Do Lie Detectors (Polygraphs) Really Work?

This video reviews the evidence supporting and refuting the accuracy of polygraphs (lie detector test). The use of polygraphs for any application is controversial. Polygraphs measure heart rate, respiration, and skin conductivity, under the theory that changes in these areas occur when someone is lying. Current research does not support the idea that polygraphs work. There is no physiological reaction associated with deception, so the underlying theory of the polygraph is not supported. Measures of the physiological responses may be accurate, but there is no pattern of responses that indicate deception. Countermeasures have also been developed, which appear to make the polygraph results even less valid. Physical movement, cognitive training, and certain medications have all been identified as countermeasures to a polygraph. True positive, false positive, true negative, and false negative rates for polygraphs have been studied. The false positive accuracy is about 50%. The accuracy is slightly higher for true positives. The concept of detecting lies would have many potential applications, however, the polygraph is not scientifically supported. Studies show that two-thirds of the public believe polygraphs are fairly reliable and valid. More research on the issue of polygraphs and their usage is needed.