Learning from financial rewards and punishments reduces the in-group bias in social approach without changing the in-group bias in impressions.

Humans' approach behaviour and impressions are biased towards individuals from their own group (in-group) compared with different groups (out-group). There is evidence that learning from specific interactions with in-group and out-group members can reduce these in-group biases, but it is yet unclear if learning from non-social reinforcers, such as financial rewards and punishments, can have similar effects. Here, we conducted three independent studies by using different versions of a novel approach-avoidance learning task, intergroup impression ratings and computational learning models. In the approach-avoidance learning task, participants moved a manikin representing themselves towards or away from one of two symbols, representing in-group or out-group individuals or which had no social meaning. Approach was financially rewarded with varying probabilities. Our results confirmed initial in-group biases in approach and impression ratings. Rewarding out-group approach significantly reduced the in-group bias in approach, with stronger learning from rewards compared with punishments. In contrast, the in-group bias in impressions remained unchanged. Two further studies showed that learning-related changes in approach are larger in social compared with non-social contexts and require varying reward probabilities. Together, these findings show that learning from financial rewards or punishments can improve out-group approach but not out-group impressions.