What Who really wakes first when the baby cries? For new parents, the birth of a baby brings drastic reductions in sleep duration and quality, which are particularly acute in the first year postpartum. Parents’ sleep is typically disrupted by their baby’s crying, with crying representing a highly effective method for babies to elicit adult attention. The loss of sleep is generally more pronounced for mothers than fathers, but can be challenging for both parents. This work will explore the fundamental responses to infant signalling that govern early parenting and ultimately impact parents’ sleep patterns. These responses will be investigated in both fathers and mothers, and across countries with divergent levels of work-related support for parents. Why Most of our knowledge about early parenting, and its effect on sleep, comes from studies of mothers. Fathers have largely been neglected in parenting research - although they constitute ~50% of parents. One reason for the relative lack of understanding of fathers' roles is that mothers are studied during day-time hours because they are more often at home providing care. Night-time therefore provides a valuable study window, because both partners are typically in the home. There are also stark differences between countries in their statutory provision of paternity leave. Through a cross-country comparison, this project will investigate how the availability of paternity leave, along with other socio-cultural factors, impacts patterns of caregiving and sleep. How This project will examine how men and women respond to infant signalling at night, and the impact on their sleep patterns. In a series of cumulative studies, adults will be tested who are not yet parents, along with adults who have had their first baby. Participants will be drawn both from Denmark and internationally, in countries with contrasting parental care provisions. Combining laboratory sleep assessments, new at-home sleep monitoring technologies, and large-scale real-time reporting using smartphones, this project will provide the most detailed analysis to date of how parents respond to, and share the care of, their infant at night. SSR Becoming a parent is amongst our greatest life transitions. New parents need to navigate sleep disruption, the demands of caregiving and our changing expectations about childcare roles. This work will aim to better understand how men and women, with different access to parental leave, cope with the new demands on their sleep from their babies. This work will also address the widely-held notion that men are simply less responsive and sensitive to babies, less engaged in their caregiving, and ultimately less important in child development than women.