Many parents have expressed concern that violent computer games may make their children more aggressive and there has been in the past research suggesting there may be a link between violence and game playing.
Previous research has suggested that people who play such games are more likely to be aggressive and commit violent crimes, and less likely to help others.
But some experts argue that these correlations prove only that violent people are drawn to such games, and that the games themselves can not change behaviour.
But a new study says it has found that violent computer games may make people more likely to act aggressively, and the links between computer images of brutality and the real thing may go further than was at first thought.
The research team from the University of Missouri-Columbia said their study which monitored the brain activity of 39 game players suggests there is a causal link.
In the study the effects of popular games such as Doom, Mortal Kombat and Grand Theft Auto, which involve brutal killings, high-powered weaponry and street crime, indicated that avid users become desensitised to quite shocking acts of aggression.
They say the research suggests that violent computer games trigger a mechanism in the brain that makes people more likely to behave aggressively.
Psychologists found that this brain alteration, in turn, appeared to prime regular users of such games to act more violently.
A type of brain activity called the P300 response was measured by the researchers; the P300 response reflects the emotional impact of an image.
They found that when they were shown images of real-life violence, people who played violent video games had a diminished response.
However, when the same group were shown other disturbing images such as dead animals or sick children they had a much more normal response.
When given the opportunity to punish a fictional opponent the game players with the greatest reduction in P300 delivered the worst punishments.
Psychologist Bruce Bartholow, the lead researcher of the study, says he believes this is the first study to show that exposure to violent games has effects on the brain that predict aggressive behaviour.