How does body language work? 

We have two brains in one: the rational one and the emotional one. The rational tries to control the emotional, and the emotional fights back. The emotional brain is faster, and sincere. The rational is slower and able to cheat, to lie. The emotional brain is not able to lie. It controls body language. So body language doesn’t lie. We can lie with words, but never with our body.

The blue area is the emotional brain, and the rational brain surrounds it.