Dynamical quantification of schizophrenic speech.

Schizophrenic speech has been studied both at the clinical and linguistic level. Nevertheless, the statistical methods used in these studies do not specifically take into account the dynamical aspects of language. In the present study, we quantify the dynamical properties of linguistic production in schizophrenic and control subjects. Subjects' recall of a short story was encoded according to the succession of macro- and micro-propositions, and symbolic dynamical methods were used to analyze these data. Our results show the presence of a significant temporal organization in subjects' speech. Taking this structure into account, we show that schizophrenics connect micro-propositions significantly more often than controls. This impairment in accessing language at the highest level supports the hypothesis of a deficit in maintaining a discourse plan in schizophrenia.