understand the theoretical perspectives the kind of underline lie detection. And the first

one is emotion. So essentially what we do is we experience three kinds of emotions when

we lie, and the first one is fear. All right. So fear of being caught. The second one is

guilt, guilt for lying, and the third is delight, delight for getting away with it successfully.

So those are the three emotions. Now these are the problems. There's only non-verbal

behaviors that are correlated with these emotions. Just because you see those behaviors, it doesn't

necessarily mean that you know if the person's lying or not. So for example, a guy can get

home late from work and, you know, his wife, he walks into the front door. And his wife's

like," Honey, where were you?" And he starts to stutter, and he's like, and gives all these

weird non-verbal, something's off. He's like, "I'm so sorry. I, I, I was late at work."

And his wife knows, "All right. Something's up. I think he's lying." She doesn't know

the source of the lie. So she may jump to the conclusion that he's cheating on me. You

don't know that. All you know is there's something wrong. There's something up.

So we can spot emotion, but we don't know the reason why the person's having that emotion.

And that's the problem is that we can see that somebody's fearful, or we can see that

somebody seems guilty in that conversation. Right? But it doesn't mean they're lying.

They could be guilty because of a wide range of reasons. So we can't just, you can't just

look at a non-verbal and be like, "Liar." You have to look at a non-verbal, look at

the emotion, and then kind of deduce whether or not the person's lying or not. The second

thing is what's called cognitive overload. Now cognitive overload is very interesting.

It basically means that when we lie, we require more cognitive facilities than when we tell

the truth. So basically lying is more demanding than telling the truth. And because lying

is more demanding, we tend to reduce the amount of behaviors we make.

So one of the things we'll tend to see is that in really animated people who move their

hands a lot, when they lie they're less likely to move their hands. So I do a cool little

study at my office where I get people to arrange a deck of cards, like put all the fours, you

can try this. Put all the fours together. Put all the fives together. Put all the sixes

together. Try doing that while telling a real story. And then try doing that while making

up a story. When you make up a story and do that, you have a hard time doing it, because

all of your cognitive processes are going towards the lie. So it's a very useful way

to see when people reduce movement. Because it's basically because they're lying, because

they're putting so much more effort into lying, they can't pay attention to other things.