonics from current memory theory, (b) the presently controversial hypnosis interview, and (c) the standard (control) police interview. These methods were evaluated empirically in a controlled, yet ecologically valid, laboratory setting. Eighty-nine subjects viewed police training films of simulated violent crimes and were questioned individually in interactive interviews 48 hours later by experienced law-enforcement personnel. Both the cognitive and hypnosis procedures elicited a significantly greater number of correct items of information from the subjects than did the standard interview. This result, which held even for the most critical facts from the films, was most pronounced for crime scenarios in which the density of events was high. The number of incorrect items of information generated did not differ across the three interview conditions. The observed memory enhancement was interpreted in terms of the memory-guidance techniques common to both the cognitive and hypnosis interviews. Neither differential questioning time nor heightened subject or interviewer motivation could explain the results.