Early manual communication in relation to the deaf child's intellectual, social, and communicative functioning.

The basic impoverishment of deafness is not lack of hearing but lack of language. To illustrate this, we have only to compare a 4-year-old hearing child, with a working vocabulary of between 2,000 and 3,000 words, to a child of the same age, profoundly deaf since infancy, who may have only a few words at his command. Even more important than vocabulary level, however, is the child's ability to use his language for expressing ideas, needs, and feelings. By the age of 4 years, the hearing child in all cultures has already grasped the rules of grammar syntax that enable him or her to combine words in meaningful ways.