The development of aggression in middle childhood : longitudinal analyses of the role of anger regulation social rejection and peer socialization Background: The engagement in aggressive behavior in middle childhood is linked to the development of severe problems in later life. Thus identifying factors and processes that con tribute to the continuity and increase of aggression in middle childhood is essential in order to facilitate the development of intervention programs. The present PhD thesis aimed at expand ing the understanding of the development of aggression in middle childhood by examining risk factors in the intrapersonal and interpersonal domains as well as the interplay between these factors: Maladaptive anger regulation was examined as an intrapersonal risk factor; processes that occur in the peer context (social rejection and peer socialization) were included as interpersonal risk factors. In addition in order to facilitate the in situ assessment of anger regulation strategies an observational measure of anger regulation was developed and validated. Method: The research aims were addressed within the scope of four articles. Data from two measurement time point…