Signs of psychopathy can be observed in children as early as age three or four but that doesn't mean they will develop into problem behaviours later in life, according to a University of Montreal professor.

Sheilagh Hodgins studies the development of serious mental disorders and antisocial disorders.

Recently, an expert witness testified at the sentencing hearing for the killer of Hannah Leflar that the accused, who was 16 at the time of the killing, displayed psychopathic tendencies.

Hodgins told CBC Radio's The Morning Edition that about four per cent of boys and one per cent of girls will have observable conduct problems. Among those groups, a smaller group of children will show callousness.

"They don't get upset when they're told their behaviour is bad. They don't learn from punishment," she said of the types of conduct.

"They lie. They are sneaky and they are selfish." 

The problems get harder to address the older a person gets, but Hodgins said if programs targeting the behaviours are funded, progress could be made — even with adults.

Genetics and experiences growing up factor into behaviour but so does parenting, she said.

"Parenting contributes to promoting conduct problems and also to reducing them," she said. 

Bad behaviour should be punished, but appropriately and proportionately, she said. Harsh parenting will promote conduct problems and callousness.

"We know that parents can effectively change their behaviour and the behaviour of their child," she said.

Taking appropriate measures once the signs are recognized can go a long way in remedying the behaviour, she said, but the services available depend on the provinces. 

"All the evidence suggests we need to make them far more accessible," Hodgins said.

"Get help. Don't try to take it on your own shoulders."

With files from CBC Radio's The Morning Edition