The two parts of pain
TIL: That what we think of as "pain" is actually two different things. The most basic sense is called nociception — a non-subjective reflex that drives lots of animals to pull away from dangerous things. Pain — actual pain — is what happens after nociception, and different individuals perceive it differently under different situations. So, for example, nociception is why you jerk your hand away from a hot stove. Pain is the feeling that helps you learn not to touch hot stoves again. Oh, and also, crabs might be capable of feeling both.