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Farah Stockman

Deadly certain

George Zimmerman’s fatal flaw was his sense of certainty

Anthony Russo for the Boston Globe

IN 2009, the ABC show “What Would you Do?’’ hired actors to pretend to steal a bike in an upscale public park to see how onlookers would react.

About 100 people walked past the first actor — a white teenager in jeans - as he hacked away at a chain. Many — including three black women — assumed he was a park official. But when he was replaced by a black actor, an angry crowd converged. So certain were they that he was up to no good that one woman snapped a picture of him and yelled, “Gotcha.’’ One man called the police, while another tried to take his tools. The more people gathered, the more certain they grew that he had to be stopped.

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“I was surprised at how fast it was,’’ the black actor, known as Matlok, told me. “Less than a minute.’’

Science shows that our unconscious brains make snap judgments about strangers within seconds, based entirely on how they look. Once we form an opinion, we magnify evidence that confirms what we already believe and dismiss what doesn’t fit.

Anyone who doubts that Trayvon Martin’s race played a role in the assumptions that George Zimmerman made about him should watch the “bike thief’’ clip on YouTube.

We may never know the details of the altercation that took place in the fateful moments before Zimmerman pulled the trigger. But one thing is clear: Zimmerman — whose father is white and whose mother is from Peru — considered Martin suspicious from the moment he laid eyes on him.

Some say that Zimmerman’s greatest sin was his gut reaction to Martin’s skin color. But you can’t control your subconscious mind, no matter how hard you try. Millions of Americans would have had the same fleeting thoughts, whether they admit it or not.

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Others conclude that Zimmerman’s erred by acting on his hunch. But do we want to live in a world where neighbors do nothing when they suspect that something bad is about to happen? Where people don’t try to stop a thief from stealing someone else’s bike?

It seems that Zimmerman’s fatal flaw was his sense of certainty. Instead of trying to figure out if Martin was a threat, he had already made up his mind. Zimmerman was so certain that Martin was dangerous that he called the police, followed him, and eventually shot him.

“This guy looks like he’s up to no good, or on drugs or something,’’ Zimmerman told the 911 operator. “It’s raining and he’s just walking around . . . Something’s wrong with him.’’

What made Zimmerman so deadly certain? According to Robert Burton, a neurologist and author of “On Being Certain: Believing You Are Right, Even When You’re Not,’’ certainty is one of the most powerful sensations a person can feel. It is generated in our subconscious brain, and it isn’t based on rational deduction.

Sometimes certainty is good. “It serves as a huge motivation,’’ he said. Without certainty, we’d be paralyzed because we’d doubt every course of action.

But too much certainty too soon poses great risks. It can cause doctors to misdiagnose illnesses, politicians to stick to inflexible positions, and ordinary people to take disastrous actions based on biases they don’t even comprehend.

Zimmerman, who wanted to be a cop, had a long track record of taking zealous, impulsive action. He once followed a supermarket shoplifter until police arrived to make an arrest. Another time, he chased a reckless driver so he could write down his license plate number for the cops. After a rash of robberies in his neighborhood, Zimmerman bought a dog and patrolled with a gun tucked in his pants.

“If you were to dissect Zimmerman, you might say that he is prompted by a moral fervor that seems to tell him a clear-cut right versus wrong,’’ Burton said. That can be an admirable trait. But it can also be dangerous. Certainty comes from the same part of the brain that makes gambling and taking cocaine feel good.

People can get drunk on it, addicted to it. “The more times you feel certain, the more it becomes a great pleasure,’’ Burton said. “That is why it is so hard for people to change their minds.’’

Therein lies the great irony at the heart of this tragedy: Zimmerman was so sure he was acting like a hero that he became a national villain.

Farah Stockman can be reached at fstockman@globe.com. Follow her on twitter @fstockman.

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