All kids try to lie. But, as any parent knows, they’re really not very good at it when they're young. So why do youngsters pick up the lying habit and when do they first start trying to tell a fib? Canadian researchers have discovered some surprising answers.

Psychologists Kang Lee and Angela Evans, from University of Toronto and Brock University respectively, have discovered that kids start figuring how to lie at the tender young age of about two years old. That’s much younger than experts had previously thought.

“Our study is the first to examine two-year-olds’ verbal deception – so their lie-telling behaviour – and we are the first to show that two-year-olds will indeed tell lies,” Evans told CTV’s Canada AM Wednesday.

To study when lying starts, Lee and Evans gathered 41 Canadian two-year-olds and 24 three-year-olds and asked them to take part in a guessing game. In the game, a toy was placed behind the child’s back and its sound played. The kids were asked to guess what the toy was. If the toy quacked, for instance, the child knew it was a duck.

After two toys, the adult leading the game then placed the next toy behind the child’s back and said they were going to the other side of the room to get something. The adult told the child not to look back at the mystery toy while they were away.

The researchers then watched through hidden cameras to see whether the children peeked, and to see how they reacted with the adult returned to the area and asked, “Did you look at the toy while I was gone?”

A full 80 per cent of the children couldn’t resist the temptation to peek at the toy – perhaps not surprising when you consider children’s undeveloped impulse control. But when the adult asked the children if they had looked, 40 per cent of the “peekers” lied. And, in a surprise to researchers, fully a quarter of the two-year-olds were among those who tried to lie.

The results appear in in the journal Developmental Psychology.

Prof. Lee, who specializes in the study of lying at the Dr. Eric Jackman Institute of Child Study, says most parents hate when their children lie, but it’s actually an indicator that their child is developing sophisticated reasoning and problem-solving skills.

“Lying is quite a normal behaviour. Most of us lie at some point in our life,” Lee says.

“And actually, in order to lie you have to have certain ingredients to be able to do that. One of them is the ability to think of other people’s minds. When you realize, ‘I know something you don’t know,’ only then can you lie. So if a child lies, it tells you the child has reached a milestone in their development,” he says.

Lee thinks there were a couple of reasons why so many of the children lied in his study. One of them is that the children knew that they had violated the rules and wanted to cover it up.

Another reason might have been that they wanted to get the question right so they could please the adult.

But the study also revealed where things go wrong with beginner liars.

As a final test, the adults asked the lying children if they knew what the toy was, even though the toy had yet to make a noise. Of the 21 liars, 16 revealed that the toy was a teddy bear. Three of the children concealed their lie by insisting they didn’t know, while two refused to answer the question.

Lee says it’s interesting that so many of the children failed to cover up their fib by blurting out the right answer.

“So they are telling lies, but they are not yet good lie-tellers,” he says.

Evans says her team’s previous research suggests that the rate of lie-telling increases as a child ages and as he or she figures out how to do it.

“So by four years or age, 80 per cent of children will lie in that kind of situation,” Evans says. “That’s maintained through childhood. Then, we’ve found that in adolescence, there’s a decrease in lying behaviour. So about 40 per cent of adolescents will lie in a similar situation.”

Lee says it’s important for parents to remember that experimenting with lying is a pretty normal thing for a kid to do.

“If your child lies, it is not a sign that they will develop into a sociopath or a pathological liar. It’s actually a sign that they’ve reached a normal developmental stage,” he says.

Yet while parents shouldn’t be alarmed by lie-telling, at the same time, they shouldn’t just let it pass.

“We should use it as a teachable moment so we can talk to a child about what is a lie, what is the truth and what is your expectations for them,” he says.