There appears now to be widespread acceptance that a correlation between screen violence and aggression is proven. In 1978 one of the largest European studies, by Belson, found a relationship between viewing media violence and serious, criminal behaviour by adolescent boys.
Some commentators argue that, while there is an effect, it is negligible.
Eysenck and Nias warn their model is over-simplified, because human behaviour is multiply determined. German and Swedish studies show children from lower socio-economic groups watch significantly more than average levels of television. Caprara and Rutter state that children vary in their susceptibility to media influences, with effects tending to be greatest when children already experience violence. The children most likely to be affected are the most vulnerable. Huesmann put forward a reciprocal model in which some personal factors lead to greater TV watching and aggressiveness, and hence to a greater interest in TV violence.