The Science of Kissing: What Our Lips Are Telling Us

by Sheril Kirshenbaum

  So what about off the screen? Computer scientists are giving us a sneak peek at what may be next on the horizon in the evolution of kissing—robots that kiss one another or, perhaps someday, kiss us.

  In 2008, the world saw the debut of Taiwan’s kissing robots, “Thomas” and “Janet.” These somewhat lifelike machines were designed to “kiss” at the National Taiwan University of Science and Technology. They are, reportedly, the first robotic pair to lock lips, an action involving complex hand-eye coordination and precise balance.

  Thomas and Janet are part of a group of performing robot actors, but might this new technology suggest more about what’s to come? Although these bots are not intended for human interactions, it’s possible that computers could eventually look and act convincingly enough to serve as surrogate human partners. Androids (male robots) and gynoids or fembots (female robots) have been depicted in films such as Millennium Man, A.I., and Austin Powers. As science advances, there is anticipation of more realistic intimate physical interactions with them. But the notion of kissing machines that have been programmed to simulate us is no longer just part of science fiction.

  In 2010, a full-sized female companion robot, named “Roxxxy,” debuted at the Adult Video News Adult Entertainment Expo. Touted as the world’s first robotic girlfriend, she stands five feet seven inches tall and weighs 120 pounds. Roxxxy’s computer employs speech-synthesis and voice-recognition software, and according to the website she

  knows your name, your likes and dislikes, can carry on a discussion and expresses her love to you and be your loving friend. She can talk to you, listen to you and feel your touch. She can even have an orgasm!

  It certainly sounds intriguing, but can she kiss?

  To find out, I called the company. It turns out Roxxxy has a motor in her mouth with sensors, but cannot take an active role in kissing. Instead, her mouth was designed to be pleasurable for other oral purposes. Like the rest of her, it was molded from the body of a female fine arts model, and serves as one of three “inputs” for users.

  Roxxxy’s engineers predict that companion robots will become commonplace in people’s homes over time. Since presumably her main buyers are men—who, as we’ve seen, do not generally place very high significance on kissing—most will probably not miss the activity. However, TrueCompanion.com is currently preparing to release a male sex robot named “Rocky.” Will a stronger female market request an enhanced kissing feature? There are currently no plans to develop this kind of function, but they carefully consider feedback when deciding on future updates. However, even if scientists engineer the perfect kissing robot, it would lack a human element that is impossible to program: the ability to form real lasting social bonds.

  EVERY DAY, new technologies change the way we interact with the world, from how doctors cure disease to the ease with which we stay connected to our social network. So although it’s not possible to predict exactly what’s in store for kissing in the future, we can already imagine some interesting possibilities. Perhaps it will be possible to “kiss” a loved one through the computer, or maybe virtual technology will allow us to experience the kiss of a celebrity or idealized partner. Just as with inventions like space shuttles and smart phones, the coming decades will reveal new kissing technologies that we can’t begin to imagine in the present day. Still, there’s one thing to be sure of: The kiss as we know it will never go out of style, because it promotes an important connection. But on a personal level, the meaning of a kiss will continue to change—just like our relationships.

  A Look Back in Time

  Online dating has emerged recently, but advertisements for romance that feature kisses have been around for a long time. Nineteenth-century newspapers frequently included love notes, marriage proposals, and missed connections from singles in burgeoning cities. According to Rutgers historian Pam Epstein, they became so popular that there was even a manual available on how to compose a reply. This ad appeared in the New York Herald on March 20, 1870, page 1:

  Will the lady with dark hair, to whom, while at a window with a friend this (Friday) morning, a card was shown, kindly send her card to the gentleman, whose name her friend knows? He regrets that he is compeled [sic] to resort to this method of making the request, but trusts that, under the circumstances, she will excuse and permit him (mentally) to kiss her hand.

  No word on whether the lady with dark hair ever replied or received his kiss in person.

  CHAPTER 13

  The Right Chemistry

  From Cleopatra to Casanova, we remember those who were legendary for the art of seduction. But can science help us understand what they seem to have known intuitively—or at the very least guide us toward leaving the most lasting impression with our lips?

  The truth is, it depends. A scientific understanding of endocrinology, olfaction, and other subjects can surely help improve the chances that a first kiss will go well, by making us more aware of how we may be affecting a partner. Science may give us an advantage, then; but how we use it is another matter, and the facts alone cannot provide the perfect ingredients to win someone’s heart and be unforgettable. That takes charm and a fair amount of serendipity.

  We kiss to express affection, adoration, respect, and love. We kiss to celebrate new beginnings and to say good-bye. We kiss because we care, or want to appear to. It all results in a staggering amount of brain activity and many complex changes in our bodies. I’ll end this final chapter with some very concrete tips about how, based on the latest science, to be a better kisser—but first let’s survey how far we’ve journeyed.

  When it comes to kissing, we’ve seen that millions of years of evolution are working to direct us. Peering across the animal kingdom demonstrates the remarkable power of physical displays of affection—often of a kissing-like nature—to connect individuals in strong relationships. Though we vary from our mammalian relatives in many respects, in the end humans work in very much the same way. We need to share, to connect, to communicate beyond just using language; and kissing has been a dramatically successful means of doing so.

  Today we see kissing practically everywhere, albeit in highly varied forms across the globe. It is a perfect example of how both “nature” and “nurture” combine to create a single complex and variable behavior, in this case one that fosters intimate social bonds among its practitioners—bonds we depend on for love, support, security, and even survival.

  We’ve also seen that when we kiss, our bodies instinctively know a great deal about what to do and how to respond to another person. We collect a staggering amount of sensory data throughout the experience, and that data in turn set off a cascade of electrical and chemical reactions, which then modulate our behavior and help us decide whether the kiss works and whether we want to continue or go even further.

  All of this unfolds at incredible speed in ways that science has barely begun to understand. After all, and as we’ve seen, research on the brain’s response to kissing barely exists in the scientific literature, and the results revealed by New York University’s MEG machine raise many new questions. Research on kissing is just getting started, and we can assume that over the coming decades we’ll know vastly more than we do at present.

  Still, we’re now in a position to at least take a crack at answering the questions we asked at the beginning of the book, based on the work of Niko Tinbergen, about why humans kiss.

  “ULTIMATE” EXPLANATIONS

  WHERE DID KISSING COME FROM?

  Other species, including many primates, engage in behaviors that are remarkably similar to what we call “kissing.” Indeed, our close relatives, bonobos, quite literally kiss mouth-to-mouth, just as we do.

  Animals engage in kissing-like behaviors for a wide range of reasons, from expressing affection to a simple greeting. Some animal “kisses” probably help promote special relationships between mothers and offspring, or between members of the same troop. In other cases, many species engage in a kissing-like motion to deliver chewed food
to their young—and some human cultures also continue this practice today.

  All of this affirms that what we call “kissing” has a deep biological history and is certainly not limited to humans. Rather, the broad distribution and persistence of this behavior suggests it plays a key role in holding individual members of different species together in romantic pairs, in family units, or in social groups.

  In ancient humans or their ancestors, kissing may have first emerged from a search for sustenance and sex, from sniff greetings, from the feeding relationship between mother and child, or perhaps a combination of all three. We can’t say for certain, but each possibility is supported by the observation of similar behaviors or displays in other species. One thing is for sure: Kissing worked, and it stuck. It is both ancient and common around the world, although different styles have gone in and out of fashion depending on events and sociocultural norms.

  HOW DOES KISSING BENEFIT US?

  Like sex, romantic kissing is a behavior that facilitates reproduction. In this sense, its relationship to success in the competition to pass on one’s genetic material is obvious. Kissing benefits us by helping us live on, through our genes, in our immediate offspring and beyond.

  Seen in this light, many aspects of the kissing experience appear explicitly engineered to ensure reproductive success. For humans especially, female lips—much like female breasts and buttocks—serve to attract members of the opposite sex, acting almost as a kind of bull’s-eye. The larger and redder they appear, the more attractive men seem to find them.

  Actress Mae West once said, “A kiss is a man’s signature.” She was right. Besides mere attraction, there’s a subtler way in which the kissing experience guides our reproductive decisions even further. A good deal of the scientific literature speculates that kissing may have evolved to help us choose a suitable partner, or to realize when a match is a bad idea. Kissing may serve as an investigative tool that brings us close enough to taste, smell, and interpret cues from a partner, so as to assess the potential for a relationship. The exchange of olfactory, tactile, and postural information might trigger unconscious mechanisms that guide us in deciding whether we should continue, and a kiss might even tell us about a potential partner’s level of commitment and genetic compatibility.

  These unconscious cues probably work for both sexes, but in different ways. For men, a larger and plumper female mouth is attractive—and that’s probably no accident. Large lips may subconsciously inform a man of a woman’s fertility or her health.

  A woman, in turn, can tell a great deal about her partner by his kiss, even if she’s not aware of it. Her body may react to the taste of his lips, his tongue, and his testosterone-laden saliva, as well as the way he positions his body—all of which help her decide whether he’s worth mating with. Meanwhile, her acute sense of smell might offer additional information, particularly if his natural odor provides a window onto his genes and whether potential children from this union will have a strong immune system.

  Both partners, then, have hidden skills to help them evaluate the other through a kiss. So in a sense, their kiss can serve as nature’s litmus test of their relationship and whether it will produce healthy offspring. That’s quite a benefit—to us, and to our species.

  “PROXIMATE” EXPLANATIONS

  WHAT MOTIVATES US TO KISS?

  Romantic kissing usually occurs when two individuals share a sense of closeness and intimacy. The precise trigger for this behavior varies from relationship to relationship, but always involves complex biological, physical, and social influences. Perhaps most important is a combination of craving and emotional attachment spurred on by the neurotransmitters and hormones in our bodies, such as dopamine and oxytocin. These substances promote a sense of desire and anticipation. They also encourage us to keep going when the match and moment are right.

  Context is also extremely important for eliciting a kiss. For the first kiss especially, a comfortable and secure environment encourages the exchange. And no wonder: Research suggests that kissing reduces the body’s levels of cortisol, a stress hormone. A good kiss brings the sense of relaxation, as well as positive feelings of reward and security, thus reinforcing the behavior and leading to further kisses.

  HOW DO WE KNOW HOW TO KISS?

  Kissing may be learned early, through the affection expressed by family and friends toward a young child. Even in infancy, the manner in which a mother presses her lips to an infant to kiss or feed stimulates pleasure centers in the baby’s brain. So does nursing. These sensations may lay down an early cognitive map for the positive feelings associated with kissing that will later emerge in adult relationships.

  However, such early experiences are by no means required to join the international kissing community. Nor do they always imply that a child will express love through the lips as an adult. In several cultures that do not traditionally kiss on the lips in a romantic fashion, individuals have nevertheless been observed to premasticate meals, or to kiss children as a sign of adoration.

  Today, kissing is so ingrained in most societies that it is nearly impossible to avoid encountering it. There can be little doubt that in the United States our urge to kiss is strongly influenced by Hollywood, fairy tales, people we see on the street, and the chatter among peers as we’re growing up. We see kissing on television, on billboards, and at school. We read about it in novels and magazines. The behavior is better advertised than Coca-Cola.

  All of these influences lead us to want to kiss, to feel it’s something we should do to express love, and to “know” that it should be done in a mouth-to-mouth fashion (even though not all human cultures have agreed). Thus it is from the complex interplay between our biology, our psychology, and our cultural expectations that the knowledge of how to kiss has emerged.

  THAT’S WHERE SCIENCE STANDS on kissing—but it’s not the only kind of information this book intends to convey. Let’s face it: We want to be memorable kissers, and I would be extremely remiss not to close with some scientifically based tips. To that end, here are ten lessons that emerge directly from the science discussed in the preceding pages. Some may sound familiar, but they take on new resonance and force once you recognize the science behind them.

  1. PLAY UP YOUR ASSETS—WISELY. Certain cosmetics serve to make our lips more alluring for a very good reason: Men like lips, and they like them red. So if makeup is your style, a little gloss or shine may send the right signals, making you look your most alluring.

  But at the same time, the research also suggests not to overdo it. Lipstick appeals to a very primal urge, but men don’t like a fake-looking pout. Moderation is critical. Evolution has made our lips naturally seductive no matter what we do—so long as we don’t go too far in making a spectacle out of them.

  2. IMPROVE YOUR TASTE AND SCENT. Taste and smell can make a big difference in the kissing experience and serve to lure in the opposite sex. So if you want to be a memorable kisser—in a positive way—you should brush and floss your teeth every day to keep the bacteria in your mouth in check. In particular, it is critical to ward off the gum disease gingivitis, which can leave you with chronic bad breath, missing teeth, and even an increased risk of heart disease.

  Although some odors are beyond our control, you can further stack the odds in your favor by avoiding certain spicy or strong foods. Keep a breath mint or chewing gum nearby, in case you have not had time to properly prepare for a fortuitous kissing encounter.

  3. GET TO KNOW EACH OTHER. If you want your first kiss with a partner to be magnificent, it’s crucial to spend lots of time learning about each other first, so as to lay down the right hormonal foundation. In the process, both of you will be building a bond with a strong chemical basis. In particular, you need to encourage the firing of those hormones that foster feelings of attachment and adoration, so that you each develop an emotional investment that sets the stage for a physical connection. That way, by the time things move to the next level, oxytocin will already be your ally—and k
issing may only reinforce the closeness you already share.

  4. FOSTER ANTICIPATION. Yearning for something makes finally getting it all the better, and a kiss is no exception. If Rhett had kissed Scarlett in the opening scene of Gone With the Wind, audiences wouldn’t have remained nearly so invested in what happened to the couple after that. It was far better to watch the sexual tension build—and in our own lives, feelings work precisely the same way.

  The first kiss will be most pleasurable if each person has been dreaming about how, when, and where it will take place. When both individuals feel the thrill of the chase, the result upon final contact could be of the kind that poets describe with violins and fireworks.

  That’s the romance novel version of this advice, but the science backs it up: Even when you’ve already got oxytocin on your side, you still need dopamine to foster desire. Before a kiss, you want this neurotransmitter spiking to its highest levels yet—at least before things get more physical.

  That’s why a fumbling drunk cannot seriously expect his sloppy kiss to impress a stranger (unless perhaps she’s equally drunk). By contrast, a couple that talks and flirts for hours in a comfortable setting builds up anticipation. By getting to know each other, they begin to pick up subtle clues about whether the other person is interested. The boundaries of personal space break down as a bond begins. When they finally kiss, the dopamine reward for each will be greater, and the kiss will be all the more memorable.