Marmosets evaluate third-party reciprocity

What is it about?

This paper describes that marmoset monkeys socially evaluate human actors after observing third-party interactions either of balanced or unbalanced reciprocal behaviors: The marmoset monkeys accepted food less frequently from those who were not reciprocal in social exchange with others than those who were. The present results suggest that this social evaluation is not specific to humans, and does not require perspective-taking, or language.

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Why is it important?

The present study suggests that other-regarding behaviors in marmosets seem to have evolved regardless of the more sophisticated cognitive structures found in capuchins, chimps and humans, all of which have proportionally larger brains. Rather, we propose such other-regarding behavior occurs due to pro-social traits, evolved within primate groups independently, and not necessarily among the ancestors common to capuchins and humans.