Children overgeneralize the rules of the grammar that guide their spoken language, resulting in speech language errors. the predictability of these errors illustrates an important point regarding language development, namely:
language development is guided by implicit grammatical rules that children use to produce new sentences and verbal constructions they've never heard before.

Language development is guided by implicit grammatical rules that children use to produce new sentences and verbal constructions they've never heard before.

Explanation:

This has been studied by many linguists, such as Chomsky. He developed a theory or a problem called "Plato's problem" (theory of language acquisition) in which he explains that under poor stimules of their enviroment children learn how to speak the language properly due to an inherent grammatical construction that the human being has. This is called universal grammar. This allows children (any person that speaks a language) to produce sentences they have never heard before.