Project Summary/Abstract Approximately 9.1% of US adolescents (11.2% girls, 7.0% boys) experience social anxiety,1 a disorder characterized by difficulty with and fear of social interactions.2 Peer social interactions are the building blocks of socioemotional and neural development during adolescence. Processes important for social interaction, including social attention and mentalizing, the ability to interpret the intentions and emotions of others,3 are in flux during adolescence,4,5 with puberty playing a particularly influential role in reorienting attention towards peers6 and the development of the mentalizing network7 and behavior.8 Puberty may be a sensitive period during which the integration of social attention and mentalizing processes could solidify or alter trajectories towards social anxiety, particularly in individuals already at elevated risk for social anxiety. The current grant will capitalize on two separate samples (one cross-sectional and one longitudinal) to examine puberty as a sensitive period for the integration of social attention and mentalizing processes (both behavioral and neural) and risk for social anxiety. Study 1 will use cross-sectional data, collected in 11- and 12-year-old adolescents. Adolescents will complete an fMRI mentalizing task and participate in a social interaction while mobile eye- tracking data are collected. The social interaction will be coded for mentalizing language/behaviors. Adolescents will be assessed for, and self-report, pubertal status. Through Study 1, I will examine puberty as a sensitive period for the integration of naturalistic social attention and spontaneous mentalizing (Aim 1). Study 2 will use longitudinal data from a completed dataset. Adolescents were assessed for fearful temperament, a risk factor for social anxiety,9 at 2 years. Adolescents participated in a social interaction and self-reported pubertal status at 12 years. Participants self-reported social anxiety at 15 years. As in Study 1, the social interaction will be coded for mentalizing language/behaviors. Through Study 2, I will examine puberty-linked longitudinal relations between spontaneous mentalizing, fearful temperament and social anxiety (Aim 2). Findings will provide information about the role of puberty in socioemotional development and risk for social anxiety. The current study is designed with an integrated training plan that will prepare the fellowship applicant for a future career as a developmental social neuroscientist. The three overarching training goals are: 1) Advanced training in naturalistic neuroscience methodology and data analysis and mentalizing. 2) Obtain conceptual and methodological training in puberty and associated psychopathology risk. 3) Advance training and professional development in preparation for an independent research career. These training goals will effectively prepare the applicant for the next steps in the desired career path of becoming a developmental social neuroscientis...