Hypnotic Effects on Hypermnesia

Abstract

The effects of hypnotic suggestions for improved memory were explored using procedures known to produce hypermnesia in the normal waking state. In Experiment 1, 64 trait adjectives were randomly assigned to orthographic, phonemic, semantic, and self-referent orienting tasks in an incidental learning paradigm. These were presented to 40 Ss classified as low, medium, high, or very high in hypnotizability, followed by a series of 3 recall trials: immediately after the study phase, following a hypnotic suggestion for enhanced memory, and after termination of hypnosis. There were significant effects of both encoding condition and repeated trials on incidental recall. However, the hypermnesia effect observed in other experiments was not obtained, and there were no memory effects attributable to hypnosis. In Experiment 2, 60 line drawings of common objects were presented to an overlapping sample of 40 Ss, followed by the same recall procedure employed in Experiment 1. There was a significant hypermnesia effect of repeated trials, but again no effects attributable to hypnosis. In Experiment 1, the hypnotic procedure seemed to interfere with the normal waking hypermnesia effect; in Experiment 2, hypnosis failed to enhance it. These results fail to support the use of hypnosis to enhance the memories of eyewitnesses in forensic investigations.