They hooked him up to a polygraph machine that measures the most minute changes in his heart-rate and breathing -- and he passed the test with flying colours.
The reason, he was told by fellow recruits, is that candidates for training were interviewed in the second stage while attached to polygraph machines by wires wrapped around their fingers.
A polygraph machine measures changes in heartbeat, blood pressure and galvanic skin response (the activity of sweat glands in the fingertips), while the subject answers a series of questions.
