A quantitative review of the guilty knowledge test.

The guilty knowledge polygraph test (GKT; D. T. Lykken, 1959, 1960) is a psychophysiological method of identifying suspects with concealed information about a crime. A meta-analysis of 50 treatment groups drawn from 22 laboratory simulation studies (total N = 1,247) was conducted to provide a comprehensive estimate of GKT accuracy under controlled conditions. Electrodermal measures correctly identified 76% of participants with concealed knowledge and 83% of those without information. Informed participants were detected at rates significantly in excess of chance, with a mean weighted effect size of .57. Enactment of mock crimes increased the hit rate to 82%. The rates of false-positive error among noninformed treatment groups did not significantly exceed chance. Applications and research directions are discussed.