There's a difference between pain and suffering. e.g. a human on an opiate drug can feel pain signals but not be bothered about them. Yet he can still suffer f

There's a difference between pain and suffering. e.g. a human on an opiate drug can feel pain signals but not be bothered about them. Yet he can still suffer from the knowledge of his impending death. We can measure pain signals in animals; we can reasonably guess that most species don't know that they're eventually going to die. More than that we don't know yet. Perhaps when we understand better how the mind works (e.g. by developing AGI) we'll be able to understand animals better too.