In the course of his or her professional preparation, every teacher has had the experience of having to listen to a long lecture on the evils of lecturing. Lecturing is a high status activity: not only do professors do it almost exclusively; but, generally so do teachers down through middle school.
Why do teachers at all levels talk so much? Isn't a picture "worth a thousand words"? Not only do teachers tend to underutilize visuals in their teaching in the middle and high schools, but university faculty (and students, too) tend to react to the use of visual aids with hardly disguised condescension. Rapid-fire loquaciousness is mistaken for profundity of thought. Lips move and heads bob and understanding remains untested.
We are trapped in antique metaphor. For example, when we understand something, we say that we "see" it. As teachers we chatter away to make things "transparent" to our students. We take joy in a "bright" student, who is a "clear" thinker. But these visual metaphors are misleading, the rubble of ancient philosophies. Something else is needed.
To examine these issues further, see The Mind’s Eye and Pedagogical Practice