I don't know you. But I'm guessing I can still tell you something important about yourself: You are more freaked out about the world - especially the other people in it - than you should be.
For starters, you are reading this, which means you consume at least some news media. And the news is, lately, a scary place. Perhaps you saw some stunning graphs recently that depicted the most common actual causes of death in the United States, the causes of death most commonly searched for online and those that get the most news coverage. 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. Perhaps as a result, about 10 percent of white-knuckled web searches for likely causes of death are for these largely unlikely outcomes.
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, thus increasing your odds of survival.
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.
Your brain responds this way to scary natural disasters like earthquakes, too. But unlike earthquakes, murder and terrorism carry yet another feature that really throws the prediction machinery for a loop: They are caused by people. Predicting the actions of other people is unusually difficult, because it requires understanding the minds directing them.
And 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. A third strategy is to use yourself as a model: "What would I be thinking in this person's shoes?" Again: A good strategy for daily life, less so for understanding rare acts of horrifying violence.
The reason is that most people would never commit an act like this. 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. Think about it this way: If people weren't, on average, pretty compassionate, we wouldn't need a label like "psychopath" for the small group of people who aren't.
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.
This sequence can leave many people (up to 1 in 5 of us) genuinely paranoid - unreasonably suspicious of everyone's intent. And 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. People who are trusting have more money and more friends. They are also happier, perhaps because their social lives are more rewarding. Trust also makes the world a better place - it's the basis of all cooperation and social capital.
So, try it out. Assume the best of others. Ask a stranger a friendly question. Trust that others will usually treat you well in return. Sometimes they won't, to be sure, and you should always be alert for genuine red flags. But you don't need to go looking for them, in the news or in real life. And you might be surprised to discover you don't miss that freaked-out feeling at all.