Increasing response vigour under time pressure as a transdiagnostic marker of eating disorders

Eating disorders (EDs) are characterised by extreme concerns about food and weight. These concerns are linked to changes in decision-making, such as persisting with actions that are no longer rewarding. This study tested whether people with eating disorder symptoms show increased persistence due to altered decision thresholds for behavioural adaptation. A group with heightened concerns about eating (ED; N=48) and a healthy control group (HC; N=56) completed a foraging task, in which an option on screen was exploited for reward. With each decision to exploit, reward feedback decreased and participants had to decide when to move on to a new option. Each block was time limited to 7.5 minutes. Behavioural persistence was measured as the number of seconds spent exploiting each option. Decision thresholds were measured when deciding to move on, as the counterfactual reward that would have been received for an exploit action. We predicted that the ED group would show increased persistence and decreased decision thresholds (i.e. lower counterfactual reward when deciding to move on). We found no evidence for these predictions. Instead, exploratory analyses showed that the ED group exhibited progressively faster response times (RTs) when approaching the time limit for each block. This increase in motor vigour correlated with the severity of eating disorder symptoms and total rewards earned. Our results point to changing motor vigour as a potential transdiagnostic marker of ED tendencies.