TIME - Apr 5 - Lookalike couples have captured public fascination for years. Back in 1987, scientists from the University of Michigan set out to study the phenomenon of married couples who grow to look more alike over time. (Their theory, which scientists still cite today, was that decades of shared emotions result in a closer resemblance due to similar wrinkles and expressions.) Psychologist Justin Lehmiller says people naturally gravitate toward people who are familiar, even though the whole process is likely subconscious. "You're familiar with your own appearance, so seeing other people who share those similar sorts of traits might lead to more liking for that reason," he says. Lookalike partners may also be drawn to each other, subliminally, because of their genes.