Just to note - I am not a huge doodler overall, but in those university lectures where I wasn't taking extensive notes (because the material was in the textbook) I doodled abstract designs endlessly. A small amount of physical distraction actually helped me stay mentally focused. Otherwise, my mind would start to think about more interesting things, and wham - next thing I know I've totally wandered and have no idea what was said for the last ten minutes.
I knitted my way through most of my classes at MIT for the same reason. I had to do complicated increase/decrease patterns at home between classes, though, and save the long straight repetitive stretches to do in class.
