The Early Childhood Friendship Project to reduce aggression and bullying in preschoolers

The purpose of this study is to assess the impact of the Early Childhood Friendship Project (ECFP) on changes in aggression/peer victimization subtypes, prosocial behavior, and social and academic competence with a teacher-implemented (with coaching) version of the program. Further, investigators will examine whether changes in executive functioning, emotion regulation, and hostile attribution biases indirectly account for the program effects. Investigators will test if physiological reactivity (skin conductance and respiratory sinus arrhythmia) serves as moderators of intervention effects. Data will be collected from 600 children (30 randomly assigned preschool classrooms) diverse in socioeconomic status and race/ethnicity. Investigators will use multiple methods (school-based observations, direct academic assessments, child interviews, physiological reactivity using two tasks, observer, caregiver, and teacher reports) to assess the efficacy of the program, hypothesized mechanisms, and role of physiology as a moderator of intervention effects. The duration of the effects will be tested at both 4 month and 12-month follow-up and will thus demonstrate the impact the program has on children's school readiness and transition to kindergarten. It is expected that preschool children randomly assigned to the ECFP intervention relative to the control condition will show significant and moderate reductions in physical and relational aggression/victimization at post-test and follow-up; the ECFP intervention group will also show increases in prosocial behavior, social competence, and academic competence, relative to the control group at post-test and follow-up (4-months at the end of preschool and 12 months after transitioning to kindergarten). Additionally, it is hypothesized that changes in executive functioning, emotion regulation, and hostile attribution biases will mediate treatment effects from baseline to respective follow-ups. It is anticipated that these hypothesis will be moderated by gender such that effects will be stronger for girls relative to boys. Finally, it is hypothesized that physiological reactivity will act as a moderator of intervention effects and of the executive functioning, emotion regulation, and hostile attribution biases mechanisms.