Dynamics of mother-infant parasympathetic regulation during face-to-face interaction: The role of maternal emotion dysregulation.

The dynamics of parent-infant physiology are essential for understanding how biological substrates of emotion regulation are organized during infancy. Although parent-infant physiological processes are dyadic in nature, research is limited in understanding how one person's physiological responses predict one's own and as well as the other person's responses in the subsequent moment. In this study, we examined mother-infant respiratory sinus arrhythmia (RSA) dynamics during the Still-Face Paradigm (SFP) among 106 mothers (M  = 29.54) and their 7-month-old infants (55 males). Given mothers' role in shaping dyadic interactions with their infant, we also tested how mothers' self-reported emotion dysregulation (measured via the Difficulties in Emotion Regulation Scale) associated with these dynamics. Results showed that both mothers' and infants' RSA tended to return to their respective homeostatic points (i.e., exhibited return strength) during each SFP episode, indicating stability in RSA for mother-infant dyads. Significant shifts in mother and infant RSA return strength were observed across SFP episodes, highlighting the role of contextual demands on each individual's physiological dynamics. Mother-infant RSA dynamics varied as a function of maternal self-reported emotion dysregulation. Specifically, RSA levels of infants with more dysregulated mothers had a weaker tendency to return to homeostasis during the Reunion episode and were less affected by their mothers' RSA during the Still-Face and Reunion episodes of the SFP, suggesting a less effective coregulatory influence. Our findings have implications for the intergenerational transmission of emotion dysregulation via mother-infant physiological dynamics.