Associations between trait shyness and cerebellar spontaneous neural activity are mediated by behavioral inhibition

Abstract

Shyness, a personality trait characterized by discomfort and inhibition in social contexts, has a profound impact on individuals' social functioning. Despite its significance, the specific neural mechanisms underlying shyness remain poorly understood. The 2 × 2 model of shyness and sociability posits that shyness arises from a conflict between approach and avoidance motivations. Within this framework, the Behavioral Inhibition System (BIS) and Behavioral Activation System (BAS) are widely regarded as reliable proxies for these opposing motivational tendencies. Therefore, this study employed resting-state fMRI and ReHo analyses to investigate the relationship between trait shyness and spontaneous neural activity in 42 healthy students (M_age = 21.36 ± 2.56), along with the mediating role of the BIS/BAS in this relationship. ReHo analysis revealed a significant association between lower spontaneous neural activity in the posterior cerebellum and higher levels of shyness; moreover, the BIS system partially mediated this link, whereas the BAS system showed no significant mediating effect. Robustness checks using inverse mediation analysis confirmed the specificity and robustness of this hypothesized pathway. These findings highlight the cerebellum's role in modulating individual differences in shyness through localized neural synchrony and emphasize the BIS system as a key mediator, offering potential implications for targeted interventions aimed at enhancing social adaptation in shy individuals.