It's been a long time since I've read Dune, but IIRC, the Gom Jabbar was a test to see if you were human by determining if your will would trump your instincts. The testee held his hand in a little box that manipulated the nerves to make the testee think his hand was being burned to a lump of coal. However, the testee was told that if he removed his hand he would be stabbed with the Gom Jabbar, a needle with a drop of poison that would kill him instantly.
Paul Atredies held his hand in the box longer than anyone had ever done so before. When he removed his hand from the box at the end of the test, he was surprised to find it unhurt.
I mention this because on the homosexual threads I often comment that the difference between humans and animals is that humans can govern their animal natures by force of will.
Shalom.
In a contemporary real sense, it also illustrates the difference between feeling about something and thinking about something. An important distinction.