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Helping and sharing among humans is often motivated by empathy and accompanied by a sense of satisfaction. To determine whether similar self-rewarding mechanisms may underpin assistance among nonhuman primates, eight female brown capuchin monkeys (Cebus apella) underwent testing in a simple choice paradigm. Paired with a partner, subjects could select either a "selfish" option that rewarded onl...

The authors proposed a novel explanation for cultural differences in ingroup favoritism (dialecticism) and tested this hypothesis across cultures/ethnicities, domains, and levels of analysis (explicit vs. implicit, cognitive vs. affective). Dialecticism refers to the cognitive tendency to tolerate contradiction and is more frequently found among East Asian than North American cultures. In Study...