A History in Deception
The polygraph has long been plagued by questions
The polygraph-developed in the 1920s by John Larson, a Berkeley, Calif., policeman with a PhD in physiology-relies on the notion that people get nervous when they lie. A subject is strapped to a chair by wires and cuffs on his arm, chest, and fingers, and the "lie detector" marks his vital signs in squiggles on paper or a computer screen. If he shows signs of an accelerated heart rate, increased sweating, or faster breathing in response to an incriminating question, he's failed the test.
First conceived as a means of replacing police brutality with hard science, the polygraph quickly took on "a bluff and bluster kind of role" in police precincts, says Ken Alder, a historian at Northwestern University. "It has the same logic as torture...to intimidate people into confessing." Academic psychologists had doubts from beginning, and only two years after its introduction, federal courts rejected polygraph evidence because of concerns about its reliability. They also worried it would supplant the jury's role of judging a defendant's credibility.
Still, the polygraph managed to take off in other spheres-government employee screening, child custody hearings, and increasingly since the September 11, 2001, terrorist attacks on the United States, as an anti-terrorist tactic. Before private employers were banned from using the device to regularly screen employees in 1988, an estimated two million tests were administered a year across public and private sectors, says Alder, author of The Lie Detectors: The History of an American Obsession.
At the same time, spies including US Central Intelligence Agency double agent Aldrich Ames and serial killers fooled the test on multiple, highly publicized occasions, highlighting its flaws in the face of countermeasures and the sociopathically calm. Most recently, in 2003, a report by the National Academy of Sciences (NAS) rejected the method, calling the few studies on the topic unrealistic and poorly controlled. The report concluded from these studies that the "tests can discriminate lying from truth telling at rates well above chance, though well below perfection," and are lacking both sensitivity and specificity. What's more, they were troubled by the fact that the monitored changes weren't specific to deception-after all, being accused of a crime is stressful in its own right.
It is a particularly poor tool for screening, says Marcus Raichle, a professor at the Washington University in St. Louis School of Medicine who served on the NAS committee, and raises "serious concerns [about the] number of people you'd have to dismiss in order to catch a few spies." The committee estimated a 99.6% false positive rate, even assuming a sensitivity far above reality, meaning that nearly every blameless potential employee would be deemed untrustworthy by the polygraph.
Though anxiety has proven an imperfect correlate of deception, the US government alone continues to administer 40,000 polygraph tests each year and as many as 10 times that number may be used in the private sector, estimates Raichle. He says he got the sense that many within the government "were not happy with the [NAS] findings. They believed in the polygraph, thought it was adequate, and were not particularly interested in hearing otherwise."
Still, in part on the report's recommendation, several agencies are now taking steps to explore other options. The CIA started showing interest in fMRI lie detection as far back as the early 1990s, according to Mark George at the Medical University of South Carolina. And scientists have long experimented with machines that measure tiny changes in facial expression, vocal pitch, brain electrical activity, or heat around the eyes in the hopes of connecting these signs to lying. The KishKish lie detector, an add-on product of Skype.com, claims to analyze voice stress levels for signs of deception, while scientists at Honeywell laboratories in Minneapolis are trying to use heat maps of the face to detect deception technologies.
Whether any of them can replace the polygraph may not be up to new research, says Alder: "The lie detector can't be killed by science because it's not borne by science."