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 make their deceptions apparent. Today, you can pick up the basics of body language for a few bucks on almost any library resale table -- "Who's Lying to You and Who's Lusting for You!" -- along with guides for spotting tricksters when you travel abroad. Popular manuals, updated with the latest findings of neuroscience, advise you how to track the eye movements and hand gestures of your spouse, boss, and stockbroker.

Yet experts on deceit -- the sort of psychologists who regularly ask Americans to lie to one another in laboratories -- tell us that the vast majority of us are very bad at detecting deception, despite our confidence in our own powers. In 2006, one review of the available research concluded that people can successfully sort truth-tellers from liars only 54 percent of the time, or about as well as blind guesswork. Surprisingly, the more intimately we know the deceiver, the worse we do. Even cops, judges, and psychologists -- those citizens professionally licensed to sort truth-tellers from liars -- don't get it right much more than half the time.

That is why, in the early years of the twentieth century, a coterie of American psychologists set out to decipher the operations of the human mind by peering beneath the skin. They recorded the body's involuntary tremors: its secret pulsations, hidden pressures, and suppressed gasps. In doing so, they drew on a new theory of the emotions that declared that human emotions were nothing more than a set of physiological responses inherited from our animal ancestors. Each act of deception, they suggested, produced a divided self, a disjuncture between the heart, fearful that its secret feelings would be exposed, and the mind, desperate to suppress the body's betrayal.

The first person to attempt this feat of detection was an artful young Harvard psychologist and lawyer named William Moulton Marston, later famous as the creator of the cartoon character called "Wonder Woman" (the embodiment, he said, of all the psychological principles behind his technique of honesty testing). But the lie detector did not truly come into its own -- or even acquire its name -- until the 1920s, when John Larson and Leonarde Keeler adapted Marston's method to the interrogation of criminal suspects. There was much that Larson and Keeler shared; for instance, both men first met their wives while interrogating them on the lie detector. But soon after they both moved to Chicago to prove their methods in the American capital of crime and corruption, they become rivals and eventually enemies. In the end, each man paid a personal price for his obsession, led by the device to mistrust the people closest to him, including one another. The machine that launched their careers poisoned their lives.

By then, however, they had established the machine in the heart of American culture, transforming the device from a detector of lies into a monitor of loyalty. What began as a way to confirm honesty in precinct stations, office towers, and government agencies became a way to test the credibility of Hollywood movies and Madison Avenue advertising. By mid-century, the device was being used to safeguard nuclear secrets, assure the political fidelity of scientists, and purge homosexuals from government jobs. By the 1980s, some 5,000 to 10,000 polygraph operators were testing 2 million Americans each year. The lie detector had become America's mechanical conscience.

Today, the lie detector is still used to interrogate criminal suspects, expose fraud, safeguard nuclear secrets, and combat terrorism. Yet no country other than the United States has made use of the technique to any significant degree. And even in America, the lie detector has been consistently banned from criminal courts and discredited by panels of illustrious scientists, from the Congressional Office of Technology Assessment to the National Academy of Sciences. Surveys of studies of role-playing games conducted in labs suggest tremendous variability in how accurately the technique detects guilty reactions: from only 35 percent to nearly perfect for standard polygraph procedures, with most in the range of 60 to 90 percent. As for field studies, their accuracy is just as variable, as best anyone can determine. Indeed, according to a review by the noted psychologist David Lykken, in real-life "field situations," when results were graded on the basis of the polygraph results alone, the innocent were called truthful only 53 percent of the time, which is to say, hardly better than guesswork. Despite all this, the lie detector lives on.

Given this history, this book does not attempt to expose the scientific pretensions of the lie detector. Not only would such an exposé be redundant; it would hardly achieve its purpose. Instead, this book addresses the obverse problem: Why, despite the avalanche of scientific denunciations, does the United States -- and only the United States -- continue to make significant use of the lie detector?

Of course, the machine's proliferation in twentieth-century America shows that the public believed the tests served some purpose. But in the case of the lie detector something additional was required, because persuading Americans of the machine's potency was itself a prerequisite for the machine's success. As its proponents acknowledged, the lie detector would not distinguish honest Americans from deceptive ones unless those same Americans believed the instrument might catch them. In short, the lie detector depends on what medical science has dismissively termed the "placebo effect." At the same time, as its proponents also acknowledged, the lie detector did not test whether people were actually telling the truth so much as whether they believed they were telling the truth. So either way, America's obsession with the lie detector poses the most troubling question of all: What do we believe?

Copyright © 2007 by Ken Alder