The professors at the Music Academy of West Berlin nominated the violin students they thought had the potential for careers as international soloists.
There were 14. Three didn’t speak fluent German and one was pregnant, so the psychologists K. Anders Ericsson, Ralf Krampe and Clemens Tesch-Römer worked with the other ten, whom their paper calls “the best violinists.” They matched them by age and sex with ten “good violinists” from the same department and ten students from the academy’s music education department, which had lower admission standards. The researchers called those ten “the music teachers,” after their likely careers.
Each student was interviewed three times and kept a diary for a week, accounting for practice, lessons, sleep, leisure and the rest.
The diaries showed what you’d expect. The best and the good violinists both practiced alone an average of 24.3 hours that week, about 3.5 hours a day, weekends included. The music teachers practiced 9.3 hours, about 1.3 a day.
They also showed how the practice was spent. Sessions averaged 80 minutes, with no reliable difference between groups. The top two groups simply had more of them, 19.5 a week against 7.1, and their practice rose between 10 a.m. and 2 p.m. And they slept more: 8.6 hours a day on average, against 7.8 for the music teachers. Counting daytime sleep between 9 a.m. and 9 p.m., the top two groups napped 2.8 hours a week. The music teachers napped 0.9.
The authors read this as a limit, not a quirk. Deliberate practice, they wrote, “is an effortful activity that can be sustained only for a limited time each day during extended periods without leading to exhaustion.” Training studies they reviewed showed essentially no benefit from practicing more than four hours a day.
The number the paper became famous for was a different one. By age 18, the best young violinists had accumulated an average of 7,410 hours of practice, against 5,301 for the good violinists and 3,420 for the music teachers. Malcolm Gladwell’s 2008 book Outliers later made a “10,000-hour rule” famous.
In 2019, Brooke Macnamara and Megha Maitra repeated the study with a double-blind procedure. They did not replicate the core finding that accumulated practice lined up with each skill level. Practice still mattered, explaining 26 percent of the differences in performance in their study, against 48 percent in the original comparison. The sleep and nap figures, meanwhile, rest on one diary week from thirty students.