Half of Berlin's Best Young Violinists Hadn't Hit 10,000 Hours by 20

Seven thousand four hundred and ten hours was the average solo practice of Berlin’s best violin students by age 18, in the 1993 study behind the 10,000-hour rule; by 20 the average reached about 10,000, and, by Ericsson’s later account, about half of them had not got there. The paper, Ericsson, Krampe and Tesch-Römer in Psychological Review, contained no rule and no promise. It contained a table of averages, which is a less marketable thing.

Here is what the table held. Students at the West Berlin music academy were sorted by their teachers into three groups: likely international soloists, “good” violinists headed for orchestras, and future music teachers. The authors estimated how many hours each had practiced alone. By age 18 the best group averaged 7,410 hours, the good group 5,301, the teachers 3,420. By age 20 the best group averaged roughly 10,000. That is the entire origin of the number: one mean, for one group of ten, estimated mostly from interviews and diaries after the fact.

What did Gladwell change?

Malcolm Gladwell’s Outliers (2008) turned the group average into a pass mark: put in 10,000 hours, then you are an expert. Ericsson’s reply in Peak (2016) was that this is a simplification of his work. Coverage of the book reports him calling it a popularized but simplistic version of his work. He listed several problems, and three are worth lining up.

First, an average is not a minimum. About half of the ten best violinists had not reached 10,000 hours by 20. Ericsson himself noted that 10,000 was the average for the best group, and that about half of those ten had not reached it by 20.

Second, the students had been playing since childhood and landed in the top group because they were already the best. Nobody in that study went from zero to elite in 10,000 hours. Third, Ericsson has called the number itself arbitrary. It is where one group’s average stood at age 20, and a round figure is easier to put on a book cover than the real data.

Did the Beatles play 10,000 hours in Hamburg?

Gladwell’s second pillar was the Beatles. In Outliers he said the band performed live about 1,200 times by 1964, sometimes up to eight hours a night in Hamburg, and that the total came close to 10,000 hours. Mark Lewisohn’s Tune In (2013) puts Hamburg stage time at roughly 1,100 hours over about 270 nights. The 270 nights appear in Outliers too, so the two books agree on the calendar and disagree about how many hours fit in it. Either way the apprenticeship was brutal. It was also mostly performing covers for a rowdy crowd, which by Ericsson’s definition is not much deliberate practice.

What does the evidence say about how much practice explains?

The cleanest answer is Macnamara, Hambrick and Oswald in Psychological Science (2014), a meta-analysis across five domains. The share of performance differences explained by deliberate practice was 26 percent in games, 21 percent in music, 18 percent in sports, 4 percent in education and under 1 percent in professions. Pooled across everything it came to roughly 12 percent.

In music, the field where the 10,000-hour idea began, practice accounts for about a fifth of the differences between players. The other four-fifths is something else: when they started, who taught them, how well they practiced, genes, luck, or error in how hours were counted. A fifth of the variation is still large for a single behavior you can control, so nobody should read this as permission to put the violin down.

Ericsson objected that the pooled studies measured general practice rather than deliberate practice and the data were retrospective. That is a fair complaint. A review that treats an hour of strumming and an hour of isolating one bad shift in the left hand as the same quantity will understate the effect of the second. Whether a cleaner measure would climb to Ericsson’s claimed numbers is unsettled, and I do not know which side the next decade of data favors.

So what is useful here?

For someone building a daily practice, the useful part is not the number but the shape of the Berlin data. The hours that counted were solo, effortful and aimed at something the player could not yet do. The total was only the visible residue of that way of working.

Which suggests a mildly rude instruction: counting hours is the weakest metric available, because hours reward showing up and sitting near the instrument. A better count is the number of sessions in which you named one thing that was failing and worked on only that. Five 40-minute sessions with a named target will probably teach you more than a ten-hour weekend of general noodling, and none of the data above contradicts that.

The original paper also has a reverse-causation wrinkle. The students who were already better got more teacher attention and more reasons to practice, so some of the hours followed from being good. A log of hours tells you where you have been. If your total is climbing and you are not improving, the total is the wrong thing to be proud of.

The same tidy-number-outruns-its-source problem shows up in the UCL study behind the 21-day habit rule and in the 1%-a-day arithmetic attached to British Cycling. For practice at its least heroic, there is a parent’s log of 30 dawn swim practices, where getting to the pool was the problem being solved.

Arguments people bring to the 10,000 rule

Is there a number of hours that guarantees expertise? No. Macnamara, Hambrick and Oswald (2014) found that deliberate practice explained roughly 12 percent of performance differences when studies across domains were pooled, so two people with the same hours can end up in very different places.

Is deliberate practice the same thing as just practicing a lot? No. In Ericsson’s definition it is effortful work on a task chosen to fix a particular weakness, usually with a teacher or fast feedback. A violinist who plays through a favorite piece for two hours is practicing, but by that definition is not doing deliberate practice. Part of the dispute with Macnamara’s team is about whether the studies they pooled measured the narrow thing or the broad one.

Does the 10,000-hour rule apply to learning something casual, like a language or guitar for fun? The 1993 study only covered students at an elite music academy aiming for professional careers, so it says nothing direct about hobbyists. It cannot say how long a recreational goal takes, because nobody in it had one.

Does the 1993 study say how quickly someone improves? No. It compared groups of students at fixed ages from retrospective estimates and did not follow anyone from beginner to expert. It can say that the best group had logged more hours when measured, but not whether hour 9,000 mattered more than hour 900.

Would having a friend watch the practice session happen change whether you do it? DontSnooze (iOS only) is one way to try.

The same trap runs through success advice generally, as Abraham Wald and the missing bullet holes shows.