This is introduced in the second chapter and refers to the minimum number of hours necessary to become an expert in any given area. It comes from research conducted by K. Anders Ericsson and others at the Berlin Academy of Music in the 1990s. They studied violinists to distinguish the elite players from the very good and the merely good. They found no natural prodigies who just had extreme talent without putting in the hard work. Instead, the single factor that distinguished players from one another was the amount of practice time invested. Those at the elite level practiced a total of 10,000 hours or more. 

Researchers in sociology refer to “accumulative advantage” as advantages that build up over time. Gladwell uses this term in Chapter 1 while discussing the selection process for programs like the youth hockey league in Canada. Usually, players are chosen to participate based on a slight advantage conferred by being older: The child is just further along developmentally than younger players at that point. Once in the program, special training and lots of practice improve these players’ skills, increasing the gap between them and other players. This gives them greater opportunities, which lead to more advantages, and so on.