There's an interesting article about the history of research into animal intelligence, cognition, and communication in last week's New Yorker but it's mostly about Alex the Parrot:
Dead, unfortunately. One thing I found interesting is that some of the nay-sayers dismiss the research by saying that it was just a single bird. Huh? It's still a fucking bird. There seems to be a strong "IT'S NOT POSSIBLE" contingent. More to investigate.