This semester I’m teaching in a classroom where, as happens all to often, the wall-mounted projection screen, when pulled down, obscures most of the white board that I’m supposed to write on. I’m left with perhaps two square meters of writing space. For several weeks I was frustrated with the mis-design of the classroom — for this course I show a lot of images and use a lot of unfamiliar terminology that I write on the board.
One day in class I realized that the lack of writing space could actually serve a useful purpose — instead of erasing the board to fill it up with more writing as I talked, I could use a it as a signal that it was time to take a break from lecturing. I began timing myself by watching the clock on the opposite wall, and sure enough, filling that space with notes took me about ten minutes, the same as the typical attention span of undergraduates. It was my cue to interrupt the lecture by posing a question or two to the students and engaging them in a conversation.