The mistake we all make... and the simple experiment that reveals it

A simple experiment questioning people's response to a picture reveals a common error that hampers our decision making. In an extract from his new book, psychologist Richard Nisbett reveals the 'mindware' to help us think smarter

Bill Gates is the richest person in the world. At the age of 19, he dropped out of Harvard to start Microsoft, and in a few short years he made it the most profitable corporation in the world. It's tempting to think that he must be one of the smartest people who ever lived.

Gates is undoubtedly extraordinarily bright. But his pre-college life was blessed, computationally speaking. He was bored at his Seattle school in eighth grade in 1968, so his parents switched him to a private school that happened to have a terminal linked to a mainframe computer. Gates became one of a small number of people anywhere who had substantial time to explore a high-powered computer. His luck continued for the next six years. He was allowed to have free programming time in exchange for testing the software of a local company; he regularly sneaked out of his house at three in the morning to go to the University of Washington computer centre to take advantage of machine time made available to the public at that hour. It is unlikely that there was another teenager in the world who had the kind of access to computers that Gates had.