You Can't Teach Speed: Falsifying the Deliberate Practice Model of Expertise (papers.ssrn.com)

Honestly, I could practice any instrument for 10,000 hours and still sound like I was touching up a chicken. Or try learning a language for 10,000 hours and sound like I was speaking it through a bucket of horse glue with the accent of a freshly minted coin.

There's a reason "The plural of anecdote is Gladwell"...