It’s the classic story of the Odd Couple: she’s the life of the party, while he gives any excuse to leave early. He’s orderly and fastidious, while she leaves milk on the counter and clothes on the floor. He’s logical, she’s emotional; he’s from Mars, she’s from Venus. Much is made of the idea that opposites attract, and we all know at least one of these “odd couples” that makes a relationship work despite major differences. But is it true that opposites attract? And more importantly, what makes for the most successful relationship—a stimulating opposite or a comforting soulmate?