Two types of posthypnotic amnesia: Recall amnesia and source amnesia

Abstract

Posthypnotic recall amnesia traditionally refers to Ss inability to recall, when challenged posthypnotically, the events which occurred during hypnosis. Posthypnotic source amnesia, only indirectly alluded to in the literature, occurs when S subsequently remembers the experiences of hypnosis, but has no recollection of acquiring the experiences: S knows the information presented during hypnosis, but does not know how or why he knows. Data from 3 samples are presented to support the distinction between the 2 types of posthypnotic amnesia. Of 243 Ss, 18 experienced recall amnesia, 26 displayed source amnesia, but only 4 developed both kinds of amnesia. There were no differences in rated depth of hypnosis of these 3 subgroups. Correlations between both types of amnesia with both rated depth of hypnosis and objective measures of susceptibility to hypnosis were significant but low. Recall amnesia and source amnesia correlated .37, .38, and .39, respectively (p < .001) in the 3 samples. The evidence indicates the two types of amnesia are different phenomena. Similarities between source amnesia and certain (dissociative) normal and psycho-pathological memory processes are discussed.