Back in college astronomy class, I sat behind a guy who wore a T-shirt with this on the back: " The best thing about the opposite sex is just how opposite they are."

It’s not just a rule in physics. There’s a strong cultural expression: opposites attract. Think Harold and Maude, Pretty Woman, It Happened One Night—Hollywood has long known the lure of antitheses in love.

But real research busts this myth.

Psychologists map out such evidence in a new book: 50 Great Myths of Popular Psychology: Shattering Widespread Misconceptions about Human Behavior.

Psychologist Donn Byrne has found that we are twice as likely to be attracted to someone when we agree on six out of 10 issues than we are with someone who we only agree with on three out of 10 issues.

To be sure, the appeal of shared interests may be specific to long-term relationships.

A 2006 University of Pennsylvania study of speed dating found that daters said they wanted someone who had a similar background in education, religion, economic status and shared personality traits. Yet when they were in the midst of the one-minute date, they made choices based on more immediate cues like physical attraction. In the speed-dating environment—a bar surrounded by singles, under the pressure of a ticking clock—daters made choices based on short-term mating criteria that were more likely to lead to fast hook-ups, not necessarily long-lived love.

So if it’s the long haul you’re searching for, best look beyond the cute face and hot body, and see if you can carry the conversation beyond 60 seconds.

—Christie Nicholson