Researchers asked nearly 800 children, from 8 to 12 years old, about whether they had witnessed violence at school, in their neighborhood, at home, or on TV. They also asked the participants if they had been a victim of violence with questions like "How often has somebody hit you at home?" The survey also measured responses to whether aggression was appropriate, such as in the statement: "Sometimes you have to hit others because they deserve it." The final section of the questionnaire measured how aggressive the child was, based both on their own report and what their classmates said about them.

Six months later, they surveyed the children again, asking the same questions. This allowed them to test whether witnessing violence -- or being a victim of it -- led to higher levels of aggression half a year later.

The schoolchildren who had witnessed violence were more aggressive. Witnessing violence also had a delayed effect -- observing violence at the first phase of the study predicted more aggression six months later, over and above how aggressive the children were in the beginning.

The same effect occurred for being a victim of violence. Victimization at the first phase of the study was associated with more aggression six months later, even given the high levels of aggression at the study's start.

The increased aggression was caused in part by a change in how the children thought that violence was normal. Seeing violence -- at home, school, on TV, or as its victim -- made it seem common, normal, and acceptable. Thinking that aggression is "normal" led to more of it.

"Exposure to violence can also increase aggression regardless of whether at home, at school, in or in the virtual world of TV, regardless of whether the person is a witness or a victim," the authors wrote. "People exposed to a heavy diet of violence come to believe that aggression is a normal way to solve conflict and get what you want in life. These beliefs lower their inhibitions against aggression against others."

The research team was headed by Izaskun Orue of University of Deusto in Spain, and included Brad Bushman of Ohio State University, and researchers from The Netherlands and Germany.

Note: If no author is given, the source is cited instead.

• Children's Health
• Accident and Trauma

• Anger Management
• Child Psychology

• Popular Culture
• Conflict

• Cyber-bullying
• Dog attack
• Self-esteem
• Bullying
• Aggression
• Child abuse