The receptive language, the understanding of the word of the others, has a gradual development, beginning to the 6 months. Nevertheless, the expressive language, the production of words, moves quickly after its beginning in around a year of age, with a “explosion of the vocabulary of the acquisition of words fast-in half of the second year. This extension of the vocabulary is closely tie to the ability to repeat the words and allows to the fast acquisition of skill in its norms pronunciation. Grammatical and combinations of words appear in around two years of age. The dominion of the vocabulary and the grammar to continue gradually through the preschool and scholastic years. The adolescents still have vocabularies smaller than the adults and the experience more difficulty with constructions like the passive voice.

The babies of a month of age sounds can produce “ooh” that seem to arise from the leisure interactions with the caretakers in a mutual “dialogue”. According to Stern, this process is the communication of infantile affection between adults and in a mutual and rhythmic interaction. The attunement and the “glance of connection” in which young and adult it acquires different think that to anticipate giving and to take from the later dialogue.

From babies of 6 to 9 months to produce more vowels, some consonants and “echolalia” or the frequent repetition of sounds like “dadadada” that seem to later have some phonetic characteristics of the speech. One thinks that a crucial part of the development of the speech is the time that dedicates the caretakers “to guess” what their children are trying to communicate with which Integra to the boy in its social world. The attribution of intentionality to the statements of the boy who has been called “shared memory” and forms a complex series of the actions, intentions and actions in answer of unexpected way.