Tremblay – early onset of aggression; aggression and preschool period

The Montreal longitudinal study helped us to understand that physical aggression is not something that starts during the elementary school years or during high school. Since they were at their peak in kindergarten and the frequency of behavior was decreasing as they grew older it forced us to start a study at birth to be able to understand the development of aggression during the preschool years. We’ve been following 2000 children from five months of age and they’re now in kindergarten.  

What we’ve been seeing is that from five months to approximately 24 months there is a rapid increase in the frequency of physical aggression; that the peak of physical aggression in terms of frequency is between age two and three, four years of age. And after that it starts decreasing. So that clearly, if there is learning of physical aggression it’s starting very early but we believe that what we’re seeing is that children do not have to learn to use physical aggression; this is a normal behavior early on and that the environment helps the child learn to use alternatives to physical aggression and this is why there is that early peak and then decrease of use of physical aggression throughout elementary school and adolescence. 

We’ve also learned that there are children, although everybody does it at age two, there are some who use physical aggression more often than others and those are clearly more at risk of not learning alternatives. They need very good environments to be able to learn to put on the brakes. So that it’s important for children during the first three, four years of life to have an environment that is helping learning alternatives to using physical aggression.