All those hours spent playing video games may not be wasted time after all.

A new study published in this week's issue of the journal Nature suggests action-packed video games such as "Grand Theft Auto III," "Counter-Strike" and "Spiderman" may sharpen your mind.

Researchers at the University of Rochester in New York studied young adults who played video games full of high-speed car chases and blazing gunbattles several times a week for at least six months.

They found that the video game players showed better visual skills than young adults who didn't play the games. For example, they kept better track of objects appearing simultaneously and processed fast-changing visual information more efficiently.

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Researchers say they've ruled out the possibility that visually adept people are drawn to video games in the first place. People who don't normally play the games were trained to play them, and they also showed better visual skills. The team said 10 hours of training on "Medal of Honor" is enough to improve a range of visual skills.

"Therefore, although video-game playing may seem to be rather mindless, it is capable of radically altering visual attentional processing," the researchers said.

Video games could be used to help visually impaired patients see better, or to train soldiers for combat, researchers say. But parents and anti-violence groups say some violent games trigger aggressive behavior.