Contextual constraint and the recall of verbal material in schizophrenia: the effect of thought disorder.

Some research indicates that thought-disordered schizophrenics produce language utterances that are less predictable than those of non-thought-disordered schizophrenics and controls. We examined the hypothesis that thought-disordered schizophrenics would have a parallel deficiency in the ability to use the predictabilities provided by contextual constraint to improve recall of heard language passages. Subjects were seventeen schizophrenics, ten normal controls, and twelve psychiatric controls, evaluated by standardized psychiatric interview and diagnosed according to research criteria. The data obtained supported the hypothesis and non-thought-disordered schizophrenics performed similarly to controls in the experimental task. Failure to classify schizophrenic subjects on the dimension of though disorder may result in misleading comparisons of general samples of schizophrenics with controls on tasks requiring language perception and production.

The predictability of thought disordered speech in schizophrenic patients.

Previous research has resulted in inconsistent findings regarding the predictability of schizophrenic speech samples. It was hypothesized that the predictability of schizophrenic speech varies as a function of clinically manifest thought disorder. In an experiment based on the Cloze procedure, raters were asked to predict ten passages of schizophrenic speech and eight passages of normal speech under conditions of fourth- and fifth-word deletion. Differences emerged between the samples only for the fifth-word deletion procedure. When the schizophrenic samples were grouped according to the presence of thought disorder, thought-disordered speech was significantly less predictable than normal and non-thought disordered schizophrenic speech. Furthermore, non-thought-disordered schizophrenic speech was no less predictable than normal speech. It is concluded that schizophrenia should be more carefully defined and that thought disorder should be routinely assessed in future investigations.