Think fast: When you go in for a kiss, do you lean your head to the right or to the left?
Chances are, you lean to the right.
Although scientists have suspected this for a while, what they haven’t been able to pin down up until now is why. Is it something we learn from pop culture? Or is it innate? Previous studies have come out on both sides, but a new study published in the journal Scientific Reports suggests that it may have more to do with chemistry than culture.
The study, led by researchers from the University of Bath’s Department of Psychology, began with competing notions. One is that human beings tend to have an innate bias toward turning to the right in general. The other is that cultural factors also contribute to which way we lean when we kiss. Although science tells us that even before birth, humans seem to want to “go right” (human fetuses seem to prefer to turn their heads to the right during the final weeks of gestation), cultures that read from right to left have been found, in research settings, to tend to turn to the left when kissing. At the same time, researchers have postulated that head-turning bias is related to whether the person is right-handed or left-handed. However, 90 percent of the world’s population is right-handed, while science has documented that only two-thirds of people turn to the right when kissing.
“Although prior studies have made important contributions to the understanding of laterality in kissing, a limitation is that they did not investigate the roles of kiss initiators and kiss recipients in producing the head-turn during kissing,” the authors note. Other researchers also didn’t study kissing behaviors in people who do not typically observe romantic kissing in public—so they would be free from any pop-culture influence. Into this breach, the researchers from the University of Bath (as well as the University of Bath Spa and the University of Dhaka in Bangladesh) decided to invite 48 married couple from Bangladesh to kiss privately in their homes and then report on various aspects of their kisses, independent of their partners.
What the researchers found, predictably, is that over two-thirds leaned to the right when kissing. But what they found that was novel was that kiss recipients tend to match their partners’ head-leaning direction, and those who initiated the kiss tended to do so based on whether they were right-handed or left-handed.
The setting for the study was significant, the study authors said in a press release issued by the University of Bath, because kissing in Bangladesh is a very private behavior, something censored from television and film. “Whereas similar results from the Western countries could be attributed to cultural factors or having learned how to kiss through influences on TV or film, the same cannot as easily be said for a non-Western country like Bangladesh.” This was also the first study in the world to show that kiss recipients have a tendency to match their partners’ head-leaning direction.
That said, the researchers note that there is a strong cultural bias against being left-handed in Bangladesh, which makes it unclear whether one’s handedness matches his or her innate hand preference. Given that men were about 15 times more likely than women to initiate kissing, the researchers hypothesize that there may be something chemical at work, perhaps relating to testosterone levels, or perhaps dopamine (a chemical related to our reward center), which gives rise to the bias toward turning right.