Genetic Factors

Genetic Factors

1. Defective gene produces low levels of MAOA

   • MAOA regulates metabolism of serotonin
     • Low levels of serotonin leads to impulsive aggressive behaviours

2. Twin Studies

   • Cocarro et al, (1997)
     • compared concordance rates in MZ and DZ twins
       • Found nearly 50% of variance in direct aggressive behaviour could be attributed to genetics
         • If aggression fully determined by genetic factors, MZ twins should be 100%
           • REDUCTIONIST
         • and environmental influences accounted for 50% physical and 70% verbal
           • Diathesis-stress Model

3. Adoption Studies

   • Hutching and Mednick (1973)
     • Danish study of 14,00 aoptions
       • Found correlation between adopted boys with criminal convictions and biological fathers convicted of violent crimes
         • cultural bias
         • Fails to acknowledge environmental influences of deprivation
           • "NATURE'

4. Caspi et al. (2002)

   • 500 male children
     • those with low levels of MAOA more likely to exhibit antisocial and aggressive behaviours, but only if they had been maltreated
       • Gene-environment interaction

5. Brunner

   • All males in Dutch family had criminal convictions as well as low levels of MAOA
     • Suggests aggressive tendancies are hereditary
       • DETERMINISTIC
         • Hines and Malley-Morrison (2005)
           • probabilistic rather than deterministic

6. PRACTICAL APPLICATION

   • Genetic engineering