Well, you will have to check out our media violence section, because we have a very good research section there.
There have not been a lot of longitudinal studies on the impact of media violence on aggression. One of the only ones, which came out of the U.S., didn't look at the context of the violence or at the television the participants were watching. Quite often in the longitudinal studies there is no contextualization of the violence, or it's just television in general. As I said, there are a lot of studies that will show you that there is no causal effect.
One thing that has been shown, and this has been shown with violent cartoons, is that children will act out immediately after viewing a violent cartoon. So they tend to have more aggressive behaviour immediately after viewing. That has been shown in several studies. But as far as longitudinal changes in behaviour go, there's very little out there.