Like what? Numbers and studies? Khan Academy said that they have very promising results in which students perform significantly better on standardized tests. W

Like what? Numbers and studies? Khan Academy said that they have very promising results in which students perform significantly better on standardized tests. Without numbers and studies, this sounds like self-selection to me - people doing Khan Academy courses are surely more self-motivated than people attending colleges and universities, a substantial percentage of whom probably don't really enjoy being there. I think it's quite obvious that it's better to watch a recorded lecture than to see the teacher perform the same lecture years after year. Do you mean obvious from some study you've heard of, or obvious to you? Because that's not at all obvious to me personally - in fact, the opposite is true. I think I learn much better from in-person lecturers (providing the lecturer is good, which would have to be true in a video lecture too). I think there are two forces at play that make this true - first, the lecturer can gauge the response of the audience and tailor his presentation - timing, level of explanation etc. Second, the atmosphere makes me pay attention more - in much the same way as going to the cinema or to see a play in a theater is more engaging that watching the same thing on TV or YouTube. I know that basically everything I've said is all anecdote and presumption, but my presumption seem just as valid (to me, more valid :-P) than yours in the absence of hard data. On your point that we should [give] the teachers and students better tools based on cognitive science that we discovered a long time ago, I wholeheartedly agree, but it needs to be done based on scientific conclusions, not anecdata (yours or mine).