The reputation of punishers

The impact of group membership on punishment versus partner rejection

People often display ingroup bias in punishment, punishing outgroup members more harshly than ingroup members. However, the impact of group membership may be less pronounced when people are choosing whether to stop interacting with someone (i.e., partner rejection). In two studies (N = 1667), we investigate the impact of group membership on both response types. Participants were assigned to groups based on a "minimal" groups paradigm (Study 1) or their self-reported political positions (Study 2) and played an incentivized economic game with other players. In this game, participants (Responders) responded to other players (Deciders). In the Punishment condition, participants could decrease the Decider's bonus pay. In the Partner Rejection condition, participants could reject future interactions with the Decider. Participants played once with an ingroup member and once with an outgroup member. To control for the effects of intent and outcome, scenarios also differed based on the Decider's Intent (selfish versus fair) and the Outcome (equal versus unequal distribution of resources). Participants punished outgroup members more than ingroup members, however group membership did not influence decisions to reject partners. These results highlight partner rejection as a boundary condition for the impact of group on responses to transgressions.

The evolution of private reputations in information-abundant landscapes

Reputations are critical to human societies, as individuals are treated differently based on their social standing1,2. For instance, those who garner a good reputation by helping others are more likely to be rewarded by third parties3-5. Achieving widespread cooperation in this way requires that reputations accurately reflect behaviour6 and that individuals agree about each other's standings7. With few exceptions8-10, theoretical work has assumed that information is limited, which hinders consensus7,11 unless there are mechanisms to enforce agreement, such as empathy12, gossip13-15 or public institutions16. Such mechanisms face challenges in a world where empathy, effective communication and institutional trust are compromised17-19. However, information about others is now abundant and readily available, particularly through social media. Here we demonstrate that assigning private reputations by aggregating several observations of an individual can accurately capture behaviour, foster emergent agreement without enforcement mechanisms and maintain cooperation, provided individuals exhibit some tolerance for bad actions. This finding holds for both first- and second-order norms of judgement and is robust even when norms vary within a population. When the aggregation rule itself can evolve, selection indeed favours the use of several observations and tolerant judgements. Nonetheless, even when information is freely accessible, individuals do not typically evolve to use all of it. This method of assessing reputations-'look twice, forgive once', in a nutshell-is simple enough to have arisen early in human culture and powerful enough to persist as a fundamental component of social heuristics.

Morality in the anthropocene: The perversion of compassion and punishment in the online world

Although much of human morality evolved in an environment of small group living, almost 6 billion people use the internet in the modern era. We argue that the technological transformation has created an entirely new ecosystem that is often mismatched with our evolved adaptations for social living. We discuss how evolved responses to moral transgressions, such as compassion for victims of transgressions and punishment of transgressors, are disrupted by two main features of the online context. First, the scale of the internet exposes us to an unnaturally large quantity of extreme moral content, causing compassion fatigue and increasing public shaming. Second, the physical and psychological distance between moral actors online can lead to ineffective collective action and virtue signaling. We discuss practical implications of these mismatches and suggest directions for future research on morality in the internet era.

Acting without considering personal costs signals trustworthiness in helpers but not punishers

Third-party punishment and helping can signal trustworthiness, but the interpretation of deliberation may vary: uncalculated help signals trustworthiness, but this may not hold for punishment. Using online experiments, we measured how deliberation over personal costs and impacts to targets affected the trustworthiness of helpers and punishers. We expected that personal cost-checking punishers and helpers would be trusted less. Conversely, impact deliberation was expected to increase the perceived trustworthiness of punishers but not helpers. Replicating previous work, we found that refraining from checking the personal cost of helping signals trustworthiness (although evidence for observers trusting uncalculating over calculating helpers was mixed). This did not extend to punishment: only uncalculating non-punishers were more trustworthy than cost-checking non-punishers. Impact deliberation results were mixed: deliberation affected the trust and trustworthiness of non-helpers more than helpers and no conclusive results were found for punishment. These results show that deliberation differentially affects assessments of those who help or punish others.

Evidence of direct and indirect reciprocity in network-structured economic games

Formal theoretical models propose that cooperative networks can be maintained when individuals condition behavior on social standing. Here, we empirically examine the predictions of such models of positive and negative indirect reciprocity using a suite of network-structured economic games in four rural Colombian communities (Nind = 496 individuals, Nobs = 53,876 ratings/transfers). We observe that, at a dyadic-level, individuals have a strong tendency to exploit and punish others in bad standing (e.g., those perceived as selfish), and allocate resources to those in good standing (e.g., those perceived as generous). These dyadic findings scale to a more generalized, community level, where reputations for being generous are associated with receipt of allocations, and reputations for being selfish are associated with receipt of punishment. These empirical results illustrate the roles that both positive and negative reciprocity, and costly punishment, play in sustaining community-wide cooperation networks.

Cross-societal variation in norm enforcement systems

Across human societies, people are sometimes willing to punish norm violators. Such punishment can take the form of revenge from victims, seemingly altruistic intervention from third parties, or legitimized sanctioning from institutional representatives. Although prior work has documented cross-cultural regularities in norm enforcement, substantial variation exists in the prevalence and forms of punishment across societies. Such cross-societal variation may arise from universal psychological mechanisms responding to different socio-ecological conditions, or from cultural evolutionary processes, resulting in different norm enforcement systems. To date, empirical evidence from comparative studies across diverse societies has remained disconnected, owing to a lack of interdisciplinary integration and a prevalent tendency of empirical studies to focus on different underpinnings of variation in norm enforcement. To provide a more complete view of the shared and unique aspects of punishment across societies, we review prior research in anthropology, economics and psychology, and take a first step towards integrating the plethora of socio-ecological and cultural factors proposed to explain cross-societal variation in norm enforcement. We conclude by discussing how future cross-societal research can use diverse methodologies to illuminate key questions on the domain-specificity of punishment, the diversity of tactics supporting social norms, and their role in processes of norm change. This article is part of the theme issue 'Social norm change: drivers and consequences'.

Action planning and execution cues influence economic partner choice

Prudently choosing who to interact with and who to avoid is an important ability to ensure that we benefit from a cooperative interaction. While the role of others' preferences, attributes, and values in partner choice have been established (Rossetti, Hilbe & Hauser, 2022), much less is known about whether the manner in which a potential partner plans and implements a decision provides helpful cues for partner choice. We used a partner choice paradigm in which participants chose who to interact with in the Prisoners' Dilemma. Before choosing a cooperation partner, participants were presented with information about the potential partners' decision-related actions in another round of the Prisoners' Dilemma. They received either information about the potential partners' planning during decision making (i.e., decision-time; Experiment 1) or action execution during decision implementation (i.e., movement directness; Experiment 2). Across both games, participants preferred to interact with those who planned actions quickly or executed actions with direct and smooth movements, indicating that they were cooperating confidently and without deliberation. This demonstrates that action cues present in either the planning or implementation of economic decisions influence partner choice. We discuss implications of this finding for human decision-making and perception-action coupling in action understanding.

Communicating emotions, but not expressing them privately, reduces moral punishment in a Prisoner's Dilemma game

The existence of moral punishment, that is, the fact that cooperative people sacrifice resources to punish defecting partners requires an explanation. Potential explanations are that people punish defecting partners to privately express or to communicate their negative emotions in response to the experienced unfairness. If so, then providing participants with alternative ways to privately express or to communicate their emotions should reduce moral punishment. In two experiments, participants interacted with cooperating and defecting partners in a Prisoner's Dilemma game. After each round, participants communicated their emotions to their partners (Experiments 1 and 2) or only expressed them privately (Experiment 2). Each trial concluded with a costly punishment option. Compared to a no-expression control group, moral punishment was reduced when emotions were communicated to the defecting partner but not when emotions were privately expressed. Moral punishment may thus serve to communicate emotions to defecting partners. However, moral punishment was only reduced but far from being eliminated, suggesting that the communication of emotions does not come close to replacing moral punishment. Furthermore, prompting participants to focus on their emotions had undesirable side-effects: Privately expressing emotions diminished cooperation, enhanced hypocritical punishment (i.e., punishment of defecting partners by defecting participants), and induced an unspecific bias to punish the partners irrespective of their actions.

Third-party punishers who express emotions are trusted more

Third party punishment (TPP) is thought to be crucial to the evolution and maintenance of human cooperation. However, this type of punishment is often not rewarded, perhaps because punishers' underlying motives are unclear. We propose that the expression of moral emotions could solve this problem by advertising such motives. In each of three experiments (n = 1711), a third-party punishment game was followed by a trust game. Third parties expressed anger or disgust instead of, or in addition to, financial punishment. Results showed that third parties who expressed these emotions were trusted more than those who didn't express (Experiment 1), and more than those who financially punished (Experiment 2). Moreover, third parties who expressed while financially punishing were trusted more than those who punished without expressing (Experiment 3). Findings suggest that emotion expression might play a role in the evolution and maintenance of cooperation by facilitating TPP.

Self-serving reward and punishment: evidence from the laboratory

Reward for altruism and punishment for selfishness are crucial components for the maintenance of society. Past studies have provided strong evidence that people are willing to incur costs to punish selfish behaviors and to reward altruistic behaviors, but how their willingness to do so depends on their relationship with the individuals conducting the anti-social or pro-social behaviors is much less explored. To probe into this question, we devised a three-stage experiment that combined a revised dictator game and third-party reward or punishment. We employed two payoff frameworks, alignment and conflict, and analyzed how third-party's willingness to reward and punish differed when their interests were either aligned or in conflict with the first-party under observation. We found that due to considerations for personal interests, third-party's reward and punishment levels deviated from what was deemed "legitimate" by society, that is, the level of reward and punishment that enhances society's intrinsic motivations to comply with social norms and act pro-socially. When an anti-social behavior was observed, third-party punished less severely under the alignment framework than under the conflict framework; when a pro-social behavior was observed, third-party demonstrated self-serving reward under the alignment framework, but they rewarded altruistically under the conflict framework. These findings provided evidence for third-party's self-serving reward and punishment.

Punishment in the public goods game is evaluated negatively irrespective of non-cooperators' motivation

The evolution of human cooperation toward strangers remains puzzling. While the punishment of non-cooperators is a possible explanation, whether punishments can help cooperation evolve depends on how people evaluate punishers. Thus, it is of vital importance to elucidate the perception of punishers. Previous studies have found that punishment is evaluated differently in different contexts; punishers are negatively and positively evaluated in the public goods game with punishment (PGG-P) and in the third-party punishment game (TPP), respectively. To disentangle the mixed evidence, our research focused on motivations for non-cooperation and examined whether different motivations for non-cooperation could explain the inconsistent findings. We hypothesized that people positively evaluate punishers when they punish those who non-cooperated to exploit others (greed), e.g., in a TPP situation. Contrastingly, people negatively evaluate punishers when they punish those who non-cooperated to avoid exploitation (fear), e.g., in a PGG-P situation. If so, in either game, punishers would be evaluated positively in situations where greed dominates, and negatively in situations where fear dominates the non-cooperation motivation. To test this, we conducted two online experiments with hypothetical scenarios in which the decision-making order was used to manipulate the motivations of non-cooperators. The results of Study 1 (N = 240) using only PGG-P and Study 2 (N = 602) using both PGG-P and TPP showed that the non-cooperation motivation did not have a significant effect on the evaluations of punishers and non-punishers. Punishers (vs non-punishers) were evaluated negatively in PGG-P and positively in TPP regardless of the decision-making order of non-cooperation. We discussed the role of higher-order information in the evaluation of punishment.

Children endorse deterrence motivations for third-party punishment but derive higher enjoyment from compensating victims

Children's punishment behavior may be driven by both retribution and deterrence, but the potential primacy of either motive is unknown. Moreover, children's punishment enjoyment and compensation enjoyment have never been directly contrasted. Here, British, Colombian, and Italian 7- to 11-year-old children (N = 123) operated a Justice System in which they viewed different moral transgressions in Minecraft, a globally popular video game, either face-to-face with an experimenter or over the internet. Children could respond to transgressions by punishing transgressors and compensating victims. The purpose of the system was framed in terms of retribution, deterrence, or compensation between participants. Children's performance, endorsement, and enjoyment of punishment and compensation were measured, along with their endorsement of retribution versus deterrence as punishment justifications, during and/or after justice administration. Children overwhelmingly endorsed deterrence over retribution as their punishment justification irrespective of age. When asked to reproduce the presented frame in their own words, children more reliably reproduced the deterrence frame rather than the retribution frame. Punishment enjoyment decreased while compensation enjoyment increased over time. Despite enjoying compensation more, children preferentially endorsed punishment over compensation, especially with increasing age and transgression severity. Reported deterrent justifications, superior reproduction of deterrence framing, lower enjoyment of punishment than of compensation, and higher endorsement of punishment over compensation together suggest that children felt that they ought to mete out punishment as a means to deter future transgressions. Face-to-face and internet-mediated responses were not distinguishable, supporting a route to social psychology research with primary school-aged children unable to physically visit labs.

Trust within human-machine collectives depends on the perceived consensus about cooperative norms

With the progress of artificial intelligence and the emergence of global online communities, humans and machines are increasingly participating in mixed collectives in which they can help or hinder each other. Human societies have had thousands of years to consolidate the social norms that promote cooperation; but mixed collectives often struggle to articulate the norms which hold when humans coexist with machines. In five studies involving 7917 individuals, we document the way people treat machines differently than humans in a stylized society of beneficiaries, helpers, punishers, and trustors. We show that a different amount of trust is gained by helpers and punishers when they follow norms over not doing so. We also demonstrate that the trust-gain of norm-followers is associated with trustors' assessment about the consensual nature of cooperative norms over helping and punishing. Lastly, we establish that, under certain conditions, informing trustors about the norm-consensus over helping tends to decrease the differential treatment of both machines and people interacting with them. These results allow us to anticipate how humans may develop cooperative norms for human-machine collectives, specifically, by relying on already extant norms in human-only groups. We also demonstrate that this evolution may be accelerated by making people aware of their emerging consensus.

Planning with Theory of Mind

Understanding Theory of Mind should begin with an analysis of the problems it solves. The traditional answer is that Theory of Mind is used for predicting others' thoughts and actions. However, the same Theory of Mind is also used for planning to change others' thoughts and actions. Planning requires that Theory of Mind consists of abstract structured causal representations and supports efficient search and selection from innumerable possible actions. Theory of Mind contrasts with less cognitively demanding alternatives: statistical predictive models of other people's actions, or model-free reinforcement of actions by their effects on other people. Theory of Mind is likely used to plan novel interventions and predict their effects, for example, in pedagogy, emotion regulation, and impression management.

Potential influence of decision time on punishment behavior and its evaluation

Previous studies on whether punishers are rewarded by reputational gains have yielded conflicting results. Some studies have argued that punitive behaviors potentially result in a positive evaluation, while others have found the opposite. This study aims to clarify the conditions that lead to the positive evaluation of costly punishment. Study 1 utilized one-round and repeated public goods game (PGG) situations and manipulated decision time for participants' punitive behavior toward the non-cooperative person in the situation. We also asked participants to report their impression evaluations of punitive behavior toward non-cooperative people. Moreover, utilizing the second- and third-party punishment games, Study 2 manipulated the decision time of participants' punitive behavior toward the self-interested person and asked them to evaluate the punitive behavior. The results showed that those who punished intuitively were not likely to be evaluated positively. However, punishers were rewarded when the decision to punish was made after deliberation or made by those who were not direct victims. These findings extend previous research on the evaluation of punitive behavior and reveal that deliberative punishment is evaluated positively occasionally.

Culture and group-functional punishment behaviour

Humans often 'altruistically' punish non-cooperators in one-shot interactions among genetically unrelated individuals. This poses an evolutionary puzzle because altruistic punishment enforces cooperation norms that benefit the whole group but is costly for the punisher. One key explanation is that punishment follows a social-benefits logic: it is eminently normative and group-functional (drawing on cultural group selection theories). In contrast, mismatch-based deterrence theory argues that punishment serves the individual-level function of deterring mistreatment of oneself and one's allies, hinging upon the evolved human coalitional psychology. We conducted multilateral-cooperation experiments with a sample of Spanish Romani people (Gitanos or Calé) and the non-Gitano majority. The Gitanos represent a unique case study because they rely heavily on close kin-based networks and display a strong ethnic identity. We find that Gitano non-cooperators were not punished by co-ethnics in only-Gitano (ethnically) homogeneous groups but were harshly punished by other Gitanos and by non-Gitanos in ethnically mixed groups. Our findings suggest the existence of culture-specific motives for punishment: Gitanos, especially males, appear to use punishment to protect their ethnic identity, whereas non-Gitanos use punishment to protect a norm of universal cooperation. Only theories that consider normative, group-functional forces underlying punishment behaviour can explain our data.

Distinctive roles of mPFC subregions in forming impressions and guiding social interaction based on others' social behaviour

People can quickly form impressions of others from their social behaviour, which can guide their future social interactions. This study investigated how the type and timing of others' social decisions affect the impression formation and social interactions. In each trial, participants watched a responder's decision in an ultimatum game, decided whether to choose the responder as their next partner for proposer or responder and reported the perceived warmth, competence and likability of the responder. Participants preferred responders who accepted (i.e. accepters) unfair offers for the responder and those who rejected (i.e. rejecters) unfair offers for the proposer in their next ultimatum game, and the rostral medial prefrontal cortex (mPFC) activity encoded such a strategic context-dependent valuation when choosing partners. Slow rejecters were perceived as warmer than fast rejecters, which was mirrored by the anterior mid-cingulate cortex activity when watching others' decisions, possibly detecting and resolving conflicting impressions. Finally, those who perceived accepters vs rejecters as warmer showed higher ventral mPFC responses to accepters vs rejecters when choosing a partner, regardless of the context. The present study suggests that distinctive subregions of the mPFC may be differentially involved in forming impressions and guiding social interactions with others based on their social behaviours.

Material Benefits Crowd Out Moralistic Punishment

Across four experiments with U.S.-based online participants (N = 1,495 adults), I found that paying people to engage in moralistic punishment reduces their willingness to do so. In an economic game with real stakes, providing a monetary bonus for engaging in third-party punishment of unfair offers nearly cut participants' willingness to do so in half. In judgments of hypothetical transgressions, participants viewed punishers who accepted payment as having worse character and rated the punishers' punitive actions as less morally acceptable. Willingness to engage in punishment was restored if participants were offered large enough payments or were told that punishment accompanied by payment still signals moral virtue. Data were consistent with a signal-corruption mechanism whereby payment interferes with the prosocial signal that moralistic punishment provides about a punisher's motives. These findings have implications for the cultural evolution of punishment and suggest that understanding perpetrators' sociomoral incentives is essential to implementing conflict-reduction policies.

Motivations to reciprocate cooperation and punish defection are calibrated by estimates of how easily others can switch partners

Evolutionary models of dyadic cooperation demonstrate that selection favors different strategies for reciprocity depending on opportunities to choose alternative partners. We propose that selection has favored mechanisms that estimate the extent to which others can switch partners and calibrate motivations to reciprocate and punish accordingly. These estimates should reflect default assumptions about relational mobility: the probability that individuals in one’s social world will have the opportunity to form relationships with new partners. This prior probability can be updated by cues present in the immediate situation one is facing. The resulting estimate of a partner’s outside options should serve as input to motivational systems regulating reciprocity: Higher estimates should down-regulate the use of sanctions to prevent defection by a current partner, and up-regulate efforts to attract better cooperative partners by curating one’s own reputation and monitoring that of others. We tested this hypothesis using a Trust Game with Punishment (TGP), which provides continuous measures of reciprocity, defection, and punishment in response to defection. We measured each participant’s perception of relational mobility in their real-world social ecology and experimentally varied a cue to partner switching. Moreover, the study was conducted in the US (n = 519) and Japan (n = 520): societies that are high versus low in relational mobility. Across conditions and societies, higher perceptions of relational mobility were associated with increased reciprocity and decreased punishment: i.e., those who thought that others have many opportunities to find new partners reciprocated more and punished less. The situational cue to partner switching was detected, but relational mobility in one’s real social world regulated motivations to reciprocate and punish, even in the experimental setting. The current research provides evidence that motivational systems are designed to estimate varying degrees of partner choice in one’s social ecology and regulate reciprocal behaviors accordingly.

What Motivates Direct and Indirect Punishment?

Abstract. Punishment represents a key mechanism to deter norm violations and is motivated by retribution and/or general deterrence. Retribution-motivated punishment is tailored to offense severity, whereas deterrence-motivated punishment is tailored to different factors, including punishment observability. This study aimed to replicate and extend prior work by testing how offense severity and punishment observability motivate direct, confrontational punishment versus indirect, covert punishment. Participants ( N = 308) read vignettes describing offenses with varying severity (high vs. low) and punishment observability (high vs. low). We then assessed their punishment tendencies – overall, direct, and indirect – and their endorsement of retribution and deterrence motives. Findings supported a “strong version” of intuitive retributivism. Manipulating retribution-relevant information consistently influenced punishment: participants reported stronger overall, direct, and indirect punishment tendencies when severity was high (vs. low). Self-reported deterrence (but not retribution) motives positively related to overall, direct, and indirect punishment tendencies. However, manipulating deterrence-relevant information did not influence punishment.

Third-party punishers do not compete to be chosen as partners in an experimental game

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.

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.

Direct punishment and indirect reputation-based tactics to intervene against offences

Punishment and reputation-based mechanisms play a major role in supporting the evolution of human cooperation. Theoretical accounts and field observations suggest that humans use multiple tactics to intervene against offences-including confrontation, gossip and ostracism-which have unique benefits and costs. Here, we draw a distinction between direct punishment tactics (i.e. physical and verbal confrontation) and indirect reputation-based tactics (i.e. gossip and ostracism). Based on this distinction, we sketch the common and unique social functions that different tactics are tailored to serve and describe information-processing mechanisms that potentially underlie decisions concerning how to intervene against offences. We propose that decision rules guiding direct and indirect tactics should weigh information about the benefits of changing others' behaviour versus the costs of potential retaliation. Based on a synthesis of existing evidence, we highlight the role of situational, relational and emotional factors in motivating distinct punishment tactics. We suggest that delineating between direct and indirect tactics can inform debates about the prevalence and functions of punishment and the reputational consequences of third-party intervention against offences. We emphasize the need to study how people use reputation-based tactics for partner recalibration and partner choice, within interdependent relationships and social networks, and in daily life situations. This article is part of the theme issue 'The language of cooperation: reputation and honest signalling'.

Decoupling cooperation and punishment in humans shows that punishment is not an altruistic trait

Economic experiments have suggested that cooperative humans will altruistically match local levels of cooperation (conditional cooperation) and pay to punish non-cooperators (altruistic punishment). Evolutionary models have suggested that if altruists punish non-altruists this could favour the evolution of costly helping behaviours (cooperation) among strangers. An often-key requirement is that helping behaviours and punishing behaviours form one single conjoined trait (strong reciprocity). Previous economics experiments have provided support for the hypothesis that punishment and cooperation form one conjoined, altruistically motivated, trait. However, such a conjoined trait may be evolutionarily unstable, and previous experiments have confounded a fear of being punished with being surrounded by cooperators, two factors that could favour cooperation. Here, we experimentally decouple the fear of punishment from a cooperative environment and allow cooperation and punishment behaviour to freely separate (420 participants). We show, that if a minority of individuals is made immune to punishment, they (i) learn to stop cooperating on average despite being surrounded by high levels of cooperation, contradicting the idea of conditional cooperation and (ii) often continue to punish, 'hypocritically', showing that cooperation and punishment do not form one, altruistically motivated, linked trait.

Virtuous victims

How do people perceive the moral character of victims? We find, across a range of transgressions, that people frequently see victims of wrongdoing as more moral than nonvictims who have behaved identically. Across 17 experiments (total n = 9676), we document this Virtuous Victim effect and explore the mechanisms underlying it. We also find support for the Justice Restoration Hypothesis, which proposes that people see victims as moral because this perception serves to motivate punishment of perpetrators and helping of victims, and people frequently face incentives to enact or encourage these “justice-restorative” actions. Our results validate predictions of this hypothesis and suggest that the Virtuous Victim effect does not merely reflect (i) that victims look good in contrast to perpetrators, (ii) that people are generally inclined to positively evaluate those who have suffered, or (iii) that people hold a genuine belief that victims tend to be people who behave morally.

Third-Party Punishment or Compensation? It Depends on the Reputational Benefits

Third-party fairness maintenance could win some reputational benefits, and it includes two methods: punishment and compensation. We predicted that the third parties' preference between punishment and compensation are affected by whether they are free to choose between the two methods, and the affection could be interpreted through reputational benefits. The present study includes two sections. In Study 1, the participants acted as fourth parties who were asked to rate the reputations of the third parties who had chosen different response methods to an unfair result of the dictator game. The results showed that (1) there was no reputational difference between the two methods when third parties were not free to choose, (2) but the reputation of compensation was better when third parties were free to choose. In Study 2, the participants acted as third parties. The participants were asked to choose a method to respond to an unfair result of the dictator game. There were two reputational contexts: secret and open. The results showed that (1) when third parties were not free to choose, they had no preference between the two methods under the two reputational contexts, (2) but when third parties were free to choose freely, they prefer punishment under the secret context but prefer compensation under the open context. This study systematically reveals a reputational interaction between fourth and third parties, and verifies the affection of reputational benefits on the third parties' preference between punishment and compensation.

Reviewing Stranger on the Internet: The Role of Identifiability through “Reputation” in Online Decision Making

The stranger on the Internet effect has been studied in relation to self-disclosure. Nonetheless, quantitative evidence about how people mentally represent and perceive strangers online is still missing. Given the dynamic development of web technologies, quantifying how much strangers can be considered suitable for pro-social acts such as self-disclosure appears fundamental for a whole series of phenomena ranging from privacy protection to fake news spreading. Using a modified and online version of the Ultimatum Game (UG), we quantified the mental representation of the stranger on the Internet effect and tested if people modify their behaviors according to the interactors’ identifiability (i.e., reputation). A total of 444 adolescents took part in a 2 × 2 design experiment where reputation was set active or not for the two traditional UG tasks. We discovered that, when matched with strangers, people donate the same amount of money as if the other has a good reputation. Moreover, reputation significantly affected the donation size, the acceptance rate and the feedback decision making as well.

Noncompliance With Safety Guidelines as a Free-Riding Strategy: An Evolutionary Game-Theoretic Approach to Cooperation During the COVID-19 Pandemic

Evolutionary game theory and public goods games offer an important framework to understand cooperation during pandemics. From this perspective, the COVID-19 situation can be conceptualized as a dilemma where people who neglect safety precautions act as free riders, because they get to enjoy the benefits of decreased health risk from others' compliance with policies despite not contributing to or even undermining public safety themselves. At the same time, humans appear to carry a suite of evolved psychological mechanisms aimed at curbing free riding in order to ensure the continued provision of public goods, which can be leveraged to develop more effective measures to promote compliance with regulations. We also highlight factors beyond free riding that reduce compliance rates, such as the emergence of conspiratorial thinking, which seriously undermine the effectiveness of measures to suppress free riding. Together, the current paper outlines the social dynamics that occur in public goods dilemmas involving the spread of infectious disease, highlights the utility and limits of evolutionary game-theoretic approaches for COVID-19 management, and suggests novel directions based on emerging challenges to cooperation.

Scarce and directly beneficial reputations support cooperation

A human solution to the problem of cooperation is the maintenance of informal reputation hierarchies. Reputational information contributes to cooperation by providing guidelines about previous group-beneficial or free-rider behaviour in social dilemma interactions. How reputation information could be credible, however, remains a puzzle. We test two potential safeguards to ensure credibility: (i) reputation is a scarce resource and (ii) it is not earned for direct benefits. We test these solutions in a laboratory experiment in which participants played two-person Prisoner's Dilemma games without partner selection, could observe some other interactions, and could communicate reputational information about possible opponents to each other. Reputational information clearly influenced cooperation decisions. Although cooperation was not sustained at a high level in any of the conditions, the possibility of exchanging third-party information was able to temporarily increase the level of strategic cooperation when reputation was a scarce resource and reputational scores were directly translated into monetary benefits. We found that competition for monetary rewards or unrestricted non-monetary reputational rewards helped the reputation system to be informative. Finally, we found that high reputational scores are reinforced further as they are rewarded with positive messages, and positive gossip was leading to higher reputations.

Direct and indirect punishment of norm violations in daily life

Across societies, humans punish norm violations. To date, research on the antecedents and consequences of punishment has largely relied upon agent-based modeling and laboratory experiments. Here, we report a longitudinal study documenting punishment responses to norm violations in daily life (k = 1507; N = 257) and test pre-registered hypotheses about the antecedents of direct punishment (i.e., confrontation) and indirect punishment (i.e., gossip and social exclusion). We find that people use confrontation versus gossip in a context-sensitive manner. Confrontation is more likely when punishers have been personally victimized, have more power, and value offenders more. Gossip is more likely when norm violations are severe and when punishers have less power, value offenders less, and experience disgust. Findings reveal a complex punishment psychology that weighs the benefits of adjusting others' behavior against the risks of retaliation.

Cognitive Flexibility Matters: The Role of Multilevel Positive Affect and Cognitive Flexibility in Shaping Victims’ Cooperative and Uncooperative Behavioral Responses to Trust Violations

Despite a significant growth in the scholarly literature in the area of trust violations and repair in the last decade, extant work has largely ignored the complex and socially competent responses of the victims of these violations. Our framework integrates insights from affective events theory, the broaden-and-build theory of positive emotions, and theories of cognitive processing to suggest that cognitive flexibility is central to understanding how individuals respond to trust violations. Rather than viewing victims solely as gatekeepers to trust repair, we examine how victims’ cognitive processes are influenced by the affective context of those violations, which can, in turn, produce a spectrum of nuanced behavioral responses. We refer to this spectrum as the “swollen middle,” the range of behavior that resides between the extremes of impulsive revenge and forgiveness-based, communal cooperation. By integrating psychological theories of emotion and cognitive processing, we seek to highlight the central role of cognitive flexibility in the range of cooperative responses to trust violations. More broadly, we seek to contribute to the emergence of a new paradigm for studying interpersonal trust at work—a paradigm that explores trust-violating events as situated affect-laden experiences that interact with relevant organizational and interpersonal factors to influence employee behavior and trust dynamics in organizations.

Juvenile cleaner fish can socially learn the consequences of cheating

Social learning is often proposed as an important driver of the evolution of human cooperation. In this view, cooperation in other species might be restricted because it mostly relies on individually learned or innate behaviours. Here, we show that juvenile cleaner fish (Labroides dimidiatus) can learn socially about cheating consequences in an experimental paradigm that mimics cleaners' cooperative interactions with client fish. Juvenile cleaners that had observed adults interacting with model clients learned to (1) behave more cooperatively after observing clients fleeing in response to cheating; (2) prefer clients that were tolerant to cheating; but (3) did not copy adults' arbitrary feeding preferences. These results confirm that social learning can play an active role in the development of cooperative strategies in a non-human animal. They further show that negative responses to cheating can potentially shape the reputation of cheated individuals, influencing cooperation dynamics in interaction networks.

The source of punishment matters: Third-party punishment restrains observers from selfish behaviors better than does second-party punishment by shaping norm perceptions

Punishment aims to deter individuals’ selfish behaviors, but it can occasionally backfire. Some scholars have proposed promoting prosocial behaviors using punishment that communicates positive social norms because it provides additional motivation. However, it is unclear which factors affect the norm expressive function of punishment. This study proposes that third-party punishment communicates more positive normative information, and thus, promotes more prosocial behavior in observers than does second-party punishment. Using dictator games, we investigated the effects of second-party punishment compared to third-party punishment of another’s unfair sharing on observers’ norm perceptions and subsequent sharing decision-making. Two experiments consistently found that third-party punishment was more effective than second-party punishment at inducing observers’ beliefs that unfair distribution was unusual (descriptive norm) and unacceptable (injunctive norm). The altered descriptive but not injunctive norm perception further guided individuals’ own sharing behaviors. Taken together, these results suggest that third-party punishment might be better than second-party punishment at decreasing selfish behaviors by shaping individuals’ norm perceptions, especially descriptive norm perception, regarding the relevant behaviors.

Aggression, Conflict, and the Formation of Intimidating Group Reputation

From inmates in prison gangs to soldiers in elite units, the intimidating reputation of groups often precedes its members. While individual reputation is known to affect people’s aggressiveness, whether one’s group reputation can similarly influence behavior in conflict situations is yet to be established. Using an economic game experiment, we isolate the effect of group reputation on aggression and conflict from that of individual reputation. We find that group reputation can increase the willingness to inflict costs on others but only when individuals are able to punish their fellow members. Even if internal discipline can sustain their shared reputation, more intimidating groups provide fewer benefits to their members in the short run. Using an agent-based simulation, we show that this might not be the case in the long run. Our findings yield insights into the effects of group reputation on aggression, conflict, and possible consequences for group survival.

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.

To help or punish in the face of unfairness: men and women prefer mutually-beneficial strategies over punishment in a sexual selection context

Consistent with a sexual selection account of cooperation, based on female choice, men, in romantic contexts, in general display mutually-beneficial behaviour and women choose men who do so. This evidence is based on a two-choice-architecture (cooperate or not). Here we extend this to include punishment options using a four-choice-architecture ('punishing a transgressor', 'compensating a victim', 'both punishing and compensating' or 'doing nothing'). Both compensation (a self-serving mutually-beneficial behaviour) and self-serving punishment, are associated with positive mate qualities. We test which is preferred by males and chosen by female undergraduates. We further explore effects of trait empathy and political ideology on these preferences. In a series of three studies using a third-party punishment and compensation (3PPC) game we show (Study One), that romantically-primed undergraduate males, express a preference to either 'compensate' or 'both compensate and punish', and undergraduate women find males who 'compensate' or 'compensate and punish' the most attractive (Studies Two and Three). Compensating men are perceived as compassionate, fair and strong by undergraduate women (Study Three). High trait empathy (Studies One and Three) and a left-wing political ideology (Study Three) are associated with a preference for compensation. Thus, self-serving mutually-beneficial behaviour can be preferred over self-serving punishment as a signal of mate quality in undergraduates. Implications for the evolution of cooperation are discussed with respect to sexual selection.

Evolution of coordinated punishment to enforce cooperation from an unbiased strategy space

The emergence and maintenance of punishment to protect the commons remains an open puzzle in social and biological sciences. Even in societies where pro-social punishing is common, some individuals seek to cheat the system if they see a chance to do so—and public goods are often maintained in spite of cheaters who do not contribute. We present a model accounting for all possible strategies in a public goods game with punishment. While most models of punishment restrict the set of possible behaviours, excluding seemingly paradoxical anti-social strategies from the start, we show that these strategies can play an important role in explaining large-scale cooperation as observed in human societies. We find that coordinated punishment can emerge from individual interactions, but the stability of the associated institutions is limited owing to anti-social and opportunistic behaviour. In particular, coordinated anti-social punishment can undermine cooperation if individuals cannot condition their behaviour on the existence of institutions that punish. Only when we allow for observability and conditional behaviours do anti-social strategies no longer threaten cooperation. This is due to a stable coexistence of a minority supporting pro-social institutions and those who only cooperate if such institutions are in place. This minority of supporters is enough to guarantee substantial cooperation under a wide range of conditions. Our findings resonate with the empirical observation that public goods are resilient to opportunistic cheaters in large groups of unrelated individuals. They also highlight the importance of letting evolution, and not modellers, decide which strategies matter.

Enforcement is central to the evolution of cooperation

Cooperation occurs at all levels of life, from genomes, complex cells and multicellular organisms to societies and mutualisms between species. A major question for evolutionary biology is what these diverse systems have in common. Here, we review the full breadth of cooperative systems and find that they frequently rely on enforcement mechanisms that suppress selfish behaviour. We discuss many examples, including the suppression of transposable elements, uniparental inheritance of mitochondria and plastids, anti-cancer mechanisms, reciprocation and punishment in humans and other vertebrates, policing in eusocial insects and partner choice in mutualisms between species. To address a lack of accompanying theory, we develop a series of evolutionary models that show that the enforcement of cooperation is widely predicted. We argue that enforcement is an underappreciated, and often critical, ingredient for cooperation across all scales of biological organization.

Basal testosterone's relationship with dictator game decision-making depends on cortisol reactivity to acute stress: A dual-hormone perspective on dominant behavior during resource allocation

The dual-hormone hypothesis proposes that testosterone's relationship with status-seeking behavior is moderated by cortisol. However, research testing this hypothesis has focused on basal cortisol; the potential moderating effect of the acute cortisol response to stress has been largely overlooked. The present research investigated the moderating role of cortisol responses to an acute stressor on basal testosterone's link with dominant, status-relevant decision-making. Also, given the multifaceted nature of the response to acute stress, cardiovascular and affective responses to the stressor were examined as alternative moderators of the testosterone-behavior relationship. Participants (N = 112; 56% female) were exposed to a social-evaluative stressor, and their stress responses were measured. Participants subsequently engaged in a one-shot dictator game, wherein they were asked to split money ($10) with a confederate counterpart. The amount of money participants decided to keep for themselves was treated as a metric of dominant status-seeking behavior. For individuals who demonstrated lower cortisol responses to the stressor, basal testosterone was positively associated with more dominant behavior (i.e., keeping more money for oneself), but for those who showed higher cortisol responses, the testosterone-behavior relationship was suppressed. Moreover, other aspects of the stress response (i.e., cardiovascular and affective responses) did not moderate the relationship between basal testosterone and dictator game behavior. These results provide unique support for the dual-hormone hypothesis using markers of stress-induced cortisol change. The findings also suggest that the antagonistic effects of stress on testosterone's role in motivating status-relevant behavior may be specific to cortisol's role in the acute stress response.