Inductive reasoning in delusional thought

Schizophrenic subjects who experience delusions have been found to request less information and are more certain about the correctness of their decision than control subjects when performing abstract probability judgment tasks (Huq, Garety & Hemsley, 1988). The present study employed an inductive reasoning task using familiar contextual stimuli to investigate the strategies employed and to observe the stages in reasoning. Twelve subjects with a diagnosis of schizophrenia and experiencing delusions were compared with matched depressed patients and normal controls on a version of the “Twenty Questions Game”. It was found, consistent with the earlier study, that the deluded subjects requested less information before making a decision, and produced poorer judgments. It is concluded that there exists a core deficit, independent of task or context.