A certain professor of psychology was annoyed because the same female student, time after time, sat in the front row and knitted while he lectured. Thinking it undignified to order her about, he slipped into his lecture a casual remark that knitting was a substitute for masturbation. She raised her hand and said "Professor ----, when I masturbate, I masturbate, and when I knit, I knit."

(I used to hear this told about a particular psychologist, but since he publicly denied it, I am letting him rest in peace.)