Learning how to write a coherent, effective text is a difficult and protracted achievement of cognitive development that contrasts sharply with the acquisition of speech. By the age of 5, spoken language is normally highly developed with a working vocabulary of several thousand words and an ability to comprehend and produce grammatical sentences. Although the specific contribution of a genetic predisposition for language learning is unsettled, it is apparent that speech acquisition is a natural part of early human development. Literacy, on the other hand, is a purely cultural achievement that may never be learned at all. Reading.
