Performing a motor action enhances associative learning in the absence of choice

Forming pavlovian associations is fundamental to human behaviour. From gambling to social interactions, rewards are frequently preceded by motor actions. While studies have shown that making a choice enhances reward learning, in many cases (e.g. playing a slot machine), actions are performed without control over outcomes. We investigated the impact of performing an action on reward processing and associative learning in the absence of choice. We used a task in which coloured houses were probabilistically associated with social reward or punishment. On a trial-wise basis, we randomised whether participants pressed a button prior to observing the outcome, or waited passively. Using fMRI we explored the impact of performing an action on reward processing. Contrary to our hypotheses, we did not find reward-related activity in the striatum, nor a modulation of striatal activity by performing an action. Instead, we found tentative evidence for enhanced reactivity to negative outcomes in active trials in areas associated with affective processing and memory formation. Cues predicting positive outcomes were associated with enhanced activity in the temporo-parietal junction and precuneus. In a second, behavioral study, we used a forced-choice task testing the formation of stimulus-outcome associations. Participants preferred stimuli associated with reward over those associated with punishment. Both approach and avoidance were enhanced for stimuli learned in active trials. These findings suggest that performing a motor action enhances pavlovian-type associative learning, and may facilitate the neural processing of outcomes. This has important implications for our understanding of human learning, as well as gambling and other reward-driven behaviours.