Though kissing may be considered first base by some, new research says this sexual activity has many functions in a relationship, but sexual arousal isn’t one of the more important ones. Theories on kissing, a behavior that is unique to humans, suggest that we do it to help assess genetic quality of potential mates, increase arousal, and keep relationships together. Researchers at Oxford University used an international survey of over 900 men and women ages 18 to 63 to determine which of these factors were true and whether there were differences based on sex, length of relationship, and physical attractiveness. The results were published in the Archives of Sexual Behavior. A companion study, published in Human Nature, also looked at whether women have different opinions about kissing at different points in their menstrual cycles.
The first study found that women tended to find kissing more important than men. In addition, men and women who rated themselves as being attractive, as well as those who said they tended to have short-term relationships and casual encounters, rated kissing as more important than other survey participants. The authors see these findings as support for the role of kissing in mate selection because, as they noted, previous studies have found that women are more selective in choosing a partner (most likely because they are more invested in their offspring). As the researchers noted, previous studies have also suggested that men and women who are attractive or have more casual sex partners are also more selective when choosing their mates. Given that these are the same groups who value kissing more, the researchers believe that kissing helps in mate assessment.
It is still not clear how kissing works in mate selection, though previous research cited by the researchers has suggested that it allows people to pick up on biological cues of fitness and compatibility through such senses as taste and smell. Robin Dunbar, the lead author of the current study, explained in a statement, “Mate choice and courtship in humans is complex. It involves a series of periods of assessments where people ask themselves ‘shall I carry on deeper into this relationship?’ Initial attraction may include facial, body, and social cues. Then assessments become more and more intimate as we go deeper into the courtship stages, and this is where kissing comes in.”
In the companion paper, the researchers noted that women valued kissing more at certain stages of their menstrual cycle. For example, they found that during the initial stages of a relationship, women valued kissing most when they were at their most fertile part of their cycle. The researchers note that previous studies have confirmed that women are pickier about mates when they are at their most fertile—at that time of the month they look for “supposed signals of underlying genetic fitness, such as masculinized faces, facial symmetry, social dominance, and genetic compatibility.” The researchers concluded, “It appears that kissing a romantic potential partner at this time helps women assess the genetic quality of a potential mate.”
As part of the first study, the researchers also concluded that kissing is important in maintaining long-term relationships. Survey respondents in long relationships said kissing was equally important at all times, whereas for those in short-term relationships, it was most important right before sex, less important during or after sex, and the least important at all other times. The researchers believe this shows that in committed relationships kissing plays a big part in maintaining a lasting bond. And kissing may indeed help maintain that bond; the researchers found that more frequent kissing in a relationship was linked to the quality of the relationship.
Interestingly, the least important role of kissing appears to be the one we often think most about—getting us turned on and ready for sex. A statement on the study explains that “While high levels of arousal might be a consequence of kissing (particularly as a prelude to sex), the researchers say it does not appear to be a driving factor that explains why we kiss in romantic relationships.”