the day’s game on the outskirts of their village. Members of the tribe then retrieve it for sharing among the villagers. When playing the ultimatum game, the Aché typically make high offers, often more than half. So do the whale-hunting Lamalera of Indonesia, who carefully and fairly divide up the meat from killed whales.

In other societies, though, the cultural influences play out differently. In Tanzania, the Hadza share meat, but they complain about it and try to get away without sharing when they can. Nonsharers, though, risk ostracism, social scorn, and negative gossip. It makes sense, then, that when playing the ultimatum game, the Hadza make low offers, with high rejection rates.

On the other hand, high offers do not always signify a culture imbued with altruism. The Au and Gnau of Papua New Guinea often offer more than half the money, but such generosity is frequently rebuffed. The reason, it seems, is that among the Au and Gnau accepting a gift implies an obligation to reciprocate in the future. And an excessively large offer may be interpreted as an insult.

Colin Camerer, one of the economists collaborating with the anthropologists in the cross-cultural games, observes that this result is just another twist in the cultural influence on economic behavior. “Offering too much money, rather than being extremely generous, is actually being kind of mean—it’s demeaning,” Camerer explained to me. “So the money is turned down because they don’t want to be insulted, and they don’t want to be in debt.”12

The surprising results of the cross-cultural game theory experiments showed that the games were not necessarily measuring what the scientists thought they were. Rather than purely testing economic behavior, the games actually tapped into patterns of cultural practice. Players apparently tried to figure out how the game related to their real-world life and then behaved accordingly.

For instance, the Orma quickly recognized a similarity between real life and a variant of the ultimatum experiment, the public goods game (which we encountered in Chapters 3 and 4). In that game the experimenter (Jean Ensminger of Caltech) offered each

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