It's not the gore that attracts video game players, but the pleasure of mastering a challenge, according to U.S. researchers who say their findings have implications for game designers.

Researchers with the University of Rochester in New York state and Florida-based Immersyve Inc., a player-experience research firm, say that for many people, gore actually detracts from a game's "fun factor," decreasing players' interest and desire to purchase a game.

Their study, published online Friday in the Personality and Social Psychology Bulletin, is based on two surveys involving 2,670 frequent video game players and four experiments involving more than 300 undergraduates.

Both experienced and beginner players preferred games where they could conquer obstacles, feel effective, and have lots of choices about their strategies and actions.

"Conflict and war are a common and powerful context for providing these experiences, but it is the need satisfaction in the gameplay that matters more than the violent content itself," co-author Richard Ryan, a motivational psychologist at the university, said in a release.

In one portion of the study, the investigators took the first-person shooter game "Half Life 2" and modified it to make a violent version and a non-violent version. Players either had a weapon that was like a shotgun or they had a psychic power.

"And then we manipulated the blood level and the gore level, so when people had the gun and they were told that it was going to be a kill or be killed situation, when they actually took out an adversary, it was very bloody, it was a very violent game," said lead author Andrew Przybylski, a graduate student in social psychology.

"And then in the less violent condition they were essentially playing a game of tag. When they were able to hit someone with their ability, the person just floated up very serenely into the air before evaporating."

The researchers wanted to find out if the same game became more fun for players when they made it more violent.

"And the answer to that question was no … as you made the game more violent, it didn't add extra variance in how enjoyable the game was."

Study subjects were assessed through a series of questions, along the lines of "how much fun was the game you just played?" and "would you like to play this game again when you come back to our lab?"

Still, violent content was preferred, though not enjoyed more, by a small subgroup of people who scored high in aggression traits.

"Video games," concluded the authors, "are enjoyable, immersive, and motivating insofar as they offer opportunities for psychological need satisfaction, specifically experiences of competence and autonomy, to which violent content per se is largely unrelated."

Craig Anderson, director of the Center for the Study of Violence at Iowa State University, said the studies were very well done methodologically and make an important contribution to our understanding of what motivates people to play video games.

"A common belief held by many gamers and many in the video game industry — that violence is what makes a game fun — is strongly contradicted by these studies," he said in an email to the Canadian Press.

With files from the Canadian Press