Interpersonal synchrony is associated with infants’ reactions to subtle changes in caregiver-infant interactions

The present study examined the role of interpersonal synchrony between mothers and their 4-month-old infants (N = 40) in infant responses to a modified interaction where mothers continually looked and verbalised towards but did not engage with their children. During a natural interaction we observed behavioural synchrony and for a subsample of infants (n = 20) measured change in their salivary oxytocin from before to after the interaction. During the modified interaction we observed infant gaze, positive, and negative affect. We found that higher interpersonal synchrony was related to longer infants’ social gaze and shorter displays of negative affect during the modified interaction. Increase in infant oxytocin was also associated with longer gaze, but also longer negative and shorter positive affect during the modified interaction. Our results show that interpersonal synchrony allows infants to notice changes in interactions with others, but also helps them to regulate their emotions during such modified exchanges. These findings thus indicate the importance of synchrony experiences with caregivers for the development of early regulatory capacities.