Infancy is an extraordinary period of human development, in which babies turn sensory and environmental information into meaning in the cradle of their caregivers' affective and attentional cues. Babies express what they are thinking and feeling through smiles and gazes long before they develop expressive language. Most developmental research focuses on mother‐infant dyads within a controlled lab environment, despite the complexity of young children's caregiving ecosystems, which range far beyond the mother‐child dyad and include caregivers at a distance via technology like video chat. This study uses a novel state space approach to examine relations between the sensitivity of two caregivers—what we call “mutual sensitivity”—and infants' real‐time affective and attentional states during video chat sessions. In this analysis of recorded semi‐naturalistic video chat interactions from 47 triads (parent, infant, and on‐screen grandparent), we find that mutual sensitivity toward the infant is associated with concurrent infant positive, alert affective states (low‐medium arousal and positive valence). However, contrary to our second hypothesis, we did not find associations between mutual caregiver sensitivity and infants' real‐time likelihood that they would concurrently engage in joint attention across the video chat screen. We discuss the implications of these discrepant findings across affective and attentional domains and the utility of this newly described mutual sensitivity variable to understand children's caregiving ecosystems beyond the dyad. -goes here

Young children transition in and out of synchronous states with their caregivers across physiology, behavior, and brain activity, but what do these synchronous periods mean? One body of two-brain studies using functional near-infrared spectroscopy (fNIRS) finds that individual, family, and moment-to-moment behavioral and contextual factors are associated with caregiver-child neural synchrony, while another body of literature finds that neural synchrony is associated with positive child outcomes. Taken together, it is tempting to conclude that caregiver-child neural synchrony may act as a foundational developmental mechanism linking children’s experiences to their healthy development, but many questions remain. In this review, we synthesize recent findings and open questions from caregiver-child studies using fNIRS, which is uniquely well suited for use with caregivers and children, but also laden with unique constraints. Throughout, we highlight open questions alongside best practices for optimizing two-brain fNIRS to examine hypothesized developmental mechanisms. We particularly emphasize the need to consider immediate and global stressors as context for interpretation of neural synchrony findings, and the need for full inclusion of socioeconomically and racially diverse families in future studies.

COVID-19 disrupted infant contact with people beyond the immediate family. Because grandparents faced higher COVID-19 risks due to age, many used video chat instead of interacting with their infant grandchildren in person. We conducted a semi-naturalistic, longitudinal study with 48 families, each of whom submitted a series of video chats and surveys, and most (n = 40) also submitted a video of an in-person interaction. Families were mostly highly-educated, White/Caucasian, and lived between 1 and 2700 miles apart. We used multilevel models to examine grandparents’ and parents’ sensitivity during video chat across time (centered at February 1, 2021, the approximate date of vaccine availability). Grandparent video chat sensitivity changed as a function of date and parent sensitivity. Parent sensitivity changed as a function of date, grandparent sensitivity, and geographic distance. We then modeled infants' affective valence during video chat and in-person interactions with their grandparents, which was only predicted by grandparent sensitivity, not modality or other factors. This study demonstrates that caregivers were sensitive toward infants during video chat interactions despite fluctuations in family stress and reduced in-person contact during COVID-19 and that grandparent sensitivity predicted positive infant affect during both video chat and in-person interactions.

Children are born learning, exploring and growing.

How they will develop depends on us. We know that during the first few years of life, more than 1 million neural connections are formed every second. Young children develop through rich, daily interactions with nurturing caregivers and educators, building brains and shaping physical, socioemotional and cognitive development for life. These early years represent a unique, flexible period of human development and a finite window for high-impact investment.