My mother is sensitive, but I am too tired to know: infant sleep as a moderator of prospective relations between maternal sensitivity and infant outcomes.

This study investigated the moderating role of infant sleep in the connections between maternal sensitivity and three indicators of infant functioning: attachment security, theory of mind, and executive functioning (EF). Maternal sensitivity was assessed when infants (27 girls and 36 boys) were 1 year of age. Infant sleep was assessed with actigraphy at age 2; attachment security, theory of mind, and EF were also assessed at age 2. Results indicated that maternal sensitivity was positively related to attachment security only among infants who got more sleep at night, and to conflict-EF and theory of mind only for infants who got greater proportions of their sleep during the night. These results suggest that sleep may enhance the benefits of maternal sensitivity for some aspects of infants' functioning, providing further support for the importance of sleep maturation as a salient developmental task of infancy.