It takes many thousands of hours of hard work to get to the top—yet time alone is not enough if you lack the other attributes necessary in your discipline, according to a study published online in July in Psychological Science.

In 1993 psychologist K. Anders Ericsson and his colleagues argued that success was not a matter of talent but rather what they termed deliberate practice, an idea that Malcolm Gladwell popularized as the “10,000-hour rule” in his book Outliers. Still, the role of deliberate practice—activities designed with the goal of improving performance—remained controversial. To try to sort things out, psychologist Brooke N. Macnamara of Princeton University and her colleagues reviewed 157 experimental results connecting total time spent practicing to ability in sports, music, education and other areas. On average, practice time accounted for just 12 percent of the variation in performance. Practice had the biggest effect on games such as chess—it explained 26 percent of the differences in performance—but it had almost nothing to do with ability in academic classes or professions, such as computer programming. The more rigorously each study judged its subjects' ability—such as by having experts evaluate their performance—the less total practice time mattered.

Although the authors wrote that they could not yet be sure what other factors contribute to high-level ability besides practice, they thought natural talent, general intelligence and working memory most likely play important roles. And success, of course, does not always scale with performance—getting to the top also depends on personality, determination and simply being in the right place at the right time.