Project Summary/Project Abstract The ability to socially navigate the world has been strongly linked to health and well-being in humans and across a wide range of human psychological disorders and depends on prosocial choices in affiliative environments and strategic learning in competitive ones. These kinds of social decisions involve balancing tradeoffs between maximizing rewards for oneself versus others and learning from others’ reward preferences. Neuroimaging studies have shown that human decisions in interpersonal economic games recruit neural structures associated with social cognition and reward valuation. While previous studies have shown that dopamine function is paramount to decisions involving rewards for oneself, it’s role in social decisions is much less well understood. Since disruptions to social decision making span multiple psychopathologies linked to dopamine dysfunction (like ADHD and schizophrenia), it is critical to understand the mechanism by which dopamine influences social decisions about rewards. To address this, the F99 phase of this proposal will investigate the relationship between dopamine function and social decision making in humans. Specifically, this work will combine positron emission tomography (PET), pharmacology, computational modeling, and behavioral experiments to address how individual differences in dopamine relates to personal reward processing and decision making as well as prosocial and strategic social decisions. Results from these studies will provide critical information about the role of dopaminergic modulation of multiple forms of social decisions and may eventually shed light on disruptions to prosocial behavior and social learning across psychopathologies. Completion of the F99 phase sets a strong intellectual, technical, and professional foundation for the postdoctoral (K00) phase of this award. During the K00 phase, training will include: learning new methods to study dynamic social interactions, understanding how dopamine and other neuromodulators support social decisions, and testing whether differences in affiliative or competitive decisions contribute to observed differences in psychopathology. These goals will support the development of knowledge, expertise, and skills essential to becoming an independent investigator.