PROJECT SUMMARY Heightened performance monitoring and overcontrol (HPM/OC) is a transdiagnostic phenotype comprised of perfectionism, extreme concern for errors, cognitive inflexibility and excessive need for control. There is increasing evidence that the HPM/OC phenotype is identifiable in early childhood and underlies obsessive- compulsive disorder (OCD), social anxiety disorder (SAD) and anorexia nervosa (AN). These psychiatric disorders are severe, chronic, and treatment-resistant disorders with high rates of comorbidity. However, there is surprisingly little research examining the neurobiological and behavioral mechanisms that make up the HPM/OC phenotype in early school-age childhood in relation to the development of transdiagnostic psychiatric symptoms. Moreover, it is unknown how the HPM/OC phenotype interacts with rapid developmental progression during this age or is influenced by social-contextual features, such as social evaluation, peer rejection or parenting styles. Determining answers to these fundamental questions could provide insight into the emergence of the HPM/OC phenotype and provide novel treatment targets for early intervention. The goal of the current proposal is to improve understanding of the HPM/OC phenotype in early childhood in relation to early markers of OCD and SAD by assessing the developmental progression of cognitive facets of performance monitoring and reactive versus proactive cognitive control and the influence of social-contextual features on psychiatric outcomes. We posit that cognitive processes that make up the HPM/OC phenotype, including heightened performance monitoring and more reactive versus proactive cognitive control, interact with various social contexts to differentiate early school-age children with impairing HPM/OC. The early school- age period is when HPM/OC is first evident and is a time of rapid cognitive and social development, making it a pivotal time to understand the developmental psychopathology of this presentation. We will employ cutting- edge and cost-effective electroencephalogram (EEG) event-related potential (ERP) and time-frequency (TF) analyses to examine multiple Research Domain Criteria (RDoC) constructs across three repeated yearly assessments in a sample of 300 community children oversampled for elevated dimensional HPM/OC, ages spanning 4 - 9 years. This fine-grained evaluation will provide an opportunity to characterize 1) how HPM/OC impacts normative neurodevelopmental trajectories of RDoC constructs during an age of high neural plasticity, 2) the developmental progression of cognitive facets of the HPM/OC phenotype in relation to transdiagnostic psychiatric impairment and 3) the impact of social-contextual features that may influence these relationships. This knowledge could have far-reaching effects on our understanding of the early neurodevelopment of the HPM/OC phenotype prior to disorder onset, which could inform early identification of high-risk children and targete...