Officially they have to follow their training, so to speak, and I am sure that's all about how polygraphs are 100% reliable and it's scientific and all that. I wonder if any instructors at some point close the door and tell them "listen, students, yeah, it's all bunk, but we just have to pretend, ok?".

> I wonder if any instructors at some point close the door and tell them "listen, students, yeah, it's all bunk, but we just have to pretend, ok?".

If online stories are to trusted, this has occurred in a lot of government clearance related situations.

They're apparently allowed to manipulate the subject ad lib.

Almost certainly.