That’s a tough one. I don’t thing our brains work on exemplars but rather on prototypes, which are amorphous “similars”.
This is why to a 2 year old, a horse can be a dog. A cat can be a dog. a Table may even be a dog.
Dog may be their category for four legged things with connected surfaces on top
I mean we probably do both but I think prototypes are primary because they cover the most territory with the most efficient (least) mental effort