genetic factors in aggression Flashcards
How might genes influence aggression?
Genes code for physical and psychological traits. Aggression may be inherited if certain genes increase its likelihood.
What do twin studies suggest about the heritability of aggression?
About 50% of variance in aggressive behaviour is due to genetics. Greater concordance is found in MZ twins (100% genes shared) than DZ twins (50%).
What did Coccaro’s study find?
MZ twins showed more similarity in aggressive behavior than DZ twins, supporting genetic influence.
What do adoption studies reveal about aggression?
If adopted children resemble biological parents in aggression, it suggests a genetic basis. Rhee & Waldman’s meta-analysis found 41% of variance due to genes.
What does the MAOA gene do?
It regulates the enzyme monoamine oxidase A, which breaks down serotonin in the brain.
What is the “warrior gene” and how is it linked to aggression?
The low-activity variant (MAOA-L) is linked to higher aggression. Found in 56% of New Zealand men in one study (Lea & Chambers).
What did Brunner’s study find?
Men from a violent Dutch family had MAOA-L and low MAOA enzyme levels—linked to impulsive aggression and criminal acts.
How does trauma interact with the MAOA gene?
Frazzetto found antisocial aggression was linked to MAOA-L only in men with early childhood trauma, suggesting a gene-environment interaction.
What supports the MAOA-aggression link?
A: Mertins et al. found men with high-activity MAOA were more cooperative in a money distribution game than those with low-activity variants.
What’s a limitation of the serotonin-MAOA link?
The mechanism is unclear—low MAOA should mean higher serotonin, yet aggression is linked to low serotonin. The issue may be dysregulation, not levels.
What’s a criticism of twin studies?
The equal environment assumption may be false. MZ twins often experience more similar environments, inflating genetic influence estimates.
