Who wouldn't be tempted by a device that let you read the thoughts of your fellow citizens? And who wouldn't hesitate to be hooked up to such a device? In the early part of the twentieth century two Americans announced that they had solved the age-old quest for a reliable method of distinguishing truth-tellers from liars. The momentous announcement came from Berkeley, California, where the two men were working as disciples of the town's police chief, himself the nation's leading advocate of bringing scientific methods to police work. The first disciple, John Larson, was the nation's first cop with a doctorate, a forensic scientist of restless integrity. The second, Leonarde Keeler, was a high school-age enthusiast, with less integrity but considerably greater charm. Working first together, then at cross-purposes, they fashioned an instrument -- and a technique of interrogation -- that was hailed by the public as history's first "lie detector." To a nation obsessed by criminal disorder and political corruption, the device seemed to light the way toward an honest society. Adultery, murder, conspiracy, espionage -- the bright lamp of the lie detector would pierce the human opacity which allowed these secret vices to flourish. On the strength of this utopian ambition, millions of Americans have been hooked up to a polygraph machine that monitors their pulse rate, blood pressure, depth of breathing, and sweatiness -- and on the basis of their physiological responses during a brief interrogation, have been declared either sincere or deceptive.

Is America more honest as a result? This book tells the story of the lie detectors and their creation: a device which seemed to mimic the actions of the human soul, until, like Frankenstein's monster, it threatened to supplant its creators, even while terrifying -- and enthralling -- a nation. This is also the story of our secret selves. Saint Augustine long ago defined a lie as the gulf between the public utterance of one's mouth and the secret knowledge of one's heart. Everyone has felt it: the skip in our hearts when we tell a big fib, the effort it takes to breathe evenly. As the poet Joseph Brodsky has observed, self-consciousness does not really begin until one has told one's first deliberate lie. To deceive is human. The problem is, human beings are opaque. Some have considered this a design flaw -- perhaps the original flaw.

According to the ancient Greeks, the first human being owed his existence to a competition staged by Zeus to reward the most inventive of the gods. It was to be the world's first science fair, with Momus, the god of criticism, to serve as judge. Each competitor tried to outdo the rest. Athena constructed a magnificent dwelling; Poseidon built the first bull; and Prometheus made the first man. Momus didn't think much of any of the entries, but he was particularly scathing about man. Athena's dwelling was so grand it was unmovable; what if its inhabitants quarreled with their neighbors? Poseidon's bull had horns on either side of its head; they would have been more effective up front. And as for Prometheus's man, he lacked a window in his breast whereby others might look in and see "all the man's thoughts and wishes., and whether he was lying or telling the truth.

" In later years Momus grew so infuriated by the duplicity of this second-runner-up invention that he plotted mankind's destruction -- for which sacrilege he was driven from heaven. Despite this warning, the search for Momus's window has continued down the centuries. The Greeks developed a science of physiognomy to assess people's character from their facial features and gestures. On the assumption that anxious deceivers generated less saliva, suspected liars in ancient China were asked to chew a bowl of rice and spit it out. Judges in India scanned for curling toes. One pious Victorian physician suggested that God had endowed human beings with the capacity to blush so as to m.