Luis Von Ahn is a computer science professor and the CEO of Duolingo, one of the more efficient ways to pick up a new language. His section has two key ideas : a) The value of "I don't understand" Luis had a Phd advisor who kept insisting that he did not understand what Luis was trying to say when he was developing the CAPTCHA system. Eventually, it was revealed that his advisor was simply employing a tactic to get Luis to think deeper about the problem he was facing with. Blogger Scott Young is an advocate for a learning approach known as the Feynman Technique which basically forces you to explain concepts that you learn in plain English. If you find that your ideas are expressed in jargon, it is possible that you really do not understand the material yourself. The kay to mastery to is to be be able ......