Chimps Donate Their Fair Share...Most of the Time

Chimpanzees may share mankind's capacity for fairness and charity, according to a study recently published in the Proceedings of the National Academy of Sciences.

Georgia University researchers used the "ultimatum game" as a litmus test for the chimps' selfish impulses. The main idea behind the test involves two sets of tokens that the subjects can choose to redeem for prizes. One token represents an equal reward for both participants, while the other favors only one. Dr. Sarah Bronson and her team taught the chimpanzees to associate each of the tokens to their respective rewards to ensure the integrity of the test. The "proposer" takes the token of their choice and hands it to their partner, who can then cash it in for the prize or refuse to exchange it if the deal is too one-sided. Although none of the Chimpanzees refused to turn in the tokens, they reportedly expressed dissatisfaction upon receiving the short end of the stick.

Darby Proctor, the principal author of the study, explains that "Humans typically offer generous portions, such as 50 percent of the reward, to their partners, and that's exactly what we recorded in our study with chimpanzees."

The team used a group of children between the ages 2 and 7 as a control group and found remarkably similar results between them and the chimps.

Senior author Sarah Bronson adds, "The chimpanzees were clearly paying attention to what their partners' outcomes were and adjusting their behavior depending on whether or not their partner could affect the outcome. If their partner couldn't do anything, they went ahead and tookt he option that gave them the most rewards. But if their partner had the potential to change the outcome, then they actually switched their behavior."

The University of Manchester's Keith Jensen, who worked on a study that suggested that fairness was a uniquely human trait, questions the study's method, notes NBC News. Jensen's argues that the animals had no grasp of the fact that refusing to cash in the token was an option.

Yet, Proctor asserts that the results "really open the door to figuring out where in our evolutionary history and what sort of adaptive pressures led to this human sense of fairness."