One of the strongest of human impulses, even when presented with irrefutable empirical evidence. The scientists have proven it:

I've found over and over again that people who have been surreptitiously tape recorded in sting operations often refuse to admit that they said the inculpatory stuff on the tape in spite of what the recording clearly shows that they said. They usually claim that the government tampered with the tape. In rare occasions, the tape has been tampered with, but 99% of the time it hasn't.

This looks like something a bit different from Dennis Preston's observation, where people don't seem to believe that they sound the way they were tape recorded (usually their phonetics, I assume, although perhaps grammar as well). In the sting tape cases, the person denies the CONTENT of the statements, claiming that they never could have said such things.

We. Do. Not. Torture.