Heliconian butterflies choose mates with similar wing patterns. Their genes make them do it.

Since the 1980s, more and more couples have sought therapy. Why is it so helpful to have that third person in the room?

For white, middle-class women in the 19th century U.S., courtship and marriage offered less emotional intimacy than their friendships with other women.

Three states have legalized covenant marriage, which makes divorce difficult. Why didn't it stick among communities preoccupied with family values?

How romance novels—despite their decided lack of cultural clout—became big business for the publishing industry.