The Child must determine which referents belong within a Symbol's umbrella of meaning.
Now the struggle begins for the child to determine just which referents are to be included within the umbrella of the symbol.
Their first inclination is to over generalize and name anything that walks on for legs a dog.
Hence, a cat, a goat, a horse and a cow may all be called "dog" by the two year old.
Then comes a process of refinement as parents read to, and correct the child's communication errors.