Influences of early dyadic and triadic interactions on infants’ heart rate responses

Early family interactions are one of the strongest predictors of children’s emotional development throughout the years (Favez et al., 2017; Hébert et al., 2021; Tissot et al., 2022). Most of the studies on infants’ physiological regulation, as a specific indicator of emotion regulation abilities, have been conducted in parent-infant dyads (Morris et al., 2007; Rodrigues et al., 2021; Tronick & Beeghly, 2011). Yet, the social context of the child is more complex and includes triadic interactions involving both the mother and the father (Fivaz-Depeursinge & Corboz-Warnery, 1999). To date, no study has been conducted to examine how triadic vs dyadic interactions affect physiological arousal regulation at a family level. Here, using an observational paradigm (Lausanne Trilogue Play), we investigated how the family context modulates heart rate (beats per minute, bpm) in a cohort of 4-5-month-old infants and their parents. Results show that the interactive context (triadic and dyadic scenes) modulates the Heart Rate (HR) response. The child displays higher arousal activation (bpm) in the triadic exchange vs. the dyadic exchange (F(1, 4)=164.04; p<.01). Conversely, both mothers (F(1, 4)=944.06; p<.01) and fathers (F(1, 4)=428.83; p<.01) reduce physiological activation during triadic interactions compared to dyadic interactions. Thus, during the parental interaction the child's heart rate further increases, while parents’ heart activation decreases. For the infant, this pattern of activation may reflect a greater self-regulatory effort related to the increased stimulation in triadic interactions and the lack of external regulation in the parental exchange. For parents, the presence of the adult partner seems to reduce physiological activation. Results suggest that early triadic interactions and dyadic exchanges specifically shape physiological arousal responses.