I'm still more partial with the dog but, I was thinking that maybe, the dog could be his perception of himself and the human could be how he really appears... like maybe the few times we see his reflection, we see him as human.

I prefer the dog, but then that's mainly because I find "adogfornoreason" amusing.

I like the theory that he imagines himself as a dog as a comfort to the unpleasant self-image he might otherwise have. It's not that uncommon to have an otherworldly persona to make yourself feel better about yourself.