If there is an idea inside the expert's head of how something works, programming or probability say, then there are graphics, usually animated graphics, that can present the core of the idea better than simply talking about it ever could. The problem is that it can be difficult to get right and this makes it expensive.
You can transfer the abstract understandings inside an experts head much more effectively using interactive simulations of the fundamental mechanisms than by using only words. Once transferred, the words that surround it help make the whole thing clear and asking a few questions that are difficult if you don't understand and easy if you do provides the diagnostic.
Randolph Hollingsworth on 14 Jul 14Ashton Anderson and Jure Leskovec (Stanford) Daniel Huttenlocher and Jon Kleinberg (Cornell) re Coursera students' activities/user rates: "engagement taxonomy" 5 different categories based on student interactions with the platform (http://www.openeducationeuropa.eu/en/news/mooc-study-creates-new-taxonomy-engagement): Bystanders are registered for the course, but their total activity is below a very low threshold. Collectors primarily download lectures, but don't participate much. Viewers watch lectures, handing in few if any assignments Solvers hand in assignments for a grade, viewing few if any lectures All-Rounders balance the watching of lectures with the handing in of assignments QUESTION: what about the way-finders - those who help create signposts for others to follow as learners navigate the course? or the web-makers - assisters/facilitators who help craft communities among learners?