Keith Jensen, Josep Call and Michael Tomasello. Chimpanzees Are Rational Maximizers in an Ultimatum Game. Science 5 October 2007:Vol. 318. no. 5847, pp. 107 – 109.

I am always playing catch up with my issues of Nature and Science and this is no exception. One of the main frustrations of game theoreticians in sociology is that humans do not behave like rational players. Ironically enough that does not seem to be a problem for those of us that use game theory in biology. In nature individuals of a species seek to maximise their benefit (otherwise they become extinct).

In their paper Jensen and coauthors show how chimpanzees,our closest relatives, do play like rational players in the ultimatum game. In the Ultimatum game one of the players offers how to split a particular item and then the other players decides whether to accept or reject the offer. If the offer is rejected then none of the players gets anything. Humans tend to reject what they perceive as unfair deals (like 20-80 or more skewed) and seldom offer deals more skewed than 60-40. Chimpanzees on the other hand where likely to offer unfair deals and when offered, they were likely to accept them.