The strong reciprocity model of the evolution of human cooperation has gained some acceptance, partly on the basis of support from experimental findings. The observation that unfair offers in the ultimatum game are frequently rejected constitutes an important piece of the experimental evidence for strong reciprocity. In the present study, we have challenged the idea that the rejection response in the ultimatum game provides evidence of the assumption held by strong reciprocity theorists that negative reciprocity observed in the ultimatum game is inseparably related to positive reciprocity as the two sides of a preference for fairness. The prediction of an inseparable relationship between positive and negative reciprocity was rejected on the basis of the results of a series of experiments that we conducted using the ultimatum game, the dictator game, the trust game, and the prisoner’s dilemma game. We did not find any correlation between the participants’ tendencies to reject unfair offers in the ultimatum game and their tendencies to exhibit various prosocial behaviors in the other games, including their inclinations to positively reciprocate in the trust game. The participants’ responses to postexperimental questions add support to the view that the rejection of unfair offers in the ultimatum game is a tacit strategy for avoiding the imposition of an inferior status.

In a series of experiments, we demonstrate that certain players of an economic game reject unfair offers even when this behavior increases rather than decreases inequity. A substantial proportion (30 -40%, compared with 60 -70% in the standard ultimatum game) of those who responded rejected unfair offers even when rejection reduced only their own earnings to 0, while not affecting the earnings of the person who proposed the unfair split (in an impunity game). Furthermore, even when the responders were not able to communicate their anger to the proposers by rejecting unfair offers in a private impunity game, a similar rate of rejection was observed. The rejection of unfair offers that increases inequity cannot be explained by the social preference for inequity aversion or reciprocity; however, it does provide support for the model of emotion as a commitment device. In this view, emotions such as anger or moral disgust lead people to disregard the immediate consequences of their behavior, committing them to behave consistently to preserve integrity and maintain a reputation over time as someone who is reliably committed to this behavior. emotion ͉ fairness ͉ reciprocity E motions, rather expressed publicly or experienced only privately in the absence of observers, may serve us well in the long run. Experimental research on economic games provides intriguing insights into this phenomenon in the context of understanding constraints on self-regarding behavior. The ultimatum game (1-5) is the game most often used in the social sciences to demonstrate the existence of preferences that are not strictly self-regarding such as inequity aversion and reciprocity. The ultimatum game is played by 2 players-a proposer and a responder. The proposer, is provided $X by the experimenter and then given the opportunity to make a proposal concerning how to divide the money with the responder. The responder is given 2 alternatives-to either accept or reject the proposal. If the proposal is accepted, each player receives the amount specified in the proposal. If the proposal is rejected, neither party receives any money. In a typical experiment, the responder does not know who the proposer is and the two never meet. Furthermore, the game is played only once. As a result, it is not possible for a responder to reject an unfair offer to communicate directly to the proposer that she should behave more fairly in the future.According to the self-regarding actor model typically used in economic game theory a rational, cognitively competent selfregarding responder should accept any proposal that provides some money, no matter how small the amount. A rational proposer who expects this response should therefore propose to give the minimal non-0 amount to the responder. However, the results of ultimatum game experiments generally do not support this prediction. The modal division proposed is a 50-50 split, and extremely unfair proposals are rare (2, 3). Furthermore, the majority of responders typically reject unfair offers that give them Ͻ20-30% o...

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Previous research has suggested that the spontaneous display of positive emotion may be a reliable signal of cooperative tendency in humans. Consistent with this proposition, several studies have found that self-reported cooperators indeed display higher levels of positive emotions than non-cooperators. In this study, we defined cooperators and non-cooperators in terms of their behavior as the proposer in an ultimatum game, and video-taped their facial expressions as they faced unfair offers as a responder. A detailed analysis of the facial expressions displayed by participants revealed that cooperators displayed greater amounts of emotional expressions, not limited to positive emotional expression, when responding to unfair offers in the ultimatum game. These results suggest that cooperators may be more emotionally expressive than non-cooperators. We speculate that emotional expressivity can be a more reliable signal of cooperativeness than the display of positive emotion alone

Japanese participants in Study 1 exhibited a self-effacing tendency when no reason for their self-evaluation was provided. However, they exhibited a self-enhancing tendency when they were offered a monetary reward for the correct evaluation. In Study 2, Americans, especially American men, exhibited a self-enhancing tendency whereas Japanese exhibited a self-effacing tendency when no reason for making the evaluation was presented. This cultural difference disappeared when participants were provided with a monetary reward for correctly evaluating their performance level. These results support the view that the modesty observed in self-evaluation among Japanese participants is a 'default strategy' to avoid offending others.