In a serial reaction time task, procedural memory was examined in Dissociative Identity Disorder (DID). Thirty-one DID patients were tested for inter-identity transfer of procedural learning and their memory performance was compared with 25 normal controls and 25 controls instructed to simulate DID. Results of patients seemed to indicate a pattern of inter-identity amnesia. Simulators, however, were able to mimic a pattern of inter-identity amnesia, rendering the results of patients impossible to interpret as either a pattern of amnesia or a pattern of simulation. It is argued that studies not including DID-simulators or simulation-free memory tasks, should not be taken as evidence for (or against) amnesia in DID.
Huntjens, R. J. C., Postma, A., Woertman, L., van der Hart, O., & Peters, M. L. (2005). Procedural memory in dissociative identity disorder: when can interidentity amnesia be truly established? Consciousness and Cognition, 14, 377-389. https://doi.org/10.1016/j.concog.2004.10.001