Brain Fitness for Women. Sondra Kornblatt
are better at activities requiring the focus of one side or the other.
But several authors have called these studies on the carpet. They scientifically challenged whether (1) our advanced instruments tell as much as we’d like, (2) the assumptions they tell are true, and (3) the studies are large enough for their statistics to have veracity.
For instance, when looking at the corpus callosum, some studies found that it is the same size in men and women, and other studies found that it's bigger in men. Studies also question whether having a larger right hemisphere means increased learning or more difficulty learning. And while the anterior cingulate cortex is the part of the brain that generates worry, this part is also involved with a wide variety of cognitive, motor, and emotional tasks, such as decision-making; so it makes as much sense to say that a larger anterior cingulate cortex means women think better than men, instead of that women worry more.
Cordelia Fine, author of Delusions of Gender, says that these studies are looking at the brain through traditional assumptions. It's just like 1915, she says, when studies “proved” that women couldn't judge political initiatives and couldn't vote, all because they had smaller upper spinal cords. The results of these studies are similarly biased because of what she calls neurosexism. 17
We are starting to get larger and more valid studies about gender and the brain, which we hope will clarify the issue. And we know some consistent male-female brain differences in animals and humans from previous decades of study.
What Do We really Know?
Boys and girls' brains are different at birth, but the differences are much smaller than we think, says Lise Eliot, PhD, in Pink Brain, Blue Brain: How Small Differences Grow Into Troublesome Gaps—And What We Can Do About It.18
In fact, before the eighth week of pregnancy, there is no male brain at all—everyone starts as a female. Around the eighth week, male embryos (meaning embryos with XY chromosomes) get a surge of testosterone. The testosterone changes the brain's original plan to create a uterus and ovaries in the female with XX chromosomes; the male embryo develops a penis and testicles instead.
Only a few physical pre-adolescent brain differences have been reliably proven to exist:
Boys’ brains are larger than girls’ brains. (This difference used to support the idea that men were smarter, but when you consider the brains of elephants, the logic fades. Larger brains are needed for larger muscles and to process more sensations.19)
Girls’ brains finish growing about one to two years earlier than boys’ brains. (Hormonal differences are key in this growth difference.)
Parts of the hypothalamus are different. The hypothalamus controls basic body cycles and is connected to the pituitary (or “master hormone”) gland. The areas of the hypothalamus that are different in males and females control circadian rhythms and reproduction.
There may be some subtle differences in boys and girls' sensory processing, language circuits, and frontal-lobe development, but overall, boys’ brains and girls’ brains are remarkably similar.
So what creates more gender-typical behavior? How babies are treated, say both Eliot and Fine. Our wonderfully plastic brains respond to gender-specific atmospheres. For example, if you believe you're better at math, the area of your brain that does math work will be larger. Even intentionally unbiased child-rearing practices have some sex stereotyping, according to Fine. Add Disney movies and sports stars to the mix, and it's a challenge to separate and study the natural brain from the nurtured one.
Hormones, such as testosterone, estradiol, oxytocin, and thyroid hormone, also affect both men and women's brains, causing differences in everything from pain response to aggression and emotional responses. In the next chapter, We'll talk about how the range of hormones affects functions of the brain.
Despite the popularity of studies that say sex differences are hardwired into brain structures, right now that assertion appears to be unproven. We have so much to learn about whether and how much gender behavior is influenced by differences in brains and hormones—even the best neuroscientists are still learning.
So when you're sorting through all the latest studies mentioned on Google News or articles in Newsweek, withhold your wholehearted approval until you've seen multiple large-sample studies. Some research might say you were born with limitations due to your gender, but others say that's not true. If you have to choose between thinking, “Oh well, that's just the kind of person I am,” or thinking “I can move beyond my limitations and perceptions,” why not go for the second?
No matter what your brain holds right now, from genetics to cultural reactions to annoying habits you learned from your parents, it has the ability to change. You can get a doctorate in diffusive biomolecular reactions, teach yourself to compartmentalize your emotional reactions, and learn the latest features on new cars—if you want.
No matter what your brain holds right now, it has the ability to change.
No matter how you use your 125 trillion synapses, choose the path that gives you all the options you want. Then your brain will know it's working for a powerful and aware woman.
Chapter 3
Swimming in Different Hormones
Variations Beyond Brain Structure
On the one hand, [men will] never experience childbirth. On the other hand, we can open all our own jars.
Bruce Willis, actor
When women are depressed, they eat or go shopping. Men invade another country. It's a whole different way of thinking.
Elayne Boosler, comedian
Have you ever worked on those find-the-difference photo puzzles? On one side, you see a picture of a celebrity like Beyoncé getting out of her limo. Next to it is the same picture, but with a few changes: the rearview mirror may be backwards, a fan in the background is missing, or there's an extra gold button on her jacket.
Male and female brains are kind of like those side-by-side pictures—mostly the same at birth but with a few differences.
Now imagine that the left picture of Beyoncé was swished in blue tint and the right one in red. The pictures look different right away, even before you look for the changed details.
Think of those colors as hormones. Hormones “tint” the parts of the brain, changing some behavior, emotional responses, and even vulnerability to illnesses. Certain parts of the brain readily absorb the color and other parts don't.
Is everything colored by hormones? Yes and no. No matter how much men and women differ from each other, the individual variations within the same sex are much wider. So while men as a group tend to be more aggressive than women, you’ll find extremely aggressive women and extremely timid men.
“Gender roles are flexible, reversible, and not all-or-none,” says Donald Pfaff, PhD, author of Man and Woman: An Inside Story. “[B]iological influences on sex differences in brain and behavior operate at so many different levels, and they interact with environmental influences in so many different ways, that rigid, stereotyped ideas about what is and is not typical male or typical female behavior have become impossible to sustain.”20
When you understand that you're swimming in different hormonal waters than men, you can have more compassion for yourself. You’ll be open to the value of your brain's perspective on the world and be more relaxed with how wide the range of women's behaviors can be.
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