Children's shyness and frontal brain maturation

Although shyness is a ubiquitous phenomenon and long viewed as a maladaptive characteristic, we know relatively little about the possible brain mechanism(s) underlying and maintaining shyness. Using a prospective longitudinal study, we examined frontal brain maturation in shy children. We collected measures of resting regional EEG spectral power approximately every six months for two years in young school-age children and characterized frontal brain maturation using a growth curve analysis of proportion of spectral power in relative faster-to-slower EEG frequencies. We found that children classified as low in shyness exhibited a significant linear growth in the proportion of overall frontal alpha power relative to delta power across assessments relative to children classified as high in shyness. High shy children displayed no growth in the proportion of overall frontal alpha power relative to delta power across assessments. These preliminary results indicate that high shy children exhibited delayed frontal brain maturation compared to low shy children. We interpret these findings within the context of a proximate explanation, suggesting links between delayed frontal maturation and emotion dysregulatory processes related to an approach-avoidance conflict. We also speculate on an ultimate explanation in which delayed frontal brain maturation may reflect neoteny (i.e., the prolongation and extension of childhood), which may have supported an adaptive function of shyness across human evolution.