Does violence on screen make society more violent?

Moviemakers excel at recreating violence and gore on screen. But Will Self asks if we should view fictional violence with more caution. When I was younger I equated viewing such things (and viewing actors performing sexual acts) with some sort of liberty - an existential freedom to be the virile fellow I felt myself to be, and a universal freedom to witness human expression in all its polymorphous perversity. But with age - and possibly, I concede, declining virility - I began to see that pornography entailed the exploitation of vulnerable and mostly young people, while the depictions of violence which bedizen our ubiquitous screens aren't victimless crimes - no matter how enthusiastically those who stage them, may consent. A few years ago Stephen Pinker published a book in which he set out to show that the venerable Dr Pangloss (a character in Voltaire's Candide) was in fact completely right - we are living in the best of possible worlds, while every day, and in every way, things can only get better.