Fig. 1.

Participants saw two types of trials involving monetary outcomes for themselves or another person. A cue before each block indicated whether the other person would be an in-group member (NYU student) or out-group member (Columbia student). (A) On ‘free choice’ trials, participants chose between one amount of money for themselves or a different amount of money for another person. (B) On ‘forced choice’ trials, participants passively witnessed a monetary gain issued to themselves, the in-group member, or the out-group member. In both trial types, an offer stage (2–8 s) was followed by a response stage (2 s). Images are not to scale.