Participants were put into a room separately observing the role model's behaviour. The room contained the Bobo doll, a toy gun, hammer and other neutral toys. Aggressive model hit Bobo doll with hammer and shouted abuse. Non-aggressive model played nicely with Bobo doll. After 10 minutes, children were taken down corridor to another room. Known as 'aggression arousal' stage. In new room with same set-up , participants were observed for 20 minutes by 2 independent observers and rated on the extent they imitated the behaviour they had witnessed.