Genetic explanations Flashcards
1
Q
Genetic Explanations
Twin studies
A
- Twin studies have suggested heritability accounts for 50% of aggressive behaviour.
- Corraro (1997) found a 50% concordance for physical violence in MZ twins which share 100% of their DNA.
- Verbal aggression concordance was 28% MZ compared to 7% for DZ.
2
Q
Genetic Explanations
Adoption studies
A
- Similarities in aggression between adopted children and biological parents suggests genetics.
- Similarities between adopted children and adoptive parents suggests environmental influence.
- Rhee and Waldman (2002) found genetic influences accounted for 41% variance in aggression.
3
Q
Genetic Explanations
MAOA gene
A
- MAOA gene controls the production of the enzyme monoamine oxidase (MAO-A)
- MAO-A regulate serotonin, which plays a role in impulse control.
- The gene comes in a high and low varient.
- MAOA-L results in MAO-A deficiency which is linked to high levels of aggression.
- Brunner (1993) studied 28 men from a Dutch family repeatedly involved in impulsively aggressive behaviours such as rape, murder and assault.
- The men has abnormally low MAO-A as well as the MAOA-L variant.
- This is sometimes refered to as ‘Brunner syndrome’
4
Q
Genetic Explanations
GxE interactions
A
- Gene are crucial influences on aggressive behaviour but doesn’t function in isolation.
- MAOA-L is only related to adult aggression when paired with early trauma.
- Frazzetto (2007) found association between higher antisocial aggression and MAOA-L and this was only present in men who experienced significant trauma in the first 15 years of life.
- Those who did not experience trauma did not have high levels of aggression even if they possessed the gene.
- This is strong evidence for GXE interactions (diathesis-stress).
5
Q
Genetic Explanations: Evaluation
Twin studies lack validity
Limitation
A
- The genetic explanation using twin studies may lack validity.
- The assumption is that every pair of twins have the same environment whereas DZ twins may not share their environment to the extetn MZ twins do.
- The equal environments assumption may be wrong because twins may be treated differently by others.
- MZ twins are treated very similarly (e.g. praised for aggression) while DZ twins aren’t.
This suggests concordance rates by be inflated and genetic influence may not be as great as suggested.
6
Q
Genetic Explanations: Evaluation
Complex link
Limitation
A
- The MAOA-L gene causes low activity of MAO-A which should lead to high serotonin because low enzyme activities don’t deactivate serotonin, leaving more to transmission.
- It is more accurate to say levels are disrupted rather than being higher or lower than usual.
The relatinship between the MAOA gene and serotonin is not fully understood.
7
Q
Genetic Explanations: Evaluation
Research support
Strength
A
- Mertins (2011) found men with MAOA-H were more cooperative in a money distributing game.
- They made fewer aggressive moves than MAOA-L participants.
This supports the link between MAOA gene activity and aggression.
