Mother-infant dyadic reparation and individual differences in vagal tone affect 4-month-old infants' social stress regulation

Infants’ social stress regulation (i.e., reactivity and recovery) might be affected by mother-infant dyadic functioning and infants’ vagal tone (i.e., Respiratory Sinus Arrhythmia, RSA). This study investigated the role of a specific dyadic functioning feature (i.e., dyadic reparation) and individual differences in vagal tone regulation (i.e., RSA suppression vs. non-suppression) in relation to social stress regulation in 4-month-old infants. Sixty-five mother-infant dyads participated in the Face-to-Face Still-Face paradigm. Social stress reactivity and recovery were measured as Negative emotionality during Still-Face and Reunion episodes, respectively. RSA was measured during Play, Still-Face and Reunion. Suppressors had higher dyadic reparation during Play and higher recovery from social stress, compared to non-suppressors. Higher reparation during Play associated with lower reactivity and higher recovery, only for suppressors. Findings suggest a joint role of infants’ RSA individual differences and dyadic reparation in affecting infants’ social stress regulation at 4-month-age