Trait anxiety drives premature disengagement despite intact opportunity-cost sensitivity
Anxiety has been linked to difficulty sustaining engagement with ongoing tasks, even when continued engagement would yield greater rewards, yet the underlying mechanisms remain unclear. Here we examined how trait anxiety shapes sequential foraging decisions using a patch-leaving task grounded in the Marginal Value Theorem (MVT), a normative framework for explore-exploit decisions previously used to reveal altered computations in conditions such as problem gambling and attention-deficit hyperactivity disorder. Across two independent cohorts, participants adjusted patch residence times according to environmental opportunity costs, indicating preserved sensitivity to task structure irrespective of anxiety levels. Despite this, individuals with higher trait anxiety consistently left patches earlier and accrued fewer rewards. Drift diffusion modeling revealed that these deviations arose from reduced reward-driven evidence accumulation, rather than impaired environmental sensitivity or altered learning: trait anxiety reliably reduced the drift rate governing continued exploitation, providing a computational account of premature disengagement. This effect remained robust after accounting for pupil-linked arousal and baseline stress biomarkers, including salivary -amylase and cortisol, which independently constrained decision dynamics. Together, these findings identify reduced reward-evidence accumulation as a core mechanism through which anxiety promotes premature disengagement from rewarding environments.