Lying - Sweaty palms

Ever experience sweaty palms in the midst of telling a lie... It just happens, you literally have no control over how your body reacts biologically. 

According to body language expert Jack Claridge sweaty palms aren't always noticeable to the person who is being lied to but the symptom is there.  It is caused by the a rise in the liar's metabolism as they lie, which in turn causes their heart rate to increase.  Sweaty palms are one of the mehods that are used by a Polygraph Machine (Lie detector).

How do lie detectors work?  

Their primary function is to determine if a person is lying or telling the truth by answering some specific questions related to the specific context of the situation.

In the picture we can see that four to six sensors are attached to him. A machine called a polygraph uses multiple "poly" signals from the sensors that are recorded on a strip of moving paper (graph).  Sensors usually recorded are:

• Breathing rate
• pulse
• blood pressure
• perspiration
• sometimes arm and leg movement

As the test is put into progress the questioner will ask a few simple questions to determine the norms for the person's signals.  After this the real questions that will be asked is being tested by the polygraph.  The person's signals will be recorded throughout the questioning period.

During and after the test has taken place a polygraph examiner will look at the graphs to see whether the vital signs changed significantly on any of the questions that were asked.Put into general, a drastic change (like a faster heart rate, higher blood pressure and increased perspiration) indicates that the person is indeed lying.

A polygraph test is not perfect but can be fooled, because an examiner's interpretation is subjective and because different individuals react differently to lying...