Altered Theory of Mind Engagement and Neural Alignment in Social Anxiety During Movie Viewing.

Background: Social anxiety (SA) is marked by a persistent fear of social scrutiny, but its neurocognitive mechanisms remain incompletely understood. We tested whether SA is associated with altered engagement of theory of mind (ToM) systems supporting inferences about others' thoughts and emotions or with broader interpretive tendencies biasing social information processing toward more internally guided responses. Methods: Functional magnetic resonance imaging, heart rate, and pupil diameter were recorded from 43 individuals with elevated SA and 43 control individuals with low SA during viewing of a nonverbal animated film. ToM engagement was assessed via scene-specific neural activation, while broader interpretive processing was indexed using dynamic intersubject correlation (ISC), quantifying the degree to which neural responses were shared versus idiosyncratic across viewers over time. Results: Participants with elevated SA showed reduced activation in the left posterior superior temporal sulcus during ToM-relevant scenes, as well as preserved engagement of the broader ToM network. Dynamic ISC analyses revealed increased alignment in early sensory regions and reduced alignment in higher-order regions outside the ToM network, consistent with more individualized processing at higher levels. These effects occurred without group differences in autonomic arousal or pupil-linked attention, and an exploratory comparison with an autism cohort revealed opposite alignment patterns in overlapping higher-order regions. Conclusions: SA is associated with focal alterations in ToM-related processing and broader shifts in movie-driven neural alignment across the cortical hierarchy. Divergent alignment patterns in SA and autism suggest that movie-driven neural alignment may serve as a transdiagnostic marker distinguishing mechanistically distinct forms of atypical social cognition.