What makes humans moral beings? This question can be understood either as a proximate question or as an ultimate question. The question is about the mental and social mechanisms that produce moral judgments and interactions, and has been investigated by psychologists and social scientists. The question is about the fitness consequences that explain why humans have morality, and has been discussed by evolutionary biologists in the context of the evolution of cooperation. Our goal here is to contribute to a fruitful (...) articulation of such proximate and ultimate explanations of human morality. We develop an approach to morality as an adaptation to an environment in which individuals were in competition to be chosen and recruited in mutually advantageous cooperative interactions. In this environment, the best strategy is to treat others with impartiality and to share the costs and benefits of cooperation equally. Those who offer less than others will be left out of cooperation; conversely, those who offer more will be exploited by their partners. In line with this mutualistic approach, the study of a range of economic games involving property rights, collective actions, mutual help and punishment shows that participants' distributions aim at sharing the costs and benefits of interactions in an impartial way. In particular, the distribution of resources is influenced by effort and talent, and the perception of each participant's rights on the resources to be distributed. (shrink)

In order to describe the logic of morality, "contractualist" philosophers have studied how individuals behave when they choose to follow their moral intuitions. These individuals, contractualists note, often act as if they have bargained and thus reached an agreement with others about how to distribute the benefits and burdens of mutual cooperation. Using this observation, such philosophers argue that the purpose of morality is to maximize the benefits of human interaction. The resulting "contract" analogy is both insightful and puzzling. On (...) one hand, it captures the pattern of moral intuitions, thus answering questions about human cooperation: why do humans cooperate? Why should the distribution of benefits be proportionate to each person's contribution? Why should the punishment be proportionate to the crime? Why should the rights be proportionate to the duties? On the other hand, the analogy provides a mere as-if explanation for human cooperation, saying that cooperation is "as if" people have passed a contract-but since they didn't, why should it be so? To evolutionary thinkers, the puzzle of the missing contract is immediately reminiscent of the puzzle of the missing "designer" of life-forms, a puzzle that Darwin's theory of natural selection essentially resolved. Evolutionary and contractualist theory originally intersected at the work of philosophers John Rawls and David Gauthier, who argued that moral judgments are based on a sense of fairness that has been naturally selected. In this book, Nicolas Baumard further explores the theory that morality was originally an adaptation to the biological market of cooperation, an arena in which individuals competed to be selected for cooperative interactions. In this environment, Baumard suggests, the best strategy was to treat others with impartiality and to share the costs and benefits of cooperation in a fair way, so that those who offered less than others were left out of cooperation while those who offered more were exploited by their partners. It is with this evolutionary approach that Baumard ultimately accounts for the specific structure of human morality. (shrink)

From an evolutionary point of view, the function of moral behaviour may be to secure a good reputation as a co-operator. The best way to do so may be to obey genuine moral motivations. Still, one's moral reputation maybe something too important to be entrusted just to one's moral sense. A robust concern for one's reputation is likely to have evolved too. Here we explore some of the complex relationships between morality and reputation both from an evolutionary and a cognitive (...) point of view. (shrink)

In the past decade, experiments on altruistic punishment have played a central role in the study of the evolution of cooperation. By showing that people are ready to incur a cost to punish cheaters and that punishment help to stabilise cooperation, these experiments have greatly contributed to the rise of group selection theory. However, despite its experimental robustness, it is not clear whether altruistic punishment really exists. Here, I review the anthropological literature and show that hunter-gatherers rarely punish cheaters. Instead, (...) they avoid dealing with them and switch to other partners. I suggest that these data are better explained by individual selection, and in particular by partner choice models, in which individuals are in competition to be recruited by cooperative partners. I discuss two apparent problems for partner choice theories: large-scale cooperation and punishments in economic games. I suggest that rather than favouring group selection theory, these two phenomena provide evidence in favour of individual selection: (1) people produce large-scale cooperation through institutions in which punishment is not altruistic but rewarded on an individual basis; (2) punishment in experimental games can be explained without altruism and is indeed often better explained by individual interests. (shrink)

Since the Industrial Revolution, human societies have experienced high and sustained rates of economic growth. Recent explanations of this sudden and massive change in economic history have held that modern growth results from an acceleration of innovation. But it is unclear why the rate of innovation drastically accelerated in England in the eighteenth century. An important factor might be the alteration of individual preferences with regard to innovation resulting from the unprecedented living standards of the English during that period, for (...) two reasons. First, recent developments in economic history challenge the standard Malthusian view according to which living standards were stagnant until the Industrial Revolution. Pre-industrial England enjoyed a level of affluence that was unprecedented in history. Second, behavioral sciences have demonstrated that the human brain is designed to respond adaptively to variations in resources in the local environment. In particular, Life History Theory, a branch of evolutionary biology, suggests that a more favorable environment should trigger the expression of future-oriented preferences. In this paper, I argue that some of these psychological traits – a lower level of time discounting, a higher level of optimism, decreased materialistic orientation, and a higher level of trust in others – are likely to increase the rate of innovation. I review the evidence regarding the impact of affluence on preferences in contemporary as well as past populations, and conclude that the impact of affluence on neurocognitive systems may partly explain the modern acceleration of technological innovations and the associated economic growth. (shrink)

Imaginary worlds are extremely successful. The most popular fictions produced in the last few decades contain such a fictional world. They can be found in all fictional media, from novels (e.g., Lord of The Rings and Harry Potter) to films (e.g., Star Wars and Avatar), video games (e.g., The Legend of Zelda and Final Fantasy), graphic novels (e.g., One Piece and Naruto), and TV series (e.g., Star Trek and Game of Thrones), and they date as far back as ancient literature (...) (e.g., the Cyclops Islands in The Odyssey, 850 BCE). Why such a success? Why so much attention devoted to non-existent worlds? In this paper, we propose that imaginary worlds co-opt our preferences for exploration, which have evolved in humans and nonhuman animals alike, to propel individuals toward new environments and new sources of reward. Humans would find imaginary worlds very attractive for the very same reasons, and under the same circumstances, as they are lured by unfamiliar environments in real life. After reviewing research on exploratory preferences in behavioral ecology, environmental esthetics, neuroscience, and evolutionary and developmental psychology, we focus on the sources of their variability across time and space, which we argue can account for the variability of the cultural preference for imaginary worlds. This hypothesis can, therefore, explain the way imaginary worlds evolved culturally, their shape and content, their recent striking success, and their distribution across time and populations. (shrink)

Punitive behaviours are often assumed to be the result of an instinct for punishment. This instinct would have evolved to punish wrongdoers and it would be the evidence that cooperation has evolved by group selection. Here, I propose an alternative theory according to which punishment is a not an adaptation and that there was no specific selective pressure to inflict costs on wrongdoers in the ancestral environment. In this theory, cooperation evolved through partner choice for mutual advantage. In the ancestral (...) environment, individuals were in competition to be recruited in cooperative ventures and it was vital to share the benefits of cooperation in a mutually advantageous manner. If individuals took a bigger share of the benefits, their partners would leave them for more interesting partners. If they took a smaller share, they would be exploited by their partners who would receive more than what they had contributed to produce. This competition led to the selection of a sense of fairness, a cognitive adaptation aiming to share equally the benefits of cooperation in order to attract partners. In this theory, punishment is not necessary for the evolution of cooperation. Punitive behaviours are only a way to restore fairness by compensating the victim or penalizing the culprit. Drawing on behavioural economics, legal anthropology, and cognitive psychology, I show that empirical data fit better with this framework than with the theory of group selection. When people punish, they do so to restore fairness rather than to help the group. (shrink)

We propose an approach reconciling the ultimate-level explanations proposed by Savage et al. and Mehr et al. as to why music evolved. We also question the current adaptationist view of culture, which too often fails to disentangle distinct fitness benefits.

Henrich et al.’s article fleshes out in a very useful and timely manner comments often heard but rarely published about the extraordinary cultural imbalance in the recruitment of participants in psychology experiments and the doubt this casts on generalization of findings from these “weird” samples to humans in general. The authors mention that one of the concerns they have met in defending their views has been of a methodological nature: “the observed variation across populations may be due to various methodological (...) artifacts that arise from translating experiments across contexts” (sect. 7.2, para. 1). Here we want to express a less sweeping methodological concern. While accepting the general conclusions and recommendations of the article, we believe they should be complemented with a.. (shrink)

The belief in immanent justice is the expectation that the universe is designed to ensure that evil is punished and virtue rewarded. What makes this belief so ‘natural’? Here, we suggest that this intuition of immanent justice derives from our evolved sense of fairness. In cases where a misdeed is followed by a misfortune, our sense of fairness construes the misfortune as a way to compensate for the misdeed. To test this hypothesis, we designed a set of studies in which (...) we show that people who do not believe in immanent justice are nonetheless implicitly influenced by intuitions of immanent justice. Strikingly, this effect disappears when the misfortune is disproportionate compared to the misdeed: In this case, justice is not restored and participants lose the intuition of immanent justice. Following recent theories of religion, we suggest that this intuition contributes to the cultural success of beliefs in immanent justice. (shrink)

Narrative fictions have surely become the single most widespread source of entertainment in the world. In their free time, humans read novels and comics, watch movies and TV series, and play video games: they consume stories that they know to be false. Such behaviors are expanding at lightning speed in modern societies. Yet, the question of the origin of fictions has been an evolutionary puzzle for decades: Are fictions biological adaptations, or the by-products of cognitive mechanisms that evolved for another (...) purpose? The absence of any consensus in cognitive science has made it difficult to explain how narrative fictions evolve culturally. We argue that current conflicting hypotheses are partly wrong, and partly right: narrative fictions are by-products of the human mind, because they obviously co-opt some pre-existing cognitive preferences and mechanisms, such as our interest for social information, and our abilities to do mindreading and to imagine counterfactuals. But humans reap some fitness benefits from producing and consuming such appealing cultural items, making fictions adaptive. To reconcile these two views, we put forward the hypothesis that narrative fictions are best seen as entertainment technologies that is, as items crafted by some people for the proximate goal to grab the attention of other people, and with the ultimate goal to fulfill other evolutionary-relevant functions that become easier once other people’s attention is caught. This hypothesis explains why fictions are filled with exaggerated and entertaining stimuli, why they fit so well the changing preferences of the audience they target, and why producers constantly make their fictions more attractive as time goes by, in a cumulative manner. (shrink)

We review recent evidence that game rules, rules of etiquette, and supernatural beliefs, that the authors see as “ritualistic” conventions, are in fact shaped by instrumental inference. In line with such examples, we contend that cultural practices that may appear, from the outside, to be devoid of instrumental utility, could in fact be selectively acquired and preserved because of their perceived utility.

Humans pay close attention to the reputational consequences of their actions. Recent experiments indicate that even very subtle cues that one is being observed can affect cooperative behaviors. Expressing our opinions about the morality of certain acts is a key means of advertising our cooperative dispositions. Here, we investigated how subtle cues of being watched would affect moral judgments. We predicted that participants exposed to such cues would affirm their endorsement of prevailing moral norms by expressing greater disapproval of moral (...) transgressions. Participants read brief accounts of two moral violations and rated the moral acceptability of each violation. Violations were more strongly condemned in a condition where participants were exposed to surveillance cues (an image of eyes interposed between the description of the violation and the associated rating scale) than in a control condition (in which the interposed image was of flowers). We discuss the role that public declarations play in the interpersonal evaluation of cooperative dispositions. (shrink)

Our discussion of the commentaries begins, at the evolutionary level, with issues raised by our account of the evolution of morality in terms of partner-choice mutualism. We then turn to the cognitive level and the characterization and workings of fairness. In a final section, we discuss the degree to which our fairness-based approach to morality extends to norms that are commonly considered moral even though they are distinct from fairness.

I am grateful to have received so many stimulating commentaries from interested colleagues regarding the psychological origins of the Industrial Revolution and the role of evolutionary theory in understanding historical phenomena. Commentators criticized, extended, and explored the implications of the perspective I presented, and I wholeheartedly agree with many commentaries that more work is needed. In this response, I thus focus on what is needed to further test the psychological origins of the Industrial Revolution. Specifically, I argue, in agreement with (...) many commentators, that we need: better data about standards of living, psychological preferences, and innovation rates ; better models to understand the role of resources in driving cultural evolution and the multiple aspects of the behavioral constellation of affluence ; and better predictions and better statistical instruments to disentangle the possible mechanisms behind the rise of innovativeness. (shrink)

Strong reciprocity theorists claim that punishment has evolved to promote the good of the group and to deter cheating. By contrast, weak reciprocity suggests that punishment aims to restore justice (i.e., reciprocity) between the criminal and his victim. Experimental evidences as well as field observations suggest that humans punish criminals to restore fairness rather than to support group cooperation.

A long tradition of research in WEIRD (Western, Educated, Industrialized, Rich, Democratic) countries has investigated how people weigh individual welfare versus group welfare in their moral judgments. Relatively less research has investigated the generalizability of results across non-WEIRD populations. In the current study, we ask participants across nine diverse cultures (Bali, Costa Rica, France, Guatemala, Japan, Madagascar, Mongolia, Serbia, and the USA) to make a series of moral judgments regarding both third-party sacrifice for group welfare and first-person sacrifice for group (...) welfare. In addition to finding some amount of cross-cultural variation on most of our questions, we also find two cross-culturally consistent judgments: (1) when indi- viduals are in equivalent situations, overall welfare should be maximized, and (2) harm to individuals should be taken into account, and some types of individual harm can trump overall group welfare. We end by discussing the specific pattern of variable and consistent features in the context of evolutionary theories of the evolution of morality. (shrink)

Why do many societies moralize apparently harmless pleasures, such as lust, gluttony, alcohol, drugs, and even music and dance? Why do they erect temperance, asceticism, sobriety, modesty, and piety as cardinal moral virtues? According to existing theories, this puritanical morality cannot be reduced to concerns for harm and fairness: it must emerge from cognitive systems that did not evolve for cooperation (e.g., disgust-based “Purity” concerns). Here, we argue that, despite appearances, puritanical morality is no exception to the cooperative function of (...) moral cognition. It emerges in response to a key feature of cooperation, namely that cooperation is (ultimately) a long-term strategy, requiring (proximately) the self-control of appetites for immediate gratification. Puritanical moralizations condemn behaviors which, although inherently harmless, are perceived as indirectly facilitating uncooperative behaviors, by impairing the self-control required to refrain from cheating. Drinking, drugs, immodest clothing, and unruly music and dance, are condemned as stimulating short-term impulses, thus facilitating uncooperative behaviors (e.g., violence, adultery, free-riding). Overindulgence in harmless bodily pleasures (e.g., masturbation, gluttony) is perceived as making people slave to their urges, thus altering abilities to resist future antisocial temptations. Daily self-discipline, ascetic temperance, and pious ritual observance are perceived as cultivating the self-control required to honor prosocial obligations. We review psychological, historical, and ethnographic evidence supporting this account. We use this theory to explain the fall of puritanism in WEIRD societies, and discuss the cultural evolution of puritanical norms. Explaining puritanical norms does not require adding mechanisms unrelated to cooperation in our models of the moral mind. (shrink)

While we cannot directly measure the psychological preferences of individuals, and the moral, emotional, and cognitive tendencies of people from the past, we can use cultural artifacts as a window to the zeitgeist of societies in particular historical periods. At present, an increasing number of digitized texts spanning several centuries is available for a computerized analysis. In addition, developments form historical economics have enabled increasingly precise estimations of sociodemographic realities from the past. Crossing these datasets offer a powerful tool to (...) test how the environment changes psychology and vice versa. However, designing the appropriate proxies of relevant psychological constructs is not trivial. The gold standard to measure psychological constructs in modern texts – Linguistic Inquiry and Word Count – has been validated by psychometric experimentation with modern participants. However, as a tool to investigate the psychology of the past, the LIWC is limited in two main aspects: it does not cover the entire range of relevant psychological dimensions and the meaning, spelling, and pragmatic use of certain words depend on the historical period from which the fiction work is sampled. These LIWC limitations make the design of custom tools inevitable. However, without psychometric validation, there is uncertainty regarding what exactly is being measured. To overcome these pitfalls, we suggest several internal and external validation procedures, to be conducted prior to diachronic analyses. First, the semantic adequacy of search terms in bags-of-words approaches should be verified by training semantic vector spaces with the historical text corpus using tools like word2vec. Second, we propose factor analyses to evaluate the internal consistency between distinct bag-of-words proxying the same underlying psychological construct. Third, these proxies can be externally validated using prior knowledge on the differences between genres or other literary dimensions. Finally, while LIWC is limited in the analysis of historical documents, it can be used as a sanity check for external validation of custom measures. This procedure allows a robust estimation of psychological constructs and how they change throughout history. Together with historical economics, it also increases our power in testing the relationship between environmental change and the expression of psychological traits from the past. (shrink)

We received several commentaries both challenging and supporting our hypothesis. We thank the commentators for their thoughtful contributions, bringing together alternative hypotheses, complementary explanations, and appropriate corrections to our model. Here, we explain further our hypothesis, using more explicitly the framework of evolutionary social sciences. We first explain what we believe is the ultimate function of fiction in general (i.e., entertainment) and how this hypothesis differs from other evolutionary hypotheses put forward by several commentators. We then turn to the proximate (...) features that make imaginary worlds entertaining and, therefore, culturally successful. We finally explore how these insights may explain the distribution of imaginary worlds across time, space, age, and social classes. (shrink)