It’s hard work being prey. Watch the birds at a feeder. They’re constantly on alert, and will fly away from food — from easy nutrition — at the slightest movement or sound. Given that I’ve never, ever seen a bird plucked from a feeder by a predator, it seems like a whole lot of wasted effort against a small threat.
Assessing and reacting to risk is one of the most important things a living creature has to deal with. The amygdala, an ancient part of the brain that first evolved in primitive fishes, has that job. It’s what’s responsible for the fight-or-flight reflex. Adrenaline in the bloodstream, increased heart rate, increased muscle tension, sweaty palms; that’s the amygdala in action. You notice it when you fear a dark alley, have vague fears of terrorism, or worry about predators stalking your children on the Internet. And it works fast, faster than consciousnesses: show someone a snake and their amygdala will react before their conscious brain registers that they’re looking at a snake.
Fear motivates all sorts of animal behaviors. Schooling, flocking, and herding are all security measures. Not only is it less likely that any member of the group will be eaten, but each member of the group has to spend less time watching out for predators. Animals as diverse as bumblebees and monkeys both avoid food in areas where predators are common. Different prey species have developed various alarm calls, some surprisingly specific. And some prey species have even evolved to react to the alarms given off by other species.
Evolutionary biologist Randolph Nesse has studied animal defenses, particularly those that seem to be overreactions. These defenses are mostly all-or-nothing; a creature can’t do them halfway. Birds flying off, sea cucumbers expelling their stomachs, and vomiting are examples. Using signal-detection theory, Nesse showed that all-or-nothing defenses are expected to have many false alarms. “The smoke detector principle shows that the overresponsiveness of many defenses is an illusion. The defenses appear overresponsive because they are ‘inexpensive’ compared to the harms they protect against and because errors of too little defense are often more costly than errors of too much defense.” So, according to the theory, if flight costs 100 calories, both in flying and lost eating time, and there’s a 1 in 100 chance of being eaten if you don’t fly away, it’s smarter for survival to use up 10,000 calories repeatedly flying at the slightest movement even though there’s a 99 percent false-alarm rate. Whatever the numbers happen to be for a particular species, it has evolved to get the trade-off right.
This makes sense, until the conditions that the species evolved under change quicker than evolution can react to. Even though there are far fewer predators in the city, birds at my feeder react as if they were in the primeval forest. Even birds safe in a zoo’s aviary don’t realize that the situation has changed.
Humans are both no different and very different. We, too, feel fear and react with our amygdala, but we also have a conscious brain that can override those reactions. And we too live in a world very different from the one we evolved in. Our reflexive defenses might be optimized for the risks endemic to living in small family groups in the East African highlands in 100,000 B.C. — not Tokyo in 2009. But we can go beyond fear, and actually think sensibly about security.
Far too often, we don’t. We tend to be poor judges of risk. We overreact to rare risks, we ignore long-term risks, we magnify risks that are also morally offensive. We get risks wrong — threats, probabilities and costs — all the time. When we’re afraid, really afraid, we’ll do almost anything to make that fear go away. Politicians and marketers, both, have learned to push that fear button to get us to do what they want.
One night last month, I was awoken from my hotel-room sleep by a loud, piercing alarm. There was no way I could ignore it, but I weighed the risks and did what any reasonable person would do under the circumstances: I stayed in bed and waited for the alarm to be turned off. No point getting dressed, walking down 10 flights of stairs, and going outside into the cold for what invariably would be a false alarm — serious hotel fires are very rare. Unlike the bird in an aviary, I knew better.
You can disagree with my risk calculus, and I’m sure many hotel guests walked downstairs and outside to the designated assembly point. But it’s important to recognize that the ability to have this sort of discussion is uniquely human. And we need to have the discussion repeatedly, whether the topic is the monitoring of our children’s Web-surfing habits, outsourcing our corporate IT infrastructure, or even the potential military invasion of another country. These things aren’t part of our evolutionary history; we have no natural sense of how to respond to them. Our fears are often calibrated wrong, and reason is the only way we can override them.
Bruce Schneier is a security technologist. His latest book is “Schneier on Security.” Read about him at schneier.com