Helen Fisher

Perhaps it is the eye—not the heart, the genitals, or the brain—that is the initial organ of romance, for the gaze (or stare) often triggers the human smile.

Smiling, it seems, we were born to do. Some infants begin to imitate their mother’s smile within thirty-six hours after birth, and all babies begin social smiling at about three months of age.9 Even children born blind and deaf burst into radiant grins, although they have never seen this facial gesture in those around them.