Infant physiological response to the still-face paradigm: contributions of maternal sensitivity and infants' early regulatory behavior.

The current study examined the independent and additive contributions of maternal sensitivity measured prior to and following a social stressor, and infant behaviors to infants' physiological response to the still-face paradigm (SFP) in a sample characterized by poverty-related environmental risk. Ninety-one mother/infant dyads participated in the SFP when their infants were 5 months old. Maternal sensitivity was coded during the play and reunion episodes. Infant behaviors were coded during the reunion episode of the SFP while measures of heart rate (HR) and Respiratory Sinus Arrhythmia (RSA) were collected from the infants at baseline and across the SFP. Maternal sensitivity during the reunion episode predicted infants' biobehavioral reactivity and regulation, over and above maternal sensitivity during the play episode. Infants' HR decreased, and RSA increased, with greater levels of maternal sensitivity during the reunion episode. Infants also exhibited greater attentional engagement and fewer resistant behaviors with greater levels of maternal sensitivity during the reunion episode. Finally, infant behaviors predicted change in HR and RSA from the still-face to the reunion episode, above and beyond that of maternal behaviors. These findings further our understanding of the dyadic basis for the development of emotion regulation in infancy.