Through surveys at a Midwestern middle school, conducted early and late in the academic year, lead investigator Dorothy Espelage found that kids who hang out with peers who bully, both boys and girls, tend to do more bullying themselves. Bullying behavior was defined as teasing, harassment, rumor spreading and social exclusion.
The study of middle-school aggression appears in the January/February issue of the journal Child Development.
The same peer effect held true for physical fighting, but was not nearly as strong, said Espelage, a professor of educational psychology at the University of Illinois at Urbana-Champaign.
The findings fit with what researchers call the "homophily hypothesis," which holds that individual behavior is influenced by the groups they're part of.
"This is the first time that we can actually show that the homophily hypothesis holds for both bullying and fighting (among early adolescents), but it is much stronger and explains much more about bullying," Espelage said. "The study shows that for bullying there was a significant peer group process."
As in other studies, by Espelage and others, she found that even when individual students engaged in little or no bullying, they often stood on the sidelines and rarely intervened. They appeared to largely accept it as part of the culture or climate, as "just how things are," she said.
The study was conducted during the 1999-2000 school year at a rural and largely white middle school (grades 6-8) with about 475 students. The first survey, early in the school year, included 422 participants, and 384 of those participated again in the spring. In both surveys, the participants were about 51 percent girls and 49 percent boys.
Students were asked about their own behavior, as well as that of their peers. They also were asked to name the kids they hung out with the most, as well as those they thought often teased and picked on others, and those who were the victims of that teasing and harassment.
The researchers then did extensive analysis to determine the students' social networks, and matched that with the behavior of individual students, as reported by themselves and their peers.
"What the study says is that for bullying-prevention programs we really need to consider this tendency of kids to go along with the group, even when they know it's very hurtful behavior," Espelage said. Very few of the programs being used take the peer group into account, she said.
The co-authors on the study were Melissa Holt, a doctoral student at the time of the study, now at the University of New Hampshire, and Rachael Henkel, who was an undergraduate research assistant.