Brain structure links extraversion to shyness in late adolescence

Shyness is a prevalent psychological construct that can lead to psychopathology and negative developmental outcomes, yet its neurostructural substrates remain poorly understood, particularly during adolescence-a critical period for social and emotional development. This study examined the brain gray matter volume correlates of shyness and the potential mediating role of basic personality traits in 228 normal adolescents (aged 16-20 years). Participants underwent structural magnetic resonance imaging and completed the Cheek and Buss Shyness Scale and NEO Five-Factor Inventory. Whole-brain voxel-based morphometry and cross-validation prediction analyses revealed a positive association between shyness and gray matter volume in the right dorsolateral prefrontal cortex, a key region implicated in cognitive control and emotion regulation. Among the Big Five traits, only extraversion correlated with right dorsolateral prefrontal cortex gray matter volume and showed a significant indirect association with the gray matter volume-shyness link. Specifically, higher right dorsolateral prefrontal cortex gray matter volume was associated with lower extraversion, which in turn was associated with greater shyness; this indirect association was partial and remained significant after controlling for other personality traits. These results highlight the importance of integrating neural and personality factors in understanding shyness during this critical developmental period and offer potential targets for early identification and intervention.