Loneliness biases social engagement decisions: Evidence from value-based choice models

Loneliness is a well-established risk factor for adverse mental health outcomes and persistent social withdrawal. We tested whether loneliness is associated with systematic alterations in value-based social decision making and examined mechanisms that may sustain withdrawal. Across two preregistered online studies (total N = 6,517), participants were randomly assigned to optimism, pessimism, or neutral expectation priming and completed a vignette-based task manipulating reward, effort, and threat. Loneliness and psychopathological symptoms were assessed by self-reports. Across both studies, higher loneliness was consistently associated with a lower likelihood of engaging in social interactions, independent of vignette characteristics and expectation priming. This association was partially mediated by reduced anticipated connectedness and elevated perceived rejection risk and remained robust after adjustment for psychopathological symptoms. Computational analyses further indicated that loneliness was associated with reduced sensitivity to both social reward and social threat, accompanied by diminished differentiation between high- and low-reward contexts, consistent with a compressed range of subjective social value across decision scenarios. These findings suggest that loneliness is linked to altered social valuation, characterized by blunted differentiation of social rewards and reduced motivational salience of potentially beneficial interactions, contributing to persistent withdrawal across diverse everyday social contexts.