The Adaptive Functions of Morality: The Intersection of Moral & Evolutionary Psychology

The Trolley Problem.


I was introduced to the study of human morality with the trolley problem: you see a trolley that is going to run over five people and you can pull a lever to divert the trolley to kill one person, saving the five others. Should you pull the lever? The implausibility of this scenario may lead us to think that moral judgments are infrequent; however, in reality we make moral judgments every day. For example, imagine that you’re riding on a crowded bus and I bump into you. You might come to the conclusion that I’m malicious; rude at best. Or you may think that I was merely thrown off balance by the momentum of the bus. In this moment you’ve made a judgment about the rightness or wrongness of my behavior. And this sort of judgment isn’t uncommon: every time we judge something as right or wrong, good or evil, prosocial or antisocial, a moral judgment has been made.

Morality refers to the principles that distinguish right from wrong. In my discussion of morality I will take a psychological perspective, which is focused on what the world is like rather than how it ought to be. A psychologist isn’t interested in whether utilitarianism is moral, but rather is focused on how people perceive the moral permissibility of utilitarian judgments. I will not be considering whether the attitudes and behaviors I discuss are right or wrong; I will be simply noting how attitudes and behaviors that could be considered moral (or immoral) impact evolutionary fitness: how well an organism can survive and reproduce in its environment.

To do so, I’m going to discuss research articles that I’ve come across while searching for answers to the questions of why certain moral beliefs persist, the functions of morality, and why errors in moral judgment occur. With an evolutionary framework, studying how morality impacts evolutionary fitness may provide answers to these questions.

More specifically, I will discuss 1) morality in non-human animals, 2) the development of moral intuitions, 3) cultural factors that influence ethical frameworks, 4) how morality functions, and 5) the persistence of immoral behavior. At first glance, it seems like morality increases direct fitness, how well an organism survives in their environment (which is measured by the number of viable offspring an organism produces), and my discussion will focus on how moral attitudes or behavior may increase or decrease direct fitness.

Morality in Non-Human Animals

Non-human animals may not possess the complex cognitive processes that give rise to moral attitudes, but certain behavioral syndromes (“personality” in animals) are reminiscent of human morality. Some animals exhibit reciprocal altruism: providing assistance to conspecifics (members of the same species), with the understanding that they will help you in the future. Reciprocal altruism is one of the factors that has helped large-scale human societies flourish (Diamond, 1999).

Pied Flycatcher.

Past studies have pinpointed non-human species that display reciprocal altruism and other moral behavioral syndromes. For instance, pied flycatchers engage in mobbing behavior, which are coordinated assaults to drive away predators (Krams, Krama, Igaune, & Mänd, 2007). These researchers predicted that mobbing behavior may function as a “tit for tat” strategy, such that if an initial pied flycatcher (mobbing initiator) is joined by a second pied flycatcher (co-operator) in mobbing a predator, then the mobbing initiator would be more likely to help the co-operator fend off a predator in the future. Alternatively, if the mobbing initiator is abandoned by a defector (a pied flycatcher that does not assist in mobbing behavior), the mobbing initiator would be less likely to act altruistically towards the defector in the future. To test this, Krams et al. (2007) assigned pairs of pied flycatchers to one of three positions (A, B, C) that represented nests. In phase one, B birds were removed and a predator (a stuffed owl) was placed in nest A. The researchers observed the mobbing behavior of A birds and any assistance from C birds. In phase two, B birds were brought back and predators were introduced to both B and C nests. The question was which group A birds would help: B (defectors) or C (co-operators)? In all trials of phase one, group C birds helped group A birds. In 30 out of the 32 phase two trials, nest box A birds helped C birds mob the predator yet never responded to group B birds. Given mobbing behavior’s potential for serious injury or death, these results suggest that the principle of reciprocal altruism underlies both rewards for cooperation and punishment for defectors.

Mobbing Behavior in Birds.

Although these results suggest that fitness (in this case, defending the nest from a predator allowing for future reproduction) is increased by reciprocal altruism, the specific cognitive mechanisms by which reciprocity functions in non-human species are unclear. Animal reciprocity appears to be symmetry-based, where animals mirror the actions of conspecifics in a close proximity; but evidence of calculated reciprocity, which requires weighing the pros and cons of acting altruistically, is scarce (Dufour, Pelé, Sterck, & Thierry, 2007). Since reciprocity in humans depends on understanding the value of goods and calculating the gain/loss of these goods over time, Dufour et al. (2007) explored chimpanzee’s capacity for self-control and anticipation over time to serve as a model for expectation management in non-human animals. In this study, the researchers gave chimpanzees a cookie and measured how long they could wait to exchange this cookie for a better reward. The researchers found that chimpanzees can wait longer durations for better rewards, which suggests that chimpanzees have the ability to weigh the benefits of a larger reward versus the costs of a longer wait time. However, Dufour et al. (2007) concluded that the small time scale of delay in chimpanzees (minutes) compared to humans (days, weeks, or years), suggests that chimpanzees do not have the ability to predict, plan, and execute complex reciprocal behaviors.

A Chimpanzee.

Moving away from reciprocal altruism, there is evidence that specific behaviors that some humans consider “immoral” serve an adaptive function in animals. For instance, deception is common in animals and it may increase fitness (Krebs, 1977). Any conclusions about the impact of morality on non-human animal fitness, however, is limited in three ways: 1) animals do not possess the cognitive abilities humans do and as a result 2) research is limited to behavioral measures, and finally 3) to classify animal behavior as “moral” or “immoral” is anthropomorphizing. Furthermore, the relationship between behavioral syndromes and direct fitness in the studies that I’ve discussed is unclear.

Let’s transition from animals to humans.

We’ll explore research in several domains: the development of morality, the influence of culture and religion, how humans make moral judgments, and the persistence of immoral behavior.

Developmental Perspectives

Developmental research often focuses on empathy, the ability to understand what another person is feeling. Empathic concern is a component of empathy and refers to the emotional reactions that we feel in response to another person in need. Because past research suggests that empathy may lead to prosocial behavior, Roth-Hanania, Davidov, and Zahn-Waxler (2011) studied infant reactions to maternal and peer distress. Infants were exposed to videos of both their mother being injured and an unfamiliar infant crying. The researchers measured affective expressions such as gestures, facial expressions, and sounds that the infants produced. Infants ages 8–10 months displayed emotional and cognitive empathy, but did not display prosocial behavior (trying to comfort their mother or peer) until after 24 months. It’s important to note that early affective/cognitive empathy predicted future prosocial behavior (Roth-Hanania et al., 2011). This study provides evidence that empathy develops earlier than previous researchers thought, and this empathy leads to future prosocial behavior. Future studies should explore how early empathy and later prosocial behavior influence direct fitness.

Infant reactions to the distress of others may function as building blocks for future cooperation, which helps human survive (Diamond, 1999). In addition, infant reactions may increase direct fitness by helping them stay alive long enough to reproduce. This is supported by how infants react differently to prosocial versus antisocial behaviors in others (Hamlin, Wynn, & Bloom, 2010). To test this, the researchers simulated “helper” versus “hinderer” situations, varying whether it was a person or object that was acted upon (Hamlin et al., 2010). Infants were assigned to view a helper or a hinder “person” represented by a human-like shape with googly eyes. The helper person was shown pushing another person up a hill and the hinderer person was shown pushing another person down a hill. In addition, the helper/hinderer person was shown pushing an inanimate object (a non-human-like shape, such as a triangle without googly eyes) up or down the hill. The researchers measured the reactions to each of the four scenarios and then measured how long infants looked at helpers versus hinderers. Hamlin et al. (2010) found that infants preferred characters that helped other people up the hill, but did not have a preference for inanimate objects being pushed up or down. Infants also spent significantly less time looking at hinderers rather than neutral or helper characters. These results are limited by the fact that non-human objects were used to test infant reactions. That being said, this study suggests that infants have the ability to discriminate between stimuli that could potentially harm them.

“Helper” and “Hinderer” Stimuli.

Religion and Morality

Infants may possess the innate ability to recognize the emotions of others, act compassionately as they mature, and recognize harmful stimuli, all of which may increase fitness. Even so, cross-cultural variability in morality suggests that cultural factors further the development of morality after infancy (Jordan et al., 2015). Religion is one of these cross-cultural factors. Past researchers have considered how numerous religious traditions have been grounded in ethical principles such as compassion and forgiveness, leading to the creation of many hospitals, homeless shelters, and charities (Biblemesh, 2012; Hardy, 2013). While comparing self-rated morality to their peers, Furrow, King, and White (2004) found that high school students endorsed the idea of an implicit morality derived from religion, such that prosocial personality traits and religious identity were strongly correlated. Furthermore, self-reports suggest a relationship between religion and specific moral attributes. For instance, those with high self-reports of empathy, altruism, and honesty also scored highly on religiosity measurements (Saroglou, Pichon, Trompette, Verschueren, & Dernelle, 2005). These self-reports were confirmed by evaluations of siblings and friends. In addition, specific attributes of religion may contribute to the perception of morality in others. Ward and King (2019) found that engaging in religious behaviors and maintaining a belief in God increased the mortality ratings of a religious target, which indicates that both self-reports and perceptions of the morality in others vary based on religiosity.

Religiosity is related to characteristics that may impact direct fitness. Furnham and Cheng (2015) found that high scores on religious background and service attendance measures were related to higher education levels and employment rates. Furthermore, Tiggermann and Hage (2019) found that religion and spirituality were positively correlated with maintaining a positive body image in a sample of 345 women. In sum, religion may be perceived as the foundation of morality and religion is related to factors that may increase fitness, such as higher socioeconomic status, education, empathy, and altruism. Given how adaptive traits constitute trade-offs (Nettle, 2006) more research is needed on the specific combinations of adaptive traits in relation to religiosity.

As mentioned above, infants possess the innate ability to recognize harm, notice pain in others, and to prefer prosocial over antisocial individuals. These responses may be strengthened by religion to form the dynamic moral intuitions and beliefs that adults possess, which serve many functions.

The Functions of Morality

One of the functions of morality is to help us make moral judgments about the relationship between the mental states of others and personal agency (Cushman, 2008). With implications in the legal system, Cushman (2008) argues that people distinguish between intent and responsibility when making moral judgments. Two experiments test whether judgments of punishment/blame are different from judgments of morality/wrongness (Cushman, 2008). In experiment one, participants were presented situations in which a person intentionally or unintentionally harms or does not harm another person (Cushman, 2008). Results suggest that judgments about wrongness depend on the beliefs/desires of the agent, but not on the consequences. Imagine if a person wants to burn another individual by pouring hot coffee on the victim but fails to actually pour the coffee. This is perceived as wrong. In contrast, judgments about blame depend on both beliefs/desires and consequences. Using the same example, the perpetrator would not be blamed because the consequence (i.e., coffee spilled on the other person) did not happen. The person who had the intention to pour coffee on another, but failed to do so, is perceived as wrong but is not blamed.

Experiment two was designed to test if the results from experiment one are applicable across a variety of moral judgments. Using the same design as experiment one, participants were asked additional questions about permissibility and punishment, rather than wrongness and blame. The results suggest that judgments about permissibility are dependent on desires whereas judgments about punishment depend on consequences. The results of these two experiments suggest that there are competing mental operations for different types of moral judgments, which contradicts the idea that humans only punish wrongful acts (Cushman, 2008). Future research should explore these two types of moral judgments (analyzing harmful consequences versus considering the mental states underpinning actions) to understand their adaptive significance.

A Lifeboat.

Cushman, Grey, Gaffey and Mendes (2012) designed two experiments to test if moral judgments in adults function via emphatic concern. In experiment one participants were asked if it is morally permissible to push one person off of a lifeboat to save everyone else on board. The researchers found that heightened physiological measures correlated with lesser willingness to do so. Experiment two was designed to clarify whether the willingness to kill one person to save the lives of many is dependent on empathic concern for the victim, perceptions about the action of killing itself, or both (Cushman et al., 2012). Participants were told to act out pretend harmful behaviors, such as smashing the experimenter’s hand with a brick, and were explicitly told that no actual harm would occur. The experimenters found that performing pretend harmful actions increased physiological responses more so than witnessing the same harmful actions or performing equivalent non-harmful actions (like hitting the experimenter’s hand with a feather). These results suggest that aversion to harming others has physiological and psychological roots. Conducting this experiment with a sequential design would shed light on the self-domestication hypothesis (humans domesticated themselves by selecting for reduced aggression), by testing whether humans have stronger aversive reactions to harming others over time.

Adding to the potential of morality to evoke prosocial behavior, ethical frameworks at the society-level may help increase cooperation, which increases direct fitness. Curry, Mullins, and Whitehouse (2019) find fault with past research on cooperation. On one hand, previous studies focus on narrow cooperative behaviors (e.g., reciprocal altruism) and do not take into account the cumulative effects of the wide range of cooperative behavior in humans. In addition, past researchers have not focused on whether the cooperative functions of morality are present across cultures. To improve upon these limitations, Curry et al. (2019) identified seven cooperation problems and tested whether these behaviors are considered morally good across cultures. The researchers gathered ethnographic information and categorized the database into each of the seven cooperation behaviors (helping the group, helping your kin, positive reciprocity, negative reciprocity, hawk/dove traits, dividing resources, and possession). The researchers found that all seven cooperative behaviors were perceived as morally good in 60 cultures. However, this study failed to take into account personality traits that may contribute to these behaviors (e.g., generosity, empathy). In addition, the researchers coded for the moral endorsement of cooperative behaviors in a binary manner (either a society endorsed or did not endorse a behavior). Future studies should take this into account by exploring the degree to which a society endorses a moral idea, rather than if the endorsement is simply present or not.

Immoral Behavior

Given the ability of morality to increase direct fitness, regulate our willingness to harm others, and cooperate with non-kin groups, the persistence of immoral behavior is puzzling. Psychopaths violate social norms, harm others, lie, deceive, and represent a significant portion of the incarcerated population, despite being a tiny fraction of the general population. Krupp, Sewall, Lalumière, Sheriff, and Harris (2012) studied a mechanism by which psychopathy may persist, given the fact that many of their characteristics are considered immoral. By analyzing hundreds of cases of violent offenders, the researchers found that psychopathy was negatively associated with relatedness to the victim. Krupp et al. (2012) argue that psychopathy may be adaptive because it does not share the characteristics of other severe mental disorders, it is related to social exploitation, and it is positively related to reproductive efforts. In other words, psychopathy increases the direct fitness of the individual by decreasing the fitness of others. Furthermore, psychopathy increases indirect fitness (the fitness of kin) by focusing harmful behavior on non-kin. The main limitation is that while antisocial behavior is often directed to non-kin, this study failed to measure the drawbacks of psychopathy on kin. Future studies ought to focus on the specific combinations of psychopathic traits and environmental factors that maximize fitness.


I’ve outlined evidence that moral behavior (specifically reciprocal altruism) exists in non-human animals, however it likely does not function through the complex cognitive mechanisms that humans rely on. In addition, immoral behavior such as deception may increase fitness, similar to how combinations of psychopathic traits such as directing antisocial behavior to non-kin increase fitness. We also saw that from birth, humans have some innate understanding of morality. Research on infants suggest that they prefer prosocial individuals and that they can understand the pain of other people. I also discussed how moral beliefs may be bolstered by religious teachings, leading to significant relationships between religious involvement and adaptive personality traits. Furthermore, some perceive religion as necessary for morality. Moving from the origins of morality to its function, adult research suggests that morality helps with harm aversion and making judgments about blame, wrongness, and punishment.

Moral judgments are ubiquitous in the lives of non-human animals and in our lives. By understanding how we come to conclusions about right and wrong, we may help reduce suffering, act justly, and promote human wellbeing.


BibleMesh. (2012, February 06). The Christian Origins of Hospitals. Retrieved from

Curry, O. S., Mullins, D. A., & Whitehouse, H. (2019). Is It Good to Cooperate? Testing the Theory of Morality-as-Cooperation in 60 Societies. Current Anthropology, 60(1), 47–69. doi: 10.1086/701478

Cushman, F. (2008). Crime and punishment: Distinguishing the roles of causal and intentional analyses in moral judgment. Cognition, 108(2), 353–380. doi: 10.1016/j.cognition.2008.03.006

Cushman, F., Gray, K., Gaffey, A., & Mendes, W. B. (2012). Simulating murder: The aversion to harmful action. Emotion, 12(1), 2–7. doi: 10.1037/a0025071

Diamond, J. M. (1999). Guns, germs, and steel: The fates of human societies.

Dufour, V., Pelé, M., Sterck, E. H. M., & Thierry, B. (2007). Chimpanzee (Pan troglodytes) anticipation of food return: Coping with waiting time in an exchange task. Journal of Comparative Psychology, 121(2), 145–155. doi: 10.1037/0735–7036.121.2.145

Furnham, A., & Cheng, H. (2015). Associations between education, gender, social class personality traits, and religious faith and service attendance in a British cohort. Personality and Individual Differences,86, 63–66. doi: 10.1016/j.paid.2015.06.014

Furrow, J. L., King, P. E., & White, K. (2004). Religion and positive youth development: Identity, meaning, and prosocial concerns. Applied Developmental Science,8(1), 17–26. doi:10.1207/s1532480xads0801_3

Hamlin, J. K., Wynn, K., & Bloom, P. (2010). Three-month-olds show a negativity bias in social evaluation. Developmental Science, 13, 923– 939.

Hardy, G. (2013, December). Why Give? Religious Roots of Charity. Retrieved from

Jordan, J., Leliveld, M. C., & Tenbrunsel, A. E. (2015). The Moral Self-Image Scale: Measuring and Understanding the Malleability of the Moral Self. Frontiers in Psychology,6. doi:10.3389/fpsyg.2015.01878

Krams, I., Krama, T., Igaune, K., & Mänd, R. (2007). Experimental evidence of reciprocal altruism in the pied flycatcher. Behavioral Ecology and Sociobiology, 62(4), 599–605. doi: 10.1007/s00265–007–0484–1

Krebs, J. R. (1977). The significance of song repertoires: The Beau Geste hypothesis. Animal Behaviour, 25, 475–478. doi: 10.1016/0003–3472(77)90022–7

Krupp, D. B., Sewall, L. A., Lalumière, M. L., Sheriff, C., & Harris, G. T. (2012). Nepotistic Patterns of Violent Psychopathy: Evidence for Adaptation? Frontiers in Psychology, 3. doi: 10.3389/fpsyg.2012.00305

Nettle, D. (2006). The evolution of personality variation in humans and other animals. American Psychologist, 61(6), 622–631. doi: 10.1037/0003–066x.61.6.622

Roth-Hanania, R., Davidov, M., & Zahn-Waxler, C. (2011). Empathy development from 8 to 16 months: Early signs of concern for others. Infant Behavior and Development, 34(3), 447–458. doi: 10.1016/j.infbeh.2011.04.007

Saroglou, V., Pichon, I., Trompette, L., Verschueren, M., & Dernelle, R. (2005). Prosocial behavior and religion: New evidence based on projective measures and peer ratings. Journal for the Scientific Study of Religion,44(3), 323–348. doi:10.1111/j.1468–5906.2005.00289.x

Tiggemann, M., & Hage, K. (2019). Religion and spirituality: Pathways to positive body image. Body Image,28, 135–141. doi: 10.1016/j.bodyim.2019.01.004

B.A. Psychology • Join me as I continue to learn about research, mental health, statistics, and academia • Let’s connect ➜

Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store