There is, however, a correlation between the school yard variety of aggression and exposure to movie, game and TV violence, said Joel Dvoskin, a clinical psychologist and co-editor of "Using Social Science to Reduce Violent Offending."
"But correlation is not the same thing as causation," Dvoskin said. "Kids who are more violent are also more intrigued by violent imagery. It's also likely that some violent imagery can influence the manner in which people act out their aggression."
Hollywood director Cohen said that audience identification with characters can be powerful — pointing out that Colorado shooting suspect James E. Holmes was apparently influenced by Heath Ledger's portrayal of the Joker character in the previous Batman movie, "The Dark Knight."
"The creation of such an iconic character — the Joker — played by such a charismatic actor, Heath Ledger, got internalized by a disturbed young man," Cohen said.