Nicolas Baumard

A Mutualistic Approach to Morality: The Evolution of Fairness by Partner Choice

What makes humans moral beings? This question can be understood either as a proximate “how” question or as an ultimate “why” question. The “how” question is about the mental and social mechanisms that produce moral judgments and interactions, and has been investigated by psychologists and social scientists. The “why” 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.

Preschoolers are able to take merit into account when distributing goods.

Classic studies in developmental psychology demonstrate a relatively late development of equity, with children as old as 6 or even 8-10 years failing to follow the logic of merit--that is, giving more to those who contributed more. Following Piaget (1932), these studies have been taken to indicate that judgments of justice develop slowly and follow a stagelike progression, starting off with simple rules (e.g., equality: everyone receives the same) and only later on in development evolving into more complex ones (e.g., equity: distributions match contributions). Here, we report 2 experiments with 3- and 4-year-old children (N = 195) that contradict this constructivist account. Our results demonstrate that children as young as 3 years old are able to take merit into account by distributing tokens according to individual contributions but that this ability may be hidden by a preference for equality.

Explaining moral religions

Moralizing religions, unlike religions with morally indifferent gods or spirits, appeared only recently in some (but not all) large-scale human societies. A crucial feature of these new religions is their emphasis on proportionality (between deeds and supernatural rewards, between sins and penance, and in the formulation of the Golden Rule, according to which one should treat others as one would like others to treat oneself). Cognitive science models that account for many properties of religion can be extended to these religions. Recent models of evolved dispositions for fairness in cooperation suggest that proportionality-based morality is highly intuitive to human beings. The cultural success of moralizing movements, secular or religious, could be explained based on proportionality.

Surveillance Cues Enhance Moral Condemnation

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.

THE EVOLUTION OF FAIRNESS IN A BIOLOGICAL MARKET

Human beings universally express a concern for the fairness of social interactions, and it remains an open question that which ultimate factors led to the evolution of this preference. Here, we present a model accounting for the evolution of fairness on the basis of individual selection alone. We consider a simple social interaction based on the Dictator Game. Two individuals, a “proposer” and a “responder,” have an opportunity to split a resource. When they have no choice but to interact together, the most powerful (here the proposer) reaps all the profits and fairness cannot evolve. Partner choice is the key lever to overcome this difficulty. Rather than just two individuals, we consider a population composed of two classes of individuals (either proposers or responders), and we allow the responders to choose their partner. In such a “biological market,” fairness evolves as an “equilibrium price,” resulting from an ecological equivalent of the law of supply and demand. If a class is disadvantaged by the chosen resource partition (i.e., if it frequently receives less than half of the resource), it is outcompeted by the other one, and automatically becomes rarer. This rarity grants it an advantage on the market, which yields in turn to the evolution of a more favorable partition. Splitting the resource into two identical halves, or more generally in a way that equalizes the payoffs of the two classes, is then the only evolutionarily stable outcome. Beyond human fairness, this mechanism also opens up new ways of explaining the distribution of benefits in many mutualistic interactions.

Religious Beliefs as Reflective Elaborations on Intuitions: A Modified Dual-Process Model:

Religious beliefs apparently challenge our view of human cognition as an evolved system that provides reliable information about environments. We propose that properties of religious beliefs are best understood in terms of a dual-processing model, in which a variety of evolved domain-specific systems provide stable intuitions, whereas other systems produce explicit, often deliberate comments on those intuitions. This perspective accounts for the fact that religious beliefs are apparently diverse but thematically similar and that they are immune to refutation and more attractive to imaginative individuals.

Social opportunities and the evolution of fairness.

We model the evolution of the division of a resource between two individuals, according to a bargaining mechanism akin to the ultimatum game, in which a dominant proposer makes an offer that his partner can only accept or refuse. Individuals are randomly drawn from an infinite population and paired two-by-two. In each pair, a proposer is chosen. The proposer offers a division of resources to his partner. If the offer is accepted it is implemented; otherwise both partners pay a cost and move on to the next social opportunity. When the role that individuals play in each interaction is chosen at random, our analysis shows that each individual receives a fraction corresponding to at least 1/2-c of the resource at evolutionary equilibrium, where c represents the cost of postponing the interaction. A quasi-fair division thus evolves as long as c is low. We show that fairness, in this model, is a consequence of the existence of an outside option for dominated individuals: namely the possibility of playing on terms more favorable to them in the future if they reject the current interaction. We discuss the interpretation and empirical implications of this result for the case of human behavior.

Partner choice creates fairness in humans

Many studies demonstrate that partner choice has played an important role in the evolution of human cooperation, but little work has tested its impact on the evolution of human fairness. In experiments involving divisions of money, people become either over-generous or over-selfish when they are in competition to be chosen as cooperative partners. Hence, it is difficult to see how partner choice could result in the evolution of fair, equal divisions. Here, we show that this puzzle can be solved if we consider the outside options on which partner choice operates. We conduct a behavioural experiment, run agent-based simulations and analyse a game-theoretic model to understand how outside options affect partner choice and fairness. All support the conclusion that partner choice leads to fairness only when individuals have equal outside options. We discuss how this condition has been met in our evolutionary history, and the implications of these findings for our understanding of other aspects of fairness less specific than preferences for equal divisions of resources.

Life-history theory explains childhood moral development

Infants understand harm and fairness in third-party situations and yet children require years of development before they apply this understanding to their own interactions with others. We suggest that the delay is explained by a life-history analysis of when behaving morally becomes beneficial. The human species is characterized by an extended period of juvenile dependence during which cooperation with non-kin is mostly superfluous. Later, as children age, moral behaviors supporting cooperation become increasingly beneficial.

What Goes Around Comes Around: The Evolutionary Roots of the Belief in Immanent Justice

AbstractThe 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.