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Feb. 25, 2009

The Science of Kissing is All About Chemistry

by Guest Blogger

By Alan S. Brown

I remember kissing my first girlfriend, Barbara, in her backyard when I was 17. It was a warm spring day and things were starting to warm up when she suddenly pushed me away and said, "Why are we doing this?"

I tried the answer most likely to reapply my lips to hers, "Because it feels good."

That didn't work. "I mean," she continued, "would we kiss if the whole culture hadn't taught us to kiss? Would people naturally want to push their tongues into someone else's mouth?"

I don't remember where the conversation went from there, but I can assure you that it did not lead to kissing. In fact, it didn't lead to much of a conversation. I really had no idea how to respond to her questions, other than with adolescent anger and hurt feelings.

Now, I think I have the answers. Or at least some of them, thanks to a seminar on "The Science of Kissing" held at this year's American Association for the Advancement of Science (AAAS) meeting on --when else -- Valentine's Day. The session began at 8:30 AM, early enough to discourage lazy morning celebrations of the day. By the time I arrived, the double-sized room was jammed with scientists and reporters standing in the back and sitting along the walls.

The seminar featured several notable researchers in the field of philematology. Leave it to academics to invent a long, Greek-sounding name (that doesn’t even appear in Merriam-Webster) for something as common as kissing. Perhaps this is because they need to distance themselves from the obviously arousing nature of their work. Science, of course, should be objective. Still, I was encouraged to hear the promise made by one scientist who measured hormones in the saliva of student volunteers who kissed for 15 minutes in the campus health center. She planned to conduct her next round of research in "a more romantic setting."

And speaking of saliva, that's what kissing is all about. You and I might think of warm lips and soft probing tongues. Scientists see our mouths as small chemical reactors of swirling chemicals that not only turn us on, but also help us assess the health and childbearing status of potential mates.

Testosterone, a hormone associated with sex drive in men and women, is one. Men prefer sloppier kisses with more open mouth, says Rutgers University anthropologist Helen Fisher. This lets them transfer more testosterone to stimulate their partner's sex drive. Fisher, who studies the brain chemistry of love (check this video), speculates that men might be able to assess a woman's fertility from estrogen or other hormones in her saliva.

Wendy Hill, a neuroscientist (and provost) at Lafayette College, finds that kissing reduces stress (associated with the chemical cortisol) and increases pair bonding (associated with oxytocin).

Of course, there are always surprises. Hill ran her experiments on couples in the sterile confines of the student health center while playing romantic music. (Sounds as kinky as R-rated experiments get.) After 15 minutes of kissing, she found that oxytocin rose in men and so they showed more interest in bonding. Yet it declined in women, indicating less interest.

This was a surprise, since most researchers believe women are more interested in bonding than men. She plans to try the tests again in a more romantic setting (I hope she keeps the music).

This may make a difference. Or perhaps men really are more interested in bonding when they are aroused. As anyone knows who has listened to Meatloaf's "Paradise by the Dashboard Light," arousal can make a guy feel intensely (and not think wisely). But those feelings may be quick to cool. That's why I'd like to see Hill take a second blood sample an hour or two later. Let's see who has elevated oxytocin levels then.

Another important chemical in saliva may be androstadienone, a steroid that maintains positive mood and increased focus in women and some men, said Duquesne University neuroendocrinologist Sarah Woodley. "It may not be a sex attractant, but it plays a role in enhancing responsiveness to other stimuli. It makes them feel better," she explained.

Woodley also thinks smell plays an important role in kissing. She flashed the famous Burt Lancaster-Deborah Kerr kiss on the beach from the movie "From Here to Eternity" onto the screen. "Notice the skin-to-skin contact," she said. Even 55 years after that scene was shot, it was hard not to notice the body-to-body contact.

Speaking strictly scientifically, Woodley believes we may smell one another's skin and breath to determine the health of our partner. (Eyes apparently deceive, since I think both Lancaster and Kerr looked incredibly healthy.) She also thinks the area under the armpit, including skin, hair, and the local bacteria, is also an important turn- on. So not too heavy with the deodorant.

Clearly, kissing triggers an avalanche of hormones, steroids, and other chemicals. So many, in fact, that Fisher believes humans have evolved three separate mating mechanisms.

The first is testosterone-driven lust, the turned-on, feels-good type of exploration that compels us to look at a range of partners.

The second is romantic love, which Fisher says is stronger than our sex drive. "The first kiss is wildly novel," Fisher told her audience. That novelty can trigger a release of dopamine, a hormone associated with pleasure. Mix in some norepinephrine (heart pounding) and – this really makes sense – serotonin (obsessive thinking) and you have a recipe for romantic love.

Finally there is attachment. It is associated with high levels of oxytocin that "enable a couple to tolerate each other long enough to raise a child," said Fisher.

Fisher, who is also chief scientist at www.chemistry.com, a dating site, has written a book, Why Him, Why Her?, on how different temperaments associated with neurochemical systems may determine our relationships.

It may explain why the chemistry created by initial flirting sometimes turns sour after a first kiss. In fact, a survey of 1,041 college students by evolutionary psychologist Gordon Gallup of SUNY Albany found that 59 percent of men and 66 percent of women backed off from someone they thought was attractive after a first kiss.

And yes, kissing is common. Charles Darwin studied it in the first global ethnographic study, sending letters to missionaries around the world and asking them to describe behaviors. Studies in the 1950's showed that kissing played a role in 90 percent of all cultures. Even those societies that didn't kiss found ways to get intimate face time. Eskimos, for example, blew and tapped at each other's faces. (They were probably afraid of frozen tongue syndrome.)

Hey, even chimpanzees and bonobos, among our closest cousins, kiss. One researcher in another seminar mentioned a bonobo that once tried to tongue a zookeeper. Other animals do the best they can. Foxes lick noses. Birds touch beaks. And bees? Well, who knows?

So now, after more years than I care to remember, I can finally answer Barbara's questions. Yes, kissing is natural. We would probably do it even if our culture hadn't taught us. And yes, there are many reasons why someone might want to push their tongue into someone else's mouth.

I guess maybe it just wasn’t the right chemistry.

Incidentally, if you want to read a really good article on the latest in post-feminist sex research, I recommend “What Do Women Want” by Daniel Bergner in the January 25 New York Times Magazine. After all, who could resist a story whose first line is: “Meredith Chivers is a creator of bonobo pornography.”

About Guest Blogger

The views expressed are those of the author and are not necessarily those of Science Friday.

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