London, Oct 5 : Chimpanzees have a very different concept of fairness, a new study by researchers from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, has revealed.

In experiments, the scientists found that chimpanzees were more focussed on the immediate outcome of a transaction rather than the overall fairness of the deal.

As part of the study, the scientists devised a game in which a player can either accept or reject a portion of money that has been divided up by an anonymous partner.

Previous studies with humans had revealed that players often rejected the deal – meaning neither person got anything – when the deal represented too small a fraction of the total sum.

Humans generally placed a huge emphasis on equity in deal brokering – so much so often caused them to make irrational economic decisions, the scientists said.

“Humans are rather strange in the propensity to compare one's own outcomes with others,” said Keith Jensen at the Max Planck Institute.

However, chimpanzees, the researchers found, placed no such emphasis on equity.

As part of the experiments, Jensen and colleagues designed a set-up whereby two chimps – separated by a Plexiglas divide – had to divvy up 10 raisins.

The first chimp would select how to split the raisins up by pulling on a length of rope attached to a tray covered with the fruit. The second chimp could accept the deal by pulling in a rod to bring the tray forward, thus allowing both animals to access their portions.

If the second chimp refused the offer, neither would get anything.

The results of the trial, which involved 11 chimps in total, showed how differently the animals responded to an unfair deal compared to humans.

In situations where the first chimp decided against an even split in favour of offering up only two raisins (keeping eight for itself), the second chimp accepted the deal 95 percent of the time.

By comparison, a previous study had shown that only 55 percent of humans would accept such a measly share of the spoils when they knew their partner could have divided the rewards equally.

“These are important results, because they suggest that the willingness to bear costs to punish others who do not cooperate is a uniquely human trait,” said James Fowler of the University of California, San Diego, US.

Fowler, however, said the chimps did not play the “ultimatum game” anonymously, making a direct comparison with humans more difficult.

“One limitation of this study is that the chimpanzees played both roles, allowing for the possibility of reciprocity,” said Sarah Brosnan at Georgia State University in Atlanta, US.

Brosnan said the chimps were from a stable social group, “which in previous studies had been shown to limit negative responses to inequity”.

Daniel Fessler, an altruism expert at the University of California, Los Angeles, US, said that the chimps involved in the experiment might not have understood full deal-making opportunity of the game.

“The claim that chimps don't care about fairness is premised on the assumption that the subjects interpret this as a social interaction,” New Scientist magazine quoted Fessler as saying.

The study appears in the journal Science. (ANI)