Read this excerpt from "Are Dogs Dumb?" by Karen Hopkin.
And how come we thinks dogs are so smart? Sure a dog might be clever enough to fetch his leash when he wants to go out. But the same mutt might also bark at a vacuum cleaner and spend a whole hour chasing his own tail. Is Rover really any brighter than a hamster, a chicken, or a kid who's always eating Play-Doh? How can you measure an animal's brain power?
What is the author's purpose in this paragraph?