Stages of Language Development: Sounding Like an Adult

As children grow and develop, their phonology, morphology, and syntax get closer and closer to the adult language. There are no clearly agreed upon stages beyond the acquisition of morphological rules, but there are many interesting observations that have been made about children’s learning of the more complex grammatical structures that become part of their internalized grammars, such as negation (She can’t go); questions (Can she go?); coordination (The boy cried and the girl laughed); subordinate clauses (The boy cried because he was sad); and the passive voice (The cat was chased by the dog).

To give you an idea of the kinds of information children must learn, consider the following task.  In order to make a question in English, you must know the distinction between a helping verb and a main verb, because helping verbs merely change place with their subjects to ask a question, while sentences without helping verbs must insert the helping verb do: Can Mary see him? vs. Did Mary see him? Further, in order to switch the order of the subject and the verb, you must be able to identify the subject constituent, even if it is long and complex: The boy who just joined our class today can come to visit becomes the question Can the boy who just joined our class today come to visit? Questions such as these are called yes-no questions, because they can be answered yes or no. There is another type of question in English, called a wh- question, which asks for a specific piece of information: Who cried? When did they leave? Why are you sad? What did you bring me? These, too, generally require that you distinguish between a main verb and a helping verb, but in addition they require knowing that the question word goes at the front, no matter what part of the sentence you are questioning: You are reading what? becomes What are you reading? Negation follows similar restrictions in English, inserting not after a helping verb and requiring the insertion of do if no helping verb is present: He will go becomes He will not go, but He went becomes He did not go. Thus, before children can utter adult questions and negation, they must master a great deal of sophisticated information: They must learn that language works by constituents, not by individual words; that different word orders can signal different functions (statements vs. questions); that certain words can signal particular functions, such as not and the wh- words; that morphemes with no meaning must be added to certain grammatical structures (Did he go?); and that constituents may need to be moved from their customary positions in sentences. For example, subjects may have to follow the verb (Is he here?), and direct objects may have to be placed at the beginning of the sentence (What did you see?).

Another milestone in child language acquisition occurs when children learn to combine more than one sentence together. They begin with coordination, adding one sentence to another with and, and eventually progress to subordination, inserting one sentence inside another, as in I know that you are ready. One widely studied type of subordinate clause is the relative clause, used to describe a noun, as in That is the boy who took my candy, in which the relative clause who took my candy describes the boy. Children apparently begin to produce and understand relative clauses when they are about three years old, but they typically do not fully master them before they go to school.