Shyness is a necessary but not sufficient condition for high salivary cortisol in typically developing 10 year-old children

Previous research has noted both high and low baseline cortisol levels in anxious personality styles. We examined the relations among shyness, baseline salivary cortisol, and resting heart rate in a non-clinical sample of 10-year-old children. As predicted, shyness was positively correlated with baseline salivary cortisol and resting heart rate, replicating and extending earlier work with preschool age children to middle childhood. However, post-hoc analyses revealed that the scatterplot of shyness and salivary cortisol was significantly triangular in shape, indicating that shyness was a necessary, but not sufficient, condition for high salivary cortisol at age 10. For children high in shyness, salivary cortisol levels ranged from low to high; for children low in shyness, salivary cortisol levels were low. This triangular pattern was not found for the association between shyness and resting heart rate, suggesting different roles of neuroendocrine and autonomic measures in relation to shyness. The potential roles of cortisol in the maintenance of shyness developmentally are discussed as are the broader implications for clarifying prior inconsistent results on the relation between temperament and cortisol in humans. The use of triangular data analytic strategies for interpreting relations between psychological variables and identification of risk and protective factors is also discussed.