Chaser the border collie knows 1,000 words. He can pick a toy – correctly – out of a thousand just by being asked to find it. He can dig out "Inky," bring "lips" and find "tennis."
It's really quite extraordinary to watch – almost as extraordinary as the clues Chaser might be giving to scientists. Is it possible for dogs expand their vocabulary? Understand elementary grammar? Make inferences? Scientists can only hope.
A story in The New York Times (http://www.nytimes.com/2011/01/18/science/18dog.html?_r=1) points out, though, that Chaser is a border collie – a breed that is diligent and always willing to please its owner. The experiments might not work on, let's say, a husky.
Denali might know 50 words. Might. He regularly responds to (or chooses to disregard): come, sit, down, stay, off, left, right, stop, let's go, outside, go bed, go poop, drop it, leave it, kisses.
Oh, and Denali's favorite: "Are you hungry?" Uttering that phrase always elicits a reaction. Just watch.