All those hours spent playing video games may not be wasted time after all: A new study suggests action-packed video games such as Grand Theft Auto III and Counter-Strike may sharpen your mind.

Researchers at the University of Rochester found that young adults who regularly played video games full of high-speed car chases and blazing gun battles showed better visual skills than those who did not. For example, they kept better track of objects appearing simultaneously and handled fast-changing visual input more efficiently.

To rule out the possibility that visually adept people are simply drawn to video games, researchers did a second experiment. They found that people who don't often play video games but were trained to play them developed enhanced visual perception.

Exactly why video games have this effect isn't clear. Researchers said more study is needed.

They said the findings suggest video games could be used to help visually impaired patients see better or to train soldiers for combat.

The study appears in today's issue of the journal Nature and was led by Daphne Bavelier, an associate professor of brain and cognitive sciences.

The study did not address how video violence affects behaviour. Instead, the experiments focused on a person's ability to recognize and interpret symbols and letters after playing video games.

"Some people think that video games are turning kids into supergeniuses or psychokillers," said Kurt Squire, an educational game designer at Massachusetts Institute of Technology. "The reality is probably close to this, where people can process visual information much quicker and be able to discern between different types of information."

Soldiers who grow up playing video games do better in processing information on a screen or operating long-range unmanned aerial vehicles that can film or photograph enemy activity on the ground, military experts say.