This book points out a lot of ways to determine if a person you are talking to is under stress, how to identify exactly what part of what you are saying is causing stress, and how to lead that to determining what the stress is about with regards to that part.  The author points out many times that the techniques will indicate stress much more than they will indicate deception.  Deception is only one thing that will cause stress.  The biggest thing the author says is an indicator is a change in behavior.  The behaviors themselves can be normal, even if they seem strange, but a change in a behavior is indicative of something no matter what kinds of behaviors are normal for a person.

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