The perceptual-cognitive dysfunction theory of schizophrenia reevaluated

The purpose of this study was to investigate the often noted perceptual-cognitive deficit associated with schizophrenia. A few recent investigations, which were carefully controlled with respect to their design, have seriously challenged the long established contention that schizophrenic patients exhibit a deficit at this level of behavioral analysis. In addition to these reports several recent reviews of the literature in this area have seriously questioned the validity of the design of the majority of this research. The experimental designs typically suffer from at least one of three short comings: (1) selection of the schizophrenic sample tested, (2) the failure to properly match the reference group or groups against which the performance of the schizophrenic subjects is compared, and (3) the failure to demonstrate that those differences observed were the results of the hypothesized deficit and not due to some uncontrolled ancillary variable. The present study postulated that through the use of properly selected and controlled reference groups no deficit would be observed in the performance of the chronic schizophrenic sample tested on a wide variety of tasks designed to measure basic perceptual and cognitive processes. The term basic perceptual process is used here to denote the input stage of stimulus information. That is, the accurate reception of stimulus input from the environment. Basic cognitive processes refers to the interpretation and utilization of the perceptual input that permits the individual to perform relatively complex behaviors, follow instructions and organize his responses in an appropriate fashion to deal effectively with the existing stimulus conditions. Twelve quartets each consisting of a chronic schizophrenic patient, an alcoholic patient, and two non-psychiatric patients, one of whom was receiving drug medication similar to the psychiatric groups were constituted from a hospital population. The members of each quartet were matched on the variables of age, sex, race, IQ, education, and length of hospitalization. Each subject was tested individually on a battery of tests designed to measure not only performance on perceptual and cognitive tasks but also on ancillary variables of motivation, alertness, short-term memory, and ability to understand and follow instructions. As predicted, the schizophrenic patients were not found to evidence any form of deficit on this test battery unique to schizophrenia. These results indicate that future research must be aimed at the Investigation of more complex forms of behavior while exerting care to select and properly control the reference group(s) with which the performance of the schizophrenic patients are compared.