To What Extent Does Speech Develop After Implantation?

“Speech Development in Children after Cochlear Implantation”
Author: Bakhshaee et al.
Publication: European Archives of Oto-Rhino-Laryngology
Date: July 2007

This paper addresses the topic of speech development in prelingually-deaf children who receive cochlear implants. The authors point out that while improvement in speech perception (or the ability to understand speech) is well documented, improvement in spoken language has not been as well studied. This is obviously a major concern for parents whose children are deaf and are likely candidates for cochlear implants. Part of the controversy among the deaf community surrounding cochlear implantation is that the implants only serve to make recipients less proficient at something that “normal” people can do, while before the implants they were perfectly proficient at other forms of communication (like sign language or lip reading). However, the paper suggests that children who are implanted gain a fairly advanced mastery of speech.

The paper details a study of 47 deaf children who received cochlear implants and whose speech development was tracked for up to five years after implantation. Speech development was quantified using the speech intelligibility rating (SIR). SIR rates speech from 1 to 5, with 1 being unintelligible and 5 being completely intelligible and easily understood in everyday contexts. All of the children started out with SIR categories of 1 or 2. After only one year with the implant, the average SIR rating for the children jumped up to 3 (where speech is intelligible if the listener concentrates and lip-reads). The average SIR rating after two and three years was 4 (where speech is intelligible if the listener has a little experience with a deaf person’s speech). Amazingly, the average SIR rating after four or five years was 5, and no children had a rating below 4. This seems to indicate that after four or five years, prelingually-deaf children can obtain a significant mastery of the spoken language.

There are several issues with the paper, however. The number of children that remained in the study dropped as the years passed, and only 9 children remained at the end of five years. Also, as the paper acknowledges, the differences between years 3 and 4 and 4 and 5 were not statistically significant, probably because of the extremely small number of children that remained in the study for 4 or 5 years. Finally, even completely intelligible speech (SIR of 5) doesn’t necessarily mean that the children still didn’t have a noticeable speech impediment, which is the reason why the deaf community views cochlear implants as such a controversial topic. However, the paper notes that speech development does not halt after five years, and that it is possible that the children had not reached their full speech intelligibility at the end of the study. Further studies are needed, but at the very least this paper reveals that cochlear implantation can have a much more profound impact on speech development in children than was previously believed.