The 10,000-hour rule popularized by Malcolm Gladwell roughly says if you practice one skill for 10,000 hours, you'll have a good chance at becoming an expert at it.

As the Guardian reports, new research indicates the 10,000-hour rule alone doesn't account for mastery in a given skill, like playing the violin.

Aside from deliberate practice, differences in each person account for skill level, according to psychologist Brooke Macnamara, who co-authored the study.

Visit Business Insider's homepage for more stories.

We've all heard that age-old saying: Practice makes perfect.

According to new research, however, that's not necessarily the case.

As the Guardian reports, the adage was given a scientific basis when journalist and author Malcolm Gladwell wrote about the 10,000-hour rule in his 2008 bestseller, "Outliers." The rule is simple: mastery comes after someone practices one skill — like playing the violin — for 10,000 hours.

As Gladwell writes in "Outliers," the key to mastering a skill is practice, and "ten thousand hours is the magic number of greatness." His book chronicles how greats like Bill Gates and the Beatles toiled away for thousands of hours before becoming experts in their fields.

To prove his point, Gladwell cited a 1993 study which indicated that increased practice led to playing the violin like a virtuoso. Anders Ericsson, the psychologist behind the rule, became something of a celebrity in his field after Gladwell's smash hit, and the related idea of "deliberate practice" — or pushing your skills over long hours — became a popular subject with the LinkedIn-y world of thought leadership.

But according to a new study published in Royal Society: Open Science that attempted to replicate the findings of the original, practice alone doesn't account for mastery. In the study, deliberate practice only accounted for a quarter percentage of the skills difference, which doesn't account for what makes someone an expert.

Brooke Macnamara, a psychologist at Case Western Reserve University, and researcher Megha Maitra interviewed three groups of 13 violinists, each rated as less accomplished, good, and best. The violinists were told to keep a diary to log practice hours, and those hours were then tallied. While the less accomplished violinists had logged an estimated 6,000 hours by age 20, the good and best had both logged around 11,000 hours.

That is to say: The good and best violinists saw no huge difference, as opposed to the not so good violinists, who didn't practice as much. The implication: practice didn't account for all the differences in performance.

"I think a lot of people like the idea that with hard work and determination anyone can become an expert at anything," Macnamara told Business Insider.

"It's very 'American Dream,'" she added. "However, it is an oversimplification. Of course you will almost undoubtedly improve with practice, but more practice does not necessarily mean you'll be better than someone else with less practice."

Macnamara said that a lot more goes into mastering a skill than practice. "Even the greatest in the world are not perfect, but to become great, it is likely a number of factors, depending on the task," she said. "A combination of genetic factors, environmental factors, and their interactions, make us who we are and what we accomplish. This includes what we think of as talent, motivation, practice, and opportunity."

One of the original study's coauthors, Ralf Krampe, a psychologist at the Catholic University of Leuven, told the Guardian that the new findings about deliberate practice don't disprove his own. The 1993 study he coauthored never concluded that the number of hours spent on a skill guarantees mastery. "But I still consider deliberate practice to be by far the most important factor," he said.