Well, there's a reason why a lot of humans can't see ghosts. A lot of us our told from a young age that ghosts do not exist, that they're a silly fantasy or whatever, so our minds stop believing in them and it suppresses our recognition of them. That's why babies and toddlers will react to spirits but will lose the ability to do so because of what they are told when they grow up. Animals aren't like humans like that. No one there to tell them whether ghosts exist or not, so animals are more sensitive to the presence of spirits, I think.
Yeah, I believe in ghosts but normally, you can't see them clearly like that or speak to them like we speek to a normal person(Well it's a cartoon so it's okay ). But I compleatly agree with what you say! But I think that animals react more to spirits because they have a kind of "power"(well power is a big word but I don't find any words) that not a lot of humans have, that's why a lot of humans don't believe in ghosts. Because they can't feel them. But the animals can,I think