Watching television and films 'can make you mean'

The study, conducted in the UK but published in the United States, found that watching mean actions on screen makes people just as prone to violence as sitting through footage of violence itself.

The findings will fuel the controversy about the link between onscreen violence and real life behaviour.

Violence in films has long been blamed for physical aggression among children but the revelation that watching cruel and malicious behaviour is just as damaging could transform the debate about the age ratings applied to films.

The research was conducted by Dr Sarah Coyne, an assistant professor at Brigham Young University in Utah, but it focused on British women she observed while working at the University of Central Lancashire in Preston.

The students who took part in the experiment had their behaviour tested after watching one of three films: a knife fight from Kill Bill, which features Uma Thurman as an assassin; Mean Girls, which focuses on a character played by Lindsay Lohan who turns the tables on three bitchy female school bullies; and a calming séance scene from the romantic film What Lies Beneath.

Dr Coyne told The Sunday Telegraph: "We showed them the clips and then monitored their behaviour afterwards.

"They were told they were competing in a game against someone online and the loser would get a really loud blast of noise. They were able to set the level of the noise."

Those who watched Kill Bill or Mean Girls turned the noise up much louder than those who did not.

A second test used an actor who pretended to be a rude job applicant seeking a reference.

"Those who watched Kill Bill or Mean Girls were more aggressive on both tests than the third group."

Dr Coyne said the study is important because mean behaviour is far more prevalent than extreme violence. "Most of us are not physically violent. We don't go and kill somebody or stab somebody," she said. "But after watching they might just beat up their wife or talk down to their kid or spread a rumour. We see these lower level forms of aggression, this meanness, all the time."

Dr Coyne said the findings might drive some parents to push for episodes of aggression in films to be taken into account in assigning their ratings.

The study is in November's Journal of Experimental Social Psychology.

Dr Coyne's earlier work probed incidences of aggressive behaviour resulting from watching British soap operas, which feature up to 15 incidences of bitchy behaviour each hour.