Arnold Schwarzenegger was a thin teenager living in Austria when, in spite of his parents' doubts, he threw himself into weightlifting. Three times a week he went to the local gym, and each evening, he worked out for several hours at home. Today the champion bodybuilder-turned-actor became the most popular actor in the history of movies.

When Dondoleeza Rice was in secondary school, she was told that test scores showed she probably would not do well in university. But she didn't listen. She threw herself into her studies with such concentrated energy that she entered the University of Denver at age of 15 and graduated with high grades at 19. Today at 41 Rice is the youngest provost in Stanford University.

What brought these two very different people to the peak of their professions? In a recent TV interview, Schwarzenegger was asked to explain his success. He said, "Hard work, lots of discipline and positive thinking."

In any field it's important to have ambition and drive. But having worked as a psychologist with athletes, executives, artists and young people, I've learned that those who rise to the hardest heights in any field aren't necessarily the ones with the greatest natural talent. They are the diligent few who put in the hours. They work hard. And then they work harder.

Recent research by fellow psychologists proves the significance of focused hard work. In 1988, K. Anders Ericsson of Florida State University and colleagues in Germany compared the careers of two groups of young musicians. The ten members of the first group were identified as potential top-class international performers. Another ten were identified as merely "good." Ericsson also included ten violinists performing in orchestras of international reputation, such as Berlin Philharmonic. Both student groups kept diaries of their current practice schedules, and all the groups provided estimates of their earlier schedules.

Of the student musicians, Ericsson found, by age 20, the "good" group had practiced 7, 500 hours—an impressive total. But the potential world-class performers had practiced a staggering 10,000 hours—the equivalent of more than a year of hard work. Moreover, the top group's total practice time matched almost exactly that of the symphony performers at the same age.

Of course, there is a difference between hard work and drudgery. It's important to put in hours. But it's not just the hours that count. For hard work to really pay off, you need to work effectively.