Abstract

Parental sensitivity towards infants’ needs influences both the way caregiver-infant interactions unfold and individuals’ own development throughout lifetime. The pivotal role of this early interaction with caregivers is especially highlighted by the fact that when the interaction is non-adaptive, infants’ development may be severely hindered in various domains, such as cognitive, social, and emotional. Moreover, the quality of the early interaction with caregivers has long-lasting effects since it constitutes a lens through which individuals interpret the social world throughout lifetime. Caregivers’ influence on individuals’ subsequent behavior is also moderated by their own genetic predispositions. However the way behavioral, physiological and genetic mechanisms dynamically interact over time in shaping the development of caregiver-infant bonding and the long term effects on individuals remains largely unknown. The present project aimed to investigate behavioral and physiological mechanisms underling caregiver-infant interactions and their long-term effects applying a multilevel approach including behavioral, physiological and genetic measurements as well as a comparative approach between human and non-human primates. Specifically, in a first study focused on human adults we investigated the effect of the interaction between early parental care and individuals' own genetic predispositions in moderating adults' subsequent peripheral physiological responses to distressing social stimuli. Next, a second study on a primate model, the marmosets (\textit{Callithrix Jacchus}), focused directly on caregiver-infant dyads applying micro-behavioral analysis during infants' first month of life. Overall findings highlighted a differential importance of environmental and genetic factors in moderating caregiver-infant dyads vs individuals' long-term development. The leading role of environmental factors, namely parental behaviors, in determining infants' responses to specific caregivers within caregiver-infant interactions seems to be, on the contrary, smoothed out by individuals' own genetic predispositions when focusing on the long-term effects. Indeed, genetic characteristics determine individuals' sensitivity to environment, either weakening or strengthening the effect of environmental contribution in shaping individuals' physiological mechanisms. Also, interesting similarities between marmosets’ and humans’ caregiver-infant interactions’ structure have been found, making way for future studies investigating the brain mechanisms underlying the development of parent-infant bonding.