Other factors are much easier to control. For instance, scientists have shown that performance itself — that is, testing oneself, from memory — is a particularly strong form of practice. One of the studies that the new review paper includes found that chess masters with similar abilities varied widely in the amount of hours they reported practicing, from 3,000 to more than 25,000.
“We may find when looking more closely that playing in tournaments, under pressure, is an important factor,” Dr. Hambrick said.The content of isolated practice is another. In dozens of experiments, scientists have shown that mixing related skills in a single practice session — new material and old, scales and improvisation, crawl and backstroke — seems to sharpen each skill more quickly than if practiced repeatedly on its own.
Varying the place and timing of practice can help as well, for certain skills, studies suggest. [cf Piano Videos: slow, fast, down an octave, up an octave]]
“The question is: What is the optimal kind of practice in the area you wish to achieve expertise?” Dr. Ericsson said. “These are things we are now beginning to study, in areas like medical training.
”Practice time is critical indeed, and its contribution to accumulated expertise is likely to vary from one field to the next as the new paper found, experts said. Personality is an enormous variable, too, although partly genetic. “Things like grit, motivation, and inspiration — that ability to imagine achieving this high level, to fantasize about it,” Dr. Kaufman said. “These are things we don’t know much about yet, and need to study more directly.”But in the end, the most important factor over which people have control — whether juggling, jogging or memorizing a script — may be not how much they practice, but how effectively they use that time.