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Relationship Between Practice and Performance in Sports: A Meta-Analysis (2016) [pdf] (case.edu)
55 points by luu 6 months ago | hide | past | web | favorite | 26 comments

A good analogy is that expertise is like an area of a rectangle: Both innate factors and practice contribute to it.

Which contributes more? It depends on the variance on each dimension. We see from Fig 3 (page 9) in the paper that the unexplained variance is highest for elite athletes at 99%. Why? Because almost all of them practice as much as it is useful to do so. In other words, the heights of their rectangles are about the same, almost all of their area differences depend on other factors [1]. For other groups, the variation in practice time explains more about their performance differences.

[1] These may include innate talent, techniques, psychological factors, etc. With more than two dimensions, we may need to change the analogy which I do not have the time to get into now. Also, as with most analogies, it is not perfect. Practice time is likely not independent of talent.

Money quote on page 345: "In the second study, Mosing, Madison, Pedersen, Kuja-Halkola, and Ullén (2014) had over 10,000 twins representing an extremely wide range of music skill estimate deliberate practice and perform tests of music aptitude. Mosing et al. (2014) found that there were genetic effects on both music practice and music aptitude. More important, there was no evidence for a causal influence of music practice on music aptitude. Identical twins differing massively in amount of deliberate practice did not differ significantly in music aptitude."

Apologies for being contrarian, but let me flip things around: Perhaps people who are able to benefit from practice enjoy it and tend to do more of it.

I get excited learning about the latest C++17 features and used to love reading stock exchange specifications, which most people would find about as exciting as a root canal. I find it rewarding because I can apply what I learned and feel a sense of satisfaction. Conversely, I've always sucked at golf and could barely stomach the half-dozen lessons I tried, even though I consider myself a diligent person and spent years practicing many other things. I never improved my swing and the entire experience was nothing but frustration. If you have a rough time at a beginner or intermediate level, it's hard to gin up the desire for continued practice beating your head to a wall.

The premise of this paper is naturally enticing. If you had only tried a bit harder practicing lay ups in gym class, you could be just as good as Michael Jordan (ok more like you could get a bit closer, since they claim practice explains ~20% of results). I don't really buy it.

> If you had only tried a bit harder practicing lay ups in gym class, you could be just as good as Michael Jordan

I don't think it's that - MJ obviously had a lot of things going for him other than his practice ethic (for one, not too many people are 6'6"). Most people just want to be slightly better than their peers - they want to be the best player on their rec league, and understand they're not going to the NBA.

That holds some water, since as the article notes deliberate practice has more effect at the lower levels of competition.

Or to bring it back to your golf analogy - you were never going to be even a low-level professional golfer, but with enough deliberate practice you could've probably held your own against your co-workers at a company event. That's the goal of most people engaging in deliberate practice, outside of very select environments.

Obviously that doesn't counteract your sheer anguish of practice, though, and you're right that it's quite difficult to practice if you don't have an aptitude for the task.

In the same vein, I think the term "deliberate practice" may produce misleading results. If you love music and you're very good at it, you may not count a jam session or some idle noodling around on a guitar to be "deliberate practice" but they would still contribute to your skills.

Likewise I suspect if you asked a bunch of mid-level gamers how much time they spent "deliberately practicing" to improve their skills, the answer would be low compared to their total playtime, and that their skill levels would correlate much more strongly with total playtime than with deliberate practice.

Neither of your examples qualify as deliberate practice. People can plateau at one skill level for decades and make sudden jumps in ability by deliberately focusing on one specific skill. Expertise is at least in part, the combination of excellence in multiple related skills.

> An expert breaks down the skills that are required to be expert and focuses on improving those skill chunks during practice or day-to-day activities, often paired with immediate coaching feedback. Another important feature of deliberate practice lies in continually practicing a skill at more challenging levels with the intention of mastering it.

K. Anders Ericsson, Ralf Th. Krampe, and Clemens Tesch-Romer. The Role of Deliberate Practice in the Acquisition of Expert Performance. Psychological Review 1993, Vol. 100. No. 3, 363-406 [

That's kind of the point. "Deliberate practice" definitely helps to hone particular skills which fill holes in your overall competence. When you're performing at ultra high levels, you probably already have optimal performance in most areas, and all you have left to practice are particular skills.

Also, how you measure "sports performance" and what a percentage point means at different levels seems crucial to the whole thing. Maybe deliberate practice only accounts for 1% of performance... but an athlete who's 99% perfect is twice as good as an athlete who's 98% perfect.

Bear in mind that the musical aptitude being measured has little to do with how skilled they are as a musician. They are measuring things like ability to differentiate tones separated by 1/2 to 1/30 of a semitone, rather than how much you would want to listen to them play.

Anders Ericsson has replied to this meta-analysis [1], which in turn got a reply from McNamara et al [2].

In Ericsson's opinion/definition [1], deliberate practice is "individualized practice with training tasks (selected by a supervising teacher) with a clear performance goal and immediate informative feedback was associated with marked improvement"; and he argues "In contrast, Macnamara, Moreau, and Hambrick’s (2016, this issue) main meta-analysis examines the use of the term deliberate practice to refer to a much broader and less defined concept including virtually any type of sport-specific activity, such as group activities, watching games on television, and even play and competitions. Summing up every hour of any type of practice during an individual’s career implies that the impact of all types of practice activity on performance is equal—an assumption that I show is inconsistent with the evidence."

McNamara et al reply saying that evidence only accounts for a relatively small fraction of expert performance [2]: "we found that deliberate practice accounted for a sizeable amount of variance in sports performance (18%), but it left a much larger amount unexplained. Ericsson’s (2016, this issue) evaluation of our research is undercut by contradictions, omissions, and errors." They conclude that "The available evidence indicates that deliberate practice, though undeniably important, does not largely account for individual differences in expertise. Building on Ericsson’s pioneering work, the task now is to develop theories of expertise that include multiple factors."

[1] Summing up hours of any type of practice versus identifying optimal practice activities: Commentary on Macnamara, Moreau, & Hambrick (2016) http://journals.sagepub.com/doi/abs/10.1177/1745691616635600

[2] How Important Is Deliberate Practice? Reply to Ericsson (2016) http://journals.sagepub.com/doi/abs/10.1177/1745691616635614

Seems like I need an account to either purchase or rent both articles?


This was a pretty interesting read, and something I've often wondered about. I remember when LeBron James joined the NBA. It just baffled me at the time how some 18 year old high schooler could be so much better than professional players, players who've played day in and day out for _years_. Hours of deliberate practice didn't seem to be an adequate explanation.

LeBron James' greatest gift is his brain that has a phenomenal photographic memory.

> In the jovial postgame locker room, it's pointed out to James by a reporter that almost exactly five years earlier, he'd won a game with a jumper at Oracle Arena at the buzzer from virtually the same exact spot at the same basket.

"Not really," James says in response. "That one was probably about six feet closer to the baseline and inside the 3-point arc. It was over Ronny Turiaf, I stepped back on him but I crossed him over first and got him on his heels. I'm sure of it. It was down the sideline a few feet. It was a side out-of-bounds play; this one we brought up."


He may have a photographic memory, but I don't think that anecdote supports the claim. I do not have a photographic memory, but I clearly remember select events that are very meaningful. Game-winning shots at the buzzer would be that sort of thing. There aren't very many of them, and they would be easily remembered in detail.

I am not going to quite the entire article, and it makes a strong case that his mind is an incredible asset.

One more excerpt. It is not just game winning plays...

> So what does it mean? What it seems to suggest -- at least the part of it that James will discuss -- is that if you give up the baseline to James on a drive in November 2011 and he's playing against you in March 2013, the Heat small forward will remember it. It means that if you tried to change your pick-and-roll coverage in the middle of the fourth quarter of the 2008 playoffs, he'll be ready for you to try it again in 2014, even if you're coaching a different team. It also means that if you had a good game the last time you played against Milwaukee because James got you a few good looks in the first quarter, the next time you play the Bucks you can count on James looking for you early in the game. Because, you know, the memory never forgets.

"I can usually remember plays in situations a couple of years back -- quite a few years back sometimes," James says. "I'm able to calibrate them throughout a game to the situation I'm in, to know who has it going on our team, what position to put him in.


his greatest gift is that he's 6'8


he has a collection of many traits that make him a unique talent

of all those traits, the one with the largest standard deviation from the norm is almost certainly his height

No, largest standard deviation doesn't make it his greatest gift unless its weighted contribution to his overall skill (some combination of importance and rarity) was the greatest. There are certainly positive traits even rarer than height that have little or no bearing on skill, not to mention that optimum is not the same as maximum for some traits, probably including height.


are you arguing that of all the traits under consideration, height isn't one of ones of primary importance for his success on the basketball court?

ie, if we keep all his various traits constant, and one by one, move each of them back a standard deviation

is there a trait that would change his effectiveness more than moving his height back a standard deviation?

No, undoubtedly optimum height is a major factor in his and other basketball players' success, and I don't know of any other factor that obviously dominates it.

His mental talents may be even rarer however. I don't know how we could know.

Did you read the article? Please do so before rebutting the assertion.



its not totally clear what percentile memory LeBron has

its not totally clear if there actually is such a thing as photographic memory

" There are so many unlikely circumstances surrounding the Elizabeth case—the marriage between subject and scientist, the lack of further testing, the inability to find anyone else with her abilities—that some psychologists have concluded that there's something fishy about Stromeyer's findings. He denies it. "We don't have any doubt about our data," he told me recently. Still, his one-woman study, he says, "is not strong evidence for other people having photographic memory."

That's not to say there aren't people with extraordinarily good memories—there are. They just can't take mental snapshots and recall them with perfect fidelity. Kim Peek *, the 53-year-old savant who was the basis for Dustin Hoffman's character in Rain Man, is said to have memorized every page of the 9,000-plus books he has read at 8 to 12 seconds per page (each eye reads its own page independently), though that claim has never been rigorously tested. Another savant, Stephen Wiltshire, has been called the "human camera" for his ability to create sketches of a scene after looking at it for just a few seconds. But even he doesn't have a truly photographic memory. His mind doesn't work like a Xerox. He takes liberties.

Photographic memory is often confused with another bizarre—but real—perceptual phenomenon called eidetic memory, which occurs in between 2 and 15 percent of children and very rarely in adults. An eidetic image is essentially a vivid afterimage that lingers in the mind's eye for up to a few minutes before fading away. Children with eidetic memory never have anything close to perfect recall, and they typically aren't able to visualize anything as detailed as a body of text. "



lets ballpark it and say his memory is in the top 1%

being 6'8 puts him in roughly the top 0.135% of adult males

I stand by my rebuttal

6'8" makes him slightly above average in the NBA. Comparing his height to the world population at large does not make sense if we are comparing him against other professional basketball players, past and present.


That's the point though, everyone in the NBA is extremely selected for height, and since we see him in the context of other NBA players we lose sight of how extreme this selection is and focused on traits that aren't particularly selected for, even if those traits are unique once you get past the previous selection

After further thought, it is clearer from the comments of others who know more that it is his height and size and speed that give him an advantage. Therefore, he is not average in the NBA but an outlier.

I only read the abstract, but it seems to support my anecdotal observations that natural talent is a big factor in most elite performers, regardless of field.


The 10,000 hr practice myth has long been busted by series of studies and this meta study is another one in the series focusing on sport. It turns out that among non-elites, only 18% of performance difference can be attributed to deliberate practice! More surprisingly, there are significant non-elites who spend same or more hours in deliberate practice which means that simply looking at this number doesn't allow you to accurately distinguish between elites and non-elites. Finally, starting at childhood has minimal advantage in performance difference.

This is another big stab in the nature vs nurture debate. There are many studies (also cited in this paper) which has indicated that deliberate practice only account for 30% of performance difference in activities like chess requiring purely cognitive abilities. So for physical activities, it makes even less difference! The paper has extensive references at the end which indicates that rest of the majority of differences comes from genetics and possibly psychological factors such as confidence, sensitivity to rewards, ability to focus, performance anxiety and so on.

So currently, it looks to me nurture contributes 1/3 and potentially (this is not in paper) nature another 1/3 and psychological factors another 1/3.

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