In the aftermath of the Sandy Hook Elementary School shooting, NRA Executive Vice President Wayne LaPierre insisted that "The only thing that stops a bad guy with a gun is a good guy with a gun."

The Truth About Guns recently tested this idea by organizing a re-enactment of the recent Charlie Hebdo shooting and arming one of the "civilians." Using paintball guns and 40 volunteers, the group ran several simulations, but in no scenario was the "armed civilian" able to take out both shooters.

In fact, no matter which volunteer was given the gun, that person "died" in the simulation — with the exception of the one who fled the scene.

Research on actual gunfights reveals that hitting the target without shooting innocent people requires extensive training, and even then things can go wrong because when you're under attack, your brain often doesn't work the way you expect it will.

Police officers involved in shootings frequently report sensory distortions such as hearing loss and tunnel vision, and afterward, some are surprised to learn they fired their gun at all.

Even New York City police officers involved in gunfights hit their intended targets only 18 percent of the time, according to a Rand study.

Do guns make us safer?

If trained professionals have difficulty shooting accurately under pressure, why then do so many people buy guns for self-defense?

handgunsAccording to psychological studies, guns can make people feel secure, fulfilling one of our most basic desires as outlined by Abraham Maslow's hierarchy of needs.

In fact, the majority of Americans believe a gun in the household makes it safer, according to a 2013 Washington Post-ABC News poll.

"The main benefits of gun ownership are feeling safe, free, independent of the government and powerful," writes Dr. Brad Bushman in "Psychology Today."

Dr. Keith Ablow, a psychiatrist and Fox News contributor, even argues that disarming Americans could cause "potential widespread psychological harm."

Guns might make us feel safer, but studies show they actually make us less safe. Statistically, if you own a gun, it's more likely to be used to kill you or someone you love than a stranger in self-defense.

Still, America is the most heavily armed country in the world, with about 90 guns for every 100 citizens.

This is your brain on guns

Research shows that owning a gun, holding one or even just seeing one can have a significant effect on our perceptions and our behavior.

For nearly 50 years, scientists have been studying the "weapons effect," a phenomenon in which the presence of a weapon or a picture of one can stimulate aggressive behavior.

A 1967 University of Wisconsin study revealed that subjects acted more aggressively in the presence of a gun, and in 2006 researchers found that men exposed to firearms before an experiment had higher levels of testosterone and were three times more likely to act aggressively than participants who weren't exposed to a gun.

In 2009, the University of Pennsylvania examined the link between gun possession and gun assault and found that people with firearms were 4.5 times more likely to be shot than those who didn't carry a gun.

The paper states that one possible reason for this is that "a gun may falsely empower its possessor to overreact," and there's further evidence to support this.

fake gunIn a 2012 study, participants were given either a replica of a firearm or a neutral object, such as a ball, and asked to identify objects other people were holding. Those holding the replica gun were more likely to assume others had a gun and were more likely to "engage in threat-induced behavior" like raising a firearm to shoot.

Spiders, snakes and firearms

Our brains react to guns in much the same way they react to spiders and snakes, a phenomenon known as the threat-superiority effect, meaning that threatening stimuli are particularly powerful at capturing our attention.

In other words, we've evolved to immediately identify threats to our safety so we can avoid them.

Upon seeing a threat, your brain immediately responds, which explains how we're able to instantly spot a gun from among several other objects.

open-carry activistsIt's this automatic response that frequently results in 911 calls when gun owners choose to open-carry, or to legally show their guns instead of concealing them.

Open-carry activists often argue that displaying guns will deter crime, but social scientists have found that all people — criminal or not — are affected by seeing firearms in their daily lives because our brains perceive them as threats.

Pro-gun group Come and Take It America even lists one of its goals as "to condition Americans to feel safe around those of us that carry."

However, social scientsits argue that familiarizing people with firearms so they no longer see them as a threat could be dangerous. After all, we evolved to fear spiders and snakes for good reason.

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Photos: (guns) Andrew Burton/Getty Images (toy gun) woodleywonderworks/flickr, (open-carry activists) Bill Pugliano/Getty Images