Let's consider Chester. From the name you can probably guess, I'm talking about a dog, since no one is named Chester anymore. Chester is our family mongrel. He is purportedly part dachshund and part chihuahua. He clearly has a personality. For one, he is a big lover. At no provocation at all, he will jump up on my lap and sprawl himself out, assuming a sort-of reclining nude pose deserving of Edouard Manet's brush strokes. He will gaze into my eyes awaiting strokes to his furry belly.
He incorrectly assumes I feel as he does. But to placate the poor thing who knows no better, I give the furry surface a gentle stroke or two, providing an illusion of affection to satisfy him. Chester doesn't seem to understand, I'm not really a "dog person." Still, he bubbles with love towards me. (In this way he will eventually conquer me.) I give him water, take him on walks, and discuss alternative energy sources and precious metal investment strategies with him, maybe that's why the feelings.
OK, so that is the healthy part. Now for the disorder part. Chester had an abusive upbringing before he was rescued by us. I'm not sure what happened to the little creature before we got him, but...don't show him your foot, he will transform into a miniature grizzly bear. And don't say the word "cage". If you say "cage", even if he is being a grizzly bear, he will instantly cower, put his tail between his legs and do his "humble walk" to his cage. So there, two personality disorders. Seems human enough, no?
Some dogs have more humanness to them than others. You can observe them, then affix a score, how much is dog and how much is human. You might say, oh, this one is basically pure dog, that one is about sixty percent dog and forty human. Chester would have a fairly high "humanness quotient" were it not for one curious behavior. He sleeps with my son John. If I walk in the room while John is still sleeping, he will growl excitedly, show his teeth, with a wild look in his eyes. Even though it is I who makes sure he has food and water, it is I who takes him on his walks, I who stroke his furriness, and it is I who carries the do-do bag and picks up product left behind after assuming his signature "arch of Saint Louis" position, I am a stranger in that moment.
I put him at about eighty-percent dog.