Thanks, I understand the experiment as described. But if you start by asking "what makes a pig optimistic", you're already assuming that a pig can be optimistic

Thanks, I understand the experiment as described. But if you start by asking "what makes a pig optimistic", you're already assuming that a pig can be optimistic. Whatever reason you find after that to say that the pig is optimistic is going to be wrong, because you have failed to do anything to justify the idea that pigs can be optimistic in the first place.