Anecdotes are entertaining and can be pretty convincing — I’ve been caught up in many of them myself — but they’re no substitute for scientifically-derived evidence. Michael Shermer explains why they’re so powerful:

The reason for this cognitive disconnect is that we have evolved brains that pay attention to anecdotes because false positives (believing there is a connection between A and B when there is not) are usually harmless, whereas false negatives (believing there is no connection between A and B when there is) may take you out of the gene pool. Our brains are belief engines that employ association learning to seek and find patterns. Superstition and belief in magic are millions of years old, whereas science, with its methods of controlling for intervening variables to circumvent false positives, is only a few hundred years old. So it is that any medical huckster promising that A will cure B has only to advertise a handful of successful anecdotes in the form of testimonials.

[Scientific American via RichardDawkins.net]

Old habits die hard. Unfortunately, humans don’t. What’s the Harm? documents cases where critical thinking — as opposed to magical thinking, superstition, or trust in authority — could have saved people’s health, money, or life.