Is it true that as soon as kids learn how to talk, they learn how to lie?

The answer seems to be yes, according to research conducted by Brock University scientists in Canada. What’s more, it seems that the ability to lie correlates with cognitive development.

In other words, lying is a developmental milestone, although probably not one parents would be proud of. The ability to lie is connected with the ability to recognize self-interest, which leads to lying to either gain something or avoid some particular negative outcome.

During an experiment published in Developmental Psychology in 2013, a researcher instructed a group of children not to peek at a hidden toy. The children, ages 2 to 3, knew the location of the toy.

The researcher deliberately gave the kids the opportunity to sneak a look. About 80 percent of the children couldn’t resist themselves and peeked.

Of those who peeked, about 40 percent lied about it when asked, while the rest confessed their transgression quickly. Older children tended to lie more as compared to younger kids, but some of the children who lied were as young as 2.

Most 2-year-olds were still very honest, but the researchers explained that was because they hadn’t learned how to lie yet. Within a year, kids become more likely to lie about their actions because they perceive some advantage to doing it.

Fortunately (at least for the parents), kids who knew how to lie still had trouble maintaining the deception. For example, the kids who lied about peeking went on to describe the toy they supposedly didn’t look at.

An important distinction should be made between a true falsehood and imaginations. Children at that age easily confuse fantasy and reality. For the experiment, the researchers were careful to make that distinction.

By the age of 4, kids understand what lying is, and they understand it’s wrong to tell a falsehood. So a 5-year-old who blames his infant sister for that painted wall knows exactly what he’s doing.


  • Lying is connected to either gaining something or avoiding something with a negative result.
  • During a study, many 2-year-olds were able to lie, although they didn’t understand what they were doing was lying.
  • Preschoolers tend to know what lying is and that it is wrong.

Last reviewed by Eva Benmeleh, PhD. Review Date: September 2020


  1. American Academy of Childhood and Adolescent Psychiatry. Children & Lying.
  2. National Institutes of Health. Emergence of Lying in Very Young Children.


  1. I read recently that telling kids this phrase tends to curb lying in children: “I will not be upset with you if you [did whatever it was], and if you tell the truth, I will be really happy.” It’s supposed to speak to kids desire to please the parent!

  2. I have noticed my 3 year old telling little white lies here and there. They aren’t anything serious, but I still make it a point to correct her when necessary. We talk about the importance of telling the truth and how to be honest. I try to tell her what she should do, rather than focusing on what not to do. And now for my confession- I would sneak a peek too-lol! I wouldn’t be able to resist the temptation!


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