Testosterone
Does testosterone simply equal aggression?
Testosterone is generally understood to influence multiple aspects of male reproductive development, including anatomy and reproductive motivation. There is a belief in popular culture that testosterone causes aggression and violence. This belief is ubiquitous to the point of being common knowledge. When bodybuilders take anabolic steroids, everyone jokes about “roid rage”. Large, hulking strange men are commonly described to elicit fear. For culture, testosterone is aggression. While there is nuance to this belief, the testosterone-aggression relationship is not a myth. Testosterone has a robust library of literature linking it to aggressive behavior. The myth is a simplification of the causation. Testosterone does directly support aggressive tendencies, but there are cultural/societal/hierarchical factors at play as well. To address the myth is to acknowledge the role that nurture and nuances of nature play on behavioral shifts.
The testosterone-aggression relationship is expanded upon when examining human behavior on an individual level. Most men, regardless of testosterone level, are criminally nonviolent. Those who argue that aggression is largely learned point to differences in violent crime rates between cultures around the world. These differences suggest that cultures of violence teach and encourage aggressive behavior (Powell, 2021). This is supported by the famous Culture of Honor experiment, where it was hypothesized that the southern culture of personal honor would cause southerners to respond more aggressively than northerners when “accidentally” bumped by a research volunteer. The findings showed that southerners were more likely to respond aggressively and testosterone levels were shown to rise as a result. Northerners were less likely to experience a rise in testosterone (Cohen et al., 1996).
Research further shows that there is only a weak connection between testosterone and aggression and a nearly nonexistent connection between testosterone and physical violence. Castration experiments have shown that while testosterone is necessary for aggression, testosterone alone is not sufficient. Researchers theorize that testosterone more accurately causes dominant behavior, which may or may not result in aggression depending on social factors such as male-male competition (Mims, 2007). Ultimately it is argued that acting out testosterone-mediated dominant behavior via aggression and violence is a choice and a learned behavior.
When discussing non-human species, the testosterone-aggression causation is more clear. There is mixed evidence in mammal and bird species that supports the assumption that increased testosterone levels during mating season leads to increase in aggression levels which supports male reproductive competitiveness (Behringer & Deschner, 2017). This body of research is collectively known as the Challenge Hypothesis. This hypothesis was put forward in the early 1990’s to explain how mating rituals and social interactions amongst birds affect aggression and hormone levels, specifically testosterone. Male sparrows were shown to have elevated circulating testosterone following aggressive interactions (Wingfield et al., 1990). This led to a flurry of studies exploring how fluctuating levels of testosterone might be influenced by territorial trespassing from rival males. While baseline levels of testosterone do not correlate with aggression, testosterone levels are shown to surge during periods of competition between males for territory, challenge and mate guarding (Wingfield et al., 2020). A 2004 study of chimpanzees supported the Challenge Hypothesis, finding that high-ranking chimpanzees showed higher levels of aggression than lower-ranking members of the community and also produced higher levels of testosterone in their urine (Muller & Wrangham, 2004). The Challenge Hypothesis was fundamental in starting the field of environmental endocrinology, but modern research now considers it to be overly simplistic. That said, a 2017 paper studying testosterone in primates confirms that testosterone promotes male competition and aggression in reproductive contexts (Muller, 2017).
The testosterone-aggression myth is compelling because it is easy and to some extent, it is right. In 2021, an article was published in the Harvard Gazette about an interview with Harvard human evolutionary biologist Carole Hooven. In this she discussed the role of testosterone in “powering acts of aggression”. She points to how significantly higher levels of testosterone in males has an effect on gene expression that manifests in larger muscles and more aggressive behavior. These physiological and behavioral shifts allow male deer, for example, to display acts of aggression when testosterone spikes during the rut. Hooven also explains that on a macro level, 94% of incarcerated persons worldwide are male and the majority of incarcerated males have elevated testosterone (Powell, 2021) (United Nations Office on Drugs and Crime). In popular culture, strong men like Sylvester Stallone and Arnold Schwartzinagger are famous for starring in violent action films. Iconic male roles in Die Hard, 300, Gladiator embody classic testosterone qualities of physical strength, endurance and overcoming challenges, but also gore, violence and aggression. The classic American sport of football is a quintessential celebration of male combat.
Ultimately, the myth is compelling because it is partially true. In a culture of violence, testosterone boosts aggression and violence. Violent criminals are almost universally male and most have higher levels of testosterone. The myth is also nuanced because human culture is nuanced. We have invented healthy outlets for dominance and aggression with our sports, our games, our politics and our legal system. Our top paid lawyers are described as “fighters” and “killers”, but they only wield a pen. We have robust punishments for violence that cause even the most triggered person to hesitate. We have conscious minds that may consider our actions and act against our basic natures. We are intelligent. We teach pacifism and kindness that cause dominance to manifest in nonviolent ways. Ultimately though, the conversation is complicated. The myth perpetuates for a good reason.
Works Cited
Behringer, V., & Deschner, T. (2017). Non-invasive monitoring of physiological markers in primates. Hormones and Behavior, 91, 3–18. https://doi.org/10.1016/j.yhbeh.2017.02.001
Challenge Hypothesis—An overview | ScienceDirect Topics. (n.d.). Retrieved February 10, 2025, from https://www-sciencedirect-com.ezproxy2.library.colostate.edu/topics/neuroscience/challenge-hypothesis
Cohen, D., Nisbett, R. E., Bowdle, B. F., & Schwarz, N. (1996). Insult, Aggression, and the Southern Culture of Honor: An “Experimental Ethnography.”
Milewski, T. M., Lee, W., Champagne, F. A., & Curley, J. P. (n.d.). Behavioural and physiological plasticity in social hierarchies. Philosophical Transactions of the Royal Society B: Biological Sciences, 377(1845), 20200443. https://doi.org/10.1098/rstb.2020.0443
Mims, C. (2007, July 5). Strange but True: Testosterone Alone Does Not Cause Violence. Scientific American. https://www.scientificamerican.com/article/strange-but-true-testosterone-alone-doesnt-cause-violence/
Muller, M. N. (2017). Testosterone and reproductive effort in male primates. Hormones and Behavior, 91, 36–51. https://doi.org/10.1016/j.yhbeh.2016.09.001
Muller, M. N., & Wrangham, R. W. (2004). Dominance, aggression and testosterone in wild chimpanzees: A test of the ‘challenge hypothesis.’ Animal Behaviour, 67(1), 113–123. https://doi.org/10.1016/j.anbehav.2003.03.013
Powell, A. (2021, September 17). How a hormone affects society. Harvard Gazette. https://news.harvard.edu/gazette/story/2021/09/harvard-biologist-discusses-testosterones-role-in-society/
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Studerus, E., Gamma, A., & Vollenweider, F. X. (2010). Psychometric Evaluation of the Altered States of Consciousness Rating Scale (OAV). PLoS ONE, 5(8), e12412. https://doi.org/10.1371/journal.pone.0012412
Testosterone in Historical Pop Culture and Media—Titan Medical Associates Ltd. (2023, August 25). https://titanmalehealth.com/testosterone-in-historical-pop-culture-and-media/
Wingfield, J. C., Hegner, R. E., Dufty, Alfred M., & Ball, G. F. (1990). The “Challenge Hypothesis”: Theoretical Implications for Patterns of Testosterone Secretion, Mating Systems, and Breeding Strategies. The American Naturalist, 136(6), 829–846. https://doi.org/10.1086/285134
Wingfield, J. C., Ramenofsky, M., Hegner, R. E., & Ball, G. F. (2020). Whither the challenge hypothesis? Hormones and Behavior, 123, 104588. https://doi.org/10.1016/j.yhbeh.2019.104588
