Differential associations between behavioral and cortisol responses to a stressor in securely versus insecurely attached infants.

In this study we examined whether securely versus insecurely attached infants use different regulatory behaviors in absence of their mother and whether these regulatory behaviors are differentially associated with physiological stress responses in secure versus insecure infants. Participants were 193 one-year-olds and their mothers. During three 3-min episodes of separation from the mother in the Strange Situation Procedure (SSP) [1], the following infant regulatory behaviors were observed: crying, fussing, self-soothing, manipulation of toys, and manipulation of the door. Salivary cortisol was measured at baseline and 25, 40, and 60min after the SSP to measure reactivity and recovery. Additionally, infants were classified as securely or insecurely attached to their mothers. During the mother's absence, secure infants engaged more in manipulation of the door than insecure infants. Furthermore, in insecure (but not secure) infants less fussing was associated with higher cortisol reactivity, while in secure (but not insecure) infants more self-soothing was associated with higher cortisol reactivity. In total, 29% of the variance in cortisol reactivity was explained by infant regulatory behaviors in the mother's absence. Cortisol recovery was not predicted by infant regulatory behaviors in the mother's absence. To conclude, the results show differential associations between behavioral and cortisol responses to a stressor in secure versus insecure infants. This might indicate that secure and insecure infants apply different behavioral regulatory strategies when physiologically stressed.