Schizophrenics show a failure in the decoding of violations of conversational implicatures

Recent approaches to the 'theory of mind' and pragmatics support that, if we did not have any idea about what other people know, we could hardly use language effectively. Successful communication (the pragmatic aspect of language) depends on inferring the beliefs and intentions of the partner in the conversation. Such successful communication is linguistically realized in part by cohesion and in part by abiding by the maxims derived from the cooperative principle. However, the violations of the Gricean implicatures are generally used in everyday language, mainly to point at a hidden, most commonly negative opinion on others. We hypothesize that schizophrenics have difficulties in the decoding of these violations, as the core deficit in this disorder is around social cognition, theory of mind and pragmatic language use.

We have examined 26 paranoid schizophrenic patients and 26 normal control subjects by using 4 'question and answer' vignettes, where the Gricean maxim of relevance was violated to express a hidden, negative opinion by one partner during the communicative act. The subjects were asked to judge these opinions and were evaluated by the investigators on a score from 0 to 2 points. In a pilot study, interrater reliability was judged to be satisfactory. The data were analysed statistically by parametric and non-parametric tests.

Statistical analyses of our data have shown that schizophrenics made significantly more mistakes during the decoding of the violated maxim as compared with controls (p < 0.0001), reflecting on the difficulties during the correct exploration of the social context, i.e. recognition of the speaker's hidden opinion.

We conclude that patients with schizophrenia fail to decode intentional violations of conversational implicatures. These results point at a dysfunctional pragmatic language use among schizophrenic patients.