genetics

• Twin studies

  • Empirical evidence supports the role of genetics in the development of criminality
• Twin studies

  • Christianson studied 3586 twin pairs, 52% of identical twin pairs were concordant but only 22% of non-identical, showing genetics play a role in criminality
• Twin studies adopt a scientific procedure so the results should be objective and bias
• twin studies Concordance rate is never 100%
• twin studies - It is difficult to separate the effects of nature and nurture
• Adoption studies


  • A good way to separate nature and nurture
• Adoption studies

  • Mednick researched 14,000 adopted boys, 20% risk of criminality if biological parents had committed a crime, 14.7% risk if adoptive parents had committed a crime, showing crime is more likely if genetically related
• adoption studies - It is not possible to separate nature and nurture completely
• Adoptive parents may not be too dissimilar so they have the same life
• Jacob's genetic theory (XYY syndrome)

  • XYY males are more likely to be aggressive and violent and have a lower intelligence, helping trigger violent criminal acts
• Jacob's genetic theory

  • Studies suggest 15 in 100 prisoners have XYY, Price and Whitemore found XYY males were unstable and likely to commit motiveless crimes
• XYY is rare
• It is not possible to determine whether the XYY pattern caused them to commit a crime or not
• Monozygotic twins share 100% of their genes but dizygotic share 50%
• XYY is said to cause criminality as it acts on the brains limbic system and therefore men are more likely to be aggressive and violent
• Criminality is only somewhat linked to genetics. another factor could be environment