Secret of Sticking to partner REVEALED!

"Sexual monogamy is actually quite costly for males, so there must be some form of mechanism binding males and females together, at least for some time,"

Hurlemann said. "There must be some benefit, and reward is actually the strongest motivation underlying human behavior."

An expert who was not involved in the study said the results suggest that couples who keep a high level of intimacy in their relationships can maintain stronger bonds.

"When you're first becoming intimate, you're releasing lots of dopamine and oxytocin. That's creating that link between the neural systems that are processing your facial cues, your voice and the reward system" of a partner's brain, said Larry Young, a professor of psychiatry at Emory University in Atlanta. He studies the role of oxytocin in social bonding.