Gene explanation of crime

MAO-A enzyme - what it does?

breaks down neurotransmitters like serotonin

What do mutations in MAO-A gene do?

linked to aggression

Difference in men and women with MAO-A gene

MAOA is on the X chromosome
not seen as strongly in women as one X cancels out the other
more common in men

Brunner (1993)

studied family in Holland with very high rate of extreme violence in men in family
found they all had a mutation on MAOA gene

Brunner (1993) - conclusion

explains their aggressive behaviour and supports theory that criminality can run through families

Christiansen (1977)

twin studies support theory
3500 pair of twins in Denmark and got data from criminal record

Christiansen (1977) - findings

concordance rate MZ - 35%, DZ - 13%
Mz share all genes, DZ share half

Raine (1993) - supporting evidence

reviewed 13 twin studies
found higher concordance rate in MZ than DZ
increases validity that genes play role in criminality

Moffitt (1992) - how and what he was finding out

if vulnerability to violent behaviour is linked between genes and environment
longitudinal study, 442 boys from birth to 26 years

Moffitt (1992) - what he found

boys with low MAOA gene and abusive childhood - more likely to be criminals
compared to those with either abuse or low MAOA gene

AO3 - twin studies

assumption that MZ and DZ are raised in similar environments
MZ raised similar - could explain higher concordance rate
no study has found 100% so nature must play role

AO3 - determinism

assumes we have no choice
may reduce blame - treat criminals more humanely, prevent criminals from taking responsibility