You might be able to beat the machine , but are you really certain you can always beat the examiner ? You shouldn ' t be . At the end of the lecture , Sullivan said he once made a bet with a friend who was bragging he could beat the polygraph he told him to think of a number between three and sevenand if Sullivan is able to guess it just by the look on his face alone while staring him in the eye and repeating each number back to him as he counts from one to ten , the friend has to pay him 5 , 000 bucks . In other words , the guy has something serious to lose , and he ' s up against a real pro . Personally , I wouldn ' t take that wager in a million years . No matter how slick you think you are , there ' s always the risk of running into someone better . I would imagine a lot of the people hired in interrogatortype positions use the polygraph more as a sort of magician ' s prop than as something to seriously rely on . And for what it ' s worth , some people really are that fucking good . I once heard about a research study where certain subjects were able to correctly detect deception 100 % of the time based on the subject ' s tone of voice alone no visual cues , no outside mechanical aids whatsoever . One of the abnormally gifted participants in question was a junior research analyst themselvesnot a professional interrogatorbut later , had been brought in to observe highlevel business negotiations for the sole purpose of informing the negotiating team about their gut hunch about when the other parties were bullshitting or holding back . They also went on to corporate intelligence as a HUMINT collector for Fortune 500 companies , so there ' s that . TLDR People don ' t fail the polygraph , they fail the examiner .