Trait psychoticism is associated with greater intersubject neural dissimilarity during naturalistic social movie viewing

Psychoticism refers to maladaptive traits associated with eccentricity, perceptual dysregulation, and unusual beliefs. This study explored how individual differences in psychoticism map into neural responses during naturalistic movie-watching. By utilizing social movies with differing demands of inference, we examined how relevant correspondence of individual differences emerges as a function of movie features. A total of 157 individuals were assessed with traits of psychoticism, and intersubject correlation of neural response was assessed with functional near-infrared spectroscopy (fNIRS). Three movie-watching conditions (low-social, high-social A/B) were compared in the examination of brain-trait correspondence. The result showed that the intersubject distance of psychoticism scores corresponds to lower neural synchrony (nearest neighbor pattern), while higher scores of psychoticism correspond to decreased synchrony between individuals (Anna Karenina pattern). Moreover, such patterns were pronounced in the movie condition that required more complex mentalizing and social inference. Also, individuals with higher psychoticism traits tended to correlate with more frequent use of excessive Theory of Mind (ToM) inference during movie-watching which further supported the basis of neural idiosyncrasy. Overall findings imply that specific task demands can be more effective in provoking individual differences of psychosis-proneness. Also, individuals with psychoticism traits may undergo maladaptive interpersonal functioning possibly due to idiographic neural response characteristics and hypermentalizing tendencies.