Hybrid Assessment Scheme Based on the Stern-Judging Rule for Maintaining Cooperation under Indirect Reciprocity

Intensive studies on indirect reciprocity have explored rational assessment rules for maintaining cooperation and several have demonstrated the effects of the stern-judging rule. Uchida and Sasaki demonstrated that the stern-judging rule is not suitable for maintaining cooperative regimes in private assessment conditions while a public assessment system has been assumed in most studies. Although both assessment systems are oversimplified and society is most accurately represented by a mixture of these systems, little analysis has been reported on their mixture. Here, we investigated how much weight on the use of information originating from a public source is needed to maintain cooperative regimes for players adopting the stern-judging rule when players get information from both public and private sources. We did this by considering a hybrid-assessment scheme in which players use both assessment systems and by using evolutionary game theory. We calculated replicator equations using the expected payoffs of three strategies: unconditional cooperation, unconditional defection, and stern-judging rule adoption. Our analysis shows that the use of the rule helps to maintain cooperation if reputation information from a unique public notice board is used with more than a threshold probability. This hybrid-assessment scheme can be applied to other rules, including the simple-standing rule and the staying rule

Reciprocity towards groups : a laboratory experiment on the causes

Field studies of conflict report cycles of mutual revenge between groups, often linked to perceptions of intergroup injustice. We test the hypothesis that people are predisposed to reciprocate against groups. In a computerized laboratory experiment, subjects who were harmed by a partner’s uncooperative action reacted by harming other members of the partner’s group. This group reciprocity was only observed when one group was seen to be unfairly advantaged. Our results support a behavioral mechanism leading from perceived injustice to intergroup conflict. We discuss the relevance of group reciprocity to economic and political phenomena including conflict, discrimination and team competition

Climate Change, Cooperation, and Moral Bioenhancement

The human faculty of moral judgment is not well suited to address problems, like climate change, that are global in scope and remote in time. Advocates of ‘moral bioenhancement’ have proposed that we should investigate the use of medical technologies to make human beings more trusting and altruistic, and hence more willing to cooperate in efforts to mitigate the impacts of climate change. We survey recent accounts of the proximate and ultimate causes of human cooperation in order to assess the prospects for bioenhancement. We identify a number of issues that are likely to be significant obstacles to effective bioenhancement, as well as areas for future research

Reciprocity towards groups

People exhibit group reciprocity when they retaliate, not against a person who harmed them, but against another person in that person's group. We tested for group reciprocity in laboratory experiments. Subjects played a Prisoner's Dilemma with partners from different groups. They then allocated money between themselves and other participants. In punishment games, subjects whose partner had defected punished participants from the partner's group more, compared to their punishment of participants from a third group. In dictator-style games, subjects did not exhibit group reciprocity. We examine possible correlates of group reciprocity, including group identification and cooperativeness

Reciprocity - an indirect evolutionary analysis

This paper investigates strategic interaction between rational agents whose preferences evolve over time. Players face a pecuniary �game of life� comprising the ultimatum game and the dictator game. Utility may but need not be attached to the reciprocation of fair and unfair play by the opponent and equitable payoff distributions as proposed by Falk and Fischbacher (2001). Evolutionary fitness is determined solely by material success � regardless of the motives for its achievement. Agents cannot explicitly condition the social component of their preferences on whether they face the ultimatum or dictator game. Under these conditions, agents develop a strong preference for reciprocation but little interest in an equitable distribution as such. This corresponds to equitable ultimatum offers but full surplus appropriation by dictators. Adding an exogenous constraint on the possible divergence between preference for reciprocation and for an equitable distribution either makes ultimatum divisions asymmetric or dictators become generous depending on the relative frequency of ultimatum and dictator interaction.

Indirect reciprocity and the evolution of prejudicial groups

Prejudicial attitudes are widely seen between human groups, with significant consequences. Actions taken in light of prejudice result in discrimination, and can contribute to societal division and hostile behaviours. We define a new class of group, the prejudicial group, with membership based on a common prejudicial attitude towards the out-group. It is assumed that prejudice acts as a phenotypic tag, enabling groups to form and identify themselves on this basis. Using computational simulation, we study the evolution of prejudicial groups, where members interact through indirect reciprocity. We observe how cooperation and prejudice coevolve, with cooperation being directed in-group. We also consider the co-evolution of these variables when out-group interaction and global learning are immutable, emulating the possible pluralism of a society. Diversity through three factors is found to be influential, namely out-group interaction, out-group learning and number of sub-populations. Additionally populations with greater in-group interaction promote both cooperation and prejudice, while global rather than local learning promotes cooperation and reduces prejudice. The results also demonstrate that prejudice is not dependent on sophisticated human cognition and is easily manifested in simple agents with limited intelligence, having potential implications for future autonomous systems and human-machine interaction

Group selection and reciprocity among Kin

The question how Darwinian mechanisms lead to the evolution of individually costly cooperative behavior has given rise to a number of hypotheses. However, attempts to build a synthesis where different types of mechanisms coexist and interact at different levels of selections are still scarce. Here we derive simple game theoretical models where the group level conflicts are resolved by group selection while simultaneously within group competition is resolved by kin selection and reciprocity. We show that none of the mechanisms, when alone, is as robust in evolving and maintaining cooperation as a synthesis of all. Furthermore, we show that initially within group conflicts can be overcome only by kin selection and not reciprocity. However, once common, different types of reciprocities can maintain high levels of cooperation even if average relatedness among individuals is lowered, groups become large, and the benefits of cooperation are reduced. Based on the synthesis we also propose a possible route to the evolution of social and eusocial systems

Is Strong Reciprocity a Maladaptation? On the Evolutionary Foundations of Human Altruism

In recent years a large number of experimental studies have documented the existence of strong reciprocity among humans. Strong reciprocity means that people willingly repay gifts and punish the violation of cooperation and fairness norms even in anonymous one-shot encounters with genetically unrelated strangers. We provide ethnographic and experimental evidence suggesting that ultimate theories of kin selection, reciprocal altruism, costly signaling and indirect reciprocity do not provide satisfactory evolutionary explanations of strong reciprocity. The problem of these theories is that they can rationalize strong reciprocity only if it is viewed as maladaptive behavior whereas the evidence suggests that it is an adaptive trait. Thus, we conclude that alternative evolutionary approaches are needed to provide ultimate accounts of strong reciprocity.

Refinement of defection strategies stabilizes cooperation

Cooperation among unrelated individuals is an enduring evolutionary riddle and a number of possible solutions have been suggested. Most of these suggestions attempt to refine cooperative strategies, while little attention is given to the fact that novel defection strategies can also evolve in the population. Especially in the presence of punishment to the defectors and public knowledge of strategies employed by the players, a defecting strategy that avoids getting punished by selectively cooperating only with the punishers can get a selective benefit over non-conditional defectors. Furthermore, if punishment ensures cooperation from such discriminating defectors, defectors who punish other defectors can evolve as well. We show that such discriminating and punishing defectors can evolve in the population by natural selection in a Prisoner's Dilemma game scenario, even if discrimination is a costly act. These refined defection strategies destabilize unconditional defectors. They themselves are, however, unstable in the population. Discriminating defectors give selective benefit to the punishers in the presence of non-punishers by cooperating with them and defecting with others. However, since these players also defect with other discriminators they suffer fitness loss in the pure population. Among the punishers, punishing cooperators always benefit in contrast to the punishing defectors, as the latter not only defect with other punishing defectors but also punish them and get punished. As a consequence of both these scenarios, punishing cooperators get stabilized in the population. We thus show ironically that refined defection strategies stabilize cooperation. Furthermore, cooperation stabilized by such defectors can work under a wide range of initial conditions and is robust to mistakes