Chimps: More Rational than Humans?

The ultimatum games feels like the most overused example of behavioral economics at this point, but it's nonetheless interesting. (Basically it's a game where people are asked to split some monetary amount, say $10, between two parties. The first party makes an offer and the second either accepts, taking their share and giving the offerer theirs, or declines, in which case neither party gets any money. Though rational economic theory would predict a person offers the smallest non-zero amount -- $1 if we're going with offers of whole numbers -- and that the person on the other end would accept any non-zero amount. The thing is, it doesn't work that way and most people won't accept an offer they don't deem to be fair.) Okay, so with that out of the way, it turns out that in this case chimps are actually more rational than we are:

Chimpanzees, however, go about the ultimatum game (which involves divisions of raisins in their case) without giving fairness any thought. In this experiment, the researchers found that the chimp responders tended to accept any nonzero offer, however unfair. And conversely, the chimp proposers rarely suggested a fair division, choosing instead to maximize their own share.