The impact of posthypnotic amnesia and directed forgetting on implicit and explicit memory: new insights from a modified process dissociation procedure.

The authors describe a study investigating the relationship between posthypnotic amnesia (PHA) and directed forgetting (DF) and their impact on implicit and explicit memory. This study adopted a recent modification of the process dissociation procedure to accommodate the cross-contamination of memory test performance by implicit and explicit memorial factors. Forty high and 40 low hypnotically susceptible participants were compared in PHA, DF, and control conditions on estimates of voluntary conscious (VCM), involuntary conscious (ICM), and involuntary unconscious memory (IUM) performance. Both groups showed significant decrements in VCM and ICM following instructions for DF, whereas only high susceptibles showed this decrement in the PHA condition; neither DF nor PHA affected IUM. Moreover, there was no relationship between forgetting in PHA and DF. Although both PHA and DF seem to prevent the conscious (i.e., explicit) expression of memorial information while leaving implicit memory intact, the mechanisms underlying these phenomena may nevertheless be different.