Language: 日本語 English


Toshio Yamagishi
Mon, 2010-02-01
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Humans think, communicate, and behave to adapt to a particular social ecology, and by doing so they collectively create, maintain, and change the very ecology (i.e., social niche) they adapt to. The niche construction approach to culture analyzes how people induce each other to think and behave in particular ways by behaving in particular ways themselves. The best support to this approach is found when cultural differences in cognition and behavior that are regularly observed in everyday life disappears in a social vacuum – in a situation in which people are rid of any social concern about implications of their behavior and can express their thoughts and behave free of any social concern. Examples of such experimental manipulations are presented and discussed.

Takako Fujiwara-Greve and Yosuke Yasuda
Sat, 2009-06-20

In many repeated interactions, repetition is not guaranteed but instead
must be agreed upon. We formulate a model of voluntary repetition by introducing
outside options to a repeated Prisoner’s Dilemma and investigate how the structure
of outside options affects the sustainability of mutual cooperation. When the outside
option is deterministic and greater than the value of mutual defection, the lower bound
of the discount factors that sustain repeated cooperation is greater than the one for
ordinary repeated Prisoner’s Dilemma, making cooperation more difficult. However,
stochastic outside options with the same mean may reduce the lower bound of discount
factors as compared to the deterministic case. This is possible when the stochasticity
of the options increases the value of the cooperation phase more than the value of the
punishment phase. Necessary and sufficient conditions for this positive effect are given
under various option structures.

Wed, 2007-08-01

Two explanations of why shared group membership promotes cooperation in social dilemmas were compared. According to the fear-greed model of social identity proposed by Simpson (2006), shared group membership reduces greed but not fear, and, thus, should promote altruistic behavior toward in-group members in the absence of fear. According to the group-heuristic model proposed by Yamagishi and colleagues, altruistic behavior toward in-group members is a “ticket” to enter a generalized exchange system; people are not predicted to behave altruistically when it is made salience that no system of generalized exchange operates in the group. We tested these models in a dictator game experiment with two conditions. In the common knowledge condition, either model predicts greater altruism toward in-group recipients. In the unilateral knowledge condition—when the dictator knows the group membership of the recipient, but the recipient does not know the membership of the dictator—the fear-greed model predicts greater altruism toward in-group recipients. In contrast, the group heuristic model does not predict such in-group bias in altruism since. The results of the experiment clearly support the group heuristic model.