Schizotypy and conditional reasoning.

This study investigated the role of reasoning biases in delusion formation and maintenance. Reasoning judgments have been shown to be influenced by prior knowledge, beliefs, and experience--that is, information stored in semantic memory. It was hypothesized that high schizotypes would exhibit a "jump to conclusions" style of reasoning as a result of not using implicit information concerned with cause-effect relationships. Research into human reasoning has traditionally adopted logic as a normative framework to assess human reasoning. Conditional inference tasks are direct tests of logical performance, and we employed an established design that depends upon the reasoner's ability to access and use implicit information. In an effort to negate some of the difficulties of research with schizophrenia patients, schizotypy measures were employed in a normal population. The results confirmed that high scorers on one dimension of schizotypy (Impulsive Nonconformity) failed to take account of the number of counterexamples that characterized the cause-effect conditional statement. These observations supported previous research demonstrating a jump to conclusions style of reasoning that it has been suggested plays a role in the formation and maintenance of delusions. Furthermore, these findings suggest a possible link between semantic memory and reasoning biases.