Tuesday, 29 January 2013

Crime and Genetics

This is a paper I wrote in my 2nd year of Psychology degree on genetic inheritability of crime. It is hoped that this article can help others in their academic endeavors. As always, if you require the reference list, please get in touch, I'll be happy to provide you with the full bibliography.

Critically evaluate the statement that criminal behaviour is genetically transmitted

Theories pertaining to the genetic inheritability of crime are primarily concerned with a genetic physiological abnormality that can be attributed to the cause of criminality. Such theories employ methodologies that either examine the genealogy of the criminal i.e. twin, family & adoption studies or, examine the gene-environment interaction to elucidate the possible causes of criminal behaviour (Joseph, 2001). The subsequent article aims to expound genetic theories of crime and their worthiness, whilst also exploring alternatives in light of the nature/nurture debate in an attempt to gain a holistic understanding of this multifaceted issue.
Twin studies rely on the basic premise of comparing concordance rates of criminality between monozygotic (MZ) twins and dizygotic (DZ) twins. Since MZ twins develop from a single egg and are ‘identical’ in their genetic make-up, a greater concordance rate in MZ twins purports a noteworthy genetic influence on criminal behaviour. After studying concordance rates in 3500 Danish twin pairs, Mednick and Christiansen (1977) observed a 35% concordance rate in MZ twins compared to only 13% in DZ twins. Furthermore, a meta-analysis performed on 12 twin studies found 50% of the variance in measures of criminal anti-social behaviour was recognised as ‘genetically influenced’ (Mason & Frick, 1994).
Although the aforementioned evidences suggest a genetic inheritability of crime, there are certain shortcomings that need to be addressed. Twin studies commonly assume the experiences and environmental stimuli twins are exposed to are alike. However, Dalgaard and Kringlen (1976) contend that the greater concordance rate observed in MZ twins can be attributed to their shared environmental experiences. MZ twins are frequently raised via the same parental techniques/environment and Carey (1992) notes, for this reason, MZ twins imitate one another more than DZ twins. Thus, one MZ twin is a facsimile of another in almost every aspect, leading to an overestimation of inheritability in crime
Another methodological approach in studying genetics and crime involves the examination of intergenerational criminality in family studies. If crime is genetically bound, one expects a significant concordance rate between criminal parents and criminal offspring. Osborn and West (1979) studied the sons of criminal and non-criminal fathers. It was found that 40% of the sons that had committed felonies had criminal fathers compared to only 13% of sons with non-criminal fathers. Evidently, the genealogy of the individual is influential in whether he becomes a criminal or not. However, Ainsworth (2000) notes as the majority (60%) of sons with criminal fathers abstained from criminality; there must be other non-genetic (nurture) features.
Theoretically, adoption studies adequately separate genetic from environmental influences in that it separates the child from the biological parents. In a study conducted by Tehrani and Mednick (2000), adopted individuals who were born to incarcerated female offenders, possessed significantly greater criminal convictions compared to a control group. These particular findings suggest the genes of the individual outweighed the environmental influences in determining whether he/she would turn out to be a criminal. However, the notion that criminality is entirely dependent on nature is rebutted by Cadoret, Cain and Crowe (1983). Cadoret et al. collated statistics from three adoption studies to observe gene-environment interaction in adolescent delinquent behaviors. Results suggested antisocial behavior drastically increased when an adoptee possesses both a genetic factor and an adverse environmental factor i.e. deprivation. The increase observed due to both influences is significantly greater than the increase from either factor alone. This suggests that there is an interaction between ‘criminal genes’ and adverse environments that can foster and facilitate crime.
Although research on twin, family and adoption studies appears to be irrefutable and conclusive in their findings, many commentators have revealed the fallibility of such methodologies. Kessler and Moos (1970) assert the nature of these studies seldom provide verification for the supposition crime is genetically bound, since it does not illuminate what is inherited and how this ‘criminal’ inherited aspect functions and is transmitted. In contrast to this, chromosomal theories do explain crime in terms of what is inherited and how it affects criminality.
Fundamentally, females possess two X chromosomes and males possess an X and a Y chromosome. In Klinefelter’s syndrome however, males are born with an additional Y chromosome which has been implicated in aggression. Since males with Klinefelter’s syndrome possess an added Y chromosome, hyper-aggressive and hyper-masculine characteristics tend to dominate the personalities of such individuals. The XYY chromosomal configuration has been found to be particularly apparent in prison populations (Price, Strong, Whatmore & McClemont, 1966).
Again, the genetic make-up of an individual is seemingly interwoven in criminality. Though, this theory lacks explanatory power as Epps (1996) asserts those males with XYY chromosomes are particularly engaged in non-violent crimes as opposed to violent crimes. Moreover, it is curtailed in that it is inept in explaining why and how women are violent or commit crimes.
Certain theories also suggest there are physical (constitutional) differences between criminals and non-criminals. Through empirical observations, Lombroso (1876) concluded that certain individuals are ‘born criminals’ with physical defects i.e. receding chins who have inherited atavistic (primal) traits. This notion was then furthered by Sheldon who in 1949 formulated the somatotype hypothesis which states that delinquency is associated a mesomorphic (athletic/muscular) body type.
The concept of an archetypal physique of a criminal has been disputed and dismissed by Goring (1913).In summarising his findings, Goring declares that there are no significant physiological differences between criminals and non-criminals. Rather, greater physique variability was found in a normal population than a criminal population.
Due to the shortcomings of genetic explanations, it is essential to also examine psycho-social models to provide a holistic understanding. Eysenck (1996) implicates personality in crime via the use of the PEN (psychoticism, extraversion and neuroticism) model. Eysenck notes all individuals possess these traits to a varying extent. However, criminals, especially violent criminals, possess excessive pathological amounts of all three traits which eventually lead to criminal behaviour.
Personality disorders have also been implicated in crime. According to the DSM IV TR (2000), Antisocial Personality Disorder (ASPD) is characterised by violation and disregard of others rights that starts in childhood. Morley and Hall (2003) note ASPD has been found to be associated with increased criminality and delinquency.
The social models explain crime in terms of learning and reinforcement. Bandura and Walters (1963) illustrated how behaviour can be learned via mere imitation in one of psychology’s seminal experiments. Children imitated actors or cartoons physically striking bobo-dolls on a television screen. This has wider implications in that parenting, or the lack of it, can be imperative in determining whether an individual turns to criminality or not. The role of parenting and attachment have also been implicated in crime via the works of John Bowlby and the maternal deprivation hypothesis. Bowlby (1944) studied 44 juvenile theives in an institution assessing the offenders’ childhood bond with their respective primary caregivers. He concluded, more than half of the delinquents had been separated for at least 6 months prior to the age of 5. Moreover, 32% of the delinquents exhibited ‘affectionless psychopathy’ which is directly associated with the lack of a monotropic childhood bond. These conclusions further elucidate the role of an individual’s childhood in determining criminality.
Family disunity, childhood abuse, peers, media and drug use are all social factors Lykken (1995) notes as influential variables. However, when deliberating social theories of crime it is difficult not to transcend the realm of psychology and delve deep into plain sociological conjecture (e.g. with poverty) that at its essence looks for no real-life conclusion. In a strict psychological sense, where the focus is on the individual, it is more than likely that crime is a concoction of a plethora of factors that encapsulate both nature and nurture. In this respect, crime can be seen as polygenic where the diathesis stress model (Gross, 2010) accounts first, for a genetic predisposition and second, an environmental trigger that intensifies the natural propensity to commit a crime.

Foyzul Rahman, 30/01/2013.
Recommended citation: Rahman, F. (2012). Crime & Genetics. http://knowledge-fozrahman.blogspot.com/2013/01/crime-and-genetics.html

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