Social inequity disrupts reward-based learning

Through reward-based learning, people learn which actions generate which outcomes in which situations. What happens to human reward-based learning when outcomes are shared? Here we show that learning is impacted by inequity in the distribution of rewards (self-other) and others' identity. In three experiments, participants could learn how different actions, in response to different stimuli, generated different monetary rewards, each split between the participant and a member of a particular social group. Overall, participants learned more slowly and less successfully when they received a smaller (vs larger) share of the total reward. Stereotypes about the partner's social group additionally modulated learning rates when cognitive load was reduced, with lower perceived warmth or competence hampering learning from the partner's share. Computational modeling showed participants' learning was best explained by adapting the standard reinforcement learning model to account for stereotypes and inequity information, demonstrating that social context modulates non-social learning processes.