The cerebellum supports two systems for understanding others in early childhood

Abstract

The cerebellum has increasingly been implicated in Theory of Mind (ToM), a hallmark of human social cognition. Yet its role in the development of social understanding remains poorly understood, despite evidence linking early cerebellar disruptions to profound social cognitive deficits. Although explicit ToM reasoning emerges only around four years of age, preverbal infants already excel at predicting others actions, raising the question of how the cerebellum supports social cognition early in development. Here, we investigated structural cerebellar correlates of ToM (explicit false belief understanding) and nonverbal action prediction in children aged 3-4 years, a critical developmental period during which explicit ToM emerges. Greater gray matter volume in Crus II, a core node of the adult cerebellar ToM network, was associated with better explicit ToM performance. By contrast, nonverbal action prediction was linked to distinct, non-overlapping clusters in inferior lobule VIIB and the posterior vermis, regions implicated in action observation and salience processing in adults. These cerebellar regions further exhibited dissociable patterns of covariance with cerebral networks, linking Crus II to the canonical ToM network and VIIB/vermal regions to salience-related areas. Our findings reveal neuroanatomically distinct cerebellar substrates supporting two separable components of early social cognition: one anchored to explicit mental-state reasoning and another to an earlier-emerging nonverbal action prediction system potentially grounded in the processing of salient social cues. Together, these findings identify the cerebellum as a key contributor to multiple stages of social cognitive development and suggest that distinct cerebellar systems scaffold the emergence of mature social understanding.