Psychologists say any one of the children who attacked a 33-year-old woman in a Saskatoon park last week would likely know right from wrong if they were asked one on one.

A video of a group of children kicking, hitting and dragging Manitoba woman Bonnie Halcrow at the Saskatoon Pleasant Hill Park on May 20 had many in disbelief that children could participate in such an act of violence.

Debra Pepler, a distinguished research professor of psychology at York University in Toronto, said hundreds of hours spent observing children in playgrounds suggest there is a pattern that emerges when group bullying occurs. She said when one child initiates bullying or an attack, then another joins in, it encourages the first child to become more aggressive and excited. The result is that they think less rationally.

"It's a group of young people doing things that, in a calm way, they would know were wrong except what happens sometimes when groups of young people get together and aren't thinking is that they excite each other," she said.

"They build on each other's aggression and something that one child would likely not have done takes off with an energy that's really difficult for us to understand." She said the feeling the child has is like "stepping into an action film," and the excitement they feel reinforces the bad behavior among others.

Pepler suggested parents who are concerned their children could get drawn into a violent or bullying situation should start a conversation about it. "If this happened and you were there, what would you do?" said Pepler. "What would you do to keep yourself safe? But what would you do to stand up and say no? And it's children who have strong relationships with their parents who are able to do that."

She said children who have warm, nurturing relationships with their parents, rather than being frightened, respond better to discipline.

A 13-year-old girl has been charged with one count of assault after the attack. There was an unspecified number of children that have been identified as being involved in the attack, but they will not be charged because they are younger than 12.