Since we're talking about "cat intelligence," here's a list of phrases you might wish to use when interacting with your cat. I can't guarantee that they'll understand what you're saying, but note the simple syntax (excluding the final phrase, which expresses an idea that spayed or neutered cats would probably find nonsensical anyway).
Who's my pretty cat? This is a rhetorical question.
Awww, puss-puss-puss. An affectionate statement.
What do you want?
Look at you! Say this when the cat does something remarkable.
Want to go outside?
Want your treats?
Yeah, you're my BEST girl. This is said while petting. May inspire jealousy if you have multiple female cats.
You'd be a BEAUTIFUL pair of mittens. Say this in a lighthearted way that makes the cat think you're being sweet, and then say "Har. Har."
Are you sad? Are you the saddest girl this side of the Baden Tower? Usually said in a mocking tone of voice, when the cat is upset about something trivial. You don't need to know where the Baden Tower is in order to say this.
What're you lookin' at? Not accusatory. Said when the cat is looking intently at something which you yourself can't see.
I'm sorry. Say this after a fight.
It's not that I don't love you, it's just that...well, you're a cat, and people would talk.