Genetic Factors (in Aggression)

Coccaro et al.--Adult males concordance rates for physical assult = MZ- 50% , DZ- 19%. For verbal assult= MZ - 28%, DZ- 9%.

✖ - Isolating genetic factors - result of Environment or genes??

Rhee & Waldman-- meta-analysis: genetics accounts for 41% of aggression. 

- similar to twin study findings.

✖ - genetic factors had a greater effect when self-reports were used... can't draw valid conclusions

-Gene breaks down neurotransmitters. 

- Low- Activity Variant = associated with aggression as it effects serotonin levels.

Brunner et al.- low-activity variant linked with aggressive behaviour in criminally violent males.

Stuart et al.- 97 males that commited IPV. Males with low MAOA gene = most violent. 

✖ - In stuart et al's findings, the serotonin transporter gene also had an effect.

✖ - Vassos et al. found multiple genes (thousands).

✔ - Mertens et al. people with high activity MAOA were more cooperative and less aggressive in a lab game.

Frazetto et al.-  low- activity MAOA gene only had an effect if they experienced childhood trauma before age 15. 

✔ - E.g. McDermott et al. (2009) -- p.p. with low activity MAOA gene behaved aggressively in a lab-based allocation game BUT only if provoked.

✔ - Caspi et al (2002) -- 500 male children with low MAOA were more likely to exhibit antisocial behaviour only if maltreated as a child.