Our brains are geared to respond to external threats. These threats could be anything from someone pointing a gun at you to lying about an extramarital affair.  In both examples, you perceive a threat and your body prepares you to either run away or fight. In both situations, you have something to lose and your body will physically respond to the threat. Within the realm of polygraph, the examination is based on psychological theories and physiological changes that occur when a person "tells a lie." Without going into a historical background, the foundation of polygraph (lie detection, truth verifier) is based on the psychological theory of "fight or flight." What about non-verbal clues to lying? I recently discussed non-verbal clues of lying with a fellow polygraph examiner. I have great respect for this individual, but in the end we agreed to disagree on several issues. The cultural background of individual plays a tremendous role in the use of polygraph. Let me provide you a few points from our discussion. Bear in mind that some of the following information is based on psychological/sociology studies and/or personal experience.

1. People who lie will not look you in the eye. Culturally, Latin and Asian nationals find it rude to stare at someone. In conversation, many will look around, occasionally make eye contact, but find it disrespectful to continuously "look you in the eye." Looking at someone in the eye as a means to firmly communicate and ensure they are receiving your message is part of the North American/European cultural. "I can't trust you if you don't look me in the eye." Remember that this isn't the case in all cultures.
2. People who lie pause before answering a question since they are trying to come up with a believable lie. Actually, many people pause before answering a question. The reasons vary from trying to understand the question to actually translating the question from one language to another. My first language was Spanish and I sometimes annoy my wife because I will occasionally translate her question in my mind before I formulate my answer. Pausing before answering may be a habit, a translation process or a method of actually trying to understand a complex question.
3. People who lie lower their tone/voice. Many Asian nationals will speak in a low tone when they first meet an individual from another country/culture It's a way to assess the individual and situation. It's a non-threatening mechanism that is used to communicate without appearing rude.
4. People who lie will ask you to repeat the question. I'll go back to #2 Sure, it's possible if an individual is attempting to provide you with a plausible lie, but what if the individual is just trying to understand the question or its meaning.  A hearing impaired individual may need to repeat the question to insure they have heard the question correctly.  People who speak English as a second language may need to repeat the question as well.  (I'll discuss communication issues such as sender-receiver-was the meaning of the message conveyed in another document.)

As a polygraph examiner, I need an understanding of the examinee's cultural background.  The common stereotypes we hold need to be reviewed before entering the polygraph examination room.  Many years ago I coauthored a paper for a Federal Agency on interviewing individuals from the Middle East.  My research into the subject convinced me to throw out my stereotyping and generic approach to individuals taking a polygraph. Polygraph is an effective tool, but many factors must be considered.  In our multi-cultural society, our old perceptions and methods need to change to account for the differences between cultures.  Myths about lying and liars need to be debunked. 

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