Are children poor liars? Do you think you can easily detect their lies? Developmental researcher Kang Lee studies what happens physiologically to children when they lie. They do it a lot, starting as young as two years old, and they’re actually really good at it. Lee explains why we should celebrate when kids start to lie and presents new lie-detection technology that could someday reveal our hidden emotions.





  • school principal –  the teacher with the greatest responsibility for the management of a school
  • peek – a quick or furtive look
  • transgression – an act that goes against a law, rule, or code of conduct; an offence
  • differentiate – recognize or ascertain what makes (someone or something) different
  • fleeting – lasting for a very short time


Think about it

Answer the questions below. Pause at times indicated in brackets. 

  • What three beliefs does the story present? (1:50)
  • What conclusions did they reach after conducting the study? (3:31)
  • What are two most important ingredients of good lying? (5:00)
  • Which child is lying? Were you right? (6:26)
  • Who is capable of detecting children’s lies? (8:24)
  • How can we spot is spot is someone is lying? What physical symptoms occur when someone is telling a lie? (11:10)
  • What are some other applications of transdermal optical imaging technology?


Practice makes perfect

Fill in the blank spaces with the missing words. Use ONE word per blank space.

We have been playing guessing games with children ________ over the world. Here is ________ example. So in this game, we asked children to guess the numbers ________ the cards. And we tell them ________ they win the game, they are going to get a big prize. But in the middle of the game, we ________ an excuse and leave the room. And before we leave the room, we tell them not to peek ________ the cards. Of course, we have hidden cameras in the room to watch their every move. ________ the desire to win the game is so strong, more than 90 percent of children will peek as ________ as we leave the room.


We found that regardless ________ gender, country, religion, at two years of age, 30 percent lie, 70 percent ________ the truth about their transgression. ________ three years of age, 50 percent lie and 50 percent tell the truth. At four years of age, more than 80 percent lie. And after four years of age, most children lie. So ________ you can see, lying is really a typical part of development. And some children begin to tell lies ________ young as two years of age.


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