When testing the brain activity of men and women playing video games, researchers at the Stanford University School of Medicine found that the reward centers of men's brains were far more activated than those in women's brains.
"These gender differences may help explain why males are more attracted to, and more likely to become 'hooked' on video games than females," the researchers wrote in their paper.
The study was originally conceived as a way to measure whether men or women were more territorial, Dr. Allan Reiss, the lead researcher and the director of the Center for Interdisciplinary Brain Sciences Research, told ABCNews.com. Reiss and his team decided to do this by looking at fMRI scans while two groups ? 11 men and 11 women -- played a specially designed video game.
In the game, a vertical line appears in the middle of the screen. The goal of the game is to click balls as they travel from right to left before they hit the wall. If the balls are clicked a certain distance before they hit the wall, the wall moves to the right and players gain space.
Researchers didn't give the participants any instructions other than to click as many balls as possible.
"We didn't want to bias them. We wanted to let their natural inclinations come to the surface of the game," Reiss said.
What researchers found when analyzing the fMRI scans is that men's mesocorticolimbic center, which is associated with reward and addiction, was more activated while playing the game than women's. Also, the more space, or territory, the men gained, the more active the center was.
"During computer gaming that involves these types of themes [of territory], males and females are different in terms of their brain activity," Reiss said.
The study turned out exactly as Reiss expected.
"By and large, people would admit males tend to be the more territorial of our species," he said. "And I think that this is the type of game that elicits that underlying predisposition."
But the study's findings that men are more likely to "get hooked" on video games fly in the face of both retail figures and the marketing strategies of leading video game companies.
According to NPD Group, American men and women split nearly evenly when buying video game software and hardware in 2007. Fifty-six percent of the $18 billion market in the U.S. was male, while 42 percent was female.
Similarly, Nintendo has increasingly tried to cater to women, specifically soccer moms, with the widely popular Wii and its portable gaming system, the Nintendo DS.
While Entertainment Consumers' Association president Hal Halpin welcomes any research on video games, he is wary of this particular study.
"We welcome any and all research about video game consumers and this one certainly seems to have a lot of merit. A concerning aspect of the research for me is that it might lead one to draw the hypothesis that game addiction is a mental, rather than behavioral, process," Halpin said. "That men are more drawn to violence than women has generally been stipulated for some time, and that male gamers prefer fighting and shooting games follows suit. I suppose that it would be more interesting to see how far the correlation could be drawn into other types of media and in other mediums. ... To do otherwise and focus solely on aggressive or violent games, to my mind, seems a play at the sensationalistic and not as helpful as could be otherwise."
Reiss admits, however, that, at least when it comes to playing video games, biology isn't destiny.
"Just like all behaviors, this is genetic as well as environmental," he said. "All behaviors have both nature and nurture components to them."