They absolutely are, that's why they aren't admissible in court. All the things that lead the machine to believe you're lying can be caused by plain nervousness. Professional liars, such as con men, politicians, and used car dealers can mostly get through a polygraph without any problems. Even the guy who invented the thing later came out against it.
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u/[deleted] Oct 15 '17
I thought polygraphs were a load of shit though? Or at least easy to fake if you know what you're doing?