One of the most complicated aspects of female desire, Dr. Meana says, is that women often want different things at different times. "Women are complicated, but I don't think they're confused," she says. "They want to be desired sometimes. Sometimes they also just want sex. They want a combination of things."

Some women don't want sex at all, and Dr. Meana says that doesn't necessarily mean a relationship is in jeopardy. "Bad sex happens to good couples all the time—: no sex happens to good couples," she says. "A lot of good relationships don't have good sex [because] ... we're tired, it's the end of the day. You put the kids to bed, you've done all of the things that you had to do and you don't feel like it."