Active vs passive learning: There is research that people tend not to learn much by re-reading a book/chapter etc. On the other hand, solving problems tends to be useful for learning. This made me wonder, is there research into passive learning by going through various different sources? Instead of re-reading the chapter, one goes to look for different sources of information, where the same thing is are explained slightly differently. Intuitively, any form of re-reading should be less effective. Any research on this?