Coordinated social behavior and positive affect shared between parent and child in early life provide a foundation for healthy social and emotional development. We examined physiological (cardiac vagal responses) and relational (attachment security) predictors of dyadic behavioral coordination in a sample of 13-month-old infants and their mothers (N = 64). We tested whether cardiac vagal responses moderated the association between attachment security and behavioral coordination. The main effect of attachment on coordination was moderated by infant cardiac vagal tone (i.e., respiratory sinus arrhythmia [RSA] during rest). Securely attached infants with lower cardiac vagal tone were more behaviorally coordinated with their mothers; there was no association between attachment and coordination for infants with high cardiac vagal tone. Infants with greater increases in cardiac vagal reactivity (i.e., RSA during social engagement) exhibited greater behavioral coordination with their mothers regardless of attachment status. There were no effects for maternal cardiac vagal responses. These results illustrate how individual differences in physiological responses inform healthy early social-emotional functioning.
Keywords: RSA; attachment; cardiac vagal reactivity; cardiac vagal tone; dyad.