Source monitoring deficits in patients with schizophrenia; a multinomial modelling analysis

Background. Schizophrenia patients, particularly those with symptoms such a s thought insertion, passivity experiences and hallucinations, may share an underlying cognitive deficit in monitoring the generation of their own tho ughts. This deficit, which has been referred to as 'autonoetic agnosia', ma y result in the conclusion that self-generated thoughts come from an extern al source. Previous work supports this notion, yet the statistical approach es that have been used have not enabled a distinction between specific defi cits suggesting autonoetic agnosia and more general cognitive dysfunction. Methods. Autonoetic agnosia was assessed using source-monitoring paradigms in 28 patients with schizophrenia and 19 control subjects. Multinomial mode l analyses, which allow the distinction between deficits in recognizing inf ormation, remembering its source, and response biases, were applied to the data. Results. Schizophrenia patients were impaired in discriminating between wor ds that came from two external sources, from two internal sources, and one internal and one external source. In a condition requiring subjects to dist inguish between words they had heard from those they had imagined hearing, when schizophrenic patients did not remember the source of the information, they showed a stronger bias than controls to report that it had come from an external source. Conclusions. The application of multinomial models to source monitoring dat a suggests that schizophrenia patients have source monitoring deficits that are not limited to the distinction between internally-generated and extern ally-perceived information. However, when schizophrenia patients do not rem ember the source of information, they may be more likely than controls to r eport that it came from an external source.