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Which risks get excessive attention and which get overlooked depends on a hierarchy of factors. Perhaps the most important is dread. For most creatures, all death is created pretty much equal. Whether you're eaten by a lion or drowned in a river, your time on the savanna is over. That's not the way humans see things. The more pain or suffering something causes, the more we tend to fear it; the cleaner or at least quicker the death, the less it troubles us. "We dread anything that poses a greater risk for cancer more than the things that injure us in a traditional way, like an auto crash," says Slovic. "That's the dread factor." In other words, the more we dread, the more anxious we get, and the more anxious we get, the less precisely we calculate the odds of the thing actually happening. "It's called probability neglect," says Cass Sunstein, a University of Chicago professor of law specializing in risk regulation.
The same is true for, say, AIDS, which takes you slowly, compared with a heart attack, which can kill you in seconds, despite the fact that heart disease claims nearly 50 times as many Americans than AIDS each year. We also dread catastrophic risks, those that cause the deaths of a lot of people in a single stroke, as opposed to those that kill in a chronic, distributed way. "Terrorism lends itself to excessive reactions because it's vivid and there's an available incident," says Sunstein. "Compare that to climate change, which is gradual and abstract."
Unfamiliar threats are similarly scarier than familiar ones. The next E. coli outbreak is unlikely to shake you up as much as the previous one, and any that follow will trouble you even less. In some respects, this is a good thing, particularly if the initial reaction was excessive. But it's also unavoidable given our tendency to habituate to any unpleasant stimulus, from pain and sorrow to a persistent car alarm.
The problem with habituation is that it can also lead us to go to the other extreme, worrying not too much but too little. Sept. 11 and Hurricane Katrina brought calls to build impregnable walls against such tragedies ever occurring again. But despite the vows, both New Orleans and the nation's security apparatus remain dangerously leaky. "People call these crises wake-up calls," says Dr. Irwin Redlener, associate dean of the Mailman School of Public Health at Columbia University and director of the National Center for Disaster Preparedness. "But they're more like snooze alarms. We get agitated for a while, and then we don't follow through."
THE COMFORT OF CONTROL