So, I was watching some youtube videos of the game show "A Moment of Truth" which seems like it's pretty much staged, but whatever. It got me thinking about lie detectors.
I know it has something to do with pulse rate and maybe blood pressure, or something, when you're lying, and some signals from the brain. How can this possibly be accurate? How do they KNOW it's accurate? Sure, there's solid stuff you can test like name, age, weight, height and so on, but for questions like "have you ever cheated on your spouse?", how do they verify whether or not the machine is accurate? One might argue that they don't need to because they can ask the verifiable questions to test the integrity of the machine, but usually those kinds of questions offer no real pressure on the test taker.
If I were taking a lie detector test (on that game show) and it asked me something incriminating, even if I were innocent, I know my heart rate would jump and other signs of nervousness or tension would show up because I'd be worried that the machine would falsely detect! So then, my worry would in turn cause the machine to give a false reading of a lie.
How can one accurately test the integrity of a lie detector, and even if they do, how can they be 97% (or whatever the number is) sure that it is accurate the same way on ALL people?
One of the questions was "do you think you're a good person?" and she answered "yes" (right after admitting to many incriminating things, so you know she has no reason to lie about this kind of question), and it buzzed as a lie, meaning she does not consider herself a good person.
Being that she'd have absolutely NO reason to lie on that (right after admitting to adultery), I can only conclude that the machine is wrong. Doesn't make sense.