Malcolm Gladwell's Outliers: The Story of Success made famous the "10,000-hour rule" which says that to become an expert at something, you need not only talent and opportunity but also about 10,000 hours of practice at it.

Very often this holds true for entrepreneurs. Jon Auerbach, general partner at Charles River Ventures, recently penned a TechCrunch story in which he points out that "some of the world's best entrepreneurs were the kids running lemonade stands, building LEGO robots, and hacking computers," essentially spending years practicing business. Just look at Mark Zuckerberg, Larry Page, and Bill Gates--all of them were heads down in technology long before leaving high school.

But recent research claims practice doesn't always make perfect.

"The evidence is quite clear," writes Michigan State University researcher Zach Hambrick, "that some people do reach an elite level of performance without copious practice, while other people fail to do so despite copious practice."

Hambrick and his colleagues made this determination by taking the average correlation between practice and performance across six studies of chess and eight studies of music. It turns out practice was responsible for only about one-third of the differences in performance in each domain. The researchers point to other factors that could be more influential when it comes to achieving greatness, things like intelligence, natural ability, and even the age at which a person starts learning to do something.

Intelligence

In fact, in an op-ed piece for The New York Times in 2011 Hambrick and co-author Elizabeth Meinz showed that incredible intelligence translates into "enormous real-world advantage."

As evidence, they pointed to a study directed by Vanderbilt University researchers that tracked the educational and occupational achievements of more than 2,000 people who by the age of 13 had scored in the top 1 percent of the SAT, something one psychologist has described as a "thinly disguised" measure of IQ.

"Compared with the participants who were 'only' in the 99.1 percentile for intellectual ability at age 12, those who were in the 99.9 percentile--the profoundly gifted--were between three and five times more likely to go on to earn a doctorate, secure a patent, publish an article in a scientific journal, or publish a literary work," they wrote.

Hambrick has also studied "working memory capacity," something that's closely related to intelligence, and found that a pianist with a higher working memory capacity is more likely to perform better when compared with someone who had practiced the same amount of time.

Natural Ability and Genetics

Did you know there were more than 20 outstanding musicians in Bach's family? There could be a very good reason for that. Hambrick's MSU paper cites studies of twins that found genetics does affect aptitude and exceptional talent. For example, in 2009 Dutch researchers released findings from a study in which they asked nearly 2,000 twin pairs to rate their competence in things like chess and music. The study found that genes are responsible for 50 percent to 92 percent of the differences across people in skill.

Starting Age

Just like young children can more easily learn a second language than adults, there may be a critical period for learning other things. Mozart, after all, was already skilled on a keyboard and violin by the time he started composing at age five.

Several studies support the idea that people who start doing something early have an edge over those who wait, including one that showed that chess players who learn the game young tend to have an advantage as adults, regardless of how much practicing they have done.

A Story of 10,000 Hours

Some people still swear by practice.

Yorgen Edholm is one of them. The Silicon Valley CEO spent 10,000 hours playing the violin to finally become world class, eventually performing in Carnegie Hall. He practiced six hours a day, seven days a week for five years while studying under Ivan Galamian, a famous violin teacher in New York who taught the likes of Itzhak Perlman and other big names.

He credits practice for his violin expertise, but I think that's too pat an explanation.

Edholm is also whip smart, which fits with Hambrick's findings that intelligence factors into success. In fact, he was interested in computers before anybody thought of them as more than souped-up calculators. As a result, in the last quarter century he has made a killing running software companies. Before his current company, Accellion, he co-founded Brio Technology, a business intelligence software company that went public and was reaching $150 million in revenues before it was swept up in a string of acquisitions that began a decade ago, eventually landing Brio's intellectual property into Oracle's fold.

As for starting age and genetics, Edholm started playing violin at age nine and has a brother who also played professionally. He says his youngest son plays and appears to be quite gifted.

Hambrick says even though he doesn't believe anyone can become anything and many factors influence whether or not someone will achieve great things, it's important not to discount effort and persistence.

"The effects of practice on performance can be far reaching," he says.

But don't forget: When it comes to business success, smarts, a top-notch team, timing, connections, and luck matter.