Practice matters a great deal, but it explains only part of the gap between experts — and the '10,000-hour rule' is a popularisation, not a finding.
What the evidence shows
Ericsson, Krampe & Tesch-Römer (1993) showed that elite performers had accumulated far more 'deliberate practice' — effortful, feedback-rich training — than lesser ones, and argued that such practice, not innate talent, drives expertise. The round '10,000 hours' number is Malcolm Gladwell's popularisation of this work, not a threshold the researchers proposed.
A later meta-analysis by Macnamara, Hambrick & Oswald (2014) pooled 88 studies and found deliberate practice explained only about 12% of the variance in performance overall — a lot for games (26%) and music (21%), much less for education (4%) and professions (1%). Practice is necessary and powerful, but it is far from the whole story, and the fixed-hour rule is not supported.
Sources
Ericsson, K. A., Krampe, R. T., & Tesch-Römer, C. (1993). The role of deliberate practice in the acquisition of expert performance.
Psychological Review, 100(3), 363–406
Expert performers had accumulated much more deliberate practice than others; the authors argued practice, not talent, is decisive (they never named a 10,000-hour threshold).
DOI: 10.1037/0033-295X.100.3.363 →Macnamara, B. N., Hambrick, D. Z., & Oswald, F. L. (2014). Deliberate Practice and Performance in Music, Games, Sports, Education, and Professions: A Meta-Analysis.
Psychological Science, 25(8), 1608–1618
Across 88 studies, deliberate practice explained ~12% of performance variance overall — substantial for games and music, small for education and professions.
DOI: 10.1177/0956797614535810 →