The effects of ostracism can be just as harmful for the persecutor as they are for the victim.

It’s hard to feel sympathy for the mean girl, the one who decides who’s “in” and who’s “out.” It’s a common theme in pop culture, made popular by the likes of Queen Bees and Wannabees, which inspired the hit movie Mean Girls.

But new research suggests that Regina George needs empathy, too. By ostracizing others, both the ostracizer and the victim face negative emotional and psychological consequences. While it seems counterintuitive, “when people comply in harming, they too suffer,” says Nicole Legate, lead author of the Psychological Science paper and a doctoral candidate at the University of Rochester.

Much research has already been done on the effects of exclusion on the victims of ostracism, which can cut so deep as to make them feel less than human. But the act of excluding others can cause just as much pain, albeit in a different form.

“In real life and in academic studies, we tend to focus on the harm done to victims in cases of social aggression,” said study co-author Richard Ryan, professor of clinical and social psychology at the University of Rochester. “This study shows that when people bend to pressure to exclude others, they also pay a steep personal cost. Their distress is different from the person excluded, but no less intense.”

A group of undergraduates played the online game Cyberball, which has been used in many studies to observe the effects of ostracism within groups. The participants played the virtual ball game with other “players” whom they were led to believe were real people.

However, the game had been pre-programmed to share the ball equally or to exclude a player after sharing the ball twice. Each participant was put into a game scenario. The ostracizer group was programmed to exclude a virtual player, and the real-life participant was told to also exclude that same player. Next, the game prevented certain players from participating, leaving them to watch the others pass the ball to one another.

Participants were also given instructions about with whom they could share the ball, and whether they could share it freely. Those who were made to exclude others experienced the most distress.

When comparing the results of surveys assessing participants’ moods and before and after the study, researchers noted that people who were ostracized felt worse about themselves and their abilities. “Although there are no visible scars, ostracism has been shown to activate the same neural pathways as physical pain,” says Ryan.

There are many ways to make someone feel left out, and this study highlights only a few of the ways ostracism poisons interpersonal relationships.

“Ostracism broadly refers to a group or an individual excluding or ignoring someone, and this can happen by not talking to someone in a group, not throwing the ball to them in a game, and even in more subtle ways, such as lack of eye contact,” Legate said.

The effects on someone who is ostracized might be more obvious than the effects on those who do the excluding, but all people crave a sense of belonging, even when it seems they are the ones ignoring or excluding others.

“Pressure to exclude others is all too common, particularly among girls,” the researchers explained. “People may face requests to ostracize someone for personal reasons (e.g., a friend’s request to ostracize a romantic rivalry) or prejudice (e.g., a peer’s request to ostracize a target perceived as gay).”

Furthermore, Legate adds, such behavior in young people could have even more serious consequences down the road.

“Research in developmental psychology has demonstrated the long-term effects being a social aggressor,” she said. “[F]or example, social aggression in childhood is an important predictor of later social and psychological adjustment problems.”