In a final example, a number of times Kathy Perkins and I have presented some non-obvious fact in a lecture along with an illustration, and then quizzed the students 15 minutes later on the fact. About 10 percent usually remember it by then.

Half of them failed to grasp it? You say it like it’s a bad thing, instead of five times more effective than a lecture.

I’m more a glass-half-full on this one. Only half didn’t get it? Cute. Try a gold standard double-blind controlled trial against a lecture.