I focus on the study of social development with a developmental psychopathology orientation. My main research activities attempt to understand the development of subtypes of aggressive behavior in children. Specifically, my colleagues and I have been exploring the development of relational and physical aggression (and peer victimization) during early and middle childhood. Current research also examines the development of both forms (relational and physical) and functions (proactive and reactive) of aggression as well as bullying behaviors. Current funded research addresses questions related to school readiness as children make the transition from preschool to kindergarten. Our recent and current research includes multiple methods and informants (e.g., school-based observations, teacher and parent reports, child interviews) and includes psychophysiology and biological markers (e.g., heart rate, skin conductance, hormone cortisol). Collaborative research examines similar developmental questions in a diverse longitudinal sample from birth to late adolescence. We have also been developing and testing the efficacy of an intervention (Early Childhood Friendship Project) for aggressive behavior among young children.