ScienceDaily (Oct. 7, 2007) — New research from the Max Planck Institute of Evolutionary Anthropology in Leipzig, Germany shows that unlike humans, chimpanzees conform to traditional economic models.

The research used a modification of one of the most widely used and accepted economic tools, the ultimatum game.

In the ultimatum game - which was developed by another German, Werner Güth, now at the Max Planck Institute for Economics in Jena - one person, the proposer, is given money by an experimenter. That proposer can then divide the "manna from heaven" with a second person, the responder. The responder is not powerless - if he accepts the division, both people take home the offered amounts. But if he rejects it, both get nothing. The fear of having an unfair offer rejected causes the proposer to make a fair offer. People typically make offers of close to 50%. Anything less is likely to be rejected. Sensitivity to unfair offers and a willingness to pay a cost to punish someone contradicts economic models of pure self-interest, and they have been claimed to be unique to humans.

In this study, the researchers confronted our closest living relatives, chimpanzees, to a simplified version of the ultimatum game. The proposer would propose an offer of raisins to the responder by partially pulling out a tray of raisins as far as he could. If the responder accepted the division of raisins, he would pull the tray the rest of the way and the two would be able eat. However, if the responder did not like what he saw, he would not pull the tray and neither of them would get anything to eat.

In each version of this mini-ultimatum game, the proposer could pull one tray with 8 raisins for himself and 2 for the other (an unfair split that people routinely reject). However, the proposer would have a choice. In one game, he could choose between this unfair offer and a fair one (5 raisins each). In another, he could choose a hyper-fair option (2 for himself and 8 for the responder). In a third, he had no choice (the second tray also had 8 for himself and 2 for the other). In the fourth game, the proposer's other choice was hyper-unfair (10 for himself, 0 for the responder).

Unlike humans faced with these games, chimpanzee responders accepted any nonzero offer, whether it was unfair or not. The only offer that was reliably rejected was the 10/0 option (responder gets nothing). The researchers conclude that chimpanzees do not show a willingness to make fair offers and reject unfair ones. In this way, they behave like selfish economists rather than as social reciprocators.

Reference: Keith Jensen, Josep Call, Michael Tomasello Chimpanzees are rational maximizers in an ultimatum game, Science, October 5, 2007

enlarge

Frodo may not have a sense of fair play, however he knows what is good for him. Here he is waiting for the keepers to distribute food in the Wolfgang Köhler Primate Research Center. (Credit: Katrin Riedl)

Related Stories

Genes Influence People's Economic Choices (Oct. 4, 2007) — Genes exert influence on people's behavior in a very common experimental economic game. Traditionally, social scientists have been quite hesitant to acknowledge a role for genes in explaining ...  > read more

Who's Bad? Chimps Figure It Out By Observation (Mar. 31, 2008) — Chimpanzees make judgments about the actions and dispositions of strangers by observing others' behavior and interactions in different situations. Specifically, chimpanzees show an ability to ...  > read more

Why Don't Chimpanzees Like To Barter Food? (Feb. 5, 2008) — Scientists examines the circumstances under which chimpanzees, our closest relatives, will exchange one inherently valuable commodity (an apple slice) for another (a grape), which is what early ...  > read more

Human-like Altruism Shown In Chimpanzees (June 25, 2007) — Experimental evidence reveals that chimpanzees will help other unrelated humans and conspecifics without a reward, showing that they share crucial aspects of altruism with humans. The evolutionary ...  > read more

Chimpanzees Show Quality Of Relationship Drives Sense Of Fairness (Feb. 15, 2005) — The evolution of the sense of fairness may have involved the quality of relationships, according to behavioral researchers at the Yerkes National Primate Research Center in ...  > read more

Search ScienceDaily

Surviving Hard Hits