In 2008, Malcolm Gladwell published Outliers, which popularized the work of Dr. K. Anders Ericsson through the “10,000 Hour Rule”, suggesting that expert-level performance in any field can be achieved through ten thousand hours of practice. Based on Ericsson’s 1991 study of violinists at a music academy in Berlin, this now-famous rule has taken on a life of its own. But it’s not so simple.

This year, Ericsson published a book (Peak) clarifying his research and explaining the caveats to this so-called rule:

1. There’s nothing special about the number 10,000: that’s just the number of hours that the top violinists Ericsson studied had accumulated by age 20. And while these were very promising students, they were not yet masters of the violin. “Pianists who win international piano competitions tend to do so when they’re around thirty years old, and thus they’ve probably put in about twenty thousand to twenty-five thousand hours of practice by then; ten thousand hours is only halfway down that path.” Ericsson also cites his first major research subject, Steve Faloon, who he helped become “the very best person in the world at memorizing strings of digits after only about two hundred hours of practice.” Certain obscure types of expertise don’t require 10,000 hours.
2. Ten thousand was only an average number of hours that the top violinists had put in by age 20. Half of the violinists in the group had put in less than 10,000 hours; so 10,000 is not some hard minimum number as the rule implies.
3. Most crucially (in my opinion), Gladwell didn’t properly distinguish between the general notion of “practice” and Andersson’s very specific definition of “deliberate practice”, which involves focused, individualized, goal-oriented training under a teacher or coach. (Here’s the chapter from The Art of Self-Directed Learning where I explained the difference.) The Beatles, for example, put in many hours of “practice” by playing shows in Hamburg, but that’s not the same as “focused, goal-driven practice that is designed to address certain weaknesses and make certain improvements.” (The Beatles success may be better explained by their songwriting, so it’s more relevant to identify what John Lennon and Paul McCartney did to develop their songwriting skills.)
4. Although Gladwell didn’t say it himself, the rule implied that almost anyone can become an expert in a given field by putting in 10,000 hours. But to prove this, Ericsson would have needed to “put a collection of randomly chosen people through ten thousand hours of deliberate practice on the violin and then see how they turned out.” His original study just showed that those admitted to the Berlin music academy, the best students had put in more hours of solitary deliberate practice.

Given all these caveats, Ericsson acknowledges that the general spirit of the rule is correct: “becoming accomplished in any field in which there is a well-established history of people working to become experts requires a tremendous amount of effort exerted over many years. It may not require exactly ten thousand hours, but it will take a lot.” There are no shortcuts, and there are no insta-geniuses. Everyone needs to put in their time.

(All quotes from Chapter 4 of Peak.)