Does 10,000 hours of practice make you an expert?

No. The '10,000-hour rule', popularized by Malcolm Gladwell in his book Outliers, says that about 10,000 hours of intense practice will make anyone an expert. But the psychologist whose research inspired it, Anders Ericsson, called the rule 'wrong in several ways'. What matters most, he found, is not the number of hours but the kind of practice: deliberate practice, focused on getting better at whatever you can't do yet.

The number came from Ericsson's famous 1993 study of violinists, which concluded that the best players owed their skill to large amounts of deliberate practice over a decade or more. But 10,000 was simply the average the top violinists had logged by age 20, when they were still nowhere near masters, and the hours needed vary from field to field.

Gladwell's star example was the Beatles, who played live in Hamburg more than 1,200 times between 1960 and 1964. Paul McCartney wasn't fully convinced: plenty of bands in Hamburg put in 10,000 hours and didn't make it, he said, so it's not a cast-iron theory.

Later research cut practice down to size. A large meta-analysis led by Brooke Macnamara found that deliberate practice explained about a quarter of the differences in performance in games like chess, a fifth in music, less in sports, and hardly anything in professions. Practice matters, the authors concluded, but not as much as has been argued.