Context-dependent information processing in patients with schizophrenia

Thirty schizophrenic patients fulfilling the Diagnostic and Statistical Manual of Mental Disorders IV criteria for schizophrenia and 30 control participants were shown a set of incomplete sentences, and were asked to complete them with the first word(s) that came to mind. Target sentences included an ambiguous word, the ambiguity of which was not resolved within the clause. However, completion necessarily required participants to select one specific meaning. Each target sentence was preceded by another sentence playing the role of context, which was designed to prime the less frequent meaning of the ambiguous word. The results showed that schizophrenic patients, especially those with thought disorder [on the basis of their TLC scores (Thought, Language and Communication Scale; Andreasen, N.C., 1979. Thought, language and communication disorders. Clinical assessment, definition of terms and evaluation of their reliability. Diagnostic significance. Arch. Cen. Psychiatry 39, 778-782)], used the most common meaning of the ambiguous word more frequently than controls, thus revealing a specific deficit in context use. The deficit was observed whether or not the relation between context and target sentences was made explicit. These results are in line with the cognitive models of schizophrenia that postulate a decreased ability to use context information. However, when considered in the light of prior studies (e.g., Bazin, N., Perruchet, P., 1996. Implicit and explicit memory in patients with schizophrenia. Schizophr. Res. 22, 241-248), they suggest that the deficit in processing contextual information is limited to what Baddeley (Baddeley, A.D., 1982. Domains of recollection. Psychol. Rev. 98, 708-729) called the interactive context (which affects the meaning, or the interpretation, of the target event) in contrast to the independent context (which does not interfere with the meaning-based interpretation of the target event).