Genetic factors in aggression

Genetic factors in aggression

1. Inheritance of criminal violence

   • Methodological limitations
     • Fail to distinguish between violent and non violent crime
   • Inconclusive evidence
     • Walters-1992 meta-analysis, low to moderate correlation between heredity and crime
     • Better designed recent studies provide less support for the gene-crime hypothesis.
     • Surgeon Generals' report on youth violence 2001- concluded 'data doesn't suggest a strong role for heredity violence'

2. Problems of assessing aggression

   • Relied on parental or self reports
     • Other studies have used observational techniques
   • Miles and Carey meta-analysis
     • Mode of assessment- significant moderator of aggressive behaviour in 24 studies used
     • Genetic factors explained large proportion of variance in behaviour in studies using parent/self reports
   • Observational ratings showed lots less genetic contribution and greater influence of environmental factors
   • Replication of Bobo doll
     • Twin pairs encouraged to act aggressively to doll
     • Found no difference between MZ twins and DZ twins
       • Suggested individual differences in aggression were product of environmental factors than genetic factors

3. Difficulties of determining the role of genetic factors

   • More than 1 gene contributed to a given behaviour
   • Many non-genetic environmental factors influence the development of aggressive behaviour
   • Influences may interact with one another
     • Genetic factors may affect which environmental factors have an influence and vice versa