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Date: Oct. 8, 2002
Contacts: Vanee Vines, Media
Relations Officer
Andrea Durham, Media
Relations Assistant
(202) 334-2138; e-mail
<news@nas.edu>
FOR IMMEDIATE RELEASE
Polygraph Testing Too
Flawed for Security Screening
WASHINGTON – The federal
government should not rely on polygraph examinations for screening
prospective or current employees to identify spies or other
national-security risks because the test results are too inaccurate
when used this way, says a new report from the National Academies'
National Research Council.
Much of the evidence
assessing the validity of polygraphs, also called "lie detectors," is
based on their use in the investigation of specific, known events such
as crimes. In these cases, lie-detector tests can differentiate lying
from telling the truth at rates well above chance, but they are far
from perfect. The report 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, Carnegie Mellon University,
Pittsburgh. "The polygraph's serious limitations in employee security
screening underscore the need to look more broadly for effective,
alternative methods."
Concerned about potential
security violations at national energy laboratories, the U.S.
Department of Energy asked the Research Council to conduct a study of
the scientific validity and reliability of using 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. When used this way, however, the drawbacks
of current polygraph exams are abundantly clear, the report says.
The exams include a pre-test
interview between the examiner and test taker, followed by
interrogation coupled with the use of a device that records an
individual's physiological responses, such as respiration rate and
changes in blood flow, to a series of questions. Examiners later
analyze the record of these responses to help make inferences about
whether someone is being honest.
Polygraph testing now rests
on weak scientific underpinnings despite nearly a century of study, the
committee said. And much of the available evidence for judging its
validity lacks scientific rigor.
Moreover, because the
largest part of the evidence comes from studies that assess lie
detection related to specific events, it has limited relevance to pre-
and post-employment screening, the report says. Examiners ask generic
questions during security screening because they do not know what
violations test takers may be concealing. Individuals may react
differently to generic questions than to specific ones typically used
in investigations of known events. Additionally, both examiners and
test takers may have difficulty knowing whether answers to generic
questions are truthful unless there are clear and consistent standards
that define what type of response is justified.
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 and sufficient
resources 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. 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,
overconfidence in this method may endanger national security objectives
by creating a false sense of security among lawmakers, federal
employees in sensitive jobs, and the general public, the report warns.
As a result, other ways to ensure safety could be neglected, creating
situations that might increase the risk of security lapses. Resources
could be wasted by devoting too much attention to employee screening
and too little to other security measures. Plus, retention of highly
skilled and valuable government workers could suffer because employees
might fear the consequences of being falsely identified as dishonest.
Some potential alternatives
to polygraphs show promise, but none has led to scientific
breakthroughs in lie detection, the report says. Moreover, the federal
government has not seriously developed the science base of any method
to detect deception through the analysis of individuals' psychological
and physiological reactions.
The committee called for a
broad research program that would provide federal agencies with the
most scientifically sound methods for deterring and detecting major
security risks, and work to make government authorities fully aware of
the strengths and drawbacks of their security techniques. This effort
would support a variety of activities – from basic research on
psychological, physiological, social, and political processes related
to discouraging and uncovering security threats, to studies on ways to
carry out well-founded screening techniques in everyday practice. No
single research approach is clearly superior.
An impartial organization
that is not responsible for any aspect of detecting deception should
run a considerable part of the program, the report says. Additionally,
the program should follow established standards for scientific research
and, without jeopardizing national security, operate under normal rules
of scientific freedom and openness to the fullest possible extent.
The study was sponsored by
the U.S. Department of Energy. The Research Council is the principal
operating agency of the National Academy of Sciences and the National
Academy of Engineering. It is a private, nonprofit institution that
provides science advice under a congressional charter. A committee
roster follows.
Read the full text of The Polygraph and Lie Detection for free on the Web, as
well as more than 1,800 other publications from the National Academies.
Printed Copies are available for purchase from the National Academy
Press Web site or by calling
(202) 334-3313 or 1-800-624-6242. Reporters may obtain a copy from the
Office of News and Public Information (contacts listed above).
NATIONAL RESEARCH COUNCIL
Division of Behavioral and
Social Sciences and Education
Board on Behavioral,
Cognitive, and Sensory Sciences
and
Committee on National
Statistics
Committee to Review the
Scientific Evidence on the Polygraph
Stephen E. Fienberg1 (chair)
Professor of Statistics and
Computer Science
Carnegie Mellon University
Pittsburgh
James J. Blascovich
Professor and Chair
Department of Psychology, and
Co-Director
Research Center for Virtual
Environments and Behavior
University of California
Santa Barbara
Richard J. Davidson
Director
Laboratory of Affective
Neuroscience, and
Vilas Professor of
Psychology and Psychiatry
Department of Psychology
University of Wisconsin
Madison
Paul Ekman
Director
Department of Psychology and
Human Interaction Laboratory
University of California
San Francisco
David L. Faigman
Professor
Hastings College of Law
University of California
San Francisco
Patricia L. Grambsch
Associate Professor
Department of Biostatistics
School of Public Health
University of Minnesota
Minneapolis
Peter B. Imrey
Professor
Department of Biostatistics
and Epidemiology
The Cleveland Clinic
Foundation
Cleveland
Emmett B. Keeler
Senior Mathematician
RAND Health
Santa Monica, Calif.
Kathryn B. Laskey
Associate Professor
Department of Systems
Engineering and
Operations Research
George Mason University
Fairfax, Va.
Kevin R. Murphy
Professor
Department of Psychology
Pennsylvania State
University
University Park
Marcus E. Raichle 1,2
Professor and Co-Director
Division of Radiological
Sciences
Mallinckrodt Institute of
Radiology
School of Medicine
Washington University
St. Louis
Richard M. Shiffrin1
Luther Dana Waterman
Research Professor
Department of Psychology, and
Director
Cognitive Science Program
Indiana University
Bloomington
John A. Swets1
Chief Scientist Emeritus
BBN Technologies
Tequesta, Fla.
RESEARCH COUNCIL STAFF
Paul C. Stern
Study Director
1 Member, National Academy of Sciences
2 Member, Institute of Medicine
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