The effects of mass media models on violence and other social behaviors have been known for almost four decades.
In the early 1960s, the noted psychologist Albert Bandura began an extensive laboratory program looking at television models and aggression. In a typical study, children would watch, on a television monitor, an adult beating a Bobo doll—a large, plastic doll with a weight at the base. When punched, the doll falls backwards and then springs upright.
In the Bandura-produced television show, models would punch, kick, fling, hit with a mallet, and scream at a Bobo doll. The children would then have the opportunity t play with various attractive toys, including a Bobo doll. The results repeatedly showed that children were likely to do what they had previously seen; those exposed to the violent model were more likely to strike, hit, punch, kick, and fling the Bobo doll.
Source: Age of Propaganda, by Anthony Pratkanis and Elliot Aronson