Why only English? If they can learn the language of another entire species (us), why would they only be able to speak one human language? I am as much a believer in animal communication as all of you, but I think it’s a bit much to think that they are aware that “English is the ‘universal’ language”.
To the dog people (and I’m sure all you cat people will confirm), the spelling thing may work on dogs, but it only works on cats for so long. They figure out what you’re spelling eventually!
Really, it’s us who need to learn their language. I believe they understand everything we say,except the parts they’re completely uninterested in (which I’m sure is a lot of it, lol), we just don’t always understand them.
I have one cat who “dumbs it down” for the humans though. He makes sure I know that he knows what I said, by physical signs. I say to him: “oh, you’re sooo smart!” when really I know he’s probably thinking: “No, you humans are just THAT dumb that I have to spell it all out for you!” 
They can learn to mimic human sounds as well. I currently have and have had other cats who meow sounds similar to our words and they say them at appropriate times, so it’s obvious that’s what they are really trying to say. One of my current ones, who adores music, has even learned to mimic sounds of instruments in certain songs.
I don’t know if dogs ever do that or not. I just know that mine never have.
I have a parrot friend who most definitely always knows exactly what he’s saying and is not just repeating what he hears. And a horse I was friends with who belonged to some people I was trying to avoid, made it quite clear to me that he was NOT happy that I wasn’t paying any attention to him either.
And don’t let anyone tell you that animals don’t express jealousy, spite, etc. either. I have experienced it firsthand and so have others I have spoken to. I’m sure so have many of you.
And then there are people like Warrior who think..they understand us…but don’t have minds…? Lol..ok?
I guess that makes sense because I’m pretty sure I have a mind…yet I don’t understand you. -.-
And Creedo, I’m just wondering, what is the actual “experiment” here?