The parent poster is correct. This is a standard practice for polygraph interviews. The pick one question, more or less at random, and double/triple/quadruple down on it until you break. Or don't.

I got "have you ever committed a crime" (and after a actually pretty cool conversation about filesharing vs recording songs off the radio with a tape recorder, I passed). A friend of mine got "have you ever had sex with animals." I don't think he enjoyed his experience quite as much.