Human Aggression: The causes, effects, and what we can do about it.

by Tushar Sunkum

Aggressiveness is one of the most standout traits in human beings. This personality trait has led to many great things, such as playing a role to spur the development of human civilization itself. It has also led to many bad outcomes, such as war and social inequality on a macroscale level, and crime and petty violence on a microscale level. What is this behavior? What are the mechanisms in the human brain that cause this behavior? Is there any cure for individuals for excessive levels of this personality trait? These and other questions will be taken on in this blog and answered comprehensively.

Let’s start with aggressiveness and where it comes from, and how it has changed in human beings over the years. To start off, Anger, which is what aggressiveness is based off of, is known as one of the innate emotions, meaning that it is hardwired into us biologically (Šimić et al., 2021). It is in our nature as human beings to experience this powerful emotion, no matter where we are from or what culture we belong to.

There are two types of aggression that are identified, proactive and reactive aggression (Wrangham., 2017). Reactive aggression is what it sounds like in name. It is a quick second, impulsive reaction to a situation (Wrangham., 2017). As for proactive aggression, Wrangham defines it as,”a purposeful planned attack with an external or internal reward as a goal…..premeditated, and deliberate efforts to harm a particular victim” (2017). Wrangham (2017) also finds that around 200,000 years ago, humans actually had a reduction in anatomical features associated with reactive aggression, thus becoming less reactive aggressive compared to other primates, such as chimpanzees. However Wrangham (2017) finds that our propensity to proactive aggression, which is a more planned, premeditated version of aggressive behavior, remains high.

Both of these types of aggression can cause violence, although the type of violence differs. Reactive aggression is more associated with types of crimes such as bar fights and petty homicide, while proactive aggression is associated with events such as premeditated murder and war (Wrangham,2017). Reactive aggression is the type of aggression that I will focus on, as it is reactive aggression that is the mechanism that causes the common, blue-collar, everyday violent crimes and disputes (O’Flaherty and Sethi.,2015).

To look inside the human body to find the anatomical causes of aggression, we have to look inside the brain. It is the organ in the body where feelings are expressed and the actions are carried out. One way to look inside the brain is through FMRI. FMRI, or Functional Magnetic Resonating Imaging, measures and maps brain activity based on changes in the blood oxygenation (Koutala et al.,2023). A meta-analysis which analyzed nine studies using this method, identified the limbic regions, superior temporal gyrus, right posterior cingulate cortex, precentral gyrus, and the precuneus, right inferior frontal gyrus(Nikolic et al.,2022). Interestingly, this study did not find reduced activity in the prefrontal cortex in these aggressive individuals regarding reactive aggression. However it contradicts multiple studies that show otherwise (da Cunha-Bang et al.,2018, da Cunha-Bang et al.,2017). Like many of the other studies cited in this paragraph, these two studies by Dr. Sofi da Cunha-Bang and colleagues highlighted the amygdala as having a potential role for aggressive behavior. There is also reduced gray matter in the prefrontal cortex in people with antisocial personality disorder(O’Flaherty and Sethi.,2015).

Another piece of the puzzle can be seen anecdotally in the famous incident involving a railroad worker named Phineas Gage. This incident, which happened in the 19th century, saw Gage have significant damage to his prefrontal cortex. This led to him being violent and impulsive(Raine,2013). In sum, all of the studies showed either the amygdala and/or prefrontal cortex had a big role in some form or another.

Although aggressiveness is a universal feeling, not all human beings experience this to the same extent. We know that males exhibit this behavior more than females (Archer.,2004). Males have a higher level of testosterone than women do (van Anders et al.,2015). It is thought that higher levels of testosterone make for higher aggressive behavior as well. It is a common consensus that genetics do play a role in aggressive behavior(O’Flaherty and Sethi.,2015). However, there is also considerable debate around what genes play a role, and if they even play a role at all(Fuentes.,2012). Undeniably though, there are variations among humans in aggressive behavior. Those that exhibit excessive levels of aggression can have certain personality disorders like ASPD, otherwise known as Antisocial Personality Disorder (Moini et al.,2023). It is the individuals with these types of conditions which the potential treatments mentioned in the following paragraphs are for.

The challenge is that the broader society tends to think of people with these disorders as incurable. They are thought to be irredeemable menaces to society, and efforts to improve their quality of life are deemed as wasteful and futile.

This notion couldn’t be further from the truth. There are many signs of hope that if developed and researched further, could be ultimate cures. When looking at pharmacological treatments, antiepileptic drugs (AEDs) that have GABA related mechanisms have promise to reduce aggressive impulsive outbursts in individuals (Stanford et al.,2009). Stanford et al.(2009) specifically recommend the AED phenytoin as a treatment for aggressive outbursts.

Non-drug therapies have shown potential as well. For instance, Lavender aromatherapy has been shown to decrease aggressive behavior in elderly adults with dementia(Young Lee and Kanho Hakhoe Chi.,2005). Many other essential oils also induce calming-like behavior, such as frankincense (Fatemeh et al.,2021). There certainly appears to be untapped potential for using essential oils as a non-drug method for treating excessive aggressive behavior in individuals with disorders such as ASPD. CBT, or cognitive behavioral therapy is another non-drug therapy used for treating aggression. CBT works by helping individuals change their ways of reacting to problems (Chand et al.,2023). It has been shown to reduce violent behavior in individuals (Bhatt et al.,2023). This is another promising treatment which has shown to have a lot of potential.

In conclusion, aggression is a natural human emotion. It is part of who we are. It has a long history among homo sapiens, whether it’s for the best or for the worst.

Despite many benefits of aggressive behavior, there are many disadvantages. It causes petty assaults and petty disputes that lead to many injuries, or worse, tragic losses of lives. Homicide kills about 20,000 Americans every year (UNODC.,2025). Many of these killings occur over petty disputes (O’Flaherty and Sethi.,2010). However, these disadvantages of aggression are not a searing pain human society will inevitably have to live with. There is a way: a treatment to greatly mitigate, or perhaps cure the “bad side” of aggression once and for all.

References

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