As far as can be ascertained, the perceptual level of a child’s awareness is
similar to the awareness of the higher animals: the higher animals are able to
perceive entities, motions, attributes, and certain numbers of entities. But
what an animal cannot perform is the process of abstraction—of mentally
separating attributes, motions or numbers from entities. It has been said that
an animal can perceive two oranges or two potatoes, but cannot grasp the
concept “two.”