PROJECT SUMMARY Sensitive and responsive caregiving interactions in early childhood, characterized by appropriate responses to a child’s cues, provide the foundation for healthy emotional and behavioral development across the lifespan. Infancy is a particularly critical period for these sensitive interactions with caregivers, given the important contribution of these interactions to the development of infants’ ability to self-regulate. Infants learn to self- regulate through co-regulation with the mother; therefore, supporting maternal wellbeing and healthy maternal- infant co-regulation is an important strategy for promoting emotional and behavioral development. One evolving and modifiable threat to these sensitive interactions is the mobile device, which has become deeply interwoven into the fabric of family life, with nearly universal adoption. A growing body of evidence suggests that due to their engaging design and portability, mobile devices may uniquely interfere with a caregiver’s ability to sensitively respond to their young children’s cues. This prior work, however, has not examined in a comprehensive model during infancy potential pathways of association between maternal mobile device use, maternal wellbeing, infant regulation, and maternal-infant co-regulation. Examining these potential associations among low-income, first-time mothers and their infants may be especially important, given the buffering role that sensitive maternal-infant interactions can have against psychosocial stress and the patterns of caregiving that become established during the transition to motherhood. Examining these pathways of association longitudinally across infancy would allow for identification of both key targets for intervention and the critical developmental periods during which to intervene upon these targets. Therefore, in a cohort of 230 low-income, first-time mother-infant dyads, we will measure maternal mobile device use, maternal wellbeing, infant regulation, and maternal-infant co-regulation at three time points in infancy to address the following aims: Aim 1: To characterize maternal mobile device use with regard to quantity, type of app, and intent. Aim 2: To test pathways of association between maternal mobile device use, maternal wellbeing, infant regulation, and maternal-infant co-regulation at infant ages 3, 6, and 12 months. Aim 3: To identify temporal relationships between maternal mobile device use, maternal wellbeing, infant regulation, and maternal-infant co-regulation across infant ages 3, 6 and 12 months. The PI, Dr. Munzer, is a developmental-behavioral pediatrician whose growing research program seeks to understand parenting in the digital age, and how it contributes to children’s wellbeing. With the support of a multidisciplinary team of mentors, Dr. Munzer will gain experience in mobile device sampling; observed and reported measures of maternal wellbeing, infant regulation, and maternal-infant co-regulation; and structural equ...