Genetic Factors/Explanations Of Aggression Flashcards
How are twin studies and adoption studies involved in genetic studies of aggression?
-Twin studies allow us to see if there are hereditary factors that goes into ones aggression.
-If aggression is found to be somewhat hereditary it could be implied that there is a genetic role in aggression.
-Adoption studies can be helpful as we can compare their behaviours between there bio and adopted parents.
-This way we can see how genetic and environmental factors of aggression interact.
Coccaro(1997)(AO1/3)
-Studied male MZ and DZ twins
-Aggressive behaviour was categorised as direct physical assault.
-Researchers found concordance rates of 50% and 19% for MZ and DZ respectively.
-Figures for verbal aggression had concordance of 28% for MZ and 7% for DZ.
-This would suggest genetic factors as when twins share twice the DNA (MZ 100% DZ%) they have ~double the concordance rates.
Mednick and Hutchings(1978)(AO3)
-Studied the links between criminality and aggression via a Danish adoption study.
-Found 10 percent danish adoptees with non criminal bio fathers became criminals.
-Found those who did have criminal bio fathers were criminals themselves 21 percent of the time - even if they never met their father.
-Suggests there is a genetic role to play in aggression due to the link between aggression and criminality.
COUNTER: crime is not specified, crimes may not be aggressive and not due to aggression.
MAOA-L (warrior gene)
-MAOA is a gene candidate - a gene linked to aggression.
-MAOA is a gene that controls the MAO-A enzyme production.
-MAO-A regulates our levels of serotonin (a neurotransmitter heavily linked to impulsive aggression).
-MAOA comes in two variants MAOA-H (high activity) and MAOA-L(low activity)
-MAOA-L causes an MAO-A deficiency and has been linked to higher levels of aggressive behaviour.
-MAOA-L has been nicknamed the “warrior gene” after Lea and Chambers(2007) found the gene to be possessed by 56% of New Zealand Maori men compared to 34% of Caucasians. The Maori have a reputation of being fearless warriors.
MAOA-L hypothesis
-Genes do not function in isolation as an explanation of aggression.
-The MAOA-L gene is only significantly seen to be linked to aggression when the gene carrier has experienced early trauma.
-Frazzetto(2007) found an association between anti social aggression and MAOA-L, but only in those who had experienced significant trauma before the age of 16.
-Frazzetto found those who carried the MAOA-L gene who did not have childhood trauma infact did not have higher aggression as adult males.
-This suggest the role of MAOA-L fits better as a diathesis in the diathesis stress model than an isolated cause of aggression.
Eval: MAOA-L hypothesis
- there is a correlation between low activity MAO-A enzymes and aggression.
-however the link between the MAO-A enzyme is not properly understood
-The idea MAOA-L is linked to aggression conflicts with other ideas linking low serotonin and aggression.
-There is evidence to suggest low serotonin and aggression is linked in Passamonti(2012) tryptophan depletion study.
Passamonti(2012)(AO3)
-Tryptophan is an amino acid in food that is required to produce serotonin.
-Passamonti wanted to study how a lack of tryptophan would change a human’s behaviour.
-He had participants avoid tryptophan containing foods in order to deplete the experimental groups tryptophan.
-Passamonti found through a series of questionnaires and tests that those depleted of tryptophan became more aggressive.
-This suggests that low serotonin can cause aggression.
