After the mass shooting at an Oregon community college in early October, a weary President Obama made an all-too-frequent address to the nation condemning the murderous act. But this time, he also decried the monotony of the reaction to it.

“The reporting is routine. My response here at this podium ends up being routine,” he said. “The conversation and the aftermath of it. We’ve become numb to this.”

Then this week another mass shooting. This time at a company holiday party. Like an elementary school or a movie theater, it was another tragic reminder that no place in America is immune from this violence.

The BBC began its news coverage of the San Bernardino rampage this way: “Just another day in the United States in America—another day of gun fire, panic, and fear.”

The more exposure a person has to an event, the less remarkable it becomes. That’s true for the good and the bad. If your husband brought you flowers every single day, it would stop being special. When there’s been more mass shooting in a year than there are days of the week, people will start to expect it.

Dan Romer, director of the Adolescent Communication Institute at University of Pennsylvania, was in a doctor’s waiting room when the news of Wednesday’s shooting flashed on a television screen. No one around him was surprised. People see the news and think, “They’ll be another one soon,” he said. They are resigned that mass shootings in America are commonplace.

“There’s no question that if you repeatedly experience something your reaction to it diminishes,” said Steven Maier, a psychology professor at the University of Colorado Boulder. “This has to do with habituation. That’s a well-known phenomenon.”

In many ways, it’s the same mechanism that has allowed humans to adapt for millennia — a process necessary to our survival.

Another term for it is desensitization. Once the novelty of something is gone, people won’t respond as intensely to it.

But if Americans have become so accustomed to mass gun violence that their response to it is just shy of a shrug, there can be serious societal repercussions.

“One risk is that we lose our empathy for others, which I think is a big deal because its one of the best predictors of pro-social behaviors,” said Brad Bushman, a professor of communication and psychology at Ohio State University.

Bushman worries that it will make humanity more callous. And he has evidence. In 2009, he conducted a study on how violent images impact people’s empathy to others’ pain. He had 320 college students play video games, both violent and nonviolent. Soon thereafter they overheard a staged fight where someone got hurt and was groaning in pain, according to a summary of the study.

People who had played a violent game took significantly longer to help the victim than those who played a nonviolent game—73 seconds compared to 16 seconds. People who had played a violent game were also less likely to notice and report the fight. And if they did report it, they judged it to be less serious than did those who had played a nonviolent game.

Additionally, he said, the more people are exposed to something bad and no one tries to fix it, the less people believe it can be fixed, which breeds complacency. Bushman advises people to force themselves to take action to fight that tendency. He does it by writing to members of Congress after almost every mass shooting asking them to vote on new gun laws.

People also can self-regulate their compassion, Keith Payne, a professor of psychology and neuroscience at the University of North Carolina has found in his research. He has studied how people tend to respond greater to one person’s suffering over many, but he said the same could be said for how people will have a strong reaction the first time something tragic happens and then it will dull with each recurrence.

“When the numbers get large people start to feel like they can’t get as emotionally involved because it could be unpleasant or overwhelming,” Payne said. “You can afford to be moved by one shooting victim, but once you realize the scope and the frequency they start to distance themselves.”

In other words, the more pandemic a problem, the more unmotivated people might feel.

“So much compassion shuts down because we feel we cannot make a difference or don’t have the means to help,” said Jane Dutton, a psychology professor at the University of Michigan. “Yet, sometimes just being with others’ pain– looking at, rather than looking away, can be helpful in and of itself.”

Yet Dutton believes that to override the numbness, people likely do show more compassion on a micro-level after such terrible news events. In other words, while they may not react as strongly to the shooting itself, they may find themselves in the aftermath being more compassionate to the people in their own lives. People inherently are motivated to care, she said.

There’s also a certain paradox in the response. People are simultaneously desensitized to the event because it’s happened so many times before while also having their sensitivities heightened for the same reason. They might be numb to the actual news, but each mass shooting carves away at people’s sense of security.

And that presents another societal problem.

“They expect it to happen,” Romer said, “as a result they could become fearful of doing things in public.”

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