I think about the subject a lot because, as president of the British Board of Film Classification (BBFC), I do sentry duty in this area. I have found useful the work carried out by two British academics, Kevin Browne and Amanda Pennell - in particular their study of the effects of video violence on young offenders.
So, for me, Browne's inaugural lecture, given earlier this month on his appointment as professor of forensic and family psychology at the University of Birmingham, was an important event. How would he evaluate recent research, which is voluminous and stretches from the media pessimists who believe in a straightforward causal relationship between violent videos and antisocial behaviour, to the sceptics who say there is no evidence that films and television programmes cause harm?
Professor Browne starts off by making a distinction between what he calls violent drama films, violent action films and violent horror films. On this analysis, Schindler's List, Platoon and Saving Private Ryan are violent drama films, whose primary purpose is to express rather than to cause excitement. The violence portrayed is necessary to tell the story. Violent action films, on the other hand, trivialise violent interactions by treating them mechanically. Rambo and such films are designed primarily to excite and stimulate the viewer, and are thus a form of exploitation. Violent horror films are worse still in Professor Browne's ranking, being a form of obscenity in the way they invite the viewer to share in the degradation, humiliation, physical harm and death of people as entertainment.
In practice violent films do not always fit easily into Professor Browne's categories. In various ways violent action may be distanced from the viewer by its treatment, whether it be stylised or even comic, whether the characters be part of everyday experience or not ("zombies" do not persuade me of their authenticity); in short, whether they feel contemporary in location, in clothing and in cultural features. Horror films are a distinct genre with their own rules and only a minority precisely fit Professor Browne's third category. When they do, they are usually found only in video format; and in the worst of cases, they are refused a licence by the BBFC, which in effect is to ban them.
Violence starts in the home. It is now common ground that the nature of the family has by far the greatest effect on a person's eventual tendency toward violence. Poor parental role models, inconsistent discipline and abuse are all factors. Moreover, research on child-protection reveals that most children growing up in a violent family will have experienced aggression from a parent even before they have reached the age when they may have an interest in watching TV and videos.
As Professor Browne comments, the reciprocal of this is that those children who feel loved and cared for by their parents will be less interested in violent scenes on the television screen.
It is misleading to suggest that everyone is influenced by television in the same way. The unfortunate children who've grown up in a violent family are the most vulnerable to violent material in the media. Thus the equation, violent films induce violent behaviour, anyway requires two major qualifications - only certain sorts of screen violence; only certain sorts of people.
Professor Browne then goes on to identify what he calls a "volatile combination". Starting from his research into young offenders, who he found had a preference for violent films and sympathy with violent characters, and linking this with American work on television viewing, he argues that "the interaction of growing up in a violent family and experiencing real violence together with witnessing violence indirectly through the television screen seems to be the volatile combination that enhances the probability of committing violent offences".
So the rest of us, then, can go on watching as much violence as we like, safe in the knowledge that we are well-adjusted people, having been brought up in loving families? I am afraid not. There is the issue of desensitisation. This is hard to measure because there isn't an obvious outcome. Friends ask me whether I have become hardened to violence on screen, having recently had to watch more of it than I would choose. I can only answer that I am not sure. I haven't suddenly started kicking the cat.
I shall have to watch out, however, for all this leads Professor Browne to a simple but chilling conclusion: television and film violence influences people, but in different ways. On the one hand, those who are more disposed to violence will become active in their violent behaviour as their aggressive thoughts are reinforced and triggered. On the other hand, those less disposed to violence will become passive in their responses to violence as they become desensitised and habituated to violent imagery.
Thankfully, public tolerance of violence on screen seems at last to be declining. One piece of evidence is that for two or three years now, Hollywood's action blockbusters have done less well and actors specialising in violent roles, such as Arnold Schwarzenegger, are finding fewer parts.
Another sign is that the annual tracking study by the Broadcasting Standards Commission, which was published last week, showed that throughout 1998 viewers noticed a decline in the amount of violence on screen. And for the first time since 1991 the incidence of violence, bad language and sex before the 9pm watershed had declined.
Perhaps, too, the nature of violent imagery is changing. It falls more often into Professor Browne's first category - violent drama films. TV viewers in the study declared themselves more accepting of violence if they felt it was justified and in context. In contrast, the violence that is always harmful is the kind that we would recognise as "exploitative". Its consequence is to weaken society's resistance to the real thing.