My son celebrated his third birthday last week by careening down the sidewalk on a black, three-wheeled vehicle that looks like something General Dynamics might have worked up for the Pentagon. "Tricycle" does not do this item justice; it is what I believe the bikers call a chopped hog, with mysterious dials and stick-on tachometers and a red side lever that promises when pulled to send my kid into spinouts that will enthrall his fiendish little friends. There is no actual weaponry hanging off the chassis, which was my principal consolation as I watched Aaron pedaling furiously through the aisles of the toy store the day we went tricycle-shopping, but I should have known better.

I live with the kid. I should have known. On his inaugural ride through the neighborhood, he stopped 20 feet from the driveway, scrunched down to look hard-eyed through the small plastic windshield, and cried, "Bad guys!" Then he pulled up the side lever and machine-gunned the bad guys into oblivion.

This is a kid, you understand, who has spent his entire life in a university town where the neighborhood children's store, the kind of richly stocked yuppie institution that keeps a toy-filled corral to entertain the children while you shop, does not even carry guns. This is a kid whose television-watching has for two years consisted of something under three hours a week of "Sesame Street," where the most violent moments involve elephants falling through holes in the floor. There are no toy guns in the homes of his four best friends, and the only gun I have ever found in his books is the one on the tank in the Cars and Trucks book, the discovery of which set off a conversation that gives you some idea what we're working with here:

Aaron: "Why does the tank have a gun?"

Mother: "Because the soldiers use it to shoot sometimes."

Three-year-old friend: "Do the soldiers go to jail? My mommy says if you shoot somebody you have to go to jail." Aaron's nursery school is rife with mommies of this sort. These are children of what used to be the Berkeley left, a generally thoughtful collection of men and women who are still, apart from an unfortunate preoccupation with mesquite and baby vegetables, considerably interested in matters of politics and social experimentation. The men raise funds for the nuclear freeze and have long, compelling dinners with colleagues from their old men's groups. The women walk in anti-Reagan rallies and have long, compelling lunches with colleagues from their old women's groups. The place is littered with female bus drivers, male preschool teachers, and women who spent the better part of the 1970s wearing overalls and old running shoes.

If ever a place awaited a generation of new children, of tough little girls and kind little boys, this was it.

So what did we get?

We got Aaron, who shot his father this morning with a waffle.

We got Devlin, who refuses to go to her nursery school in anything but tights and a dress.

We got Nicole, who went to a wedding this summer in her first party outfit and now insists every morning -- the kid is not even 2 years old yet -- that her mother pull out both a dress and the white T-strap pumps, which Nicole understands to be shoes with seat belts.

We got Rachel, who by age 6 was the best pitcher and catcher on the block, and who was overheard one day being urged by the local boys to come play with them. "No," Rachel said primly. "But I'll be the cheerleader."

Rachel's mother Susan, a fierce-willed attorney who in fact had taught Rachel everything that girl knew about catching a softball, summoned all she had to keep from roaring out the front door to shove her daughter back into the game. "It wrecked me," she says. I remember quite vividly the eight months or so when Rachel's principal delight in life came from a collection of pastel, Degas-like tutus; she was barely 3 years old then, and as her mother and I tried to make sense of the delicate mass of lace that had consumed Susan's feisty little girl, I heard for the first time what has since seemed to me a kind of bewildered and conspiratorial refrain among women whose children arrived in the wake of the women's movement:

They're different.

The boys slug each other and the girls paint their fingernails.

Where are they getting this stuff?

I have been thinking about this ever since my son, in a sudden fall from innocence somewhere into his second year, discovered guns. Unless you move to a television-free commune in the mountains, you cannot shield a North American kid from guns. The freeway into San Francisco still leads us under Marlboro billboards. And shortly after Aaron figured out how to change channels, I left him and a friend watching Sesame Street and then walked back into the living room to find them enraptured by some network cartoon in which flying caped persons appeared to be blasting each other to bits.

"We're watching a shooting program," Aaron explained.

Also, we got Ricky. Ricky is the James Dean of the nursery school. He is blond and tough and very smart, and he has guns. He doesn't bring them to class, since this is a no-gun Berkeley nursery, but we know he has guns because on the afternoon of his third birthday party, his principal gift was an enormous boxed assortment of G.I. Joes. "Who told you guns make a noise like that?" my husband would ask Aaron. "Why do you think guns are for shooting bad guys?" And the answer, reliably, was Ricky.

So the culture offers them guns. I grant considerable power to the culture. But the culture offers them computers, and ocean liners, and farm animals, and a lot of other arguably interesting phenomena that do not flower instantly into passion bordering on obsession. Only dinosaurs have approached guns for sheer staying power in our house, and it is plain to me that dinosaurs are about precisely the same business. Did we care about the cute little baby protoceratops seen clambering newborn from its egg? No. We wanted Tyrannosaurus rex. We were heard, at regular intervals, arguing about who would play Tyrannosaurus, making the attack with his terrible big teeth, and who would play the unfortunate Stegosaurus, fighting back with what Aaron used to describe with great relish as "his SHARP NEEDLES."

The girls -- I am about to make the kind of sweeping statement that in the glory days of the women's movement used to drive me crazy -- don't go around shooting each other. They don't leap up at the school birthday party, as Ricky did this very morning, demanding a Tyrannosaurus cupcake and assaulting their comrades with imaginary fangs. They don't even want the airplanes and pickup trucks we keep thrusting at them. I know there must be girls somewhere who could be hauled out to disprove this, but for every one of them I will show you 20 ardent feminists' daughters ignoring the construction set while they coil pink bracelets up their arms.

One is told, in an informal survey of psychologists and "You and Your Child" sorts of paperbacks, that young children will resort to something approaching parodies of sex roles in their need to identify themselves as one sex or the other. That will do for a hint of explanation; the female kitties in the Richard Scarry books are identified by their dresses, and it must be acknowledged that for all her coaching moxie, Rachel's mother does not spend much time playing softball in the street.

But she's no cheerleader, either. None of the men in Aaron's immediate vicinity, as far as I can determine, occupy their spare moments blowing up bad guys. There is more at work here than the tainted winds of the world at large, and it makes me slightly uneasy to report some professional confirmation for this. Two California psychologists, Eleanor Maccoby of Stanford and Carol Nagy Jacklin of the University of Southern California, have over the last decade produced one textbook and a large collection of papers examining boy-girl differences, many of them observed among 200 Northern California children Maccoby and Jacklin have followed from birth through first grade. The studies, undertaken over the objections of a few 1970s feminists who thought them politically imprudent, have challenged some conventional psychological wisdom about boy behavior and girl behavior; they found, for example, no evidence that girls are more suggestible than boys or that boys are more analytic than girls.

But they also found "rough-and-tumble play," the academic term that embraces roaring dinosaur duels, overwhelmingly the terrain of boys -- there were girls who played rough, and boys who didn't, but the scale on the whole was exceedingly male. They found that pairing unacquainted 33-month-old girls and boys sharply altered the social balance of same-sex pairs; girls who had played briskly with each other became more passive around the boys, moving closer to their mothers. They found -- this is the one that sets my teeth on edge -- that the boys and girls alike paid attention when a boy cried "No!" but that a similar prohibition from a girl tended to have little effect on the boy she was playing with.

Familiar explanations like a preponderance of testosterone are too simple to be of much use; hormones, Maccoby observes, have different effects when they are administered to different sexes. "Predisposition" is the word Maccoby uses, suggesting some complex calculus of biology and breeding -- "a predisposition, stronger in boys than girls, to be interested in issues of dominance."

Do we treat boy babies and girl babies differently from the beginning, even in Berkeley, even now? Probably. There are famous experiments that show how people coo gently over an unfamiliar baby dressed in pink and then make blustery talk about big strong boys when, without warning, the same baby is brought out dressed in blue. My husband decided a few months ago to let Aaron start punching him, in a friendly sparring-partner sort of way; Aaron loves it, and as he was flailing away at his father the other day, I asked if my husband envisioned making the same offer to a daughter. "You want to bet how interested she'll be?" he said.

Get in there and whomp him, I exhorted an imaginary little girl, appalled even as I thought it. My son did not grow up with baby dolls or tea sets; despite occasional sorties into liberated toyland, like my insistence on a small furnished structure that could conceivably be described as a dollhouse, I realized a while ago that I had no idea what our suburban toy emporium even stocked in its unlabeled but unmistakable Girl Section. The Girl Section gave me a pain, to tell you the truth. I wanted to look at the building sets, and the fire engines, and the cranes with their clever little crank-up chains. I suppose I have never abandoned the retroactive resentment of 1950s girls who waited for brothers to be born so the electric train could be set up, or dressed those Barbie dolls with their unfathomable bosoms, or braced for Bronx cheers from the outfield when we stepped up to home plate. Part of the cant of the new right is the notion that feminists did girls and women a massive disservice by for the first time equating femininity with wimpdom; this is nonsense, since any woman who was clinically awake during her childhood can tell you it was boys and the culture around them who made us understand that we were never going to keep up with them, but it is true that some of us have blurred dolls and small dresses into memories that still make us mad.

So here we are, pinned between plastic Howitzers and dollies with strawberries on their skirts, groping around for the middle ground we thought our kids would claim. Who knew it was going to be this complicated? Who imagined that a Berkeley psychologist, a woman still immersed in the principles of feminism and the New Left, would panic when her son did buck the machotrikes around him -- and asked for a canopy bed? The other boys will make fun of you, she muttered for days, suffering no illusions about who was really most worried about incipient sissiness. When she finally bought the coveted bed, she made it sure its canopy was an old-fashioned print that someone -- probably not the boys who came to cluster under it in delight -- might construe as western and cowboyish and, you know, male.

I am assuming we will get the hang of this after a while. I am assuming we will figure out how to stifle the urge to make small girls feel as bad about girlish trappings as the boys used to make us feel. I assume also -- it is unbearable not to -- that there is some merry lesson waiting in the wings, that the girls are going to show their silly dogmatic mothers that tutus and lipstick are not physical or intellectual retardants. Rachel is 9 now, and every morning, she goes into the bathroom and puts on moisturizer precisely the way Susan does. Forehead, left cheek, right cheek, chin. She is about as soft of spine as a Maine lobster. "Papa," Rachel will chide, "that's a sexist thing to say." She's terrific.

"I now accept it," Susan says. "I no longer go nuts. I don't feel that the fact that she likes to wear makeup and dresses means she's going to be a sweet, demure little girl. And I think, 'How sad that little boys can't do that, too.' "

As for the daily slaughter of bad guys in my own living room, I am trying to keep a lid on myself. No toy guns cross the threshold; in a city where schoolboys pack handguns to seventh-grade social studies, I can't stand watching my kid wave black plastic Magnums around. This bothers him not a bit; he figured out almost immediately that there is scarcely a building set in America, from Tinkertoys to those Legos with their sweet little plastic pine trees, that cannot be made into fierce and elaborate weaponry.

I think also that he has come to see that both parents, for reasons that mostly elude him but have something to do with the nature of real guns, are unenthusiastic about being shot at. Some weeks before his birthday, we made a foray into a shopping center toy store a long way from home. Aaron dove straight for a shelf that looked like the welcoming table at a Third World arms dealers convention, and as I followed him he looked up at me and said kindly, "Mommy, don't look at this. These are guns. You don't like guns, but I do. So I'm going to look at them."

There is always the possibility that by the age of 3 he has already ingested some creepy message about men protecting ladies from big bad guns. I don't think so, though. I think, all things considered, that this is a prince of a kid.