Sometimes other primates are fair when it’s at no cost to themselves. Back to capuchin monkeys. Monkey 1 chooses whether both he and the other guy get marshmallows or it’s a marshmallow for him and yucky celery for the other guy. Monkeys tended to choose marshmallows for the other guy.* Similar “other-regarding preference” was shown with marmoset monkeys, where the first individual got nothing and merely chose whether the other guy got a cricket to eat (of note, a number of studies have failed to find other-regarding preference in chimps).16
