Let me hasten to say next that men have changed, too. They expect more of women, they demand more of women. Male eyes follow a pretty girl as unfailingly as ever, but they are eyes that carry more than a sexual question. There is plenty of simple physical sex, of course—and physical sex is, by the way, essentially a very simple business in spite of all the books written on the subject–but there is in the male calculation a question and a demand for something more, if a relationship is to continue. Brains are surprisingly often appreciated. Men enjoy being amused, diverted, stimulated to thought and consideration of new ideas, and once having had this new and surprising experience with a woman, they learn to demand it. This has, of course, an important effect on women, leading them to further self-development.