Cognitive disorders have long assumed a central position in describing the pathognomonic characteristics of schizophrenia. Kraepelin's (1902) and Bleuler's (1911) uniquely innovative descriptions of attentional dysfunctions and associational loosening in thought processes laid the groundwork for the concept of basic disorder devised by authors who embraced a phenomenological approach to psychopathology in German-speaking countries (Huber, 1983; Janzarik, 1983), and for experimental research endeavours in English-speaking countries to identify a ‘core psychological deficit’ in schizophrenia (Lang & Buss, 1965). Recent research has identified specific information-processing deficits in affected individuals. These include (a) problems with elementary functions such as selective attention towards relevant stimuli and sustained attention over prolonged periods of time (Oltmanns & Neale, 1975; Nuechterlein, 1977); (b) problems with more complex functions such as encoding and recognition of familiar cues, storing information for future retrieval, or drawing deductive or analogous conclusions from available information (Broga & Neufeld, 1981; Brenner, 1983; Nuechterlein & Dawson, 1984b); and (c) problems with executive functions and response selection (Broen & Storms, 1967; Weinberger et al, 1986, 1988).