Serial Killers; A Multifactorial Discussion of Etiology

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  • Author Robert Depaolo
  • Published March 28, 2022
  • Word count 4,408

Serial Killers: A Multi-factorial Discussion of Etiology

by Robert DePaolo


This article discusses the behavioral dynamics of serial killers in terms of several disciplines including psychology, linguistics, anthropology, sociology and neurology. Conclusions are drawn with respect to the development of an obsessive desire to kill. The argument is presented that explanations based on analysis of "triggers,' childhood upbringing and lack of a conscience (i.e. superego mal-development) are insufficient to explain why individuals engage in this kind of behavior. The general theme here is that a combination of occurrences and predispositions must be in place to lead to aggression and the excessive need for domination seen in murderous sociopaths. This includes a phenomenon referred to as "hypo-speciation') - a diminution of victims to below human status that enables the killer to override guilt (DePaolo 2021).

A look at the lives of serial killers presents both discrepancies and commonalities with respect to their motives, background and behavior patterns. Such discrepancies are seen in the most notorious members of this group: including Jeffrey Dahmer, Ted Bundy, Gary Ridgeway, Albert DeSalvo, John Wayne Gacy and Dennis Rader.

There are also commonalities, which has been documented through psychiatric evaluations, books, and statements made by the killers themselves. It appears their acts all combined aggression with the sex drive and featured a defense-based need to control people whom they feel could otherwise control them (as a result of their tentative levels of self- esteem and the concomitant threat of rejection). Each act involved targeting victims in the aftermath of lengthy surveillance and stalking, and sexual intercourse with the deceased victim (necrophilia).

However, there are also differences among the killers. DeSalvo murdered older women as well as young women (White, 2015). Bundy murdered college age women but also preteens (Rule 1980). Dahmer victimized young males to satisfy his homosexual desires (Schwarz 2021) and Rader killed parents and their children.

The difference in victimology suggests a prominent factor might have simply been the availability of the targets. Bundy's victims were mostly petit women, easily overwhelmed. The targets of Dahmer and Gacy were young males who could easily be overcome physically, and in the case of Ridgeway, it involved killing prostitutes almost exclusively, who were strangled during intercourse when they were in a defenseless position. In a sense, all these acts resembled the hunting strategy of a predator who selects the weakest member of a pack. In each case the killer seemed to be maximizing his chance at completing the act, which suggests (despite theories of victim typology) it was the act of killing per se that was the goal, and that convenience was a prime motivation.

Sexual gratification was part and parcel of the act for these killers, but even here there are variances. DeSalvo was aroused by older women. Rader and Bundy engaged in sexual activity with pre-pubescent young girls and Dahmer and Gacy picked young male victims they felt were vulnerable. (Linedecker 1993)

That raises several questions; for example, why is killing so necessary to these individuals? Secondly, why is sexual gratification derived from killing the sexual "partner," bearing in mind that many serial killers, particularly Bundy, Rader, Dahmer and DeSalvo engaged in intercourse with their deceased victims? To address those questions, it would seem helpful to delve into several influences on human behavior that arise not just in extreme but also general circumstances.

First, it is necessary to assert that humans derive from a primate line. We are not descended from apes, as goes the colloquial interpretation, but we do apparently come from an ancestor common to both humans (and hominids) and arboreal primates - possibly an ancient upright walker known as Ramipithecus (Bali, 2022). In the primate world, social organization is typified by male dominance. In both chimpanzee and Gorilla societies the alpha male controls sexual practices. Moreover, his dominant status makes him attractive to females. It is a genetic process that ostensibly guarantees the strongest genes will be passed onto the next generation.

That doesn't mean only dominant males will mate, but it takes cunning and intelligent opportunism for lesser members of the group to attract females - as well as a certain amount of sexual urgency on the part of females who realize the estrus period is brief.

That means humans have some tendency to pair up sex with male dominance. It is not just an evolutionary process. Sexual readiness comes about through neurochemical uptake so that dominance comes about through an increase in testosterone and norepinephrine. That means in the most basic neuro-behavioral context, there is an interrelationship among sex, dominance and aggression. That might explain why, according to federal crime statistics, there are, on average roughly 1800 instances annually of men killing women in the U.S.

Most humans can modulate their impulses so that aggression does not spill over to the sex act - which for our species is predominantly a tender, empathic experience. However, the potential for that spillover exists within the human genome and within our basic physiology, particularly within human brain circuitry.

The appetitive and sexual centers in the brain's limbic ring (a circular midbrain structure) are adjacent to and innervate one another. The hypothalamus regulates sexual and appetitive drives. It sits next to the amygdala - a center that regulates rage and aggression. (Bailey, 2018) This is fortuitous, since the act of hunting and killing prey is prerequisite to eating form many creatures. In that context, one might conclude (in somewhat oblique fashion) that the interaction and neural spillover effect of sex, dominance, aggression and appetite is adaptive.

An analogous neural spillover relationship can be seen in the proximity of neural pathways connecting finger and hand movement and the movement of the tongue that enables us to employ manual gestures as well as vocalization to enhance communication. Thus, while many neuroscientists discuss the brain in terms of specific locations and functions, for example, the hippocampus for memory storage and consolidation, the cortical occipital lobe for visual processing and Broca's area for language expression, many human activities involve integration of a variety of neural circuits, which can both facilitate actions and at times interfere with them.

Most of us have the capacity for reciprocal inhibition (a process in which one brain circuit can selectively block the activity of another) so that amygdaloid circuits do not spill typically over to the hypothalamus and pair up sex with violent behavior. Obviously that spillover does occur with serial killers. That doesn't mean serial killers suffer from organic dysfunction - they typically do not. For example, Ted Bundy’s neurological exams were normal as determined by E.G.G and MRI workups. However, neither of those instruments can determine a cross wiring anomaly. They can determine whether neural structures are intact but not "where they go." With billions of neural interconnections in the brain that would be an impossible task.

Such cross-wiring anomalies can occur through childhood experience when limbic-cortical connections are established. During early childhood sex can be paired with aggression to the point of becoming a Guthrie-esque, immutable associative bond. In not being able to utilize sophisticated defense mechanisms and cognitive parsing skills, a young child will tend to incorporate sex and violence into an associative mindset rather than reject it. In such instances, the pairing of sex with aggression can become an unconscious process - a nearly reflexive type of learned habit that is effectively unattributable to the child.

That might explain why most serial killers are unable to really explain why they pair up sex with violence. Their horrific actions arguably reflect childhood regression. That might explain why Ted Bundy - a man who seemed intelligent and attractive - had to resort to serial murder to satisfy his sexual and social needs. It wasn't the adult law student and articulate bon vivant doing the killing but rather the child who was “father to the man” known as Ted.

Some traits of serial killers include compensatory dominance, whereby an extreme sense of inferiority clashes with a self-contrived sense of superiority. That dynamic, which is line with Adlerian theory, (Orgler 1976) leads to a psychological balancing act. In response to extreme bouts with feelings of inadequacy the compensatory swing will be equally extreme (even in conjured up in fantasy) which will raise the level of superiority by the serial killer to such a degree that other people are, by comparison, deemed sub-human, making the kill no more guilt-inducing than that of a deer hunter. Such an equating of a human victim with an animal (hypo-speciation) can often be seen in the early acts of animal torture typical of many serial killers.

Does that mean childhood experience can produce neurological pathology? Neurological workups of Ted Bundy and others tended to be normal. However, as discussed above, while there might not be discernible neuro-pathologies there could be faulty interconnectivity, possibly due to fragmented connections between the self - regulatory frontal lobes and mid brain emotion circuits.

There is an ironic process at work in those pathways. The frontal lobes are responsible for self- monitoring, self-regulation and arguably provide a mechanism by which the conscience develops. The frontal cortex has more connections to other brain sites than any other network in the human brain. (Hoffman 2013) That is why self-control is the rule, rather than the exception for our species. On the other hand, when those pathways are skewed, interrupted as a result of childhood experiences or lack sufficient communicative coordination (are dyspraxic) a level of control will be lost, and potentially lead to unfathomably brutal behavior patterns.

The fact that neither DeSalvo, Bundy, Gacy, Rader or Ridgeway could articulate the reasons for their actions suggests the impulse to kill does not typically arise from cognitive schemata. That level of awareness might lead a person to be aggressive against another for a specific reason (perhaps revenge, the perception of threat or even momentary rage as in the case of manslaughter) but it does not seem to be involved in the actions of a person who kill repeatedly.

As discussed above, such pathological connectivity could be related to childhood experiences. This could include identification with a violent male role model in early childhood. That is because identification is mandatory for so social a creature as Homo sapiens. The need for social bonding is intense enough, and probably derived from evolution that it cannot distinguish the good from the bad. Any child will tend to be a psychological reflection of his caretakers.

It could also be induced by obsessive self-talk/programming whereby the serial killer spends time contemplating and justifying his rage so often as to block out external inputs, including the social taboo against violence, the importance of empathy and other factors that would otherwise contribute to superego formation. In other words, the kind of psychopath who engages in serial murder might not suffer from lack of empathy per se. Instead, he might be so caught up in super-empathy for himself due to the perception of threat from his victims, or their typology, as with Bundy, who had an extreme fear of rejection by females and Dahmer, who feared abandonment and kept his victims in a semi-animated state after death so they couldn't leave him) as to block out the external social environment. Interestingly, the usual stereotype of the serial kill is of a highly intelligent individual. That is not necessarily true. However, anyone who can rely on his own internal language appraisals to sanction murderous actions would have to be extremely verbal and ironically, capable of pristine logic. Otherwise, he would not be able to persuade himself to engage in such brutality. In watching interviews with Bundy, Rader, Kemper and Dahmer this writer became impressed with their language skills. Despite their obvious savagery, they came across as professorial.

Yet, many people are verbally gifted experience rejection and fear abandonment but do not engage in serial murder. Perhaps that is because the concerns of some psychopaths are more external. They do not engage in self-programming and cannot block out the outside world they are so invested in manipulating.

Self-talk can provide justification for the acts of serial killers. After all, some have defined the conscience as a process by which one engages in self consultations about right and wrong. Even though, as Freud suggested the superego is formed through parental and societal inputs, the values must eventually become internalized and self- regulated. Negative self-programming would seem to operate along similar lines.

That seems to have been the case with Bundy, Gacy, Rader and Dahmer, who did not show overt signs of anger and did not seem to develop their pathology as a result of family discord or other externally induced traumas but did spend a lot of time in either physical or psychological isolation. Self-programming is doubly ominous because it not only prevents early identification of the serial killer's violent potential, but also enables the internally driven killer to become increasingly violent and socially detached even if, like Bundy he does interact with people on a regular basis. As long as inner commentary dominates, his real motives will be undetectable.

There are sociological factors to consider as well. Many of the episodes of serial murder occurred in the time between the 70s and 80s in the USA, particularly in the cases of Bundy, Ridgeway, Gacy and Rader. It was a time when women were asserting their independence, including in the area of sexual liberation. Most men adapted to the changes, not just out of a sense of compassion but out of necessity - many women were either breadwinners or at least significant co-contributors to the household income around this time. For some males, this presented a clash between their belief in dominance over females and the realities of the workplace and social mores per se. In that sense, the acts of these predators could be presumed to be, among other things, a protest against changing times.

Despite all these causative factors, most males do not murder females. Indeed, built into the social code for many years was the dictum...never hit a girl (or woman). Part of this was based on the perception that females are generally smaller and have less muscle mass and that it was cowardly to harm someone weaker than yourself - an instance in which the much-maligned macho ethic served to mitigate against male on female aggression. The question then becomes; why do some incredibly small percent of males engage in such horrific behavior?

Since all serial killers have existed within the same societal structure as the rest of us, it seems there must be an extra-social causative element pushing them over the top. There are many psychopaths in society, but most do not kill. There are many men who are rejected by females - like Bundy, but they do not kill. Many men have problematic relationships with their mothers - like Edmund Kemper, but they do not kill. All of which seems to argue against the "trigger," poor upbringing and sociopathy explanations of serial murder. In short something within the individual must be involved.

What might that be and how can we identify it before the damn breaks? That is not an easy question to answer, especially if one assumes part of the causation has to do with the killer using self-talk to prompt and sustain his acts of violence. To examine that issue it might be helpful to categorize them by trait and dynamics.

Bundy was an introvert, who was detached and alienated, even before discovering he was illegitimate. He seemed to identify with an abusive grandfather - the only significant male in his early childhood. As a toddler Bundy developed a fascination with knives. Later in his latency years he tortured animals and might have had his first "dry run at age 14 when he possibly killed a young girl named Marie Burr.

DeSalvo, married with a handicapped daughter, had a passive wife who spoke little English. He had a violent father who forced Albert to engage in sex with his sister and brought home prostitutes as his wife and children looked on. Albert was a loner with few friends, who felt estranged socially.

Dahmer was an introvert, who drifted away socially and began drinking in his teens as a means of drowning out his latent homosexual urges. He became socially isolated, which led to periods of rumination and anticipation of being rejected and abandoned. He killed his victims because he felt to unworthy that only by murder could he keep victims from "leaving him."

Gacy's father berated him for his effeminate interests as a child, expressing disdain for people who were less than masculine, which cast shame on his son – who, not coincidentally was named after John Wayne. That led to Gacy's hate for himself and for his urges, which resulted in his killing young male sexual partners/victims as a kind of self-nihilism.

Gary Ridgeway failed at several marriages, and in relationships with women in general. He developed an extreme sense of detachment and feelings of inferiority as a result of maternal rejection. Had a very secretive existence fueled by superego sidestepping, self-programming and a projection of his own guilt onto prostitutes, whose "evil allure" he deemed responsible for his own short-comings and lack of self-control.

Dennis Rader was a secretive man who sought positions of power in his community, showed no obvious signs of psychopathology but had deep seated, over-compensatory needs to not only conquer his victims but outwit the authorities. He sought sexual gratification with the youngest of his victims - a prepubescent girl.

In examining these trends, it seems several central factors stand out that have psychological, and anthropological ramifications. One is human nature. We are linguistic, hyper-social, dependent on interactions, social comparisons, social mores and social contact to sustain our emotional integrity. Since we cannot function in the absence of that influence social isolation can lead to various forms of psychopathology. Detachment, whether by actual separation or self-programmed alienation will tend to cause mental deterioration by precluding a social check and balance on impulse.

There must also be a severe oscillations between feelings of inferiority and self-contrived superiority that can, in the extreme instances, elevate the psychopath to God-like status. That would render others effectively sub-human, and thus enable the "hunter" to seek and destroy his "game."

Third, the hypo-speciation factor must be interesting enough to make objectification of victims pleasurable. Once they are rendered sub-human, the killer can become fascinated, rather than appalled at the site of dead bodies, and even find them sexually attractive. In such instances he will enjoy the look and company of the deceased. Physical aspects of their lifelessness, while to most would visually displeasing would overridden by the appeal of “company” who are non-threatening, compliant and in a strange sort of way 'serene" in the eyes of the serial killer.

Fourth, the killer must experience frequent, intense and unpredictable lapses back into feelings of inferiority - especially since the killer's pretense of ultra-dominance is contrived. Not being psychotic, the killer will recognize that the "God" he deemed himself to be is really a delusion. During episodes of realization, the killer is forced to exert complete control over the victim/sexual partner, which means only complete passivity by the deceased sex object (who cannot reject him) can be sexually satisfying.

A fifth consideration is a depression syndrome. Use of the word ‘syndrome’ - as opposed to a specific diagnostic term is due to the risk involved in multiple acts of killing. All reasonable people can understand the risk inherent in any act. This is particularly true when the act is criminal and when retribution can take the form of lengthy incarceration or the death penalty. Most sociopaths are considered legally sane and in the most basic sense, reasonable. Certainly Bundy, Dahmer, Gacy, DeSalvo and Rader and Ridgeway were. In that context one must explain why they were willing to take bold risks despite knowing there was a good chance they would be caught. Ridgeway trolled the streets at night, repeatedly hitting on prostitutes. He was a "regular John" who could have been easily identified. Bundy approached two women at Lake Sammamish in broad daylight with thousands of people around and introduced himself to his victims using his real name. Gacy killed in his own neighborhood, as did Dahmer and Rader. While it took a while to catch these men, none particularly went out of their way to avoid detection. Rader even engaged in ongoing conversations by letter with police and journalists during his killing spree.

The usual assumption is that the risk factor was related to the thrill of avoiding arrest and/or the quest for notoriety.

I believe a more central antecedent to risk taking was chronic depression. Boldness is often a function of a nothing to lose mentality. That doesn't mean the killers wanted to get caught and punished but it does suggest the thrill attraction on such a grand scale could have been a compensatory adjustment for purposes of counteracting extreme sadness. Since the depression was ostensibly chronic, risk taking would have to escalate further and further to blot out sadness.

Also. having to negotiate between the threat of inferiority and the need to re-invigorate compensatory grandiosity would have required constant effort and chronic vigilance; especially regarding the mental work resulting from inner thoughts related to self vs other comparisons. That would tend to produce a drain on energy. The fact that no permanent resolution could ever be found to erase feelings of inadequacy would eventually lead to the kind of depression associated with learned helplessness. It might explain why Bundy often said he was "bummed out" after a kill, and that he had to keep doing it to create renewed but only temporary gratification.

In fact, depression might be the most fundamental neuro-behavioral reason why a child can end up with poor superego development. For example, the frontal lobes are the latest neural circuits to develop - not reaching full development until young adulthood. For any brain structure to develop requires adequate and repeated neurohumoral transmission so that clear, functional pathways and inter-neuronal relationships can be established.

That is particularly the case with frontal development, because the connections between this site and other brain sites is complex and voluminous. If a child is placed in a helpless situation - for example being dependent on yet detached from or fearful of care his takers he will not have the cognitive skills by which to compartmentalize the experience. It will overwhelm him, and helplessness-fueled depression will become entrenched and compelling. Should that occur, there will be an accompanying depletion of neurotransmitters that could otherwise provide feelings of wellness and security. If frontal-limbic circuits are not properly "bathed" and carved out through catecholamine transmission normal connections will not be fully established. That could lead to many functions of the frontal circuits being delayed or diminished.

While there are undoubtedly other causative factors, it seems social detachment, extreme feelings of inferiority, and a depression-fueled need to sustain a compensatory sense of grandiosity are core elements disposing serial killers to engage in obsessive violence.

Still, many personalities feature similar dynamics but do not kill. Indeed, that is part of the morbid fascination with serial killers, who are all too often transformed by the culture into mythical figures over time. It seems reasonable to assume the creation of a serial killer requires a combination of neurological, psychological, anthropological and sociological factors. Just what proportion might be involved is difficult to tell but it appears no one component or trigger is sufficient to explain such behavior. It might be that, like many psychopathologies, sociopathy entails degrees of severity. It might also explain why serial killers are so rare and why it is so difficult to predict their emergence.

Since it is quite possible for neurological connections to divert from normalcy through either experience or undetectable developmental anomalies it is likely that faulty frontal to limbic wiring resulting from neuro-dyspraxia, depression and/or childhood trauma could provide the critical threshold leading to serial murder.

Perhaps that explains why most sociopaths do not kill. Some can be manipulative but also be adequately socialized, even if they do not feel the pain of others. Some might not have the time or inclination to self-program, possibly because they are not socially or psychologically isolated, have succeeded enough to avoid inferiority-superiority oscillations, or have vocational or personal habits and activities that take up too much time to stalk, plan and kill. And, perhaps most importantly, the more adaptable psychopaths might have essentially normal neural development.

Factors that lead an individual to become a serial killer might seem complex and beyond prediction. However, we do have a primate legacy disposing us toward dominance and a large brain that makes possible a spillover of appetitive drives. Such factors can lead some to believe in a world consisting of the strong and the weak, the dominant and the submissive, and in male and the female stereotypes.

That evolutionary legacy can run amok, absent social and psychological restraints, because while most of us deem the actions of a serial killer inhuman, human nature is complex enough for such potential to be manifest under certain conditions. It might seem trite to say we are all capable of heinous acts but there might well be a pathological mosaic that can lead to the creation of a monster who is both murderous yet a fellow who appears to the "nice guy who lives next door."


Bali, A. (2022) Difference Between Humans and Apes: The Evolution of Humans. Collegedunia

Bailey, R. (March 2018) The Limbic System of the Brain; The Amygdala, Hypothalamus and Thalamus, Science Technology Thought Co.

Blair, R.J.R. (Jan. 2013) Considering Anger from a Cognitive Neuroscience Perspective. Wiley Interdisciplinary Review of Cognitive Science

DePaolo, R. (2021) Bundy: A Clinical Discussion of the Perfect Storm. Abuzz Press

Harrington, R. (2019) Edmund Kemper: The True Story of a Brutal American Serial Killer. Independent Publisher

Hoffman, M. (March 14, 2013) The Human Frontal Lobe and Frontal Network System: Evolutionary, Clinical and Treatment Perspectives. S.R.N. Neurology

Linedecker,, C. (1993) The Man Who Killed Boys; The True Story of Mass Murder in a Chicago Suburb. St. Martin’s Press

Orgler, H. (1976) Alfred Adler International Journal of Social Psychology Vol. 22 (1) p. 67

Rule, A. (1980) The Stranger Beside Me: The Shocking Inside Story of Serial Killer Ted Bundy. Simon & Schuster

Schwarz, A. (2021) Monster: The True Story of Jeffrey Dahmer, Union Square and Company Publishing

White, D. (2015) Albert DeSalvo: The Boston Strangler True Crime Short Books 5

Robert DePaolo is a retired practitioner in the fields of clinical, educational and neuropsychology. He is a former professor of psychology in the NH University System and author of the recent books, Bundy; A Clinical Discussion of the Perfect Storm and From Evolution to God: An Integration of Faith and Science

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