Genetic factors in aggression - Evaluation

Cases et al (1995) found genetically engineered mice with low MAOA levels had atypical serotonin levels, demonstrating increased levels of aggression.

Brunner et al (1993) In a study of a Dutch family, they found that male members who had been involved in serious crime had abnormally low levels of MAOA.

Problems separating genetics and the environment. McDermott et al (2009) found that participants with the low-activity MAOA gene behaved aggressively in a lab based money-allocation game, but only when provoked.

MAOA gene only explain aggression in 1/3 men in Western populations. Often expressedin women due to chromosomal make-up. Means aggression in 2/3 men + most women cannot be accounted for this way.