Temperament, social competence, and adrenocortical activity in preschoolers.

The relations among temperament, social competence, and levels of a stress-sensitive hormone (salivary cortisol) were examined in two studies of preschoolers children (Study 1, N = 29; Study 2, N = 46). In both studies, we sampled cortisol daily for the initial weeks of school year (Group Formation period) and for several weeks later in the year (Familiar Group period). For each child, we examined two measures of cortisol activity (separately for each period) based on the distribution of cortisol levels across days: (a) median cortisol (50th percentile) and (b) cortisol reactivity (the difference between the 75th and 50th percentile). Median cortisol was modestly stable across periods, but cortisol reactivity was not. Children who showed high cortisol reactivity (75th minus 50th percentile > or = 0.10 micrograms/dl) during the Group Formation period but low-to-normal cortisol reactivity during the Familiar Group period were outgoing, competent, and well liked by their peers. In contrast, children who changed from low/normal to high cortisol reactivity and those who maintained high cortisol reactivity from the Group Formation to Familiar Group period were affectively negative and solitary. Children who showed high median cortisol during the Familiar Group period or over both periods scored lower on a measure of attentional and inhibitory control. Together, these results suggest that relations among temperament, social competence, and neuroendocrine reactivity reflect both individual and contextual differences.