[andai]

Your logic implies that intellectually impaired people also don't experience pain or pleasure.

I do imagine they experience a lesser degree of psychological suffering, of the kind created by mental processes, if some of those processes are absent. But the basic pain of the type experienced by a being who is caged and killed, that's just physical.

I've sometimes heard the words pain and suffering used to separate these two types out. If you accidentally hit your toe on the table, that's pain. If you then call yourself an idiot for doing that, that's suffering. But that's not a very mainstream use of the word, I just just don't know better one for it. I think "physical suffering" and "psychological suffering" are more helpful.

Anyway my point is, that as far as we can tell we're on the same pages animals as far as physical suffering goes.