(I) Of all the things we feel, none captures our attention like pain. (II) We may sometimes be unconcerned about other experiences but it is hard to ignore the experience of pain. (III) Yet for all the discomfort it causes, we would be at risk if we had no sense of pain. (IV) For instance, it would be difficult for children to learn not to touch a hot stove, or to stop chewing their tongues. (V) These receptors are neurons with specialized free nerve endings.