The Evolution of Generosity in the Ultimatum Game.
When humans fail to make optimal decisions in strategic games and economic gambles, researchers typically try to explain why that behaviour is biased. To this end, they search for mechanisms that cause human behaviour to deviate from what seems to be the rational optimum. But perhaps human behaviour is not biased; perhaps research assumptions about the optimality of strategies are incomplete. In the one-shot anonymous symmetric ultimatum game (UG), humans fail to play optimally as defined by the Nash equilibrium. However, the distinction between kin and non-kin-with kin detection being a key evolutionary adaption-is often neglected when deriving the "optimal" strategy. We computationally evolved strategies in the UG that were equipped with an evolvable probability to discern kin from non-kin. When an opponent was not kin, agents evolved strategies that were similar to those used by humans. We therefore conclude that the strategy humans play is not irrational. The deviation between behaviour and the Nash equilibrium may rather be attributable to key evolutionary adaptations, such as kin detection. Our findings further suggest that social preference models are likely to capture mechanisms that permit people to play optimally in an evolutionary context. Once this context is taken into account, human behaviour no longer appears irrational.
BEACON Center for the Study of Evolution in Action, Biomedical and Physical Sciences Building, 567 Wilson Road Room 1441, East Lansing, MI 48824, USA.|Department of Integrative Biology, Michigan State University, 288 Farm Lane RM 203, East Lansing, MI 48824, USA.|Department of Computer Science and Engineering, Michigan State University, 428 South Shaw Lane RM 3115, MI 48824, USA.
Arend
A
Hintze
Center for Adaptive Rationality, Max Planck Institute for Human Development, Berlin, Germany.
Ralph
R
Hertwig
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