The Female Brain (10 page)

Boys and girls have the same risk of depression, before the hormones of puberty. But by age fifteen, girls are twice as likely to suffer from depression. Genetics may also play a role in female depression. In certain families with high depression rates, for example, researchers have found a mutation in a gene called CREB-1 that puts teenage females—but not males—at higher risk for clinical depression. Shana’s mother and grandmother had had serious depressions in their teens, and a female cousin had committed suicide. These facts put her at serious risk. Shana had a true clinical depression. I started her on an antidepressant, stayed in close contact, and did weekly cognitive therapy. Within four to six weeks she was able to concentrate again, take her final exams, and stop obsessing over both Mike and her weight.

T
HE
B
IOLOGY OF
M
EAN
G
IRLS

Hormonal surges can turn nice girls mean at the drop of an egg, and so can sexual competition, which is strong—and pivotal—among teenage girls. This competition, however, plays out with a different set of rules than does that among teen boys. Girls are driven to gather in cliques, but there is another side, in which these cliques are at war. Teen girls, we know, can be devastatingly mean. When females are competing with other females, they often use more subtle tools, such as spreading rumors to undermine a rival. This way, they can cover their tracks—“I wasn’t trying to be mean. I’m sorry.” Such tactics lessen the risk of destroying the bond that the teen girl brain sees as essential to survival. But also essential to survival is sexual competition.

I can remember when I was in seventh grade, there was one girl who was beautiful, and the other girls were very jealous because she got so much attention from the boys. She was also shy, so others assumed she was a snob. One day the not as pretty girl who sat directly behind her in a class took a wad of bubble gum out of her mouth and stuck it in the pretty girl’s hair. Unknowingly, the pretty girl began to twist the gum into such a mess that the only way to get it out was to cut off her seductive locks. The queen of mean who put the gum in this girl’s hair felt triumphant. Her biological imperative to compete for sexual attractiveness had a momentary victory.

The hormones usually associated with aggression in both males and females are androgens. They begin to rise early in puberty and continue until they peak at age nineteen in females and twenty-one in males. The three main androgens that women make are testosterone, DHEA, and androstenedione (andro-steen-DIE-own). In a study at the University of Utah, the most in-your-face aggressive teenage girls were found to have high levels of the androgen androstenedione. Acne is a good clue that your teen’s androgen levels are high. Girls with high levels of testosterone and DHEA also tend to have sexual intercourse earlier. By the time I saw Shana at age fifteen, she not only had acne and fully developed breasts but had been having sex for the past year.

Aggressive impulses can fluctuate with the hormones of the menstrual cycle. During some weeks of the cycle, the teen girl will be more interested in social connection. During other weeks, she’ll be more interested in power—over boys and other girls. This association implies that the higher amounts of androgens made by the ovaries during weeks two and three increase aggression levels in women and teens. Less empathy, social connection, and affiliation have been associated with higher androgen levels in both sexes. We can’t know for sure, but Shana’s higher androgen levels on certain weeks of her cycle may have been triggering her aggressive outbursts.

Not only is aggression reduced when androgen levels are low but sex drive is decreased, too. Teens taking oral contraceptives have reduced aggression and sex drive because the contraceptive suppresses the ovaries, so they make less androgen. Although both men and women make testosterone, men make more than ten times as much—meaning that their sex drive is much greater than women’s. Scientists know that it is probably not just androgens that increase aggressive spirit and ambition in women but estrogen, too. In the same study at the University of Utah, women who were the most outspoken and had the highest self-regard also had the highest levels of estrogen, testosterone, and androstenedione. They also ranked themselves above how their peers ranked them. And these young women were routinely rated by others as the most boastful.

Of course, a hormone alone does not cause a behavior. Hormones merely raise the likelihood that under certain circumstances a behavior will occur. And just as there is no one seat of aggression in the brain, there is no one hormone of aggression. But achieving success and attaining power in the world requires some aggression for both sexes. These hormones change teens’ reality and perceptions of themselves as sexual, assertive, and independent beings in the world.

During the teen years a girl’s brain circuits go through massive growth and pruning. It’s as if she is given a whole new set of extension cords and needs to figure out which one to plug into which outlet. The full power of her female brain circuits can now start to be manifested. And where will they push her? Right into the arms of a man.

THREE

Love and Trust

M
ELISSA, A BRASSY
San Francisco film producer, really wanted to fall in love. Her career was finally chugging along at a steady pace, and at age thirty-two, she was ready to move into the next phase of her life. She now wanted a family and the continuity of a relationship with a man who would stick by her for more than a few sexually charged months. The only problem was that she couldn’t seem to connect with the right one. She would go on countless dates through setups, or with men she met on the Internet, but none was touching off the flurry of butterflies in her stomach or that intense, irrational need to be around him all the time.

One night her best friend, Leslie, called and asked Melissa to go salsa dancing. But Melissa wasn’t in the mood. She wanted to stay home, relax, and watch TV, but Leslie was relentless, so Melissa acquiesced. She tousled her curly hair to look sexy, put on a swirly skirt, her new red suede heels, and bee sting red lipstick, which made her mouth pop out. She grabbed a taxi over to the dance club.

Leslie was already inside drinking a margarita when Melissa arrived. As they were getting loose to hit the dance floor, Melissa saw a tall, handsome man with a sculpted face, olive skin, and a shock of nearly black hair across the room. “Wow, he’s gorgeous,” she said.

She turned back to Leslie and whispered for her to glance over at the man, but it was too late. He was already walking toward them. Melissa was locked in gaze with this stranger. A wave of energy shot up her back. It was the feeling she hadn’t experienced in all the months of her bad dates. There was something vaguely familiar about him. “Hmm, who
is
that?” she whispered under her breath to Leslie, as her brain’s cortex scanned her memory banks. No match was found, but all her attention circuits were now on “mating alert status.” Is he here alone or with someone? she wondered. She looked around for the one of the gorgeous women who always seem to be attached to these perfect-looking guys but saw no one. And he was still walking toward her.

The closer he got, the more unfocused Melissa became on her friend’s story. She grabbed her drink tightly. Her eyes and attention were riveted on him, taking in every detail—his leather Armani shoes, his sexy black cords, and no wedding ring on his left finger. Everything else dropped into the background as her brain honed to make contact. She felt like she was falling in love. The mating impulse had taken over.

“Hi, I’m Rob,” he said, leaning against the bar nervously. His voice was pure velvet. “Have we met before?” Melissa was unable to hear his words. She could only bask in the feel of him, his earthy smell, and his devilish green eyes.

The dance of romance had begun, and its choreographer was not her friend or a matchmaker. It was the biology of Melissa’s brain. We know that the symmetry of physiques and faces that entrance us, the moves that seduce us, and the heart-pounding passion of attraction are all hardwired into our brains’ love drive by evolution. Short-and long-term “chemistry” between two people may seem accidental, but the reality is that our brains are preprogrammed to know better. They subtly but firmly steer us toward partners who can boost our odds in the sweepstakes of human reproduction.

Melissa’s brain is beginning to imprint Rob. Her hormones are surging. As he tells her that he is a marketing consultant who lives in a loft in Potrero Hill and musters up the nerve to ask her to dance, her brain, faster than a supercomputer, calculates the qualities that might put him in the running as a mating partner. Already some green light is flashing that he’s a good one, and
wham
, hot, knee-buckling waves of attraction and desire are flooding her body with a heady rush of dopamine—sparking euphoria and excitement. Her brain has also ordered her a shot of testosterone, the hormone that stokes sexual desire.

As Rob speaks, he is also sizing up Melissa at a closer view. If his calculations come out positive, he’ll get a neurochemical jolt, too, prodding him to try to hook up with her. With their love circuits mutually revved up, the two move onto the dance floor and spend the next few hours locked in sweaty salsa rhythms. At 2:00
A.M
., the music slows down and the club begins to empty. Leslie has gone home hours earlier. Standing on the corner, Melissa says that she has to go and flirtatiously turns on her high heels. “Wait,” Rob says. “I don’t have your number. I want to see you again.” “Google me and you’ll find me,” she replies, smiling and jumping into a cab. Now the chase begins.

For men and women, the initial calculations about romance are unconscious, and they’re very different. In short-term couplings, for example, men are chasers and women are choosers. That’s not sex stereotyping. It’s our inheritance from ancestors who learned, over millions of years, how to propagate their genes. As Darwin noted, males of all species are made for wooing females, and females typically choose among their suitors. This is the brain architecture of love, engineered by the reproductive winners in evolution. Even the shapes, faces, smells, and ages of the mates we choose are influenced by patterns set millennia ago.

The truth is, we’re much more predictable than we think. Over the course of our evolution as a species, our brains have learned how to spot the healthiest mates, those most likely to give us children, and those whose resources and commitment can help our offspring survive. The lessons that early men and women learned are deeply encoded in our modern brains as neurological love circuits. They are present from the moment we’re born and activated at puberty by fast-acting cocktails of neurochemicals.

It’s an elegant system. Our brains size up a potential partner, and if he fits our ancestral wish list, we get a jolt of chemicals that dizzy us with a rush of laser-focused attraction. Call it love or infatuation. It’s the first step down an ancient pair-bonding path. The gates have opened to the courtship-mating-parenting brain program. Melissa may not have wanted to meet anyone that night, but her brain had other plans that are deep and primitive. When it saw Rob across the room, a signal went off for mating and long-term attachment, and she was lucky that his brain felt the same way. Each of them will come up against anxiety, threats, and mind-numbing joys, over which they have little control because now biology is building their future together.

M
IND-SET ON
M
ATING

As Melissa struts along the city streets, sips her latte, or cruises the Internet for potential dates while she’s waiting for Rob to locate her number on her website—she did tell him the name of her latest film, so if he is smart, he’ll find her—it’s not easy to believe that what’s inside her cranium is a Stone Age brain. But that’s the case, according to scientists who study the mate-attraction engineering of the human mind. We spent more than 99 percent of the millions of years it took human beings to evolve living in primitive conditions. As a result, the theory goes, our brains developed to solve the kinds of problems that those early human ancestors encountered. The most important challenge they faced was reproduction. It wasn’t just a matter of having children. It was making sure those children lived long enough to propagate their genes. Early people whose mating choices produced more surviving offspring succeeded in passing their genes on. Their specific brain systems for courtship attraction were more successful. Ancestors who made the wrong reproductive moves left no imprint on the future of the species. As a result, the brain wiring of the best Stone Age reproducers became the standard-issue circuitry of modern humans. This courtship circuitry is what is commonly known as “falling in love.” We may think we’re a lot more sophisticated than Fred or Wilma Flintstone, but our basic mental outlook and equipment are the same.