Generally, children learn the syntax of their language through the process of induction. It is a process of self-discovery through observation and comparison of different sentences, but not artificial teaching in classroom.

When the child interacts with others, the child compares the sentences they made with those he/she heard, and then finds out the difference between the sentences. Through this process, the child then works out the language rules behind the sentences. The case of learning negation is one of the examples.

Usually, the process of learning negation can be divided into several steps.
At first, the child simply adds negative marker, not, in front of the verb, say wanted, without changing the tense. Then, by observation and comparison, the child starts to add auxiliary do in font of the negative marker. The phrase then becomes “do not wanted something…”. Next, the child moves the tense marker -ed from the verb want to follow do. At last, the child is able to turn *doed into did, and make some corrections on the negative agreement, the phrase then become “did not want anything…” .

Obviously, nobody teaches the child about the rule to create a negative sentence, but the child manages to do so. It is because the child is learning by comparing the sentences they made with other people’s sentences. By picking out the difference between these sentences, the child can easily work out the rules in forming a negative sentence. It is a process of observation, comparison and understanding, and we call this process induction.

The learning of negation is not learned through the process of explication/explanation, because the grammar problems involved in negation are some abstract concepts, which are difficult for a child to understand. Thus, the most effective way to learn negation is through induction, when the child interacts with others, but not explication. In fact, # those whose learn language through teaching process tend not to develop the proficiency of those who learn the language from long periods spent in social interaction
and daily use of the language. ( Yule, p191 )

Bibliography
# Yule, Geogre. The Study of Language, Cambridge University Press, p191