Have you ever noticed a potential employer mirror your body language in an interview? This should have made you feel at ease because mirroring the body language of someone else is an indication that what they are saying is understood and compelling to the listener.
Here are a some basic signals:
1) When someone crosses his or her arms across the chest, he or she is saying something powerful. If the person is uncomfortable, this is his or her way of creating a barrier. He or she might also look around absently or purse his or her lips.
Look out if he or she is leaning away from you with a harsh or blank facial expression because this is a demonstration of outright hostility.
On the flip side, if the conversation is amicable, this signal means that a person is thinking deeply about what is being discussed…or maybe he or she is just cold. Look for huddling or arm rubbing, which would signify the latter.
2) Eye contact. I’m not going to pretend that this signal is in any way straightforward. It can indicate trust or distrust. It is culturally variant. People with certain psychological disorders don’t make it. Like any other signal, it is just a piece to the puzzle that might help indicate what someone is thinking.
If someone has his or her arms crossed, as described above, eye contact might be an indication that something is bothering him or her, and that he or she wants to talk about it.
When someone is fiddling with something, even when making eye contact, this usually means that their attention is elsewhere.
3) If the eyes and head are both tilted down, this is usually a good indicator of shame.
4) Boredom can be indicated by the tilting of the head, but be careful because this may also be an indication of interest. Ever seen a dog tilt its head? That means its intrigued. Look for extended eye contact and still posture to confirm interest.
A much better, but harder to catch indicator is the eyes. If a person’s eyes become unfocused during conversation, you are boring them.
5) You can usually tell that someone is being deceitful if they touch their face a lot during conversation and blink excessively. Interestingly enough, a lack of blinking is actual a more reliable indicator.
Lie detection is a complicated subject and will be discussed more in-depth at a later date.
Sources: You Say More Than You Think (Janine Driver) & The Definitive Book of Body Language (Allan and Barbara Pease)