Abstract
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.