The premise of just about every romantic comedy is that opposites attract. From Roman Holiday (princess meets lowly reporter) to Annie Hall (neurotic Jew meets space cadet shiksa) to Harold and Maude (young meets old) to Pretty Woman (businessman meets prostitute) to Beauty and the Beast (beauty meets beast) to Love, Actually (prime minister meets housekeeper) to The Proposal (boss meets assistant), the presumption is that the most passionate love stories involve polar opposites. But the real lives of celebrities, not to mention social science research, show that it's just not true.
Tabloids have recently seized on the rumored romance between Sandra Bullock and Ryan Reynolds, both of whom recently broke off marriages with people perceived to be in some ways their opposite. Bullock, whose public image is Hollywood's girl next door, ditched tattooed biker husband Jesse James of Monster Garage fame, while Reynolds, a happy-go-lucky funny guy, called it off with the relatively artsy and ice-cool Scarlett Johansson. Their break-ups serve as a reminder that whatever Hollywood movies—even their own!—preach, the most successful relationships are like-meets-like.
It's an established tenet of social psychology that similarities rather than differences—whether in attitude, personality, age, income, race, or religion—produce a lasting relationship. "Opposites tend to attract in the short term, but not in the long-term," says Catherine Sanderson, a psychology professor at Amherst College who teaches a class on close relationships. "Over the long haul, one of the bigger predictors of success in relationships and marriages is similarity." (A marriage between people with similar qualities is known as homogamy.) There's less to fight about, for one thing. People from different religious backgrounds might want to raise children in different traditions, or those from disparate economic backgrounds might clash on the importance of education. Agreement, meanwhile—whether on movies, restaurants, religion, or favorite romantic comedies—produces positive emotions and more fruitful relationships. (It's also true that similar people are more likely to meet each other in the first place: If you like sports, you're more likely to be in situations where you'll run into other sports lovers.)
Not only is like attracted to like, like becomes more like like over time. In other words, similar people become more similar once they enter a relationship. Or at least they think they're more similar. There's a difference between perceived similarity and actual similarity. Perceived similarity is likeness in how two people describe each another; actual similarity is likeness in how they describe themselves. When two people start dating, they start to see similarities in each other—even if those similarities don't exist. For example, if you think of yourself as intelligent, you're likely to start seeing your partner as intelligent, too. People want to make relationships work, after all, so they look for common ground. Previously disparate views can actually get closer, says Marian Morry, professor of social psychology at the University of Manitoba:"If you hate liver but your partner likes liver, you'll eat more and they'll eat less."
When two people first meet, their differences might seem attractive. For example, an introvert might enjoy being around someone who's friendly and outgoing. But over time, differences start to wear. Someone who at first seemed spontaneous begins to seem irresponsible and flaky. That quiet and mysterious person appears brooding and isolated. What was once gregariousness becomes never shutting up.
That doesn't mean couples can't disagree on anything. Some researchers have found that small disagreements in otherwise stable relationships can lead to "self-expansion" as couples discover new things through their partners. But the more important the area of disagreement, the less likely it is that the relationship will work out. For example, two people can have different religious views and still have a healthy relationship—as long as religion isn't that important to either one. Likewise, the less serious the relationship, the less of a problem big differences are. One survey of college students found that "similarity was positively correlated with liking only in high-commitment relationships." In low-commitment relationships, dissimilarity was actually a good thing.
There are plenty of examples of functioning "opposite" relationships, such as that between political consultants James Carville and Mary Matalin, who worked for opposing presidential campaigns in 1992. But even they have more in common than not. They're both highly paid TV pundits who live and breathe politics. They might disagree on many political issues, but that probably doesn't outweigh their attitudes on, say, personal spending or religion or how to rear their two children. Same with Hollywood celebrities. Even if two stars have reputations that would categorize them as opposites—Tom Cruise and Katie Holmes, say, or Ashton Kutcher and Demi Moore—they've got plenty in common to fall back on: money, attractiveness, fame, extroversion, and liberal political views.
Yet the "opposites attract" myth persists—and it has consequences. When asked, most people say they're attracted to people unlike them, even though they overwhelmingly pick mates with similar qualities. "People may partially draw upon lay theories of romantic attraction rather than their true desires for a mate," says Pieternel Dijkstra, a professor at the University of Groningen in the Netherlands. They assume dating someone like them is "boring," he says. But in the long run, it's either that or be single.