Robustness analysis is widespread in science, but philosophers have struggled to justify its confirmatory power. We provide a positive account of robustness by analysing some explicit and implicit uses of within and across-model robustness in evolutionary theory. We argue that appeals to robustness are usually difficult to justify because they aim to increase the likeliness that a phenomenon obtains. However, we show that robust results are necessary for explanations of phenomena with specific properties. Across-model robustness is necessary for how-possibly explanations (...) of multiply instantiated phenomena, while within-model robustness is necessary for explanations of phenomena with multiple evolutionary starting points. In such cases, the appeal of robustness is explanatory rather than confirmatory. (shrink)

In this article I develop a big picture of the evolution of human cooperation, and contrast it to an alternative based on group selection. The crucial claim is that hominin history has seen two major transitions in cooperation, and hence poses two deep puzzles about the origins and stability of cooperation. The first is the transition from great ape social lives to the lives of Pleistocene cooperative foragers; the second is the stability of the social contract through the early Holocene (...) transition to complex hierarchical societies. The first of these transitions is driven, at least initially, by individual advantage: cooperation paid off for individual foragers, initially through mutualist interaction, then through reciprocation. This argument leads to a reanalysis of the role of violence and the nature of the freeriding threat to cooperation. But the conditions that select for cooperative individuals in the Pleistocene were eroded in the Pleistocene–Holocene transition. So we need an alternative account of the survival, and indeed the expansion, of cooperation in the Holocene. Group selection driven by intercommunal conflict really may well be central to this second transition. (shrink)

Existing economic models of prosociality have been rather silent in terms of proximate psychological mechanisms. We nevertheless identify the psychologically most informed accounts and offer a critical discussion of their hypotheses for the proximate psychological explanations. Based on convergent evidence from several fields of research, we argue that there nevertheless is a more plausible alternative proximate account available: the social motivation hypothesis. The hypothesis represents a more basic explanation of the appeal of prosocial behavior, which is in terms of anticipated (...) social rewards. We also argue in favor of our own social motivation hypothesis over Robert Sugden’s fellow-feeling account (due originally to Adam Smith). We suggest that social motivation not only stands as a proximate account in its own right but also provides a plausible scaffold for other more sophisticated motivations (e.g., fellow-feelings). We conclude by discussing some possible implications of the social motivation hypothesis on existing modeling practice. (shrink)

Coalitions and alliances are core aspects of human behavior. All societies recognize alliances among communities, usually based in part on kinship and marriage. Aggression between groups is ubiquitous, often deadly, fueled by revenge, and can have devastating effects on general human welfare. Given its significance, it is surprising how little we know about the neurobiological and hormonal mechanisms that underpin human coalitionary behavior. Here we first briefly review a model of human coalitionary behavior based on a process of runaway social (...) selection. We then present several exploratory analyses of neuroendocrine responses to coalitionary social events in a rural Dominican community, with the objective of understanding differences between in-group and out-group competition in adult and adolescent males. Our analyses indicate: (1) adult and adolescent males do not elevate testosterone when they defeat their friends, but they do elevate testosterone when they defeat outsiders; (2) pre-competition testosterone and cortisol levels are negatively associated with strength of coalitionary ties; and (3) adult males usually elevate testosterone when interacting with adult women who are potential mates, but in a striking reversal, they have lower testosterone if the woman is a conjugal partner of a close friend. These naturalistic studies hint that reciprocity, dampening of aggression, and competition among friends and allies may be biologically embedded in unique ways among humans. (shrink)

Economists and biologists have proposed a distinction between two mechanisms – “strong” and “weak” reciprocity – that may explain the evolution of human sociality. Weak reciprocity theorists emphasize the benefits of long-term cooperation and the use of low-cost strategies to deter free-riders. Strong reciprocity theorists, in contrast, claim that cooperation in social dilemma games can be sustained by costly punishment mechanisms, even in one-shot and finitely repeated games. To support this claim, they have generated a large body of evidence concerning (...) the willingness of experimental subjects to punish uncooperative free-riders at a cost to themselves. In this article, I distinguish between a “narrow” and a “wide” reading of the experimental evidence. Under the narrow reading, punishment experiments are just useful devices to measure psychological propensities in controlled laboratory conditions. Under the wide reading, they replicate a mechanism that supports cooperation also in “real-world” situations outside the laboratory. I argue that the wide interpretation must be tested using a combination of laboratory data and evidence about cooperation “in the wild.” In spite of some often-repeated claims, there is no evidence that cooperation in the small egalitarian societies studied by anthropologists is enforced by means of costly punishment. Moreover, studies by economic and social historians show that social dilemmas in the wild are typically solved by institutions that coordinate punishment, reduce its cost, and extend the horizon of cooperation. The lack of field evidence for costly punishment suggests important constraints about what forms of cooperation can or cannot be sustained by means of decentralised policing. (shrink)

Helen Frowe has recently offered what she calls a “practical” account of self-defense. Her account is supposed to be practical by being subjectivist about permissibility and objectivist about liability. I shall argue here that Frowe first makes up a problem that does not exist and then fails to solve it. To wit, her claim that objectivist accounts of permissibility cannot be action-guiding is wrong; and her own account of permissibility actually retains an objectivist (in the relevant sense) element. In addition, (...) her attempt to restrict subjectivism primarily to “urgent” situations like self-defense contradicts her own point of departure and is either incoherent or futile. Finally, the only actual whole-heartedly objectivist account she criticizes is an easy target; while those objectivist accounts one finds in certain Western European jurisdictions are immune to her criticisms. Those accounts are also clearly superior to hers in terms of action-guidingness. (shrink)

Altruism is a deep and complex phenomenon that is analysed by scholars of various disciplines, including psychology, philosophy, biology, evolutionary anthropology and experimental economics. Much confusion arises in current literature because the term altruism covers variable concepts and processes across disciplines. Here we investigate the sense given to altruism when used in different fields and argumentative contexts. We argue that four distinct but related concepts need to be distinguished: (a) psychological altruism , the genuine motivation to improve others’ interests and (...) welfare; (b) reproductive altruism , which involves increasing others’ chances of survival and reproduction at the actor’s expense; (c) behavioural altruism , which involves bearing some cost in the interest of others; and (d) preference altruism , which is a preference for others’ interests. We show how this conceptual clarification permits the identification of overstated claims that stem from an imprecise use of terminology. Distinguishing these four types of altruism will help to solve rhetorical conflicts that currently undermine the interdisciplinary debate about human altruism. (shrink)

It is central to standard economic theory that people act on their interests. People are interested in a variety of things, so a range of values should influence market behavior. When engaged in commerce, however, people generally act for personal gain; the influence of other values usually just disappears in the marketplace. What is missing from the standard account is that people often act on proper subsets of their interests. Economics can, however, be extended to capture this insight. Key Words: (...) economic theory • attention • self-interest • social responsibility • discrimination. (shrink)

The origin of human cooperation poses an evolutionary puzzle. In order for cooperation to evolve, our Pleistocene ancestors must have overcome the free rider problem, in which noncooperators reap the benefits of cooperation without paying the costs. Cultural group selection accounts offer a potential solution to this problem. In this article, I evaluate Boyd and Richerson’s influential account. I argue that it cannot explain the evolutionary origins of human cooperation because it presupposes cooperative behaviors among our Pleistocene ancestors. Although Boyd (...) and Richerson’s account may explain the expansion of cooperation in hominin evolution, it cannot explain how cooperative behaviors first emerged. (shrink)

If you are kind to me, I am likely to reciprocate and doing so feels fair. Many theories of social exchange assume that such reciprocity and fairness are well aligned with one another. We argue that this correspondence between reciprocity and fairness is restricted to interpersonal dyads and does not govern more complex multilateral interactions. When multiple people are involved, reciprocity leads to partiality, which may be seen as unfair by outsiders. We report seven studies, conducted with people from the (...) United States, in which participants were asked to evaluate situations involving resource distribution in contexts such as economic games, government, and the workplace. Specifically, we find that equal resource distribution in multilateral interactions is seen as more fair than engaging in reciprocity. We also find that negative reciprocity is seen as more fair than positive reciprocity in these multilateral situations because positive reciprocity is perceived as based in favoritism. We rule out alternative explanations and demonstrate that there are contexts where favoritism is not viewed as unfair. These findings are important for theories of fairness and reciprocity as they demonstrate the central role of perceived partiality in the evaluation of multi‐party resource allocation. (shrink)

I explore the evolution of strategies in an Augmented Stag Hunt game that adds a punishing strategy to the ordinary Stag Hunt strategies of cooperating, which aims for optimality, and defecting, which “plays it safe.” Cooperating weakly dominates punishing and defecting is the unique evolutionarily stable strategy. Nevertheless, for a wide class of Augmented Stag Hunts, polymorphic strategies combining punishing and cooperating collectively have greater attracting power for replicator dynamics than that of the ESS. The analysis here lends theoretical support (...) to the altruistic punishment hypothesis in the social sciences. (shrink)

Economists and biologists have proposed a distinction between two mechanisms – “strong” and “weak” reciprocity – that may explain the evolution of human sociality. Weak reciprocity theorists emphasize the benefits of long-term cooperation and the use of low-cost strategies to deter free-riders. Strong reciprocity theorists, in contrast, claim that cooperation in social dilemma games can be sustained by costly punishment mechanisms, even in one-shot and finitely repeated games. To support this claim, they have generated a large body of evidence concerning (...) the willingness of experimental subjects to punish uncooperative free-riders at a cost to themselves. In this article, I distinguish between a “narrow” and a “wide” reading of the experimental evidence. Under the narrow reading, punishment experiments are just useful devices to measure psychological propensities in controlled laboratory conditions. Under the wide reading, they replicate a mechanism that supports cooperation also in “real-world” situations outside the laboratory. I argue that the wide interpretation must be tested using a combination of laboratory data and evidence about cooperation “in the wild.” In spite of some often-repeated claims, there is no evidence that cooperation in the small egalitarian societies studied by anthropologists is enforced by means of costly punishment. Moreover, studies by economic and social historians show that social dilemmas in the wild are typically solved by institutions that coordinate punishment, reduce its cost, and extend the horizon of cooperation. The lack of field evidence for costly punishment suggests important constraints about what forms of cooperation can or cannot be sustained by means of decentralised policing. (shrink)

Experimental studies on punishment have sometimes been over-interpreted not only for the reasons Guala lists, but also because of a frequent conflation of proximate and ultimate explanatory levels that Guala's review perpetuates. Moreover, for future analyses we may need a clearer classification of different kinds of punishment.

The standard theories of cooperation in humans, which depend on repeated interaction and reputation effects among self-regarding agents, are inadequate. Strong reciprocity, a predisposition to participate in costly cooperation and the punishment, fosters cooperation where self-regarding behaviors fail. The effectiveness of socially coordinated punishment depends on individual motivations to participate, which are based on strong reciprocity motives. The relative infrequency of high-cost punishment is a result of the ubiquity of strong reciprocity, not its absence.

Recent years have witnessed an increased number of game-theoretic approaches to social norms, which apparently share some common vocabulary and methods. We describe three major approaches of this kind (due to Binmore, Bicchieri and Gintis), before comparing them systematically on five crucial themes: generality of the solution, preference transformation, punishment, epistemic conditions and type of explanation. This allows us to show that these theories are, by and large, less compatible than they seem. We then argue that those three theories struggle (...) to account for three phenomena pertaining to social norms (namely context-dependence, conflicting norms and self-evidence), with which any complete game-theoretic account should in principle be able to deal. (shrink)

The disagreement between Binmore and the “behaviouralists” concerns mainly the kind of reciprocity mechanisms that sustain cooperation in and out of the experimental laboratory. Although Binmore’s scepticism concerning Strong Reciprocity is justified, his case for Weak Reciprocity and the long-run convergence to Nash equilibria is unsupported by laboratory evidence. Part of the reason is that laboratory evidence alone cannot solve the reciprocity controversy, and researchers should pay more attention to field data. As an example, I briefly illustrate a historical case (...) suggesting that the institutions that foster cooperation in the real world rely on Weak Reciprocity mechanisms such as those that feature prominently in Binmore’s story. (shrink)

Preface to a special section on "Cooperation in nature, science, and society".

Paul Seabright is the first to clearly identify a major puzzle about human social evolution: the expansion of cooperation in the more complex societies of the Holocene. Identifying that problem is a major achievement, but in this paper I give a somewhat different account of the nature of the problem and a somewhat different account of the social world of Pleistocene foragers. So, we agree that there is a problem, but not on its nature or solution.

Many studies show that punishment, although able to stabilize cooperation at high levels, destroys gains which makes it less efficient than alternatives with no punishment. Standard public goods games (PGGs) in fact show exactly these patterns. However, both evolutionary theory and real world institutions give reason to expect institutions with punishment to be more efficient, particularly in the long run. Long-term cooperative partnerships with punishment threats for non-cooperation should outperform defection prone non-punishing ones. This article demonstrates that fieldwork data from (...) hunter-gatherers, common pool resource management cases and even PGGs support this hypothesis. Although earnings in PGGs with a punishment option may be lower at the beginning, efficiency increases dramatically over time. Most ten-period PGGs cannot capture this change because their time horizon is too short. (shrink)