Automated Assessment of Discourse Coherence in Schizophrenia and Schizoaffective Disorder

Disorganized, or incoherent, speech is one of the key criteria for diagnosing schizophrenia. However, there is still a lack of an objective method for measuring speech coherence. Automated discourse analysis is a possible solution to this problem. I analyzed discourse coherence in a set of spoken narratives by people with schizophrenia or schizoaffective disorder (n = 20) and by neurotypical speakers of Russian (n = 21). All narratives were automatically rated for local and global coherence, using vector semantics methods. The discourse coherence was compared to psychiatric judgment as well as to the automatically measured performance on a verbal fluency task. People with higher psychosis symptoms showed lower coherence scores. Lower discourse coherence was also found to be associated with worse performance on verbal fluency task.