Step 1 : Introduction to the question "1. What is meant by the word polygraph?"
...1. electronic calculator 2. lie detector 3. dental chart 4. library indexing system A polygraph is a lie detector, a machine that measures the responses of a person undergoing questioning, normally a suspect in a criminal investigation, or sometimes for employment-related security clearance purposes. It measures blood pressure, breathing and sweating, all of which are bodily responses that are believed to alter when the interrogee is lying. It is not used in all countries, but is used in some, including some American states, although taking the test is not compulsory. The polygraph was invented by John Augustus Larson of California in 1921.
