Genetic Factors in Aggression

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GENETIC FACTORS IN AGGRESSION
- Genetic links - research has to seperate the role of the environment and influence of genetics
Selective Breeding - Species of various individuals have been selectively bred to produce highly aggressive individuals
- E.g. Doberman dogs were originally bred by humans to behave aggressively towards intruders.
- This ability to select the most aggressive dogs and breed them together to give new generations with the same aggressive tendencies suggests there are specific genes determining levels of agg.
MAOA - warrior gene, an enzyme technically not a gene.
- Found in the X chromosome, more prevalent in boys. Monoamine Oxidase is a protein produced by a certain gene that has been attributed to agg behaviour.
Role is to mopup excess neurotransmitters in synapse. MAOA regulates metabolism of serotonin, noradrenatine and dopamine.
Synapse becomes desensitised to neurotransmitters.
Low levels of MAOA has been attributede to agg behaviour.
Twin studies - Coccaro et al 1997 found in twin pairs a 50% variance in direct agg behaviours can be attributed to genetic factors. Found 19% for DZ, verbal agg was 28% for MZ, 7% for DZ.
Adoption studies - Hutchings and Mednick 1975 - found a number of adopted boys with criminal convictions had biological parents with convictions for criminal violence, when assessing 14,000 adoptions in Denmark.

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