27/02/2017 08:23 GMT | Updated 28/02/2018 05:12 GMT

This Is the Number One Way To Spot A Liar, According To A Former Special Agent

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What are some good signs to watch for when reading nonverbal signals? originally appeared on Quora - the knowledge sharing network where compelling questions are answered by people with unique insights.

Answer by Chris Voss, author of Never Split the Difference, CEO of The Black Swan Group, on Quora:

The #1 nonverbal signal to look for is a change from baseline. This is actually the way a polygraph works. People being interviewed are hooked up to quite a few probes that are designed to detect a number of physical changes: changes in breathing, head movement, eye and head movement, hand gestures etc. The interviewees are then given a number of simple questions to determine a baseline of when they are telling the truth; for example, the tester might ask the interviewee some questions for which the answers are easily verifiable.

"What did you have for breakfast?"

"Where did you grow up?"

"What did you like about where you grew up?"

If, while they are answering, a change is detected anywhere, then the person is likely practicing some form of deception. This could correlate to a weakness in position that he or she is trying to cover up. If the hands are covering the mouth as a response to a question, this is often a sign of discomfort with the answer, and therefore possibly indicates deception.

The flip side might be asking the person something you know they'll be caught off guard by and know they aren't completely sure of the answer for:

"Do you have complete authority to make a deal?"

Since no one has complete authority, the respondent likely just gave you their first (and go-to) tell, or a physical move that is "telling" about a lie or some sort of deception.

There are a number of common tells indicating someone is lying, but not common enough to be sure with each person. There is a great Jimmy Kimmel episode that I show a lot of my clients and students called Lie Witness News. It shows the 4-5 most common ways people lie. Each person night even manifest a different way, depending on the circumstances.

Despite the variety of ways people might lie, for the most part everybody has only one way that they as an individual tell the truth, if they tell the truth. Get a sense of that and then look for physical changes to indicate deception. If you ask a question and receive an answer that you know isn't true, and you see no change, that may mean they're deceiving all the time. This is good information to know as well.

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