Punitive sentiment as an anti-free rider psychological device

From Envy to Radicalization

Models of radicalization have typically placed grievances at the heart of radicalization. In contrast, we argue that viewing the radicalizing agent as decidedly proactive, and less reactive, better accounts for the available data. At the core of our radicalization model is the functional structure of envy. The operative properties of the emotion align with essential and conspicuous features of the radicalization process: a motivation to monitor social differentials, an identification of sources of postulated welfare costs, an impulse to eliminate or depower purported competitors, an attempt to diffuse responsibility for one's aggressive actions, and the rejoicing at the envied agent's misfortune. Two of those operative properties are particularly important for our understanding of radicalization. Envy motivates the neutralization of competitors when responsibility for welfare costs is not objectively attributable to others' wrongdoing toward the party who feels injured. The "process of typification" serves as a means to diffuse responsibility. It extends the reach of individual concerns by downplaying the particulars of the personal situation motivating the envious agent while evoking universally shared interaction templates (e.g., humiliation, injustice) to appeal to a broader audience.

Threat-induced anxiety and selfishness in resource sharing: Behavioral and neural evidence

In real life, it is not unusual that we face potential threats (i.e., physical stimuli and environments that may cause harm or danger) with other individuals together, yet it remains largely unknown how threat-induced anxious feelings influence prosocial behaviors such as resource sharing. In this study, we investigated this question by combining functional magnetic resonance imaging and a novel paradigm. Together with an anonymous partner, each participant faced the possibility of receiving a 10-s noise administration, which had a low or high probability to be a threat (i.e., the intensity of noise can induce a high level of unpleasantness). Each participant first reported her/his immediate feeling of anxiety about the current situation (being threatened by the unpleasant noise), then decided how to split a number of resources (which could relieve the noise) between her/him and the partner. Behavioral results revealed that the participants showed a selfish bias in the threat conditions than in the safe conditions, and that self-reported anxiety feeling significantly predicted this bias. Functional magnetic resonance imaging results revealed that: (1) the activation level of the anterior insula was correlated with self-reported anxiety and (2) the connectivity between the anterior insula and the temporoparietal junction was sensitive to the modulating effect of anxiety on the selfish bias. These findings indicate the neural correlates of the association between threat-induced anxiety and prosocial tendencies in social interactions.

Cooperative and conformist behavioural preferences predict the dual dimensions of political ideology

Decades of research suggest that our political differences are best captured by two dimensions of political ideology. The dual evolutionary framework of political ideology predicts that these dimensions should be related to variation in social preferences for cooperation and group conformity. Here, we combine data from a New Zealand survey and a suite of incentivised behavioural tasks (n = 991) to test whether cooperative and conformist preferences covary with a pair of widely used measures of the two dimensions of political ideology-Social Dominance Orientation (SDO) and Right Wing Authoritarianism (RWA)-and related policy views. As predicted, we find that cooperative behaviour is negatively related to SDO and economically conservative policy views, while conformist behaviour in the form of social information use is positively related to RWA and socially conservative policy views. However, we did not find the predicted relationships between punitive and rule following behaviours and RWA or socially conservative views, raising questions about the interpretation of punishment and rule following tasks and the nature of authoritarian conformist preferences. These findings reveal how cooperative and conformist preferences that evolved to help us navigate social challenges in our ancestral past continue to track our political differences even today.

Discriminatory attitudes against unvaccinated people during the pandemic

During the COVID-19 pandemic, sizeable groups of unvaccinated people persist even in countries with high vaccine access¹. As a consequence, vaccination became a controversial subject of debate and even protest². Here we assess whether people express discriminatory attitudes in the form of negative affectivity, stereotypes and exclusionary attitudes in family and political settings across groups defined by COVID-19 vaccination status. We quantify discriminatory attitudes between vaccinated and unvaccinated citizens in 21 countries, covering a diverse set of cultures across the world. Across three conjoined experimental studies (n = 15,233), we demonstrate that vaccinated people express discriminatory attitudes towards unvaccinated individuals at a level as high as discriminatory attitudes that are commonly aimed at immigrant and minority populations^3-5. By contrast, there is an absence of evidence that unvaccinated individuals display discriminatory attitudes towards vaccinated people, except for the presence of negative affectivity in Germany and the USA. We find evidence in support of discriminatory attitudes against unvaccinated individuals in all countries except for Hungary and Romania, and find that discriminatory attitudes are more strongly expressed in cultures with stronger cooperative norms. Previous research on the psychology of cooperation has shown that individuals react negatively against perceived 'free-riders'^6,7, including in the domain of vaccinations^8,9. Consistent with this, we find that contributors to the public good of epidemic control (that is, vaccinated individuals) react with discriminatory attitudes towards perceived free-riders (that is, unvaccinated individuals). National leaders and vaccinated members of the public appealed to moral obligations to increase COVID-19 vaccine uptake^10,11, but our findings suggest that discriminatory attitudes-including support for the removal of fundamental rights-simultaneously emerged.

Association between Cooperative Attitude and High-Risk Behaviors on the Spread of COVID-19 Infection among Medical Students in Japan

The impact of high-risk behaviors on the spread of COVID-19 infection among young people is an important problem to address. This study analyzed the association between cooperativeness and high-risk behaviors. We conducted a cross-sectional study among fourth-year medical students at Tokyo Medical and Dental University. The students were asked about cooperative attitude in a hypothetical situation of performing a task together with an unfamiliar classmate, who did not cooperate to complete the task previously. The response items were as follows: "cooperate", "don't want to cooperate and do it alone (non-cooperative)", and "don't want to cooperate and let the partner do it alone (punishment)". Eating out and vaccine hesitancy were also treated as high-risk behaviors. Poisson regression was used to investigate the association between cooperative attitude and each high-risk behavior, adjusted for demographics. Of the 98 students, 23 (23.5%), 44 (44.9%), and 31 (31.6%) students chose "noncooperative", "cooperative", and "punishment", respectively. Cooperative-type students exhibited 2.77-fold (PR: 2.77, 95% CI: 1.03-7.46), and punishment-type students exhibited 3.16-fold greater risk of eating or drinking out (PR: 3.16, 95% CI: 1.14-8.75) compared with those of the noncooperative type. Among medical students, the "cooperative" type and "punishment" type comprised the high-risk group for eating out during the pandemic.

Help or punishment: acute stress moderates basal testosterone's association with prosocial behavior

The gonadal hormone testosterone is well-recognized to facilitate various behaviors for obtaining social status. A good reputation (i.e. competitive, generous, and trustworthy) is of crucial importance for acquiring high social status. It is unclear which type of reputation is preferred by individuals under the influence of testosterone. Given that the recent dual-hormone hypothesis emphasizes the modulating effect of stress (cortisol) on the influence of testosterone, it would be intriguing to test the role of stress-induced cortisol in testosterone-related reputation seeking. To test this hypothesis, we induced acute stress in 93 participants with cold pressor test (CPT) paradigm (vs. control condition), and then they were instructed to play a third-party intervention game, in which they made decisions as an uninvolved, outside the third party to punish a violator, help a victim, or do nothing. Salivary samples were obtained to assess participants' testosterone and cortisol levels. We split the testosterone concentration by median to low endogenous testosterone (LT) and high endogenous testosterone (HT). We found that HT individuals' prosocial preferences did not affect by acute stress. They were more likely to choose punishment than helping under both stress and control conditions. In contrast, individuals with low testosterone were more inclined to help than punish under control conditions. Interestingly, acute stress brought behavior patterns of LT individuals closer to those of HT individuals, that is, they reduced their helping behavior and increased the intensity of punishments. In this preliminary study on the preference inducement of testosterone for different types of prosocial behaviors, we discuss the physiological mechanism of the relationship between testosterone and reputation and the implications of these results for the dual-hormone hypothesis.HIGHLIGHTSLow testosterone (LT) individuals were more inclined to help than punish.High testosterone (HT) individuals were more inclined to punish than help.The HT individuals' preferences for prosocial types were not affected by acute stress.Acute stress brought the behavior patterns of LT individuals closer to those of HT individuals.

Hazers' Personality Characteristics and the Perception of School Climate in Slovenia

This article presents the initiation rite for the admission of newcomers to Slovenian upper secondary education, which is called "pheasanting" and has similar characteristics to hazing. It examines the relationship between certain personality traits of hazers with their perception of the school climate and the severity of the hazing activities they engage in (subtle, harassing, and violent hazing). In a sample of 460 students in the fourth grade of upper secondary education, 25.4% of them had carried out hazing in the previous 3 years, of which 47% performed only subtle, 24% harassment, and 29% violent hazing. Violent and harassment hazers justified their actions much more often than subtle hazers by dominating and distorting of the consequences and by diffusing responsibility. They also had less empathy and perceived the school climate as enabling more aggressive attitude. However, violent hazers had the most negative attitude toward hazing, while harassment hazers found hazing most acceptable. Finally, some practical implications of the results at individual and school level are discussed.

From Help to Harm: Increases in Status, Perceived Under-Reciprocation, and the Consequences for Access to Strategic Help and Social Undermining Among Female, Racial Minority, and White Male Top Managers

This paper explores how social psychological biases impede the social exchange relations of executives who ascend to high-status corporate leadership positions. We theorize that a combination of self-serving attribution biases among executives who gain status and egocentric biases of their prior benefactors cause a systematic difference in perceptions about the relative importance of that help to the beneficiary’s success. This leads to the perception among prior benefactors that the high-status executives have not adequately reciprocated their help. We then extend this argument to explain why perceptions of under-reciprocation are heightened when the high-status executive is a racial minority or a woman but reduced when the prior benefactor is a racial minority or a woman. The final element of our theoretical framework examines the social consequences of perceived under-reciprocation for corporate leaders. We suggest that the high-status leaders’ access to strategic help is reduced, and they may become the target of social undermining that can damage their broader reputation. The findings support our social psychological perspective on social exchange in corporate leadership, revealing how and why executives who have ascended to high-status positions not only may encounter difficulty obtaining assistance from fellow leaders but also may experience adverse reversals in their social exchange ties such that managers who previously aided them engage in socially harmful behavior toward them.

Passport to freedom? Immunity passports for COVID-19

The COVID-19 pandemic has led a number of countries to introduce restrictive 'lockdown' policies on their citizens in order to control infection spread. Immunity passports have been proposed as a way of easing the harms of such policies, and could be used in conjunction with other strategies for infection control. These passports would permit those who test positive for COVID-19 antibodies to return to some of their normal behaviours, such as travelling more freely and returning to work. The introduction of immunity passports raises a number of practical and ethical challenges. In this paper, we seek to review the challenges relating to various practical considerations, fairness issues, the risk to social cooperation and the impact on people's civil liberties. We make tentative recommendations for the ethical introduction of immunity passports.

Environmental adversity is associated with lower investment in collective actions

Environmental adversity is associated with a wide range of biological outcomes and behaviors that seem to fulfill a need to favor immediate over long-term benefits. Adversity is also associated with decreased investment in cooperation, which is defined as a long-term strategy. Beyond establishing the correlation between adversity and cooperation, the channel through which this relationship arises remains unclear. We propose that this relationship is mediated by a present bias at the psychological level, which is embodied in the reproduction-maintenance trade-off at the biological level. We report two pre-registered studies applying structural equation models to test this relationship on large-scale datasets (the European Values Study and the World Values Survey). The present study replicates existing research linking adverse environments (both in childhood and in adulthood) with decreased investment in adult cooperation and finds that this association is indeed mediated by variations in individuals’ reproduction-maintenance trade-off.

Punishment: one tool, many uses

Humans are outstanding in their ability to cooperate with unrelated individuals, and punishment - paying a cost to harm others - is thought to be a key supporting mechanism. According to this view, cooperators punish defectors, who respond by behaving more cooperatively in future interactions. However, a synthesis of the evidence from laboratory and real-world settings casts serious doubts on the assumption that the sole function of punishment is to convert cheating individuals into cooperators. Instead, punishment often prompts retaliation and punishment decisions frequently stem from competitive, rather than deterrent motives. Punishment decisions often reflect the desire to equalise or elevate payoffs relative to targets, rather than the desire to enact revenge for harm received or to deter cheats from reoffending in future. We therefore suggest that punishment also serves a competitive function, where what looks like spiteful behaviour actually allows punishers to equalise or elevate their own payoffs and/or status relative to targets independently of any change in the target's behaviour. Institutions that reduce or remove the possibility that punishers are motivated by relative payoff or status concerns might offer a way to harness these competitive motives and render punishment more effective at restoring cooperation.

Cross-Cultural and Cross-Organizational Evidence for an Evolved Hazing Motivation

We report the first cross-cultural and cross-organizational evidence for an evolved hazing motivation. Using experiments performed in the United States, Japan, and among members of a hazing and a nonhazing organization, we demonstrate an invariant set of core hazing predictors. In particular, we show that the perception of near-term group benefits, which would have been ancestrally exploitable by new group members, substantially increases desired hazing severity in all samples. Results are discussed in light of human organizational psychology and the difficulty of reliably suppressing hazing behavior.

Evolutionary Models of Leadership : Tests and Synthesis

This study tested four theoretical models of leadership with data from the ethnographic record. The first was a game-theoretical model of leadership in collective actions, in which followers prefer and reward a leader who monitors and sanctions free-riders as group size increases. The second was the dominance model, in which dominant leaders threaten followers with physical or social harm. The third, the prestige model, suggests leaders with valued skills and expertise are chosen by followers who strive to emulate them. The fourth proposes that in small-scale, kin-based societies, men with high neural capital are best able to achieve and maintain positions of social influence (e.g., as headmen) and thereby often become polygynous and have more offspring than other men, which positively selects for greater neural capital. Using multiple search strategies we identified more than 1000 texts relevant to leadership in the Probability Sample of 60 cultures from the Human Relations Area Files (HRAF). We operationalized the model with variables and then coded all retrieved text records on the presence or absence of evidence for each of these 24 variables. We found mixed support for the collective action model, broad support for components of the prestige leadership style and the importance of neural capital and polygyny among leaders, but more limited support for the dominance leadership style. We found little evidence, however, of emulation of, or prestige-biased learning toward, leaders. We found that improving collective actions, having expertise, providing counsel, and being respected, having high neural capital, and being polygynous are common properties of leaders, which warrants a synthesis of the collective action, prestige, and neural capital and reproductive skew models. We sketch one such synthesis involving high-quality decision-making and other computational services.

In Defense of the Commons: Young Children Negatively Evaluate and Sanction Free Riders

Human flourishing depends on individuals paying costs to contribute to the common good, but such arrangements are vulnerable to free riding, in which individuals benefit from others' contributions without paying costs themselves. Systems of tracking and sanctioning free riders can stabilize cooperation, but the origin of such tendencies is not well understood. Here, we provide evidence that children as young as 4 years old negatively evaluate and sanction free riders. Across six studies, we showed that these tendencies are robust, large in magnitude, tuned to intentional rather than unintentional noncontribution, and generally consistent across third- and first-party cases. Further, these effects cannot be accounted for by factors that frequently co-occur with free riding, such as nonconforming behaviors or the costs that free riding imposes on the group. Our findings demonstrate that from early in life, children both hold and enforce a normative expectation that individuals are intrinsically obligated to contribute to the common good.

Moral Judgments of In-Group and Out-Group Harm in Post-conflict Urban and Rural Croatian Communities

Our research brings to light features of the social world that impact moral judgments and how they do so. The moral vignette data presented were collected in rural and urban Croatian communities that were involved to varying degrees in the Croatian Homeland War. We argue that rapid shifts in moral accommodations during periods of violent social strife can be explained by considering the role that coordination and social agents' ability to reconfigure their social network (i.e., relational mobility) play in moral reasoning. Social agents coordinate on (moral) norms, a general attitude which broadly facilitates cooperation, and makes possible the collective enforcement of compliance. During social strife interested parties recalibrate their determination of others' moral standing and recast their established moral circle, in accordance with their new or prevailing social investments. To that extent, social coordination-and its particular promoters, inhibitors, and determinants-effects significant changes in individuals' ranking of moral priorities. Results indicate that rural participants evaluate the harmful actions of third parties more harshly than urban participants. Coordination mediates that relationship between social environment and moral judgment. Coordination also matters more for the moral evaluation of the harmful actions of moral scenarios involving characters belonging to different social units than for scenarios involving characters belonging to the same group. Participants high in relational mobility-that ability to recompose one's social network-moralize similarly wrongdoings perpetrated by both in- and out-group members. Those low in relational mobility differentiate when an out-group member causes the harm. Additionally, perceptions of third-party guilt are also affected by specifics of the social environment. Overall, we find that social coordination and relational mobility affect moral reasoning more so than ethnic commitment.

The development of intention-based sociomoral judgment and distribution behavior from a third-party stance

The current study investigated children's intention-based sociomoral judgments and distribution behavior from a third-party stance. An actor puppet showed either positive or negative intention toward a target puppet, which had previously performed a prosocial or antisocial action toward others (i.e., children witnessed various types of indirect reciprocity). Children (3- and 5-year-olds) were asked to make sociomoral judgments and to distribute resources to the actor puppet. Results showed that 5-year-olds were more likely than 3-year-olds to be influenced by intention when they made their judgment and distributed resources. The target's previous actions affected only 5-year-olds' intent-based social preference. These results suggest that children's judgments about intent-based indirect reciprocity develop from ages 3 to 5 years.

Folk-economic beliefs: An evolutionary cognitive model

The domain of "folk-economics" consists in explicit beliefs about the economy held by laypeople, untrained in economics, about such topics as, for example, the causes of the wealth of nations, the benefits or drawbacks of markets and international trade, the effects of regulation, the origins of inequality, the connection between work and wages, the economic consequences of immigration, or the possible causes of unemployment. These beliefs are crucial in forming people's political beliefs and in shaping their reception of different policies. Yet, they often conflict with elementary principles of economic theory and are often described as the consequences of ignorance, irrationality, or specific biases. As we will argue, these past perspectives fail to predict the particular contents of popular folk-economic beliefs and, as a result, there is no systematic study of the cognitive factors involved in their emergence and cultural success. Here we propose that the cultural success of particular beliefs about the economy is predictable if we consider the influence of specialized, largely automatic inference systems that evolved as adaptations to ancestral human small-scale sociality. These systems, for which there is independent evidence, include free-rider detection, fairness-based partner choice, ownership intuitions, coalitional psychology, and more. Information about modern mass-market conditions activates these specific inference systems, resulting in particular intuitions, for example, that impersonal transactions are dangerous or that international trade is a zero-sum game. These intuitions in turn make specific policy proposals more likely than others to become intuitively compelling, and, as a consequence, exert a crucial influence on political choices.

The Evolutionary Psychology of War: Offense and Defense in the Adapted Mind

The study of warfare from an evolutionary perspective has expanded rapidly over the last couple of decades. However, it has tended to focus on the ancestral origins, prevalence, and instruments of war rather than adaptationist analyses of its underlying psychology. I argue that our evolved coalitional psychology may contain a set of distinct evolved heuristics designed specifically for offensive and defensive coalitional aggression. Data from two survey experiments are presented, in which subjects were given scenarios depicting offensive or defensive aggression and were told to make decisions, for example, regarding their willingness to participate in the conflict, their opinions of others who did not choose to participate, and their expectations benefit. The results indicate that humans do indeed distinguish readily between these two domains and that their willingness to participate, as well as their emotional responses toward others, is highly contingent upon this informational cue in adaptively relevant ways. In addition, and consistent with parental investment theory, data reveal a range of sex differences in attitudes toward coalitional aggression in the two conflict domains. Beyond the study of warfare, this project has implications for our understanding of the relationship between individual behavior and group dynamics, as well as for our understanding of the mechanisms by which the psychological framing of political events can lead to important social outcomes.

The Paranoid Optimist: An Integrative Evolutionary Model of Cognitive Biases

Human cognition is often biased, from judgments of the time of impact of approaching objects all the way through to estimations of social outcomes in the future. We propose these effects and a host of others may all be understood from an evolutionary psychological perspective. In this article, we elaborate error management theory (EMT; Haselton & Buss, 2000). EMT predicts that if judgments are made under uncertainty, and the costs of false positive and false negative errors have been asymmetric over evolutionary history, selection should have favored a bias toward making the least costly error. This perspective integrates a diverse array of effects under a single explanatory umbrella, and it yields new content-specific predictions.

Accounting for reciprocity in negotiation and social exchange

People generally adhere to the norm of reciprocity during both tacit and negotiated exchange. Emotional responses generated from profitable and unprofitable exchange facilitate the formation of motives to settle scores with others. In two studies we examine how exchange incidents trigger positive and negative emotional responses, bargaining behavior, and process. In Study 1, we developed measures of emotional response toward the counterpart that can index the state of relational accounts between parties. In a complex, multi-issue negotiation, The measures show that prior profitable or unprofitable exchange experiences shifted affect and individual social motives, as well as initial bargaining positions. In Study 2, shifts in relational accounts altered the bargaining process and subsequent implementation of agreements. The relational accounting concept represents an important link for understanding how negotiation functions as a sub-process in the wider stream of social exchange.

Five-year-olds punish antisocial adults

The human tendency to impose costs on those who have behaved antisocially towards third parties (third-party punishment) has a formative influence on societies, yet very few studies of the development of this tendency exist. In most studies where young children have punished, participants have imposed costs on puppets, leaving open the question as to whether young children punish in real third-party situations. Here, five-year-olds were given the opportunity to allocate desirable or unpleasant items to antisocial and neutral adults, who were presented as real and shown on video. Neutral individuals were almost always allocated only desirable items. Antisocial individuals were instead usually allocated unpleasant items, as long as participants were told they would give anonymously. Most participants who were instead told they would give in person did not allocate unpleasant items, although a minority did so. This indicates that the children interpreted the situation as real, and that whereas they genuinely desired to punish antisocial adults, they did not usually dare do so in person. Boys punished more frequently than girls. The willingness of preschoolers to spontaneously engage in third-party punishment, occasionally even risking the social costs of antagonizing an anti-social adult, demonstrates a deep-seated early-developing punitive sentiment in humans.

Pro-community altruism and social status in a Shuar village

Reciprocity theory (RT) and costly signaling theory (CST) provide different explanations for the high status of pro-community altruists: RT proposes that altruists are positively and negatively sanctioned by others, whereas CST proposes that altruists are attractive to others. Only RT, however, is beset by first- and higher-order free rider problems, which must be solved in order for RT to explain status allocations. In this paper, several solutions to RT's free rider problems are proposed, and data about status allocations to Ecuadorian Shuar pro-community altruists are analyzed in light of RT and CST. These data confirm that perceived pro-community altruists are indeed high status and suggest that (1) community residents skillfully monitor the altruism of coresidents, (2) residents who engage in opportunities to broadcast desirable qualities are high status only to the extent that they are considered altruistic, and (3) individuals who sanction coresidents based on coresidents' contributions to the community are themselves relatively high status. To a greater extent than CST, RT straightforwardly predicts all of these results.

Norm enforcement among the Ju/'hoansi Bushmen : A case of strong reciprocity?

The concept of cooperative communities that enforce norm conformity through reward, as well as shaming, ridicule, and ostracism, has been central to anthropology since the work of Durkheim. Prevailing approaches from evolutionary theory explain the willingness to exert sanctions to enforce norms as self-interested behavior, while recent experimental studies suggest that altruistic rewarding and punishing-"strong reciprocity"-play an important role in promoting cooperation. This paper will use data from 308 conversations among the Ju/'hoansi (!Kung) Bushmen (a) to examine the dynamics of norm enforcement, (b) to evaluate the costs of punishment in a forager society and understand how they are reduced, and

Morality: An Evolutionary Account

Refinements in Darwin's theory of the origin of a moral sense create a framework equipped to organize and integrate contemporary theory and research on morality. Morality originated in deferential, cooperative, and altruistic "social instincts," or decision-making strategies, that enabled early humans to maximize their gains from social living and resolve their conflicts of interest in adaptive ways. Moral judgments, moral norms, and conscience originated from strategic interactions among members of groups who experienced confluences and conflicts of interest. Moral argumentation buttressed by moral reasoning is equipped to generate universal and impartial moral standards. Moral beliefs and standards are products of automatic and controlled information-processing and decision-making mechanisms. To understand how people make moral decisions, we must understand how early evolved mechanisms in the old brain and recently evolved mechanisms in the new brain are activated and how they interact. Understanding what a sense of morality is for helps us understand what it is.

Context-dependent social evaluation in 4.5-month-old human infants: the role of domain-general versus domain-specific processes in the development of social evaluation

The ability to distinguish friends from foes allows humans to engage in mutually beneficial cooperative acts while avoiding the costs associated with cooperating with the wrong individuals. One way to do so effectively is to observe how unknown individuals behave toward third parties, and to selectively cooperate with those who help others while avoiding those who harm others. Recent research suggests that a preference for prosocial over antisocial individuals emerges by the time that infants are 3 months of age, and by 8 months, but not before, infants evaluate others' actions in context: they prefer those who harm, rather than help, individuals who have previously harmed others. Currently there are at least two reasons for younger infants' failure to show context-dependent social evaluations. First, this failure may reflect fundamental change in infants' social evaluation system over the first year of life, in which infants first prefer helpers in any situation and only later evaluate prosocial and antisocial actors in context. On the other hand, it is possible that this developmental change actually reflects domain-general limitations of younger infants, such as limited memory and processing capacities. To distinguish between these possibilities, 4.5-month-olds in the current studies were habituated, rather than familiarized as in previous work, to one individual helping and another harming a third party, greatly increasing infants' exposure to the characters' actions. Following habituation, 4.5-month-olds displayed context-dependent social preferences, selectively reaching for helpers of prosocial and hinderers of antisocial others. Such results suggest that younger infants' failure to display global social evaluation in previous work reflected domain-general rather than domain-specific limitations.

The evolution of leader-follower reciprocity: the theory of service-for-prestige

We describe the service-for-prestige theory of leadership, which proposes that voluntary leader-follower relations evolved in humans via a process of reciprocal exchange that generated adaptive benefits for both leaders and followers. We propose that although leader-follower relations first emerged in the human lineage to solve problems related to information sharing and social coordination, they ultimately evolved into exchange relationships whereby followers could compensate leaders for services which would otherwise have been prohibitively costly for leaders to provide. In this exchange, leaders incur costs to provide followers with public goods, and in return, followers incur costs to provide leaders with prestige (and associated fitness benefits). Because whole groups of followers tend to gain from leader-provided public goods, and because prestige is costly for followers to produce, the provisioning of prestige to leaders requires solutions to the "free rider" problem of disrespectful followers (who benefit from leader services without sharing the costs of producing prestige). Thus service-for-prestige makes the unique prediction that disrespectful followers of beneficial leaders will be targeted by other followers for punitive sentiment and/or social exclusion. Leader-follower relations should be more reciprocal and mutually beneficial when leaders and followers have more equal social bargaining power. However, as leaders gain more relative power, and their high status becomes less dependent on their willingness to pay the costs of benefitting followers, service-for-prestige predicts that leader-follower relations will become based more on leaders' ability to dominate and exploit rather than benefit followers. We review evidential support for a set of predictions made by service-for-prestige, and discuss how service-for-prestige relates to social neuroscience research on leadership.

Moral Judgment and Action in Preverbal Infants and Toddlers

Although developmental psychologists traditionally explore morality from a learning and development perspective, some aspects of the human moral sense may be built-in, having evolved to sustain collective action and cooperation as required for successful group living. In this article, I review a recent body of research with infants and toddlers, demonstrating surprisingly sophisticated and flexible moral behavior and evaluation in a preverbal population whose opportunity for moral learning is limited at best. Although this work itself is in its infancy, it supports theoretical claims that human morality is a core aspect of human nature.

Do humans really punish altruistically? A closer look

Some researchers have proposed that natural selection has given rise in humans to one or more adaptations for altruistically punishing on behalf of other individuals who have been treated unfairly, even when the punisher has no chance of benefiting via reciprocity or benefits to kin. However, empirical support for the altruistic punishment hypothesis depends on results from experiments that are vulnerable to potentially important experimental artefacts. Here, we searched for evidence of altruistic punishment in an experiment that precluded these artefacts. In so doing, we found that victims of unfairness punished transgressors, whereas witnesses of unfairness did not. Furthermore, witnesses' emotional reactions to unfairness were characterized by envy of the unfair individual's selfish gains rather than by moralistic anger towards the unfair behaviour. In a second experiment run independently in two separate samples, we found that previous evidence for altruistic punishment plausibly resulted from affective forecasting error-that is, limitations on humans' abilities to accurately simulate how they would feel in hypothetical situations. Together, these findings suggest that the case for altruistic punishment in humans-a view that has gained increasing attention in the biological and social sciences-has been overstated.

Cognitive systems for revenge and forgiveness

Minimizing the costs that others impose upon oneself and upon those in whom one has a fitness stake, such as kin and allies, is a key adaptive problem for many organisms. Our ancestors regularly faced such adaptive problems (including homicide, bodily harm, theft, mate poaching, cuckoldry, reputational damage, sexual aggression, and the infliction of these costs on one's offspring, mates, coalition partners, or friends). One solution to this problem is to impose retaliatory costs on an aggressor so that the aggressor and other observers will lower their estimates of the net benefits to be gained from exploiting the retaliator in the future. We posit that humans have an evolved cognitive system that implements this strategy – deterrence – which we conceptualize as a revenge system. The revenge system produces a second adaptive problem: losing downstream gains from the individual on whom retaliatory costs have been imposed. We posit, consequently, a subsidiary computational system designed to restore particular relationships after cost-imposing interactions by inhibiting revenge and motivating behaviors that signal benevolence for the harmdoer. The operation of these systems depends on estimating the risk of future exploitation by the harmdoer and the expected future value of the relationship with the harmdoer. We review empirical evidence regarding the operation of these systems, discuss the causes of cultural and individual differences in their outputs, and sketch their computational architecture.

Who Punishes? Personality Traits Predict Individual Variation in Punitive Sentiment

Cross-culturally, participants in public goods games reward participants and punish defectors to a degree beyond that warranted by rational, profit-maximizing considerations. Costly punishment, where individuals impose costs on defectors at a cost to themselves, is thought to promote the maintenance of cooperation. However, despite substantial variation in the extent to which people punish, little is known about why some individuals, and not others, choose to pay these costs. Here, we test whether personality traits might contribute to variation in helping and punishment behavior. We first replicate a previous study using public goods scenarios to investigate effects of sex, relatedness and likelihood of future interaction on willingness to help a group member or to punish a transgressor. As in the previous study, we find that individuals are more willing to help related than unrelated needy others and that women are more likely to express desire to help than men. Desire to help was higher if the probability of future interaction is high, at least among women. In contrast, among these variables, only participant sex predicted some measures of punitive sentiment. Extending the replication, we found that punitive sentiment, but not willingness to help, was predicted by personality traits. Most notably, participants scoring lower on Agreeableness expressed more anger towards and greater desire to punish a transgressor, and were more willing to engage in costly punishment, at least in our scenario. Our results suggest that some personality traits may contribute to underpinning individual variation in social enforcement of cooperation.