Does playing violent video games make players aggressive? It is a question that has taxed researchers, sociologists, and regulators ever since the first console was plugged into a TV and the first shots fired in a shoot 'em up game.

Writing May 14 in the International Journal of Liability and Scientific Enquiry, Patrick Kierkegaard of the University of Essex, England, suggests that there is scant scientific evidence that video games are anything but harmless and that they do not lead to real world aggression. Moreover, his research shows that previous work is biased towards the opposite conclusion.

Video games have come a long way since the simplistic ping-pong and cascade games of the early 1970s, the later space-age Asteroids and Space Invaders, and the esoteric Pac-man. Today, severed limbs, drive-by shootings, and decapitated bodies captivate a new generation of gamers and gruesome scenes of violence and exploitation are the norm.

Award-winning video games, such as the Grand Theft Auto series, thrive on murder, theft, and destruction on every imaginable level explains Kierkegaard, and gamers boost their chances of winning the game by a virtual visit to a prostitute with subsequent violent mugging and recovery of monies exchanged. Games such as '25 To Life' remain controversial with storylines involving violent gangs taking hostages and killing cops, while games such as World of Warcraft and Doom are obviously unrelated to the art of crochet or gentle country walks.

Kierkegaard points out that these violent games are growing more realistic with each passing year and most relish their plots of violence, aggression and gender bias. But, he asks, "Is there any scientific evidence to support the claims that violent games contribute to aggressive and violent behaviour?"

Media scare stories about gamers obsessed with violent games and many research reports that claim to back up the idea that virtual violence breeds real violence would seem to suggest so. However, Kierkegaard has studied a range of such research papers several of which have concluded since the early 1980s that video games can lead to juvenile delinquency, fighting at school and during free play periods and violent criminal behaviour such as assault and robbery. Evidence from brain scans carried out while gamers play also seem to support a connection between playing video games and activation of regions of the brain associated with aggression.

However, Kierkegaard explains, there is no obvious link between real-world violence statistics and the advent of video games. If anything, the effect seems to be the exact opposite and one might argue that video game usage has reduced real violence. Despite several high profile incidents in US academic institutions, "Violent crime, particularly among the young, has decreased dramatically since the early 1990s," says Kierkegaard, "while video games have steadily increased in popularity and use. For example, in 2005, there were 1,360,088 violent crimes reported in the USA compared with 1,423,677 the year before. "With millions of sales of violent games, the world should be seeing an epidemic of violence," he says, "Instead, violence has declined."

Research is inconclusive, emphasises Kierkegaard. It is possible that certain types of video game could affect emotions, views, behaviour, and attitudes, however, so can books, which can lead to violent behaviour on those already predisposed to violence. The inherent biases in many of the research studies examined by Kierkegaard point to a need for a more detailed study of video games and their psychological effects.