ABSTRACT
Imagine a classroom in which your teacher slouches in late and begins scribbling an outline for a lecture on the chalkboard. Eventually he turns and starts an algebra lecture by reading directly from a textbook for the next 20 minutes. Your mind wanders, and you hear your classmates playing videogames on their cell phones and talking. You are brought back to attention when your teacher slams the book shut and calls you to the blackboard to complete one of the example problems.
