To follow up on Lee’s post, here is Cosma Shalizi.
An anecdote relevant to Shalizi’s re-framing of Jensen’s original argument: I have a colleague who has taught the same large introductory course several times. By now, the class content doesn’t change from semester to semester, and in all likelihood the class demographics don’t change much from semester to semester. But last spring he made one change: he replaced his casual attire with a shirt, pants, and jacket. He told us that his teaching evaluations went up noticeably.