“Be still my beating heart”: Linkages between mother–infant co-regulation and brief bradycardia at the onset of arm-restraint in 6-month-old infants

This study examined linkages between 6-month-old infants’ (n = 101) orienting response, measured physiologically by brief bradycardia or heart deceleration at the onset of a frustration task (maternal arm-restraint) and mother–infant co-regulation measured during a 15-min unstructured free play episode. Given the socially disruptive nature of the frustration task, we suspected that infants who experienced more positive co-regulated interactions including symmetrical (both partners actively engaged and attending to each other) or asymmetrical (one partner actively engaged while partner attends to the other) with mothers would be more likely to display an orienting response (bradycardia) during the onset of the arm-restraint procedure than infants who experience unilateral (one partner focused on other but the other focused on self), unengaged (neither partner attending to the other) or disruptive interactions. Findings indicate that dyads that experienced more asymmetrical co-regulation had infants who were more likely to experience bradycardia while unengaged interactions predicted the absence of bradycardia. These findings suggest that mother–infant co-regulation may help establish expectations about social interactions and that when these relational expectancies are violated infants are more likely to exhibit bradycardia at the onset of a socially disruptive task. Alternative explanations are also considered.

► We examined the presence of orienting bradycardia in 6-month-old infants at the beginning of an arm-restraint task.
► We examined whether the presence of an orienting bradycardia was linked to mother–infant co-regulation.
► Infants that experienced more asymmetrical co-regulation were more likely to experience bradycardia.
► Unengaged dyadic interactions predicted the absence of bradycardia.
► Co-regulation may influence expectations about social engagement and the presence of an orienting bradycardia.