A moral trade-off system produces intuitive judgments that are rational and coherent and strike a balance between conflicting moral values.

How does the mind make moral judgments when the only way to satisfy one moral value is to neglect another? Moral dilemmas posed a recurrent adaptive problem for ancestral hominins, whose cooperative social life created multiple responsibilities to others. For many dilemmas, striking a balance between two conflicting values (a compromise judgment) would have promoted fitness better than neglecting one value to fully satisfy the other (an extreme judgment). We propose that natural selection favored the evolution of a cognitive system designed for making trade-offs between conflicting moral values. Its nonconscious computations respond to dilemmas by constructing "rightness functions": temporary representations specific to the situation at hand. A rightness function represents, in compact form, an ordering of all the solutions that the mind can conceive of (whether feasible or not) in terms of moral rightness. An optimizing algorithm selects, among the feasible solutions, one with the highest level of rightness. The moral trade-off system hypothesis makes various novel predictions: People make compromise judgments, judgments respond to incentives, judgments respect the axioms of rational choice, and judgments respond coherently to morally relevant variables (such as willingness, fairness, and reciprocity). We successfully tested these predictions using a new trolley-like dilemma. This dilemma has two original features: It admits both extreme and compromise judgments, and it allows incentives-in this case, the human cost of saving lives-to be varied systematically. No other existing model predicts the experimental results, which contradict an influential dual-process model.

Invariances in the architecture of pride across small-scale societies.

Becoming valuable to fellow group members so that one would attract assistance in times of need is a major adaptive problem. To solve it, the individual needs a predictive map of the degree to which others value different acts so that, in choosing how to act, the payoff arising from others' valuation of a potential action (e.g., showing bandmates that one is a skilled forager by pursuing a hard-to-acquire prey item) can be added to the direct payoff of the action (e.g., gaining the nutrients of the prey captured). The pride system seems to incorporate all of the elements necessary to solve this adaptive problem. Importantly, data from western(-ized), educated, industrialized, rich, and democratic (WEIRD) societies indicate close quantitative correspondences between pride and the valuations of audiences. Do those results generalize beyond industrial mass societies? To find out, we conducted an experiment among 567 participants in 10 small-scale societies scattered across Central and South America, Africa, and Asia: (i) Bosawás Reserve, Nicaragua; (ii) Cotopaxi, Ecuador; (iii) Drâa-Tafilalet, Morocco; (iv) Enugu, Nigeria; (v) Le Morne, Mauritius; (vi) La Gaulette, Mauritius; (vii) Tuva, Russia; (viii) Shaanxi and Henan, China; (ix) farming communities in Japan; and (x) fishing communities in Japan. Despite widely varying languages, cultures, and subsistence modes, pride in each community closely tracked the valuation of audiences locally (mean r = +0.66) and even across communities (mean r = +0.29). This suggests that the pride system not only develops the same functional architecture everywhere but also operates with a substantial degree of universality in its content.

Cross-cultural invariances in the architecture of shame.

Human foragers are obligately group-living, and their high dependence on mutual aid is believed to have characterized our species' social evolution. It was therefore a central adaptive problem for our ancestors to avoid damaging the willingness of other group members to render them assistance. Cognitively, this requires a predictive map of the degree to which others would devalue the individual based on each of various possible acts. With such a map, an individual can avoid socially costly behaviors by anticipating how much audience devaluation a potential action (e.g., stealing) would cause and weigh this against the action's direct payoff (e.g., acquiring). The shame system manifests all of the functional properties required to solve this adaptive problem, with the aversive intensity of shame encoding the social cost. Previous data from three Western(ized) societies indicated that the shame evoked when the individual anticipates committing various acts closely tracks the magnitude of devaluation expressed by audiences in response to those acts. Here we report data supporting the broader claim that shame is a basic part of human biology. We conducted an experiment among 899 participants in 15 small-scale communities scattered around the world. Despite widely varying languages, cultures, and subsistence modes, shame in each community closely tracked the devaluation of local audiences (mean r = +0.84). The fact that the same pattern is encountered in such mutually remote communities suggests that shame's match to audience devaluation is a design feature crafted by selection and not a product of cultural contact or convergent cultural evolution.

Support for redistribution is shaped by compassion, envy, and self-interest, but not a taste for fairness.

Why do people support economic redistribution? Hypotheses include inequity aversion, a moral sense that inequality is intrinsically unfair, and cultural explanations such as exposure to and assimilation of culturally transmitted ideologies. However, humans have been interacting with worse-off and better-off individuals over evolutionary time, and our motivational systems may have been naturally selected to navigate the opportunities and challenges posed by such recurrent interactions. We hypothesize that modern redistribution is perceived as an ancestral scene involving three notional players: the needy other, the better-off other, and the actor herself. We explore how three motivational systems-compassion, self-interest, and envy-guide responses to the needy other and the better-off other, and how they pattern responses to redistribution. Data from the United States, the United Kingdom, India, and Israel support this model. Endorsement of redistribution is independently predicted by dispositional compassion, dispositional envy, and the expectation of personal gain from redistribution. By contrast, a taste for fairness, in the sense of (i) universality in the application of laws and standards, or (ii) low variance in group-level payoffs, fails to predict attitudes about redistribution.

Cross-cultural regularities in the cognitive architecture of pride.

Pride occurs in every known culture, appears early in development, is reliably triggered by achievements and formidability, and causes a characteristic display that is recognized everywhere. Here, we evaluate the theory that pride evolved to guide decisions relevant to pursuing actions that enhance valuation and respect for a person in the minds of others. By hypothesis, pride is a neurocomputational program tailored by selection to orchestrate cognition and behavior in the service of: (i) motivating the cost-effective pursuit of courses of action that would increase others' valuations and respect of the individual, (ii) motivating the advertisement of acts or characteristics whose recognition by others would lead them to enhance their evaluations of the individual, and (iii) mobilizing the individual to take advantage of the resulting enhanced social landscape. To modulate how much to invest in actions that might lead to enhanced evaluations by others, the pride system must forecast the magnitude of the evaluations the action would evoke in the audience and calibrate its activation proportionally. We tested this prediction in 16 countries across 4 continents (n = 2,085), for 25 acts and traits. As predicted, the pride intensity for a given act or trait closely tracks the valuations of audiences, local (mean r = +0.82) and foreign (mean r = +0.75). This relationship is specific to pride and does not generalize to other positive emotions that coactivate with pride but lack its audience-recalibrating function.

Shame closely tracks the threat of devaluation by others, even across cultures.

We test the theory that shame evolved as a defense against being devalued by others. By hypothesis, shame is a neurocomputational program tailored by selection to orchestrate cognition, motivation, physiology, and behavior in the service of: (i) deterring the individual from making choices where the prospective costs of devaluation exceed the benefits, (ii) preventing negative information about the self from reaching others, and (iii) minimizing the adverse effects of devaluation when it occurs. Because the unnecessary activation of a defense is costly, the shame system should estimate the magnitude of the devaluative threat and use those estimates to cost-effectively calibrate its activation: Traits or actions that elicit more negative evaluations from others should elicit more shame. As predicted, shame closely tracks the threat of devaluation in the United States (r = .69), India (r = .79), and Israel (r = .67). Moreover, shame in each country strongly tracks devaluation in the others, suggesting that shame and devaluation are informed by a common species-wide logic of social valuation. The shame-devaluation link is also specific: Sadness and anxiety-emotions that coactivate with shame-fail to track devaluation. To our knowledge, this constitutes the first empirical demonstration of a close, specific match between shame and devaluation within and across cultures.

Inclusive fitness theory and eusociality.

Arising from M. A. Nowak, C. E. Tarnita & E. O. Wilson 466, 1057-1062 (2010); Nowak et al. reply. Nowak et al. argue that inclusive fitness theory has been of little value in explaining the natural world, and that it has led to negligible progress in explaining the evolution of eusociality. However, we believe that their arguments are based upon a misunderstanding of evolutionary theory and a misrepresentation of the empirical literature. We will focus our comments on three general issues.

Looking Under the Hood of Third-Party Punishment Reveals Design for Personal Benefit.

Third-party intervention, such as when a crowd stops a mugger, is common. Yet it seems irrational because it has real costs but may provide no personal benefits. In a laboratory analogue, the third-party-punishment game, third parties ("punishers") will often spend real money to anonymously punish bad behavior directed at other people. A common explanation is that third-party punishment exists to maintain a cooperative society. We tested a different explanation: Third-party punishment results from a deterrence psychology for defending personal interests. Because humans evolved in small-scale, face-to-face social worlds, the mind infers that mistreatment of a third party predicts later mistreatment of oneself. We showed that when punishers do not have information about how they personally will be treated, they infer that mistreatment of other people predicts mistreatment of themselves, and these inferences predict punishment. But when information about personal mistreatment is available, it drives punishment. This suggests that humans' punitive psychology evolved to defend personal interests.

Human cooperation shows the distinctive signatures of adaptations to small-scale social life.

The properties of individual carbon atoms allow them to chain into complex molecules of immense length. They are not limited to structures involving only a few atoms. The design features of our evolved neural adaptations appear similarly extensible. Individuals with forager brains can link themselves together into unprecedentedly large cooperative structures without the need for large group-beneficial modifications to evolved human design. Roles need only be intelligible to our social program logic, and judged better than alternatives.

Regulatory adaptations for delivering information: The case of confession.

Prior to, or concurrent with, the encoding of concepts into speech, the individual faces decisions about whether, what, when, how, and with whom to communicate. Compared to the existing wealth of linguistic knowledge however, we know little of the mechanisms that govern the delivery and accrual of information. Here we focus on a fundamental issue of communication: The decision whether to deliver information. Specifically, we study spontaneous confession to a victim. Given the costs of social devaluation, offenders are hypothesized to refrain from confessing unless the expected benefits of confession (e.g. enabling the victim to remedially modify their course of action) outweigh its marginal costs-the victim's reaction, discounted by the likelihood that information about the offense has not leaked. The logic of welfare tradeoffs indicates that the victim's reaction will be less severe and, therefore, less costly to the offender, with decreases in the cost of the offense to the victim and, counter-intuitively, with increases in the benefit of the offense to the offender. Data from naturalistic offenses and experimental studies supported these predictions. Offenders are more willing to confess when the benefit of the offense to them is high, the cost to the victim is low, and the probability of information leakage is high. This suggests a conflict of interests between senders and receivers: Often, offenders are more willing to confess when confessions are less beneficial to the victims. An evolutionary-computational framework is a fruitful approach to understanding the factors that regulate communication.

Evolutionary psychology: new perspectives on cognition and motivation.

Evolutionary psychology is the second wave of the cognitive revolution. The first wave focused on computational processes that generate knowledge about the world: perception, attention, categorization, reasoning, learning, and memory. The second wave views the brain as composed of evolved computational systems, engineered by natural selection to use information to adaptively regulate physiology and behavior. This shift in focus--from knowledge acquisition to the adaptive regulation of behavior--provides new ways of thinking about every topic in psychology. It suggests a mind populated by a large number of adaptive specializations, each equipped with content-rich representations, concepts, inference systems, and regulatory variables, which are functionally organized to solve the complex problems of survival and reproduction encountered by the ancestral hunter-gatherers from whom we are descended. We present recent empirical examples that illustrate how this approach has been used to discover new features of attention, categorization, reasoning, learning, emotion, and motivation.

Evolution of direct reciprocity under uncertainty can explain human generosity in one-shot encounters.

Are humans too generous? The discovery that subjects choose to incur costs to allocate benefits to others in anonymous, one-shot economic games has posed an unsolved challenge to models of economic and evolutionary rationality. Using agent-based simulations, we show that such generosity is the necessary byproduct of selection on decision systems for regulating dyadic reciprocity under conditions of uncertainty. In deciding whether to engage in dyadic reciprocity, these systems must balance (i) the costs of mistaking a one-shot interaction for a repeated interaction (hence, risking a single chance of being exploited) with (ii) the far greater costs of mistaking a repeated interaction for a one-shot interaction (thereby precluding benefits from multiple future cooperative interactions). This asymmetry builds organisms naturally selected to cooperate even when exposed to cues that they are in one-shot interactions.

The ancestral logic of politics: upper-body strength regulates men's assertion of self-interest over economic redistribution.

Over human evolutionary history, upper-body strength has been a major component of fighting ability. Evolutionary models of animal conflict predict that actors with greater fighting ability will more actively attempt to acquire or defend resources than less formidable contestants will. Here, we applied these models to political decision making about redistribution of income and wealth among modern humans. In studies conducted in Argentina, Denmark, and the United States, men with greater upper-body strength more strongly endorsed the self-beneficial position: Among men of lower socioeconomic status (SES), strength predicted increased support for redistribution; among men of higher SES, strength predicted increased opposition to redistribution. Because personal upper-body strength is irrelevant to payoffs from economic policies in modern mass democracies, the continuing role of strength suggests that modern political decision making is shaped by an evolved psychology designed for small-scale groups.

The architecture of human kin detection.

Evolved mechanisms for assessing genetic relatedness have been found in many species, but their existence in humans has been a matter of controversy. Here we report three converging lines of evidence, drawn from siblings, that support the hypothesis that kin detection mechanisms exist in humans. These operate by computing, for each familiar individual, a unitary regulatory variable (the kinship index) that corresponds to a pairwise estimate of genetic relatedness between self and other. The cues that the system uses were identified by quantitatively matching individual exposure to potential cues of relatedness to variation in three outputs relevant to the system's evolved functions: sibling altruism, aversion to personally engaging in sibling incest, and moral opposition to third party sibling incest. As predicted, the kin detection system uses two distinct, ancestrally valid cues to compute relatedness: the familiar other's perinatal association with the individual's biological mother, and duration of sibling coresidence.

Colloquium paper: adaptive specializations, social exchange, and the evolution of human intelligence.

Blank-slate theories of human intelligence propose that reasoning is carried out by general-purpose operations applied uniformly across contents. An evolutionary approach implies a radically different model of human intelligence. The task demands of different adaptive problems select for functionally specialized problem-solving strategies, unleashing massive increases in problem-solving power for ancestrally recurrent adaptive problems. Because exchange can evolve only if cooperators can detect cheaters, we hypothesized that the human mind would be equipped with a neurocognitive system specialized for reasoning about social exchange. Whereas humans perform poorly when asked to detect violations of most conditional rules, we predicted and found a dramatic spike in performance when the rule specifies an exchange and violations correspond to cheating. According to critics, people's uncanny accuracy at detecting violations of social exchange rules does not reflect a cheater detection mechanism, but extends instead to all rules regulating when actions are permitted (deontic conditionals). Here we report experimental tests that falsify these theories by demonstrating that deontic rules as a class do not elicit the search for violations. We show that the cheater detection system functions with pinpoint accuracy, searching for violations of social exchange rules only when these are likely to reveal the presence of someone who intends to cheat. It does not search for violations of social exchange rules when these are accidental, when they do not benefit the violator, or when the situation would make cheating difficult.

Rational inferences about social valuation.

The decisions made by other people can contain information about the value they assign to our welfare-for example how much they are willing to sacrifice to make us better off. An emerging body of research suggests that we extract and use this information, responding more favorably to those who sacrifice more even if they provide us with less. The magnitude of their trade-offs governs our social responses to them-including partner choice, giving, and anger. This implies that people have well-designed cognitive mechanisms for estimating the weight someone else assigns to their welfare, even when the amounts at stake vary and the information is noisy or sparse. We tested this hypothesis in two studies (N=200; US samples) by asking participants to observe a partner make two trade-offs, and then predict the partner's decisions in other trials. Their predictions were compared to those of a model that uses statistically optimal procedures, operationalized as a Bayesian ideal observer. As predicted, (i) the estimates people made from sparse evidence matched those of the ideal observer, and (ii) lower welfare trade-offs elicited more anger from participants, even when their total payoffs were held constant. These results support the view that people efficiently update their representations of how much others value them. They also provide the most direct test to date of a key assumption of the recalibrational theory of anger: that anger is triggered by cues of low valuation, not by the infliction of costs.

To punish or repair? Evolutionary psychology and lay intuitions about modern criminal justice.

We propose that intuitions about modern mass-level criminal justice emerge from evolved mechanisms designed to operate in ancestral small-scale societies. By hypothesis, individuals confronted with a crime compute two distinct psychological magnitudes: one that reflects the crime's seriousness and another that reflects the criminal's long-term value as an associate. These magnitudes are computed based on different sets of cues and are fed into motivational mechanisms regulating different aspects of sanctioning. The seriousness variable regulates how much to react (e.g., how severely we want to punish); the variable indexing the criminal's association value regulates the more fundamental decision of how to react (i.e., whether we want to punish or repair). Using experimental designs embedded in surveys, we validate this theory across several types of crime and two countries. The evidence augments past research and suggests that the human mind contains dedicated psychological mechanisms for restoring social relationships following acts of exploitation.

Formidability and the logic of human anger.

Eleven predictions derived from the recalibrational theory of anger were tested. This theory proposes that anger is produced by a neurocognitive program engineered by natural selection to use bargaining tactics to resolve conflicts of interest in favor of the angry individual. The program is designed to orchestrate two interpersonal negotiating tactics (conditionally inflicting costs or conditionally withholding benefits) to incentivize the target of the anger to place greater weight on the welfare of the angry individual. Individuals with enhanced abilities to inflict costs (e.g., stronger individuals) or to confer benefits (e.g., attractive individuals) have a better bargaining position in conflicts; hence, it was predicted that such individuals will be more prone to anger, prevail more in conflicts of interest, and consider themselves entitled to better treatment. These predictions were confirmed. Consistent with an evolutionary analysis, the effect of strength on anger was greater for men and the effect of attractiveness on anger was greater for women. Also as predicted, stronger men had a greater history of fighting than weaker men, and more strongly endorsed the efficacy of force to resolve conflicts--both in interpersonal and international conflicts. The fact that stronger men favored greater use of military force in international conflicts provides evidence that the internal logic of the anger program reflects the ancestral payoffs characteristic of a small-scale social world rather than rational assessments of modern payoffs in large populations.

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.