If you have a date for this evening, no doubt you’re looking forward to sharing a kiss (or several) with your Valentine. No one has described the mysterious power of the kiss better than Chekhov, in his short story “The Kiss,” when a stranger plants one on Ryabovitch:
We may recognize Ryabovitch’s symptoms, but most of us would be hard-pressed to describe why a kiss has this effect. In fact, kissing is so widespread that it rarely occurs to us to interrogate it. If you do think about it, though, all this mouth-pressing, saliva-swapping, and tooth-knocking really does seem odd. So why do we do it? As Sheril Kirshenbaum—a research scientist at the University of Texas and blogger for Discover magazine—explains in an engaging new book, “The Science of Kissing,” the answer is far from simple. Drawing on sources from literature, history, evolutionary biology, psychology, popular culture, and neurology, “The Science of Kissing” probes various theories of kissing, how it may have originated, why we seek it out, and what it does to our brains and bodies. I recently spoke to Kirschenbaum about this mysterious act, its past, and how we use it to define and negotiate relationships. An edited version of our conversation appears below.
What happens in our bodies when we kiss?
In a good kiss, our pupils dilate, which is one of the reasons we close our eyes, our pulse quickens, and our breathing can deepen and become irregular. But we’re also hard at work on a subconscious level. Scent plays a really powerful role in whether it’s a good kiss or not. Women are actually most attracted to the natural scents of men who have a different set of genes called the major histocompatability complex that codes for immunity. We’re most attracted to people whose MHC genes have a lot of diversity from ours—the advantage of that would be if you reproduce, that child’s probably going to have a stronger immune system, and so be more likely to survive to pass on their genes. This isn’t something that we’re consciously aware of, but we do seem to know if something feels off. And actually, more than half of men and women—fifty-eight per cent of women, fifty-nine per cent of men—report ending a budding relationship because of a bad kiss.
_How important is a couple’s first kiss?
A first kiss has the power to shape the future of a relationship for a particular couple. Of course, there are other factors that play a role, but kissing is really nature’s ultimate litmus test. It puts us right up close so that we can sense whether this is someone we want to continue a relationship with. If it’s a good kiss, there’s an associated rise in the neurotransmitter dopamine, which is associated with strong feelings of craving and desire. Kissing also stimulates the same pleasure centers in the brain that are associated with addictive drugs like cocaine, so kissing really does act on the brain and body like a drug. There’s also a rise in the hormone oxytocin, which is known as the love hormone and is important in terms of social bonding and really committing to someone, and serotonin, the neurotransmitter that is often associated with obsessive-compulsive thoughts. It was really interesting to me as I was writing this book and learning about the chemicals coursing through our brains and bodies, to discover that when we think about these symptoms we associate with being in love, well, there’s a real chemical basis for that.
You mention in the book that there’s a real gender gap when it comes to kissing. Are men really from Mars?
I was pretty shocked by the gender differences between men and women. It actually really irritated me! I started dipping into evolutionary psychology work that had been done and coming across men reporting kissing as a means to an end—a way to get to sex—whereas women were saying that kissing itself is significant, that it helps figure out what he’s thinking, or how he feels about me, or whether we have a future together. Over and over, around the world in different studies, kissing was reported as much more important to women. I ended up calling Gordon Gallup, an evolutionary psychologist at SUNY Albany, and talking to him about why this existed. When we got down to it, it has a lot to do with reproductive biology, because men, from a strictly biological standpoint, are a lot less picky when they’re choosing a partner, whereas women invest much more time and energy into reproduction. We’re fertile for a much smaller period of our lives, so it’s really important to figure out whether someone would be a good genetic match. So when we’re up close and personal with someone, kissing them, we’re actually more sensitive to things like taste and smell and really engaging all of these senses as we kiss.
I was surprised to learn that women can actually take in testosterone from a man’s saliva during a kiss.
That was so funny, because I kept coming across people saying that too much tongue is gross, and that it’s kind of silly, but there’s actually an evolutionary reason for it. It’s to a man’s advantage to be slipping a woman the tongue. He’s of course not aware of it, but he’s giving her a bit of the male hormone testosterone, which over the weeks and months might enhance her libido, and she might then be more receptive to sex, so it’s to his benefit to do so.
I was amazed by the variety of kisses you bring up, including my two new favorites, Aristophanes’ “Doorbolt” and “Spread-outer.” Without an official taxonomy, how do you sort through the many ways we kiss?
The Romans had three categories of kisses, and the Kama Sutra classified kissing in many different ways. Aristophanes was actually mocking kisses in his plays—none of those kisses were supposed to be particularly good. In terms of modern science though, scientists can’t even decide what a kiss is. That’s probably part of the reason its been so ignored for such a long time. For the book I described it as touching one’s lips to another individual’s mouth, or another part of the body or object, which is pretty general. Darwin actually talked a lot about “kissing like behaviors” and basically broadened the definition to include many other things he saw in other cultures that were not kissing mouth-to-mouth. But then again, not everyone was brushing their teeth and using mouthwash then, so a mouth-to-mouth kiss was probably a very different experience! But if you broaden the definition of kissing to include nipping, rubbing, licking, patting on the face, or even other parts of the body, then it seems to be a universal behavior.
I read once that the kiss was invented by women in the Middle Ages to see if their husbands had been drinking. Myth?
Cato, the Roman statesman, did advise Roman soldiers to kiss their wives when they returned home to see if they’d been drinking, so maybe that’s where that evolved from. But really, the amount of misinformation on kissing is huge. I kept coming across the “fact” that there are twenty-six calories burned in a kiss, and I knew that just didn’t make any sense, but I started to wonder because this was mentioned over and over. Then, on Halloween two years ago I was eating Hershey’s Kisses, and whatever flavor it was happened to have twenty-six calories in it! So, I guess at some point someone wrote that there are twenty-six calories in a Hershey’s kiss and that found its way into the science on kissing.
So how long have humans been kissing?
The earliest literary reference that we have is from India’s Vedic Sanskrit texts, but I would suspect that kissing predates anything that we have written evidence for. Looking around the animal kingdom there are so many similar behaviors in other species. We can’t call them “kissing,” because we don’t want to anthropomorphize, and we don’t know what motivates another animal. But bonobos for example will suck on each other’s tongues for about twelve minutes straight—and they’re probably doing so for some kind of affectionate reason. There are fish that touch lips in conflict, gerbils that tap heads, all these different species that do something similar. It’s always about connecting with another individual for some significant purpose—whether it’s out of self-preservation or affection or a grooming behavior. So I think humans have probably been kissing, in some way or another, for as long as we’ve been here.
You mention that the scientific term for kissing is “osculation,” which sounds terribly unromantic to me. In diminishing the mystery, does studying the science of kissing diminish the romance?
It had the opposite affect on me, actually—I still feel that romance is so important. Studying the science of kissing for as long as I have gave me a much greater awareness of how significant this single thing that we do is in our lives, and how much it really matters in our relationships. So I’m actually a lot more aware of, for instance, taking a moment to kiss my husband goodbye in the morning when he’s leaving the house. To me it’s a great example of the way that science can really help us in our relationships to understand ourselves and our partners. And this was actually one of the things I was hoping to do with the book. We’re so disconnected from the world of science, so while I hope this book will be a fun journey, I also hope it will encourage people to think a little differently about what science is and why it matters so much in their lives.
Can science give us any clues as to how to be especially effective kissers this Valentine’s Day?
Well, there are certainly things beyond our control—if it’s a star-crossed match, your body’s going to sense that—but there’s also a lot we can do. The obvious things, of course: women pay a lot of attention to the taste and the breath of the person they’re with, so basic personal hygiene is pretty important. But then there’s also making a person comfortable. Environment matters a lot in terms of whether we enjoy the kissing experience. If the timing is bad, or if you’re feeling pressured, you’re going to get a stress hormone called cortisol in your body, which really isn’t conducive to a good kiss. Also, if there’s a lot riding on a kiss, for instance if it’s someone you’ve been after for a long time, really getting to know them, so that you’ll both be dreaming about and anticipating this kiss before it happens, will make it much better when it does.
But the most important thing, I think, is that when you’ve found a partner, you should take the time to kiss them often. We should all be kissing more. For the important relationships in our lives, it matters tremendously.
(Author Photo: Gretchen Mathison)