Inducement Leading to Confession

If there were any biologists in this world, they would definitely be very interested in the Abyssal Sirens. How could this kind of creature feel no pain, which is, from a scientific perspective, a protective mechanism that is used to warn people from doing the wrong thing. One story goes that there was once a man who could not feel pain. He had burned himself while reading, but he didn't realize it until he smelt something scorched. However, by the time he realized it, he was already irreparably injured.