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“If we want to have this grand, national dialogue about why our culture is as violent as it is, there’s no escaping the fact that there’s some media impact,” he said. “Unfortunately, all we ever hear out of Hollywood and their lobbyists is that everything that can possibly be done is being done. And that’s simply absurd.”

But John Lott, an authority who has written extensively on the connections between gun laws and crime, said there are simply too many variables involved to definitively tie mass shootings to violent movies or video games.

“It’d be one thing if you could say, ‘these states are allowed to sell the video games, and these states don’t’” over particular periods of time, he said. “I just am very skeptical — that unless you have some type of laboratory experiment, it’s going to be tough to disentangle those different things that are going on.”

Mr. Biden himself conceded that he doesn’t have a magic formula, either.

“There’s no measure that I’m aware of to be able to determine whether or not there’s a coarsening of our culture in a way that is not healthy,” he said. “I don’t know the answer to that question.”