Trajectory of heart period to socioaffective threat in shy children.

Although shyness is characterized by distinct psychophysiological correlates, we know very little about the development of these correlates. In this longitudinal study, we examined how children's shyness was associated with trajectories of heart period (HP) to socioaffective threat across four assessments spanning approximately 2 years. Children (M  = 6.39 years) viewed age-appropriate, socioaffective videos at each visit while having their HP measured concurrently. A growth curve analysis revealed that low shy children had a relatively lower HP at enrollment, but experienced increases in HP across visits, while high shy children exhibited relatively stable low HP across visits while viewing threat-related socioaffective video stimuli. These patterns did not exist for HP during resting baseline or HP to nonthreatening video stimuli. These findings suggest that longitudinal patterns of HP among shy children may reflect a stable, characteristic way of responding to socioaffective threat, and possibly a physiological mechanism underlying shyness in some children.