Title: Human Altruism - Proximate Patterns and Evolutionary Origins
Author: Ernst Fehr / Urs Fischbacher
Page: 6-47

Abstract: Are people selfish or altruistic? Throughout history this question has been answered on the basis of much introspection and little evidence. It has been at the heart of many controversial debates in politics, science, and philosophy. Some of the most fundamental questions concerning our evolutionary origins, our social relations, and the organization of society are centered around issues of altruism and selfishness. Experimental evidence indicates that human altruism is a powerful force and unique in the animal world. However, there is much individual heterogeneity and the interaction between altruists and selfish individuals is key for understanding the evolutionary dynamics as well as the proximate patterns of human cooperation. Depending on the environment, a minority of altruists can force a majority of selfish individuals to cooperate or, conversely, a few egoists can induce a large number of altruists to defect. Current gene-based evolutionary theories cannot explain important patterns of human altruism pointing towards the need for theories of cultural evolution and gene-culture coevolution.

Title: Behavioral Game Theory and Contemporary
Author: Herbert Gintis
Page: 48-72

Abstract: It is widely believed that experimental results of behavioral game theory undermine standard economic and game theory. This paper suggests that experimental results present serious theoretical modeling challenges, but do not undermine two pillars of contemporary economic theory: the rational actor model, which holds that individual choice can be modeled as maximization of an objective function subject to informational and material constraints, and the incentive compatibility requirement, which holds that macroeconomic quantities must be derived from the interaction and aggregation of individual choices. However, we must abandon the notion that rationality implies self-regarding behavior and the assumption that contracts are costlessly enforced by third parties.

Title: Altruists with Green Beards
Author: Ernst Fehr / Urs Fischbacher
Page: 73-84

Abstract: If cooperative dispositions are associated with unique phenotypic features ('green beards'), cooperative individuals can be identi ed. Therefore, cooperative individuals can avoid exploitation by defectors by cooperating exclusively with other cooperative individuals; consequently, cooperators ourish and defectors die out. Experimental evidence suggests that subjects, who are given the opportunity to make promises in face-to-face interactions, are indeed able to predict the partner's behavior better than chance in a subsequent Prisoners' Dilemma. This evidence has been interpreted as evidence in favor of green beard approaches to the evolution of human cooperation. Here we argue, however, that the evidence does not support this interpretation. We show, in particular, that the existence of conditional cooperation renders subjects' choices in the Prisoners' Dilemma predictable. However, although subjects predict behavior better than chance, sel sh individuals earn higher incomes than conditional cooperators. Thus, although subjects may predict other players' choices better than chance evolution favors the sel sh subjects, i.e., the experimental evidence does not support the green beard approach towards the evolution of cooperation.

Title: Altruists with Green Beards: Still Kicking?
Author: Robert H. Frank
Page: 85-96

Abstract: In earlier work, I proposed the 'adaptive standard of rationality', according to which narrow self-interest models can be broadened by positing additional tastes, but only upon a plausible showing that those tastes do not hamper resource acquisition in competitive environments. This proposal is related to the green beard hypothesis from biology, according to which altruism might be adaptive if its presence could be reliably signaled by some observable feature, such as a green beard. In their contri- bution to this issue Ernst Fehr and Urs Fischbacher o er theoretical arguments and describe laboratory experiments whose results they interpret as refuting my version of the green beard hypothesis. In this response, I argue that their theoretical arguments and experimental evidence pose no threat to the green beard hypothesis.

Title: Strong Reciprocity and the Comparative Method
Author: Christopher Stephens
Page: 97-105

Abstract: Ernst Fehr and his collaborators have argued that traditional explanations of human cooperation cannot account for strong reciprocity. They provide substantial empirical evidence that strong reciprocity is an important phenomenon that cannot be explained by the traditional models of kin selection or reciprocal altruism. In this note, however, I argue that it will be di cult to test speci c adaptive explanations of strong reciprocity because it is apparently unique to humans. Consequently, it is di cult to employ the comparative method, which is one of biology's best tools for testing adaptationist claims.

Title: The Evolutionary Foundations of Strong Reciprocity
Author: Jason McKenzie Alexander
Page: 106-112

Abstract: Strong reciprocators possess two behavioural dispositions: they are willing to bestow bene ts on those who have bestowed bene ts, and they are willing to punish those who fail to bestow bene ts according to some social norm. There is no doubt that peoples' behaviour, in many cases, agrees with what we would expect if people are strong reciprocators, and Fehr and Henrich argue that many people are, in fact, strong reciprocators. They also suggest that strongly reciprocal behaviour may be brought about by specialised cognitive architecture produced by evolution. I argue that specialised cognitive architecture can play a role in the production of strongly reciprocal behaviour only in a very attenuated sense, and that the evolutionary foundations of strong reciprocity are more likely cultural than biological.

Title: The Biological and Evolutionary Logic of Human Cooperation
Author: Terence C. Burnham / Dominic D. P. Johnson
Page: 113-135

Abstract: Human cooperation is held to be an evolutionary puzzle because people voluntarily engage in costly cooperation, and costly punishment of non-cooperators, even among anonymous strangers they will never meet again. The costs of such cooperation cannot be recovered through kin-selection, reciprocal altruism, indirect reciprocity, or costly signaling. A number of recent authors label this behavior "strong reciprocity", and argue that it is: (a) a newly documented aspect of human nature, (b) adaptive, and (c) evolved by group selection. We argue exactly the opposite; that the phenomenon is: (a) not new, (b) maladaptive, and (c) evolved by individual selection. In our perspective, the apparent puzzle disappears to reveal a biological and evolutionary logic to human cooperation. Group selection may play a role in theory, but it is neither necessary nor sufficient to explain human cooperation. Our alternative solution is simpler, makes fewer assumptions, and is more parsimonious with the empirical data.

Title: On the Original Contract: Evolutionary Game Theory and Human Evolution
Author: Alex Rosenberg / Stefan Linquist
Page: 136-157

Abstract: This paper considers whether the available evidence from archeology, biological anthropology, primatology, and comparative gene-sequencing, can test evolutionary game theory models of cooperation as historical hypotheses about the actual course of human prehistory. The examination proceeds on the assumption that cooperation is the product of cultural selection and is not a genetically encoded trait. Nevertheless, we conclude that gene sequence data may yet shed signi cant light on the evolution of cooperation.

Title: Social Relations Instead of Altruistic Punishment
Author: Anton Leist
Page: 158-171

Abstract: Ernst Fehr's experimental research on altruistic behaviour aims at superseding the classical homo oeconomicus in micro-economic behaviour theory. This essay discusses Fehr's results from two points of view: rst, in regard to the understanding of social action associated with the term "altruism"; second, in regard to the 'anthropological' strategy of research that is based on the laboratory method. Against the emphasis on altruism it will be argued that it misleads into providing a distorted description of social acting, and that, due to insu cient clarity about motives for acting, Fehr's empirical results give evidence not of altruism but rather of phenomena of social recognition. The objection against the anthropological strategy will be that it makes visible only local phenomena within prevailing social conditions and that it thus assumes more than it explains.

Title: 'Nostrism': Social Identities in Experimental Games
Author: Hans Bernhard Schmid
Page: 172-187

Abstract: In this paper it is argued that a) altruism is an inadequate label for human cooperative behavior, and b) an adequate account of cooperation has to depart from the standard economic model of human behavior by taking note of the agents' capacity to see themselves and act as team-members. Contrary to what Fehr et al. seem to think, the main problem of the conceptual limitations of the standard model is not so much the assumption of sel shness but rather the atomistic conception of the individual. A much-neglected question of the theory of cooperation is how the agent's social identity is determined, i.e. how individuals come to think of themselves and act as members of a group. Considering as an example one of Fehr et al.'s third party punishment experiments, I shall argue that the agents' identities (and thus the result of the experiment) are strongly in uenced by the way the experiment is presented to the participants, especially by the collectivity-related vocabulary used in the instructions.

Title: Altruism and the Indispensability of Motives
Author: Mark S. Peacock / Michael Schefczyk / Peter Schaber
Page: 188-196

Abstract: In this paper we examine Fehr's notions of "altruism", "strong reciprocity" and "altruistic punishment" and query his ascription of altruism. We suggest that, pace Fehr, altruism cannot be de ned behaviourally because the de nition of altruism must refer to the motives of actors. We also advert to certain inconsistencies in Fehr's usage of his terms and we question his explanation of altruism in terms of 'social preferences'.

Title: Fehr on Altruism, Emotion, and Norms
Author: Jon Elster
Page: 197-211

Abstract: I discuss recent work by Ernst Fehr and his collaborators on cooperation and reciprocity. (i) Their work demonstrates conclusively the reality and importance of non-self-interested motivations. (ii) It allows for a useful distinction between trust and blind trust. (iii) It points to a category of quasi-moral norms, distinct both from social norms and moral norms. (iv) It demonstrates how social interactions can generate irrational belief formation. (v) It shows the potential of punishment for sustaining social norms and for overcoming the second-order free rider problem as well as obstacles to group selection. (vi) It o ers a provocative experimental basis for the `warm-glow' explanation of altruistic behavior. I conclude by suggesting some experiments that might allow for further developments of the theory.