You may have heard of the '10,000-hour rule'. The rule says that if you practice for 10,000 hours, you will become an expert. It came from a 1993 study of violin students in Berlin.

But in 2019, other researchers repeated the study, and the main result did not appear again. Practice is important, but it does not explain everything. For language learning, how you practice is as important as how long you practice.

The famous '10,000-hour rule' comes from a 1993 study by Ericsson and his colleagues. They found that the best violin students at a music school in Berlin had practiced alone for about 10,000 hours by the age of 20.

However, when the researchers Macnamara and Maitra repeated the study in 2019, the main result was not replicated. A 2014 meta-analysis of 88 studies also showed that practice explained 26% of the differences in performance in games, 21% in music and 18% in sports, but only 4% in education. For language learners, researchers suggest 'desirable difficulties', such as spacing out reviews and practicing recall.

The 10,000-hour rule goes back to a 1993 study. Ericsson and colleagues divided violin students at a Berlin music academy into three skill levels and asked them to estimate their past practice. The best violinists had built up around 10,000 hours of solitary practice by age 20, and the researchers concluded that deliberate practice, focused effort designed to improve performance, explained most individual differences.

A bestselling book made the figure famous, although Ericsson himself objected to treating it as a magic number. In 2019, Macnamara and Maitra repeated the study with a few changes to the method. The central finding, that practice neatly matched skill level, did not hold up. Practice still had a sizeable effect, but far smaller than first reported.

A 2014 meta-analysis of 88 studies had already found that deliberate practice explained 26 percent of performance differences in games, 21 percent in music, 18 in sports, 4 in education and under 1 percent in professions. The original study also relied on people recalling their past practice, and researchers disagree about its definition. For language learners, time is necessary but not sufficient. Spacing out study, mixing problem types and practicing retrieval can each make an hour count for more.