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

BACKGROUND

Schizophrenia patients, particularly those with symptoms such as thought insertion, passivity experiences and hallucinations, may share an underlying cognitive deficit in monitoring the generation of their own thoughts. This deficit, which has been referred to as 'autonoetic agnosia', may result in the conclusion that self-generated thoughts come from an external source. Previous work supports this notion, yet the statistical approaches that have been used have not enabled a distinction between specific deficits 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 model analyses, which allow the distinction between deficits in recognizing information, remembering its source, and response biases, were applied to the data.

RESULTS

Schizophrenia patients were impaired in discriminating between words that came from two external sources, from two internal sources, and one internal and one external source. In a condition requiring subjects to distinguish 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 data suggests that schizophrenia patients have source monitoring deficits that are not limited to the distinction between internally-generated and externally-perceived information. However, when schizophrenia patients do not remember the source of information, they may be more likely than controls to report that it came from an external source.