The Female Brain

“More than ninety-nine percent  of male and female  genetic  coding  is exactly the same. Out of the 30,000 genes in the human  genome, the variation between the sexes is small. But those few differences  influence every single cell in our bodies—from the nerves that register pleasure and pain to the neurons that transmit perception, thoughts,  feelings and emotions.”
“Just as women have an eight-lane  superhighway for processing  emotion while men  have a small country  road, men  have Chicago’s O’Hare Airport as a hub for processing  thoughts  about sex whereas  women have the airfield nearby that lands small and private planes. That probably  explains  why  eighty-five percent  of twenty-  to thirty-year-old  males think about sex every fifty two seconds  and women think about it once  a day—or up to every three or four hours on their most fertile days. This makes  for interesting interactions between
the sexes.”

Louann Brizendine

As a medical student,  Louann  Brizendine was aware  of conclusive stud- ies done around the world  showing  that  women  suffer from depression at a ratio  of 2:1 compared to men. Going through college at the peak of the feminist movement,  along with many others  she believed this was the result of the “patriarchal oppression of women.” But it came to her notice that,  up until puberty, depression  rates between  boys and girls are the same. Could  the hormonal changes to girls in their early teenage years, she won- dered, make them suddenly  more prone  to getting depressed?
Later, as a psychiatrist, Brizendine worked  with women  suffering from the extremes  of premenstrual syndrome,  and was struck  by the extent  to which the female brain  is shaped  by dramatic changes in hormonal chemistry,  driving a woman’s  behavior  and creating  her reality. In 1994,  Brizendine established the Women’s Mood  and Hormone Clinic in San Francisco,  one of the first of its type in the world.  The Female Brain, the culmination of her 20 years of practice  as a neuropsychiatrist, pulls together  her own research  and the latest findings from a range of disciplines. Contrasting the relative stability  of male hormonal brain  states with those of the female, which involve an often com- plex cocktail  of chemicals and change dramatically from girlhood  to adoles- cence, early adulthood, motherhood, and menopause, the book  brilliantly shows why women’s brain  states and chemistry  merit independent research, and why generalities  about  human  behavior  usually relate to male behavior.
The Female Brain includes fascinating  chapters  on the female brain  in love, the neurobiology of sex, the “mommy brain” (how a woman’s  thinking changes according  to altered  brain  chemistry  in pregnancy), and the mature female brain,  post-menopause. We focus here on some of Brizendine’s insights regarding  the infant  and pubescent  female brain.

Basic differences
Even taking  into account  differences in body size, Brizendine notes, the male brain  is about  9 percent  larger than  the female. This fact was once interpreted as meaning  that  women  were not as smart  as men. In fact, women  and men have the same number  of brain  cells, but women’s are more tightly packed into their skull.
In the areas of the brain  dealing with language  and hearing,  women  have a full 11 percent  more neurons  than  men, and the part  of the brain  associated with memory,  the hippocampus, is also larger in women.  The circuitry  for observing  emotion  on other  people’s faces is again larger compared to the male. In relation  to speech, emotional intelligence,  and the ability to store rich memory,  therefore,  women  have a natural advantage.
Men, on the other  hand,  have more processors  in the amygdala,  a part  of the brain  regulating  fear and aggression.  This perhaps  explains  why males are more likely to anger quickly and take violent action  in response  to immediate physical danger.  Women’s brains  also evolved to deal with possibly life- threatening situations, but in a different  way. The female brain  experiences greater  stress over the same event as a man’s, and this stress is a way of taking account  of all possible risks to her children  or family unit. This is why, Brizendine suggests, a modern  woman  can view some unpaid  bills as catas- trophic, as they seem a threat  to the family’s very survival.
Brain scanning  and imaging technologies  now allow us to see the work- ings of the brain  in real time. They show the brain  lighting up in different places depending  on whether  we are in love, looking  at faces, solving a prob- lem, speaking,  or experiencing  anxiety,  and these hot spots differ between men’s and women’s brains.  Women  actually  use different  parts  of the brain and different  circuits than  men to accomplish  the same tasks, including  solving problems,  processing  language,  and generally experiencing  the world.
One other  basic brain  difference is noteworthy. Studies have shown  that men think  about  sex on average every 52 seconds, while for women it is once a day. As the part  of the brain  where sexual thought and behavior  is generated is two and a half times larger in the male, this is not surprising.

The baby  female brain
Until they are eight weeks old, the brains  of male and female foetuses look the same—“female is nature’s  default  setting,” Brizendine observes. At about  eight weeks, a male foetus’s brain  is flooded with testosterone, which kills off the cells relating  to communication and helps to grow cells relating  to sex and aggression.  Biochemically,  the male brain  is then significantly different  from a female one, and by the time the first half of the pregnancy  is over, the differ- ences between  male and female brains  are mostly set.
A female baby comes into the world  wired to notice faces and hear vocal tones better.  In the first three months  of her life a baby girl’s abilities at “mutual gazing”  and eye contact  grow by 400 percent.  In the same period, these abilities do not grow at all in boys.
It is well known  that  girls usually begin speaking  some time before boys, thanks  to the better-developed language  circuitry  of their brains.  This contin- ues into adulthood, with women  speaking  on average 20,000 words  a day and men averaging  only around 7,000.  (As Brizendine remarks, this higher ability “wasn’t  always appreciated,” with some cultures  locking up a woman  or putting  a clamp on her tongue  to stop the chatter.)

One other  important difference in infancy is that  baby girls are more sen- sitive to the state of their mother’s  nervous  system. It is important that  infant girls do not have mothers  who are stressed out, as when the girl grows up to have children  of her own her ability to be nurturing will be reduced.  However, armed  with this knowledge,  it is possible to break  the cycle of mother–infant stress.

The teen  girl’s brain
At puberty, a girl’s thinking  and behavior  change according  to the fluctuating levels of estrogen  (one of the “feel-good” hormones), progesterone (“the brain’s valium”), and cortisol  (the stress hormone) in her brain.  Other  impor- tant  hormones produced are oxytocin  (which makes us want  to bond,  love, and connect  with others)  and dopamine (which stimulates  the brain’s pleasure centers).
The effect of these chemicals is to give a teenage girl a great need for and pleasure  in gossiping, shopping,  exchanging  secrets, and experimenting with clothing  and hair styles—anything that  involves connecting  and communicat- ing. Teenage girls are always on the phone  because they actually  need to com- municate  to reduce their stress levels. Their squeals of delight at seeing friends, and the corresponding panic at being grounded, are also part  of these changes. The dopamine and oxytocin  rush that  girls experience  is “the
biggest, fattest  neurological  reward  you can get outside  of an orgasm,” Brizendine remarks.
Why exactly does the loss of a friendship  feel so catastrophic to a teen girl, and why is her social group  so important to her? Physiologically she is reaching  the optimum age for child rearing,  and in evolutionary terms she knows  that  a close-knit  group  is good protection, since if she has a small child with her she is not able to attack  or run away as a man can. (The concept  of “fight or flight” in response  to danger  is an observation of men rather  than women.)  Close social bonds  actually  alter the female brain  in a highly positive way, so that  any loss of those relationships triggers a hormonal change that strengthens the feelings of abandonment or loss. The intensity  of female pubescent  friendships  therefore  also has a biochemical  basis.
The teenage girl’s confidence and ability to deal with stress also change according  to the time of the month,  and Brizendine has treated  many “prob- lem” girls who experience  higher than  average hormonal changes. The most brash  and aggressive girls often have high levels of androgens, the hormones associated  with aggression.  At normal  levels, fluctuations in androgens can cause a girl to be more focused on power,  whether  within  the peer group  or over boys.
Incidentally,  why do teenage boys often become brooding and monosyllabic?  The testosterone that  marinates their brains  not only drives them to “compelling  masturbatory frenzies,”  but also reduces their wish to talk or socialize if it does not involve girls or sport.
Overall,  in the teen years the differing hormonal effects on the brain cause males and females to go off in different  directions—boys gain self-esteem through independence from others,  while females gain it through the closeness of their social bonds.

Final comments
Brizendine began her career in psychiatric  work  and later moved to neurology. This perspective  has made her less willing to speculate  on psychological  or sociological ideas that  have little to do with how the brain  actually  works; though  clearly a feminist, she warns  that political  correctness  has no role in understanding behavior. Yes, we may be able to alter our cultural  attitudes or policies to make a better  world,  but first we must understand the facts about how brain  biology—so  different  between  men and women—shapes behavior.
Brizendine weighs into the debate  sparked  by Harvard University president Lawrence Summers, who said that  the differences in achievement  between men and women  in mathematics and the sciences was due to natural brain  differ- ences between the sexes. She notes that  until puberty, boys and girls are exactly the same in mathematical or scientific achievement.  However,  the testosterone that  floods the male brain  makes boys extremely competitive  but also more willing to spend many hours  studying  alone or working  on their computers. With the teenage girl’s flood of estrogen,  in contrast, a female becomes a lot more interested  in social bonding  and her emotional life, and as a consequence is unlikely to sit for hours  alone pondering mathematical puzzles or battling  to top the class. Even as adults  women  are compelled  by their brain  chemistry  to want  to communicate and connect,  and this favors them less for the sort of solitary  work  often required  by mathematical, scientific, or engineering careers. Brizendine’s theory in a nutshell:  It is not lack of aptitude that  makes women stay out of these fields, but brain-driven attitudes to the work  involved.
Yet Brizendine says, “Biology powerfully  affects, but does not lock in our reality.”  That  is, if we know  about  the physiological  or genetic forces that shape us, we are able to take account  of them. The availability  of estrogen  in pill form and the fact that  we can replace hormones (The Female Brain includes a long appendix on hormone replacement therapy)  means that
women  can now have more control  over their daily experience  of reality; per- haps such treatments will end up having as great an impact  on women’s lives and destinies as the contraceptive pill did.
Subtracting the copious  appendices  and notes, The Female Brain is only 200 pages long. As an enjoyable and often witty popular synthesis of the latest research  on the subject, it is likely to be read for many years to come. With many additional insights into the male brain,  this is a book  for everyone.

Louann Brizendine
Brizendine’s first degree was in neurobiology from  the University  of California, Berkeley  (1972–6),  followed by medicine  at Yale University,  and psychiatry  at Harvard  Medical School (1982–5).
After  a stint teaching at Harvard,  in 1988  she accepted a post at the Langley  Porter Psychiatric Institute at the University  of California, San Francisco, where in 1994  her Women’s Mood  and Hormone Clinic was estab- lished. She continues  to combine  research work  with  clinical practice and teaching, focusing  on the effects on mood,  energy, sexual function, and hormonal influences on the brain.