Incautious reasoning as a pathogenetic factor for the development of psychotic symptoms in schizophrenia.

Previous studies indicate that schizophrenia patients draw decisions more hastily than controls. The aim of the present study was to obtain convergent evidence with a new paradigm, designed after the Who Wants to Be a Millionaire television game show. Thirty-two schizophrenia patients and 38 healthy subjects were administered 20 knowledge questions, along with 4 response alternatives. Participants were required to provide probability estimates for each alternative. Whenever a subject was confident that one of the alternatives was correct or was wrong, the subject was asked to indicate this via a decision or rejection rating. Thus, probability estimates and decisions were independently assessed, allowing determination of the point at which probability estimates translate into decisions. Patients and controls gave comparable probability estimates for all alternatives. However, patients committed more erroneous responses, owing to their making decisions in the face of low subjective probability ratings and rejecting alternatives despite rather high probability ratings. The results provide further evidence for the claim that schizophrenia patients make strong judgments based on little information. We propose that a lowered threshold for accepting alternatives provides a parsimonious explanation for the data-gathering bias reported in the literature.