Let's take chess: 10k hours of deliberate practice in your teen years will make you a master level player (and possibly near GM caliber if you think Polgar experiment was not a fluke).
There are no known instances of someone starting to play chess after age of 30 and getting near GM. Conversely, I've known people who retired in their 40s and dedicated themselves to chess and could not achieve more than a 50-100 point gain.
I would love to be proven wrong, but I suspect the story is the same with piano, violin and programming.
Your 10k hours at age 40 will not get you near anywhere the same return than 10k hours at age 10-16.
I would love to see some references to people achieving mastery in some field past the age of 40 starting from scratch.
http://en.wikipedia.org/wiki/Neuroplasticity is supposed to show that it is possible to get good at a later age, but I am very skeptical.
When you're young, you have more time, less commitments and obligations (family, job, etc.), and generally less fears (if I screw this up, it's fine because I'm 17). As you grow older, these things get added on and it becomes difficult to motivate yourself to actually spend the 10k hours.
If you're talking about something like skateboarding, I think you're right that younger people will learn it better and faster than old people, because it's inherently physical. If you're talking about a mental task, I think it's a matter of whether or not you will sit down and do the work.
[1] http://en.wikipedia.org/wiki/Fluid_and_crystallized_intellig... : "This decline may be related to local atrophy of the brain in the right cerebellum. Other researchers have suggested that a lack of practice, along with age-related changes in the brain may contribute to the decline."
I think this discussion [1] from other day is relevant.
Basically, getting old and taking on more responsibilities doesn't necessarily have to mean becoming less productive as long as you can adapt your strategy and habits.
I got serious about playing the game of go relatively late in life for a go player--I was 23 years old at the time. In 2 years of hard study (1~2h/day, and a bit more on weekends) I rose from essentially a complete beginner to dan level play. Since then, life has pulled me away from playing go as actively, but the work I do at this point does let me maintain my level of play.
I think it's fair to say that you get MORE out of your effort at a younger age, but at the same time, I think that if you're serious about learning and honest about the way you learn, you can absolutely get a LOT out of those hours--and that ultimately, you can get the same utility as you would have, by tailoring your studies to the way you learn more effectively.
I think part of the trouble is that that the definition of "mastery" is so fluid. In chess, is "grandmaster" really the bar you want to set? Why not just "master" or even "expert?"
In another area, some percentage of medical doctors receive their degrees after age 40. Is that achievement + licensure sufficient to call it "mastery?"
Lesson: Master a skill that you can franchise and protect.
http://allaboutwork.org/2012/11/21/malcolm-gladwells-10000-h...
Are you also offended by astronomers getting the mass of a star, or geologists measuring the amount of oil in a well wrong? They would be delighted to get the order of magnitude right.
One issue I have with the 10,000 hour rule in general is this: there are approximately 2,088 hours in a work-year not counting overtime. To achieve mastery in your profession would then take less than 5 years. Most professions don't consider someone an expert 5 years into their careers. So does that mean a) you're not really improving that much in those 5 years b) there are more conditions to the 10,000 hour rule c) the 10,000 hour rule is flawed or d) the evaluation of one's expertise is flawed?
Another issue I have with the 10,000 hour rule is the idea of competence and sufficient experience. At what level of experience (in this case, hours) are you competent enough to achieve your goal? If programming, at what level can you create something that solves a given problem. If business, at what level can you successfully run a startup, etc.
So if the target changes to "enough experience to achieve a specific goal" then I'd argue one has much more time available to him/her than what this math suggests.
I think this is where you get into mastery vs. experience. 10k hours of a task does not make you an expert unless you've spent those 10k hours deliberately attempting to gain expertise.
This is also where you get into good practice vs. bad practice. i.e., the average golf enthusiast "practices" by going to the driving range, because it's easy and fun and he's probably already decent at using a driver. Someone who wants to become a golf professional practices by hitting a hundred balls out of a sand trap or driving into the wind or any number of other difficult techniques they're not good at yet.
It's not so much the passage of time (10k hours) that matters, as it is how you spend those hours.
To your second point, "mastery" is sort of a vague term. I like your idea of "enough to achieve a certain goal". That's probably better from a mental health perspective too (experts in many fields are pretty crazy because they've devoted themselves exclusively to this one narrow area for years and years).
In other words, I can see the benefit of taking all aspects of my job seriously, even meetings, because they are the backbone of influencing others on your ideas/design as well as fully understanding all aspects of a project.
The 10k hours claim is utter nonsense on the most basic level. How exactly is "one skill" defined? There is no such thing as "one skill." Every skill, field, whatever is a highly complex amalgam of countless sub-skills. How do you determine the extent of the "one skill" that you're devoting to?
Let's say you want to master 18th century history, defined as achieving a skill/knowledge level of X in that field. Does this take 10k hours? Why not 20k? Why not 5k? How can anyone assume that just because 18th century history has been defined as a particular "skill" that reaching some skill level X will take 10k hours?
If you instead choose to master early 18th century history from 1700-1730 so that you know the years 1700-1730 just as well as the 1700-1800 specialist, does it now take you only 3K hours instead of 10K?
Does any of this math make any sense at all?
Since the concept of "one skill" is utterly absurd nonsense that is completely undefinable, and the concept of "mastery" is equally undefinable and meaningless, this whole 10k meme is nothing but marketing bullshit of the kind that Gladwell mass produces in his shitty vapid books.
Gladwell is a hack of the highest order. He has never said anything meaningful. This 10k hour meme is just another marketing turd he shit out to mystify and flatter the dumb middle classes who read poppy trash like Gladwell so they can call themselves literate.
Fucking disgrace that people take this seriously
Second and more important, we need to remember that none of us learn in a vacuum. How much faster did you pick up programming because you already understood the concept of grammar, and had taken a logic or debate class in high school? Even in wildly different fields of study, there are dots we connect, analogies that we construct, and skills that we posses and bring to the table. It is reasonable to assume that we gain some efficiency in learning new skills, by virtue of the masteries we already possess.
Life creeps up, and seeps into the cracks so tenuously occupied by free time. Mastering but a single skill is impressive.
On a serious thought, if old people live longer, we have longer access to their knowledge and expertise. When old people die, we lost some their expertise forever. So if we cure cancer and other diseases, that would be money well spent.
