Response or Comment
Much of the contention and confusion that seem inevitably to arise whenever the subject of pain in animals comes up appear to stem principally from problems with the word "pain" itself. When used to describe responses in humans, "pain" can mean any subset of an incredibly broad spectrum of sensations and emotions, ranging from the instantaneous, galvanizing effect of a dentist drill hitting the nerve in a molar, to more airy notions such as the "pain" of rejection or "painfully" embarrassing situations. Humans even use concepts as abstruse as the German term, weltschmerz, or "world pain," which denotes a vaguely defined kind of sentimental depression or despair.
Murphy, D.H. (1982). The problem of pain: What do animals really feel? International Journal for the Study of Animal Problems, 3(4), 275-282.