What is the difference between Joe Six-Pack, Joe the Plumber and Joe Biden? One is vice president; the other two are not. Why? The answer depends on a host of interactive variables that must be factored into any equation of success: genes, parents, siblings, peers, mentors, practice, drive, culture, timing, legacy and luck. The rub for the scientist is determining the percentage of influence of each variable and its interactions, which requires sophisticated statistical models.

Journalists unconstrained by research protocols churn out self-help books that focus on select variables that interest them. Few do so better than Malcolm Gladwell, and in his new book Outliers: The Story of Success (Little, Brown, 2008), the New Yorker writer claims that successful people are not "self-made" but instead "are invariably the beneficiaries of hidden advantages and extraordinary opportunities and cultural legacies that allow them to learn and work hard and make sense of the world in ways others cannot."

Bill Gates, for example, may be smart, but Gladwell prefers to emphasize the fact that Gates's wealthy parents sent him to a private school that had a computer club with a teletype time-sharing terminal with a direct link to a mainframe computer in Seattle, and in 1968 this was very unusual. His good fortune to be born in the mid-1950s also meant that Gates came of age when the computer industry was poised to have someone of his experience start a software company.

Similarly, Gladwell says, Mozart's father was a composer who mentored the young Wolfgang into greatness from age six until his early 20s, when his compositions morphed from pleasantly melodious into masterful. The Beatles' lucky break came in Hamburg, Germany, where they were able to log in more than 1,200 live performances and thereby meet the well-known 10,000-hour rule for perfecting a profession. Elite hockey players are disproportionately born in January, February and March (40 percent compared with the expected birthrate, which in most studies hovers around 25 percent) because the birthday cutoff date when they were youngsters first hitting the ice was January 1, and players born early in the year were slightly bigger, stronger and faster, giving them an advantage. Asian student wunderkinds are the product of "the tradition of wet-rice agriculture" that must be practiced year-round and that requires "the highest emphasis on effort and hard work," and that's why they study all summer while American students go to the mall.

Such prodigies and geniuses, Gladwell says, "are products of history and community, of opportunity and legacy. Their success is not exceptional or mysterious. It is grounded in a web of advantages and inheritances, some deserved, some not, some earned, some just plain lucky but all critical to making them who they are."

Well, yes and no. As Frank J. Sulloway, author of the comprehensive study of success Born to Rebel (Pantheon, 1996), told me: "Creative people are not just sitting around waiting for opportunities to come to them. They create their own opportunities. Charles Darwin was already planning a voyage of discovery to the Canary Islands, for example, when the position on the Beagle opened up. If the Beatles hadn't gone to Hamburg, they would have gotten their 10,000 hours somewhere else. What distinguishes Gates is that he has a really interesting creative mind, and he would have had that mind even without a computer terminal at his private school and hence would likely have found alternative ways to access programming tools." And of course, Leopold Mozart's son was a child prodigy and musical genius, not merely the beneficiary of cultural legacy.

Even the 10,000-hour rule isn't just about skill mastery. According to Dean Keith Simonton, author of Origins of Genius (Oxford University Press, 1999), success includes a Darwinian process of variation and selection. Creative geniuses generate a massive variety of ideas from which they select only those most likely to survive and reproduce. The best predictor of winning a Nobel Prize in science, for example, is the rate of journal citation. As Simonton notes, "empirical studies have repeatedly shown that the single most powerful predictor of eminence within any creative domain is the sheer number of influential products an individual has given the world."

Genius is as genius does.

Editor's Note: This story was originally published with the title "Inside the Outliers"