(genetics) Bio explanations of criminal behaviour

• Christiansen (1977)


  • Christiansen's (1977) twin study found concordance rates for criminal convictions among were 35% for identical male twins and 12% for non-identical male twins
• Adoption studies

  • Adoption studies also support a link between genetics and criminal behaviour e.g. Mednick et al (1984) looked at 14,427 adopted children and compared the likelihood that a child would grow up to engage in criminal activity if their biological parent or adoptive parent were convicted criminals. The results suggested biological factors are more important than environmental factors
• AO3-Supporting evidence

  - in addition to the studies above, Brunner et al (1993) suggests the MAOA gene may explain criminal behaviour
• AO3-other factors

  if criminal behaviour was entirely determined by genetics, the concordance rate would be 100% among identical twins. However, Christiansen (1977) found the concordance rates for criminal behaviour among identical twins to be less than 100%, which suggests other factors are needed for a complete explanation of criminal behaviour
• AO3-Methodological concerns

  Adoptees are often raised by their biological parents for a long time before being adopted, so the correlation between having a biological parent who is a criminal and becoming a criminal seen in Mednick et al (1984) could be due- at least in part to environmental factors rather than genetics.