How Americans Are Living Dangerously

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No one knows how such a set point gets calibrated, but evidence suggests that it is a mix of genetic and environmental variables. In a study at the University of Delaware in 2000, researchers used personality surveys to evaluate the risk-taking behavior of 260 college students and correlated it with existing research on the brain and blood chemistry of people with thrill-seeking personalities or certain emotional disorders. Their findings support the estimate that about 40% of the high-thrill temperament is learned and 60% inherited, with telltale differences in such relevant brain chemicals as serotonin, which helps inhibit impulsive behavior and may be in short supply in people with high-wire personalities.

CAN WE DO BETTER?

Given these idiosyncratic reactions, is it possible to have a rational response to risk? If we can't agree on whether something is dangerous or not or, if it is, whether it's a risk worth taking, how can we come up with policies that keep all of us reasonably safe?

One way to start would to be to look at the numbers. Anyone can agree that a 1-in-1 million risk is better than 1 in 10, and 1 in 10 is better than 50-50. But things are almost always more complicated than that, a fact that corporations, politicians and other folks with agendas to push often deftly exploit.

Take the lure of the comforting percentage. In one study, Slovic found that people were more likely to approve of airline safety-equipment purchases if they were told that it could "potentially save 98% of 150 people" than if they were told it could "potentially save 150 people." On its face this reaction makes no sense, since 98% of 150 people is only 147. But there was something about the specificity of the number that the respondents found appealing. "Experts tend to use very analytic, mathematical tools to calculate risk," Slovic says. "The public tends to go more on their feelings."

There's also the art of the flawed comparison. Officials are fond of reassuring the public that they run a greater risk from, for example, drowning in the bathtub, which kills 320 Americans a year, than from a new peril like mad cow disease, which has so far killed no one in the U.S. That's pretty reassuring--and very misleading. The fact is that anyone over 6 and under 80--which is to say, the overwhelming majority of the U.S. population--faces almost no risk of perishing in the tub. For most of us, the apples of drowning and the oranges of mad cow disease don't line up in any useful way.

But such statistical straw men get trotted out all the time. People defending the safety of pesticides and other toxins often argue that you stand a greater risk of being hit by a falling airplane (about 1 in 250,000 over the course of your entire life) than you do of being harmed by this or that contaminant. If you live near an airport, however, the risk of getting beaned is about 1 in 10,000. Two very different probabilities are being conflated into one flawed forecast. "My favorite is the one that says you stand a greater risk from dying while skydiving than you do from some pesticide," says Susan Egan Keane of the Natural Resources Defense Council. "Well, I don't skydive, so my risk is zero."