The Female Brain (11 page)

That our mental instincts haven’t changed in millions of years may explain why women, worldwide, look for the same ideal qualities in a long-term mate, according to the evolutionary psychologist David Buss. For over five years, Buss studied the mate preferences of more than ten thousand individuals in thirty-seven cultures around the world—from West Germans and Taiwanese to Mbuti Pygmies and Aleut Eskimos. He discovered that, in every culture, women are less concerned with a potential husband’s visual appeal and more interested in his material resources and social status. Rob had told Melissa he was a marketing consultant—they were a dime a dozen in San Francisco, and Melissa had seen more than a few go out of business. She didn’t realize that this thought was making it hard for her to figure out if Rob was Mr. Right or Mr. Right Now.

Buss’s findings may be uncomfortable at a time when many females are achieving at high levels and are proud of their social and financial independence. Nevertheless, he found that, in all thirty-seven cultures, females value these qualities in a mate much more than males do, regardless of the females’ own assets and earning capacity. Melissa may be an independent economic unit, but she wants her partner to provide, too. Female bowerbirds share this preference by choosing to mate with the male who has built the most beautiful nest. My husband jokes that he’s like a male bowerbird, since he built a beautiful house several years before we met, and it was ready and waiting for me. Women, researchers have found, also look for mates who are, on average, at least four inches taller and three and a half years older. These female mate preferences are universal. As a result, scientists conclude, they’re part of the inherited architecture of the female brain’s mate-choice system—and are presumed to serve a purpose.

According to Robert Trivers, a pioneering evolutionary biologist at Rutgers University, choosing a mate based on these attributes is a savvy investment strategy. Human females have a limited number of eggs and invest far more in bearing and raising children than males do, so it pays for women to be extra careful with their “family jewels.” This is why Melissa didn’t jump into bed with Rob on the first night, even though the dopamine and testosterone surging through her brain’s attraction circuits made him hard to resist. It’s also why she kept a number of other guys on her dance card. While a man can impregnate a woman with one act of intercourse and walk away, a woman is left with nine months of pregnancy, the perils of childbirth, months of breast feeding, and the daunting task of trying to ensure that child’s survival. Female ancestors who faced these challenges alone were likely to have been less successful in propagating their genes. Though single motherhood has become fashionable among some sets of modern women, it remains to be seen how well this model will succeed. Even today, in some primitive cultures, the presence of a father triples children’s survival rate. As a result, the safest bet for females is to partner long-term with males who are likely to stick around, protect them and their children, and improve their access to food, shelter, and other resources.

Melissa was smart to take her time and make sure Rob was a good catch. Her dream was a husband whom she loved, and who loved and worshiped her back. Her worst fear was a man who might be unfaithful, the way her father was to her mother. After the night at the dance club, she got a number of positive clues. Rob was taller, older, and appeared financially comfortable. In the grand, Stone Age scheme of things, he fit the bill, but it still wasn’t clear whether he was the long-term type.

C
HEMICAL
A
TTRACTION

If Melissa’s ancient brain circuitry was scanning for assets and protection, what was Rob’s brain looking for in a long-term partner? According to Buss and other scientists, something completely different. Worldwide, men prefer physically attractive wives, between ages twenty and forty, who are an average of two and a half years younger than they are. They also want potential long-term mates to have clear skin, bright eyes, full lips, shiny hair, and curvy, hourglass figures. The fact that these mate preferences hold true in every culture indicates that they’re part of men’s hardwired inheritance from their ancient forefathers. It wasn’t just that Rob had a thing for girls with shiny curls. Melissa’s hair triggered his ancient attraction wiring.

Why would these particular criteria top men’s lists? From a practical perspective, all of these traits, superficial as they may seem, are strong visual markers of fertility. Whether or not men know it consciously, their brains know that female fertility offers them the biggest reproductive payoff for
their
investment. With tens of millions of sperm, men are capable of producing an almost unlimited number of offspring as long as they can find enough fertile females to have sex with. As a result, their key task is to pair up with women who are likely to be fertile and reproduce. Pairing with infertile women would be a waste of their genetic futures. So, over millions of years, male brain wiring evolved to scan women for quick visual clues to their fertility. Age, of course, is one important factor; health is another. A high activity level, youthful gait, symmetrical physical features, smooth skin, lustrous hair, and lips plumped by estrogen are easily observable signs of age, fertility, and health. So it’s no wonder women are reaching for the plumping effects of collagen injections and the wrinkle smoothing of Botox.

Shape, too, is a remarkably good indicator of fertility—breast implants notwithstanding. Before puberty, males and females have very similar body shapes and waist-to-hip ratios. Once the reproductive hormones kick in, however, healthy females develop curvier shapes, with waists that are about one-third narrower than their hips. Women with that body type have more estrogen and become pregnant more easily and at a younger age than those with waists that are closer in size to their hips. A thin waist also gives an instant clue to a woman’s reproductive availability, since pregnancy radically alters her silhouette. Social reputation is often a factor in male assessment, since the most reproductively successful males also need to pick women who will mate only with them. Men want to ensure their paternity but also to be able to count on a woman’s mothering skills to make sure that their offspring thrive. If Melissa had immediately gone to bed with Rob or showed off to him about all the guys she had had, his Stone Age brain might have judged that she would be unfaithful or had a bad reputation. That she was affectionate on the dance floor and went home at a proper hour in a taxi showed him she was a high-quality lady with whom to mate long-term.

C
ALCULATING
P
OTENTIAL
D
ANGER

Rob left a message on her machine, and Melissa waited a few days before calling him back. And although they had kissed on the first date, she had no plans of going to bed with him until she knew more about him. He was incredibly funny and charming, and seemed to have his life in order, but she needed to be sure on a gut level that she could trust him. The brain’s anxiety circuits usually fire around strangers—her amygdala’s fear circuits were still turned on full force. A natural cautiousness toward strangers is part of the brain wiring of both males and females, but women in particular give early, careful scrutiny to a man’s likely level of commitment when looking for a mate.

Seduction and abandonment by males is an old ruse, going back to the beginning of our species; one study found that young college males admitted to depicting themselves as kinder, more sincere, and more trustworthy than they really are. Some anthropologists speculate that natural selection favored men who were good at deceiving women and getting them to agree to have sex. Females, as a result, had to get even better at spotting male lies and exaggerations—and the female brain is now well-adapted to this task. A study by the Stanford University psychologist Eleanor Maccoby showed, for example, that girls learn to tell the difference between reality and fairy tales or “just-pretend” play earlier than boys. By adulthood, modern females have fine-tuned their superior ability to read emotional nuance in tone of voice, eye gaze, and facial expressions.

As a result of this extra cautiousness, the typical female brain isn’t as ready to admit to being overwhelmed by infatuation or the sheer excitement of sexual behavior as is the male. Women do reach the same or a higher romantic end point, but they’re often slower to confess to being in love and more careful than males in the beginning weeks and months of a relationship. Male brains have a different neurological love wiring. Brain-imaging studies of women in love show more activity in many more areas, especially gut feelings, attention, and memory circuits, while men in love show more activity in high-level visual processing areas. These heightened visual connections may also explain why men tend to fall in love “at first sight” more easily than women.

Once a person is in love, the cautious, critical-thinking pathways in the brain shut down. Evolution may have made these in-love brain circuits to ensure we find a mate and then focus in exclusively on that one person, according to Helen Fisher, an anthropologist at Rutgers University. Not thinking too critically about the loved one’s faults would aid this process. In her study on being in love, more women than men said that their beloveds’ faults don’t matter much to them, and women scored higher on the test of passionate love.

T
HE
B
RAIN IN
L
OVE

Melissa and Rob were talking on the phone almost every night. Every Saturday they would meet in the park to take Rob’s dog for a walk, or at Melissa’s apartment to watch the dailies on her latest film. Rob was feeling stable in his job and had finally stopped talking about his former girlfriend, Ruth. This waning attachment to Ruth gave Melissa a clue that she wasn’t just a rebound and that he was ready to focus in on her exclusively. She had already, involuntarily, fallen in love with him but hadn’t told him yet. She began warming to his physical affection, allowing her sex drive to catch up with her love drive.

Finally, after three months, Melissa and Rob fell passionately into bed after a day lying in the sun at the park totally entranced by each other. The pair was tumbling into full-blown consummated love.

Falling in love is one of the most irrational behaviors or brain states imaginable for both men and women. The brain becomes “illogical” in the throes of new romance, literally blind to the shortcomings of the lover. It is an involuntary state. Passionately being in love or so-called infatuation-love is now a documented brain state. It shares brain circuits with states of obsession, mania, intoxication, thirst, and hunger. It is not an emotion, but it does intensify or decreases other emotions. The being-in-love circuits are primarily a motivation system, which is different from the brain’s sex drive area but overlaps with it. This fevered brain activity runs on hormones and neurochemicals such as dopamine, estrogen, oxytocin, and testosterone.

The brain circuits that are activated when we are in love match those of the drug addict desperately craving the next fix. The amygdala—the brain’s fear-alert system—and the anterior cingulate cortex—the brain’s worrying and critical thinking system—are turned way down when the love circuits are running full blast. Much the same thing happens when people take Ecstasy: the normal wariness humans have toward strangers is switched off and the love circuits are dialed up. So romantic love is a natural Ecstasy high. The classic symptoms of early love are also similar to the initial effects of drugs such as amphetamines, cocaine, and opiates like heroin, morphine, and OxyContin. These narcotics trigger the brain’s reward circuit, causing chemical releases and effects similar to those of romance. In fact, there’s some truth to the notion that people can become addicted to love. Romantic partners, especially in the first six months, crave the ecstatic feeling of being together and may feel helplessly dependent on each other. Studies of passionate love show this brain state lasts for roughly six to eight months. This is such an intense state that the beloved’s best interest, well-being, and survival become as important as or more important than one’s own.

During this early phase of love, Melissa was intensely memorizing every detail of Rob. When she had to go to L.A. for a week to show a piece of her new film project at a conference, both struggled with the separation. This was not just some fantasy; it was the pain of neurochemical withdrawal. During times of physical separation, when touching and caressing is impossible, a deep longing, almost a hunger, for the beloved can set in. Some people don’t even realize how bonded or in love they are until they feel this tugging at their heartstrings when the beloved is absent. We are used to thinking of this longing as only psychological, but it’s actually physical. The brain is virtually in a drug-withdrawal state. “Absence makes the heart grow fonder,” your mother would say as you were moaning in pain because
he
was away. I can remember the early days of dating my husband, when I already knew he was “the one” but he didn’t yet. During a brief separation he “decided” we should get married—thank goodness for dopamine and oxytocin withdrawal. His heartstrings finally got the attention of his very self-sufficient and independent male brain, as his friends and family will tell you.

During a separation, motivation for reunion can reach a fever pitch in the brain. Rob was so desperate in the middle of the week for physical contact with Melissa that he flew down to see her for a day. Once reunion takes place, all the components of the original loving bond can be reestablished by dopamine and oxytocin. Activities such as caressing, kissing, gazing, hugging, and orgasm can replenish the chemical bond of love and trust in the brain. The oxytocin-dopamine rush once again suppresses anxiety and skepticism and reinforces the love circuits in the brain.