According to a new study, most people are "wired" to turn their heads to the right when they kiss. The study was done by scientists at the University of Bath, in the U.K., and looked at the "directionality bias in head-turning during kissing."
In the study's abstract it states:
"Humans have a bias for turning to the right in a number of settings. Here we document a bias in head-turning to the right in adult humans, as tested in the act of kissing."
They looked at 48 married heterosexual couples What they found was that most couple turned their head to the right when they kiss. The researchers believer that the direction you tilt your head is based on your predominant hand, which is why turning to the right is the most common.