OK, so a border collie named Rico can identify 200 toys by spoken word, or roughly the vocabulary of a 3 year-old human. Tom rightly wonders why a dog needs 200 toys. You might ask the same thing about three-year old humans -- my grandchildren, for example.
Does Rico's feat mean dogs are smarter than cats? As far as I know, no cat has demonstrated language responses remotely as numerous as Rico's. But as the bumper sticker says: Dogs have owners, cats have staff. What self-respecting cat would humiliate itself by running to fetch one of 200 toys to please some "owner's" ego?
With so little access to the inner lives of animals, it is exceedingly difficult to access language ability. Rico's talent is more than matched by chimps, and equaled by "bird-brained" parrots. Researchers have a long way to go before we understand fully even how human children acquire language.
Scientists spend a lot of time teaching experimental animals to run mazes and and other tricks of pseudo-human behavior; we force the animals into a human template, rewarding them with food when they conform or zapping them with an electric charge when they fail. It may be that we have more to learn from them than they have to learn from us.
For my money, one of the most engaging books I have ever read about animal communication is Alan Powers' Bird Talk: Conversations With Birds. Powers teaches English at Bristol Community College in Fall River, Massachusetts. He is an avid birder, scholar, poet, and knowledgeable musician, all of which he brings to bear on his topic. His little book doesn't provide answers to the deepest questions about animal communication, but it leaves the reader in little doubt that real, two-way communication is possible with other species.