Dynamic Flexibility in Infancy: Moment-by-Moment Biobehavioral Organization and Synchrony Across System and Context

Abstract

As humans, our sophisticated interpersonal capacities emerge from neural, biological, and behavioral systems that are intricately coordinated, both internally and with other people. However, research to date has allocated comparatively little focus to the dynamic processes of how social interactions emerge across levels of analysis, especially early in development. Second-person neuroscience (SPN) and dynamic systems approaches together offer an integrative framework for studying the development of social interactions in infancy, through quantifying flexible biobehavioral organization, interactivity within and between people, and dynamic sensitivity to context. This study builds on previous work by using a novel study design that capitalizes on the ubiquity of personal technology and leverages newly adapted methodologies for capturing the dynamic unfolding of real-time, moment-by-moment social processes. The current study quantified continuous heart rate and behavior (~360 observations per system, per person) from 44 mothers and their typically developing infants (M= 9 months) during face-to-face interaction, a perturbation (unexpected series of text messages), and recovery. Aim 1 results revealed a flexible, putative self-organizational structure for the unfolding of both infants’ behavior and their physiology, with relatively less rigid organization associated with more positive social engagement across the entire task. Results from Aim 2 found dynamic, positive linkages between infants’ parasympathetic nervous system activity and their social engagement at the subsequent second, but only while their caregiver was actively attending to them. Lastly, Aim 3 results revealed moment-by-moment parasympathetic synchrony between mothers and infants in the form of a co-regulatory feedback loop. Mothers’ parasympathetic activity positively predicted that of their infant at the subsequent second, a linkage that decreased during the task perturbation and did not fully recover upon reunion. Conversely, infant parasympathetic activity negatively predicted that of their mother at the subsequent second, a linkage that was not sensitive to social context. Together, these findings offer new ways of capturing flexibility in social interactions –through the unfolding of moment-by-moment, flexible midrange organization; cross-system linkages; and asymmetric dyadic synchrony –reflecting both stability and adjustment in the face of changing contexts. Findings from this study contribute to both basic science knowledge and potential targets for monitoring and intervention to better support adaptive social development across the lifespan.