As a teenager in Sweden, Anders Ericsson used to play chess against one of his classmates, a boy considerably worse at the game than Ericsson. Every time they'd play, Ericsson would trounce him.

Then one day, the classmate beat him.

Ericsson wanted to know: What exactly had the boy done to improve his performance so drastically?

Though Ericsson didn't realise it then, the question would come to define his life's work.

In the years that followed his defeat at the hands of his classmate, Ericsson found himself less interested in improving at chess and more interested in learning how people improve at anything.

Today, Ericsson is a professor of psychology at Florida State University, where he specialises, among many topics, in the science of peak performance. He is, in other words, an expert on experts.

According to Ericsson's research and logic, the sole reason you aren't a virtuoso violinist, or an Olympic athlete, or another kind of world-class performer, is that you haven't engaged in a process he calls "deliberate practice."

In general, according to Ericsson, deliberate practice involves stepping outside your comfort zone and trying activities beyond your current abilities. While repeating a skill you've already mastered might be satisfying, it's not enough to help you get better. Moreover, simply wanting to improve isn't enough — people also need well-defined goals and the help of a teacher who makes a plan for achieving them.

At first, the teacher gives feedback on your efforts; eventually, you can spot problems in your own performance and tweak it accordingly. Ericsson's research has led him to study expert spellers, elite athletes, and memory champions — and he attributes their diverse successes to deliberate practice.

Most notably, Ericsson's work on deliberate practice formed the basis for the "10,000-hour rule" featured in Malcolm Gladwell's book, "Outliers": Put in about 10,000 hours of practice, and you'll become an expert.

Unfortunately, Ericsson says Gladwell misinterpreted his research and that 10,000 hours of merely repeating the same activity over and over again is not sufficient to catapult someone to the top of their field.

Gladwell likely drew his conclusions from a paper that Ericsson and his colleagues published in 1993, which studied 40 violinists in Germany. Specifically, the researchers focused on what factors differentiated the best musicians from the good or the mediocre ones.

After asking all the violinists to give detailed records of how they spent their time, on music practice as well as on other activities, the researchers found that the top two groups of violinists spent significantly more hours practicing alone than the others did. The researchers also studied pianists and yielded similar conclusions.

On average — and Gladwell likely drew his conclusion from this — the best violinists had spent a total of 10,000 hours practicing their craft by 20 years old. Some, however, had practiced much more, or less, than that. (Gladwell's publicist didn't respond to a request for comment.)

Ericsson's findings from the past three decades suggest that deliberate practice is the key to achieving high levels of performance in any field.

In his new book, "Peak: Secrets From the New Science of Expertise," cowritten with the journalist Robert Pool, Ericsson translates the principles of deliberate practice from academic-speak into plain language.

When I spoke with Ericsson by phone in May, he told me that people who think practice can only get you so far aren't talking about the same kind of practice as he is.

As for whether genetic differences — say, in cognitive or physical ability — account for variations in achievement, Ericsson is skeptical.

Height and body size, he said, are the only genetically predetermined traits that can't be altered much through practice and have a meaningful impact on performance.

Even intelligence, Ericsson said, is not directly linked to expert performance. In "Peak," he cites a study by British researchers, which found that intelligence does indeed predict chess skill among children. But when those researchers looked only at kids who were elite chess players, a higher IQ was, in fact, linked to worse skills.

While a high IQ helps kids learn the game and acquire the basic skills required to play, once other kids catch up intelligence level probably doesn't matter, Ericsson explains. But deliberate practice does.

"I've been spending now 30 years trying to look for kind of limits that would actually constrain some individuals from being successful in some domain," Ericsson told me. "And I'm surprised that I've yet really to find such limits."

(Anders Ericsson (Anders Ericsson)

In the last few years, however, Ericsson's findings on deliberate practice have come under intense scrutiny from other psychologists.

Research published in May 2016 analysed the results of thousands of studies and found that while deliberate practice did indeed account for some of the differences between more and less skilled athletes, it couldn't account for all of them. The researchers can't say for sure what other factors matter, but they propose that genetically influenced physical traits such as how easily you build muscle mass, and even psychological traits like confidence, play a role.

Prior, in 2014, researchers analysed six studies of chess players and eight studies of musicians and found that deliberate practice was not the only explanation for high performance in either domain. Instead, other factors, like intelligence, might be at play there as well.

In a response to the 2016 paper, published in the same journal, Ericsson wrote that these conclusions are inaccurate, largely because they conflate total hours of accumulate practice with deliberate practice specifically.

Unless you're performing exercises that were assigned by a teacher to help you improve in a particular area, Ericsson believes you're not engaging in deliberate practice. Plenty of practice activities are completely ineffective and won't lead to improvement, he told me when we spoke again in June.

Reading over the scientific studies on deliberate practice, I couldn't help but wonder what these findings mean for professional writers.

Given the right practice conditions, could I really become the next Tom Wolfe or Michael Lewis?

Based on my understanding of Ericsson's research, it would take a lifetime of adherence to rigid practice criteria — but yes, it would theoretically be possible.

I posed a similar question to D. Zachary Hambrick, a professor of psychology at Michigan State University who coauthored both the 2014 and 2016 papers debunking Ericsson's findings.

Hambrick said he didn't know. To date, no research has explored the role of deliberate practice in writing expertise. But Hambrick also said he'd be surprised if writing ability was entirely dependent on deliberate practice. In other words, unless I started out with certain requisite abilities, a lifetime might not be enough for me to achieve Wolfe or Lewis levels.

Hambrick, however, kept reiterating that practice is important, if not essential, to the development of expertise in any field.

"I don't think there's any downside to believing in the power of practice," he said. "I do think there is a possible downside to sort of thinking that anybody can accomplish anything with no limits."

To put it frankly, believing that people can deliberately practice their way to peak performance might be a waste of time.

"People might start training in things and end up not improving much when they could have invested their resources and energies and time and training in other things which they might be more likely to excel at," Hambrick said.

Beyond the controversy over whether deliberate practice leads directly to expertise, perhaps the insight that struck me most in "Peak" was this: To become an expert, you may need to be willing to sacrifice short-term pleasure for potential satisfaction of success down the road. A key tenet of deliberate practice is that it's generally not enjoyable.

Instead, it's about doing things that don't come naturally or easily, which can be tough. "Practice really involves failing a lot until you eventually reach your goal," Ericsson told me.

He cited research on figure skaters (which appeared in this book) that found elite skaters spent more time than average ones practicing jumps and spins in routines they hadn't yet mastered. By contrast, average skaters spent more time going over routines they were already good at.

So what's the downside to becoming an expert? Perhaps it's that you need to devote yourself wholly to one area — that while one door flies wide open, others slowly creak to a close. Ericsson told me he doesn't know of anyone who's become a world-class expert in more than one skill.

That's why, he said, becoming an expert in anything and placing 100% focus on becoming the best in one domain "may not be basically the right thing here for even the majority of people."

That is to say, there's nothing inherently wrong with being average. In fact, working toward expertise in any area can be a grueling, lonely, and often ugly undertaking.

Ericsson, however, does practice what he preaches. He said he personally uses the principles of deliberate practice to become a better researcher. Every article he published, as a postdoctoral researcher and afterward, was the result of multiple drafts and feedback from the psychologists he was working with.

Ericsson cited one 1980 paper, which he cowrote with the late cognitive psychologist Bill Chase and published in the journal Science.

"Partly because I am Swedish," Ericsson said, "it took over 30 different drafts with comments on problems and issues by Bill before we had an article that Bill was willing add his name to."

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