The origin of the modern lie detector can be traced back several centuries, to early societies who sought the truth by means of a wide variety of tests, many of them ridiculous or cruel in nature. The Bedouin of Arabia forced those who lied to them to lick a hot iron, resulting in a burnt tongue. In China, a suspect was forced to chew and spit out a handful of rice powder; if it was dry, the suspect was pronounced guilty. In England a person was asked to swallow the "trial slice" of cheese and bread; if he or she could not, guilt was pronounced. Despite their primitive methods, each of the aforementioned methods operated under the assumption that some form of physiological response will occur in a guilty person. The mouth will be dry and the throat will be constricted, for example. The first scientific...