When Odd Girl Out first hit book stands, it was the first text to delve into the politics of girl aggression. It was 2002, and bullying was barely on the radar: Mean Girls wouldn’t hit theaters for two more years; it was pre-“It Gets Better” project, and long before anybody would hear the story of 15-year-old Phoebe Prince (or the many bullying-related suicides that followed).

But Rachel Simmons, at the time a Rhodes scholar—with her sights on law school—had a feeling she was on to something, if for no other reason than the response she’d get from friends when she brought up the subject. When she finally sat down with a group of Washington ninth graders to talk about girl bullying—one of what would be many sit-downs like this—the depth of the topic suddenly became clear.

“Girls can turn on you for anything,” one girl offered.

“Girls are secretive,” posited another.

“Girls are manipulative,” somebody suggested.

“They destroy you from the inside,” the group said.

And then, finally: “There’s an aspect of evil in girls that isn’t in boys.”

In strong, matter-of-fact voices, the girls painted themselves as disloyal, untrustworthy, and sneaky. They described their friends as “fake” and manipulative, just waiting for the appropriate moment to exact revenge. And in almost every group session—Simmons conducted eight that day—someone volunteered her wish to have been born a boy. “Because boys,” Simmons recounts, “can ‘fight and have it be over with.’”

Girls, apparently, cannot. Which is a window into what Simmons describes in the latest version of Odd Girl Out—released this month—as the hidden culture of female aggression: a kind of torment that is serious, but exists just quietly enough for parents and teachers not to notice. “Girls use backbiting, exclusion, rumors, name-calling, and manipulation to inflict psychological pain on victimized targets,” Simmons writes. “They flash looks, pass notes, and spread rumors.” It’s different from the fists or shouts that are a staple of male aggression, yet can be even more crippling—leaving girls to turn inward, wondering what went wrong.

“That’s part of what’s so dysfunctional about this behavior,” Simmons, who cofounded the Girls Leadership Institute, tells The Daily Beast. “It doesn’t give girls an opportunity to remedy or repair. The experience of not knowing why somebody is mad at you can derail her entire day, or maybe even her entire academic year.”

Simmons wrote the first edition of Odd Girl Out as an observer—her data based primarily on interviews with hundreds of women and girls. There are the queen bees who control their prey; the burn books circulated to humiliate and bite; there are rumors and backstabbing; and finally, the feelings of pain and revenge still raw decades later. Her goal? In part she wanted to prove that girl aggression indeed existed—that it wasn’t just a “passing phase” that many would grow out of. “There was always a sense that girls could be mean, but it really lived in the shadows for a long time,” Simmons says. “It was everyone's personal story, but there was no collective narrative.”

This time around, the narratives are constant. Reality TV producers have suddenly discovered that girl aggression sells, and so they’ve churned out scores of programs whose characters engage in it. “Mean Girls” is the catch-phrase du jour, with a new breed of “expert” looking to cash in. Forty-five states now have anti-bullying laws on their books, yet most of them deal primarily with its physical aspects. (Earlier this week, viral singing sensation Rebecca Black revealed she was leaving school as a result of bullying by her peers.)

New technology, meanwhile, has changed the game for good: the detachment of a computer screen makes it easier to say things we normally wouldn’t; the option of anonymity can make inflicting torment even more alluring. “Social media has given girls an entirely new plane on which to harm themselves”—allowing instant access to events they were excluded from, or conversations they weren’t invited to join, says Simmons.

And while boys suffer the effects of cyberbullying, too—the most twisted example, perhaps, being the tragic bullying of Rutgers student Tyler Clementi—studies show that girls are 10 percent more likely to be targets of cyberbullying, and more likely to do the online bullying themselves, too. Social media, says Simmons, offers “the perfect alternative to the direct conflict so many girls disdain.”

But that conflict avoidance isn’t new. Rather, says Simmons, it’s the result of centuries-old stereotypes by which this behavior has been learned. Young girls may be entering the workforce in droves, but there remains a feeling among young women that it is femininity, not feminism, that is the expectation: in one study, from the University of Michigan, researchers found that girls were told to be quiet, speak softly, or use a “nicer” voice about three times more often than boys, even though the boys were louder.

“Silence is deeply woven into the fabric of female experience,” Simmons writes. When she asked a group of middle-school students to write down how society expects an “ideal” woman to behave, the girls used words like “girlie,” “kind,” and “doesn’t get mad.” “Boys don’t care about getting into trouble,” one girl told Simmons. “They think they’re all bad and don’t worry about it. But girls don’t want anyone to know... Girls worry about how they’re going to look.”

Simmons knows she faces an uphill battle—but her goal this time around is to be prescriptive about the problem. “We have to teach girls communication skills,” she says. “If you can’t tell a girl how you feel, how are you going to ask your boss for a raise?”