Intact implicit learning in schizophrenia

Objective: Schizophrenia impairs performance on explicit, but not implicit, memory tasks, indicating that conscious awareness at retrieval is a critic al determinant of impaired memory. The authors investigated implicit learni ng, i.e., knowledge acquisition in the absence of conscious awareness, in p atients with schizophrenia. Method: An artificial grammar learning task was used to assess implicit lea rning in 48 patients with schizophrenia and 24 healthy comparison subjects. The subjects were first presented with letter strings that were generated according to the rules of a finite-state grammar paradigm. They were then r equired to indicate whether new letter strings were "grammatical," dependin g on whether or not the strings corresponded to the rules. 1Q, working memo ry, explicit memory, verbal fluency, and speed of processing were also asse ssed. Results: Patients performed significantly worse than the comparison subject s on cognitive tasks that assessed episodic memory, verbal fluency, working memory, and speed of processing. In contrast, patients classified as being correct more grammatical than nongrammatical letter strings, and the magni tude of the difference was similar to that observed in healthy comparison s ubjects. Conclusions: implicit learning, as assessed with an artificial grammar lear ning task, is intact in patients with schizophrenia. Conscious awareness mi ght be a critical determinant of memory impairment both at encoding and at retrieval.