Boys are good at math. Girls are good at multi-tasking. Men talk less, and women are more empathetic. But are these differences a function of biology, or social conditioning? Do they even exist? The gap between male and female cognitive ability, as indicated by intelligence testing, has shrunk to almost nothing.
The underlying theory, presented in many books and articles across disciplines, is that the hormones that determine a baby’s sex during fetal development also cause changes in the brain.
Rebecca Jordan-Young, a Barnard professor with a doctorate in socio-medical science, decided to investigate this claim. She read 400 studies on the topic, and interviewed top researchers in neuroscience and neuropsychology. Her book, Brain Storm: The Flaws in the Science of Sex Differences is a summary of her findings. Jordan-Young recently visited Israel to speak about her book.
Sex differences and gender are in the news. A Canadian couple is refusing to announce their baby’s sex. Naturally, the child has a unisex name (Storm) and will wear unisex clothes. They’re not the first, either—a couple in Sweden is doing the same thing.
Jordan-Young debunks the idea that men and women’s brains differ in any significant way. When she went to look at the studies, she found that they were biased from the start. For instance, definitions of masculine and feminine were subjective, and might consider playing with Legos as a sign of masculinity in girls.
Twin studies have looked at this issue, based on the assumption that the females in boy-girl twins are exposed to male hormones in utero. Some studies showed that the female of boy-girl pairs is more aggressive, but when Jordan-Young asked experts in twin studies, many reported that they had found no differences. But studies that show negative results—”file drawer studies”—are less likely to get published. Eight published studies might show differences, but 200 unpublished studies might not.
Jordan-Young is razor-sharp and dedicated to rooting out bad science. Someone asked her about the effect of hormones like oxytocin on brain development and human personality. Women produce oxytocin during birth, lactation, and sexual activity, and it is sometimes referred to as the “mothering hormone.” Jordan-Young responded that men also produce oxytocin. As part of my lactation studies, I’ve read about its role in everyday social interactions.
Wrong assumptions about sex and gender differences affect health policy. Studies using actors show that doctors are more likely to order more tests for a male patient than for a female one, even when the two present with identical symptoms. Women, especially the elderly, get less pain medication and their symptoms are more often presumed to be psychosomatic.
Even when there are differences between the sexes, like in the risk of getting certain types of heart disease, this may be more attributable to differences in body mass or height. The overlap means that making generalizations can lead to a wrong diagnosis.
Physically, the brains of men and women are nearly identical. The only difference is an extra nodule in the hypothalamus of women. No one is sure what it does, but comparisons with animal brains suggest it may regulate the menstrual cycle.
The theory that hormones affect brain development in utero has a serious flaw. Genitals develop as either male or female at a critical point during pregnancy. But brain development lasts longer in humans than in other vertebrates, and continues beyond pregnancy.
Jordan-Young also has noticed more sexism in child-rearing than in the past. When shopping for a toy online, she was immediately asked whether it was for a boy or girl.
So what will happen to those “genderless” children? Will their masculinity or femininity rear up in the end? Or will they be free to develop as individuals, without social gender constraints?
Ph.D. in Parenting wrote a post about parenting boys and girls differently.