People are hard-wired to tilt their heads to the right when kissing a romantic partner, an international study has found.
Building on work from western countries, the universities of Dhaka, Bath and Bath Spa set out to investigate kissing behaviours, including a bias for turning the head to one side.
The research, published in the journal Scientific Reports, studied 48 married couples in Bangladesh, where kissing is not generally observed in public.
The couples were asked to kiss privately in their homes and independently report on different aspects of the kiss. It found that men were about 15 times more likely to initiate kissing than women, and that both partners preferred to lean their heads to the right.
More than two thirds of kiss initiators and kiss recipients turned their heads to the right, with 79 per cent of men being the kiss initiator.
“This is the first study to show sex differences in the initiation of kissing, with males more likely being the initiator, and also that the kiss initiators’ head-turning direction tends to modulate the headturning direction in the kiss recipients,” Dr Rezaul Karim, from the department of psychology at the University of Dhaka said.
The data also revealed that being left or right-handed predicted the head leaning direction of the person that initiated the kiss, and that the head-leaning direction of the initiator strongly predicted that of the recipient.
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This suggests that recipients are likely to match the direction of their partner to avoid the discomfort of mirroring heads.
“This further suggests the underlying cognitive mechanisms of the act of kissing and head turning,” the authors said.
“Though this action tends to be performed intuitively, a decision must be made about the direction to which the partners should lean to kiss each other.”
As kissing in Bangladesh is private and censored from film or television, the researchers insist that this precludes any influence of cultural factors or copying.
“This study is unique in giving us a look into a private behaviour in a private culture with implications for all people. Prior works could not rule out cultural learning due to having western samples. It turns out, we as humans are similar even if our social values differ,” Dr Michael Proulx, from the department of psychology at the University of Bath added.
Ultimately, the research suggests that the act of kissing is influenced by the way the brain divides tasks between its hemispheres and that hormone levels, such as testosterone, might be unevenly distributed, causing a bias to turning right.