On Tuesday, as millions of people from Delaware to Connecticut awoke to homes and businesses damaged or destroyed, with no electricity and no certainty about when they’d have it back, millions of others in Boston and Washington awoke to a wet, breezy morning and a seemingly unnecessary day off.

With no more than a lot of leaves and branches on the ground and an occasional fallen tree, schools, businesses and public transportation remained closed in many areas that had braced for Superstorm Sandy but fortunately escaped the worst of its power. And while New York, which suffered so badly, looked smart for having taken such precautions, many people thought Washington, Boston and Philadelphia had overreacted.

From a public safety standpoint, every city that prepared was right to do so. But this contrast in public opinion highlights the subjective nature of individual risk perception.

Like Goldilocks with her porridge, sometimes our perceptions of risk are too hot — we worry more than the evidence warrants. Sometimes our perceptions are too cold — we don’t worry as much as the evidence warns. And sometimes our fears are just right. But given how important it is to our health and safety to assess risk just right, why do we so often get it wrong?

With natural disasters, many people don’t worry enough. General preparation for such events is poor, and only urgent alarms of an impending Frankenstorm send people shopping for batteries and bottled water. This time, while some prepared and others evacuated high-risk areas in New York and New Jersey, many didn’t take Sandy’s risks seriously or were “just plain stupid,” as New Jersey Gov. Chris Christie put it, and stayed in harm’s way.

Hospitals in New York lost power because electrical systems in their basements weren’t protected, and untested backup generators failed, too. Car owners left their vehicles on the streets and in the underground parking garages of Lower Manhattan and low-lying areas of Brooklyn and — surprise! — later found them submerged.

Why don’t people take natural disasters seriously enough? Some tell themselves that “it won’t happen to me” or “I’ve been through these storms before.” Psychologists call this optimism bias.

“I’m ready,” some say, reflecting a misplaced confidence that their flashlights, sandbags and backup generators will protect them from the ferocity of Mother Nature. The more control over a risk you think you have, the less worrisome it feels, no matter how false that sense of control might be.

We also tend to worry less about risky behaviors that afford us some benefit — such as living on the coast, where the beauty of the view causes some to play down the danger of ocean storms. Those who stay put to “protect my property” are also weighing risk vs. benefit, as are people who go down to the shore to watch the waves because “I may never see this again in my life!” And that may turn out to be true because of the dangerous thrill-seeking they’re doing.

Finally there is the problem of innumeracy — illiteracy about numbers. We’re lousy at probabilities. It’s a good bet (though I can give no odds) that most people who experienced this “once in a century” storm figure that such freakish weather is not likely to happen again soon. Sorry, but next year’s weather hasn’t gotten that memo. There are probabilistic patterns for assessing the risk of natural disasters over the long term. But the long term is much longer than our very brief lifetimes.

On the other hand, Sandy also demonstrated why it’s so common to worry too much. A friend of mine who lives on Long Island complained Sunday afternoon, when the worst of the storm was more than a day away, that his wife had become addicted to “storm porn.” Like many, she couldn’t stop watching television and scanning news sites and social media, far more than she needed to in order to stay informed.

This phenomenon is fueled in part by the neural roots of risk perception: When potential threats trigger a fight-or-flight response, stress hormones heighten our sensitivity to any additional hint of danger, creating a positive feedback loop. The more worried we are, the more readily we worry.

People are also naturally “loss averse.” In economics, this means that a loss hurts more than an equivalent gain feels good. In health and safety terms, loss aversion makes us instinctively precautionary, so risk and loss carry more emotional power than does a benefit. Loss aversion is what turns some of us into storm-coverage addicts.

That brings us to the purveyors of storm porn — the media, both news and social. News coverage is far more likely to warn us that the sky is falling than to reassure us that it isn’t. If it scares, it airs, because anything that threatens us is pretty sure to grab our attention. If weather forecasts include days of Frankenstorm predictions, the future is sure to feel pretty frightening. (To be fair, despite their breathless alarmism, the news media did make the public aware of Sandy, helping us prepare.)

And even if you can avoid the traditional news, it’s hard to escape the social “news” from the virtual world to which we are so connected. The flood of tweets and Facebook posts about the storm further magnified the fear.

Our personal risk assessments aren’t all emotion and instinct, though. Reason also has a say. A lot of people got their perception of Sandy just right. They prepared. They protected their property as best they could. They evacuated. They even understood in Washington and Boston on that mild Tuesday that decisions about school, business and transit shutdowns must be planned for and announced in advance, and that erring on the side of caution makes sense.

But for many, their risk perception was too hot or too cold, and that matters for what lies ahead. How afraid Sandy made us — before, during and after — will shape how we respond to the next natural disaster. Some who suffered serious losses might be yet more loss averse when future storms loom. For others, optimism bias could lead them to think: “I survived the last one. Nothing bad will happen to me.”

Risk perception determines how prepared we are — or aren’t. It determines whether we follow government evacuation orders or make sure we have candles, working flashlights and bottled water. It determines whether we buy insurance and how much (flood insurance take-up rates are ridiculously low). Our intuitive risk perceptions shape how much we trust the government to protect us, which in turn bears on how willing we are to support the government agencies that have those responsibilities.

So the overreaction or underreaction to Sandy’s dark clouds may offer a silver lining: Shedding light on why we sometimes get risk wrong could help us to get closer next time to personal risk assessment that is just right.


David Ropeik is a consultant in risk perception and risk management and the author of “How Risky Is It, Really?: Why Our Fears Don’t Always Match the Facts.”

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David Ropeik is a consultant in risk perception and risk management, and author of “How Risky Is it, Really? Why Our Fears Don’t Always Match the Facts.”