Think of the "ticker tape" at the bottom of ESPN or CNN, people read this information and it stays with them longer than the hosts that they tune out. The "facts" at the bottom people read and hear it in their heads which is held onto possibly longer than someone elses voice on a video screen. That would be an interesting study.

You could also look into Khan's black screen approach where he only uses that backdrop. He is humorous and captivating like in his Ted.com talk, so I extract more by listening to his voice and seeing the examples he is drawing up. Your videos with students (assumed) add another element of stimulus that might take away from their efficency.

This was interesting. I think Khan videos in a vaccume would leave room for error to occur. The nice thing is that in doing the problems on their website it would allow you to see where your short sightedness came into play and would be a corrected pattern especially as the student continued on in the process of learning a new topic.

I am sure that in the second set of videos which introduce common misconceptions, it would be described as clear, if the added video text would be added accross the top of the video screen with "common misconceptions" then the correct presentation/facts could be presented.

interestesting