BRENDGEN TWIN STUDY

Twin methods, longitudinal

A-see if social aggression and physical aggression are down to genetics or the environment

P

• longitudinal over period of 6 years

• 234 twin pairs Quebec National Twin study.

• Teachers answered questionnaires on the twins aggression and peer ratings also given. Eg 3 point scale

R- similar ratings for both social and physical aggression in MZ twins (double DZ).

C- physical aggression caused by genetics and social/verbal caused by environment.

EVALUATE BRENDGEN

-extraneous variables social desire ability bias as the 234 twins may have guessed the aim over the 6 years they were being observed.

+APPLY to society in terms of reducing social aggression. Taught to overcome signs of physical aggression early before it develops into social aggression. Less problematic in society

-not generalisable as all 234 were twins of age 6 meaning there may be slight differences in upbringing such as being brought up differently to normal children. Therefore result about physical and verbal aggression causes may differ with children who aren’t twins. Also doesn’t represent people over 6yrs

+Took part in school in natural environment over span of 6 years so good ecological validity and mist likely natural behaviour in terms of aggression.

- not all twins DNA tested for MZ or DZ so some may have been in wrong groups skewing results on aggression