Evaluation

• Environment is a confounding variable


  One limitation of the genetic explanation of criminal behaviour is that the environment may act as a confounding variable:

  • Evans and Martin suggest parents, teachers etc. treat MZ twins more similarly than DZ twin
  • Therefore, greater similarity in terms of criminal behaviour may also be due to greater similarity of experiences
• Support for the DSM


  One strength is support for the diathesis-stress model of offending:

  • Mednick et al. analysed 13000 Danish adoptees and found that when neither set of parents had convictions, 13.5% of adoptees did
  • This rose to 20% when either of the biological parents had criminal convictions, and 24.5% when both sets of parents did
  • Therefore, both genetic inheritance and environmental influence play a role in determining offending behaviour
• Nature vs nurture


  One strength of adoption studies is that they offer support to the nature vs nurture debate:

  • Adoptees are exposed to different environments than that of their biological parents, so it is easier to separate the effects of nature and nurture than for twin studies
  • However, there may be trauma with being adopted, which can act as a confounding variable
  • Furthermore, adoption after birth means biological contact may have been maintained