Is boy and girl behavior hardwired in babies' brains at birth, or can we help all babies develop into children who have both "boy" skills and "girl" skills. We ask the author of "Pink Brain, Blue Brain: How Small Differences Grow Into Troublesome Gaps - And What We Can Do About It."

What led you to write this book?

I was all caught up in the whole Mars/Venus thing - the notion that men and women are fundamentally different and that women find meaning through relationships and men find meaning through… sports and television (laughs). I bought into the idea that men and women are evolved for different abilities. But when I started to look into the data I found that it wasn’t as solid as the evolutionary psychologists were portraying. There is lots of data on boys and girls that doesn't find sex differences. But that data doesn’t get published. There's virtually nothing proven about inborn differences between boys’ brains and girls’ brains. But we do know very clearly that early experience shapes the brain’s neuro circuits in a permanent way. Gender behavior is shaped early on in babies and kids by experience - the role models and the environment they are exposed to. As parents we definitely do have an impact over how our children spend their time, particularly when they’re young, and therefore what brain circuits they're wiring up.

You argue that parents relate to babies in different ways depending on whether they’re girls or boys, even when we think we’re not. You also say that relating to babies in a certain way affects how their brains get wired.

As a parent myself, I know it’s absolutely impossible to treat people in a gender-neutral way. There was that whole series of “Saturday Night Live” skits about “Pat” – and whether Pat was a man or woman. It was so disconcerting to people: How do you relate to this person if you don't even know if it’s a man or a woman?

We treat babies the same way. Strangers on the street, the first thing they’ll ask, if they’re not sure, is “is it a boy or a girl?” And very often if they’re not sure, they prefer to make the mistake of assuming it’s a boy because parents are more offended to have their boys mistaken as girls than vice versa. There's no question that if you look at how parents shape children's gender behavior, one thing that's universal is that parents, particularly fathers, discourage feminine play in boys. To a much more modest extent we discourage masculine play in girls.

While much “boy” or “girl” behavior develops later on, real differences are already apparent in a 2-year-old, you’ve determined.

The differences in infancy are very subtle - baby boys are very responsive to faces and voices and infant boys like dolls just as much as they like trucks - but they become more obvious after the first year. By the time they're 2 or 3, you definitely see boys and girls go their separate ways. Boys will choose very typical “boy things” - trucks and balls versus tea sets and dollies. In preschool you see the most dramatic differences, particularly in toy choice. Another dramatic difference is activity level - boys are generally more active throughout childhood - and this difference first emerges in the second year of life.

How do we shortchange boys and girls when we assume that they’re very different and we relate to them that way?

If we only let girls do “girl things” and only let boys do “boy things,” if we only relate to girls in a touchy-feely way, only relate to boys in rough-and-tumble ways, we’re going to exaggerate their differences. Boys’ toys promote visual and spatial skills and girl play promotes relational and communication skills, and that’s where these small differences start growing into bigger gaps. And, to the extent that we are worried about certain gender gaps in education, leadership and parenting responsibilities, the only way those things are going to change is through development and early rearing.

So if I as a parent wanted my daughter to be well-rounded - to have, say, skills related to spatial awareness as well as relational skills, what types of toys would help?

We need to find ways to get girls involved in spatial things like building toys and puzzles. When it comes to building toys, there are studies that show that kids who play Legos and other three-dimensional building games do improve on spatial skills tests. But 80 percent of Lego sets are sold as gifts to boys.

And other than gender-opposite toys, what can parents do to bridge the gap?

For parents of young boys, it’s really important to talk to them and sing to them and read to them. Boys absolutely can benefit from more verbal and communicative engagement, more eye contact. Parents should start the story time as young as possible. Girls will sit down with a pile of books and spend a little more time with them than the boys will. With girls, the important thing is getting them moving, engaging their three-dimensional abilities through sports, as well as puzzle-solving and building toys.