I know you’re looking for more empirical responses, Ringo, but I’ve got a personal anecdote that’s relevant. I work for a government agency (via contract) and underwent a polygraph. In the post-polygraph interview (aka, the “I Know You’re Lying, Now Confess” phase), I was told that I demonstrated deception in regard to my account of drug use and handling of Classified materials. Thing is, I’ve never, nor would I ever, mishandle Classified or Sensitive material. Furthermore, my drug history is absolutely clean.
The polygrapher at one point said, “you see this spike? That’s like a finger pointing to God telling me that you’re lying.” My response (which didn’t include the fact that I’m an agnostic and am further skeptical that line graphs have fingers with any desire to point at a deity) was “you’re the one who knows how to read that. I see spike all over the place. But if it’s calling me a liar, I’m calling it a liar.”
As to the drug question, I pretty much ended the conversation with “Listen, you’re not gonna’ beat a confession out of me here.” For the Classified materials thing, I said, “First off, any information that comes in could endanger my coworkers if it got out, so I wouldn’t do that.” He came back with, “Come on, maybe you were out at a bar and wanted to impress a girl or something?” At that point I laughed and pointed out that if I were trying to impress a girl, the last thing I’d want to do would be to tell her that I work where I do and then bore her with mostly technical data.
The interview ended with him saying, “I’ve got to send the data to HQ. There’s a good chance that they’re going to want you to come in for another polygraph.” Then, as he was escorting me out of the building through the elevator, he half-mumbled, “you know you passed, right?”
It probably helped that we both knew that we shared a mutual friend. . .
At the end of the day, the polygraph is useful for forcing confessions when the polygrapher already knows the answers.