Exercise in Humiliation

"You're a freak and a nerd! No one likes you, and you have no friends!"

It's the kind of cruelty for which teenage girls are famous. If you're a woman, perhaps you remember just how traumatizing it can be to find yourself the victim of a group of mean girls.

"You're such a LOSER! You smell and you'll never have a boyfriend!"

So, if you were taking a stroll through the park, and you encountered three teenage girls viciously insulting and picking on another girl, what would you do? Is it your job to step in, or should you keep your distance?

CLICK HERE for more reactions caught on tape!

Girl Bullies vs. Boy Bullies

ABC News decided to see how people might react to such a scenario. We hired four teenage actors: three "mean girls" and a victim. Then we went to a busy suburban New Jersey park and, on a park bench over the course of a few days, the girls bullied each other and waited to see how people would react.

The mean girls berated their victim about her looks and social status. They told her she smelled, she was stupid, and she had no friends. These kinds of painful insults and much, much worse, are hurled at kids every day in schools across the country. In a 2005 Department of Justice study, 28 percent of U.S. students, age 12 to 18, said they'd been bullied at school.

We were particularly interested in understanding the difference between the way boys bully and the way girls bully. Two years ago, ABC News tried the same experiment, except that the actors were young boys, and their bullying was mostly physical. When bystanders witnessed the bullying, both men and women stepped in to stop it.

This time, ABC News asked the girls to stick to verbal abuse. We wanted to know if people would be more or less likely to get involved if the weapons were words instead of punches. Do people perceive verbal abuse as "dangerous" as physical abuse?

'Does Humiliation Mean Nothing?'

Studies show that, while girls use more indirect forms of aggression than boys, such as spreading rumors or pressuring peers to reject or exclude a victim, girls' self-esteem and school performance is affected just as much as when the bullying is physical. In fact, verbal and emotional bullying can hurt a teenage girl even more than a physical conflict.

During the experiment, our production team watched the action on monitors from a nearby van, along with Rosalind Wiseman, an internationally-known social justice educator, and best-selling author of "Queen Bees and Wannabes," the book on which the movie "Mean Girls" was based.

The first thing we noticed was that, when many men spotted the bullying, they watched but kept on walking. One man told us that, because he didn't see anything physical going on, he decided not to intervene. But Wiseman was quick to point out that the damage to a teenage psyche is just as real when the weapons are words.

"Why do we have to wait until it gets physical to do something about it?" she asked. "Does humiliation mean nothing? It's ... the seeds of what happens when kids do get physical."

Women, on the other hand, seemed more willing to get involved. Maggie Murphy passed by the scene with her friend Kathleen Deutsch and their children. Deutsch yelled at the bullies to leave their victim alone. Then, the women walked away. But Murphy came charging back a few minutes later, and joined another woman, Lillian Levy, in setting the mean girls straight.

'You're Such Losers!'

"You're being so evil and mean! When you grow up, you're going to be ashamed of the way you're acting! ... You three are very ugly, unattractive people!" yelled Murphy.

Then, she turned to Catherine Daddario, the actor playing the victim. "I'm, like, so upset for you. These are very, very evil people," she said.

We watched as one after another, women stepped up to admonish the girls.

Pat Summers asked the bullies, "Don't you have anyplace else to go?" When one of the mean girls responded, "you're not my mother!" Summers replied, "Thank God! If I were your mother, I'd knock your head off!"

Interesting patterns began to emerge. We had asked our actors to keep their language clean, so we were surprised to find out that it was the adults who were the ones cursing. But we were most surprised to find that many of the women who confronted the bullies, summoned their "inner teen" and imitated the actors, giving the mean girls a dose of their own medicine.

During Murphy's confrontation with the girls, she waved her hands in the air and yelled at them, "Oh, you guys are SO COOL!!! You're such losers, it's unbelievable!"

Lisa Stein and her husband David stepped in to help a bullied victim by yelling at the girls to stop their bad behavior. Then, Lisa imitated the bullies and said, "It's so COOL to pick on people! Oh, my GOD!"

We sensed that our girls were striking a nerve. In an interview afterward, Stein told ABC News, through tears, that she was bullied as a teenager, and she thought she might have mimicked the girls because that memory came flooding back.

We asked Wiseman why such raw emotions rose to the surface when women interacted with the mean girls? She told us she thinks it's a reflection of how intense people feel upon remembering what it was like to be a teen.

"It's like a flashback to when they were younger," Wiseman told correspondent John Quinones. "And when that happens, it can be a gift, because it can really propel you to be courageous and intervene."

Next, we met a woman who didn't let the bullies rattle her one bit. She approached our actors and calmly said, "This is something that I try to teach my children, and they're only 4 and 8 — if they want respect, they've got to give respect."

We noticed that a lot more women stepped up to the mean girls than when the bullies were boys. Our teenage actors told us they thought they knew why.

Daddario — the "victim" — told us that women "implant a little idea into your head, and it totally messes with you ... that's a skill that we hone!"

Actress Samantha Goober explained, "Boy bullying and girl bullying is so different, and I think that's why the women understand it more; because it's not just a punch in the face, and you're friends again. It's like, it's there forever."

A New Twist

But what would happen if our girls dressed in hoodies and acted more aggressively, instead of just mean? This time, the girls also threatened Daddario with physical violence, not just emotional abuse.

The result? People were much more reluctant to get involved. But those who did say something appealed directly to Daddario.

Madeline Adami approached the girls and intervened quickly, saying, "Catherine, why don't you just get up and walk away? Don't let them do this to you. It's not worth it. Walk away right now!"

John Benshoe offered Daddario reassuring words: "Don't worry," he told her after he chased away the bullies. "I've been there before ... The reason they do that is because they don't like themselves."

Confront the Aggressors

So, what's the best approach? Wiseman said it's much better to confront the aggressors than the victim. If you speak exclusively to the person receiving the abuse, "they're probably going to say, 'I'm fine, I'm fine.' Because they have to deal with the bullies later. The adults don't."

Wiseman added, "It's much more effective to actually say to the bullies, 'This is what you need to do. You need to stop. You need to walk over there. I am calling the police.'"

Which is exactly what a man named Shawn Taylor did, in no uncertain terms. He strode up to the girls, open cell phone in hand, and addressed them in a serious tone.

"Girls, I'll give you about three minutes to clear this area," Taylor instructed, as his two young children looked on. "All three, clear the area ... let's go, move it. Leave the girl alone or you'll deal with the police."

It's hard to know what to do when witnessing a public and vicious word fight involving feisty teenage girls. But no matter the age, sex or appearance of the bullies, it's important to do something.

And what if it's your child who's being bullied? Wiseman said there are three key things to say to the victim: "I'm so sorry this is happening to you. Thank you for telling me ... And together, you and I are going to work this out."

Wiseman also suggests that the parent help the bullied child decide what to say to the perpetrator, and also choose a location where the confrontation should take place.

So, who learned more, the people passing by, or our actors?

Goober told us, "I've always tried to stick up for people, and it's so hard when your friends are the ones picking on this girl. You could lose a friendship. Now, especially from this experience, I will totally stick up [for the victim], no matter what. Because seeing people just walk away, I was like, 'never again, never again.'"