About a month ago I was invited to give a brief talk to my nephew Gianni’s first grade class—nothing too deep, mind you, rather simply about what it’s like living in a foreign place such as Belfast. The highlight of my presentation was the uproarious laughter that erupted when I mentioned that people on this side of the Atlantic refer to diapers as “nappies” and cookies as “biscuits.” But one must play to the audience.

Now, my sister resides in a small town in central Ohio, so perhaps there’s something about the mid-West which breeds especially endearing and affectionate six-year-olds, but I should be forgiven for momentarily siding with Rousseau that afternoon on his overly simplistic view that society corrupts and turns such naïve, innocent cherubs into monstrous adults. To give an example, one little girl waved at me in so kind a manner that it seemed, in that instant, I was in the presence of a better species of humankind, one that naturally regards other people as benevolent curiosities and the contrivances of social etiquette haven’t tarnished and brutally tamed genuine emotions.

What punctured this rose-tinted illusion of mine was the knowledge that these diminutive figures giggling and sitting Indian-style on the carpet before me might also be viewed as incubating adolescents. Perhaps it’s just me, but I’d swear the world knows not an eviler soul than an angry, angst-ridden, hormonally intoxicated teen. And if this little pigtailed girl is anything like the rest of her gender, in just a few years’ time she will unfortunately morph into an eye-rolling, gossiping, ostracizing, sarcastic, dismissive, cliquish ninth-grader, embroiled in the classic cafeteria style bitchery of adolescent female social politics.

If that strikes you as misogynistic, rest assured it’s merely an empirical statement. (Rest assured, also, that I’m afraid I have much in common with this tactical style, and I have great respect for more refined Machiavellians, so I’m not casting stones here.) In fact, over the past few decades, scholars from a variety of disciplines—including developmental psychology, evolutionary biology and cultural anthropology—have noted a striking difference in the standard patterns of aggression between reproductive-aged males and females. While teenage boys and young male adults are more prone to engage in direct aggression, which includes physical acts of violence such as hitting, punching and kicking, females, in comparison, exhibit pronounced social aggression, which includes such obnoxious things as mentioned in the various acts of bitchery listed above.

A prototypical example of an act of teenage social aggression is given by University of Flinders psychologists Rosalyn Shute, Laurence Owens and Phillip Slee in a 2002 article published in the International Journal of Adolescence and Youth:

Jo is a fifteen-year-old girl. She is average at her high school work and she is involved in school tennis in summer and netball in winter. In the past, she was well accepted, having a close group of friends and getting along well with most of her peers. After a day off with illness, she returns to school to find that things have changed. She walks over to her usual group but when she tries to talk to any of them, their responses are abrupt and unfriendly. She tries to catch the eye of her friend, Brooke, but Brooke avoids her gaze. In first lesson, she sits in her usual seat only to find that Brooke is sitting with someone else. At recess time, she joins the group late but just in time to overhear one of the girls bitching about her…

In peer discussion groups with teenage girls in South Australia, Shute and her colleagues found that Jo’s situation is incredibly common. And what’s especially sad is that adult authority figures such as teachers and parents often miss such devastating acts of reputational violence because they’re so subtle and often occur “in context”—that is, they’re less conspicuous than the physical altercations of boys.

Let me attempt to preempt the obvious criticism that this is not, of course, to say that all teenage girls are catty—need I really point out the obvious that many are of course wonderful, thoughtful and mature people? Nor is it to say that teenage boys are never socially aggressive or that girls don’t occasionally display physical violence. But the culturally recurrent findings of female social aggression, and the largely invariant age distribution where such behaviors and attitudes are especially prominent (flaring up between about age eleven and seventeen in girls), do suggest a strong psychological bent in the fairer sex that leads “naturally” to these types of catty displays.

This question of whether female social aggression is innate, much like men’s reaction to curl their hands into fists, was explored recently by Washington State University at Vancouver anthropologists Nicole Hess and Edward Hagen. In a 2006 study reported in the journal Evolution and Human Behavior, Hess and Hagen rounded up 255 undergraduate students—men and women ranging from eighteen to twenty-five years in age—and asked them to read and mull over the following social scenario, which I’ll summarize here for brevity.

Let’s say that you’re at a campus party and out of the corner of your eye you notice one of your classmates (another male student for male participants and another female student for female participants) conversing with the teaching assistant for the class you share with this other student. The other student, who is unusually short, is overheard saying some rather nasty lies about you—in particular, he or she is telling the teaching assistant that you haven’t been working on a joint project for the class. Instead, this person says, you’ve been slacking off, coming to class with a hangover and partying in Baja. Your TA glances over at you, with your beer in hand, and then glances away quickly as if disgusted. Then your duplicitous classmate walks over to you and says, innocently, “Hey! How are things going? Hasn’t the weather been great lately?”

Once participants read this basic story, they completed a questionnaire about how they’d like to respond. On a scale of 1-10, with 1 being “disagree strongly” and 10 being “agree strongly,” participants were asked questions such as, “I feel like punching this person right now,” “I feel like telling people at the party that this person is clueless and spews useless comments during lecture,” and “I feel like saying, ‘Yeah, the weather has been nice.” Whereas the first two items are measures of direct and indirect aggression, respectively, the last item presumably tapped into the participant’s willingness to turn the other cheek, so to speak. Importantly, Hess and Hagen also asked the participants how appropriate they thought various acts of violence against the treacherous classmate would be.

Findings from this study indicated a clear difference in aggressive responses between the genders, with women overwhelmingly compelled to retaliate by attacking the offender’s reputation, mostly through gossip. This gender effect panned out even after controlling for participants’ evaluation of the social appropriateness of such acts. In other words, in spite of the fact that the women realized malicious gossip wasn’t socially appropriate, this was nevertheless their preferred first point of attack. Men, on the other hand, were more evenly divided in their response, but failed to show the same preferential bias for acts of “informational warfare” against the unlikable classmate.

Although most researchers acknowledge the somewhat speculative nature of evolutionary arguments in this area, female social aggression among reproductively viable females is usually interpreted as a form of mate competition. Hess and Hagen, for example, suggest that the sex differences uncovered in their study would likely have been even more pronounced in a younger group of participants. Evolutionarily, historically and cross-culturally, they point out, girls in the fifteen- to nineteen-year-old range would be most actively competing for mates. Thus, anything that would sabotage another females’ image as a desirable reproductive partner, such as commenting on her promiscuity, physical appearance or some other aberrant or quirky traits, tends to be the stuff of virile gossip. Also, the degree of bitchiness should then demonstrate a sort of bell-shaped curve over the female life course. On the surface this seems mostly true. Anecdotally, I can’t think of a single postmenopausal woman who seems hell-bent on undermining another woman’s dating life—unless, perhaps, that involves spreading rumors about the sexual rival of her fertile daughter, in whom she has a vested adaptive interest. Then I can actually give you a name. As with most overarching research questions, though, there are many empirical studies yet to be run on the peculiar nature of female social aggression.

And I should say, if you’re still unconvinced and you’ve any doubt about acts of social aggression occurring in practice, have a gander at the current topics of ongoing conversation among the girls of Jezebel.com.

Editors' Note, 5/29/09: For a response to the concerns raised in the comments, see Women Really Are More Socially Aggressive than Men (With Apologies to Jezebel.com).

In this column presented by Scientific American Mind magazine, research psychologist Jesse Bering of Queen's University Belfast ponders some of the more obscure aspects of everyday human behavior. Ever wonder why yawning is contagious, why we point with our index fingers instead of our thumbs or whether being breastfed as an infant influences your sexual preferences as an adult? Get a closer look at the latest data as “Bering in Mind” tackles these and other quirky questions about human nature. Sign up for the RSS feed or friend Dr. Bering on Facebook and never miss an installment again.