Bullying is common in classrooms around the world: About 15 percent of children are victimized, leading to depression, anxiety, loneliness, and other negative outcomes. What's driving bullies to behave the way they do? According to a new large-scale Dutch study, most bullies are motivated by the pursuit of status and affection.

The longitudinal study was conducted by researchers at the University of Groningen in the Netherlands. It appears in the March/April 2010 issue of the journal Child Development.

In their work, the researchers questioned almost 500 elementary-school children ages 9 to 12. Based on their findings, they conclude that bullies generally choose to gain status by dominating their victims. But at the same time, they try to reduce the chances that they'll end up on the outs with other classmates by choosing as victims children who are weak and not well-liked by others. In short, even bullies care a lot about others' affection and don't want to lose it.

Gender also plays a role. For example, the study finds that at this age, bullies only care about not losing affection from classmates of their own gender. So when boys bully boys, it doesn't matter whether girls approve or disapprove. The same holds for girls. Moreover, boys will bully only those girls that aren't well liked by other boys, regardless of what girls think about it, and girls will do the same in their bullying of boys.

"To understand the complex nature of acceptance and rejection, it's necessary to distinguish the gender of the bully, the gender of the target, and the gender of the classmates who accept and reject bullies and victims," according to René Veenstra, professor of sociology at the University of Groningen, who led the study.