Cohesion and Coherence Analyses of Extended Written Schizophrenic Discourse: An Exploratory Case Study

Schizophrenic discourse is characterized by thought disorder, or a lack of coherence, prompting substantial research into identifying and measuring the incoherent discourse of schizophrenics. Much of this research has examined short extracts of elicited spoken data and used researcher judgments. This study examines the connectedness of naturally-occurring extensive written schizophrenic discourse using three methods of analysis: an automated analysis of cohesion, lexical cohesion analysis, and topic-based analysis focusing on propositional coherence. The results show that the schizophrenic texts are highly cohesive, especially in their use of connectives and the density of connections. The texts also show high proportions of topic shifts and a greater average distance of moves between concepts. These suggest that the topic structure of the schizophrenic texts consists predominantly of repetitive topic maintenance interspersed with short unrelated mini-topics, and it is this structure that manifests thought disorder.