By Scott Hillis

SAN FRANCISCO (Reuters) - Playing video games does not turn children into deranged, blood-thirsty super-killers, according to a new book by a pair of Harvard researchers.

Lawrence Kutner and Cheryl Olson, a husband-and-wife team at Harvard Medical School, detail their views in "Grand Theft Childhood: The Surprising Truth About Violent Video Games and What Parents Can Do," which came out last month and promises to reshape the debate on the effects of video games on kids.

"What I hope people realize is that there is no data to support the simple-minded concerns that video games cause violence," Kutner told Reuters.

The pair reached that conclusion after conducting a two-year study of more than 1,200 middle-school children about their attitudes towards video games.

It was a different approach than most other studies, which have focused on laboratory experiments that attempt to use actions like ringing a loud buzzer as a measure of aggression.

"What we did that had rarely been done by other researchers was actually talk to the kids. It sounds bizarre but it hadn't been done," Kutner said.

They found that playing video games was a near-universal activity among children, and was often intensely social.

But the data did show a link between playing mature-rated games and aggressive behavior. The researchers found that 51 percent of boys who played M-rated games -- the industry's equivalent of an R-rated movie, meaning suitable for ages 17 and up -- had been in a fight in the past year, compared to 28 percent of non-M-rated gamers.

The pattern was even stronger among girls, with 40 percent of those who played M-rated games having been in a fight in the past year, compared to just 14 percent for non-M players.

One of the most surprising things was how popular mature games were among girls. In fact, the "Grand Theft Auto" crime action series was the second-most played game behind "The Sims," a sort of virtual dollhouse.

Kutner and Olson said further study is needed because the data shows only a correlation, not causation. It is unclear whether the games trigger aggression or if aggressive children are drawn to more violent games.

"It's still a minority of kids who play violent video games a lot and get into fights. If you want a good description of 13-year-old kids who play violent video games, it's your local soccer team," Olson said.

The researchers also try to place video games in a larger context of popular culture. The anxiety many parents voice over video games largely mirrors the concerns raised when movies, comic books and television became popular.

"One thing I like about their approach is that they've tried to historicize the whole concept of a media controversy and that we've seen this before," said Ian Bogost, a professor at Georgia Tech known for his studies on video games.

The book urges a common-sense approach that takes stock of the entire range of a child's behavior. Frequent fighting, bad grades, and obsessive gaming can be signs for trouble.

"If you have, for example, a girl who plays 15 hours a week of exclusively violent video games, I'd be very concerned because it's very unusual," Kutner said.

"But for boys (the danger sign) is not playing video games at all, because it looks like for this generation, video games are a measure of social competence for boys."

Many video game fans have embraced the pair as champions of the industry, a label that makes them uncomfortable.

"We're not comfortable doing pro and con. We've been asked to do the pro-game side in debates, and I don't consider myself a pro-game person. Video games are a medium," Olson said.

(Reporting by Scott Hillis; editing by Patricia Reaney)