I believe the answer is: is significantly better than others at performing a certain task
Developmentalist believe that a strong skill set is aquired through repeating a certain action over and over again to the point where that person could perform a certain task in significantly better quality compared to other people.
According to these developmentalists, in order to be a world class expert in a certain thing, you need to at least put 10,000 hours of effort into that task.
