There have been almost 300 mass shootings in 2015 alone, DNews cited — so why doesn't it seem like people care?

The answer may be habituation, or "the act of psychological adaptation." DNews co-host Trace Dominguez explains that when people continue to hear a story that doesn't change, in this case stories of mass shootings, then it becomes easy for people to ignore them. Since it's impossible to focus on each individual crime, Dominguez pointed out, it can cause psychological numbness.

And there is no short supply of crime-related stories in the media. According to the Pew Research Center’s Project for Excellence in Journalism, 29 percent of local news stories in 2005 were about crime; by 2012, that figure had dropped to 17 percent. Still, crime and mass shootings feed into what's called the "issue-attention cycle."

First, people react to news of a shocking event with alarm; then, they try to come up with a solution, also known as the "hard solution." After realizing how difficult this is, a person's interest in the issue declines and eventually the public falls into apathy. The cycle starts over again when there's news over a new shooting, genocide, civil war, or other shocking event.

"Each narrative is somehow novel, and the novelty reinvigorates attention," Dominguez said. "But otherwise school shootings are joining the list of things we just don't have the psychological wherewithal to stick to. Humans have to habituate."

If habituation can be healthy, how do people refocus their attention? Watch the full video above for all of Dominguez's thoughts.