Abstract
The present study maps the use of postpositional particles and auxiliary verbs to explore how these words can reflect writer's pathological mental state. Ten literary works written by Natsume Soseki(1867-1916), who is a foremost novelist in modern Japan and is known to suffer from recurrent mental symptoms by biographical and pathographical studies, were analyzed to extract linguistic information using a Japanese morphological analysis system (Chasen ). Data on the frequencies of the postpositional particles and auxiliary verbs were tested using hierarchical cluster analysis and principal component analysis. The results showed that the literary works were clustered roughly into three groups of his late thirties, early forties and late forties, which in accord with the course of the illness. Behaviormetric analysis of such function words can be a useful approach to the evaluation of writer's mental state.
