Oh yes, I remembered the other thing I meant to say.
I think horror is the sense you are about to be eaten, or that someone close to you is. It is a primal fear with survival value, which we share with animals.
Where we differ is in our imaginative capacity, with which we can conjure this emotion even absent actual danger. Like animals, we can be traumatized by horror and confinement, and like animals we can stay stuck there forever.