Copyright © 2010 John G. Hemry
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Science Fact: WHAT'S IN A KISS?: THE WILD, WONDERFUL WORLD OF PHILEMATOLOG by Richard A. Lovett
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"Since the invention of the kiss, there have only been five kisses that were rated the most passionate, the most pure. This one left them all behind."
—The Princess Bride
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"When you kiss me, without uttering a single word, you speak to my soul."
—Source unknown
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"We are all mortal until the first kiss and the second glass of wine."
—Eduardo Galeano
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Search the Internet, and it's easy to find hundreds of quotes like this. Every writer or poet with even a hint of a romantic streak seems, at one time or another, drawn to rhapsodize on the power of the kiss. And not just the first kiss. Consider this quote from John Keats (1795-1821): “You are always new, the last of your kisses was ever the sweetest."
But what exactly is involved in these lip-locks?
Love, obviously. Hopefully, some happily ever-aftering.[1] But that's not all. According to osculologists[2]—scientists who make their careers studying kissing—there's also an enormous amount of neurotransmitters, evolutionary biology, and instant assessments of potential life-mates. “It can be highly positive or highly negative,” says Helen Fisher, a professor of anthropology at Rutgers University. “Often the first kiss kills a relationship,"
Many customs vary widely from culture to culture, but kissing isn't one of them. As far back as the mid-nineteenth century, Charles Darwin noticed this and mailed questionnaires to missionaries, asking if people in the isolated tribes they dealt with kissed each other. The overwhelming answer was yes. In the 1950s, the study was repeated, with similar results. “Even where people found it disgusting, they did all kinds of other things,” said Fisher, in a pre-Valentine's Day press conference at the 2009 meeting of the American Association for the Advancement of Science. “Blow on the face. Tap on the face. Nip on the face."
Unless this is a truly massive coincidence, it means that kissing must do something biological: self-reinforcing, so that once people discover it, it drives out the types of cultural alternatives science fiction writers might otherwise invent (such as, say, pairs thumb-twiddling).
One prospect is that it shifts the body's hormone balance. To test this, Wendy Hill, a professor of neuroscience at Lafayette College, in Easton, Pennsylvania, recruited fifteen couples (all college students) and asked them to spend fifteen minutes alone together. One group held hands and talked. The other kissed. (Ah, the sacrifices we make in the name of science . . .)
Before and after, the researchers collected samples of blood and saliva, analyzing them for two critical hormones: cortisol and oxytocin.
Cortisol is a stress hormone. Oxytocin is related to feelings of trust, closeness, and pair bonding. Some scientists think it might be stimulated, early in life, by nursing and (in some cultures) premastication, in which mothers chew food before giving it to their infants. Since both of these are oral behaviors, it's possible that later in life, the same warm-fuzzy hormone is stimulated by other oral actions . . . such as kissing.
Also significant is the fact that humans aren't the only animals to exhibit such behaviors. Bonobos kiss and elephants put their trunks in each other's mouths. Foxes lick faces. “Some form of facial contact is common not only in mammals but also in avian and reptilian species,” says Fisher. Darwin wondered if kissing might be a natural instinct. “This might be in our hard-wiring,” says Carey Wilson, a student researcher at Lafayette College who helped with Hill's studies.
Precisely what our “hard-wiring” is leading us to search for, via kissing, is a subject of some debate. One prospect is that men are trying to taste sex hormones, such as estrogen, in women's saliva, subconsciously attempting to determine which women are most likely to be fertile. Another is that they're trying to make their dates more randy by passing on testosterone from their own saliva. Supporting this argument, Wilson notes, is the fact that while women tend to view kissing as a form of mate assessment and of maintaining a strong relationship, men often see it more as a prelude to sex.
Men also seem geared to maximize the exchange of saliva. “Men are more likely to like wet kisses with an open mouth with more tongue action,” Fisher says.
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Kissing in the Med Center
Hill's team found that even at baseline, the women had higher levels of oxytocin than the men: sad confirmation that most men might truly have only one thing on their minds.[3]
After kissing, cortisol declined in both men and women (compared to the hand-holding control group), indicating that stress had been reduced. But contrary to expectations, oxytocin increased only in the men. In women, it actually decreased slightly.
Perhaps something is wrong with the theory—though it's hard to understand how kissing might undermine the pair-bonding of already established couples.[4] Alternatively, perhaps the study group was too small to produce anything more than statistical noise in this part of the study.
Hill's team thinks the problem may have been that the experiment was carried out in the student health center. “It was done there for the convenience in drawing blood,” says EvanLebovitz, another of the student researchers. But that may not have been an ideal choice. “The setting wasn't very romantic,” Hill admits. “There were flowers and music, but it was a place where students go when ill."
She speculates that the setting may have been more disruptive to the women than the men. “We are in the process of running the study again in a more romantic setting."
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Human Pheromones
Insects produce pheromones: airborne sex chemicals that signal interest or draw prospective mates. Could people do something similar via kissing and related behaviors?
Quite possibly, say some researchers. Sarah Woodley, a neuroendrocrinologist from Duquesne University, notes that the simple act of blowing kisses might, to some degree, signify such intents. And many children, she notes, learn early to “throw” hugs. “Are we ‘throwing’ pheromones around?” she asks.
There is considerable debate over whether humans truly produce pheromones, but it's possible to sidestep that argument by speaking in terms of “chemosignals."
Such chemicals might well be transmitted via kissing. One older study reputedly asked people if they'd have sex with someone they'd never before kissed.[5] Not surprisingly, quite a few men (about half) said sure. Women, however, were highly unlikely to do so.
In another much-better-publicized study conducted three decades ago, scientists sprayed androstenone, a male sex hormone, on chairs in dentists’ waiting rooms. Women sat slightly more often in the sprayed chairs.[6] “But the data are problematic,” Woodley said. “There is a great deal of variability in the ability of people to detect it [androstenone]. A lot can't at all, and some find it sickening in smell, almost like urine. Others say it's like vanilla. So it's a complicated story."
Also of interest are “MHC” genes.
MHC stands for “major histocompatibility complex,” comprised of about a hundred genes. All are involved in immune function, but for some unknown reason they affect body odor.
What this means is that by smelling someone (or kissing them), you may be able to determine the strength of their immune system: valuable information in trying to determine if they'll be around long enough to raise your kids. Or you might be determining how genetically similar (or dissimilar) they are to you. Kissing someone with too close an MHC complex might produce subconscious cues akin to kissing your brother (or sister), good protection against inbreeding.
To test this, several research teams have asked people to sleep in the same T-shirts for several nights in succession. Then, other people were asked to rate the odors on the shirts, assessing, among other things, their pleasantness (or lack thereof) and
sexiness.
Six such studies were recently reviewed by a team that included Craig Roberts of the University of Liverpool, Woodley said. Most found that people preferred odors from people whose MHCs differed from their own.
Chemo-sensing (in this case by smell) appears to be real. But it's hard to pin down because there are plenty of cultural practices (up to and including arranged marriages) that can override it.
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My Adventure or Your Comfort Zone?
All of this is only the beginning. Fisher believes kissing may stimulate brain-affecting hormones and neurotransmitters linked to reproduction. She groups them into three basic brain “systems.” One is the sex drive. We've already talked about testosterone and estrogen in saliva and how kisses, particularly of the sloppy, wet variety, can exchange them. “Men do see kissing early in a relationship as a step toward copulation,” Fisher reiterates.
But in the long run, neurotransmitters might be more important. Fisher and her colleagues recruited forty-nine volunteers who were madly in love and put them in a brain scanner to see what parts of their brains lit up when they thought about the objects of their affections.[7] Seventeen had fallen in love recently, seventeen had been in love for years, and the rest had recently been dumped.
She found considerable activity in brain centers known to express two major neurotransmitter groups. One was dopamine, a natural stimulant linked to many types of pleasurable activities, including intense romantic love. This was particularly evident in the people who had recently fallen in love, who showed considerable activity in the brain's reward centers—what Fisher called “the brain systems for wanting, for craving, for focused attention.” So much for that single-minded perfection of new love: you're high on neurotransmitters. In addition to the dopamine, Fisher says, there's probably norepinephrine, which produces sweaty palms and a pounding heart.
This neurotransmitter cocktail, Fisher says, is an even stronger drive than sex itself. “People in stories kill for love, live for love, and die for love,” she says. Cupid's arrow is tipped with dopamine.
Rejected lovers had similar brain activity, plus some in regions of the brain active in cocaine addicts. No surprise, Fisher suggests. “Romantic love is an addiction when it's going well and horrible when not."
The long-term lovers were a bit different. They still showed activity in some of the flashy dopamine centers, but also had activity in parts of the brain associated with producing our friend oxytocin. “They're feeling not only romantic love, but also deep attachment,” Fisher says. They also exhibited a lot of activity in a serotonin-producing region associated with calmness. “These people are in love, but that early intenseness and anxiety is now replaced,” Fisher says.
How does kissing affect this? Well, new experiences stimulate dopamine and norepinephrine. “And certainly the first kiss is wildly novel,” Fisher says. “So it's entirely possible the novelty, [by] driving up dopamine and norepinephrine, could also trigger the brain system for romantic love."
Combine this with Hill's oxytocin/cortisol research, and other groups’ findings regarding sex hormones in saliva, and it appears there's a lot going on in a “simple” kiss. In fact, Fisher suggests, it may have evolved to stimulate all three of the brain's relevant hormone/neurotransmitter systems. “[The] sex drive got you out there looking for a range of partners,” Fisher says. “Romantic love got you to focus on one at a time. Attachment evolved to at least allow you to tolerate this human being long enough to raise a child together."
But Cupid doesn't hit everyone equally. Some people are strong in one neurotransmitter, some in another. Some appear to produce large amounts of one hormone, some another.
To learn more, Fisher teamed up with online dating giant match.com to determine what type of biochemistry produces the type of relationship chemistry we all crave.
Going into the partnership, she had determined that there were four basic hormonal/neurotransmitter types, or patterns: dopamine/norepinephrine, serotonin, testosterone, and estrogen/oxytocin. So she developed a survey to distinguish them—a sort of biochemical Myers-Briggs personality inventory. “We got seven million responses,” she says.
The four groups were quite distinctive. “Dopamine is more risk-taking, novelty-seeking, [and] creativity,” she says. “Serotonin is calm, social, cautious but not fearful."
High-dopamine people have energy and optimism and are good idea generators with many interests. They're also curious and verbal. Think “Obama,” she says. But they can be easily bored, impulsive, reckless. Addiction is a possibility. The word they're most likely to use in their online ads is “adventure."
High-serotonin people are more conventional. They have more close friends, are good at cooperation, and are persistent, stoical, conscientious, and tend to be more religious. But they can also be stubborn, closed-minded, rigidly moralistic, and controlling. In their ads, the most important words were “family,” “loyal,” “respect morals,” “trustworthy,” “caring.” They also tend to be rural. “I could point out the red states and blue states and see where the serotonin and dopamine was, and why these people don't understand each other,” Fisher said. “The whole language is different."
As an example of a high-serotonin person, Fisher suggests George Washington.
High-testosterone people are analytical, direct, decisive, tough-minded, work well in “rules-based” systems, and are good at math, computers, chess, and music. They're also emotionally contained. “If you watch a high-testosterone person on television, they're really only moving their lips,” Fisher says. “They're not moving much of the rest of their face at all.” The downside is that they can have poor verbal skills and be aggressive and uncompromising.
"I think John McCain is a perfect example,” Fisher says. “He was proud of being a maverick.” Not that this category is exclusively male. Fisher puts Hillary Clinton in the same group.[8]
Estrogen is usually viewed as a female hormone, but men can express it as well. “Football players have been found to be high estrogen as well as testosterone,” she says.
If you're looking for a good example, she says, think the other Clinton: Bill. Such people are consensual, holistic, able to see the big picture. They're imaginative, linguistic, intuitive and emotionally expressive, and have strong verbal and social skills. But they can also be indecisive, unfocused, gullible, effusive, ruminating, and unforgiving.
In dating ads, their favorite words are “passion,” “real,” “heart,” “kind,” “reader,” “sensitive,” “sweet,” “empathic."
Again, she points to the former President Clinton. “I feel your pain,” she says. “Only this type would say that.” And she notes, “His book was 963 pages. We all know he can't stop talking."
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So who do these people pair up with?
In most cases, Fisher says, similar brain chemistries attract. High-dopamine/norepinephrine people go with high-dopamine/norepinephrine people; high-serotonin people go with high-serotonin people. In other words, “adventurous” people go with other “adventurous” people and traditionalists want traditionalists—with the obvious caveat that other factors play big roles, ranging from intelligence and socioeconomic background to childhood experiences and religious preferences.
A lot of this makes biological sense. Emotionally, people who mate with similar neurotransmitter types are going to agree. High-serotonin types may both want to build a family, go to church, have a traditional Thanksgiving, etc. One question Fisher asked was whether people would rather have loyal friends or interesting ones. Only the serotonins preferred loyalty. “We all want loyal friends,” Fisher said, “[but] the other three can't tolerate uninteresting friends."
The exception to likes attracting are the testosterone people. “Testosterone goes for estrogen and oxytocin,” she says, again pointing to the Clintons. “In this case, opposites attract."
From an evolutionary perspective, she adds, high-dopamine people might be pro
grammed to seek out mates with wide-ranging interests that expand their own. High-serotonin people might be seeking to reinforce their own strengths. And testosterone-estrogen pairs may seek each other out in order to combine divergent resources.
Not that all of this is written in concrete. It's possible, her survey found, to rank high on more than one of the four scales. “I've found people who are high on three of the four,” she says. “The outlier is serotonin. If you're expressive of it, you're low on the others, mostly."
All of this obviously has a lot to do with Valentine's Day, but what does it have to do with kissing? Possibly a lot. There's got to be a reason why so many cultures use kissing as a preliminary step in mate assessment. “I think we'll find that kissing is a real adaptive mechanism,” Fisher says. “The brain becomes very activated."
Her main point, though, is much simpler. “Who you choose to mate with is one of the most important things you do,” she says.
Thus, it makes sense that we have a lot of biological processes designed to help us do it right. On top of that is the fact that we have “these four very broad constellations” of personality types. “These play a role in attraction when you kiss."
So, when you kiss your sweetheart this Valentine's Day, remember that you might be exchanging a lot more information than you think. But remember also that humans are creatures of will and spirit as well as biochemistry. I know one couple (both high-serotonin types) who chose not to kiss until their wedding. A silver anniversary later, they're tightly enough pair-bonded you'd think they'd been mainlining oxytocin. Others worship from afar for months, or even years, before they finally acknowledge it. And then—well, it's Princess Bride time. Maybe the normal “kiss” signaling has been done by other means. Humans are, after all, complex creatures.
If we weren't, what fun would science fiction be?
Copyright © 2010 Richard A. Lovett
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[FOOTNOTE 1: Not that this is required. “The default assumption is that people kiss in an erotic or romantic situation,” says Donald Lateiner, a professor of classical studies at Ohio Wesleyan University. “But there are other occasions.” In some cultures, for example, social kissing is common among people of equal status. In others, kissing can be a sign of deference or superiority. “[That's] sometimes called kissing up, or down,” Lateiner said. (An example would be kissing a bishop's ring.) But this article is timed to come out near Valentine's Day, so let's go with the cultural flow and focus on romance.]
Analog SFF, April 2010 Page 8
