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 26 Jul 10Cornell University's website on academic integrity, including a nice section on student rights for their own content created for class work.
