Evidence of Pragmatic Impairments in Speech and Proverb Interpretation in Schizophrenia

Schizophrenia has been suggested to involve linguistic pragmatic deficits. In this study, two aspects of pragmatic ability were assessed; comprehension and production. Drawing on relevance theory and Gricean implicatures to assess shared attention and interpretation in a linguistic context, discourse samples and proverb interpretation were transcribed from recorded interviews with patients with schizophrenia and control subjects. The productive aspect of implicatures was assessed by quantifying the use of 'connectors' in discourse. Receptive aspects were assessed by scoring interpretations of four common proverbs. Statistically significant effects were found: patients with schizophrenia used connectors less than controls as well as performing worse in proverb comprehension. Positive correlations between connectors and proverb interpretation in all subjects suggested an underlying pragmatic root for both productive and receptive aspects. The relative number of connectors (as a percentage of words used) provided a better index of pragmatic ability than total number because total output appeared to be influenced by additional factors such as IQ. Deficits were found in the use of connectors and in proverb interpretation even when controlling for verbal IQ, suggesting that pragmatic aspects of language are particularly vulnerable in schizophrenia compared with other verbal abilities.