Kissing is fun and feels lovely, but what is causing us to want to lock lips?
New research out of Oxford University suggests it's a way we size up our mates.
There are three working theories about why we, as opposed to other species, like to kiss, according to Time magazine website. Kissing can arouse, it cements relationships together or it's a trial run of a potential mate.
Researchers from Oxford's department of psychology recently provided evidence for the latter.
Rafael Wlodarski and Robin Dunbar set up an online survey and asked about 900 adults (around two-thirds of whom were women) to answer questions about how important kissing was in both long and short relationships. Overall, women valued kissing more than men (no surprise there), but gents who rated themselves as more attractive than others or who had lots of girlfriends also placed greater importance on pashing.
"Mate choice and courtship in humans is complex," Dunbar said in a statement discussing the work.
"It involves a series of periods of assessments where people ask themselves, 'Shall I carry on deeper into this relationship?'
The early judgment calls are all based on facial, body and social cues.
"Then assessments become more and more intimate as we go deeper into the courtship stages," he said, "and this is where kissing comes in."
So how does a kiss predict compatibility? Time said this isn't clear, but quoted evidence from some philematologists (people who study kissing) who think it could have something to do with smell:
In her book The Science of Kissing, Sheril Kirshenbaum cites Claus Wedekind, who she says found that "women are most attracted to the scent of men who have a very different genetic code for their immune system in a region of DNA known as the major histocompatibility complex." Having different DNA from the individual you are kissing heightens the chance of having healthy offspring should the kissing lead somewhere.
Other scientists believe women send off a signal if they're ovulating that can be subconsciously detected if a mate is close enough.
The Oxford study also found that women were more likely than men to say kissing was more important in long-term relationships.
"Men are more likely to initiate kissing before sex, when it might be used for arousal purposes," the authors wrote, "whereas women are more likely to initiate kissing after sex, where it might better serve a relationship maintenance function."
But perhaps the biggest and most useful takeaway from the survey was this: Lots of kissing was associated with a satisfying and ultimately healthy long-term relationship. The same can't be said about sex.
"There seems to be something special about kissing," Wlodarski told NPR.