Why did you write this book?

Like many parents, I was fascinated by the differences between my daughter and sons.  But as a neuroscientist, I was curious how these differences are reflected in their brains. And if there are differences between boys’ and girls’ brains, what causes them—nature or nurture? I’ve also always been fascinated by the degree to which our personalities and abilities are shaped by innate factors, such as genes and hormones, versus environment—learning and experiences. Sex differences are a perfect distillation of this question, because there are obviously inborn biological differences between boys and girls, as well as deep differences in the culture boys and girls grow up in. I relished the chance to dig into the actual scientific data on the comparative roles of nature and nurture in creating sex differences in children’s brains and behavior.


What is the main thing you hope readers take away from your book?

That boy-girl differences are not as “hard-wired” as many parents today, imbued with the Mars/Venus philosophy, believe. Yes, there are innate differences, but we should be aware of how they become magnified through our own parenting and marketing, and especially through our kids’ own culture. Also, I would like readers to come away with a sense of how fantastically plastic the human brain is. Whatever you do is what your brain becomes “wired” for. So any time you see an obvious difference between men and women, or boys and girls, you have to ask yourself: How did they spend their time over the past three or thirty years to make their brains so good (or so bad) at certain skills?


Did your views about sex differences change while you were writing this book?

Absolutely. As a biologist, I started out very focused on figuring out precisely how boys’ and girls’ brains differ and the role of hormones in creating such differences. But the data just aren’t there! Scientists have identified very few reliable differences between men’s and women’s brains, much less between boys’ and girls’. So while I’d always intended to cover the “nurture” side of the equation, my focus shifted midway through my writing toward uncovering the many ways in which parents, teachers, and especially children’s own choices about gender-appropriate behavior trigger the neuroplasticity that magnifies small initial differences into much more blatant boy-girl gaps.


What’s the biggest myth you hear about “how boys are”? And “how girls are”?

Well, the most dangerous is that boys lack empathy. The ability to read others’ emotions is crucial in any social species, and hardly something males could have made it through evolution without. The actual size of the sex difference in empathy is small in children, and the ability to read emotions in others is clearly teachable (indeed, this is the core of most successful therapies for autism). Parents and teachers should not let boys’ tendency to talk less about their feelings convince them that they actually feel less, or that they fail to understand others’ emotions. Babies—both male and female—are riveted by social stimuli, and parents should make every effort to engage both their sons and daughters in shared eye contact and emotional expression. Think Thomas the Tank Engine, a toy that appeals to boys but has great emotional content.

Another myth is that girls are not aggressive. It’s true that they rarely hit their friends, siblings, or others, but “relational aggression” is a serious matter among middle- and high-school girls. And it’s so much harder to stamp out than physical aggression, which is the focus of most anti-bullying campaigns. Similarly, girls are plenty competitive, but it’s usually over appearance and thinness. (That’s why we have an epidemic of anorexia and bulimia.) Girls should be taught that competition is a good thing, when it’s friendly and channeled into athletics, academics, or other achievements (as opposed to social climbing). Girls’ competitive feelings should be acknowledged and used to their benefit rather than to undermine one another.


Which genuine differences surprised you the most?

The writing gap is much larger than I appreciated—especially when you consider all the great male writers through history. Boys clearly need more attention in this area, and I’ve suggested several ways to do this in the book. I was also frankly surprised that the sex difference in spatial navigation is as large as it is. I love maps and always orient myself in terms of north-south-east-west, so to learn that women really are much poorer at this than men was eye-opening, and makes me all the more determined to use such “direction-speak” when I’m driving my kids—daughter and sons—around town.

On the other hand, I was honestly surprised at how weak the evidence is for hormonal effects on our mood and thinking abilities. While prenatal testosterone pretty clearly influences play behavior and perhaps on later sexual orientation, the sex hormones that rise at puberty and remain elevated in adults have surprisingly modest effects on our thinking—except for sex drive, which testosterone elevates in both men and women!


Parents like to believe we don’t reinforce sex stereotypes. Are we kidding ourselves?

To some degree, yes. The problem is that gender is impossible to ignore. Though at times we bend over backward to counter the stereotypes, much of the time we default to interacting differently with boys and girls, just as we unthinkingly relate differently to adult men or women. And of course, any time we do deliberately challenge a gender stereotype, the kids themselves balk, because they so strongly want to gender conform. (If anything is “hardwired,”  I believe it is children’s desire to have an unambiguous gender identity, male or female. Even gender dysphoric children, those who express unhappiness about their biological sex, work so hard to conform to the norms of the other sex. They’re not choosing to be androgynous.)  In spite of what we overtly preach about gender equality, parents implicitly treat boys and girls differently much of the time, just as we are unconsciously biased about race, age, and every other group characteristic. Things have changed a lot for girls; parents’ encouragement that “you can do anything you want” is paying off, especially in sports, scholastic achievement, and leadership. But we have a lot further to go, especially for boys, who I believe are short-changed by assumptions about their slow maturation and the limited range of opportunities that are considered “masculine.”


Your introduction mentions that these are “politically sensitive” issues. Have you witnessed anyone become upset by your research findings?

Another journalist told me that people start arguing with her whenever she describes my book to them. I think we have become enamored of the Mars/Venus dichotomy. Somehow, it empowers women (about their communicative superiority) while reinforcing men in the comfortable notions of masculinity (sports and leadership). And to suggest that such differences are actually learned in large measure, instead of programmed by evolution, is less fun than picturing men retreating to their “man caves” and women to their cliques.  It also puts unquestionably greater pressure on parents to change our ways, which is not easy. No one wants to accept that we stereotype our children, and bucking the trend (by allowing your son to wear pink or signing up your daughter for basketball) is just too hard most of the time.

On the other hand, some people still get upset when you posit any kind of innate behavioral or ability differences between boys and girls, arguing that such claims are inevitably used to discriminate, or at least to set up different gender expectations that end up limiting opportunities. (The same argument, when applied to racial differences, resonates even stronger.) But as a biologist, I can’t deny that a certain amount of gender differentiation is probably baked into human brain development. Testosterone exposure before birth likely does promote certain behaviors, like rough-and-tumble play and later sexual attraction to females. It’s not definitive, and its effects on other behaviors, including gender identity, appear to be more modest.  To me, the biggest gap in this equation is that neuroscientists have yet to figure out how testosterone affects the human brain, beyond a very tiny zone called the hypothalamus.


You have two sons and a daughter. Do you think either girls or boys are harder to raise in a gender-balanced way?

Absolutely. Girls can do anything these days. Although they often restrict themselves to certain activities (because they see a computer programming camp as unfeminine), their parents are not usually feeding them such ideas. And you definitely see girls moving into areas they didn’t broach before, like playing the trombone or leading student council.

With boys, it’s harder, because our society is still very homophobic and fears that sending a boy to ballet class will change his sexual orientation. So you can get away with raising your daughter along a broader expanse of the gender spectrum, but boys are being painted into an ever-tinier corner as they avoid domains (like art and theater) that have taken on a feminine label. It takes a community-wide effort to make a difference. In my town, we happen to have a great choral teacher who gets considerable numbers of middle-school boys singing and dancing. But this is just one lucky happenstance of local culture. Most other activities in childhood are distressingly gender-segregated, which is bad for both boys and girls.

The only way around this pink-blue barrier is to require kids to engage in certain activities. When I was in middle school (at the dawn of Title IX), everyone had to take woodworking as part of the art curriculum. Today, we let kids choose woodworking versus painting, so guess who ends up in each class? As I argue in the book, we need to reign in some of kids’ choices if we want to reduce some of the gnawing gaps between boys and girls.

On the other hand, as a mother of a teenaged daughter, if you ask me which gender is harder to raise … well, answering that will just get me into a lot of trouble at home.