… would you expect a positive or a negative correlation between mental ability and ability to feel pain? Most people unthinkingly assume a positive correlation, but why?

Isn’t it plausible that a clever species such as our own might need less pain, precisely because we are capable of intelligently working out what is good for us, and what damaging events we should avoid? Isn’t it plausible that an unintelligent species might need a massive wallop of pain, to drive home a lesson that we can learn with less powerful inducement?

At very least, I conclude that we have no general reason to think that non-human animals feel pain less acutely than we do, and we should in any case give them the benefit of the doubt.

I would add: why should we think that love (or feelings of emotional attachment) are any less strong or meaningful in “unthinking” animals than in people?