DISTURBED thinking is generally considered the distinctive and most prominent feature of schizophrenic disorder. Bleuler (1911), though he included ambivalence, autism, and affective disorder among the fundamental symptoms of schizophrenia, designated thought disorder, defined as a disruption in the continuity of associations, as the primary identifying characteristic of schizophrenia. Meehl (1962) similarly points out that although ambivalence, anhedonia, and interpersonal aversiveness are important aspects of schizophrenia, cognitive slippage is usually the most heavily weighted factor in clinical judgments. This and the following two chapters are concerned with the nature of disturbed thinking and encompass the bulk of psychodiagnostic indicators most distinctively associated with schizophrenic disturbance.