Nature vs Nurture in Context

Portrait of a Killer: Nature vs. Nurture and its Relation to Homicide Offenders

On April 20, 1999, Eric Harris and Dylan Klebold opened fire on Columbine High School. The pair murdered twelve students and one teacher before killing themselves (Brooks). This tragic incident of mass homicide led to a number of controversial and disturbing questions, many of which centered on the larger, ever-present issue of nature vs. nurture. Were the murderous intents of Harris and Klebold the result of a difficult home and school environment or genetic predispositions that unfolded according to a biological plan?  This ongoing question of the scientific and sociology worlds has evolved over the years and numerous theories and ideas have attempted to respond to it. As it stands now, most scientists and theorists agree that the important thing is to realize that there may be no clear-cut answer and that both genetic tendencies and environmental influences compose an entire human being. Understanding and appreciating that genetics, environment, physiology, and psychology all influence a person’s predisposition to commit a crime like murder is vital in considering how to prevent these crimes from becoming realities.

The nature-nurture debate is nothing new; in fact, it was born alongside modern science during the Renaissance period. During this time, the prominent French scholar Renee Descartes proposed the idea that most refer to now as Cartesian Dualism, which suggests that physical matter and the human mind are separate entities. According to this theory, physical matter is subject to the laws of science while the human mind does not abide by any natural law (Pinel 20). This concept remained the basis of scientific thought for some time until modern science proved that some behavior has a biological basis and some personality traits are passed down through genetics; the two sides of the dualism began to intertwine. Today, as the fields of neuroscience and psychology continue to develop, one can easily see that Cartesian Dualism has its flaws.  Textbook authors Carol Sigelman and Elizabeth Rider propose that the question therefore is not nature or nurture but “how biological forces and environmental forces interact to make us what we are” (Sigelman & Rider 5).

Although research has convinced scientists that nature and nurture interact to influence personality traits, convincing the general public of this is not always an easy task. In the mid-1970’s, the nature-nurture debate became political after Edward O. Wilson fathered the branch of science known as sociobiology, which studies the influence of genes on behavior. Wilson’s “left-wing colleagues” attacked him for threatening equal rights and justice with his suggestion that humans are born with genetic tendencies, rather than as blank slates.  Since then, New York Times writer Nicholas Wade asserts, many people remain uncomfortable with the fact that genes can predispose a person to “politically sensitive aspects of human nature,” like aggressive or criminal tendencies. Today, armed with increased knowledge as well as the Human Genome Project, psychologists and biologists alike stress that genes do influence behavior, but our experiences and interactions are ultimately our destiny (Malmquist 68).  Hence, the debate should be whether to emphasize nature or nurture in attempting to understand the complexities of human development.

The constructivists, who stand on the nurture side of the debate, emphasize environment, learning, experience, and cultural influence when explaining how people grow (Sigelman & Rider 6). This school of thought, also known as behaviorism, dominated psychology through the 1950’s, when “environmental conditions were seen as always controlling  behavior,  beyond some basic motor patterns for reflexes” (Malmquist 45).  Sigelman and Rider define environment as “all the external physical and social conditions, stimuli, ad events that can affect us. . . “(5). Constructivists also suggest that individual learning processes guide development, rather than universal maturational processes; thus, experiences have more of a hand in creating a human being rather than genetics. Additionally, nurture points to a person’s physical environment to explain his behavior or illness; for instance, a person exposed to lead paint may be intellectually stunted while early stimulation can greatly increase a child’s IQ (5). Finally, a person’s culture plays a part in his personality and dispositions; for instance, looking at what different cultures emphasize in school can explain much about a person’s intellectual capabilities.

Those that emphasize the nature side are called nativists. Guided by biology and psychoanalytic theories of instinctual behaviors, the nature side of the issue emphasizes four key factors that guide development: heredity, maturation, genes, and biological predispositions (Sigelman & Rider 6). Maturation refers to a genetically-influenced patter than “[guides] us all through many of the same developmental changes at about the same points in our lives, which individual heredity endowment is making each person’s development unique” (Sigelman & Rider 5). During this maturation process, a person’s genetic predispositions guide his personality, actions, and vulnerability to disease. The nature side also refers to the biological processes that control behavior, such as hormones like testosterone (which fuels aggression) and neural structures, such as the amygdala (which helps regulate the emotion of fear), to explain the way a person acts. 

Before discussing the relationship between the nature-nurture issue and murder, it is necessary to understand the specificities of this crime. The Oxford Dictionary of Law Enforcement defines murder as “homicide that is neither accidental nor lawful and does not fall into the categories of manslaughter or infanticide” (248). Therefore, when examining those who commit murder, one must observe only those who committed murder with intent. Identifying the intents and backgrounds of these offenders is also essential because it allows us to understand what led to their behavior and how to prevent it in the future (Laajasalo & Haakanen 452). The background statistics of murderers have led to three key points of research: gender, psychopathology, and socioeconomic status, which help us to understand who is at risk for violent behavior and exemplify the roles played by nature and nurture in that behavior.

Carl Malmquist’s book “Homicide: A Psychiatric Perspective” cites gender as one of the nine epidemiological variables that are significant to homicide rates; data suggest that men commit 86 % of homicides (6). It is common knowledge that men tend to be more aggressive than women, which begs the question: is this due to inborn biological tendencies or society’s stereotypes of men being hostile fighters? As usual, the lines between nature and nurture in this issue are hopelessly blurred.

One can make a case for the influence of nature in gender typing by looking at the prenatal processes of sexual differentiation. Each fetus begins with a chromosomal pair of either XX for girls or XY for boys. However, these fetuses look largely the same regardless of their genetic gender until hormones step in, creating masculinized and feminized brains with either an influx of testosterone or estrogen (Pinel 327). Because testosterone dominates the brains of males, even before birth, they tend to be more aggressive and hence more likely to engage in violent acts. One study of 700 male prison inmates found that high-testosterone inmates had committed more violent crimes than low-testosterone inmates, thus showing that the hormone has a correlation with hostile behavior (Lippa 131). An additional case for nature lies in cross-cultural studies which show that, even in countries where emphasis on gender role is not as prevalent as it is in the U.S., boys still show higher levels of aggression than girls (Sigelman & Ride 6). It is obvious that genetic make-up has a great deal to do with basic gender identity, but it does not explain everything about how a person fits his or her gender role in society.

Biological theories explain some innate sex differences, but they do not account for the role of social environment in individual sex differences (Lippa 104). For example, it is easy to say that all men are more aggressive because of testosterone, but interactions with different individuals in everyday life prove that this is simply not the case. Social learning theories, cognitive theories, and social psychology theories attempt to explain gender and its relation to tendencies like aggression or criminality from a nurture perspective. Social learning theories suggest that the differing behaviors of men and women are due to individual learning experiences and observation (Lippa 104). A little boy who receives a reward for rough play or assertion and a punishment for doing activities considered feminine will learn to stay away from such activities and continue being assertive and playing rough; this exemplifies the phenomenon of operant conditioning. Cognitive theories, on the other hand propose that gender typing occurs in stages as children’s cognition skills develop, much like Piaget’s learning theory (Lippa 107). Finally, social psychology theories point to gender-role stereotypes and cultural norms in gender typing. Environment does seem to play a role in influencing gender-types traits. America is a more violent country that emphasizes the “tough” male stereotype, as evidenced by superheroes and strong men fighting off villains to save the damsel in distress (Lippa 159). The U.S. also has a higher homicide rate than most countries that do not have such stereotypes of men. These two facts seem to have an obvious correlation.

Gender is definitely a background to consider when looking at the background of a murderer, but it does not explain everything. Psychological disorders can override any influence of hormones or gender role stereotype. While psychological disorders are very different from clinical disorders in that they are psychological rather than physiological, they do have a genetic component as well as environmental causation. Developmental psychologists have found a diathesis-stress model useful in explaining how psychological disorders develop.  This model attempts to explain how the interplay between biological, psychological, and social factors produces psychological disorders over time. Diathesis refers to a predisposition based on “genetic makeup, physiology, cognitions, personality, or a combination of these. A person who has this predisposition is more likely than a person without any predisposition to develop a disorder following a stressful experience. Constructing diathesis-stress models for different psychological disorders allows researchers to better understand the development of psychological disorders that trigger violent or unpredictable behavior (Sigelman & Rider 472-473). ). It is uncomfortable to think that somebody may have a psychological disease somewhere in his genome, but it is reassuring to know that, unlike most clinical diseases, one can prevent these disorders with early intervention. ).

Personality disorders in particular are present in a significant number of murderers; in one study of seventy-seven offenders, nearly half (42%) had a personality disorder, primarily antisocial personality disorder (Laajasalo & Hakkanen 452).  Because of its relation to criminality, clinical researchers have studied antisocial personality disorder more than any other personality disorder (Gray and Zide 293). The results have shown a genetic component to this order, according to twin and adoption studies (Hanlon et. al. 3). However, a look at the case of Luke Rossey suggests a definite environmental factor to antisocial personality disorder. As a young boy, Luke Rossey dealt with teasing by the other boys for his size; fed up, he killed the boys’ dogs and drowned a kitten in order to send a message (Gray and Zide 296). Luke always seemed to be in trouble, according to his sister, but he became especially uncontrollable following this act and went on to live a life of violence and crime (296).  In addition to experiencing bullying in childhood, the boy’s father was an alcoholic who left the family (Gray & Zide 293). This case study excellently exemplifies the diathesis-stress model as well as the importance of solving the problem before it is too late.

While gender and psychological disorders are largely unavoidable, some background characteristics of murderers result from more than just chance. Additional investigation of the backgrounds of homicide offenders helps researchers to understand the etiology of violent tendencies; these background characteristics also exemplify additional nature-nurture interactions (Laajasalo & Hakkanen 472). Alcoholism is one illustration; alcohol is present in 54% of homicidal acts and 20-40% of homicide offenders are diagnosed alcoholics (Malmquist 16). The significant links of alcohol to violence have led to controversies about whether or not to count alcoholism as a disease, thus making the inference that “individuals who are biologically vulnerable to the effects of alcohol should not be seen as responsible for their violent acts committed under the influence” (Malmquist 15). Constructivists in this debate argue that the culture ideas associated with the effects of alcohol leads to violence, rather than the physiological effects of the drug (Malmquist 16). Alcoholism does have several biological factors; a person can inherit the disorder or have a genetic predisposition to become heavily addicted to alcohol (Laajasalo & Hakkanen465). However, there a number of environmental factors that go into alcoholism; for example a child who grows up watching his parents have a drink every night at dinner will see drinking as an acceptable norm and may be more likely to experiment with it. Some factors are a combination of nature and nurture; the parents described above may have also passed on genes that predispose their child to enjoy the taste and feel of alcohol. Thus, some people are vulnerable to the effects of alcohol, but alcoholism depends on a number of biological, environmental, and cultural factors.

One last background characteristic of murderers to note is socioeconomic status. Research has found significant correlations between socioeconomic status (SES), as well as education level, to the likelihood that a person will commit murder. One study found that over 45% of offenders had school problems and 46% were unemployed (Laajasalo & Hakkanen 458). Factors associated with low SES, such as household crowding, are also worth noting. One 1980’s study found that homicide rates tripled as rates of household crowding exceeded 20% (Centerwall 814).  Although intelligence is an inherited trait, researchers have found that lower IQ does not necessarily correlate with likelihood that a person will become a criminal (Laajasalo & Haakanen 459). Those with “school problems” simply had a lower education level or had dropped out of school (Laajasalo & Hakkanen 453). This particular variable, then, is evidence of the environment’s role in violent tendencies; even with their genetically-endowed potential for intelligence, people with the “school problems” described in Laajasalo and Hakkanen’s study came from an environment that did not allow them to effectively reach that potential. Similarly, low SES creates an environment full of stress and negative social stigmas that build a number of negative traits, such as aggression. Hence, although nature does affect intelligence and other personality traits, an unsuccessful environment can change those traits for the worse.

Eric Harris and Dylan Klebold, the Columbine killers, both had psychological disorders, a “nature” factor; they also allowed a violent Goth subculture to influence them, a “nurture” factor (Brooks). There are no clear lines between the influence of nature and the influence of nurture in the carrying out of this act. In order to prevent violent crimes, it is vital to realize that people are neither blank slates nor slaves to their genes. Genes simply give the individual potential while environment makes that individual a unique human being. A number of factors go into the background of a murderer; however, armed with knowledge of both genetic and environmental factors, there are plenty of changes to manipulate these factors for the better. Imagine an environment where parents and caretakers took a child’s genetic predispositions into account while optimizing his environment in order to rear him. Some simple changes in environmental factors may prevent another Columbine, another life lost, or another life spent behind bars.

 Works Cited

Brooks, David. “The Columbine Killers.” The New York Times 24 April 2004 nat’l. ed. A17

Centerwall, Brandon. “Race, Socioeconomic Status, and Domestic Homicide, Atlanta 1971-72.”    American Journal of Public Health 74.8 (1984): 813-815. Print.

Gooch, Graham. A Dictionary of Law Enforcement Oxford, NY: Oxford University Press, 2007.Print.

Gray, Susan and Marilyn Zede. Psychopathology Belmont, CA: Cengage Learning, 2008. Print.

Hanlon, Robert E. et. al. “Neuropsychological Features of Indigent Murder Defendants and

Death Row Inmates in Relation to Homicidal Aspects of their Crimes.” Archives of Clinical Neuropsychology 25 (2010): 1-13. Print

Laajasalo, Taina and Helina Ha’’kka’’nen. “Background Characteristics of Mentally Ill Homicide Offenders: a Comparison of Five Diagnostic Groups.” Journal of Forensic Psychology 15.3 (2004): 451-474. Print.

Lippa, Richard A. Gender, Nature and Nurture Mahwah, NJ: L. Erlbaum, 2002. Electronic book.

Malmquist, Carl. Homicide: A Psychiatric Perspective Washington, DC: American Psychiatric Press, Inc., 1996. Print.

Sigelman, Carol and Elizabeth Rider. Lifespan Human Development 6th ed. Belmont, CA: Cengage Learning, 2009. Print.

Wade, Nicholas. “Steven Pinker; In Nature vs. Nurture, a Voice for Nature.” The New York Times 17 September 2002. Nat’l. ed. F4+

 Note: This was a research paper for my final in a Rhetoric class.