Both capuchin monkeys and chimpanzees have a sense of fairness (and of being cheated)

In September 2003, CBC News reported that capuchin monkey seem have a sense of fairness.

In a recent study, brown capuchin monkeys trained to exchange a granite token for a cucumber treat often refused the swap if they saw another monkey get a better payoff — a grape.

When both monkeys were given a cucumber slice after handing over the token, they completed the trade 95 percent of the time.

But when one was given the tastier grape for the same amount of work, the rate of cooperation from the other monkey fell to 60 percent, with the cheated primate sometimes throwing the token, refusing the cucumber or giving the cucumber to the other monkey. And when one didn’t have to do anything to get a grape, the other made the trade for the cucumber only 20 percent of the time.

The refusal to make the exchange increased as the experiment went on, the researchers reported.

Now Scientific American reports that the chimps have a similar sense of fairness suggesting that we all probably inherited it from a common ancestor.