MONDAY, Jan. 14 (HealthDay News) -- Chimpanzees have a sense of fairness previously believed to be uniquely human, according to a small new study.
The study included six adult chimpanzees and 20 human children, aged 2 to 7, who played what is called the Ultimatum Game.
In the game, a participant chose between two different colored tokens that, with a partner's cooperation, could be exchanged for rewards. The chimpanzees were offered food and the children were offered stickers.
One color of token provided equal rewards to both partners, while the other color favored the individual making the choice and shortchanged their partner. The chooser had to give the token to the partner, who then exchanged it with a researcher for the reward. This way, both partners needed to be in agreement.
Both the chimpanzees and the children responded in a way typically seen in adult humans. If the partner's cooperation was required, the chimpanzees and children split the rewards equally. But if an individual had a passive partner who had no chance to reject the offer, the chimpanzees and children chose the selfish option.
The findings, published online in the new issue of the journal Proceedings of the National Academy of Sciences, suggest that a sense of fairness comes from a common ancestor of both humans and apes, said the researchers at the Yerkes National Primate Research Center at Emory University in Atlanta.
"Until our study, the behavioral economics community assumed the Ultimatum Game could not be played with animals or that animals would choose only the most selfish option while playing," study co-author Frans de Waal said in a university news release. "We've concluded that chimpanzees not only get very close to the human sense of fairness, but the animals may actually have exactly the same preferences as our own species."
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