I dunno how to draw a clear line between reading and memorization for kids (which I don't have). My nephew started "reading" before age 2 if you count looking at flashcards without pictures and being able to say the word. He also was able to associate such words with actual things. So he could "read" the word "dog" off a flashcard and also recognize that the family pet was a dog.
He (my nephew, not the dog, lol) loves books. He'll grab a bunch of them, set them down by a grownup. That's our cue to sit down, so he can back into our laps and have us read together. It's the only time he'll sit still.