Difficult to control for variables if you were going to try and conduct a proper scientific study. The main proof we have is the results of people that have im

Difficult to control for variables if you were going to try and conduct a proper scientific study. The main proof we have is the results of people that have implemented the techniques described. But there are also other places where it's possible to take a closer look with a fairly large number of samples. Competitive multiplayer gaming is a good example, there are certainly competitors in that field who practice on a 'raw hours' basis and those that focus on individual skills in an ordered fashion. All that's needed is to go out and match that against their respective results.