A study conducted by UCLA's Department of Psychiatry has revealed that the kind of face a woman finds attractive on a man can differ depending on where she is in her menstrual cycle. For example: If she is ovulating, she is attracted to men with rugged and masculine features. However, if she is menstruating, or menopausal, she tends to be more attracted to a man with duct tape over his mouth and a spear lodged in his chest while he is on fire.
No further studies are expected.
(thanks Amy D - got a chuckle out of this)