I don’t have the firmest grasp on the way a polygraph functions, but I’ve just had this thought a lot.
Could a polygraph help people uncover repressed memories? For example if a person suspects they were being harmed as a child, but can’t remember details, could a polygraph help them get more answers? Like by asking specific questions maybe related to what a person suspects happened and detecting how they respond.
Or, is a polygraph only useful to detect truth/a lie about things someone is certain about and remembers fully?
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No.
All a polygraph does is measure a set of physiological responses – like how fast you a breathing, what your pulse is, how sweaty your hands get, etc. The “science” behind a polygraph is that if you are lying, you are going to have an involuntary stress reaction, causing one of those responses to change. I say “science” because there is a host of evidence that polygraphs don’t work as lie detectors – people can get uncomfortable telling the truth and there are proven ways to trick the machine even when you are lying.
Even **if** the polygraph was 100% accurate in detecting lies (which it is **not**) it only works if the subject _knows_ they are lying, and thus has the involuntary response. It would not be capable of telling if someone was telling a lie they _thought_ was the truth, as they wouldn’t have the physiological reactions the machine can dectect.
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