From the Heart to the Mental States of Others: Linking Cardiac Autonomic Activity to Theory of Mind Ability in Young Adulthood.

Theory of mind (ToM) enables individuals to decode and attribute others' mental states to predict their behavior. While cardiac autonomic activity, particularly cardiac parasympathetic (PSNS) activity, is linked to social cognition, most previous studies infer cardiac sympathetic (SNS) activity rather than examining both simultaneously. This study aimed to investigate both cardiac PSNS and SNS activities to provide a more comprehensive understanding of ToM ability in young adults. Cardiac PSNS and SNS activities were simultaneously measured at rest in 146 participants (mean age = 20.84, SD = 2.86 years) in a cross-sectional study, and in 73 of these participants (mean age = 21.56, SD = 2.70 years) 12 months later. ToM ability was assessed using the Chinese version of the Faux Pas Recognition Test. The results indicated significant uncoupled but reciprocal associations between ToM ability and both cardiac PSNS and SNS activities. Hierarchical regression analysis further revealed that higher cardiac PSNS activity and lower cardiac SNS activity together predicted better ToM ability and its cognitive component, after controlling for possible covariates. Preliminarily, a two-wave cross-lagged panel model demonstrated a significant inverse bidirectional relationship between cardiac SNS activity and ToM ability, along with a positive predictive relationship between ToM ability and cardiac PSNS activity 1 year later. In conclusion, the present study provides direct evidence for a relationship between ToM ability and the simultaneous combination of both cardiac PSNS and SNS activities in young adults. Notably, these findings suggest the possibility that cardiac SNS activity may play an equally important, if not more crucial, role in social-cognitive processes.