ABSTRACT
BACKGROUND: The attribution of self-generated speech to others could explain the experience of verbal hallucinations. To test this hypothesis, we developed a task to simultaneously evaluate (A) operations of self-other distinction and (B) operations that have the same cognitive demands as in A apart from self-other distinction. By adjusting A to B, operations of self-other distinction were specifically evaluated. METHOD: Thirty-nine schizophrenia patients and 26 matched healthy controls were required to distinguish between self-generated, other-generated and non-generated (self or other) sentences. The sentences were in the first, second or third person and were read in a male or female voice in equal proportions. Mixed multi-level logistic regression models were used to investigate the effect of group, sentence source, pronoun and gender of the heard sentences on response accuracy. RESULTS: Patients differed from controls in the recognition of self-generated and other-generated sentences but not in general recognition ability. Pronoun was a significant predictor of response accuracy but without any significant interaction with group. Differences in the gender of heard sentences were not significant. Misattribution bias differentiated groups only in the self-other direction. CONCLUSIONS: These data support the theory that misattribution of self-generated speech to others could result in verbal hallucinations. The syntactic (pronoun) factor could impact self-other distinction in subtypes of verbal hallucinations that are phenomenologically defined whereas the acoustic factor (gender of heard speech) is unlikely to affect self-other distinction.
