Have you ever thought about which side you lean your head to when you're kissing your partner? Scientists have...

Do you lean to the left or the right when you're going in for a snog? Well, if you lean to the left you're in the minority according to scientists. A new study from an international team of psychologists and neuroscientists suggest that humans are hardwired to favour leaning to the right while kissing a romantic partner. Building on previous research on the same topic, a new academic paper just published in the journal Scientific Reports, is the first study in the world to show that the kiss recipients have a tendency to match their partners' head-leaning direction. The research team invited 48 couples to kiss privately in their own homes, and after kissing they were asked to go to different rooms, open an envelope and then report on various aspects of the kiss independently of each partner. Their results showed a bias to turn heads to the right when kissing for both the initiator and the recipient of the kiss, and also that men were about 15 times more likely than women to initiate kissing. Over two-thirds of the kiss initiators and kiss recipients turned their heads to the right. Interestingly, being right or left-handed predicted head-leaning direction in the kiss initiators, but not in the kiss recipients. When mirroring each other's head movements on request for a kiss, both the kiss initiators and the kiss recipients reported that they felt physically uncomfortable kissing in that way. Lead author Dr Rezaul Karim, from the department of psychology at the University of Dhaka, says the findings suggest that the act of kissing is determined by the brain splitting up tasks to its different hemispheres - similar to being either right or left-handed:

"Head turning is one of the earliest biases seen in development, even in the womb a preference for turning the head to the right is observable before that of favouring the right hand or foot. Whether this fundamental bias is innate and extends into adulthood is a lingering question for neuroscience and psychology."

Dr Karim says this is the first study to show that men are more likely to initiate kissing:

"We as humans make lots of behaviours while interacting with others everyday, but almost all the time we are not aware of the biases we have in those behaviours, such as in turning the head to one side during lip kissing. Prior studies also poorly understood the phenomena as they ignored the role of kiss recipients or were unable to disentangle the impact of kiss initiators on the head turning direction in kiss recipients. This is the first study to show sex differences in the initiation of kissing, with males more likely being the initiator."