Humans have a perplexing 
tendency to fear rare threats such as shark attacks while blithely 
ignoring far greater risks like 
unsafe sex and an unhealthy diet. Those illusions are not just 
silly—they make the world a more dangerous place.

We like to think that humans are supremely logical, making decisions on the basis of hard data and not on whim. For a good part of the 19th and 20th centuries, economists and social scientists assumed this was true too. The public, they believed, would make rational decisions if only it had the right pie chart or statistical table. But in the late 1960s and early 1970s, that vision of homo economicus—a person who acts in his or her best interest when given accurate information—was knee­capped by researchers investigating the emerging field of risk perception. What they found, and what they have continued teasing out since the early 1970s, is that humans have a hell of a time accurately gauging risk. Not only do we have two different systems—logic and instinct, or the head and the gut—that sometimes give us conflicting advice, but we are also at the mercy of deep-seated emotional associations and mental shortcuts.

People are likely to react with little fear to certain types of objectively dangerous risk that evolution has not prepared them for, such as guns, hamburgers, automobiles, smoking, and unsafe sex, even when they recognize the threat at a cognitive level.

Even if a risk has an objectively measurable probability—like the chances of dying in a fire, which are 1 in 1,177—people will assess the risk subjectively, mentally calibrating the risk based on dozens of subconscious calculations. If you have been watching news coverage of wildfires in Texas nonstop, chances are you will assess the risk of dying in a fire higher than will someone who has been floating in a pool all day. If the day is cold and snowy, you are less likely to think global warming is a threat.

Our hardwired gut reactions developed in a world full of hungry beasts and warring clans, where they served important functions. Letting the amygdala (part of the brain’s emotional core) take over at the first sign of danger, milliseconds before the neocortex (the thinking part of the brain) was aware a spear was headed for our chest, was probably a very useful adaptation. Even today those nano-pauses and gut responses save us from getting flattened by buses or dropping a brick on our toes. But in a world where risks are presented in parts-per-billion statistics or as clicks on a Geiger counter, our amygdala is out of its depth.

A risk-perception apparatus permanently tuned for avoiding mountain lions makes it unlikely that we will ever run screaming from a plate of fatty mac ’n’ cheese. “People are likely to react with little fear to certain types of objectively dangerous risk that evolution has not prepared them for, such as guns, hamburgers, automobiles, smoking, and unsafe sex, even when they recognize the threat at a cognitive level,” says Carnegie Mellon University researcher George Loewenstein, whose seminal 2001 paper, “Risk as Feelings,” debunked theories that decision making in the face of risk or uncertainty relies largely on reason. “Types of stimuli that people are evolutionarily prepared to fear, such as caged spiders, snakes, or heights, evoke a visceral response even when, at a cognitive level, they are recognized to be harmless,” he says. Even Charles Darwin failed to break the amygdala’s iron grip on risk perception. As an experiment, he placed his face up against the puff adder enclosure at the London Zoo and tried to keep himself from flinching when the snake struck the plate glass. He failed.

Read on.