I think it's more so 'body language'. Everyone speaks not just with words. And sometimes we can send off a message by our actions and movements. Body language is just as important if not more, then talking. Some can say one thing, yet you can completely see that their body is saying the opposite.
People can't help the way they send out a certain message by their body language. Sometimes they may even be completely unaware, until someone brings
it to their attention.
I don't really think there is a technique in it though. You just have to watch people for a while, watch their movements that coincide with their
words. Do they match? If someone says they aren't nervous, yet their foot is swinging back and forth 90 miles an hour, then ask them why they seem
nervous, yet insist that they aren't. Touching is a big clue that someone could be fond of you. Crossing their arms could mean they don't agree with
you. Not looking in your eyes while they are talking could mean they are intimidated by you and or nervous, because they are lying or uncertain with
what they are saying *course it could also mean they have vision problems* Just sit back and observe people, you will soon see what they are saying
and feeling without them even opening their mouths.