This is an individual National Research Service Award for post-doctoral research training, which provides support for promising Fellowship Applicants with the potential to become productive, independent investigators in scientific health-related research fields. Children with autism spectrum disorder exhibit lower levels of emotion regulation as compared to typically developing children. Using a developmental psychopathology perspective, this longitudinal project proposes to examine the developmental trajectories of emotion regulation across the first three years of life in two groups of children: 150 low-risk infants with a typically developing older sibling and 75 high-risk infants with an older sibling with autism spectrum disorder. At 6 months of age the temporal associations between infant facial expressions and gaze direction will be examined. Similar relationships will be examined during the second and third year when toddlers participate in a frustrating prohibition task. Finally, the project will use infant and toddler emotion regulation to predict individual differences in developmental outcomes during the third year, including social competence. This is an important first step to understanding the origins of individual differences that set infants on diverse paths of vulnerability or resilience to later risk. Examination of the developmental trajectories of emotion regulation may help to inform early intervention programs and shed light on the emergence of autism symptomatology.