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National Academy of Sciences report says polygraph testing too flawed for security screening - News and Comment
Skeptical Inquirer, Jan-Feb, 2003 by Kendrick Frazier
A long-awaited report on polygraphs from the National Academy of Sciences says the U.S. Government should not rely on polygraph examinations for screening employees to identify spies or other national security risks because the test results are too inaccurate when used this way.
Much of the evidence assessing the validity of polygraphs, popularly called "lie detectors," is based on their use in the investigation of specific, known events such as crimes. In these cases, said the NAS committee, lie-detector tests can differentiate lying from telling the truth at rates well above chance, but they are far from perfect.
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The report, issued at a news conference at the Academy's headquarters in Washington October 8, 2002 (www.nas.edu), concludes that the polygraph's accuracy is not good enough for security screening for two reasons. First, accuracy is almost certainly lower when the tests are used this way rather than in the investigation of specific incidents. Second, the large groups of people being checked include only a tiny percentage of individuals who are guilty of the targeted offenses; tests that are sensitive enough to spot most violators will also mistakenly mark large numbers of innocent test takers as guilty. Tests that produce few of these types of errors, such as those currently used by several federal agencies, will not catch most major security violators--and still will incorrectly flag truthful people as deceptive.
"National security is too important to be left to such a blunt instrument," said Stephen E. Fienberg, chair of the committee that wrote the report and professor of statistics and computer science at Carnegie Mellon University. "The belief in its accuracy goes beyond what the evidence suggests.
Concerned about potential security violations at its national laboratories and criticized about congressionally mandated plans to expand its polygraph program, the U.S. Department of Energy asked the Academy to conduct a study of the scientific validity and reliability of polygraph testing to identify personnel who may jeopardize national security. Employees who work in sensitive positions at DOE labs and similar federal sites are subject to testing by law. However, the new report says that when polygraph exams are used this way, the drawbacks of current polygraph exams are abundantly clear.
The proposed wider use of polygraphs as a screening tool at the national labs became intensely controversial among many labs scientists. They criticized the idea as highly damaging to morale due to the large false-positive rates in polygraph exams, the lack of any serious scientific underpinning to polygraphy, and history showing that convicted spies had passed polygraph rests while they had been engaged in espionage. (See "Polygraphs and the National Labs: Dangerous Ruse Undermines National Security," Commentary by Alan P. Zelicoff, SKEPTICAL INQUIRER, July/August 2001.)
The NAS committee said polygraph testing rests on weak scientific underpinnings. And much of the available evidence for judging its validity lacks scientific rigor. "Almost a century of research in scientific psychology and physiology provides little basis for the expectation that a polygraph test could have extremely high accuracy," says the report.
Using these tests in pre-employment screening is even more complicated because examiners make inferences about individuals' future behavior based on information about previous deeds, which may differ widely from the offenses authorities hope to prevent. The committee concluded that polygraph testing is less accurate for employee screening than for investigating specific incidents.
On a more basic level, theories about how deception is linked to the physiological responses being measured have not been verified, the report says. A variety of mental and physical factors, such as anxiety about being tested, can affect polygraph results--making the technique susceptible to error. Also, people can learn ways to mimic some physiological responses of truthful test takers. This is a particular concern when dealing with deceptive individuals who have strong incentives to perfect certain "countermeasures" or ploys to appear honest and avoid detection. Available research sheds little light on how well examiners can systematically expose such people.
Despite its weak science base, polygraph testing is commonly believed to be a highly valid procedure for detecting lies. The report notes that popular culture and the mass media often portray lie detectors as magical mind-reading machines. The mystique surrounding the exams--instead of a solid scientific foundation--may account for much of their usefulness to authorities, the committee noted. Examiners' field reports and indirect scientific evidence indicate that testing programs may deter potential security violators or elicit confessions from some offenders who, unaware of the tests' weaknesses, believe that a lie detector would surely catch them.
The federal government relies heavily on polygraph testing to identify people who have committed or might commit espionage and sabotage. However, the report warns that overconfidence in this method may endanger national security objectives by creating a false sense of security among lawmakers, government employees in sensitive jobs, and the general public. As a result, other ways to ensure safety could be neglected, creating situations that might increase the risk of security lapses. Also, retention of highly skilled and valuable government workers could suffer because employees might fear being falsely identified as dishonest.
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