Biological Explanations of Offending Behaviour - Genetic Explanations Flashcards
What was Lange’s research - 1930
He looked at 13 MZ twins and 17 DZ twins where one of the twins had served time in prison. He found that 10 of the MZ and only 2 of the DZ had a twin also in prison. This shows that genetics have a larger influence than the environment.
What was Christiansen’s study - 1997
He studied over 3500 twin pairs born between 1880 and 1910 in Denmark. He checked their offender behaviour against police records and found a concordance rate for offending of 35% of MZ twins and 13% of DZ twins. WE can conclude from this that genetics have a large influence on criminality.
What were Crowe’s findings?
He found that adopted children whose biological mother has a criminal record had a 50% risk of having a criminal record, whereas children whose biological mother didn’t have a criminal record only had a 5% risk, indicating a strong genetic component in offending behaviour.
What are candidate genes?
According to gene theory, criminals have inherited a genetic predisposition that leads to them conducting criminal behaviour. Candidate genes are isolated genes that are believed to play a role in a behaviour.
What was Tiihonen’s research - 2014
He studied 800 Finnish offenders, and identified a pattern of 2 abnormal genes, MAOA and CDH13.
What is the MAOA gene?
MAOA is a chemical that helps to break down excess neurotransmitters in the synapse before the reuptake process. If the MAOA gene is defective, then there will be a lack of MAOA, meaning there is a buildup of serotonin - making someone respond to a stressful situation with aggressive and risk-taking behaviours.
What is the CDH13 gene?
A gene linked to attention deficit disorder and substance abuse
What were the findings from Tiihonen’s study?
He found that 5-10% of all severe violent crimes in Finland are attributed to the MAOA and CDH13 genotypes. Individuals with this high-risk combination were 13 times more likely to become violent offenders.
What is the diathesis-stress model?
Where a person has a genetic predisposition (diathesis) which is triggered by a biological or psychological stressor.
What is the limitation - Environment = Genetics?
It is often assumed that environmental factors are the same for MZ and DZ twins because they experience similar environments, however because MZ twins look identical, parents tend to treat them similarly which affects their behaviour. This means that higher concordance rates for MZ’s may be because they are treated more similarly than DZ’s, suggesting that the conclusions lack validity.
What is the support - Mednick?
Mednick researched 13000 Danish adoptees who have committed petty offences.
When neither the biological or adoptive parents had a criminal record, the % of adoptees that did was 13.5%
When one of the biological parents had a criminal record, the figure was 20%
When a biological and adoptive parent had a record - it was 24.5%
This suggests that although genetic influence plays a part, environmental influences cannot be disregarded.
What is the limitation - problems with adoption studies
Some children are adopted late, which means they have kept a considerable time with their biological parents, and also many children keep some form of contact with their biological parents.
Such methodological issues make it difficult to assess adoption studies as the biological parents may have had a significant impact on the environment. This makes it hard to separate nature and nurture
