The word “altruistic” might conjure images of a selfless, charitable individual who puts the needs of others above their own, but what does it really mean? The American Psychological Association (n.d.) offers one possible definition of altruism as “apparently unselfish behavior that provides benefit to others at some cost to the individual”. As a concept, altruism has captured the academic interest of both individual scientists, and entire branches of psychology.

In particular, evolutionary psychology, which studies behaviour as a response informed by survival and reproduction pressures (Tooby & Cosmides, 2015), raised several theories on why we might engage in behaviour that does not benefit, and which may even harm, oneself. For one, costly signaling theory suggests that willingly taking on personal costs to behave altruistically serves as a social indicator that a person is trustworthy, increasing the likelihood of them forming positive associations with others (McAndrew, 2019). This contributes to one’s ability to survive, especially as part of a social species, where isolation and loneliness can be detrimental to one’s well-being (Cacioppo et al., 2006).

Narrowing our examination of altruism from the species level, individual differences in traits and characteristics may also play some role in influencing prosocial behaviour. For example, a meta-analysis by Thielmann et al. (2020) found positive correlations between altruistic actions, and attributes such as honesty and modesty, in games that allowed participants to choose to exploit one another, but not in games without this feature.

In addition, developments in neuroimaging have allowed psychologists to study altruism on a biological level. Even as our understanding of specific neurological pathways continues to develop, research findings consistently point to links between physical brain structures and prosocial acts. Activity levels in brain regions associated with emotional processing, such as the amygdala and insula, would vary across individuals, and be correlated with altruistic behaviour (Filkowski et al., 2016). Damage to these structures also had concrete effects on altruism. When the basolateral subregion of the amygdala was lesioned, the likelihood of selfless behaviour towards another person became moderated by how close that person was to the individual (Kalenscher et al., 2025).

In the face of various possible mechanisms for altruism, it is important to also consider the culmination of all these factors into the desire, whether conscious or otherwise, to act selflessly. Naturally, our care and concern for our loved ones may motivate us to act in their best interests, even if this brings about negative outcomes for us (Kolm, 2006). In general, Lee et. al (2005) also found that altruists often showed a strong ability to empathise with the people they demonstrated altruism towards, as verbalised in interviews.

Tying together these various sources of research, it seems that a person’s internal thought process is inextricably intertwined with underlying biological and evolutionary factors, all of which act together to produce altruistic behaviour. Ultimately, when the opportunity to act altruistically arises, perhaps the responsibility lies with us to try our best to do good by others, within our abilities and capacities.

 

Written by:

Laura Zheng Kailin

National University of Singapore (NUS)

 

References:

American Psychological Association. (n.d.). Altruism. In APA Dictionary of Psychology. Retrieved June 9, 2025, from https://dictionary.apa.org/altruism

Cacioppo, J. T., Hawkley, L. C., Ernst, J. M., Burleson, M., Berntson, G. G., Nouriani, B., & Spiegel, D. (2006). Loneliness within a nomological net: An evolutionary perspective. Journal of Research in Personality, 40(6), 1054–1085. https://doi.org/10.1016/j.jrp.2005.11.007

Filkowski, M. M., Cochran, R. N., & Haas, B. W. (2016). Altruistic behavior: mapping responses in the brain. Neuroscience and Neuroeconomics, 5, 65–75. https://doi.org/10.2147/NAN.S87718

Kalenscher, T., Lüpken, L. M., Stoop, R., Terburg, D., & Van Honk, J. (2025). Steeper social discounting after human basolateral amygdala damage. Proceedings of the National Academy of Sciences, 122(16), e2500692122. https://doi.org/10.1073/pnas.2500692122

Kolm, S.-C. (2006). Chapter 1 Introduction to the Economics of Giving, Altruism and Reciprocity. In Handbook of the Economics of Giving, Altruism and Reciprocity (Vol. 1, pp. 1–122). Elsevier. https://doi.org/10.1016/S1574-0714(06)01001-3

Lee, D. Y., Kang, C. H., Lee, J. Y., & Park, S. H. (2005). Characteristics of exemplary altruists. Journal of Humanistic Psychology, 45(2), 146–155. https://doi.org/10.1177/0022167805274954

McAndrew, F. T. (2019). Costly Signaling Theory. In T. K. Shackelford & V. A. Weekes-Shackelford (Eds.), Encyclopedia of Evolutionary Psychological Science (pp. 1–8). Springer International Publishing. https://doi.org/10.1007/978-3-319-16999-6_3483-1

Thielmann, I., Spadaro, G., & Balliet, D. (2020). Personality and prosocial behavior: A theoretical framework and meta-analysis. Psychological Bulletin, 146(1), 30–90. https://doi.org/10.1037/bul0000217

Tooby, J. & Cosmides, L. (2015). The Theoretical Foundations of Evolutionary Psychology. In Buss, D. M. (Ed.), The Handbook of Evolutionary Psychology, Second edition. Volume 1: Foundations. (pp. 3-87). Hoboken, NJ: John Wiley & Sons.