Genetic Explantions

Question 1

Research support for twin studies –

Answer 1

Research support for genetic transmission comes from
Christiansen (1977) who studied over 3,500 twin pairs in Denmark and identified concordance
rates of criminal behaviour. He found concordance rates of 33% (MZ) and 12% (DZ), suggesting
that offending may have a genetic component. However, a problem with twin studies of criminality is that most twins are reared in the same environment and so this maybe a major confounding variable, as the concordance rates may be due to shared learning experiences rather than genetics. For example, an identical twin (MZ) may be more likely to model the criminal behaviour of their identical twin than in the situation with non-identical (DZ) twins where their
twin may be a different gender. This therefore highlights the difficulty of disentangling nature from nurture when explaining offender behaviour

Question 2

Research support for the role of the MAOA gene in offending behaviour

Answer 2

Evidence to support the idea that the gene for MAOA is linked to aggression and therefore offending behaviour comes from research by Brunner et al (1993). He investigated male members of a Dutch family where several generations of the men had a history of aggressive and violent acts. He found that the males had a genetic condition which became later known as “Brunner syndrome”. The condition results in
lower intelligence levels (the family studied had an average IQ of 85) and causes a deficiency in monoamine oxidase A (MAOA) resulting in abnormal levels of neurotransmitters including
noradrenaline and dopamine. This offers compelling evidence that individuals can inherit genetic
conditions which make them prone to offending behaviour