A03 Genetic And Neural Explanations

• Problems with twin studies


  Early studies like Lange were poorly controlled and judgements related to zygosity were based on appearance rather than DNA testing and so lack validity.
• Samples and environment (Problems with twin studies)


  Also involve typically small samples and twins are an unusual so may not represent the rest of the population. Also environment is a confounding variable.
• Support for diathesis stress model of crime


  13000 Danish adoptees study by Mednick et al. Criminal behaviour defined as having at least one court-room conviction and this was checked against Danish police records.
• Mednick et al findings


  When neither biological nor adoptive parents had convictions, the adoptees that did was 13.5% yet rose to 20% when either of the biological or adoptive parents were criminals. 24.5% when both adoptive and biological parents were criminals. Shows environment influence cannot be ignored.
• Problems with adoption studies


  Many children experience late adoption meaning much of their infancy was spent with their biological parents anyway. Also, lots of adoptees spend time with biological parents following their adoption. Both points make it difficult to assess environmental impact biological parents may have.
• Petty offences (Problems with adoption studies)


  Also Mednick et al only studies petty offences and not violent crimes and so conclusions cannot be drawn.
• Biological reductionism


  Criminality is complex. Explanations of neural influences/genetics being a factor to offending behaviour may be too simplistic.
• Familial situations (Biological reductionism)


  Crime appears to run in families but so does emotional instability, poverty. Makes it difficult to disentangle effects of genes and neural influences from other possible factors. Also MZ twins never share 100% concordance rates.
• Biological determinism


  The 'criminal gene' is a dilemma. Our legal system is based on the criminal having personal and moral responsibility and only under extreme under circumstances can they claim they were not under free will (mental disorders). Raises ethical questions about what society does with people who carry criminal genes and what implications they have for sentencing.