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Behind Closed Doors: Psychology Behind the Making of a Serial Killer

October 15, 2020
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Abstract: The human mind has long been a mystery, able to disguise the most rotten characters from public scrutiny. Killers like Ted Bundy, Jeffrey Dahmer, John Wayne Gacy, and Ed Gein, were all once perceived as normal, even exceptional, in society’s eyes. Though we tend to focus on their evil deeds, we do not often ask ourselves why, or how, these individuals decided to become the despicable, infamous serial killers they are known as today. To better understand how potential perpetrators become full fledged killers, scientists dove deep into the psychology behind the outer persona, discovering similar genes in the brain and traumatic childhood events of such individuals who may exhibit proclivities for future violent tendencies. A combination of neuroscience and psychology studies have revealed the underlying clues  that any average person can become a bloodthirsty serial killer. While they may be able to keep up a calm, charismatic exterior and easily blend into our society, they may be capable of hunting down the vulnerable to satisfy their own sick, twisted desires.

Keywords: MAOA, serotonin chromosome, psychopath, psychotic, sociopath


I. Introduction

Jim Fallon’s Ted Talk, “Exploring the Mind of a Killer,” offered a plethora of scientific information about both the mind of a serial killer and recent findings in neuroscience. Specifically, he talked in depth about the Monoamine Oxidase A (MAOA) violence gene that is commonly found in killers. In this paper, I will discuss his scientific findings along with other external factors that affect the psyche of  these murderous human beings otherwise described as psychopaths. According to Fallon ,  a neuroscientist at the University of California, over 90% of convicted serial killers are observed to have a particular gene that triggers violent behaviors. This gene, known as MAOA, has different variations.  Moreover, . the MAOA enzyme,coded by the MAOA gene, catabolizes serotonin, norepinephrine, and dopamine. Some researchers have concluded that low MAOA density in certain regions of the brain may contribute to psychopathology but further research still needs to be done (Kolla 2017).  Others have focused on studies that show youth having a long allele of the serotonin transporter gene in the presence of environmental stress can exhibit interpersonal and affective traits of psychopathy (Sadeh et al. 2013).  In this paper, I will focus mainly on the influence of serotonin which is . a chemical produced by nerve cells, sending signals across those cells, otherwise known as a neurotransmitter. In the case of psychopathy, serotonin’s most important function is to regulate mood and social behaviors. A lack of serotonin, therefore, will offset the psychological balance of the human brain.


The MAOA enzyme is a mitochondrial enzyme that is encoded by the x-chromosome linked MAOA gene.  MAOA can determine aspects of human personality and thereby can increase the risk for personality disorders. Variations in the MAOA gene and the MAOA enzyme levels have been linked to antisocial behavior and aggression (Kolla 2017). Furthermore, low MAOA density in regions of the brain may contribute to psychopathology although environmental influences must also be considered..  Researchers have found that males displayed signs of extraversion of this gene at age 16, which continued to develop through their late 20s. This result was expected, as most genetic effects, especially those of more complex traits, are most strongly developed during the late childhood and early adulthood years.  (Xu et al 2019.). 

The MAOA gene is only one of two main factors that contribute to the makings of a future serial killer. An extra amount of serotonin in the brain during developing stages is also a factor. Ironically, normal amounts of serotonin are supposed to make the human body calm down. However, combined with the MAOA gene, the brain overloaded with serotonin, can eventually become insensitive to this chemical. This is equivalent to having a car without brakes causing desires in the brain to run wild without any mechanism to stop them from spiralling out of control.

Xu et al. (2019) expounds on this important point in their study, “Monoamine Oxidase A (MAOA) Gene and Personality Traits from Late Adolescence through Early Adulthood: A Latent Variable Investigation.”, The data in this experiment aligns with the statistics presented by Michaud and Aynesworth, successfully tying together the neuroscience and psychological portions of my paper.

Both these factors are phenotypes, genetic information that has not yet been expressed externally, in behavior or on the human body. In the book The Only Living Witness, Michaud and Aynesworth are a reporter and an investigator team reveal -that all killers need a trigger, most times taking the form of a traumatic childhood event (environmental factors) that results in physical damage to the brain. 74% of serial killers underwent mental abuse and 42% underwent physical abuse during their childhood years. Most likely, those events leave the child prone to injury, with 29% of convicted serial killers having suffered some sort of head trauma. Children mimic what they see, with their mental states not yet fully developed. With 43% of future killers suffering through sexual abuse and 35% witnessing such acts as a child, it is no surprise that those unforunate children grow up to be the monsters they’ve suffered under all those years. To block out childhood trauma, most killers in turn develop psychopathic behaviors as a coping mechanism (Michaud 2012). 


The term ‘psychopath’ is commonly misunderstood among the general public; most people seem to associate it with crazy, or disarray, the complete opposite of the true definition. Psychopaths cannot feel love, but they can have strong feelings over their possessions. James Blair,claims that psychopaths are extremely good at hiding their tendencies and dark urges, able to blend in with society as just another normal member (Blair 2013); this often comes as a shock to most. 

Blair (2013) introduces a new concept toreaders by highlighting the point that psychopaths are often inaccurately depicted as crazy, visibly unstable people and that society has the misconception they behave in accordance to this myth  in real life. Blair explores the truth behind psychopathy, offering information that most people have never thought about. Blair  claims psychopathy is easy to hide.  He had also previously noted that psychopaths can be insensitive to cues of punishment as well as insensitive to others in distress which is relevant and important to the underlying discussion in this paper.The most horrifying fact is that psychopaths understand how charismatic they can be, thereby using their charm as  their modus operandi. In his book The Encyclopedia of Serial Killers Second Edition, author Michael Newton comments that  those “predators in human form” who have long been hidden in society, are invisible to the naked eye until they strike. Newton’etail about the lives of infamous killers.  He goes into depth about the influencing aspects in these psychopaths’ lives that played a role in shaping them into who they become. For example, he noted parental abuse, and head trauma as two common factors that many killers shared.

One of the main factors that is emphasized by Newton is the extent of their “psychopathic charm”. Ted Bundy wore fake casts to appear weaker in front of unsuspecting young women (Brogaard 2012)(Newton 2006). Jeffrey Dahmer coaxed his victims into a drunken state before having his way with them (Michaud 2012). Edward Gein was well known around his town as the “helpful man,” successfully using his reputation to cover up what happened behind closed doors (Newton 2006). These psychopaths often understand the extent of their heinous crimes, and yet feel no remorse when caught. 

In the Ted Bundy tapes, for example, the famed killer chatted with the interviewer as if they were old buddies, completely ignoring the current circumstances. By observing different patterns in human interactions around them, psychopaths are able to mimic those actions, allowing them to appear perfectly sane to the eyes of the public (Michaud 2019)(Newton 2006). The live, broadcasted interview with infamous serial killer Ted Bundy proved how “normal” murderers can act. Even with all the cameras, Bundy was still able to hold a clear, casual conversation with the interviewer, as if they were friends. It’s not often that we get to observe the actions of a killer, and this is one of those rare moments in history that contains a dark, rotten core. However, seeing Bundy’s casual behavior supported my previous claims in the paper about psychopathic traits and how easily they can be hidden from the public.

Blair (2001) has suggested that reduced amygdala functioning is a key biological factor in psychopathy.  This supports the finding made by Hariri et al (2002) in using functional magnetic resonance imaging (fMRI) to explore the connection between genetic variation in the serotonin transporter gene and brain activity.  It has been suggested  by Heinz et al. (2005) that the genetic variants of the serotonin transporter gene  are linked to the amygdala functioning.  Furthermore, the reduction in amygdala activity in the presence of a long allele of serotonin transporter gene appears to suggest a potential risk factor for development of psychopathic traits (Glenn 2011).

While only some serial killers may exhibit manipulative psychopathic behaviors, most of them are also ‘psychotics,’ a completely different classification from ‘psychopathic.’ Berit Brogaard, a PhD and director of the multisensory research at the University of Miami, further explores the psychotic traits in her article “The Making of a Serial Killer: Possible Social Causes of Psychopathology.” Though there are overlaps, such as “blunted emotions,” psychotics lack a touch with reality, existing in a constant state of hallucination, not aware of their surroundings (Brogaard 2012). They may hear a voice in their head, continuously force feeding them false ideologies about the world around them, motivating them to commit unspeakable deeds. With this given information, unsurprisingly most convicted serial killers have been diagnosed with psychotic diseases, such as schizophrenia and bipolar disorder, both of which negatively impact the mental state of the human brain.


Serial killers do not simply pop out of the womb feeling murderous; there are many factors throughout their lives that impact the way they think, act, and feel around others. While these traumatic events should not make society feel any sympathy for those who take the lives of others, it is interesting to piece together similarities that change a normal human to a cold-blooded killer.

One factor in explaining this complex disorder may be hidden in the brain and the MAOA enzyme.  Specifically, along with a broad spectrum of environmental influences are the epigenetic factors that may determine the decreased activity of MAOA and long allele of serotonin transporter gene..


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