Despite the advancements in studying brain development in children and adolescents, little is known about changes in brain development in relation to social networks. The current project has the objective to measure brain development in relation to peer influence across the age range 10-22 years using experimental studies. These will be complemented with individual difference measures including resistance to peer-influence, school performance and peer network. We expect to show that social-emotional brain circuitry will be hypersensitive to peer-opinions in mid adolescence. This study will lead to a better understanding on how children learn and participate in a complex social world.