Have you ever successful detected any kids lying? At least in this talk, I failed for the one example he introduced. 

The speaker has been studying how children learn to tell lies for the last 20 year. At the beginning, he gave one example that one kid called teacher to take one day off and he said to teacher that he was his father.  

How do you think below three beliefs are true??

1) children only come to tell lies after entering elementary school

2) Children are pop liar. Adults can easily detect their lies.

3) If children lie at a very young age, there must be some character flaws with them. 

Turns out, all of the three beliefs are wrong. 

They have been playing guessing games with children and tell them if they win the game, they are going to get a big prize. After they left, the monitered with hidden cameras and they found that 90% children peeked as soon as they left the room. 

They found that 30% children lie when they are two years old. At three years of age, 50% lie and 50% tell the truth. At four years of age, 80% lie. After four years of ago, most children lie. 

He mentioned two key ingredients to make good lying. 

1) theory of mind, or the mind-reading ability. The bail for this is I know you don’t know what I know. 

2) self-control. It is the ability to control own speech, own facial expression and body language. 

They found that young children who have more advanced mind-reading and self-control abilities tell lies earlier and are more sophisticated liars. 

So he said if you discover your two years old kid is telling first lie, you should celebrate, instead of being alarmed. Because it signals that your child has arrived at a new milestone of typical development.

Also the researches found that the children are not poor liars. 

Many different professionals cannot really detected whether children lie or not, even their own parents. 

At the end, he introduced the new development - trying to figure out a way to reveal hidden emissions behind a liar. Underneath our facial skin, there’s a rich network of blood vessels. When we experience different emotions, our facial blood flow changes subtly. These changes are regulated by the autonomic system that is beyond our conscious control. They can reveal people’s hidden emission by look at facial blood flow changes. A new imaging technology “transdermal optical imaging” - has been developed by them. 

The accuracy of this technology was at about 85%. 

They found that when people lie, the facial blood flow on the cheeks decreases, and the facial blood flow on the nose increases. 

Except lying, it can be applied in other situation. For example, it can help mathematics teacher to identify the student who may experience high anxiety about the topic he is teaching. Also it uses in health care, or even in politicians.