On the concept of dog, and other mysteries

It's hard sometimes to understand that abstraction and concreteness exist along a continuum. Is "dog" and abstract or concrete term? "Cocker Spaniel"? "Spot"?

How do toddlers so uncannily differentiate between dog and cat? How do they group Great Danes and toy breeds so effortlessly? I would think some dogs might look like cats to the young eye. Pugs, for example.

Milosz was having similar confusion when I busted him in Chapel Hill back in '89.

Graham, similarly, has an uncanny ability to differentiate junk food from other food. He eats a very restricted diet, and if you put something reasonably healthful in front of him he'll throw it on the floor. But potato chips, cupcakes, by God, he picks up the first one he sees in his life and mashes it into his mouth. How does he distinguish junk from healthful? Just by watching other kids? Was it the sprinkles?

One of the great mysteries.