APA Dictionary of Psychology

pervasive, marked impairment of thinking in terms of loosening of associations and slowness of associations, representing positive symptoms and negative symptoms, respectively, of schizophrenia. Because thinking must be inferred rather than observed, and because no single definition or test or technique of inference has been universally accepted, evaluation is usually limited to examining samples of speech or writing that the individual is inclined to express. On certain psychological tests (e.g., Rorschach, MMPI), schizophrenic thinking is identified deviant verbalizations, which are unusual, exaggerated, or otherwise abnormal responses to items presented during the test, such as inventing a word (see neologism) to describe a Rorschach inkblot. On the Whitaker Index of Schizophrenic Thinking (WIST; 1980), schizophrenic impairment of thinking is defined as simultaneously illogical, impaired, and without apparent awareness, all to a marked degree.