How much of expert performance does practice explain?

A fifth to a quarter, in the domains where it does most. A meta-analysis covering every major domain where deliberate practice has been studied put it at 26 percent of the variance in performance for games and 21 percent for music. Sports came in at 18 percent, education at 4 and professions at less than 1.

The proposal is more than twenty years old. Individual differences in performance in domains like music, sports and games largely reflect individual differences in the amount of deliberate practice, defined as structured activity created specifically to improve performance.

It became a staple of popular-science writing, which is what makes a test worth running. The authors ask directly whether the view is supported by empirical evidence, and answer it with a meta-analysis covering all major domains in which deliberate practice has been investigated.

The shares fall in a clear order. Deliberate practice explained 26 percent of the variance in performance for games, 21 percent for music, 18 percent for sports, 4 percent for education and less than 1 percent for professions.

Their conclusion is stated with care: deliberate practice is important, but not as important as has been argued. Nothing here says practice does not matter, and what it does say is that the rest of the variance belongs to something else.