In this article a number of psychological theories on the causes of schizophrenic symptoms are reviewed. The authors present theories that explain symptoms in terms of defects in the speed and capacity of cognitive information processing, or as defects in the profile of cognitive abilities. The neuropsychological research strategy is also discussed. In this context particular attention is paid to the theories of Weinberger and Frith.

The cognitive approach reveals, that in schizophrenic patients disturbances are mainly found in controlled information processing (as opposed to automatic processing).

Research on the abnormalities in the profile of cognitive abilities of schizophrenic patients appears to have hardly any theoretical foundation. Therefore this profile approach has little explanatory value.

Although neuropsychological research in schizophrenia has to deal with great methodological and conceptual problems, this approach is promising, in particular when it is combined with neurophysiological methods.