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The article focuses on a commentary by Pat Barclay and Sandeep Mishra discussing a recent paper by de Courson et al. The paper explores the psychology of relative state and violence, offering insights into the incentives for violence in society based on agent-based fitness modeling. It summarizes the model's findings, reviews the evidence linking the psychology of relative state to deprivation and speculates on the policy implications of the model for addressing violence and inequality.

People vary both in their embrace of their society's traditions, and in their perception of hazards as salient and necessitating a response. Over evolutionary time, traditions have offered avenues for addressing hazards, plausibly resulting in linkages between orientations toward tradition and orientations toward danger. Emerging research documents connections between traditionalism and threat responsivity, including pathogen-avoidance motivations. Additionally, because hazard-mitigating behaviors can conflict with competing priorities, associations between traditionalism and pathogen avoidance may hinge on contextually contingent tradeoffs. The COVID-19 pandemic provides a real-world test of the posited relationship between traditionalism and hazard avoidance. Across 27 societies (N = 7844), we find that, in a majority of countries, individuals' endorsement of tradition positively correlates with their adherence to costly COVID-19-avoidance behaviors; accounting for some of the conflicts that arise between public health precautions and other objectives further strengthens this evidence that traditionalism is associated with greater attention to hazards. [ABSTRACT FROM AUTHOR]

Previous work has reported a relation between pathogen-avoidance motivations and prejudice toward various social groups, including gay men and lesbian women. It is currently unknown whether this association is present across cultures, or specific to North America. Analyses of survey data from adult heterosexuals (N = 11,200) from 31 countries showed a small relation between pathogen disgust sensitivity (an individual-difference measure of pathogen-avoidance motivations) and measures of antigay attitudes. Analyses also showed that pathogen disgust sensitivity relates not only to antipathy toward gay men and lesbians, but also to negativity toward other groups, in particular those associated with violations of traditional sexual norms (e.g., prostitutes). These results suggest that the association between pathogen-avoidance motivations and antigay attitudes is relatively stable across cultures and is a manifestation of a more general relation between pathogen-avoidance motivations and prejudice towards groups associated with sexual norm violations. [ABSTRACT FROM AUTHOR]

The "fearful ape hypothesis" is interesting but is currently underspecified. We need more research on whether it is specific to fear, specific to humans (or even cooperative breeders in general), what is included in "fear," and whether these patterns would indeed evolve despite arms races to extract help from audiences. Specifying these will result in a more testable hypothesis. [ABSTRACT FROM AUTHOR]

Third-party punishment is thought to act as an honest signal of cooperative intent and such signals might escalate when competing to be chosen as a partner. Here, we investigate whether partner choice competition prompts escalating investment in third-party punishment. We also consider the case of signalling via helpful acts to provide a direct test of the relative strength of the two types of signals. Individuals invested more in third-party helping than third-party punishment and invested more in both signals when observed compared to when investments would be unseen. We found no clear effect of partner choice (over and above mere observation) on investments in either punishment or helping. Third-parties who invested more than a partner were preferentially chosen for a subsequent Trust Game although the preference to interact with the higher investor was more pronounced in the help than in the punishment condition. Third-parties who invested more were entrusted with more money and investments in third-party punishment or helping reliably signalled trustworthiness. Individuals who did not invest in third-party helping were more likely to be untrustworthy than those who did not invest in third-party punishment. This supports the conception of punishment as a more ambiguous signal of cooperative intent compared to help. [ABSTRACT FROM AUTHOR]

Gossip, or sharing information about absent others, has been identified as an effective solution to free rider problems in situations with conflicting interests. Yet, the information transmitted via gossip can be biased, because gossipers may send dishonest information about others for personal gains. Such dishonest gossip makes reputation-based cooperation more difficult to evolve. But when are people likely to share honest or dishonest gossip? We build formal models to provide the theoretical foundation for individuals' gossip strategies, taking into account the gossiper's fitness interdependence with the receiver and the target. Our models across four different games suggest a very simple rule: when there is a perfect match (mismatch) between fitness interdependence and the effect of honest gossip, the gossiper should always be honest (dishonest); however, in the case of a partial match, the gossiper should make a choice based on their fitness interdependence with the receiver and the target and the marginal cost/benefit in terms of pay-off differences caused by possible choices of the receiver and the target in the game. Moreover, gossipers can use this simple rule to make optimal decisions even under noise. We discuss empirical examples that support the predictions of our model and potential extensions. This article is part of the theme issue 'The language of cooperation: reputation and honest signalling'. [ABSTRACT FROM AUTHOR]

Social organisms often need to know how much to trust others to cooperate. Organisms can expect cooperation from another organism that depends on them (i.e. stake or fitness interdependence), but how do individuals assess fitness interdependence? Here, we extend fitness interdependence into a signalling context: costly helping behaviour can honestly signal one's stake in others, such that those who help are trusted more. We present a mathematical model in which agents help others based on their stake in the recipient's welfare, and recipients use that information to assess whom to trust. At equilibrium, helping is a costly signal of stake: helping is worthwhile for those who value the recipient (and thus will repay any trust), but is not worthwhile for those who do not value the recipient (and thus will betray the trust). Recipients demand signals when they value the signallers less and when the cost of betrayed trust is higher; signal costs are higher when signallers have more incentive to defect. Signalling systems are more likely when the trust games resemble Prisoner's Dilemmas, Stag Hunts or Harmony Games, and are less likely in Snowdrift Games. Furthermore, we find that honest signals need not benefit recipients and can even occur between hostile parties. By signalling their interdependence, organisms benefit from increased trust, even when no future interactions will occur. This article is part of the theme issue 'The language of cooperation: reputation and honest signalling'. [ABSTRACT FROM AUTHOR]

When one individual helps another, it benefits the recipient and may also gain a reputation for being cooperative. This may induce others to favour the helper in subsequent interactions, so investing in being seen to help others may be adaptive. The best-known mechanism for this is indirect reciprocity (IR), in which the profit comes from an observer who pays a cost to benefit the original helper. IR has attracted considerable theoretical and empirical interest, but it is not the only way in which cooperative reputations can bring benefits. Signalling theory proposes that paying a cost to benefit others is a strategic investment which benefits the signaller through changing receiver behaviour, in particular by being more likely to choose the signaller as a partner. This reputation-based partner choice can result in competitive helping whereby those who help are favoured as partners. These theories have been confused in the literature. We therefore set out the assumptions, the mechanisms and the predictions of each theory for how developing a cooperative reputation can be adaptive. The benefits of being seen to be cooperative may have been a major driver of sociality, especially in humans. This article is part of the theme issue 'The language of cooperation: reputation and honest signalling'. [ABSTRACT FROM AUTHOR]

Humans care about having a positive reputation, which may prompt them to help in scenarios where the return benefits are not obvious. Various game-theoretical models support the hypothesis that concern for reputation may stabilize cooperation beyond kin, pairs or small groups. However, such models are not explicit about the underlying psychological mechanisms that support reputation-based cooperation. These models therefore cannot account for the apparent rarity of reputation-based cooperation in other species. Here, we identify the cognitive mechanisms that may support reputation-based cooperation in the absence of language. We argue that a large working memory enhances the ability to delay gratification, to understand others' mental states (which allows for perspective-taking and attribution of intentions) and to create and follow norms, which are key building blocks for increasingly complex reputation-based cooperation. We review the existing evidence for the appearance of these processes during human ontogeny as well as their presence in non-human apes and other vertebrates. Based on this review, we predict that most non-human species are cognitively constrained to show only simple forms of reputation-based cooperation. This article is part of the theme issue 'The language of cooperation: reputation and honest signalling'. [ABSTRACT FROM AUTHOR]

Some evidence suggests that people behave more cooperatively and generously when observed or in the presence of images of eyes (termed the 'watching eyes' effect). Eye images are thought to trigger feelings of observation, which in turn motivate people to behave more cooperatively to earn a good reputation. However, several recent studies have failed to find evidence of the eyes effect. One possibility is that inconsistent evidence in support of the eyes effect is a product of individual differences in sensitivity or susceptibility to the cue. In fact, some evidence suggests that people who are generally more prosocial are less susceptible to situation-specific reputation-based cues of observation. In this paper, we sought to (1) replicate the eyes effect, (2) replicate the past finding that people who are dispositionally less prosocial are more responsive to observation than people who are more dispositionally more prosocial, and (3) determine if this effect extends to the watching eyes effect. Results from a pre-registered study showed that people did not give more money in a dictator game when decisions were made public or in the presence of eye images, even though participants felt more observed when decisions were public. That is, we failed to replicate the eyes effect and observation effect. An initial, but underpowered, interaction model suggests that egoists give less than prosocials in private, but not public, conditions. This suggests a direction for future research investigating if and how individual differences in prosociality influence observation effects. [ABSTRACT FROM AUTHOR]

Objective: Stratified groups face at least two obstacles in solving collective action problems and producing public goods. Individuals face temptation to free ride, and high‐ranking group members face incentives to protect their position at the group's expense. We introduce democratic competition for rank as a solution to the problem of cooperation in groups. We argue that democratic competition for high rank creates incentives for cooperation that are absent in nondemocratic groups. Methods: In a small‐group behavioral experiment, we contrast groups in which individuals compete for a valuable high‐ranking position through democratic elections with groups in which individuals compete for high rank in resource‐based competitions. Groups faceda fluctuating external threat, and group members could invest resources in manipulating the apparent (but not actual) level of this threat. Results: We find that democratic groups reward high contributors by electing them to the high‐ranking position at greater rates than low contributors. We also find evidence that individuals in democratic groups contribute more to the public good than individuals in nondemocratic groups. However, high‐ranking individuals in democratic groups exaggerate threats to the group at similar rates to high‐ranking individuals in nondemocratic groups. Conclusion: The findings suggest that democratic competition increases public goods production and overall group efficiency, but does not eliminate—and may exacerbate—individuals' tendency to deceive their peers [ABSTRACT FROM AUTHOR]

Why do we care so much for friends, even making sacrifices for them they cannot repay or never know about? When organisms engage in reciprocity, they have a stake in their partner's survival and wellbeing so the reciprocal relationship can persist. This stake (aka fitness interdependence) makes organisms willing to help beyond the existing reciprocal arrangement (e.g. anonymously). I demonstrate this with two mathematical models in which organisms play a prisoner's dilemma, and where helping keeps their partner alive and well. Both models shows that reciprocity creates a stake in partners' welfare: those who help a cooperative partner––even when anonymous––do better than those who do not, because they keep that cooperative partner in good enough condition to continue the reciprocal relationship. ‘Machiavellian' cooperators, who defect when anonymous, do worse because their partners become incapacitated. This work highlights the fact that reciprocity and stake are not separate evolutionary processes, but are inherently linked. [ABSTRACT FROM AUTHOR]

Delay discounting is a measure of preferences for smaller immediate rewards over larger delayed rewards. Discounting has been assessed in many ways; these methods have variably and inconsistently involved measures of different lengths (single vs. multiple items), forced‐choice methods, self‐report methods, online and laboratory assessments, monetary and non‐monetary compensation. The majority of these studies have been conducted in laboratory settings. However, over the past 20 years, behavioral data collection has increasingly shifted online. Usually, these experiments involve completing short tasks for small amounts of money, and are thus qualitatively different than experiments in the lab, which are typically more involved and in a strongly controlled environment. The present study aimed to determine how to best measure future discounting in a crowdsourced sample using three discounting measures (a single shot measure, the 27‐item Kirby Monetary Choice Questionnaire, and a one‐time Matching Task). We examined associations of these measures with theoretically related variables, and assessed influence of payment on responding. Results indicated that correlations between the discounting tasks and conceptually related measures were smaller than in prior laboratory experiments. Moreover, our results suggest providing monetary compensation may attenuate correlations between discounting measures and related variables. These findings suggest that incentivizing discounting measures changes the nature of measurement in these tasks. [ABSTRACT FROM AUTHOR]

Speech contains both explicit social information in semantic content and implicit cues to social behaviour and mate quality in voice pitch. Voice pitch has been demonstrated to have pervasive effects on social perceptions, but few studies have examined these perceptions in the context of meaningful speech. Here, we examined whether male voice pitch interacted with socially relevant cues in speech to influence listeners’ perceptions of trustworthiness and attractiveness. We artificially manipulated men's voices to be higher and lower in pitch when speaking words that were either prosocial or antisocial in nature. In Study 1, we found that listeners perceived lower‐pitched voices as more trustworthy and attractive in the context of prosocial words than in the context of antisocial words. In Study 2, we found evidence that suggests this effect was driven by stronger preferences for higher‐pitched voices in the context of antisocial cues, as voice pitch preferences were not significantly different in the context of prosocial cues. These findings suggest that higher male voice pitch may ameliorate the negative effects of antisocial speech content and that listeners may be particularly avoidant of those who express multiple cues to antisociality across modalities. [ABSTRACT FROM AUTHOR]

Who takes risks, and when? The relative state model proposes two nonindependent selection pressures governing risk-taking: need-based and ability-based. The need-based account suggests that actors take risks when they cannot reach target states with low-risk options (consistent with risksensitivity theory). The ability-based account suggests that actors engage in risk-taking when they possess traits or abilities that increase the expected value of risk-taking (by increasing the probability of success, enhancing payoffs for success or buffering against failure). Adaptive risk-taking involves integrating both considerations. Risk-takers compute the expected value of risk-taking based on their state--the interaction of embodied capital relative to one's situation, to the same individual in other circumstances or to other individuals. We provide mathematical support for this dual pathway model, and show that it can predict who will take the most risks and when (e.g. when risk-taking will be performed by those in good, poor, intermediate or extreme state only). Results confirm and elaborate on the initial verbal model of state-dependent risk-taking: selection favours agents who calibrate risk-taking based on implicit computations of condition and/or competitive (dis)advantage, which in turn drives patterned individual differences in risk-taking behaviour. [ABSTRACT FROM AUTHOR]

Who takes risks, and why? Does risk-taking in one context predict risk-taking in other contexts? We seek to address these questions by considering two non-independent pathways to risk: need-based and ability-based. The need-based pathway suggests that risk-taking is a product of competitive disadvantage consistent with risk-sensitivity theory. The ability-based pathway suggests that people engage in risk-taking when they possess abilities or traits that increase the probability of successful risk-taking, the expected value of the risky behavior itself, and/or have signaling value. We provide a conceptual model of decision-making under risk—the relative state model—that integrates both pathways and explicates how situational and embodied factors influence the estimated costs and benefits of risk-taking in different contexts. This model may help to reconcile long-standing disagreements and issues regarding the etiology of risk-taking, such as the domain-generality versus domain-specificity of risk or differential engagement in antisocial and non-antisocial risk-taking. [ABSTRACT FROM AUTHOR]

In order for non-kin altruism to evolve, altruists must receive fitness benefits for their actions that outweigh the costs. Several researchers have suggested that altruism is a costly signal of desirable qualities, such that it could have evolved by sexual selection. In two studies, we show that altruism is broadly linked with mating success. In Study 1, participants who scored higher on a self-report altruism measure reported they were more desirable to the opposite sex, as well as reported having more sex partners, more casual sex partners, and having sex more often within relationships. Sex moderated some of these relationships, such that altruism mattered more for men's number of lifetime and casual sex partners. In Study 2, participants who were willing to donate potential monetary winnings (in a modified dictator dilemma) reported having more lifetime sex partners, more casual sex partners, and more sex partners over the past year. Men who were willing to donate also reported having more lifetime dating partners. Furthermore, these patterns persisted, even when controlling for narcissism, Big Five personality traits, and socially desirable responding. These results suggest that altruists have higher mating success than non-altruists and support the hypothesis that altruism is a sexually selected costly signal of difficult-to-observe qualities. [ABSTRACT FROM AUTHOR]

Social pain is often associated with social rejection and shares neural correlates with the bothersome aspect of physical pain, which may also indicate an overlap in function. Pain has been described as a motivational signal to respond to the source of the pain in an adaptive way, such as by altering behavior. We tested whether social pain causes similarly adaptive alterations in behavior. Participants played computerized ball-tossing tasks with putative players-one who passed to and one who excluded the participant from play-in both a social and nonsocial version. We assessed the behavioral consequences of social pain by comparing the number of throws to each stimulus (social rejector vs. nonsocial rejector) over the course of the task. Posttask questionnaires assessed subjective feelings of social pain. A decrease in throws to the rejecting stimulus was only observed in the social version, indicating that rejection that is social in nature leads to change in behavior. Moreover, participants reported more negative feelings toward the rejecting stimulus in the social than in the nonsocial version. These subjective feelings of social pain mediated the effect of version of the game (social vs. nonsocial) on changes in behavior, indicating that social pain from social rejection causes changes in behavior. [ABSTRACT FROM AUTHOR]

People who are more avoidant of pathogens are more politically conservative, as are nations with greater parasite stress. In the current research, we test two prominent hypotheses that have been proposed as explanations for these relationships. The first, which is an intragroup account, holds that these relationships between pathogens and politics are based on motivations to adhere to local norms, which are sometimes shaped by cultural evolution to have pathogenneutralizing properties. The second, which is an intergroup account, holds that these same relationships are based on motivations to avoid contact with outgroups, who might pose greater infectious disease threats than ingroup members. Results from a study surveying 11,501 participants across 30 nations are more consistent with the intragroup account than with the intergroup account. National parasite stress relates to traditionalism (an aspect of conservatism especially related to adherence to group norms) but not to social dominance orientation (SDO; an aspect of conservatism especially related to endorsements of intergroup barriers and negativity toward ethnic and racial outgroups). Further, individual differences in pathogen-avoidance motives (i.e., disgust sensitivity) relate more strongly to traditionalism than to SDO within the 30 nations. [ABSTRACT FROM AUTHOR]

People perform greater within-group cooperation when their groups face external threats, such as hostile outgroups or natural disasters. Researchers and social commentators suggest that high-ranking group members manipulate this “threat-dependent” cooperation by exaggerating threats in order to promote cooperation and suppress competition for their position. However, little systematic research tests this claim or possible situational moderators. In three studies, we use a cooperative group game to show that participants pay to increase others’ perceptions of group threats, and spend more on manipulation when holding privileged positions. This manipulation cost-effectively elicits cooperation and sustains privilege, and is fostered by competition over position, not only position per se. Less cooperative people do more manipulation than more cooperative people do. Furthermore, these effects generalize to broader definitions of privilege. Conceptually, these results offer new insights into an understudied dimension of group behavior. Methodologically, the research extends cooperative group games to allow for analyzing more complex group dynamics. [ABSTRACT FROM AUTHOR]

Members of social groups face a trade-off between investing selfish effort for themselves and investing cooperative effort to produce a shared group resource. Many group resources are shared equitably: they may be intrinsically non-excludable public goods, such as vigilance against predators, or so large that there is little cost to sharing, such as cooperatively hunted big game. However, group members' personal resources, such as food hunted individually, may be monopolizable. In such cases, an individual may benefit by investing effort in taking others' personal resources, and in defending one's own resources against others. We use a game theoretic “tug-of-war” model to predict that when such competition over personal resources is possible, players will contribute more towards a group resource, and also obtain higher payoffs from doing so. We test and find support for these predictions in two laboratory economic games with humans, comparing people's investment decisions in games with and without the options to compete over personal resources or invest in a group resource. Our results help explain why people cooperatively contribute to group resources, suggest how a tragedy of the commons may be avoided, and highlight unifying features in the evolution of cooperation and competition in human and non-human societies. [ABSTRACT FROM AUTHOR]

Individuals of different quality often differ in their helping behavior, but sometimes it is the high-quality individuals who help most (e.g., human meat sharing, vigilance) and other times it is the low-quality individuals (e.g., reproductive queues, primate grooming). We argue that these differences depend on individual differences in the performance costs of actually helping, the opportunity costs from forsaking alternative activities, and the fitness benefits for engaging the help. If helping is more difficult for some individuals to do (quality-dependent help), it will usually be done by high-quality individuals, whereas help that all individuals could do equally well (quality-independent help) will be done by whoever pays lower opportunity costs. Our model makes novel predictions about many kinds of helping, allows us to categorize different types of helping by their relationship with individual quality, and is general enough to apply to many situations. Furthermore, it can be generalized to any other type of (nonhelping) behavior where there are individual differences in benefits, performance costs, or opportunity costs. [ABSTRACT FROM PUBLISHER]

Social organisms in many taxa cooperate to produce resources that are shared among group members. Some cooperatively produced resources may be monopolized by individuals who invest in within-group competition, but these have largely been overlooked in empirical and theoretical research on human cooperation, which has focused on noncontestable public goods. In this study, we allow for the potential of within-group competition over cooperatively produced resources and use a game theoretic “tug-of-war” model and empirical test to show that such competition decreases the degree of cooperation within human groups and hence decreases group members' payoffs. Our study thus sheds light on how cooperative production and equal division of shared resources may have evolved, expands on current models of human cooperation to reflect the many natural conditions with opportunities for within-group competition, and demonstrates unifying principles in cooperation and competition across the animal kingdom. [ABSTRACT FROM PUBLISHER]

Purpose – Increased use and changes in the way e-resources are delivered led some libraries to question the detail of some of the definitions used and particularly to suggest that statistics required by SCONUL did not always match the requirements or practice of the libraries themselves. The purpose of this paper is to explore a set of e-measures. Design/methodology/approach – A pilot project was set up to test a set of e-measures, sufficiently robust to give confidence in their use in a national/international context and in benchmarking individual libraries. A total of 20 SCONUL members made quarterly returns during 2009-10. During the year, categories and definitions were adjusted in the light of comments received. A workshop was held to exchange views and inform the decision on what went into the new return. Findings – It was clear from the start that practice varied, and compromise would be required. Foremost among the changes are: inclusion of e-resources held within databases in the count of titles; count of free titles or titles purchased in previous years; inclusion of database searches; separation of costs of different types of e-resource. Originality/value – The SCONUL statistics are a tool and servant of the members, helping libraries to run more effectively, and at the same time providing valuable evidence on UK academic libraries and their activities to the wider world. The new e-measures questions will provide a reliable picture of the use of e-resources across the sector and be useful to libraries individually or in benchmarking groups in assessing their own usage. [ABSTRACT FROM AUTHOR]

Public generosity may be a means to convincingly advertise one's good character. This hypothesis suggests that altruistic individuals will be desirable as romantic partners. Few studies have tested this prediction, and these showed mixed results. Some studies have found that altruism is not particularly attractive; other studies showed that altruism is attractive by contrasting descriptions of 'nice guys' with 'jerks'. The present study sought to resolve this debate by having participants read a series of experimentally manipulated vignettes of persons with corresponding photographs, such that altruistic vignettes were compared with control descriptions that differed only in the presence or absence of small hints of altruistic tendencies. Altruists were more desirable for long-term relationships than neutral individuals. Women also preferred altruists for single dates whereas men had no such preference. These results are discussed with regard to the idea that people (males in particular) signal their good character via generosity. [ABSTRACT FROM AUTHOR]

We extend Tomasello's framework by addressing the functional challenge of obligation. If the long-run social consequences of a decision are sufficiently costly, obligation motivates the actor to forgo potential immediate benefits in favor of long-term social interests. Thus, obligation psychology balances the downstream socially-mediated payoffs from a decision. This perspective can predict when and why obligation will be experienced. [ABSTRACT FROM AUTHOR]

The evolution of reciprocal altruism probably involved the evolution of mechanisms to detect cheating and remember cheaters. In a well-known study, Mealey, Daood, and Krage (1996) observed that participants had enhanced memory for faces that had previously been associated with descriptions of acts of cheating. There were, however, problems with the descriptions that were used in that study. We sought to replicate and extend the findings of Mealey and colleagues by using more controlled descriptions and by examining the possibility of enhanced altruist recognition. We also examined whether individual differences in cheating tendencies were related to cheater and altruist recognition. In the first experiment, 164 undergraduates saw 40 faces that were paired with character descriptions representing the categories of cheater, trustworthy, altruist, or neutral, for individuals who had either low or high social status. One week later participants reported which faces they recognized from the previous week (among 80 faces). Overall, the results failed to replicate the findings of Mealey and her colleagues, as there was no enhanced memory for cheaters. In addition, there was no enhanced memory for altruists, and no effect of participants' cheating tendencies. A second experiment using a slightly different methodology produced similar results, with some evidence for enhanced memory for altruists. [ABSTRACT FROM AUTHOR]

Physical attractiveness affects how one gets treated, but it is just a single component of one's overall “market value.” One's treatment depends on other markers of market value, including social status, competence, warmth, and any other cues of one's ability or willingness to confer benefits on partners. To completely understand biased treatment, we must also incorporate these other factors. [ABSTRACT FROM PUBLISHER]

Van de Vliert's findings may be explained by the psychology of threat and bargaining. Poor people facing extreme threats must cope by surrendering individual freedom in service of shared group needs. Wealthier people are more able to flee from threats and/or resist authoritarianism, so their leaders must concede greater freedom. Incorporating these factors (plus inequality) can sharpen researchers' predictions. [ABSTRACT FROM PUBLISHER]

The target article's important point is easily misunderstood to claim that all revenge is adaptive. Revenge and forgiveness can overstretch (or understretch) the bounds of utility due to misperceptions, minimization of costly errors, a breakdown within our evolved revenge systems, or natural genetic and developmental variation. Together, these factors can compound to produce highly abnormal instances of revenge and forgiveness. [ABSTRACT FROM AUTHOR]

While admirable, Guala's discussion of reciprocity suffers from a confusion between proximate causes (psychological mechanisms triggering behaviour) and ultimate causes (evolved function of those psychological mechanisms). Because much work on “strong reciprocity” commits this error, I clarify the difference between proximate and ultimate causes of cooperation and punishment. I also caution against hasty rejections of “wide readings” of experimental evidence. [ABSTRACT FROM PUBLISHER]

Recent studies in experimental economics have shown that many people have other-regarding preferences, potentially including preferences for altruism, reciprocity, and fairness. It is useful to investigate why people possess such preferences and what functional purpose they might serve outside the laboratory, because evolutionary and social learning perspectives both predict that cooperative sentiments should only exist if they bring benefits that outweigh the costs of other-regarding behavior. Theories of costly signaling suggest that altruistic acts may function (with or without intention) as signals of unobservable qualities such as resources or cooperative intent, and altruists may benefit (possibly unintentionally) from the advertisement of such qualities. After reviewing the theories that could potentially account for the evolution of altruism (Chapter 1), I test some predictions about cooperation derived from costly signaling theory. In Chapter 2, I show that participants in experimental public goods games were more cooperative when they had cues that they could benefit from having a good reputation, and that there was apparently some competition to be the most generous group member. Furthermore, in subsequent trust games, people tended to trust high public goods contributors more than low contributors. Chapter 3 failed to find evidence that granting high status to people makes them more likely to contribute to public goods or punish free-riders, but there was suggestive evidence that physical proximity to the experimenter affected contributions and punishment. In Chapter 4, I found that people tended to trust others who were willing to incur costs to punish those who free-ride on group cooperation provided that such punishment was justified, and men were more punitive than women. In Chapter 5, I show that women find altruistic men more desirable than neutral men for long-term relationships. Together, these results suggest that humans do treat altruism as a signal of willingness to be cooperative. These findings are discussed with respect to the adaptive design of cooperative sentiments as well as the current debate over group selection. [ABSTRACT FROM AUTHOR]