LAUSR

BACKGROUND AND OBJECTIVES Dysfunction in reward processing is a hallmark feature of depression. In the context of reinforcement learning, previous research has linked depression with reliance on simple habit-driven ('model-free') learning strategies over more complex, goal-directed ('model-based') strategies. However, the relationship between depression and habit-breaking remains an under-explored research area. The current study sought to bridge this gap by investigating the effect of depressive symptoms on habit formation and habit-breaking under monetary and social feedback conditions. Additionally, we examined whether spontaneous eyeblink rate (EBR), an indirect marker for striatal dopamine levels, would modulate such effects. METHODS Depressive symptoms were operationalized using self-report measures. To examine differences in habit formation and habit breaking, undergraduate participants (N = 156) completed a two-stage reinforcement learning task with a devaluation procedure using either monetary or social feedback. RESULTS Regression results showed that in the monetary feedback condition, spontaneous EBR moderated the relationship between depressive symptoms and model-free strategies; individuals with more depressive symptomatology and high EBR (higher dopamine levels) exhibited increased reliance on model-free strategies. Depressive symptoms negatively predicted devaluation sensitivity, indicative of difficulty in habit-breaking, in both monetary and social feedback contexts. LIMITATIONS Social feedback relied on fixed feedback rather than real-time peer evaluations; depressive symptoms were measured using self-report rather than diagnostic criteria for Major Depressive Disorder; dopaminergic functioning was measured using EBR rather than PET imaging; potential confounds were not controlled for. CONCLUSIONS These findings have implications for identifying altered patterns of habit formation and deficits in habit-breaking among those experiencing depressive symptoms.