Public Release: 

Simple test improves accuracy of polygraph results

Symptom validity testing helps detect lies, feigned symptoms

Blackwell Publishing Ltd.

Maastricht, The Netherlands - November 28, 2007 - In order to prevent false positive results in polygraph examinations, testing is set to err on the side of caution. This protects the innocent, but increases the chances that a guilty suspect will go unidentified. A new study published in Psychophysiology finds that the use of a written test, known as Symptom Validity Testing (SVT), in conjunction with polygraph testing may improve the accuracy of results.

SVT is an independent measure that tests an entirely different psychological mechanism than polygraph examinations. It is based on the rationale that, when presented with both real and plausible-but-unrelated crime information, innocent suspects will show a random pattern of results when asked questions about the crime. SVT has previously been shown as effective in detecting post-traumatic stress disorder, amnesia and other perceptual deficits for specific events.

The study finds that SVT is also an easy and cost-effective method for determining whether or not a suspect is concealing information. In simulated cases of mock crime questioning and feigned amnesia, it accurately detected when a participant was lying.

Furthermore, when used in combination with the preexisting but relatively uncommon concealed information polygraph test (CIT), test accuracy is found to be higher than when either technique is used alone.

"We showed that the accuracy of a Concealed Information Test can be increased by adding a simple pencil and paper test," says lead author Ewout Meijer of Maastricht University. "When 'guilty' participants were forced to choose one answer for each question, a substantial proportion did not succeed in producing the random pattern that can be expected from 'innocent' participants."

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This study is published in Psychophysiology. Media wishing to receive a PDF of this article may contact journalnews@bos.blackwellpublishing.net.

Ewout Meijer, Msc, can be reached for questions at eh.meijer@psychology.unimaas.nl.

Psychophysiology is the oldest, first, and most established journal in its field. This prestigious international journal plays a key role in advancing psychophysiological science and human neuroscience, covering research on the interrelationships between the physiological and psychological aspects of brain and behavior. Psychophysiology reports on new theoretical, empirical and methodological advances in: psychology and psychiatry, cognitive science, cognitive and affective neuroscience, social science, health science and behavioral medicine, and biomedical engineering. The journal publishes theoretical papers, evaluative reviews of literature, empirical papers, methodological articles, meeting announcements, and fellowship opportunities. For more information, please visit www.blackwell-synergy.com/loi/psyp.

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