From a comment by Linda Lin on my Nature Network blog:

Nevertheless, there is a habit of teaching the way we ourselves were taught, even if this is not the most efficient approach.

I went to a workshop for TAs and instructors addressing the issue of sort of flying blind in teaching. They emphasized on the importance of training and reading up on teaching every so often. One researcher said, well, we’ve been taught science for 20 years, surely we’d know how teach it without needing any training. His head of dept retorted that “I’ve had sex for 20 years, that doesn’t make me a qualified gynaecologist”.