Polygraph Reliability and Validity

The validity and reliability of polygraph testing has been a subject of debate since such testing was first implemented almost a century ago (OTA, 1983, par. 1). Abundant research has been done on modern polygraph machines and techniques that has served to validate their use and their accuracy, however controversy still remains in the minds of many (Gougler et al., 2011, 196-201). One way to go about determining the reliability and validity of a polygraph machine would, of course, be to look at the research that has been conducted on the machine previously if available, as it truly takes years and abundant study to ensure these features to a degree worthy of scientific scrutiny (Gougler et al., 2011; 197). Assuming such research is unavailable or is untrustworthy, however, there are other more direct methods that can be employed to effectively determine how valid and reliable a polygraph is.

Validity is a measure of how well the polygraph measures what it is supposed to measure, and reliability is a measure of how consistent the polygraph is. To determine both validity and reliability, multiple tests will need to be performed with subjects that are both known to be telling the truth on certain elements and known to be lying on others (or perhaps some subjects only tell the truth, while others lie after base-line measurements are taken (Gougler et al., 2011, 196-8). If the polygraph is able to consistently differentiate lies from truths across the research population and above a selected confidence or probability point (approximately 90% seems to be the standard, according to Gougler et al. (2011, 200)), then it can be considered valid and reliable. It will be valid because it measures what it was intended to measure -- falsehood or lies -- and reliable because it will be consistent, as shown in continued success in repeated efforts.

References

Gougler, M., Nelson, R., Handler, M., Krapohl, D., Shaw, P. & Bierman, L. (2011). Executive Summary of the Meta-Analytic Survey of Criterion Accuracy of Validated Polygraph Techniques. Accessed 16 March 2012. http://www.polygraph.org/files/executive_summary_meta_analytic_survey_apa_2012.pdf

OTA. (1983). Scientific Validity of Polygraph Testing: A Research Review and Evaluation. Accessed 16 March 2012. http://www.fas.org/sgp/othergov/polygraph/ota/contro.html