Researchers in Atlanta gave some capuchin monkeys a choice. They could get a food reward, or they could get a food reward and also have another monkey receive food. And it depended on just who the other monkey was.
When they were paired with a relative or a "friend," the monkeys primarily went for the double reward.
But they weren't so generous with strangers, choosing the "selfish" option instead of what's described as the "pro-social" choice.
The researchers at Emory University don't know if the giving amounts to a self-reward for the monkeys because they can eat together, or if the monkeys just like to see another monkey enjoying the food.
The lead researcher says, "They seem to care for the welfare of those they know."
The research appears in the Proceedings of the National Academy of Sciences.