(Betsy, another border collie, has been shown to have a vocabulary of over 340 words, but we'll stay with Rico's story for now.)
Fast mapping, as referenced above, is the ability to immediately assign meaning to a word never heard before. Rico is the first animal that has passed that test, previously thought to be possible only by human toddlers. Fast mapping is not merely a function of memory, it shows logical thought as well.
"It's like he's saying to himself, 'I know the others have names, so this new word cannot refer to my familiar toys. It must refer to this new thing.' Or it goes the other way around, and he's thinking, 'I've never seen this one before, so this must be it.' He's actually thinking." --biologist Julia Fischer, quoted in the Washington PostStudies done with Rico were specifically designed to eliminate the "Clever Hans" effect, and Rico passed without a problem. (Clever Hans was a horse who was supposed to be able to do arithmetic, but was actually picking up subconscious body language from his trainer. His story is always brought up whenever a new example of animal intelligence is discussed.)
Why does Rico have such a large vocabulary and an affinity for words? The reason is probably that his owners started to teach him the names of toys and various everyday items at the age of 10 months. At that time Rico was ill and unable to get exercise. They started the mental exercises to keep him from getting bored. Games were developed based on retrieving toys from a box or locations in other rooms. In other words, somebody took the time to pay attention to this dog and actively engage his mind. It obviously paid off.
In the same issue of Science magazine in which Rico's story was first published, Paul Bloom tries to disparage the dog's achivements. He writes:
Rico is 9 years old and knows about 200 words, whereas a human 9-year-old knows tens of thousands of words. And children can speak; Rico cannot.That sounds like frantic desperation to cling to the erroneous notion that only humans have language. A human 9-year-old may know thousands of words in English, but how many does he know in dog-ish? I know I was all full of myself when I learned one word in tiger-ish--how brilliant does that make me in comparison with a tiger?
And to say that a dog cannot speak just means that Mr. Bloom isn't listening.