Q: How does news of mass shootings and other violence affect the way we think?

A: The news is, lately, a scary place. In reality, most people die of diseases of old age, such as heart disease and cancer. By contrast, more than half of news coverage is devoted to homicides and terrorism, which account for a minuscule fraction — less than 1 percent — of actual deaths.

We disproportionately buy, click on and share scary stories about people killing other people. And for this, you can blame your brain. Your brain's most important job is to take in information about the messy, confusing world we inhabit, find patterns embedded in the noise and use them to make predictions about the future. Brains particularly like actionable intelligence — and the most useful information pertains to threats that can be avoided.

Heart disease and strokes don't provide much fodder for this prediction machine. We know why they happen: because we get old. Talk about unactionable intelligence. The best you can do is stave them off for a while by doing things we already know are healthy: Eat well, exercise, don't smoke. You can almost hear your brain yawning.

Now consider a gunman mowing down a crowd of innocents. Acts like these are rare, vivid and unexpected. The combination sets your brain whirring, generating a red-alert signal called a "prediction error," a surge of activity deep in the brain's emotional core. A prediction error signal screams: "Look for a cause! Prevent this next time!"

This leaves you craving even more information about such attacks, in the vain hope you can predict the next one.

But you're not nearly as good at intuiting the minds of others — even people you know well — as you think you are. So the best way to figure people out is — and get ready, here comes some science — to ask them questions. Really. And this strategy works great in daily life, but not so well for mass murderers.

Another strategy is stereotyping: What do mass murderers usually look and sound like? This is not very effective, largely because there is no template (other than being male) to which mass murderers conform.

As a neuroscientist, I've spent more than a decade conducting research on rare populations such as altruistic kidney donors and psychopathic teenagers, and I've come away convinced of two things: First, we are not all the same. Some people have much more (or less) capacity for compassion than average. And second: The average person is really pretty nice. Study after study bears that out. Most people return lost wallets, share resources, donate to charity and help strangers as a default response.

Thus, the average person is totally unable to understand or predict why anyone would want to kill innocent people. And so the brain's prediction machine draws the worst possible conclusion: If we can't predict who among us is capable of heinous violence, it's best to assume anyone could be. From there, it's just one step further to conclude: Everyone could be. Translation: Trust no one.

While maintaining this psychological defensive crouch might seem like a safe bet, this is your brain fooling you. In reality, assuming that people are trustworthy is the better strategy.

So, try it out. Assume the best of others. You might be surprised to discover you don't miss that freaked-out feeling at all.

— Abigail Marsh, The Washington Post