Infants who are deaf or hard of hearing go through critical sensitive periods for the development of vocabulary, grammar and the sounds of spoken English, according to a University of Colorado at 葫芦娃视频 professor.
Christine Yoshinaga-Itano, chair of the speech, language and hearing sciences department, presented "What the deaf child can't afford to miss: Language, Deafness and the Remarkable Infant" Feb. 17 at the annual meeting of the American Association for the Advancement of Science.
Thanks to advances in diagnostic testing, hearing loss can now be identified in children shortly after birth. For the first time in deafness research, the majority of children who are identified and receive intervention early for hearing loss demonstrated age-appropriate language levels, Yoshinaga-Itano said.
"Children with hearing loss born in Colorado hospitals that screened for hearing loss had an 82.4 percent probability of attaining age-appropriate language in the first five years of life, as compared to 31.6 percent of the non-screened group," she said. "These findings lead to a hypothesis that a sensitive period for access to language exists."
Yoshinaga-Itano's research showed that if children are diagnosed with hearing loss in the first six months of life, their eventual language levels were dramatically better than those who were diagnosed later. The first six months were a specifically sensitive period for vocabulary development.听
"Simply stated, the development of vocabulary, either through sign language or speech, is vitally important to children with hearing loss. The data indicated that sensitive periods for other aspects of language development had a longer time frame," she said. "Children with no speech in the first two years of life still had high probabilities of developing intelligible speech."
Vocabulary development, whether through sign language or speech, provides a gateway to other aspects of language. "For the child with a significant hearing loss, vocabulary becomes the foundation upon which all other aspects of language are built. This explanation for the sensitive period of access to language differs dramatically from the currently held belief that earlier identification of hearing loss results in language advantage because of access to hearing," Yoshinaga-Itano said.
Access to vocabulary can account for the language advantage of early-identified children with hearing loss whether or not they have access to hearing spoken English. The research results point to a hypothesis that the means by which the child obtains language is less important than the amount of language that is acquired through that means.听
An additional language pathway, called the "two modality sequential pathway," was identified through Yoshinaga-Itano's research. "This newly-identified pathway is exciting because it answers the question of whether children who use signing without speech can develop intelligible spoken English. These children started their language development through a visual/manual mode, acquiring vocabulary through sign language. Their language development was at low-average levels.
"They received a cochlear implant in the second year of life, or beginning of the third year. At the time of cochlear implantation, these children had minimal or no English syntax or morphology," said Yoshinaga-Itano .
"Within 12 to 18 months after implantation, the children transferred their sign vocabulary to oral speech. They mapped the sounds of English rapidly to the hundreds of vocabulary words that they used. Once the child understood the role of hearing to communication, this transfer occurred within approximately a 6 month to 12 month period," she said.
These children also present a new pattern of English language development, she said. "They use their vocabulary knowledge to accelerate learning the sounds of English which then accelerates learning English grammar. The normal pattern for hearing children is that speech-sound development leads to the development of vocabulary, which leads to the development of grammar."
Yoshinaga-Itano also found that the relationship between parent and child pragmatic language strategies and language outcome is very strong within the first two years but loses significance at later age levels. "Sensitive periods of language development are a complex web of interactions between the characteristics of the child, the characteristics of the parents and access to a complete language system," she said.