Majority of humans are hardwired to lean to the right while kissing romantic partners, a study has found.
Building on previous work from Western countries, the research is the first to investigate an inherent bias for turning the head to one side while people kiss in a non- Western context, in Bangladesh, where romantic kissing is not typically observed in public.
The study, published in the journal Scientific Reports, is also the first to show that kiss recipients have a tendency to match their partners' head-leaning direction.
Researchers from University of Bath in the UK and University of Dhaka in Bangladesh, invited 48 married couples to kiss privately in their own homes.
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.
The results highlight 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.
Handedness predicted head-leaning direction in the kiss initiators, but not in the kiss recipients.
In addition, the kiss initiators' head-leaning direction strongly predicted the kiss recipients' head-leaning direction.
This suggests that the kiss recipients have a tendency to match their partners' head-leaning direction in order to avoid the discomfort of mirroring heads.
In fact, when mirroring each other's head movements on request for a kiss, both the kiss initiators and the kiss recipients reported that they felt discomfort kissing in that way.
The setting for the study was significant as kissing in Bangladesh is a very private behaviour; something censored from television or films.
While similar results from the Western countries could be attributed to cultural factors or having learnt how to kiss through influences on TV or film, the same cannot as easily be said for a non-Western country like Bangladesh, researchers said.
The study suggests 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 - specifically the functions in the left cerebral hemisphere, located in the emotion and decision-related areas of the brain.
The researchers suggest different hormone levels (such as testosterone) in each hemisphere and neurotransmitters might be unevenly distributed to each hemisphere (such as dopamine, involved in reward behaviours) as giving rise to a bias to turn right.
This may have implications if you are left handed and your partner is right-handed or vice versa.
It is likely that as a kiss initiator you will alter your partner's spontaneous head leaning to a comfortable direction or as a kiss recipient you will be affected in a similar manner by your partner's head leaning direction, researchers said.
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