Risk: The Science and Politics of Fear, By Dan Gardner

A stimulating new book claims that our modern minds struggle against our primitive instincts

I recently applied for a free smoke alarm from the London Fire Brigade, who insisted that it could not put the device in the post and risk me fitting it incorrectly; a trained firefighter would visit my property to do the job. However, I was warned that "the Fire Brigade has a legal duty to provide a safe working environment to protect the health of its staff" and that "if a smoke-free environment cannot be provided, our staff will need to assess the situation before proceeding". This shows an eccentric attitude towards danger, to say the least. While fire-fighters are expected to tackle infernos created by burning plastics and industrial solvents, God forbid they should ever catch a lungful of Marlboro Light.

According to Dan Gardner, such madness demonstrates that the modern world is too much for the Stone Age brain – or "Gut" as the author calls it – to comprehend. The modern mind – or "Head" – is locked in a battle with the gut to react rationally to the supernormal stimuli the media throws at us. Our instincts evolved to cope with a far simpler environment and their sense of proportion is easily thrown. This happened after the 9/11 terrorist attacks when, according to one calculation, an extra 1,595 Americans died on the roads as a result of avoiding domestic flights. If a jet flew into a tower every month for a year, then someone who flew once a month would have a 1 in 135,000 chance of being killed in a hijacking compared to a 1 in 6,000 of being killed in a car crash.

Rules of thumb that worked well on the savannah lead us astray in more complex situations. One such is the Rule of Typical Things, which is the basis for stereotypes that allow us to make reliable snap judgments. Prejudice against black and orange stripes saved many a caveman from the jaws of a tiger, but similar considerations of colour are less helpful in a multi-ethnic society. Unfortunately, our instincts need only the slightest excuse to overrule our heads. Head tries its best, but even when it wins, Gut behaves like a recently liberated populace that reverts to its old ways of homophobia and genital mutilation as soon as the marines have boarded the transports home.

According to one study, people are willing to pay more for insurance covering "terrorist acts" than for death from "all possible causes". In another famous experiment, subjects are told that a student named Linda is deeply concerned with issues of discrimination and social justice and participates in anti-nuclear demonstrations. They are then asked to rate the likelihood of a number of further descriptions that include the following: "Linda is a bank teller" and "Linda is a bank teller and is active in the feminist movement." The overwhelming majority of respondents judge the latter conjunction to be more probable than "Linda is a bank teller". Yet this cannot be true, since the probability of a conjunction cannot be greater than the probability of one of its parts. But even when one is aware of the logic, it is extremely difficult to quiet one's intuition that Linda has to be an active feminist as well as a bank teller.

Marketing gurus and cynical politicians collude with the Gut to keep us in a constant state of overblown fear in order to win votes and make a buck. The author notes that when Martin Rees, the astronomer royal, wrote a book about the threats raised by new scientific advances titled Our Last Century?, his publishers first removed the question mark, then changed "Century" to "Hour".

Where writers such as Richard Dawkins, Christopher Hitchens and Francis Wheen have been content largely to enumerate the errors of less rational men and women, Dan Gardner has collated part of what we need to diagnose the problem. If sceptics spent less time moaning about the propensity of their fellows to believe what they want to believe and more time asking why they do so, there might not be such a crisis of reason in the West today.