I read this book called "the Inner Life of Animals." Now it's one of my core beliefs that they are, in fact, more intelligent than give them credit for. And I can't ignore my own observations:
-Ever since my dog Dexter died, one of my other dogs, Rose, refuses to sleep in a bed that she and him used to all the time. Rubecca, the most antisocial dog you will ever meet, (for a dog that's probably never been abused) suddenly became very social.
-If I'm having a bad day, sometimes my cat, Tom, will sit outside my bedroom door meowing until I let him in, and then he jumps up on me and pretty much gives me a hug.
I think the language barrier is what's really in the way; maybe they aren't quite as developed mentally as humans are, but we're also not used to relying only on body language for communication, and that's an animal's primary means of communication.