In my last post, I stated that the significance of genetics could not be ignored when determining whether criminal behaviour was inherited or learnt. I focused on a story of a serial killer and the results of twin studies to prove my point. In this post, I would like to introduce the two forms of aggression and compare between the people who display these behaviours: proactive aggression and reactive aggression.
Proactive aggression is a calculated goal-oriented method of hurting others. Examples of this would include revenge crimes—when person A intentionally plans and harms person B for maltreating person C (someone who is important to person A). On the other hand, reactive aggression results in “crimes of passion” where the assailant is driven by impulse to harm their victim(s). For instance, person A insults person B who, in his fit of anger, assaults person A. These two types of aggression are consistently demonstrated by violent criminals albeit two different types. The first form of aggression is found in almost every psychopathic serial killer there has been, as psychopathic criminals are more likely to engage in proactive aggression than non-psychopathic criminals. They meticulously structure and execute the killings of multiple victims over and over, usually to fulfill their bizarre needs. The latter form is found in most offenders—those who lack the ability to contain their anger and cannot resist the temptation of a fight. Both groups of criminals break laws and hurt others, but is there a difference in their biological makeup that sets them apart from each other and the peaceful majority of people?
Psychopaths are calculating, meticulous planners with high executive functioning and charming personalities. Some deviate from the law and are serial killers, using predatory violence to attack their victims. With their beguiling charm, no one could ever tell they had the potential to kill. “Jolly” Jane Toppan is a good example of a murderous psychopath who showed no trace of violence or deviation from your typical, friendly nurse. She worked at Cambridge Hospital in 1885, where she would stealthily inject elderly patients with an overdose of morphine and watch as they sank into comas. Then, she would revive them with atropine and observe in gratification as her victims died a slow death. She was a proactive murderer with an extremely unstable childhood and defective amygdalae and ventral prefrontal cortex, which would explain her ability to kill innumerably and the absurdity of her case.
Contrastingly, most serial offenders are affective attackers (those who attack in reaction to something else). These impulsive criminals biologically deviate from the rest of us peaceful citizens in a number of ways: low serotonin, MAO-A deficiency, and less active prefrontal cortex regions that help regulate and control our emotions. Serotonin is an inhibitory neurotransmitter set in place to balance excitatory neurotransmitters, such as dopamine.
Lower levels of serotonin can lead to depression, sleeplessness, and indirectly affect the ability to inhibit rash actions such as violence. Proven in numerous rat and human studies, serotonin deficiency leads to reduced activity of the frontal lobe, weaker connection between the frontal lobe and amygdalae, and high levels of aggression. MAO-A, or monoamine oxidase A, is an enzyme involved in the breakdown of neurotransmitters such as dopamine and serotonin. MAO-A deficiency is a rare disorder that occurs exclusively in males and also damages one’s ability to control their impulses. Beyond biology, children with reactive aggression are more likely to have social information processing deficits and have been physical abused.
Comparing PET scans of the brains of “normal” (law-abiding) controls, reactive murderers, and proactive murderers, it has been found that both proactive and reactive murderers have more activity in the subcortical limbic regions of their brain. This region includes the thalamus, the amygdalae, and the hippocampus, where aggression is stimulated and modulated (think back to the structures I focused on in my ‘neurological roots of racism’ research).
Remember how those impulsive criminals have poor prefrontal cortex functioning? When reactive murderers are riled up, they cannot help but retort immediately in aggravation. As you can see up above, their frontal lobes are green whereas the normal control and proactive murderer scans show yellow and red, signs of clear activity. Thus, proactive murderers have the prefrontal capabilities to express their aggression in a premeditated manner. They regulate their emotions, but only enough to be able to carefully plan and carry out assaults. This is ultimately what differentiates proactive murderers and their predatory approach of stalking and killing their victims to reactive murderers who retaliate when provoked.
From all this research, it's clear to say that proactive aggression and reactive aggression are quite different from each other and stem from varying biological factors. In my next posts, I will be furthering my research by looking into biomarkers, psychopaths, and antisocial behaviour.
Thank you so much to everybody who has taken the time to read this long post!