Our brains are hard-wired to make poor choices about harm prevention.

Daniel Gilbert, always an engaging writer, has done a nice piece in Nature "Buried by bad decisions" and I pass on a few clips here:

…should we do everything in our power to stop global warming? To make sure terrorists don't board aeroplanes? To keep Escherichia coli out of the food supply? These seem like simple questions with easy answers only because they describe what we will do without also describing what we won't. When both are made explicit — should we keep hamburgers safe or aeroplanes safe? — these simple questions become vexing. Harm prevention often seems like a moral imperative, but because every yes entails a no, it is actually a practical choice. ..research shows that when human beings make decisions, they tend to focus on what they are getting and forget about what we are forgoing. For example, people are more likely to buy an item when they are asked to choose between buying and not buying it than when they are asked to choose between buying the item and keeping their money “for other purchases”. Although “not buying” and “keeping one's money” are the same thing, the latter phrase reminds people of something they know but typically fail to consider: buying one thing means not buying another.

In the seventeenth century, Blaise Pascal and Pierre de Fermat derived the optimal strategy for betting on games of chance, and in the process demonstrated that wise choices about harm prevention are always the product of two estimates: an estimate of odds (how likely is the harmful event?) and an estimate of consequences (how much harm will it cause?). If we know which harm is most likely and which harm is most severe, then we know which harm to prevent. We should spend less to prevent a natural disaster that will probably leave 3,000 people homeless than a communicable disease that will certainly leave 3 million people dead, and this is perfectly obvious to everyone….Except when it isn't.

Our brains were optimized for finding food and mates on the African savannah and not for estimating the likelihood of a core breach or the impact of overfishing. Nature has installed in each of us a threat-detection system that is exquisitely sensitive to the kinds of threats our ancestors faced — a slithering snake, a romantic rival, a band of men waving sticks — but that is remarkably insensitive to the odds and consequences of the threats we face today…Because we specialize in understanding other minds, we are hypersensitive to the harms those minds produce..we worry more about shoe-bombers than influenza, despite the fact that one kills roughly 400,000 people per year and the other kills roughly none. We worry more about our children being kidnapped by strangers than about becoming obese, despite the fact that abduction is rare and diabetes is not.

We are especially concerned when threats human agents produce are to our dignity, values and honor…Our obsession with morality can also discourage us from embracing practical solutions to pressing problems. The taboo against selling our bodies means that people who have money and need a kidney must die so that people who need money and have a spare kidney can starve. Economic models suggest that drug abuse would decline if drugs were taxed rather than banned7, but many people have zero tolerance for policies that permit immoral behaviour even if they drastically reduce its frequency.

Our species' sociality has always been its greatest advantage, but it may also be its undoing. Because we see the world through a lens of friends and enemies, heroes and villains, alliances and betrayals, virtue and vice, credit and blame, we are riveted by the dramas that matter least and apathetic to the dangers that matter most. We will change our lives to save a child but not our light bulbs to save them all.

What are we to do about the mismatch between the way we think and the problems we should be thinking about? One solution is to frame problems in ways that appeal to our nature. For example, when threats are described as moral violations, apathy often turns to action. Texas highways were awash in litter until 1986, when the state adopted a slogan — 'Don't mess with Texas' — that made littering an insult to the honour of every proud Texan, at which point littering decreased by 72%.

The other way to deal with the mismatch between the threats we face and the way we think is to change the way we think. People are capable of thinking rationally about odds and consequences, and it isn't hard to teach them. Research shows that a simple five-minute lesson dramatically improves people's decision-making in new domains a month later10, and yet that is five minutes more than most people ever get. We teach high-school students how to read Chaucer and do trigonometry, but not how to think rationally about the problems that could extinguish their species.