duplicate post
My boy is an all black greyhound. I love having the opportunity (which I take frequently) to tell him either:
“Hello, tall dark and handsome!”
Or:
“You know, a gypsy once told me I’d fall in love with someone tall, dark and handsome. And here you are!”
I don’t ask Pluto if he’s a good boy.
I tell him he’s a good dog, with the hope that by constant encouragement and reinforcement, one day he will be a good dog. 
At least someone out there is also interrogating their cats as to their goodness
I always took it as a call and response situation. You ask who is a good boy, he acts in a way that calls attention to himself, implying “Me, me!” And then we affirm that he is correct, praising him not only for being good, but smart enough to know it, too.
It just seems like it would be a lot more affirming than just hearing “Good boy!”
And, yes, I am anthropomorphizing and am aware that dogs don’t actually understand it that way. But we’re discussing our behavior, not theirs.
Funny. This reminds me of a friend who was a psychologist specializing in family counseling with troubled kids. He said the most effective thing he did was identify when the kid did something good, and then praise them like crazy. That seemed rare in those families, and seemed to work better than anything else.
He once said that he came home at night and said the same things to his dog that he’d been saying in counseling sessions all day long.
My ex-wife used to chide me for using baby-talk with my dog. Turns out that I was instinctively using the tone and language that apparently dogs respond to best. He was a highly intelligent Bernese Mountain Dog (most working dogs are bred for intelligence as well as specific capabilities) who had quite an extensive vocabulary of words he understood – not just the obvious like “would you like to go for a walk?” but more abstract concepts like “later”, meaning he would get what he wanted, but not right now.
He was smart enough to outsmart a health care worker who came to look after my elderly mother when she lived with us. He loved to jump up and try to play with her, sometimes bringing his squeaky-toy to encourage this, but in an effort to get some work done, she opened the patio door and went out on the deck. He naturally followed her out, whereupon she jumped back in and closed the glass door. Next week she came by he once more wanted to play, so she once more walked out to the deck. I have this fond memory of Bernie going out to the edge of the door sill with that beautiful Bernese smile on his face, expressing the sentiment “I know this game. I choose to sit here inside the house and smile at you, out there on the deck like a naive idiot. Your move. What are you going to do now?” 
ETA: Forgot to mention this beautiful quote from Aaron Katcher (abbreviated version): “A dog is like a child who never grows old – always there to love and be loved.”
In Spain we tell them “well done”, "“pretty doggie”, “good doggie” when they follow orders correctly or anticipate the order, but the question “who’s a good doggieeeee?” is something I only see done in Spanish when it’s in a movie translated from English. I’m sure there are people who do it, but well, they’re likely to be the same ones who think you need to speak to your dog in English.
Dolphins are supposed to be quite smart, so the thing to ask them is “Who’s a smart dolphin?”
When I was doing some dolphin training some years ago (and yes, we were doing a research project that had to do with how smart they might be), I gave them my college textbook on differential equations. Then each day, I would ask them “Who’s a smart dolphin?”, and they would tell me what problems they solved the previous evening, including showing all their work (which of course I carefully transcribed).
And that’s how I got though my Differential Equations class that year.
We were doing a study of language acquisition in dolphins. I don’t think Douglas Adams (of HGTTG fame) knew of our project at the time, because when our dolphins warned us that the Vogons were coming, we understood them immediately.
ETA: And furthermore, there’s a stub of a website, ironically named “Doggie”, with a picture of those dolphins, here.
I’ve always done this with babies too. Who’s the best little baby ever, yes, you are!
They - babies and dogs make me feel happy, and that makes them the best, for that moment. You generally only get positive feedback from this behaviour, so it perpetuates.
There was a scene in Scrubs, a show I never watched often but I saw this one, where two of the characters are thinking about having a baby, and the woman says that it’ll be like having a dog, but it grows and learns to talk.
I’ll stop when they answer.
As Terry Pratchett put it:
Why must we perpetually ask dogs who’s a good boy/girl?
Because deep down we don’t really know. And we don’t trust anyone else but dogs to tell us the truth.
It was, I think, Charles V who pointed out that horses speak German and God speaks Spanish.
In my experience, parrots speak Spanish or French depending.
Cats… well nobody really knows.
Because it makes them happy and excited and makes them want to please you all the more. In my experience, praise reinforces good behavior.
This meme was going around a while back: When your dog eats your philosophy homework.
I’m sure he’s pondering the eternal question, “Who’s a good boy?”
I like the fact that he has a panic room that’s called the “thunder room.”
Most dogs will sell you out for a hamburger.
Knowing my dogs, they’d get hung up over, “What exactly is good?”
I don’t ask my rescue dog “who’s a good girl” I tell her she’s a “good girl”. I think she needed to hear it. She had some bad habits when I got her. Positive reinforcement with praise helped out.