Twin Studies

• It is suggested that some people may be aggressive due to genetic inheritance; therefore researchers compare concordance rates for traits such as aggression between monozygotic and dizygotic twins.
• In one of the few studies that specifically studied the genetic transmission of aggression (rather than general anti-social behaviour) Coccaro et al found that for physical assault there was a concordance rate of 50% for monozygotic twins and 19% for dizygotic twins.
• As monozygotic twins (who share 100% of their DNA) are more likely to share aggressive behaviour than dizygotic twins (who share 50% of their DNA), this suggests there is a genetic basis for aggression.