The language system in schizophrenia: effects of capacity and linguistic structure.

Dysfunction in receptive language processes has been reliably observed in individuals diagnosed with schizophrenia and their first degree family members. The present study addressed the unresolved issue of whether receptive syntax is intact in schizophrenia. The principal question concerned whether comprehension dysfunction in schizophrenia involves a disturbance in the processing of syntactic structure, a susceptibility to demands placed on temporal auditory processing, or some combination of these two general factors. Comprehension accuracy was compared between 32 males diagnosed with schizophrenia and 22 males with no lifetime diagnosis of psychiatric disorder. Accuracy was examined for responses to Who questions ("Who did X?" and "Who was done X?") about information in the sentential clauses (main vs. relative) of two types of relative sentences (subject-relatives vs. object-relatives) that were presented aurally at conversational and accelerated rates. The relationship between cognitive functions and comprehension accuracy was also tested. Results showed highly significant effects of diagnosis, syntactic structure, and temporal demand. Patients were characterized by reduced overall comprehension accuracy compared to controls. More important, patients and controls differed in their patterns of accuracy across the different types of syntactic structure. Finally, cognitive functions predicted but did not completely account for comprehension accuracy. Findings suggest the hypothesis that receptive syntax is disrupted in schizophrenia, and this dysfunction may not be entirely explained by compromised general cognitive ability.