When we think of aggression, what immediately comes to mind is physical altercations between two parties resulting from anger or prior disagreement. However, this is a dramatized and misleading characterization of what aggression truly looks like, especially what aggression looks like in the female sex. Reports on bullying, violence, and torment are overwhelmingly done using male examples and subjects to lead research. This was, in some ways, justified by stating that “women just simply are not as aggressive as men.” This is incredibly untrue, given the hard statistics where young girls in the United States from ages 12-17, in a July 2021 through December 2023 study by the National Health Interview Survey, reported 38.3 percent had been the victims of “bullying.” Teen boys, on the other hand, from ages 12-17 of the same study, only had about 29.9 percent who had experienced a significant amount of bullying. 

This clearly shows that young women actually, on average, experience more bullying and aggression in their lifetime. Where this data differs is in the response to the types of aggression that are exhibited by both genders. Schools' policies surrounding bullying usually emphasize physical violence and responses to that. This overwhelmingly assists boys in dealing with bullying, as according to the WHO, boys are about 2.3 times more likely to engage in physical altercations. Young women, on the other hand, are far more likely to use tactics of imitation, isolation, and humiliation to victimize other women. These factors influence young girls to develop mental health issues in the future after experiencing bullying from their peers. However, the question then becomes, why do women do this to each other? 

Does female aggression come from neurological structures and built-in behaviors? Or does female aggression stem from evolutionary situations, leading to women being overwhelmingly prone to intimidation tactics as a means of competition between women? 

Method:

I researched this project by carefully analysing multiple sources and drawing overall conclusions in my own words. However, my initial research stemmed from social conditioning and some of the more obvious impacts and implications of female-based aggression. When I found conclusions about these social aspects, I turned my focus towards the scientific reasoning why these social dynamics exist. There, I used evolutionary, biological, and neurological evidence to draw broader conclusions. Overall, I used a multi-faceted approach in which multiple sources were used to support overall conclusions.

Hypothesis: Women already have neurological mechanisms for relational aggression over physical aggression. Evolutionary factors like childbirth, infant mortality, and overall survival shaped the female brain to prioritize certain displays of aggression. Today, societal systems have honed a model in which women are condemned for physical aggression and have turned to relational aggression, which is often overlooked by the majority of psychological research.

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Biological Determinants of Aggression

Both men and women experience aggression; however, how they experience that aggression is drastically different.  The term aggression is defined as “a response that delivers noxious stimuli to another person.” This specifically relates to the presence and amount of specific hormones used in individuals' bodies and how they are triggered by the hypothalamus.

Testosterone is a crucial hormone used in men for gonad development and secondary sex characteristics. On average, men over the age of 18 have 264 to 916 ng/dl of testosterone in their systems; in comparison, pre-menopausal women only have about 10-55 ng/dl of testosterone produced.

In one study, ovariectomized female rats were administered testosterone, estradiol, or a placebo. The results indicated that testosterone increased the rates of physical aggression directed against other rats. The estradiol and placebo yielded no notable changes in behavior. The removal of ovaries also served to reduce the amount of violent aggression between female rats. These findings support the conclusion that biological factors have a large influence on aggressive behavior.

In humans, while these hormones are required to enable such actions, competition and stress drive this process. When women become overly stressed, it activates the hypothalamic-pituitary-adrenal axis, which in turn engages with endocrine systems. These hormonal systems, and the release of testosterone and cortisol enables aggressive behavior. It is important to note how environmental stress is an important piece to this explanation, and is, in part, a trigger of testosterone-sensitive systems.

In the modern world, aggression is often perceived in a strictly male sense. Men most often use violence, or threats of violence, as their main outward manifestations of aggression. So it's important to note that being triggered in the aggression neuro-pathway doesn't necessarily mean this type of manifestation. Aggression can be seen in relational issues and psychological manipulation. The question we then need to ask is, why do women often show this type of aggression despite being reactive to testosterone?

The answer may lie deeper in the sociological implications many women have grown up with, as well as the psychological relationships between women.

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The Neurological Implications in Men and Women Relating to Aggression

Men and women exhibit distinct neurologically driven factors in how their brains are activated during stress and in their reactions to threatening situations.

The amygdala is an almond-shaped subcortical structure in the temporal lobe. For many years, it was largely believed that the amygdala was associated primarily with fear responses; our understanding of this area of the brain is becoming more varied to represent different behavioral outputs.

In one study, women were shown to have more persistent activation of the limbic system, primarily the amygdala. This contrasted mens easily diminished reaction, telling us that women’s fear responses continue for a longer period of time than men’s. McClure et al looked at men's and women's reactions to ambiguous “angry” faces. They found that relative to men, women showed more activation of the entire fear circuit, amygdala, orbitofrontal, and anterior cingulate cortex. Men showed less uniformity in orbofrontal activation, with their fear being more based on high anxiety and reactive anger. The left area of the amygdala, specifically the one that correlates with physical aggression reactions, is generally more active in men than in women.

Further studies show us that the amygdala itself is typically larger in men than in women, a trait attributed to prenatal testosterone's impact on early brain development. The neuropeptide oxytocin is also very involved in women's natural fear response. Oxytocin is recognized for its anxiolytic properties, meaning that it results in a reduction in stress and anxiety. While oxytocin has been seen to reduce amygdala reactivity to threats in men, it is widely recognized as having the opposite effect in women. Oxytocin, which is released in part due to the presence of estrogen when binding to the amygdaya actually serves to strengthen the fear response in females, which is often viewed as a method for survival and infant protection. Women reflect a more subtle type of aggression in order to maximize chances at survival.

Furthermore, looking into different emotional responses of the two sexes gives us more insight. The anterior insula cortex (AIC) and the anterior cingulate cortex (ACC) have been suspected to have a major role in aggression. These structures monitor basic bodily needs, including thirst, and are also activated in response to a range of emotions, primarily fear and anger. It has been proposed that the AIC monitors the internal neural and visceral state, often coined as interoception, and the ACC mediates the subjective experience of emotion. This means that the AIC makes individuals primarily think about their physical survival, and how these events affect their actual bodily systems; on the other hand, the ACC relates to emotional trauma and responses to these events.

Women generally have greater amounts of grey matter within their brains and higher blood flow towards the ACC. Additionally, Multiple studies examining sex differences in neural activation to emotional stimuli have also found that women often show larger activation in the ACC and men in the AIC. In response to specifically negative stimuli, women showed greater reactivity than men in the ACC, suggesting that women process stimuli in terms of subjective emotional states. Men have also been seen to have more activation in the AIC compared to women. This suggests that women process stress and fear in a more subjective emotional lens, whereas men process these events through a physiological introceptive state.

Females tend to have a larger prefrontal cortex relative to their brain size when compared to men. This enables stronger emotional regulation, which can translate to lower rates of outward aggression. Men, in contrast, demonstrate higher activity in the right ventrolateral frontal cortex, which is related to impulse control. Further proving how men's neuro-structures are geared towards physical aggression when compared to the relational aggression often observed in women.

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The Implications of Sociological Factors and Social Conditioning.

In studies across the world, aggression is primarily looked at and studied through a male lens and with male participants. This has enabled this kind of mysticism revolving around female-based aggression and societal condemnation of stereotypically feminine aggression.

Aggression is not only a physical act, it can also entail social humiliation, exclusion, and public rejection. Research over the past decade has proven that girls participate in aggressive and exclusionary behaviors equally if not more so than their male counterparts. The commonly held view is that while relational aggression is unpleasant, physical aggression is far more damaging, for example, the widely taught quote and lesson, “sticks and stones may break my bones, but words will never hurt me.” However, studies actually contradict this; girls often suffer more than boys in the long run after being victimized. This can look like anxiety, depression, and loneliness.

Girls' social standings can also look different within this kind of social hierarchy between women. Some girls find themselves at the top of the social ladder after victimizing others, and this incentivizes these types of actions and has a “social payoff.” Cillessen and Mayeux (2004) found that young girls who engaged in relational aggression were held in higher regard by their peers socially, but were actually more widely disliked.

Women who have also experienced abuse are far more likely to experience or engage in these behaviors. Jasper, Smith, and Bailey (1998) found that 71% of girls in a forensic mental health facility had experienced at least one form of abuse. Family dysfunction also plays a key role in female aggression. Females who experience some level of family dysfunction are far more likely to enable abusive relationships in their personal lives and inflict social harassment on others.

Furthermore, women are often taught from a young age to be more “nurturing” and emotionally expressive than men. This has morphed into the way aggression is accepted and understood within women. Society did not diminish aggression within women; it instead redirected it into more “acceptable forms.”

Media representation also plays into this, where women in film are portrayed to use passive aggressive tactics and clique dynamics to confront others. This has ended up manifesting into girls' idealizing and playing into these social hierarchies.

Society seems to turn a blind eye to this form of aggression, resulting in it being unchecked. This is partially why we see such high rates of anxiety, depression, and other forms of mental illness in young girls.

Overall, many cultures and societies' perception of what is feminine and “acceptable” for women has facilitated social aggression between women. This has overwhelmingly resulted in these alternative types of relational aggression forming. Today, we continue to see this form of aggression being mocked and being reduced to “catfights.” This has further perpetuated this issue and let this continue further.

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Female aggression on Social media

The use and innovation of social media have added another layer of complexity to this topic. Now, women's aggression can go even more unnoticed as private chatrooms and comment sections enable anonymity, which allows for further harassment.

When looking into lots of the harassment and online bullying that female celebrities face, an interesting thing to notice is how these comments often come from other women. With celebrities such as Megan Markle and Amber Heard receiving high criticism often rooted in sexism. You can disagree with their actions; however, the way their gender has played into their internet hate is also apparent. This online behavior is perpetuated by women condemning other women.

This has to do with the way social media has amplified peer-aggression. Studies have indicated a link between intimidating “selfies” and rates of online posts to self-presentation strategies rooted in female psychology. Social media intensifies social comparison, with “likes” and “followers” serving as direct evidence of popularity and infamy. When a social hierarchy becomes in many ways quantifiable, it leads to further issues regarding young girls' self-esteem and other such factors. This relates to psychological conclusions about power and how underhanded relational aggression serves to maintain social power.

Online environments also serve to prevent people from feeling as connected to what they say online. If you can detach your name and identity from your accounts, why would you care about the impacts of what you say? You will not have to deal with the consequences. Inyears past, women generally tried to avoid direct social confrontation; however, social media has facilitated a new way to interact.

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Evolutionary Factors in Female Aggression

When we look into the behavior of both men and women, their actions when it comes to aggression and competition greatly differ. However, this is not due to a lack of anger or stress that women experience in contrast to men; in reality, the evolutionary factors that contributed to the success of the human species may have a large impact.

In the past, sexual competition between humans was almost entirely focused on males, which highlighted male competition for “mates.” However, this diminishes the true nature of sexual selection. Historians and anthropologists today are becoming more aware of the female aspect that played into sexual selection. With biparental care and diminished sexual dimorphism being highly present in our species, it is clear how women also had to compete to enable their family’s survival. Women aimed to discredit their rivals and highlight their own assets.

Through these new understandings made by archaeologists, we have also concluded that ecological factors and individual implications, such as population density, sex ratios, and variation in male quality, also played a part.

It has also been proven that historical females who lacked a firm father figure, or lost their father very young, actually started their menstrual cycle earlier as well. Accelerations in puberty timings enabled young girls to be more competitive in the reproductive market. In addition, older girls were more sensitive to this change, so younger women entering this area were more likely to be victimized in the process. Even today, we see women who enter puberty younger being more likely to engage in criminal activity and drug abuse, which relates back to hormonal attributes being present in aggression and reactivity.

Among primates, dominance relations are most discernible in female-bonded species. However, these relationships are facilitated through matrilines. These relationships actually enable a sort of stability within the species, in which fewer physical altrications occur. In Studies with bonobos, the females constituted only 9 out of 325 aggressive episodes recorded. Using dominance to stabilize interactions and a reluctance of females to engage in physical violence suggest that there must be some risks involved. Females differ from men in both their child rearing and reproductive success. Females are able to have successful offspring when they are present in their children's infancy; this contrasts with paternal care, as having a father figure in the wild doesn’t lead as directly to survival. Infancy and early childhood are vulnerable periods. Among the Ache of Paraguay, 13% of children die before the end of their first year and 27% before the age of five. The mother is the infant's most important anchor, who aids in their survival.

This suggests that there is a psychological adaptation to lower rates of outward aggression, and women are more risk-averse than men. Women actually tend to be more fearful, showing more signs of anxiety and neuroticism. Additionally, women have more corrugator muscle and electrodermal activity than men when viewing negative images and stronger fear responses to startling noises, indicating women's general predisposition to anxiety.

Following September 11, 2009,  a sample of Americans were given a survey to indicate general public fear. Women gave significantly higher assessments of the danger, and generally were shown to be more panicked given the situation.  This also has an alternative effect in which women sometimes feel the need to suppress fear to avoid “victimization”, presenting as overly aggressive to mediate these fears.

The truth is, like all organisms, women compete; the nature of that competition is what piques curiosity. Anthropologists also serve to emphasize how women's roles culturally and the traditional form of femininity impact different forms of aggression perpetuated among females. The role that mothers play in infant survival also provides an evolutionary viewpoint and framework that corresponds to the overwhelming truth about female aggression.

This is a research project, and I included my overall findings and broader data in the research portion of this assignment.

This text is added to meet the minimum character requirement.

In conclusion, female aggression is far more complex than is largely given credit for. While male aggression has been the baseline and accepted portrayal of aggression, research shows us that female aggression still exists, but not in as obvious ways. Relational aggression and social hierarchies are cornerstones of female portrayals of aggression. Hormonal differences between men and women, and the neurological and structural differences in men's and women's brains, also serve to give some additional context. Research also indicates that the vast complexities of evolution have deterred women from physical forms of aggression. 

Cultural barriers and expectations of women have further cemented these forms of relationships among women. Societal expectations condemn women for using physical aggression, which is seen as “non-feminine.” The glamorization and sexualization of relational aggression, being seen as “catfights,” results in a further misunderstanding of women. It becomes clear that policymakers, educators, and psychologists need to become better acquainted with this study and identify these patterns within women and broader social systems. 

Overall, it is clear that female aggression is a combination of multiple factors. Most notably womens neurological and evolutionary disposition away from physical violence and towards relational competition. However, this is also partially manifested by the sociological factors in our everyday lives. Societal conditioning of young girls and what is perceived to be feminine and non-feminine has allowed for discrete aggression between girls to fester. Resulting in heightened levels of social shame, isolation, and mental health problems among young girls. This confirms my initial hypothesis about the intersection of evolutionary, societal, and neurological factors.

Works cited:

Sarah Blaffer Hrdy. The Woman That Never Evolved: With a New Preface and Bibliographical Updates. Harvard University Press, 1981, https://books.google.ca/books?hl=en&lr=&id=pICPOwf3lMsC&oi=fnd&pg=PR11&ots=GW4Ine7-mQ&sig=0242sB4LXoPXcdAb3vodey3oTg4&redir_esc=y#v=onepage&q&f=false. Accessed 03 03 2026.

Campbell, Anne. “The evolutionary psychology of women's aggression - PMC.” PMC, https://pmc.ncbi.nlm.nih.gov/articles/PMC3826207/. Accessed 3 March 2026.

Catharine P. Cross. “Women's aggression.” Aggression and Violent Behavior, sciencedirect, 10 2011, https://www.sciencedirect.com/science/article/abs/pii/S1359178911000425. Accessed 03 03 2026.

D'Ardenne\, Kimberlee. “ASU study identifies sex-based differences in physical aggression | ASU News.” ASU News\, 9 May 2024\, https://news.asu.edu/20240509-science-and-technology-asu-study-identifies-sexbased-differences-physical-aggression. Accessed 3 March 2026.

“The Dark Side of Girlhood: Recent Trends, Risk Factors and Trajectories to Aggression and Violence.” PMC, https://pmc.ncbi.nlm.nih.gov/articles/PMC2538724/. Accessed 3 March 2026.

KATELLA, KATHY. “How Social Media Affects Your Teen's Mental Health: A Parent's Guide.” Yale Medicine, 17 June 2024, https://www.yalemedicine.org/news/social-media-teen-mental-health-a-parents-guide. Accessed 3 March 2026.

Reed, Phil. “Are Women Just as Aggressive as Men?” Psychology Today, 3 February 2023, https://www.psychologytoday.com/ca/blog/digital-world-real-world/202302/research-casts-doubt-on-male-centred-theories-of-aggression. Accessed 3 March 2026.

Vaillancourt, Tracy. “Do human females use indirect aggression as an intrasexual competition strategy?” PMC, https://pmc.ncbi.nlm.nih.gov/articles/PMC3826209/. Accessed 3 March 2026.

Weir, Kirsten. “Social media brings benefits and risks to teens. Psychology can help identify a path forward.” American Psychological Association, 1 September 2023, https://www.apa.org/monitor/2023/09/protecting-teens-on-social-media. Accessed 3 March 2026.

Image:

eidy_riveros. Brain image. Pinterest. https://ca.pinterest.com/pin/322148179614867677/

I would like to acknowledge the hard work of my teacher sponsor, Mr. Niki Foruk, for supporting me and guiding me through this process. I would like to give thanks to all of the researchers who continue to expand upon and draw new conclusions about this ever-evolving topic. I would also like to appreciate all of the volunteers, teachers, and organizers who enable CYSF to continue to expand young minds and give students the opportunity to research topics of their choice.