A child was walking down the street with his mother and called the black top "tarmacs." Presumably, he added the "s" because it was a long road. What does this reveal about how children learn language?

What will be an ideal response?

The child invented ‘tarmacs" by adding an "s," even though the plural of tarmac does not require adding an "s." He had not learned this word by hearing it in his environment; instead he must have a language acquisition device that allows him to generate the rules of language. In this case, he had not learned the exception to the rule