Genetic factors in aggression

• What is the biological approach to aggression related to?

  It is related to genetic make-up.
• What do researchers aim to establish regarding genetic influences on aggression?

  They aim to determine the sensitivity to genetic inheritance versus environmental influences.
• What research techniques have been employed to study genetic factors in aggression?

  Twin adoption studies, analyses of individual genes, and studies of violent populations.
• How do twin studies contribute to understanding aggression?


  • Compare similarity in aggression between monozygotic (MZ) and dizygotic (DZ) twins.
  • Similarity in MZ twins suggests genetic influence.
  • Similarity in both types suggests environmental influence.
• What percentage of variance in aggressive behavior is suggested to be due to heritability?


  About 50%.
• What were the concordance rates for aggressive behavior in MZ and DZ twins according to Coccaro et al. (1997)?


  50% for MZ twins and 19% for DZ twins.
• What do adoption studies help to untangle in the context of aggression?


  They help to untangle the contributions of environment and heredity.
• What did the study of over 14,000 adoptions in Denmark find regarding adopted boys with criminal convictions?


  Many had biological parents with convictions for criminal violence.
• What did Miles and Carey (1999) conclude from their meta-analysis of twin and adoption studies?


  • There is a strong genetic influence on aggression.
  • Genetic factors could account for up to 50% of variance in aggression.
• What did Rhee and Waldman (2002) find in their meta-analysis regarding aggressive anti-social behavior?


  • It is largely a product of genetic contributions.
  • Combined results of 51 twin and adoption studies supported this conclusion.
• What variables moderated the genetic influence on aggression in the studies by Miles and Carey and Rhee and Waldman?


  Age of participant and assessment method for aggression.
• What is a problem with assessing aggression in genetic studies?


  Many studies rely on parental or self-reports rather than observational techniques.
• What did the Caspi and Carey meta-analysis reveal about the mode of assessment in aggression studies?


  It was a significant moderator of aggressive behavior.
• How did the mode of assessment affect the findings regarding genetic factors in aggression?


  Parental or self-reports showed a larger genetic contribution than observational ratings.
• What challenges exist in isolating genetic influences on aggression?


  • Difficulty in separating genetic and environmental factors.
  • Genes may only express aggressive behavior under favorable environmental conditions.
• What is the role of the MAOA enzyme in the brain?


  It breaks down neurotransmitters, especially serotonin, after nerve impulses.
• What is the 'warrior gene' associated with?


  It leads to low MAOA activity and has been linked to aggressive behavior.
• What did Brunner et al. (1993) find in their study of a Dutch family regarding MAOA levels?


  Men involved in aggressive behaviors had abnormally low levels of MAOA.
• What did Caspi et al. (2002) discover about children with the low variant of MAOA?


  • They were more likely to exhibit anti-social behavior.
  • This was compared to those with the high variant of MAOA.
• What did McDermott et al. (2009) find regarding participants with the MAOA-L gene?


  They displayed higher levels of aggression in response to provocation.
• What is the significance of gene/environment interactions found by Caspi and McDermott?


  • MAOA-L variant leads to anti-social behavior only under certain environmental conditions.
  • Environmental factors can mitigate or enhance genetic predispositions.
• What did the animal studies by Rene-Cates et al. (1995) reveal about MAOA and aggression?


  • Disabling the MAOA gene in male mice increased aggression.
  • Restoring the gene function returned aggression levels to normal.
• What are the positive implications of genetic research on aggression?


  • May inform treatments for personality disorders.
  • Could aid in rehabilitation of offenders.
• What ethical concerns arise from genetic testing in criminal cases?


  Findings may be used as evidence for diminished responsibility.
• How does the concept of free will relate to genetic influences on aggression?


  • Genetic findings may suggest biological determinism.
  • This raises questions about the extent of free will in aggressive behavior.