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The sound of machine guns rattled through the building as explosions shook the walls.

No, I wasn’t at a weapons convention or shooting range or in an impromptu war. I was at the annual Electronic Entertainment Expo here, also known as E3.

With shootings happening with alarming frequency in schools, malls, movie theaters and streets across America, people are again asking if video games contribute to gun violence. And do so-called first-person shooter games have a particular impact on people — usually young men — who suffer from the types of mental illnesses that make them more prone to violent behavior?

In the halls of E3, where toy guns are everywhere and fantasy mayhem is encouraged, such questions are unavoidable.

A first-person shooter is a game in which you, the player, carry a weapon into some sort of video game conflict. It can be a simulation of a battlefield, like the beaches of Normandy on D-Day. It can be a simulation of violent city streets. And sometimes you get to be the villain, targeting police or the unfortunate workers in a bank that is about to be robbed.

The mass shootings in recent years in Newtown, Conn. and Aurora, Colo., were both committed by young men who had regularly played first-person shooters. But of course, tens of millions of young men play these games and never commit acts of violence.

Studies on the impact of video game violence by research institutes, universities and psychologists have been inconclusive. For seemingly every report that says video games lead to real-world shootings, there have been others rebutting those claims.

But new psychological studies are finding that as violent games become more realistic, constantly playing them can lead to a desensitization toward real violence.

“The research is getting clearer that over the long term, people with more exposure to violent video games have demonstrated things like lower empathy to violence,” said Dr. Jeanne Brockmyer, a clinical child psychologist and professor emeritus at the University of Toledo. “Initially, people are horrified by things they see, but we can’t maintain that level of arousal. Everyone gets desensitized to things.”

Ms. Brockmyer has written a paper, set to be published later this summer, that will show how areas of the brain responsible for empathy become muted by violent images when teens are exposed to them over long periods of time.

The paper comes on the heels of a study from Canada’s Brock University, published in February, which found that when children play violent video games for significant lengths of time, they are not as morally mature as other children their age. Researchers believe that the constant flood of violent images takes away a child’s ability to feel empathy for people who have been through similar situations in real life.

But while the study found evidence of slowed moral growth in teens who play games, it was unable to determine if these effects happen to people who play first-person shooter games for two hours a day, once or a week, or any other specific amount of time.

At video game conferences, asking the game-violence questions some psychologists are trying to answer is considered unacceptable. When I approached attendees and developers at E3 and asked if there was any evidence tying video game violence to real violence, or even if we should be talking about such a link, most people simply scoffed.

“Ha — umm, no,” one young man said snidely, rolling his eyes at me before returning to the first-person shooter he was playing.

People noted that mass shootings happened before there were video games. And guns and violence have been a part of video games since the mid-1970s, when Gun Fight, an early, very pixelated, two-player shooter was released in arcades.

But it is hard to argue that there isn’t some level of desensitization after a day spent at E3. At the main entrance of the Los Angeles Convention Center, where the conference was held, people lined up to play the new game Payday 2. In this game, you team up with friends to rob a bank. Killing police is a big part of succeeding.

As I watched people picking off cops and security guards with sniper rifles and handguns, news broke that a real-life shooting in Las Vegas had resulted in the death of two police officers and three civilians (including the two shooters).

I asked Almir Listo, manager of investor relations at Starbreeze Studios, which makes Payday 2, if he felt in any way uncomfortable about making a game that promotes shooting police.

“If you look hard enough, you can find an excuse for everything; I don’t think there is a correlation,” he said. “In Sweden, where I am from, you don’t see that stuff happen, and we play the same video games there.”

After the Sandy Hook shootings in Connecticut, when it became clear that Adam Lanza was a fan of first-person shooters, including the popular military game Call of Duty, President Obama said Congress should find out once and for all if there was a connection between games and gun violence.

“Congress should fund research on the effects violent video games have on young minds,” he said. “We don’t benefit from ignorance. We don’t benefit from not knowing the science.” Yet more than a year later, we don’t conclusively know if there is a link.

And gun violence in the real world — and the gaming world — goes on.

Email: bilton@nytimes.com