"My big dog often behaves as if he's dumb as a post, but my small dog is an Einstein." "Size doesn't matter. My big and small dogs are smart on some tasks and not so smart on others." "Molly, my tiny ...

If you’ve ever noticed your friend’s tiny Chihuahua still bouncing around well into its teens while your neighbor’s Great Dane started slowing down after just a few years, you’re not imagining things.