Life Magazine, July 99
“WHAT'S THE DIFFERENCE BETWEEN BOYS AND GIRLS?”
By Deborah Blum
A funny thing happened when we left "puppy dogs' tails" and "sugar and spice" behind. Scientists discovered that
it's not just our culture that makes rules about gender-appropriate behavior--it's our own body chemistry.
My four-year-old son asked for a Barbie this year. His blue eyes were hopeful, his small face angelic. His mother
was suspicious.
Between this child and his older brother, our house is a Toys R Us warehouse of heavily muscled action figures,
dinosaurs with jagged teeth, light-up swords and leaking water pistols. Complaint is constant--Oh, Mom, you're no
fun--over my refusal to buy more additions to the arsenal. My older son at one point began to see weapons in
household objects the way adults dream up phallic symbols. "Shoot her with the toothbrush," he once shouted to a
companion as they chased the cat around the house.
"Why do you want the Barbie, honey?" I asked.
"I wanna chop her head off."
There I was again, standing at the edge of the great gender divide, the place and the moment where one becomes
absolutely sure that the opposite sex is, in fact, opposite. I know of no way for women of my generation, raised to
believe in gender neutrality, to reach this edge faster than through trying to raise children.
"I did not do this," a friend insisted on the day her son started carefully biting his toast into the shape of a gun. "I
think my daughter has a pink gene," a British journalist confided recently, as she confessed that her daughter has
not only a Barbie collection but all the matched plastic purses and tiny high-heeled shoes. I don't think in pastels
myself. I think jungle-green, blood-red. Most of all, I think there's a reason--a reasonable biology--to the differences
we see in little boys and girls, men and women, males and females.
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We are, I hope, moving past the old politically correct notion that we are pure culture, that children are born blank
slates to be influenced--or, worse, manipulated--by the adults around them. There's a straightforward reason why
we are a male-female species: Reproductively, it works. We are all born with bodies designed to be the same
(breathe, circulate blood) and to be different (produce sperm, produce eggs, produce milk, produce none). There's
an internal biology--structural and behavioral--that supports those differences. It's not all of who we are, but it's a
part. When is biology the primary influence? Where does culture overtake it, and at what point, in the startlingly
fluid landscape of human behavior, does one alter the other?
One of my favorite illustrations of the way culture fine-mates us for gender roles has to do with the Barbie versus
Godzilla effect. It turns out that lots of little boys ask for dolls and other so-called girl toys. They aren't encouraged,
though; parents really hesitate to buy their children "gender inappropriate" toys. In a study involving almost 3oo
children, researchers found that if little boys asked for a soldier equipped with battle cannons for their birthday,
they got it some 70 percent of the time. If they asked for a Barbie doll, or any of her plastic peers, the success rate
was 4o percent or less. Can you think of a child who wouldn't figure out in, oh, a day, how to work that system?
Marc Breedlove, a neuroscientist at the University of California, Berkeley, points out that splitting apart biology
and culture is analogous to splitting hairs. But scientists try to separate the strands anyway, exhaustively exploring
early development. A few ambitious scientists have even looked for prebirth differences, arguing that it's difficult to
slap too much cultural attitude onto a fetus. It turns out that boy fetuses are a little more active, more restless, than
girl fetuses. And in the first year after birth, toy preferences already seem distinct: Boy infants rapidly engage with
more mechanical or structural toys; little girls of a few months gravitate toward toys with faces, toys that can be
cuddled.
The world of play--the toys we gravitate to, how we play with them, how we play in general--has now become
serious business to scientists. Today's hottest theory of play is that it's a practice run at the challenges of adult life.
Through games, the experts tell us, we learn the art of measuring the competition, how to win and lose gracefully
(we hope), which leads pretty directly into how to build friendships. In scientific terms, we learn socialization.
"Play offers a non-life-threatening way of asserting yourself," says Christine Drea, a researcher. "By playing, you
learn skills of managing competition and aggression." We are a social species. We find isolation destructive, and
we establish patterns of childhood play that reflect adult social structures. In humans, our patterns tend to conform
to our chemistry: Human males are likely to produce seven to 10 times more testosterone, for example, than
females. (Hyenas are quite a different story; see box, page 52.) And so, you would correctly predict, little boys tend
to be more rough-and-tumble than little girls. That's true, in fact, for the entire realm of primates (monkeys, apes,
man).
Back in the late 1970s, Robert Goy, a psychologist at the University of Wisconsin, first documented that young
male monkeys consistently played much more roughly than juvenile females. Goy then went on to show that if you
manipulate testosterone level--raising it in females, cutting it off in males--you reverse those effects, creating sweet
little boy monkeys and rough-and-tumble girls. We don't experiment with human development this way, obviously.
But there are naturally occurring genetic variations that make closely comparable points. As mentioned earlier,
human males circulate higher levels of testosterone. There's a well known exception, however, called congenital
adrenal hyperplasia (CAH), in which a baby girl's adrenal gland inadvertently boosts testosterone levels.
Researchers have found that CAH girls, in general, prefer trucks and cars and aggressive play. That doesn't mean
they don't join in more traditional girl games with friends--but if left to choose, they prefer to play on the rowdy
side of the street.
Higher testosterone levels are also responsible for another characteristic: competitiveness. In fact, testosterone is
almost predictable in this regard. It shoots up before a competition; that's been measured in everything from chess
matches to soccer games to courtroom battles to brawls. It stays up if you win, drops if you lose. Its role, scientists
think, is to get you up and running and right on the competitive edge.
Even in preschool, boys and girls fall into very different play patterns. Boys tend to gather in larger, competitive
groups. They play games that have clear winners and losers and bluster through them, boasting about their skills.
Girls, early on, gather in small groups, playing theatrical games that don't feature hierarchy or winners. One study
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of children aged three to four found they were already resolving conflict in separate ways--boys resorting to threats,
girls negotiating verbally and often reaching a compromise.
There are some provocative new insights into that verbal difference. Recently, researchers at Emory University
have found that little female monkeys are much quicker to pick up "verbal" skills than little boy monkeys. Sound
familiar? The small female monkeys do more contact calling (cooing affectionately) than their male counterparts.
And it appears, again, that this is related to their mothers' prenatal hormones. Some very preliminary tests suggest
that females exposed to androgens early in their fetal development become more like male monkeys: They are less
likely to use language to express themselves.
In humans, too, we look for natural biological variations. In general, girls have sharper hearing than boys--the tiny
hair cells that register sound waves vibrate more forcefully. These are ears tuned for intense communication. (The
rare exception tends to be in boy-girl twin pairs. Those girls are more likely to have ears built a little more like their
brothers'--less active hair cells, notched-down response. Researchers looking at this suspect a higher exposure to
androgens in utero.) There's something about the biology of the egg-producing sex that seems to demand more
acute communication abilities.
Of course, there's a whole range of personalities and behaviors that don't fall into any of the obvious stereotypes.
What about tomboys, those exuberant girls who prefer softball to tea parties? What about the affectionate sweetness
of little boys, who--away from the battle zone of their friends and brothers--turn out to be surprisingly cuddly and
clingy? What about the female stiff, the chatty male, and so on, into infinity? The quick answer: Sex differences are
group differences, overall patterns.
The complex of genes and hormones and neurotransmitters and internal chemistry that may influence our behaviors
varies from person to person and is designed to be flexible. There's nothing in average, everyday biology that
forbids either the truck-loving girl or the boy who likes to play house, the aggressive, competitive adult woman or
the nurturing, stay-at-home man. Human biology makes room for every possible type of personality and sexuality
in the range between those stereotypes.
And finally, the way we behave can actually influence our biology. The link between testosterone and competition
makes this point perfectly. Yes, corporate lawyers tend to have higher testosterone levels than ministers. But there's
a chicken-or-egg aspect to this. Is the lawyer someone born with a high testosterone level? Or is it the profession
that pushed it up? Or some combination of both? It's worth noting that the parallel works in men and in women;
women in competitive jobs have more testosterone; men who stay home with their children have less.
Nothing in biology labels behaviors as right or wrong, normal or abnormal. Any stereotypes we impose on
children--and, by extension, adults--are purely cultural, not biological. For example: Little boys are noisy and
rambunctious; we tend to equate that with being emotionally tough. But what science actually tells us is the exact
opposite. Little boys, we're learning, need a lot of emotional support. One revealing study of children of depressed
and withdrawn mothers, clone at U.C. Berkeley, found that a lack of affection actually lowered the IQ of little boys.
Laura Allen, a neuroscientist at the University of California, Los Angeles, explains it like this: "I think boys need
more one-on-one attention. I think affection may change the sex hormone level in the brain, which then affects
brain development." Both the Berkeley study and a more recent federal daycare study find a different pattern in
girls. They're emotionally sturdier--I think most of us have already figured this out-and their healthy development
seems most harmed by being restricted. It's confinement that seems to drive down IQ in our daughters.
What's the real difference between boys and girls? More, and less, than we thought. With rare exceptions, the
anatomy of gender is straightforward, separate. But the chemistry of gender is more complex. It's a continuum, I
think, and we can each find a place within the wide band of "normal." What's more, we can change our place. And
we can influence our children's places--not by force but by guidance.
And so, if you're wondering, I did not buy my son the doll. I'm too grown up these days to approve of
dismembering pricey toys. I did let him pick out a scaled-down Barbie, instead of a toy car, in one of those fastfood kid's meal promotions. It turned out to be cream and gold in appearance, annoyingly indestructible, and he lost
interest. These days, he likes to make books and draw pictures of blood-dripping dinosaurs. Me? I pass him the red
crayons.
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Further reading: Among the best of the recent books that explore the shifting sands of gender identity are Deborah
Blum's Sex on the Brain: The Biological Differences Between Men and Women (Penguin) and Natalie Angler's
Woman: An Intimate Geography (Houghton Mifflin).
PHOTOS (COLOR): LIFE turned a group of boys and girls (ages four to six) loose in a playground, with equal
access to toys, equipment and dress-up clothes. The two genders generally conformed to stereotype--right down to
their knees.
PHOTOS (COLOR): By preschool age, little boys are playing hierarchical games in which they challenge each
other to win, and boast about being winners. Girls tend to prefer less competitive activities, like dressing up.
PHOTOS (COLOR): One scientist believes that society is responsible for many of our predispositions--except
when it comes to aggression. There, the difference between boys and girls can be traced to a single chemical source:
testosterone.
PHOTOS (COLOR): Swapping toys may not change the basic differences in the ways the genders approach play.
Little boys may tear apart their dress-up clothes, and little girls may find a way to interact collaboratively with toy
cars.
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By Deborah Blum
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