10,000 Hours or 10 Years

What does it mean to be an expert on something? What does it take? A lot of research has been done about this, and, unfortunately, I don't have links to all of it here. One pattern that I have seen emerging in the research, though, is that there is some kind of threshold of experience that seems to be strongly correlated with mastery.

I have heard two different estimates for this threshold. I have heard that one must spend 10,000 hours on an activity to attain mastery. For example, a study that correlated different factors with athletic success found that number of hours spent practicing was a better indicator of success in a sport than such aspects as whether one's parent(s) played the sport, natural physical ability, or intelligence.

Another estimate that I have heard is that it takes 10 years of active participation to become an expert. Of course, there are lots of things people do for 10 years without mastering. But, doing something diligently, like, say, as a job, for 10 years does seem like enough to achieve mastery. If I programmed in Perl for 10 years, I think I would be an expert on it. If I worked at playing the saxophone for the next 10 years, I might not be the best player in the world, but I would likely be considered an expert by almost everyone who assessed me.

In fact, these two estimates aren't too far apart... if you do 10,000 hours of something over a 10 year period, it amounts to 1,000 hours per year, or about 2.74 hours / day. That seems pretty believable. So, if you do something for 3 hours per day, with a little break in the middle, you'll be an expert in roughly 10 years.