The kiss is one of the most intimate forms of human expression, and there are myriad types. These include the affectionate kiss that parents give to children, the reverential peck that Catholics bestow upon the ring of the Pope, the platonic kind used to greet friends, and, of course, the vigorous cheek-pinch-and-kiss combo practiced by zealous aunts everywhere. But of all these, the kiss that expresses romantic love is the most commonplace and enduring, occurring in more than 90 percent of human societies. In fact, the odds that an undergraduate student 18 or older has kissed at least 20 members of the opposite sex are 1 in 4.26! All this lip-locking makes kissing seem like a trivial, unremarkable activity, but recent research suggests there is more to the romantic kiss than meets the lips.
In a 2007 study published in the journal Evolutionary Psychology, a team of researchers led by psychologist Susan Hughes examined gender differences in kissing among college students and the evolutionary foundations for those differences. What they found indicates that kissing is as much a science as an art.
According to the study, men and women swap more than spit when they kiss; they share important biological information as well. This is because our facial area is packed with sebum-producing sebaceous glands that are controlled by sex hormones. When we kiss, sebum is released from the glands and mixes with our saliva. Swapping sebum, the researchers suggest, may help people assess the health and hormonal conditions of their partner before they commit to sex (a metabolically expensive activity) or long-term involvement. Chemical cues also help people, particularly women, size up potential mates. Hughes and her colleagues found that women tend to base a man’s kissing ability on the smell and taste of his mouth. This is probably because foul breath and bad taste (apart from being unpleasant) are often symptoms of larger health problems.
The Wetter the Better
Gallup’s study also found that men prefer wetter kisses with more tongue action. Dr. Helen Fisher, a professor of biological anthropology at Rutgers University in New Jersey, theorizes this is because the sloppier the smooch, the more saliva—and hence, hormonal information—is exchanged. In a 2009 interview on the radio program Earth and Sky, Fisher explained that our cheek cells absorb the hormones estrogen and testosterone that are exchanged during a wet kiss. Men, suggests Fisher, may use this hormonal input to subconsciously gauge their partner’s fertility and reproductive potential. A man’s preference for extra-wet kisses may have to do with the fact that men are less sensitive than women to chemosenses like taste and smell.
Is the First Kiss Key?
The first kiss on a first date is notoriously nerve-wracking. We instinctively sense that a lot is riding on our performance. And there’s good reason—for most people, a bad first kiss can end a relationship before it’s even begun. In a separate survey, Hughes asked people, “Have you ever found yourself attracted to someone, only to discover after kissing them for the first time that you were no longer interested?” The majority of both male and female respondents answered yes. But if a bad kiss can end a first date, can a good kiss prompt one? Probably not, according to Hughes’s original study, which found that most men (69%) and women (67%) don’t believe in starting a relationship with someone just because he or she is a good kisser.