Aggression: Genetic factors in aggression Flashcards
Who investigated twin concordance rates in aggression?
Coccaro et al.
Describe Coccaro’s twin study into aggression.
Measured degree of similarity in aggressive traits between twins. Found 50% of variance in direct aggression towards others was due to genetic factors.
Describe an adoption study’s findings into genetics and aggression.
Found criminal adopted boys were more likely to have biological parents with criminal convictions.
Who completed a meta-analysis into the influence of genetics on aggression?
Miles and Carey
Meta-analysis on 24 twin and adoption studies into aggression.
What did Miles and Carey find?
Genetics accounted for 50% of variance - strong genetic link.
With age, genetic influences continued to be strongest factor in aggression.
What gene (not specifically) has been associated with aggression levels?
Gene which influences the production of the MAOA enzyme.
Why is the MAOA gene associated with aggression levels?
Responsible for metabolism of serotonin in the brain. Associated with impulsive and aggressive behaviour.
What is the ‘warrior gene’?
MAOA-L gene.
Variant where serotonin is less regulated, leading to increased serotonin levels.
Describe research evidence for the influence of MAOA on behaviour.
Branner et al.
5 generations of Dutch men with violent and aggressive past.
Found abnormally low MAOA levels (MAOA-L).
AO3: Genetic factors in aggression
+advantage of using the MAOA gene to explain aggression levels
-reliability issue with the MAOA hypothesis
-sampling issue with genetic studies into aggression
-difficulty of determining the influence of genetics
(+AO3) What is the advantage of using the MAOA gene to explain aggression levels?
Examples gender differences.
Different vulnerabilities of genders to MAOA gene.
MAOA linked to X chromosome (women - 2, men - 1).
Women inherit mutated X gene, may have normal X gene from other parent to counter mutated X gene effects.
Men inherit mutated X cannot be countered.
(-AO3) What is the reliability issue with the MAOA hypothesis.
Serotonin deficiency hypothesis: low serotonin = aggression
MAOA-L: high serotonin = aggression
Inconsistent evidence within biological approach reduces reliability. Shows complexity of aggressive behaviour.
(-AO3) What is a sampling issue with genetic studies into aggression?
Only focus on convicted violent criminals in studies.
Difficult to compare to vast majority of non-convicted violent criminals. Small minority = less population validity.
Also participant effects and sample bias as convicted may have higher/lower aggression levels.
(-AO3) What is the difficulty of determining the influence of genetics?
More than 1 gene responsible for complex behaviour.
Many nongenetic influences.
Interaction of environment and genetics important. Can talk about reductionism etc.
