Decoding Love

by Andrew Trees

  Unsurprisingly, both sexes also share similar feelings about what qualities are the most important. In one 1990 study, both men and women considered warmth and consideration the most important qualities. When it comes to intelligence, both sexes want at least average intelligence in someone they are dating, although if the question is whether or not to have sex with someone, men are willing to sleep with someone of less than average intelligence, while women seek someone of more than average intelligence. Women do place a greater emphasis on sincerity, which David Buss argues is a code word to judge a man’s commitment. Women also place more emphasis on having a sense of humor.

  LEAVE THEM LAUGHING

  Humor deserves its own special treatment. As anyone who skims through the personal ads knows, sense of humor is an absolutely essential quality. Everyone wants it in his or her partner, and no one will admit to lacking it. Any time I asked men or women what qualities they looked for, sense of humor was at or near the top of the list. Why should that be the case? Researchers did a very interesting study that helps provide some answers. They asked a group of women to read vignettes about various men. The key variable that changed from story to story was the man’s sense of humor. In some stories, the fictional man had an excellent sense of humor. In others, he had an average one. And in still others, he had a poor sense of humor. The study found that men with an excellent sense of humor were endowed by female readers with all sorts of other good qualities. Women saw them as more sensitive, more adaptable, happier, more intelligent, more masculine, and even taller. All of these additional attributes were not because of anything in the vignette. They were entirely the result of the man’s sense of humor. In other words, women unconsciously use sense of humor as a proxy for many other traits, such as creativity and intelligence. This helps explain why humor is always high on the list of desired qualities. It is not just for that quality in and of itself but because it acts as a signal for so many other sought-after qualities as well.

  To see how deeply this is woven into our psyches, you only need to look at the results when the researchers took into account a woman’s fertility. When a woman was at her peak fertility and looking for a short-term relationship, her attraction to the man with an excellent sense of humor spiked sharply. Men with average or below-average humor found their ratings unchanged, which confirms that humor acts as a proxy for good genes in general. Humor may even be worth the importance that so many of us place on it. One study revealed that women’s humor rating of their partners significantly predicted their general relationship satisfaction. But there remains a crucial difference between the sexes. Studies show that men tend to be the ones who make the jokes, and women tend to be the ones who laugh at them.

  Unfortunately, none of this is the holy grail of dating. At best, it gets you only a small way toward figuring out what to look for in a partner. When it comes to personality, science still only has a rudimentary understanding of why one person is attracted to another.

  THE BRAIN—ADDICTED TO LOVE

  Many of you clever readers probably have a nagging question in the back of your minds going all the way back to those provocative lap dancers at the start of the chapter. All well and good to give us this advice about things to look for and how to attract a mate, you’re thinking, but it sounds as if none of this might be in our control. After all, if attraction is tied to things like a woman’s fertility cycle, who cares who is batting whose eyes at whom? And you would be quite right to raise that objection. While it doesn’t negate the previous pages, it does leave one area unexplored, and that area may be the most powerful of all: our own body chemistry, those signals ranging from smell to ovulation to hormones over which we have no control.

  There is a great deal of emerging scientific evidence that being in love does strange things to the brain. According to functional MRI scans, infatuated love activates the same brain circuits as obsession, mania, and intoxication. One study found that the areas of the brain activated by cocaine were the same ones that became active when lovers were shown photographs of their partners. People in love also have high levels of PEA, a natural amphetamine found in chocolate. It may be what helps fuel the sudden ability to go without sleep as you stay up all night with your lover. Louann Brizendine, a neuropsychiatrist, has compared the brain activity of a person in love to that of a drug addict craving his next fix. And when people talk about the pain of a broken heart, they are being more literal than you would think. Rejection activates the same brain circuits as physical pain. In fact, being in love literally rewires the brain. One of the chemicals released is oxytocin. Along with causing feelings of euphoria, it also appears to melt old neural connections so that large-scale changes in the brain can take place. This makes it easier to learn new things, such as replacing feelings of love for an old partner with feelings of love for a new partner.

  These physical manifestations of what once seemed to be merely metaphoric descriptions are not surprising when you start to explore how much physical space our sexual organs monopolize in our brains. Stefan Klein writes, “If the size of individual organs were commensurate with the space given them in the brain, the penis and the vagina could easily outweigh the entire upper body.” In fact, it’s not much of a stretch to say that the brain itself is the most important sexual organ in the body and that, as Helen Fisher claims, the search for love is a fundamental drive like hunger or thirst.

  When we fall in love or even when we simply experience desire, a whole slew of chemicals is involved—dopamine, nor-epinephrine, phenylethylamine, oxytocin, and vasopressin to name just a few. Of course, what goes on in men’s brains and what goes on in women’s brains are quite dissimilar. For instance, women in love have activity in different regions of their brain than men in love. This difference can be seen in a wide number of related areas as well. Take, for example, the issue of women’s sexuality. It is a much more elusive phenomenon than men’s sexuality. Physical cues, such as wetness or swelling, do not necessarily indicate sexual arousal or appetite, and according to one study, while heterosexual men were predictably turned on by footage of naked women, the opposite was not true. Videos of naked men did not necessarily cause more arousal for women than the control footage of snowcapped mountains. What really got women going was the degree of sensuality. When that was present, women put men to shame in the polymorphous nature of their desires. Not only did they respond to videos of naked men—they also responded to videos of naked women. In another study, women were even genitally aroused by footage of bonobo chimps mating (which evoked no response from men), although the women did not consciously experience any sense of arousal.

  Studies of our neurochemistry can tell us a great deal about the nature of sexual attraction. For example, the waning of desire is a common problem for all couples—and not just the human ones. Researchers have dubbed this the Coolidge effect because of a famous incident involving the former president and his first lady. According to the story, the first couple were separately touring a government farm. Mrs. Coolidge noticed a rooster mounting a hen and asked how often the rooster copulated. The answer was dozens of times a day, to which she replied, “Please tell that to the president.” When Coolidge was later told about this exchange, he asked if the rooster always mated with the same hen and was informed that the rooster copulated with different hens. Coolidge smiled pleasantly and said, “Tell that to Mrs. Coolidge.”

  Scientists can now offer concrete evidence of the Coolidge effect by monitoring the level of dopamine in animals before and after copulation (dopamine has been dubbed the “molecule of desire” because it is the chemical that motivates us to attain our goals). Take a recent study of rats. When a male rat was shown a new female, his dopamine rose 44 percent, a number that continued to increase before sex but that dropped off drastically after the rat climaxed. The second time he copulated with the same female, the spike in dopamine was smaller, and after several times, the dopamine level hardly rose above normal. If you placed a new female rat on dis
play, though, the male rat’s dopamine rose by 34 percent. In our age of casual sex, all of this has major implications for our relationships, and a strong chemical argument could be made that people looking for long-term partners would be best served by prolonging the period of courtship. Unfortunately, for the swingers among us, it appears that our grandparents’ advice about people not wanting to buy cows when they can get the milk for free has a scientific basis.

  Our brains have a funny quirk built into them that enhances this effect. They thrive on a challenge as long as that challenge is not so difficult that it seems impossible. It is the expectation of a reward, rather than the reward itself, that appears to stimulate dopamine production. We all have experienced this at one time or another. Just think back to the last time you deeply longed for something and how achieving that goal proved far less exciting than thinking about it. In fact, even meaningless goals, such as reaching a new level on a video game, can activate our neurons and get our hearts pumping faster. What this means for women is that their best strategy for ratcheting up a man’s level of dopamine and making herself more irresistible is to make sex with her a challenging goal. Once sex occurs, a man’s dopamine level and his desire will inevitably fall off, although a woman can probably maintain it at a higher level if sex does not become a foregone conclusion but something that a man has to earn on a continual basis.

  THE SCENT OF ATTRACTION

  Of course, once scientists started to consider the chemical basis for love, they realized that what frequently underlies attraction is not strangers in the night exchanging glances but exchanging smells. For a long time, scientists dismissed as preposterous the whole idea that humans could be attracted to one another based on smell. In recent years, though, they have discovered that smell can and often does play a crucial role, which brings me to one of my favorite experiments—the smelly T-shirt test.

  It could have been worse. Scientists could have asked us to smell one another’s urine. The first inklings that smell might play a role in human attraction came not from humans but from rats, specifically from a segment of DNA called the major histocompatibility complex or MHC for short, a sequence of more than fifty genes located along a single chromosome that is different for each and every individual. The reason behind this almost infinite diversity is that the MHC acts as a kind of warning system for the body by detecting disease and alerting the body’s defenses to attack, and it has to deal with a bewildering multitude of attackers.

  One of the unusual aspects of the MHC is that it is codominant, rather than dominant. With a trait controlled by a dominant gene such as eye color, only the version from one parent will be expressed. With codominant genes, though, both versions continue to function in the offspring. This is a great advantage when it comes to fighting disease. If a father’s genes contain immunity to one variant of the disease, while a mother’s genes contain immunity to a different variant of the same disease, the offspring will have immunity to both versions of the disease.

  Now, back to those pesky rats. It turns out that when a female mouse was offered two different males with which to mate, she always chose the one whose MHC genes were most different from her own. This makes sense as that choice will increase the immunity of her offspring. Her method of selection? Smelling the urine of the male rats. This put sex researchers off the scent, as it were, because humans do not typically make a habit of smelling one another’s urine. But then researchers stumbled on a very interesting discovery—humans can smell the difference among mice that differ only in their MHC without having to rely on urine at all. With that, a Swiss biologist named Claus Wedekind designed an experiment to see if he could discover a similar ability in women smelling the MHC of men (women have greater smell sensitivity than men), and thus, the great smelly T-shirt experiment was born. Although Wedekind’s findings are better known than most of the studies I discuss, they still deserve close attention because the key element driving smell preference is often not explained, and the shocking results relating to contraception are frequently left out.

  More than eighty college students participated in the study. The men were given cotton T-shirts to sleep in for two consecutive nights. To guard against any wayward smells creeping into the picture, they were told not to eat spicy foods, not to smoke, and not to drink any liquor. They also had to avoid any deodorants, cologne, or perfumed soaps. And, of course, no sex. During the day, their T-shirts were kept in a sealed plastic container.

  The women were also primed for the experiment. For two weeks prior to the test, they used a nasal spray to protect the mucous membranes lining their nose. Around the time they were ovulating, when their smell was enhanced, they were put to the test: a row of boxes with a hole cut in the top, each containing the T-shirt of one of the men. After inhaling deeply from each box, the women rated each man’s shirt for sexiness, pleasantness, and intensity of smell. What the researchers discovered demolished any lingering doubts about the role of smell in attraction.

  Wedekind and his staff found that how a woman rated a man’s smell depended entirely upon how much of their MHC profiles overlapped. Because a person’s MHC profile is incredibly idiosyncratic, what smells good to one woman will not necessarily smell good to another, and short of genetic testing, there is no easy way to predict what a woman will find appealing. For instance, race does not exert much influence on it. All of this made the results of the study even more astounding. The more a man’s MHC profile differed, the more the woman rated his smell as pleasant and sexy (a later study found that you can be too different—if there are no MHC genes in common, women are not attracted to the man’s smell).

  The evidence also suggested that this attraction was not confined to the lab. Women said that the smells they preferred reminded them of current or ex-boyfriends roughly twice as often as men with similar MHC profiles, so smell had likely played an important role in their real world mate selection as well. No matter what the MHC profile, though, strong body odor was a turn-off. Researchers theorized that a strong body odor is often an indicator of disease, so that women may have evolved an aversion to strong smells as a means of avoiding a genetically unfit mate. In fact, odor appears to be yet another marker of genetic fitness. In a different study, women judged symmetrical men to be better smelling than their nonsymmetrical counterparts.

  There was one other surprising finding: women taking oral contraceptives had preferences that were the opposite of women not on the pill. They chose men who had similar MHC profiles. To give you some idea of how potentially disturbing this reversal is, women generally described the smell from men with similar MHC profiles as reminding them of their father’s or brother’s odor. Traditionally, it may have made sense for a woman to stay close to her family during her pregnancy to ensure her protection and care. But that evolutionary development is clearly being blindsided by scientifically engineered contraceptives, which fool a woman’s body into thinking that it is pregnant. As if that wasn’t bad enough, another study has shown that women on the pill see the world in a more platonic light, which is clearly counterproductive for single women looking to find a partner because it might blind them to the romantic possibilities around them.

  Similar MHC genes have also been shown to cause a host of problems for couples. According to one study, partners who have more difficulty conceiving a child share significantly more of their MHC genes than couples who have dissimilar MHCs. Doctors have also found that couples with more similar MHC profiles suffer from higher rates of miscarriage. It even has an effect on sexual fidelity. As MHC profiles become more similar, researchers have found that a woman’s sexual responsiveness to her partner diminishes. She is more attracted to other men, and she is, on average, unfaithful with a greater number of men. With 50 percent of the profile in common, a woman has a 50 percent chance of sleeping with another man. These studies clearly suggest that any woman who is serious about finding a long-term partner should avoid oral contraceptives. By outwitting nature, we may have actually outw
itted ourselves and undermined an important element of mate selection—smell.

  If a woman does decide to go off the pill, I do have to warn that there will be one unexpected downside if she chooses to use condoms instead—she will no longer have the medicinal benefits of semen. That may sound even more preposterous than the T-shirt study, but it’s the truth. Unlikely as it sounds, semen contains powerful, mood-enhancing chemicals that are absorbed through the vaginal wall (digestion is a different matter, so this doesn’t apply to fellatio). According to a recent study, women who don’t use condoms and have regular sex are less depressed than women who use condoms or women who aren’t having sex.

  Of course, women have probably intuitively understood the power of smell all along. A surprising number of women I interviewed said that smell played a crucial role in their dating, and some even claimed that they could immediately “smell” if a man was right for them. One woman even said that she liked to smell her boyfriend’s armpit—and not when he was fresh out of the shower. Not since Walt Whitman have I seen such a ringing endorsement of the sweet smell of armpits. Our hygiene-obsessed society makes it more difficult for women to smell whether a protective partner has the right stuff or not, which might help explain why kissing plays such a large role in most relationships. Our saliva also contains traces of our MHC, so kissing can reveal what our daily showering hides. You do have to exercise some caution when relying on your nose, though. Fragrances can fool even the most astute sniffer, so you need to make sure that you are smelling the unadulterated scent.