Trajectories of mother-infant synchrony in response to stress: developmental stability and impact of maternal childhood trauma and infant temperament

 Young infants largely depend on their primary caregivers to regulate their emotions. While considerable research has explored infant and maternal behaviour and physiology during this process, few studies have explored trajectories of behaviour and physiology in response to a stressor concurrently, dyadically, and longitudinally. This dissertation addressed these limitations. In a community sample (N = 108), maternal and infant Respiratory Sinus Arrythmia (RSA) reactivity and behavioural synchrony after exposure to a brief dyadic stressor (i.e., StillFace Paradigm) was assessed when infants were 3.5 months and 7 months of age. Contrary to hypotheses, neither infant nor maternal RSA or behavioural synchrony significantly changed during the 2-minute recovery episode. Trajectories of RSA did not significantly co-vary between mother and infant and were not significantly related to changes in behavioural synchrony. However, when maternal exposure to childhood trauma was added to the model, variability in trajectories was indicated. Infants of mothers reporting higher levels of childhood trauma exposure showed higher initial RSA reactivity and a steeper decline in RSA reactivity across the recovery period. A significant increase in RSA reactivity across the recovery period was also seen for infants who were rated by mothers as showing more negative affectivity. Interestingly, these covariates were significant at 7 months but not at 3.5 months, suggesting a possible influence of development or experience within the mother-infant relationship. A comprehensive and critical analysis of these results in light of extensive heterogeneity of findings and iv operationalization of constructs in this area of study are provided, along with insights to guide future research.