Abstract: Many experimental studies indicate that people are motivated by reciprocity. Rabin (1993) develops techniques for incorporating such concerns into game theory and economics. His model, however, does not fare well when applied to situations with an interesting dynamic structure (like many experimental games), because it is developed for normal form games in which information about the sequential structure of a strategic situation is suppressed. In this paper we develop a theory of reciprocity for extensive games in which the sequential structure of a strategic situation is made explicit. We propose a new solution concept— sequential reciprocity equilibrium—which is applicable to extensive games, and we prove a general equilibrium existence result. The model is applied in several examples, including some well known experimental games like the Ultimatum game and the Sequential Prisoners’ Dilemma.

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This paper uses a three-games (or triadic) design to identify trusting and reciprocating behavior. A large literature on single-game trust and reciprocity experiments is based on the implicit assumption that subjects do not have altruistic or inequality-averse other-regarding preferences. Such experimental designs test compound hypotheses that include the hypothesis that other-regarding preferences do not affect behavior. In contrast, experiments with the triadic design do discriminate between transfers resulting from trust or reciprocity and transfers resulting from other-regarding preferences that are not conditional on the behavior of others. Decomposing trust from altruism and reciprocity from altruism or inequality aversion is critical to obtaining empirical information that can guide the process of constructing models that can increase the empirical validity of game theory.

In constructing improved models of human behavior, both experimental and behavioral economists have increasingly turned to evolutionary theory for insights into human psychology and preferences. Unfortunately, the existing genetic evolutionary approaches can explain neither the degree of prosociality (altruism and altruistic punishment) observed in humans, nor the patterns of variation in these behaviors across different behavioral domains and social groups. Ongoing misunderstandings about why certain models work, what they predict, and what the place is of “group selection ” in evolutionary theory have hampered the use of insights from biology and anthropology. This paper clarifies some of these issues and proposes an approach to the evolution of prosociality rooted in the interaction between cultural and genetic transmission. I explain how, in contrast to non-cultural species, the details of our evolved cultural learning capacities (e.g., imitative abilities) create the conditions for the cultural evolution of prosociality. By producing multiple behavioral equilibria, including group-beneficial equilibria, cultural evolution endogenously generates a mechanism of equilibrium selection that can favor prosociality. Finally, in the novel social environments left in the wake of these cultural evolutionary processes, natural selection is likely to favor prosocial genes

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Most economic models are based on the self-interest hypothesis that assumes that all people are exclusively motivated by their material self-interest. In recent years experimental economists have gathered overwhelming evidence that systematically refutes the self-interest hypothesis and suggests that many people are strongly motivated by concerns for fairness and reciprocity. Moreover, several theoretical papers have been written showing that the observed phenomena can be explained in a rigorous and tractable manner. These theories in turn induced a new wave of experimental research offering additional exciting insights into the nature of preferences and into the relative performance of competing theories of fairness. The purpose of this paper is to review these recent developments, to

Gender is rarely included as a factor in economics models. However, recent work in experimental economics, as well as in psychology and political science, suggests that gender is an important determinant of economic and strategic behavior. We examine gender differences in bargaining using the ‘‘trust game’ ’ introduced by Joyce Berg et al. (1995). 1 In this two-person game, the ‘‘proposer’ ’ is given a choice of sending some, all, or none of his or her $10 experimental payment to an anonymous partner, the ‘‘responder.’ ’ The experimenter triples any money sent. The responder then chooses how much of his or her total wealth (his or her $10 experimental payment plus the tripled money) to return to the proposer. Any money the responder does not return may be kept (thus the responder is playing a dictator game with his or her endowment plus three times the amount the proposer sent). The unique subgame-perfect Nash equilibrium is for the proposer to send no money and for the responder to return none. For U.S. subjects, Berg et al. found that 30 of 32 proposers deviated from this economic equilibrium and sent some money to their partners (the average amount sent was $5.16). In

Abstract We examine the characteristics and relative strength of third-party sanctions in a series of experiments. We hypothesize that egalitarian distribution norms and cooperation norms apply in our experiments, and that third parties, whose economic payoff is unaffected by the norm violation, may be willing to enforce these norms although the enforcement is costly for them. Almost two-thirds of the third parties indeed punished the violation of the distribution norm and their punishment increased the more the norm was violated. Likewise, up to roughly 60% of the third parties punished violations of the cooperation norm. Thus, our results show that the notion of strong reciprocity extends to the sanctioning behavior of ''unaffected'' third parties. In addition, these experiments suggest that thirdparty punishment games are powerful tools for studying the characteristics and the content of social norms. Further experiments indicate that second parties, whose economic payoff is reduced by the norm violation, punish the violation much more strongly than do third parties.

Most contracts, whether between voters and politicians or between house owners and contractors, are incomplete. “More law,” it typically is assumed, increases the likelihood of contract performance by increasing the probability of enforcement and/or the cost of breach. This paper studies a contractual relationship where the first mover has to decide whether she wants to enter a contract without knowing whether the second mover will perform. We analyze how contract enforceability affects individual performance for exogenous preferences. Then we apply a dynamic model of preference adaptation and find that economic incentives have a non–monotonic impact on behavior. Individuals perform a contract when enforcement is strong or weak but not with medium enforcement probabilities: Trustworthiness is “crowded in” with weak and “crowded out” with medium enforcement. In a laboratory experiment we test our model’s implications and find support for the crowding prediction. Our finding is in line with the recent work on the role of contract enforcement and trust in formerly Communist countries.

Exploiting moral wiggle room: Experiments demonstrating an illusory preference for fairness