K. Anders Ericsson, co-author of Peak, is the inspiration of the conventional wisdom that 10,000 hours of practice is the key to expertise. In the early 90s he published research suggesting that the average 20-year-old violin player in a prestigious music school had spent an accumulated 10,000 hours of time practicing. Malcolm Gladwell seized on this number a decade later in his book Outliers as a guideline for how many hours it takes to achieve expertise.
In Peak, Ericsson takes issue with Gladwell’s assertion, calling it a vast oversimplification. For one thing, pegging expertise to the level of skill of 20-year-old violin players seems arbitrary. He also picks apart other examples Gladwell uses.
Still, he’s clearly sympathetic with Gladwell’s larger assertion that deliberate practice, and a lot of it, is the key to skill mastery.