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.

"There's something that happens, though, when the mob forms," said Patti McDougall, a developmental and educational psychologist at the University of Saskatchewan.

"And so that tells me, or that would suggest that the reasonable, rational part of your decision making has gone out the window."

Watch the video of Halcrow's attack:

Bonnie Halcrow says she was attacked when she began recording a group of young boys throwing rocks at an older man. It happened Monday in Pleasant Hill Park in Saskatoon. 0:26

McDougall said she was shocked and horrified when she viewed a video of a group of children kicking, hitting and dragging Manitoba woman Bonnie Halcrow at the Pleasant Hill Park on May 20.

Physiology can take over

A 13-year-old girl has been charged with one count of assault after the attack. She is also facing another assault charge over a different incident, in which two girls aged 10 and 14 said they were assaulted at the same park a week earlier.

Police said an unspecified number of children have been identified as being involved in the attack, but they will not be charged because they are younger than 12.

McDougall said she believes any child, in the right conditions and context, could behave terribly.

University of Saskatchewan developmental and education psychologist Patti McDougall believes more supervision, not necessarily from police but from adults, could improve child behaviour in the Pleasant Hill area. (CBC)

She said there are situations where physiology or adrenaline can take over rational thought.

"We know that in this case, to see that unfold would suggest that there was a huge degree of impulsivity and they completely disengaged from any rational decision making," said McDougall.

'They build on each other's aggression'

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.

Like McDougall, Pepler thinks the young people in the Saskatoon video might not behave the same way outside of the group.

"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."

Debra Pepler, a distinguished research professor at York University in Toronto, was not surprised by what she saw in the Saskatoon video. (CBC News)

She said the feeling the child has is like "stepping into an action film," and the excitement they feel reinforces the bad behaviour 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.

For the children involved in the Saskatoon attack, McDougall said it will be important to assess their individual needs as a response to the incident.

Community should talk about increasing adult presence

She said an increased adult presence in the area, not necessarily by police but also the community, would be a deterrent to the children and one way to approach community safety.

"We know that added supervision and even the perception of monitoring can have an impact on behaviour," said McDougall.

"So the mere presence of adults and the belief that ... you're accountable to those people, and that you need to monitor or alter your behaviour accordingly — that can make an impact.

"That's something that community needs to be talking about."

With files from CBC's Bonnie Allen