Why we kiss: The science behind smooching and your cycle

Do you remember your first kiss? Was it at a school dance in a humid auditorium? Or perhaps in your neighbor’s dilapidated treehouse? Wherever it was or whomever it was with, your first kiss is probably one of your earliest vivid memories.

Kissing, pressing the lips upon a person or thing, is a common bodily gesture used as a marker of salutation, desire or love. Characteristics of kissing can have different meanings across situations and cultures, from casual greetings to choosing a partner.

According to a study done in the US and UK by the University of Oxford, kissing is an important behavior in sexual relationships for a few reasons: mate assessment, a means to initiate arousal for sex and behavior to maintain closeness in a relationship (1).

The report by Oxford states initial instinctual attraction between people is based on facial and body cues — but to determine whether a person is worthy of long term commitment, kissing may be crucial. It’s a means of courtship, and through this phase it serves as indicator of mate compatibility (1).

Have you ever found somebody appealing, but after kissing them you were no longer interested? That may actually be your genes saying, “Nope! Not the one for you.”

When a kiss occurs, there’s a complex exchange of “visual, tactile, postural and chemical information based on olfactory and gustatory cues” (2). Components triggered at the moment of a kiss evaluate subtle factors of a person’s general health, which determines “genetic compatibility and reproductive viability;” bad breath or oral lesions could be symptomatic of poor resistance to pathogens (2).

Basically if you explore a sexual prospect’s mouth with your own mouth and you feel aloof afterwards, it’s possible you subconsciously detected signals of subpar overall health; and if you’re fertile, you don’t want their genes in your offspring (2).

So in the words of Sylvia Plath, “Kiss me, and you will see how important I am.”

The menstrual cycle contributes to kissing’s significance. One study observed people in their late follicular phase may deem kissing to be of particular importance (1). Ovulation — when chances of conception are highest — occurs mid cycle, between the follicular and luteal phases. Thus kissing is thought to be extra significant during the end of the first part of the cycle because it includes the fertile window, ie. the time when becoming pregnant is possible, so mate evaluation is heightened. During the late follicular phase the top preference in a partner’s qualities was found to be fitness, which can be representative of quality of health (1).

Kissing has also been connected to greater sexual satisfaction. Locking lips — particularly with saliva exchange — serves as a way to facilitate arousal, which was found to enhance a sexual experience for most people (3).

One study found that people who engage in more foreplay (which included deep kissing) and affectionate behavior after sex (gentle kissing) reported greater sexual fulfillment (4). Furthermore, kissing correlates to higher likelihood of female orgasms (4). The study showed that deep kissing during a sexual encounter was associated with increased probability to orgasm in females.

For established couples, kissing was found to correlate with relationship longevity, as it’s also used as a means to initiate affection and attachment. Kissing was additionally found to be used as a means to initiate reconciliation (2). More smooching = a better bond.

Kissing is an instinctual behavior for important reasons: it analyzes partner suitability, instigates eroticism and solidifies intimate relationships.

Do you notice the urge to kiss more during your fertile window? Track your sex drive in Clue.


References

1. Wlodarski R, Dunbar RI. Menstrual cycle effects on attitudes toward romantic kissing. Human Nature. 2013 Dec 1;24(4):402–13.

2. Gallup Jr GG, Frederick DA. The science of sex appeal: An evolutionary perspective. Review of General Psychology. 2010 Sep;14(3):240.

3. Hughes SM, Harrison MA, Gallup Jr GG. Sex differences in romantic kissing among college students: An evolutionary perspective. Evolutionary Psychology. 2007 Jul 1;5(3):147470490700500310.

4. Frederick DA, John HK, Garcia JR, Lloyd EA. Differences in orgasm frequency among gay, lesbian, bisexual, and heterosexual men and women in a US national sample. Archives of Sexual Behavior. 2017 Feb 17:1–6.