If 10,000 hours of deliberate practice is necessary and sufficient for world-class performance, Epstein asks, why do some people reach the master level in chess after 3,000 hours while others require 23,000? The average number of hours needed for many pros may be about 10,000, but it varies widely.
The reason for the variation is genetic, Epstein says. In one study, researchers at Indiana University, University of Minnesota, Texas A&M University, Washington University, Pennington Biomedical Research Center, and Laval University in Quebec measured changes in VO2 max, an indicator of aerobic capacity, in people who followed a strict exercise regimen. About 5 percent of participants boosted their VO2 max levels by an astonishing 40 to 50 percent. Another 5 percent, however, saw almost no gain at all, and the rest fell in between.
The clincher was that, although a subject’s rate of improvement had little to do with how fit he or she was to start with, members of a family showed somewhat similar gains. The rate of improvement varied 2 1/2 times as much between families as within families, highlighting the importance of genes in determining how much improvement occurred. As one of the researchers told Epstein, “Unfortunately for the low responders in these studies, the predetermined (genetic) alphabet soup just may not spell ‘runner.’”
The research does not suggest that genes are dominant and training is irrelevant; instead, it says that the benefit from training is partially driven by genetics, so that a combination is required for top performance.
Orszag concludes by observing that “Epstein’s book is consistent with the literature about IQ,” and that while practice benefits virtually everyone, “some will see will bigger gains than others.”