Is the lie detector really effective? – Part 2


A new frontier in lie detection is now emerging. An increasing number of projects are using AI to combine multiple sources of evidence into a single measure for deception. Machine learning is accelerating deception research by spotting previously unseen patterns in reams of data.

After 9/11, the US government – long an enthusiastic sponsor of deception science – started funding other kinds of brain-based lie-detection work through Darpa, the Defence Advanced Research Projects Agency. By 2006, two companies – Cephos and No Lie MRI – were offering lie detection based on functional magnetic resonance imaging, or fMRI. Using powerful magnets, these tools track the flow of blood to areas of the brain involved in social calculation, memory recall and impulse control.

But just because a lie-detection tool seems technologically sophisticated doesn’t mean it works. “It’s quite simple to beat these tests in ways that are very difficult to detect by a potential investigator,” said Dr Giorgio Ganis, who studies EEG and fMRI-based lie detection at the University of Plymouth. In 2007, a research group set up by the MacArthur Foundation examined fMRI-based deception tests. “After looking at the literature, we concluded that we have no idea whether fMRI can or cannot detect lies,” said Anthony Wagner, a Stanford psychologist and a member of the MacArthur group, who has testified against the admissibility of fMRI lie detection in court.

A new frontier in lie detection is now emerging. An increasing number of projects are using AI to combine multiple sources of evidence into a single measure for deception. Machine learning is accelerating deception research by spotting previously unseen patterns in reams of data. Scientists at the University of Maryland, for example, have developed software that they claim can detect deception from courtroom footage with 88% accuracy.

The algorithms behind such tools are designed to improve continuously over time, and may ultimately end up basing their determinations of guilt and innocence on factors that even the humans who have programmed them don’t understand. These tests are being trialled in job interviews, at border crossings and in police interviews, but as they become increasingly widespread, civil rights groups and scientists are growing more and more concerned about the dangers they could unleash on society.

Nothing provides a clearer warning about the threats of the new generation of lie-detection than the history of the polygraph, the world’s best-known and most widely used deception test. Although almost a century old, the machine still dominates both the public perception of lie detection and the testing market, with millions of polygraph tests conducted every year. Ever since its creation, it has been attacked for its questionable accuracy, and for the way it has been used as a tool of coercion. But the polygraph’s flawed science continues to cast a shadow over lie detection technologies today.

Even John Larson, the inventor of the polygraph, came to hate his creation. In 1921, Larson was a 29-year-old rookie police officer working the downtown beat in Berkeley, California. But he had also studied physiology and criminology and, when not on patrol, he was in a lab at the University of California, developing ways to bring science to bear in the fight against crime.

In the spring of 1921, Larson built an ugly device that took continuous measurements of blood pressure and breathing rate, and scratched the results on to a rolling paper cylinder. He then devised an interview-based exam that compared a subject’s physiological response when answering yes or no questions relating to a crime with the subject’s answers to control questions such as “Is your name Jane Doe?” As a proof of concept, he used the test to solve a theft at a women’s dormitory.

John Larson (right), the inventor of the polygraph lie detector. Photograph: Pictorial Parade. Image: Getty.

Larson refined his invention over several years with the help of an enterprising young man named Leonarde Keeler, who envisioned applications for the polygraph well beyond law enforcement. After the Wall Street crash of 1929, Keeler offered a version of the machine that was concealed inside an elegant walnut box to large organisations so they could screen employees suspected of theft.

Not long after, the US government became the world’s largest user of the exam. During the “red scare” of the 1950s, thousands of federal employees were subjected to polygraphs designed to root out communists. The US Army, which set up its first polygraph school in 1951, still trains examiners for all the intelligence agencies at the National Center for Credibility Assessment at Fort Jackson in South Carolina.

Companies also embraced technology. Throughout much of the last century, about a quarter of US corporations ran polygraph exams on employees to test for issues including histories of drug use and theft. McDonald’s used to use the machine on its workers. By the 1980s, there were up to 10,000 trained polygraph examiners in the US, conducting 2m tests a year.

The only problem was that the polygraph did not work. In 2003, the US National Academy of Sciences published a damning report that found evidence on the polygraph’s accuracy across 57 studies was “far from satisfactory”. History is littered with examples of known criminals who evaded detection by cheating the test. Aldrich Ames, a KGB double agent, passed two polygraphs while working for the CIA in the late 1980s and early 90s. With a little training, it is relatively easy to beat the machine. Floyd “Buzz” Fay, who was falsely convicted of murder in 1979 after a failed polygraph exam, became an expert in the test during his two-and-a-half-years in prison and started coaching other inmates on how to defeat it. After 15 minutes of instruction, 23 of 27 were able to pass. Common “countermeasures”, which work by exaggerating the body’s response to control questions, include thinking about a frightening experience, stepping on a pin hidden in the shoe, or simply clenching the anus.

The upshot is that the polygraph is not and never was an effective lie detector. There is no way for an examiner to know whether a rise in blood pressure is due to fear of getting caught in a lie, or anxiety about being wrongly accused. Different examiners rating the same charts can get contradictory results and there are huge discrepancies in outcome depending on location, race, and gender.

As long ago as 1965, the year Larson died, the US Committee on Government Operations issued a damning verdict on the polygraph. “People have been deceived by a myth that a metal box in the hands of an investigator can detect truth or falsehood,” it concluded. By then, civil rights groups were arguing that the polygraph violated constitutional protections against self-incrimination. In fact, despite the polygraph’s cultural status, in the US, its results are inadmissible in most courts. And in 1988, citing concerns that the polygraph was open to “misuse and abuse”, the US Congress banned its use by employers. Other lie-detectors from the second half of the 20th century fared no better: abandoned Department of Defense projects included the “wiggle chair”, which covertly tracked movement and body temperature during interrogation, and an elaborate system for measuring breathing rate by aiming an infrared laser at the lip through a hole in the wall.

The polygraph remained popular though – not because it was effective, but because people thought it was. “The people who developed the polygraph machine knew that the real power of it was in convincing people that it works,” said Dr. Andy Balmer, a sociologist at the University of Manchester who wrote a book called Lie Detection and the Law.

The threat of being outed by the machine was enough to coerce some people into confessions. One examiner in Cincinnati in 1975 left the interrogation room and reportedly watched, bemused, through a two-way mirror as the accused tore 1.8 meters of paper charts off the machine and ate them. (You didn’t even have to have the right machine: in the 1980s, police officers in Detroit extracted confessions by placing a suspect’s hand on a photocopier that spat out sheets of paper with the phrase “He’s Lying!” pre-printed on them.) This was particularly attractive to law enforcement in the US, where it is vastly cheaper to use a machine to get a confession out of someone than it is to take them to trial.

But other people were pushed to admit to crimes they did not commit after the machine wrongly labeled them as lying. The polygraph became a form of psychological torture that wrung false confessions from the vulnerable. Many of these people were then charged, prosecuted and sent to jail – whether by unscrupulous police and prosecutors or by those who wrongly believed in the polygraph’s power.

Perhaps no one came to understand the coercive potential of his machine better than Larson. Shortly before his death in 1965, he wrote: “Beyond my expectation, through uncontrollable factors, this scientific investigation became for practical purposes a Frankenstein’s monster.”

Source: The Guardian

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