Neural and Behavioral Correlates of Similarity, Trustworthiness, and Stress in Decision-Making - Project Summary / Project Abstract Social influences are among the most powerful drivers of human decision-making—especially in contexts like substance use, where behaviors often emerge from implicit learning and modeling of trusted, similar peers. However, these two common social heuristics—trust and perceived similarity—are conceptually distinct but frequently confounded in both theory and practice. This project aims to dissociate these heuristics and characterize their unique and interactive effects on social decision-making, particularly under conditions of acute stress that compromise self-regulation. Participants will engage in a multi-part behavioral and neuroimaging study. In Aim 1, they will complete a trust game with fictional partners varying orthogonally in trustworthiness and similarity. Behavioral data will be modeled using a modified Social Value Model to quantify the weight placed on each heuristic. In Aim 2, participants will complete the same task under fMRI, enabling model-based analyses of the neural systems involved. Representational similarity analysis (RSA)—which captures fine-grained spatial and temporal patterns often missed by univariate approaches—will test whether trust and similarity elicit dissociable neural codes within overlapping regions such as the medial prefrontal cortex (mPFC), temporoparietal junction (TPJ), and ventral striatum (VS). In Aim 3, the task will be repeated under an acute social and physiological stressor (socially evaluated cold pressor task) to assess how stress modulates heuristic use. Behavioral, physiological, and computational measures will determine whether stress biases individuals toward similarity-based decisions and reduces trust adaptation. Together, these studies will clarify how trust and similarity guide social valuation, identify their neural signatures, and reveal how stress shifts heuristic reliance. This framework will support precise models of social decision-making and offer translational insight into health- risk behaviors. Understanding when similarity leads people to trust untrustworthy but familiar sources (e.g., substance-using peers) can inform strategies to improve decision-making in recovery contexts. Conversely, it can help identify how to build trust with dissimilar yet prosocial actors (e.g., clinicians), particularly under stress. Insights from this work may inform targeted interventions for populations vulnerable to stress-related dysregulation (e.g., adolescents, substance use disorders). The training plan includes advanced instruction in the application of computational modeling and stress physiology. These skills are essential to the applicant’s broader goal of becoming an independent investigator focused on the social, affective, and physiological factors that shape decision-making under uncertainty. By bridging social neuroscience with addiction science, this F32 will prepare the applicant to lead high-impact research on how people decide whom to trust, when to rely on intuitive heuristics, and how stress alters the balance between social learning and self-regulation. This work aligns with goals to identify mechanisms of health-related vulnerability and resilience and lays the foundation for a career dedicated to improving health through mechanistic, ecologically valid, translational research.
