- MZ - 1 fertilised egg divided into 2 embryos (identical) DZ - 2 fertilised eggs (non identical)
- Twin studies used to identify whether aggression is a product of inherited characteristics or through environmental influences.
- Studies establish higher concordance rate in MZ rather than DZ twins leading to argument genetics can cause aggression.
McGuffin and Gottesman 1985
P- Looked at aggressive/anti-social behaviour in MZ and DZ twins
E- Found 87% rate in MZ twins and 72% in DZ twins
E- Not a massive link between the rates, it suggests there may be a genetic explanation