Psychologist Anders Ericsson’s original study, on violin students in Berlin, found that the best performers had accumulated, by age 20, roughly 10,000 hours of practice on average – but deliberate, structured practice, not just hours spent randomly.
Malcolm Gladwell’s book “Outliers” popularized the number as an almost guaranteed rule for mastery in any field, significantly simplifying the original findings.
Ericsson himself publicly criticized this simplification years later, pointing out that his study was about the quality of practice and individual variation, not a guaranteed magic threshold for anyone.
A number can become famous precisely for its simplified version, not for the more nuanced, real one.
See also: