Apparent amnesia on experimental memory tests in dissociative identity disorder: an exploratory study

Dissociative identity disorder (DID; called multiple personality disorder in DSMIII-R) is a psychiatric condition in which two or more identity states recurrently take control of the person's behavior. A characteristic feature of DID is the occurrence of apparently severe amnestic symptoms. This paper is concerned with experimental research of memory function in DID and focuses on between-identity transfer of newly learned neutral material. Previous studies on this subject are reviewed and a pilot study with four subjects is described. This study is specifically concerned with the question whether self-reported asymmetries in between-identity transfer can be replicated on experimental memory tests. A secondary aim was to examine whether, in the absence of explicit transfer, implicit transfer of information would occur. The results showed that the apparent amnestic asymmetry for explicit information was substantiated in the laboratory, although at least some leakage was present between the apparently amnestic identities. No evidence was found for better performance on implicit than on explicit memory tests in the apparently amnestic identities. In the discussion, parallels between apparent amnesia in DID and state-dependent memory are drawn, and the question of simulated amnesia is addressed.