Hallucinations and two types of free-recall intrusion in schizophrenia.

Background: Previous research has demonstrated that various types of verbal source memory error are associated with positive symptoms in patients with schizophrenia. Notably, intrusions in free recall have been associated with hallucinations and delusions. We tested the hypothesis that extra-list intrusions, assumed to arise from poor monitoring of internally generated words, are associated with verbal hallucinations and that intra-list intrusions are associated with global hallucination scores.
Method: A sample of 41 patients with schizophrenia was administered four lists of words, followed by free recall. The number of correctly recalled words and the number of extra- and intra-list intrusions were tallied.
Results: The verbal hallucination score was significantly correlated with the number of extra-list intrusions, whereas it was unrelated to the number of correctly recalled words. The number of intra-list intrusions was significantly correlated with the global, but not with the verbal, hallucination score in the subsample of hallucinating patients. It was marginally significantly correlated with the delusion score in delusional patients.
Conclusions: The data corroborate the view that verbal hallucinations are linked to defective monitoring of internal speech, and that errors in context processing are involved in hallucinations and delusions.