Fear in the wake of a terrorist attack is normal. It’s natural and human. But it can also be counterproductive — and even cruel.

After the attacks in Paris last week, the gut reaction of many politicians around the world was to shut the door to Syrian refugees for fear that terrorists may be lurking among them. For those like New Jersey Gov. Chris Christie or House Speaker Paul Ryan, the "better safe than sorry" approach is winning out. Christie insisted he wouldn't want even a 5-year-old orphan refugee to enter his state.

Plenty of writers have come up with a long list of arguments for why barring refugees is a bad idea. None of the terrorists in Paris appear to have been Syrian nationals; all the attackers identified so far appear to be European Union citizens. Refugees are refugees because they are escaping violence, not joining it. There are much greater everyday dangers than terrorism, like car crashes. (Max Fisher runs through a comprehensive list of reasons here.)

But it's also rare that these arguments persuade anyone to change their mind. No one will get Chris Christie to relent on refugees just by showing him the statistics on traffic fatalities. And one big issue here may be that both sides are talking past each other. Those trying to make the case for allowing in refugees aren't fully grappling with the psychology of fear.

What psychology can tell us about the backlash against refugees

The reaction over refugees looks more comprehensible in the context of years of psychological work on conflict and emotion. Terrorist attacks set off one of our most fundamental gut reactions: When threatened, we draw clear lines between "us" and "them."

"When attacks happen, there’s a [perceived] high cost in mistaking in-group, out-group members for one another," says Mina Cikara, who runs the intergroup neuroscience lab at Harvard. "So when you see an attack like the one in Beirut or the one in Paris, it highlights those boundaries between 'us' and 'them.' It means those boundaries become more closely circumscribed; they become tinier."

It also means, Cikara says, that we overexaggerate our perceptions of who "they" are. Innocent Syrians can get caught up in our notions of who is a terrorist, no matter what the statistics say.

Psychologists have also found that threats from these out-groups often appear much bigger and more imminent than they really are. Jay Van Bavel and his colleague Y. Jenny Xiao at New York University illustrated this concept nicely in a 2012 paper.

The test was simple: The researchers asked participants to estimate the straight-line distance from New York to Mexico City. Participants who expressed more animosity toward Mexican immigrants rated Mexico City as being several hundred miles closer to New York than people who felt less threatened. And, Van Bavel adds, "We have new data showing that if people think the wall between the countries is secure, this effect goes away."

The uncertainty that comes in the wake of a terrorist attack is particularly effective at heightening our suspicion of outsiders. In 2014, Ingrid Haas, a political psychologist at University of Nebraska Lincoln, published a series of experiments showing that when her team manipulated participants' fear as well as their feelings of uncertainty, the participants became more intolerant of others. Simply instilling fear wasn't enough.

In other experiments, uncertainty has been found to strengthen feelings of group identity.

"Really the uncertainty is making things worse," Haas says of the current refugee situation. In chaotic news events, misinformation is bound to proliferate, and threatening narratives like "terrorists are sneaking in with refugees" prove particularly sticky.

Is there any way to change people's minds about refugees?

The negative reaction to the refugees is more emotional than rational. And, psychologists say, it's unlikely to be countered by statistics or logical counterarguments. To change people's minds, either the negative emotions ("refugees are dangerous") need to be turned down or more positive emotions ("refugees are human beings like us and need help") need to be turned up.

"Before you can even get people to talk in any sort of rational, statistics based way, of the probabilities of X, Y, and Z occurring, you have to attenuate [their] negative emotions," Cikara says. "When those negative emotions are really high, good luck having a rational conversation about probability."

Cikara singles out an intriguing experiment published in the journal Psychological Science that demonstrates it's possible to teach people to downplay negative emotions in us-versus-them decision-making.

For that study, Israeli researchers taught half of their participants a technique called cognitive reappraisal — basically a method to challenge your negative emotions, question how they originate, and then watch them dissipate among that meta introspection. All of the participants were then instructed to look through materials designed to get them angry. A week after the training, all the participants were asked question about the Israeli-Palestinian conflict. "What [the authors] found was that those who had practiced emotion regulation ... actually preferred less hostile and more diplomatic approaches," Cikara says.

Getting American politicians into cognitive reapprasial classes seems unlikely. But there is another approach. Charities have long understood the "identifiable victim effect," which suggests that images of singular victims are easier to empathize with than statistics, even when those statistics are astronomical.

"This is why pictures and stories can be so powerful," Deborah Small, a professor of marketing and psychology at the University of Pennsylvania, writes in an email. "In the case of Syria, we have identifiable perpetrators, which cause anger and fear, and then we have statistics about refugees. Identifying and telling the stories of more innocent refugees could make the victim’s case more moving." (Perhaps relevant: Research has shown that suggesting a black person is on the same team as a white person can reduce racial biases.)

Identifying victims in this manner increases the feeling that they are "us" rather then "them," and are therefore worthy of our empathy. "If you plopped a 5-year-old Syrian orphan at Chris Christie’s door, would he really shut it in his face?" Cikara asks. That's an open question.

The passage of time also helps in reducing emotions. Haas offers a very practical solution. "Maybe a better recommendation is just that we should wait a little while for the emotional response to die down a bit before making major decisions about changes to immigration policy, escalation of war," she says.

"It's going to be difficult for people to make well-reasoned decisions when the emotional response is so strong. This is probably better advice than trying to get average citizens to digest statistical information in the aftermath of a terrorist attack, which is usually what professors like to recommend."