Detailing the findings of two studies conducted by University of Michigan professor Brad Bushman, and Iowa State University professor Craig Anderson, the research fill an important gap in the literature on the impact of violent media.

Past studies demonstrated that exposure to violent media produces physiological desensitisation—lowering heart rate and skin conductance—when viewing scenes of actual violence a short time later.

However, the current research has shown that violent media also affects a person’s willingness to offer help to an injured person, both in a field study as well as in a laboratory experiment.

"These studies clearly show that violent media exposure can reduce helping behaviour," said Bushman, professor of psychology and communications and a research professor at the U-M Institute for Social Research.

He added: "People exposed to media violence are less helpful to others in need because they are ''comfortably numb'' to the pain and suffering of others, to borrow the title of a Pink Floyd song.”

In a study of 320 college students, the participants played either a violent or a non-violent video game for approximately 20 minutes, and then after a few minutes overheard a staged fight that ended with the "victim" sustaining a sprained ankle and groaning in pain.

It was found that those who had played a violent game took significantly longer to help the victim than those who played a non-violent game—73 seconds compared to 16 seconds.

Also, people who had played a violent game were less likely to notice and report the fight. And in case they did report it, they judged it to be less serious than did those who had played a non-violent game.

In the second study, the participants were 162 adult moviegoers. The researchers staged a minor emergency outside the theatre in which a young woman with a bandaged ankle and crutches "accidentally" dropped her crutches and struggled to retrieve them.

Participants who had just watched a violent movie took over 26 per cent longer to help than either people going into the theatre or people who had just watched a non-violent movie.