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GENETIC EXPLANATIONS OF OFFENDING BEHAVIOUR (Twin Studies (Twin studies…
GENETIC EXPLANATIONS OF OFFENDING BEHAVIOUR
Introduction (A01)
Genes are a strong determinant of who you are as a person. The debate of whether genes underpin criminal behaviour or whether it's a result of the social environment is an ongoing debate which researchers continue to investigate.
Although there's no clear explanation of why people turn to crime, researchers have now found a common trait amongst many inmates. Recent research has found that antisocial personality disorder (ASPD) was found in 40 - 70% of prison population, in comparison to just 1 - 3% in the general population.
Two genes are responsible for criminal behaviour:
MAOA (Monoamine oxidase A) - associated with dopmaine levels.
CDH13 (Cadherin 13) - associated with neural connectivity.
Key Study
A genome-wide study of Finnish prisoners found that from 794 prisoners, 568 were found to be positive for ASPD.
A further analysis found that two genes in particular (CDH13 and MAOA) were associated with criminal behaviour. (
Jari Tiihonen at al 2015
)
Twin Studies
Twin studies are a well known method for identifying a genetic basis of behaviour.
Christiansen (1977)
examined over 3,500 twin pairs in Denmark and identified concordance rates of criminal behaviour.
MALE MZ: 35%, MALE DZ: 13%
FEMALE MZ: 21%. FEMALE DZ: 8%
These findings indicate a degree of inheritance, however, the concordance rates are low (by twin study standards) which indicates that the environment still plays a big role in criminality. Secondly, the difference between male and female twins raises an interesting question about the role of gender in criminal behaviour.
Family studies
Family studies are another way of investigating genetic links in offending behaviour.
Brunner at al (1993)
conducted an analysis of a large family in the Netherlands, a number of which had been responsible for various counts of anti-social and criminal behaviour including attempted rape, arson and exhibitionism. They found that the males had a genetic condition (known as Brunner syndrome). The condition results in lower IQ levels and causes a deficiency in MAOA (serotonin - links to aggression).
Conclusion:
individuals can inherit genetic conditions which make them prone to offending behaviour.
Adoption Studies
Adoption studies attempt to separate environmental and genetic factors by looking at children who have been adopted and have therefore been raised by adoptive parents, where there's no genetic similarity. Additionally, they are not sharing the same environment as their genetic parents.
Crowe (1972)
compared a group of adopted children whose biological mother had a criminal record, to a control group of adopted children whose biological mother didn't have a criminal record.
It was found that if a biological mother had a criminal record, 50% of the adopted children also had one by the time they were 18. In the control group, this was only 5%. This indicates that, regardless of the changed environment, children seemed biologically pre-disposed to criminality.
Diathesis-Stress Model
Epigenetic genes (impacted by the environment) are able to be 'switched on and off' due to the epigenomes (chemical compounds directing genes) which have been affected by environmental factors such as maltreatment in childhood.
Caspi et al (2002)
conducted a longitudinal study on 1,000 people, initially assessed at age 26 for anti-social behaviour and found that 12% with low MAOA genes were maltreated as children and were responsible for 44% of violent crimes.
Evaluation
Limitation:
Twin and family studies are seen as problematic since they don't rule out the impact of the environment. The results could be due to social learning since the twin sets and families concerned are all occupying the same environment.
Strength:
Adoption studies enable psychologists to rule out the effects of the environment, since the adoptees are being raised in a different environment from the biological parent concerned.
Strength:
Genetic explanations have strong support for the nature side of the nature/nurture debate. For example, research into families and twins suggests that there's some genetic basis for behaviour, which has implications for our understanding of offending behaviour.
Limitation:
Genetic explanations counter the nurture argument as it ignores the influence of external factors such as parenting, culture and social learning, misses crucial elements of explaining offending behaviour and it can therefore be considered reductionist. If concordance rates aren't 100% there must be other factors.
Weakness:
Biological determinism presents problems for our legal system since it negates free will and raises the ethical question surrounding what society does with people who carry criminal genes. Another problem with a deterministic explanation isn't everyone with the same gene becomes a criminal, but it does show that for some people the cause of their behaviour is outside their control.