Genetic factors in aggressive behaviour Flashcards
What is the research trying to determine?
Trying to determine the role of genetic factors in aggression – nature vs. nurture (nature=genetic inheritance nurture=environmental issues)
Outline why research is conducted on twins.
- MZ twins share their genes whereas DZ twins only share 50%.
- If MZ twins aggressive behaviour is alike then aggression could be down to genetics.
What has McGuffin and Gottesman found?
Found a concordance rate of 0.87 (or 87%) between MZ twins and 0.72 between DZ twins.
What did Coccaro find?
He compared MZ and DZ twins for aggressive behaviour and found that genes were able to account for around 40% of the differences between individuals in aggressive behaviour; but that the environment accountd for 50% of individual differences in physical aggression and 70% of individual differences in verbal aggression.
Outline why research has been focused on adoption sttudies.
• If the concordance rate between child and adopted parent is higher, then it is probably an environmentally influenced behaviour, but if concordance for the behaviour is higher between child and biological parents then it is probably a genetically influenced behaviour.
What did Hutchings et al. do?
Reviewed 14000 adoptions in Denmark and found that a significant number of adopted boys with criminal convictions had biological parents with criminal convictions providing evidence with criminal convictions.
What did Miles and Carey find?
Conducted a meta-analysis of 24 twin and adoption studies and found a significant genetic influence on aggressive behaviour. They also found that there was a strong influence from environmental and genetic factors, but that the environmental influence became less and the genetic influence became greater as the children grew older.
Outline the role of MAOA.
- No identifiable gene has been found for aggression but a gene responsible for producing protein MAOA has been found to correlate with aggressive behaviour. MAOA regulates the serotonin in the brain.
- Dutch family in 1960 found that lots of males in their family who had been very violent and aggressive had very low levels of MAOA in their bodies.
Outline the research by Caspi et al.
studied 500 male children and found that those with low levels of MAOA were seen to grow up to be aggressive but only if they were mistreated as children. Those who were not mistreated did not have aggressive traits. Therefore the gene and environment must play a role for the gene to be a contributing factor.
