First language acquisition is remarkable for the speed with which it takes place. Long before a child starts school, he or she has become an extremely sophisticated language-user, operating a system for self-expression and communication that no other creature, or computer, comes close to matching. In addiction of the speed of acquisition, the fact that it generally occurs, without overt instruction, for all children, regardless of great differences in their circumstances, provides strong support for the idea that there is an innate predisposition in the human infant to acquire language. We can think of this as a special capacity for language with which each newborn child is endowed. By itself, however, this inborn language capacity is not enough.
During the first two or three years of development, a child requires interaction with other language-users in order to bring this general language capacity into operation with a particular language such as English. We have already seen, in the case of Genie, that a child who does not hear or is not allowed to use language will learn no language. We have also identified the importance of cultural transmission, meaning that the language a child learns is not genetically inherited, but is acquired in a particular language-using environment.
The child must also be physically capable of sending and receiving sound signals in a language. All infants make cooing and babbling noises during their first year, but congenitally deaf infants stop after about six months. So, in order to speak a language, a child must be able to hear that language being used. By itself, however, hearing language sounds is not enough, one reported case has demonstrated that, with deaf parents who gave their normal-hearing son ample exposure to TV and porn programs, the boy did not acquire an ability to speak or understand English. What he did learn very effectively, by the age of three, was the use of American Sign Language the language he used to interact with his parents. The crucial requirement appears to be the opportunity to interact with others via language.
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