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Prominent evolutionary theories of morality maintain that the adaptations that underlie moral judgment and behavior function, at least in part, to deliver benefits (or prevent harm) to others. These explanations are based on the theories of kin selection and reciprocal altruism, and they predict that moral systems are designed to maximize Hamiltonian inclusive fitness. In sharp contrast, however, moral judgment often appears Kantian and rule-based. To reconcile this apparent discrepancy, some theorists have claimed that Kantian moral rules result from mechanisms that implement simple heuristics for maximizing welfare. To test this idea, we conducted a set of studies in which subjects (N=1290) decided whether they would kill one person to save five others, varying the relationship of the subject with the others involved (strangers, friends, brothers). Are participants more likely to observe the Kantian rule against killing in decisions about brothers and friends, rather than strangers? We found the reverse. Subjects reported greater willingness to kill a brother or friend than a stranger (in order to save five others of the same type). These results suggest that the rule-based structure of moral cognition is not explained by kin selection, reciprocity, or other altruism theories.

Humans spend tremendous amounts of time producing and consuming narratives about people who have never existed doing things that have never been done. These narratives often concern actions that would, in the real world, have very large fitness consequences, such as the forming and dissolving of sexual relationships and committing acts of serious interpersonal violence. Country music lyrics capture listeners' attention, in part, with narratives depicting social interactions with big evolutionary stakes.

Pinocchio is alone on a lifeless planet. Is it possible for Pinocchio to do something morally wrong? If he shouts falsehoods into empty space, will his nose grow longer? Will the moral lessons he l...

Psychopathy represents a unique set of personality traits including deceitfulness, lack of empathy and guilt, impulsiveness, and antisocial behavior. Most often in the literature, psychopathy is described as pathology — a disorder that has been linked to a variety of biological deficits and environmental risk factors. However, from an evolutionary perspective, psychopathy, while it could be a disorder, has been construed in the context of an adaptive strategy. In this article we will examine the strengths and weaknesses of two models suggesting that psychopathy is an adaptive strategy, and one model suggesting that it is a form of pathology resulting from accumulated mutations. Overall, we do not find that there is strong enough evidence to draw firm conclusions about one theory over another, but we highlight some areas where future research may be able to shed light on the issue.

Moral judgment involves much more than computations of the expected consequences of behavior. A prime example of the complexity of moral thinking is the frequently replicated finding that violations by omission are judged less morally wrong than violations by commission, holding intentions constant. Here we test a novel hypothesis: Omissions are judged less harshly because they produce little material evidence of wrongdoing. Evidence is crucial because moral accusations are potentially very costly unless supported by others. In our experiments, the omission effect was eliminated when physical evidence showed that an omission was chosen. Perpetrators who “opted out” by pressing a button that would clearly have no causal effects on the victim, rather than rescuing them, were judged as harshly as perpetrators who directly caused death. These results show that, to reduce condemnation, omissions must not only be noncausal, they must also leave little or no material evidence that a choice was made. © 2011 Elsevier Inc. All rights reserved.

Humans, unlike most other species, show intense interest in the activities of conspecifics, even when the activities in question pose no obvious fitness threat or opportunity. Here, we investigate one content domain in which people show substantial interest, the use of drugs for non-medical purposes. Drawing from two subject populations—one undergraduate and one Internet-based—we look at the relationships among (i) abstract political commitments; (ii) attitudes about sexuality; and (iii) views surrounding recreational drugs. Whereas some theories suggest that drug views are best understood as the result of abstract political ideology, we suggest that these views can be better understood in the context of reproductive strategy. We show that, as predicted by a strategic construal, drug attitudes are best predicted by sexual items rather than abstract political commitments and, further, that the relationship between factors such as political ideology and drugs, while positive, are reduced to zero or nearly zero when items assessing sexuality are controlled for. We conclude that considering morality from the standpoint of strategic interests is a potentially useful way to understand why humans care about third party behaviour.

Evolutionary theories of morality, beginning with Darwin, have focused on explanations for altruism. More generally, these accounts have concentrated on conscience (self-regulatory mechanisms) to the neglect of condemnation (mechanisms for punishing others). As a result, few theoretical tools are available for understanding the rapidly accumulating data surrounding third-party judgment and punishment. Here we consider the strategic interactions among actors, victims, and third-parties to help illuminate condemnation. We argue that basic differences between the adaptive problems faced by actors and third-parties indicate that actor conscience and third-party condemnation are likely performed by different cognitive mechanisms. Further, we argue that current theories of conscience do not easily explain its experimentally demonstrated insensitivity to consequences. However, these results might be explicable if conscience functions, in part, as a defense system for avoiding third-party punishment. If conscience serves defensive functions, then its computational structure should be closely tailored to the details of condemnation mechanisms. This possibility underscores the need for a better understanding of condemnation, which is important not only in itself but also for explaining the nature of conscience. We outline three evolutionary mysteries of condemnation that require further attention: third-party judgment, moralistic punishment, and moral impartiality.

Kinship is a fundamental component of human sociality influencing a range of behaviors including altruism, aggression, and mating. Though a central focus in psychology’s neighboring disciplines, kinship has been largely neglected within psychology. An illustrative example ‐ and the focus here ‐ is research on social categorization. Researchers investigating the categories into which our mind carves the social world have focused primarily on sex, age, and race. Here we present evidence that kinship belongs in the family of fundamental social categories. In a series of experiments using a memory confusion paradigm, we show that participants implicitly encode the kinship relations of social targets and do so to the same extent as sex and age, two previously established robust dimensions of social categorization. The functional framework applied here provides useful guide-rails for investigating how the human mind naturally parses the social world, and, more broadly, helps unite psychology with its neighboring disciplines in which kinship is treated as an important conceptual tool. Copyright # 2008 John Wiley & Sons, Ltd.

Forensic science error rates are needlessly high. Applying the perspective of veritistic social epistemology to forensic science could produce new institutional designs that would lower forensic error rates. We make such an application through experiments in the laboratory with human subjects. Redundancy is the key to error prevention, discovery, and elimination. In the “monopoly epistemics” characterizing forensics today, one privileged actor is asked to identify the truth. In “democratic epistemics,” several independent parties are asked. In an experiment contrasting them, democratic epistemics reduced the rate at which biased observers obscured the truth by two-thirds. These results highlight, first, the potential of “epistemic systems design,” which employs the techniques of economic systems design to address issues of veracity rather than efficiency, and second, the value of “experimental epistemology,” which employs experimental techniques in the study of science.

Questions remain about the details of the reciprocal strategies people use in the context of group cooperation. Here we report an experiment in which participants in public goods games could access information about the lowest, median, or highest contribution to the public good before making their own contribution decisions. Results suggest that people have clear preferences for particular pieces of information and that information preferences vary systematically across individuals as a function of their contribution strategies. Specifically, participants playing reciprocal strategies sought information about the median contribution, free riders preferred to view the highest contribution, and altruists had inconsistent preferences. By including a treatment in which people could pay to see information rather than obtaining it for free, we found that people were willing to incur costs to acquire information, particularly those using a reciprocal strategy. Further, adding a cost to view information decreased aggregate contributions, possibly because the motivation to induce others' reciprocal contributions diminished under these conditions. Copyright © 2007 John Wiley & Sons, Ltd.

Because researchers are making increasing use of data gleaned from Internet dating sites, it is important to know if the preferences people specify in Internet advertisements predict the choices that they actually make. HurryDate, a commercial speed-dating firm, collected data from over 10,000 people in their 20s, 30s, and 40s who participated in speed-dating events in cities across the United States. The present analysis compared these speed daters’ advertised preferences with their decisions to attend particular events and their choices of potential partners at the events they attended. Findings indicated that speed daters’ advertisements reflect frequently replicated sex differences and assortative patterns and that these advertised mate preferences predicted their decisions to attend particular events. Advertised preferences did not, in contrast, substantially predict decisions within events. These results support the conclusion that advertised preferences predict behavior in the mating domain in some contexts but not others.

We investigate cooperation using an incremental investment game in which the first-mover has the ability to make small, but increasing incremental investments in their counterpart. Our experiment is designed to test whether establishing trust in small increments is more effective than alternatives, including a one-shot investment game, a decrease only condition where the amount the first-mover sends to the second-mover must be less than the amount previously sent, and an unrestricted condition where the first-mover is not restricted by the amount previously sent. Although results were mixed, broadly, iteration affords greater cooperation than one-shot games and, when given the choice, participants seem to prefer to build trust gradually. Implications for institutional design are discussed.

A modular view of the mind implies that there is no unitary “self” and that the mind consists of a set of informationally encapsulated systems, many of which have functions associated with navigating an inherently ambiguous and competitive social world. It is proposed that there are a set of cognitive mechanisms—a social cognitive interface (SCI)—designed for strategic manipulation of others' representations of one's traits, abilities, and prospects. Although constrained by plausibility, these mechanisms are not necessarily designed to maximize accuracy or to maintain consistency with other encapsulated representational systems. The modular view provides a useful framework for talking about multiple phenomena previously discussed under the rubric of the self.

Punishment has been proposed as being central to two distinctively human phenomena: cooperation in groups and morality. Here we investigate moralistic punishment, a behavior designed to inflict costs on another individual in response to a perceived moral violation. There is currently no consensus on which evolutionary model best accounts for this phenomenon in humans. Models that turn on individuals' cultivating reputations as moralistic punishers clearly predict that psychological systems should be designed to increase punishment in response to information that one's decisions to punish will be known by others. We report two experiments in which we induce participants to commit moral violations and then present third parties with the opportunity to pay to punish wrongdoers. Varying conditions of anonymity, we find that the presence of an audience—even if only the experimenter—causes an increase in moralistic punishment.

Like many topics of psychological research, the explanation for friendship is at once intuitive and difficult to address empirically. These difficulties worsen when one seeks, as we do, to go beyond “obvious” explanations (“humans are social creatures”) to ask deeper questions, such as “What is the evolved function of human friendship?” In recent years, however, a new window into human behavior has opened as a growing fraction of people’s social activity has moved online, leaving a wealth of digital traces behind. One example is a feature of the MySpace social network that allows millions of users to rank their “Top Friends.” In this study, we collected over 10 million people’s friendship decisions from MySpace to test predictions made by hypotheses about human friendship. We found particular support for the alliance hypothesis, which holds that human friendship is caused by cognitive systems that function to create alliances for potential disputes. Because an ally’s support can be undermined by a stronger outside relationship, the alliance model predicts that people will prefer partners who rank them above other friends. Consistent with the alliance model, we found that an individual’s choice of best friend in MySpace is strongly predicted by how partners rank that individual.

Individual and organizational actors enter into a large number of relationships that include benefiting others without ensuring the equality of reciprocal benefits. We suggest that actors have evolved mechanisms that guide them in the choice of exchange partners, even without conscious calculation or bookkeeping of gain and loss. One such mechanism directs actors to membership in clusters, which are homogenous groups of actors densely connected among themselves and only loosely connected to other groups. We suggest that clusters offer network externalities, which are not possible in sparse networks, thus conferring cascading benefits on the actors contained in those clusters. Using this logic, one can understand the omnipresence of clustering in social networks of individuals and firms. We review the benefits and challenges associated with clustering and use the logic of cascading benefits to derive empirical predictions. Copyright © 2006 John Wiley & Sons, Ltd.

Human beings exhibit substantial interpersonal trust—even with strangers. The neuroactive hormone oxytocin facilitates social recognition in animals, and we examine if oxytocin is related to trustworthiness between humans. This paper reports the results of an experiment to test this hypothesis, where trust and trustworthiness are measured using the sequential anonymous ‘‘trust game’’ with monetary payoffs. We find that oxytocin levels are higher in subjects who receive a monetary transfer that reflects an intention of trust relative to an unintentional monetary transfer of the same amount. In addition, higher oxytocin levels are associated with trustworthy behavior (the reciprocation of trust). Absent intentionality, both the oxytocin and behavioral responses are extinguished. We conclude that perceptions of intentions of trust affect levels of circulating oxytocin.

To investigate the choices that people make in dating partners, we analyzed data provided by HurryDate, a commercial dating service aimed at adult singles living in major metropolitan areas. Here, we report data from 10,526 participants in HurryDate sessions, in which roughly 25 men and 25 women interacted with each other for three minutes and subsequently indicated which of the people they met they would be interested in having contact with in the future. We had general survey information collected by HurryDate for all the participants and additional survey information for 2,650 participants. Our main findings are that (1) HurryDate interactions are driven primarily by generally agreed-upon mate values and less by niche-based or assortative patterns, (2) the agreed-upon mate values for both men and women derive almost exclusively from physically observable attributes like attractiveness, BMI, height, and age and are not substantially related to harder-to-observe attributes such as education, religion, sociosexuality, having children, or desiring future children, and (3) small positive assortative trends arise in the areas of race and height. Our results provide rare behavioral evidence regarding people’s preferences in dating partners.

Trust is an essential component of transactions that occur over time. The amount of trust accorded to others is typically conditioned on multiple factors, including knowledge of the other party, the history of interactions, and the context of exchange. Determining who to trust and who to distrust is especially important in modern societies with largely impersonal exchange (Vernon L. Smith, 2003). In fact, trust is among the strongest predictors of whether a country will successfully develop: poor countries are by-and-large low-trust countries. This occurs because low trust inhibits investment and thereby the creation of wealth (Zak and Stephen Knack, 2001). Unfortunately, subjects in laboratory settings are unable to articulate clearly why they decide to trust or distrust a trading partner. In order to discover why human beings trust or distrust others, economists have begun obtaining physiologic measurements during trust experiments (Zak, 2005). This new transdisciplinary field is called neuroeconomics (Kevin McCabe et al., 2001; Zak, 2004; Colin F. Camerer et al., 2005). Recently, Zak et al. (2004, 2005) reported that people who received a signal of trust in an experimental game had higher levels of the neuroactive hormone oxytocin (OT) than those who received similar amounts of money absent a trust signal. In addition, higher OT levels were associated with an increased reciprocation of trust (i.e., greater trustworthiness). Animal models have shown that OT promotes prosocial behaviors by producing a pleasurable sensation. Because humans are highly social creatures, there may be both positive and negative physiologic controls over social behaviors, as there are for other important behaviors. For example, the hormones ghrelin and leptin are primary regulators of nourishment, promoting food intake and signaling satiety to terminate food consumption, respectively. This paper provides evidence for a hormone that is associated with a negative social interaction, distrust. We test two hypotheses

This is the first report that endogenous oxytocin in humans is related to social behaviors, which is consistent with a large animal literature. Subjects are put into a social dilemma in which absent communication, cooperative behavior can benefit both parties randomly assigned to a dyad. The dilemma arises because one participant must make a monetary sacrifice to signal the degree of trust in the other before the other's behavioral response is known. We show that receipt of a signal of trust is associated with a higher level of peripheral oxytocin than that in subjects receiving a random monetary transfer of the same average amount. Oxytocin levels were also related to trustworthy behavior (sharing a greater proportion of the monetary gains). We conclude that oxytocin may be part of the human physiology that motivates cooperation.

Contemplation of death increases support of ingroup ideologies, a result explained by proponents of terror management theory (TMT) as an attempt to buffer existential anxiety. While TMT claims that only death-salient stimuli yield such effects, an evolutionary perspective suggests that increased intergroup bias may occur in response to a wide variety of situations that, in ancestral environments, posed adaptive problems for which marshaling social support was a reliably adaptive response. Four experiments from two cultures produced results consistent with this latter perspective but contrary to TMT. Studies 1 and 2 demonstrated that, among UCLA undergraduates, participants asked to contemplate aversive scenarios unrelated to death displayed increased support of ingroup ideology. Studies 3 and 4 replicated elements of these results, exploring the moderating effects of self-esteem and collectivism on intergroup bias in two Costa Rican samples. These results indicate that worldview defense effects occur even when death is not salient.

Using the real-time protocol of play—a relatively new experimental mechanism in which the order of play and timing of decisions are determined endogenously—we investigate voluntary contributions to the provision of pure public goods. We consider the case where the good is binary, players are asymmetric, communication is prohibited, and all-or-none contributions to the public good can be withdrawn at any time during the round of play. Our results: (1) support an equilibrium in which contributors maximize the sum of their own payoffs; (2) show considerably higher levels of contribution than under the more commonly used simultaneous protocol of play; and (3) exhibit no decrease in level of contribution across multiple iterations of the stage game. On comparing our results to those of Goren et al. (2003), we conclude that modifying the mechanism so that contributions once made cannot be revoked yields significantly higher levels of contribution over the course of the game. Copyright © 2003 John Wiley & Sons, Ltd.

UNTIL RECENTLY, EXPERIMENTS ON PERSON PERCEPTION HAD LED TO TWO UNWELCOME CONCLUSIONS: (1) people encode the race of each individual they encounter, and (2) race encoding is caused by computational mechanisms whose operation is automatic and mandatory. Evolutionary analyses rule out the hypothesis that the brain mechanisms that cause race encoding evolved for that purpose. Consequently, race encoding must be a byproduct of mechanisms that evolved for some alternative function. But which one? Race is not encoded as a byproduct of domain-general perceptual processes. Two families of byproduct hypotheses remain: one invokes inferential machinery designed for tracking coalitional alliances, the other machinery designed for reasoning about natural kinds. Recent experiments show that manipulating coalitional variables can dramatically decrease the extent to which race is noticed and remembered.

Whereas most experimental studies of public goods provisioning require that all players make their decisions simultaneously, in most organizational settings contribution decisions are made in real time. To account for this aspect of the decision process, we introduce a real-time protocol of play in which, at any point in time, players can either withhold or contribute their entire endowment to a step-level public good. Once contributed, the individual endowments—that in the present experiment differ from one group member to another—cannot be withdrawn. Our results show that contribution levels under the real-time protocol with irrevocable commitments significantly exceed those observed in previous studies under the more common simultaneous protocol of play, thereby considerably reducing social loafing (free riding). Consistent with our equilibrium analysis, over multiple iterations of the game play converges to an equilibrium set of players who maximize the sum of their individual benefit-to-contribution ratios.

There has been substantial recent interest in determining why there is cooperation in public goods experiments even in environments that provide all subjects with the incentive to free ride (see e.g., John O. Ledyard, 1995). Theories used to explain such cooperation generally posit either that subjects are “confused” in the sense that they make errors or do not understand the game’s incentives, or that subjects contribute due to social factors such as altruism and reciprocity. Although several authors have pointed out the importance of distinguishing between these alternatives, the roles that confusion and social motives play in determining public contributions remain poorly understood. This paper provides new evidence on the way that confusion and social motives determine contributions in public goods games by reporting data from experiments that use a new design with the Voluntary Contribution Mechanism (VCM). Two important and often replicated findings in the experimental public goods literature are (1) that subjects’ public contributions are much greater than predicted by standard economic theories of free-riding and (2) that these contributions decay over the course of multiple-round games (see e.g., Douglas D. Davis and Charles A. Holt, 1993). Models that employ social factors to explain cooperation and its decay usually assume that subjects are motivated by altruism, reciprocity, or fairness (see e.g., Andreoni, 1990; Rachel T. A. Croson, 1998; Anna Gunthorsdottir et al., 2001). It has been argued, for instance, that subjects make contributions in order to elicit like contributions from reciprocators in subsequent rounds and that decay in public contributions might result from “frustrated attempts at kindness” (Andreoni, 1995 p. 892). Specifically, because there is generally heterogeneity in the willingness to contribute to the public good, initially cooperative players will likely reduce their public contributions after being grouped with relatively low contributors. In contrast, confusion theories postulate that players make public contributions either in error or because they do not understand how to pursue their self-interest. These theories argue that high initial contributions decay primarily because subjects gradually come to understand the game’s incentives. Recently, Andreoni (1995) conducted an interesting series of experiments in the first and, to our knowledge, only effort to discriminate between these competing theories of cooperative play. He provides two reasons that doing this is important. The first is that knowing the relative importance of confusion and social motives in generating cooperative decay can provide a useful guide to future research. While Andreoni argues that such knowledge could be used to inform research on learning models, note also that to the extent confusion is found to be important, shedding light on the way different sorts of instructions affect confusion could help to improve pedagogics. A second compelling reason Andreoni gives is that the outcomes of experiments designed to test theories of social giving are difficult to interpret if confusion is a primary source of cooperation. * Houser: Department of Economics and Economic Science Laboratory, University of Arizona, Tucson, AZ 85721; Kurzban: Economic Science Laboratory, University of Arizona, Tucson, AZ 85721. We thank Mark Isaac, Kevin McCabe, David Porter, Vernon Smith, Bart Wilson, seminar participants at the University of Arizona, and two anonymous referees for valuable comments on this research. The authors gratefully acknowledge the research support of fellowships from the International Foundation for Research in Experimental Economics. This research was supported by Russell Sage Foundation Grant No. 98-00-01. The authors are responsible for any errors. 1 See, for example, James Andreoni (1995), Martin Sefton and Richard Steinberg (1996), and Thomas R. Palfrey and Jeffrey E. Prisbrey (1997). 2 This paper focuses on only standard linear games in which to contribute zero to the public good is the dominant strategy.

Substantial evidence comparing men’s perceptions of women’s sexual intentions with women’s own reports of their sexual intentions has shown a systematic pattern of results that has been interpreted as support for the idea that men overestimate women’s true sexual intentions. However, because women’s true sexual intentions cannot be directly measured, an alternative interpretation of the existing data is that women understate their sexual intentions and that men’s assessments of women’s intentions are generally accurate. In three studies, we (a) replicated the typical sex difference in sexual-intent ratings, (b) showed that men maintain their ratings of women’s sexual intentions even when incentivized to tell the truth, and (c) showed that women believe that other women are understating their sexual intentions in self-report measures. Taken together, these results imply that men might be accurate in perceiving and reporting women’s sexual intentions and that men might be managing errors through biased behavior rather than biased beliefs.

According to signaling theory and a large body of supporting evidence, males across many taxa produce courtship signals that honestly advertise their quality. The cost of producing or performing these signals maintains signal honesty, such that females are typically able to choose the best males by selecting those that produce the loudest, brightest, longest, or otherwise highest-intensity signals, using signal strength as a measure of quality. Set against this background, human flirting behavior, characterized by its frequent subtlety or covertness, is mysterious. Here we propose that the explanation for subtle and ambiguous signals in human courtship lies in socially imposed costs that (a) vary with social context and (b) are amplified by the unusual ways in which language makes all interactions potentially public. Flirting is a class of courtship signaling that conveys the signaler's intentions and desirability to the intended receiver while minimizing the costs that would accompany an overt courtship attempt. This proposal explains humans' taxonomically unusual courtship displays and generates a number of novel predictions for both humans and non-human social animals. Individuals who are courting should vary the intensity of their signals to suit the level of risk attached to the particular social configuration, and receivers may assess this flexible matching of signal to context as an indicator of the signaler's broader behavioral flexibility and social intelligence.

Humans are an intensely social species, frequently performing costly behaviors that benefit others. Efforts to solve the evolutionary puzzle of altruism have a lengthy history, and recent years have seen many important advances across a range of disciplines. Here we bring together this interdisciplinary body of research and review the main theories that have been proposed to explain human prosociality, with an emphasis on kinship, reciprocity, indirect reciprocity, punishment, and morality. We highlight recent methodological advances that are stimulating research and point to some areas that either remain controversial or merit more attention.

Allowing players in public goods games to make small incremental commitments to contributing to the good might facilitate cooperation because it helps to prevent players from being “free ridden,” contributing more to the public good than other group members. Two experiments using a real-time version of the voluntary contribution mechanism were conducted to investigate the hypothesis that players are generally willing to contribute public goods conditional on beliefs that others are doing so at similar levels. Experiment 1 provided evidence that affording a strategy of commitment can increase the production of public goods. Experiment 2 provided evidence that most players are willing to contribute to the public good at a level at or slightly above the contribution of the lowest contributor in the group. Both experiments point to inequity aversion as an important element of play in public goods games.

Research using the public goods game to examine behaviour in the context of social dilemmas has repeatedly shown substantial individual differences in patterns of contributions to the public good. We present here a new method specifically designed to capture this heterogeneity in play and classify participants into broad categories or types. Players in groups of four made initial, simultaneous contributions to the public good. Subsequently, players were sequentially told the current aggregate contribution to the public good and allowed to change their decision based on this information. The game continued, with players updating their contribution decision until the game ended at an unknown point. By looking at the relationship between players' contributions and the aggregate value they observed, we were able to cleanly classify 82% of our players into three types: strong free riders (28%), conditional cooperators of reciprocators (29%), and strong cooperators (25%). We also found that scores on some of the personality dimensions we investigated (self‐monitoring, self‐esteem, neuroticism, and conscientiousness) correlated with player type. Finally, males were found to be more likely to be strong cooperators than females. Copyright © 2001 John Wiley & Sons, Ltd.

A reconceptualization of stigma is presented that changes the emphasis from the devaluation of an individual's identity to the process by which individuals who satisfy certain criteria come to be excluded from various kinds of social interactions. The authors propose that phenomena currently placed under the general rubric of stigma involve a set of distinct psychological systems designed by natural selection to solve specific problems associated with sociality. In particular, the authors suggest that human beings possess cognitive adaptations designed to cause them to avoid poor social exchange partners, join cooperative groups (for purposes of between-group competition and exploitation), and avoid contact with those who are differentially likely to carry communicable pathogens. The evolutionary view contributes to the current conceptualization of stigma by providing an account of the ultimate function of stigmatization and helping to explain its consensual nature.

An experiment was conducted to test the hypothesis that cooperation in a social dilemma context could be facilitated by inducing participants to emit “social psychophysical” cues, information in the perceptual array that affords meaningful and consequential social inferences. In particular, participants were asked to engage in mutual eye gaze, to touch one another gently, to communicate in a virtual chat room, or to tap out rhythms in synchrony. All but the last of these manipulations increased contributions to a public good in all-male but not all-female groups. These results suggest the inference systems that are engaged when individuals make decisions about whether or not to cooperate in a group context are responsive to relatively low level nonverbal behavioral cues.

Why does performing certain tasks cause the aversive experience of mental effort and concomitant deterioration in task performance? One explanation posits a physical resource that is depleted over time. We propose an alternative explanation that centers on mental representations of the costs and benefits associated with task performance. Specifically, certain computational mechanisms, especially those associated with executive function, can be deployed for only a limited number of simultaneous tasks at any given moment. Consequently, the deployment of these computational mechanisms carries an opportunity cost – that is, the next-best use to which these systems might be put. We argue that the phenomenology of effort can be understood as the felt output of these cost/benefit computations. In turn, the subjective experience of effort motivates reduced deployment of these computational mechanisms in the service of the present task. These opportunity cost representations, then, together with other cost/benefit calculations, determine effort expended and, everything else equal, result in performance reductions. In making our case for this position, we review alternative explanations for both the phenomenology of effort associated with these tasks and for performance reductions over time. Likewise, we review the broad range of relevant empirical results from across sub-disciplines, especially psychology and neuroscience. We hope that our proposal will help to build links among the diverse fields that have been addressing similar questions from different perspectives, and we emphasize ways in which alternative models might be empirically distinguished.

Psychopathy research is plagued by an enigma: Psychopaths reliably act immorally, but they also accurately report whether an action is morally wrong. The current study revealed that cooperative suppressor effects and conflicting subsets of personality traits within the construct of psychopathy might help explain this conundrum. Among a sample of adult male offenders (n = 100) who ranked deserved punishment of crimes, Psychopathy Checklist-Revised (PCL-R) total scores were not linearly correlated with deserved punishment task performance. However, these null results masked significant opposing associations between task performance and factors of psychopathy: the PCL-R Interpersonal/Affective (i.e. manipulative and callous) factor was positively associated with task performance, while the PCL-R Social Deviance (i.e. impulsive and antisocial) factor was simultaneously negatively associated with task performance. Importantly, these relationships were qualified by a significant interaction where the Interpersonal/Affective traits were positively associated with task performance when Social Deviance traits were high, but Social Deviance traits were negatively associated with task performance when Interpersonal/Affective traits were low. This interaction helped reveal a significant non-linear relationship between PCL-R total scores and task performance such that individuals with very low or very high PCL-R total scores performed better than those with middle-range PCL-R total scores. These results may explain the enigma of why individuals with very high psychopathic traits, but not other groups of anti-social individuals, usually have normal moral judgment in laboratory settings, but still behave immorally, especially in contexts where Social Deviance traits have strong influence.