In this study, 54 male inmates were classified as psychopaths or non-psychopaths through clinical diagnoses and subjected to polygraph examinations; the psychopaths did not 'beat the polygraph'.
Half of the subjects were instructed to steal a 20-dollar bill (under controlled conditions), while the other half were merely told of the theft the others committed. A 20-dollar inducement was offered if the subjects could outfox the machine. The same series of control and experimental questions was asked each subject. Psychopaths had no more success in defeating the polygraph than non-psychopaths, who had no success at all.