If you're having a hard time convincing kids of all ages to pull themselves away from their video games, there's a deep-rooted psychological reason, a study by U.S. researchers suggests.

The survey by psychologists at the University of Rochester in Rochester, N.Y.,and virtual worlds researchers at Immersyve Inc. indicates that people enjoy video games because they are satisfying at a fundamental psychological level.

The research published Tuesday in the journal Motivation and Emotion found that the driving force that draws people to games was not fun — which doesn't keep players interested — but instead a sense of achievement, freedom and even social connectedness.

"We think there's a deeper theory than the fun of playing," University of Rochester motivational psychologist Richard Ryan said in a written statement.

Gamers said they felt the best about their experience when the games they played produced positive outcomes in scenarios related to the real world.

"It's our contention that the psychological 'pull' of games is largely due to their capacity to engender feelings of autonomy, competence and relatedness," said Ryan, the lead investigator in four new studies about gaming.

The draw of video games "also can be experienced as enhancing psychological wellness, at least short-term," Ryan said.

The researchers asked 1,000 gamers what drives them to keep playing video games, examining what drew and maintained their interest, based on an area of the psychology of motivation known as self-determination theory.

Previous studies have examined the game mechanics rather than looking at the players.

The researchers evaluated players' motivations in virtual worlds by asking four groups of people to play different games, including a genre known as massively multiplayer online (MMO) games, which some industry watchers regard as the future of video games.

MMOs let hundreds or even thousands of players interact simultaneously in a persistent world where events continue even when a gamer is not online.

The researchers found that for MMO gamers in particular, interrelations among playersprovided "an important satisfaction that promotes a sense of presence, game enjoyment and an intention for future play."

The study was co-authored by Andrew Przybylski, a graduate student at the University of Rochester, and Scott Rigby, president of Immersyve who earned a doctorate in psychology at the school.