Good point. I do remember well how uncomfortable it was to be called upon when I was unprepared to answer--that is, to provide the answer the professor expected to hear. From my own experience, I know those students who avert their eyes don't want to be called upon. I don't ever pressure a student to participate--but try to create an atmosphere of ease in the classroom, so that, in time, even the shy students feel comfortable to speak up--or look up.
