Читать книгу Brain Fitness for Women - Sondra Kornblatt - Страница 16

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.