On identifying the processes underlying schizophrenic speech disorder.

Speech of people with schizophrenia is often difficult to follow. There is evidence that neuropsychological deficits associated with schizophrenia explain some of the variance in speech disorder, but its nature and causes overall are not well understood. This study rated speech samples from 60 schizophrenic outpatients for thought disorder, conceptual disorganization, linguistic structural breakdown, and communication failure. A battery of neuropsychological tests potentially relevant to coherent speech production was administered, and associations between these variables and the speech measures were assessed. Consistent with previous research, the measure of functional effect, communication failure, was more highly associated with neuropsychological test performance than were the measures of putative cause: thought disorder, conceptual disorganization, or linguistic structural breakdown. Performance on tests of attention, immediate memory, working memory, organizational sequencing, and conceptual sequencing all were significantly related to the frequency of communication failures in the speech. In hierarchical regression, attention, working memory, and conceptual sequencing each contributed significantly and together explained 29% of the variance. Some other potential contributors to test in future research include auditory attention, internal source memory, emotional disturbances, and social cognitive deficits.