The Male Brain Read online

  I must have been dimly aware of this long catalog of distinctive male behaviors when I first found out, twenty-one years ago, that the baby I was carrying had a Y chromosome. I immediately thought, Oh dear. What am I going to do with a boy? Up until that moment, I realized, I had unconsciously been thinking It’s a girl! and feeling confident that my own female life experiences could guide me in raising a daughter. I was right to be nervous. My lack of boy-smarts was about to matter more than I imagined. I now know from my twenty-five years of research and clinical work that both men and women have a deep misunderstanding of the biological and social instincts that drive the other sex. As women, we may love men, live with men, and bear sons, but we have yet to understand men and boys. They are more than their gender and sexuality, and yet it is intrinsic to who they are. And it further complicates matters that neither women nor men have a good sense of what the others’ brains or bodies are doing from one moment to the next. We are mostly oblivious to the underlying work performed by different genes, neurochemicals, and hormones.

  Our understanding of essential gender differences is crucial because biology does not tell the whole story. While the distinction between boy and girl brains begins biologically, recent research shows that this is only the beginning. The brain’s architecture is not set in stone at birth or by the end of childhood, as was once believed, but continues to change throughout life. Rather than being immutable, our brains are much more plastic and changeable than scientists believed a decade ago. The human brain is also the most talented learning machine we know. So our culture and how we are taught to behave play a big role in shaping and reshaping our brains. If a boy is raised to “be a man,” then by the time he becomes an adult, his brain’s architecture and circuitry, already predisposed that way, are further contoured for “manhood.”

  Once he reaches manhood, he will likely find himself pondering an age-old question: What do women want? While no one has a definitive answer to that question, men do know what women and society in general want and expect from them. Men must be strong, brave, and independent. They grow up with the pressure to suppress their fear and pain, to hide their softer emotions, to stand confidently in the face of challenge. New research shows that their brain circuits will architecturally change to reflect this emotional suppression. Although they crave closeness and cuddling as much or perhaps even more than women, if they show these desires, they are misjudged as soft or weak by other men and by women, too.

  We humans are first and foremost social creatures, with brains that quickly learn to perform in socially acceptable ways. By adulthood, most men and women have learned to behave in a gender-appropriate manner. But how much of this gendered behavior is innate and how much is learned? Are the miscommunications between men and women biologically based? This book aims to answer these questions. And the answers may surprise you. If men and women, parents and teachers, start out with a deeper understanding of the male brain, how it forms, how it is shaped in boyhood, and the way it comes to see reality during and after the teen years, we can create more realistic expectations for boys and men. Gaining a deeper understanding of biological gender differences can also help to dispel the simplified and negative stereotypes of masculinity that both women and men have come to accept.

  This book provides a behind-the-scenes brain’s-eye view of little boys, tumultuous teens, men on the mating hunt, fathers, and grandfathers. As I take readers through the phases of the male brain’s life, my hope is that men will gain a greater understanding of their deepest drives and women will catch a glimpse of the world through male-colored glasses. We are entering an era, finally, when both men and women can begin to understand their distinct biology and how it affects their lives. If we know how a biological brain state is guiding our impulses, we can choose how to act, or to not act, rather than merely following our compulsions. If you’re a man, this knowledge can not only help you understand and harness your unique male brain power, but it can also help you understand your sons, your father, and other men in your life. If you’re a woman, this book will help you interpret and comprehend the intricacies of the male brain. With that new information, you can help your sons and husbands to be truer to their nature and feel more compassionate toward your father.

  Over the years, as I have been writing this book, I have come to see the men I love most—my son, my husband, my brother, and my father—in a new light. It is my hope that this book will help the male brain to be seen and understood as the fine-tuned and complex instrument that it actually is.

  ONE

  The Boy Brain

  DAVID RACED past the swing set and zoomed around the toolshed in the backyard with his preschool buddies Matt and Craig hot on his heels. Determined to maintain his lead, he took a shortcut through the sandbox, sending sand and shovels flying as he made a beeline for the coveted Big Wheel tricycle. Matt pushed Craig aside and dived for the wheeled wonder, but David was already sliding into the driver’s seat. With pedals churning, David screeched off down the sidewalk and into the driveway, where he victoriously spun doughnut after doughnut.

  Disappointed but not to be outdone, Matt and Craig headed for the open garage to see what else they could find to ride. Craig spotted it first: a large plastic trash can. “Let’s use this!” he shouted. And without another word, the boys were running headlong for the hill in the backyard, dragging the can behind them. “C’mon. Gimme a push!” Craig commanded as he slid into the can. “Harder!” he said, as Matt’s first shove barely budged it. Matt rammed the can with his shoulder as hard as he could, and the green vehicle tumbled down the hill with Craig inside whooping and hollering.

  You don’t have to study brain science to know that little boys are all about action and adventure. Go to a playground and you’ll see boys like David and his friends in perpetual motion. Boys are programmed to move, make things move, and watch things move. Scientists used to think this stereotypical boy behavior was the result of socialization, but we now know that the greater motivation for movement is biologically wired into the male brain.

  If you watched the fetal development of a male and a female brain with a miniature time-lapse brain scanner, you’d see these critical movement circuits being laid down from the blueprint of their genes and sex hormones. Scientists agree that when cells in various areas of the male and female brains are stimulated by hormones like testosterone and estrogen, they turn on and off different genes. For a boy, the genes that turn on will trigger the urge to track and chase moving objects, hit targets, test his own strength, and play at fighting off enemies.

  David and his friends weren’t taught to be action-oriented; they were following their biological impulses. David’s mother said that his love affair with movement was obvious from day one. “When I put him in his bassinet, I thought he’d cry and look beseechingly at me the way Grace did when she was a baby,” she said. “But as soon as he spotted the moving mobile, he forgot I was there.”

  David was only twenty-four hours old, and without encouragement or instruction from anyone, he stared at the rotating triangles and squares on the mobile and seemed to find them fascinating. Nobody taught David to follow the movements of the dangling triangles and squares with his eyes. He just did it. A boy’s superior ability to track moving objects isn’t the result of being conditioned by his environment. It’s the result of having a male brain. Every brain is either male or female and, while they are mostly alike, scientists have discovered some profound differences. Certain behaviors and skills are wired and programmed innately in boys’ brains, while others are wired innately in girls’. Scientists have even found that male-specific neurons may be directly linked to stereotypical male behaviors like roughhousing. And studies show that from an early age, boys are interested in different activities than girls. These differences are reinforced by culture and upbringing, but they begin in the brain.

  WHAT MAKES A BOY A BOY?

  I met David’s mother, Jessica, a few months after he was born. Her daughter, Gr
ace, was three years old, and Jessica and her husband, Paul, were thrilled to have a beautiful baby boy. But Jessica was worried because things weren’t going quite as smoothly with David as they had with Grace. Jessica said, “He’s sweet and cuddly one minute, and the next minute he’s squirming out of my arms. If I don’t put him down, he shrieks like I’m killing him.”

  Jessica was afraid that David might be hyperactive. But her pediatrician told her David was just fine and developing normally. Researchers at Harvard found that baby boys get emotionally worked up faster than girls, and once they’re upset, they’re harder to soothe. So, early on, parents spend more time trying to dial down their sons’ emotions than their daughters’. She said, “Grace was easier to calm. David keeps us constantly on our toes!”

  Jessica also told me that David didn’t make eye contact with her the way Grace did when she was a baby. She said that he’d only look at her for a couple of seconds and then go right back to staring at the mobile. I couldn’t help but smile, because I had this same concern with my own son. At that time, psychologists believed the key to developing a bond with your baby was what they called mutual gazing—looking into each other’s eyes. Whereas that’s true for baby girls, it turns out that baby boys bond without as much mutual gazing. And unlike girls, who are inclined to look long and hard at faces, boys’ visual circuits pay more attention to movement, geometric shapes, and the edges and angles of objects from the get-go.

  I said to Jessica, “By the time they’re six months old, baby girls are looking at faces longer and making eye contact with just about everyone. But baby boys are looking away from faces and breaking eye contact much more than girls. There’s nothing wrong with David. His brain just doesn’t find eyes and faces as interesting as toy airplanes and other moving objects.”

  David’s male brain was prompting him to visually explore animated objects. We now know that genes on the Y chromosome are the reason. Like other boys, David’s fascination with movement was the result of circuitry that started to form in his brain just eight weeks after he was conceived. During fetal development, David’s brain was built in two stages. First, during weeks eight to eighteen, testosterone from his tiny testicles masculinized his body and brain, forming the brain circuits that control male behaviors. As his brain was marinating in testosterone, this hormone began to make some of his brain circuits grow and to make others wither and die.

  Next, during the remaining months of pregnancy another hormone, MIS, or Müllerian inhibiting substance, joined with testosterone and defeminized David’s brain and body. They suppressed his brain circuits for female-type behaviors and killed off the female reproductive organs. His male reproductive organs, the penis and testicles, grew larger. Then, together with testosterone, MIS may have helped form David’s larger male brain circuits for exploratory behavior, muscular and motor control, spatial skills, and rough play. Scientists discovered that when they bred male mice to lack the MIS hormone, they did not develop male-typical exploratory behavior. Instead, they behaved and played more like females. The female brain circuits that make a girl a girl are laid down and develop without the effects of testosterone or MIS.

  After I shared this information with Jessica, she raised her eyebrows and asked, “Are you saying that if Grace’s brain had been exposed to these male hormones when I was pregnant, she’d act more like David?”

  “That’s right,” I said, smiling as her face lit up with recognition. It’s always rewarding to me when I see this kind of relief on a mother’s face. Suddenly, instead of thinking that she’s doing something wrong or that there’s something wrong with her child, she can relax and begin to appreciate her son’s maleness.

  She said, “It’s just so different with David. He’s so much more active than Grace was, even at this age. But he can be the very essence of sweetness, too.

  “The other day when I was having a hard time getting him down for his nap, Paul took him and played with him on our bed, hoping he’d calm down. I had my doubts about whether it would work, but when I peeked in to check on them a little later, David was lying with his tiny hand inside of Paul’s big one, and they were both fast asleep.”

  From birth until a boy is a year old, a period that scientists call infantile-puberty, his brain is being marinated in the same high levels of testosterone as in an adult man. And it’s this testosterone that helps stimulate a boy’s muscles to grow larger and improves his motor skills, preparing him for rough-and-tumble play. After the year of infantile-puberty, a boy’s testosterone drops, but his MIS hormone remains high. Scientists call this period, from age one to ten, the juvenile pause. They believe that the MIS hormone may form and fuel his male-specific brain circuits during this ten-year period, increasing his exploratory behavior and rough play. This meant it wouldn’t be long before Jessica would have more reason to worry as David started testing his limits, as I well remember with my own son.

  When he was a toddler and we were out walking on Baker Beach in San Francisco, he took off running after a sandpiper toward the water. I shouted and waved my arms like a madwoman to signal danger. He completely ignored me. I had to run after him and grab his shoulders to pull him back from the surf, just as a huge wave was rolling in. That was the first day in what would be years of his ignoring my signals of danger—stop, don’t do that—requiring me to keep a firm hold on him.

  Researchers have found that by the time a boy is seven months old, he can tell by his mother’s face when she’s angry or afraid. But by the time he’s twelve months old, he’s built up an immunity to her expressions and can easily ignore them. For girls, the opposite happens. A subtle expression of fear on Jessica’s face would stop Grace in her tracks. But not David.

  By the age of one, David seemed oblivious to the look of warning on Jessica’s face. Researchers asked mothers of one-year-old boys and girls to participate in an experiment in which an interesting but forbidden toy was placed on a small table in the room with them. Each mother was told to signal fear and danger with only her facial expressions, indicating that her child should not touch it. Most of the girls heeded their mother’s facial warning, but the boys seemed not to care, acting like they were magnetically pulled toward the forbidden object. Their young male brains may have been more driven than the girls’ by the thrill and reward of grabbing the desired object, even at the risk of punishment. And this also happens with fathers. In another study, with dads and their one-year-olds, the boys tried to reach forbidden objects more often than the girls. The fathers had to give twice as many verbal warnings to their sons as to their daughters. And researchers found that by the age of twenty-seven months, boys more often than girls will go behind their parents’ backs to take risks and break rules. By this age, the urge to pursue and grab items that are off-limits can become a hair-raising game of hide-and-seek—with parents hiding the danger their sons will inevitably seek.

  When David was three and a half, Jessica told me that he never ceased to amaze her, both for better and for worse. “He picks me flowers, tells me he loves me, and showers me with kisses and hugs. But when he gets the urge to do something, the rules we’ve taught him vanish from his mind.” She told me that David and his friend Craig were in the bathroom washing up for dinner when she heard Craig yell, “Stop it, David. I’m peeing.” Then she heard the distinct sound of the hair dryer. Danger flashed through Jessica’s brain. Racing down the hall, she flung open the bathroom door just in time to get a splash of urine on her legs. David had turned the blow-dryer on his friend’s stream—just to see what would happen. But being sprayed with urine didn’t upset her nearly as much as David’s disregarding the “no electrical appliances without adult supervision” rule. For the next couple years, she had to keep all electrical appliances well out of David’s reach. But, she told me with a slight blush, “There’s one thing I can’t keep out of his reach, even in public.”

  PLAYING WITH HIS PENIS

  David thought nothing of grabbing and playing with his penis—any
time, anywhere. A boy’s public relationship with his penis is something that has made many mothers wince, including me. But the male brain’s reward center gets such a huge surge of pleasure from penis stimulation that it’s nearly impossible for boys to resist, no matter what their parents threaten. So rather than trying to stop David, I suggested Jessica start teaching him to explore this compelling pleasure in the privacy of his room.

  A few weeks after Jessica started trying to get David to play with his penis in “privacy,” the family went on vacation. As they were walking down the hallway in their hotel, David saw a sign hanging on the doorknob of the room next-door and asked, “Mom, what does P-R-I-V-A-C-Y say?” When Jessica said the word out loud for him, he said, “Oh, that man must be doing his privacy in there.” From then on, he’d refer to playing with his penis as “doing my privacy.”

  BOYS’ TOYS

  Later that year, when David came into the office with Jessica, I handed him a lavender toy car from an assortment I had in a shoe-box. He frowned as he said, “That’s a girl car.” Tossing the car back into the box, he grabbed the bright red car with black racing stripes, saying, “This is a boy one!” Researchers have found that boys and girls both prefer the toys of their own sex, but girls will play with boys’ toys, while boys—by the age of four—reject girl toys and even toys that are “girl colors” like pink.