When the time comes for your brain to process the information, the second word comes up faster than the first one. So when it's in your head, all of a sudden, it comes out backwards and you think of the word backwards.
“I understand by this passion the union of desire, friendship, and tenderness, which is inflamed by a single female, which prefers her to the rest of her sex, and which seeks her possession as the supreme or the sole happiness of our being.”