Age Is Important In Language Development In Cochlear Implant Users
INDIANAPOLIS -- The younger a profoundly deaf child is when he receives a cochlear implant, the more apt he is to have his speech development and perception match his chronological age, according to a study published by Indiana University School of Medicine researchers in the March 1 issue of Psychological Science.
The study, conducted by Mario A. Svirsky, Ph.D., associate professor of otolaryngology at the IU School of Medicine, and his colleagues, explores whether cochlear implants enhance English language development in prelingually deaf children. A cochlear implant is a device that electrically stimulates the auditory nerve to produce hearing perceptions in some profoundly deaf and hearing-impaired individuals.
Critics of the procedure claim that no study has documented a single case of a child who has developed a linguistic system based on input from an implant. This study, the researchers say, provides evidence that cochlear implants do enhance language development.
The "language gap" between hearing children and hearing-impaired children can be drastically narrowed if the child receives a cochlear implant at an early age, says Dr. Svirsky.
"Children who are born deaf or who become profoundly deaf before the age of three typically experience significant delays in their acquisition of English language skills," says Dr. Svirsky, the lead author. "The gap between a hearing impaired child's chronological age and his language age typically continues to increase as the child grows older. However, we have found that when a child receives a cochlear implant, the child begins to develop language skills at about the same rate as a child with normal hearing. In other words, the gap stops growing. Some children with cochlear implants develop language at a faster rate and actually start to approach the linguistic levels of their age peers who have normal hearing."
The researchers followed 70 children who had received cochlear implants. The children were tested four months before receiving the implant and again at six, 12, 18, 24 and 30 months after implantation.
All the children showed a gap between their language age (skill level) and their chronological age, but the gap was greater for older children. Prior studies have shown that the gap for deaf children continues to widen as they age. Language perception and verbal skills in children with cochlear implants involved in this study showed marked increases in their abilities, and the gap between hearing children and children with implants continued to narrow as time passed after implantation.
"The rate of language development in the profoundly deaf children after implantation was quite close to that of children with normal hearing, and it exceeded the development rate expected from unimplanted profoundly deaf children," Dr. Svirsky said. "Some children in the experimental group showed above-average rates of language acquisition and achieved scores that were comparable to those of their hearing peers after only 2.5 years of using their cochlear implant."
Assisting Dr. Svirsky with the study from the IU Department of Otolaryngology-Head & Neck Surgery were Amy M. Robbins, M.S.; Karen Iler Kirk, Ph.D., assistant professor and Psi Iota Xi Scholar; and Richard T. Miyamoto, M.D., Arilla De Vault Professor and department chairman; and David B. Pisoni, Ph.D., Chancellor's Professor at the IU Department of Psychology at Bloomington.
National Institutes of Health grants supported the study.
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