Language development in profoundly deaf children with cochlear implants

Abstract

Although cochlear implants improve the ability of profoundly deaf children to understand speech, critics claim that the published literature does not document even a single case of a child who has developed a linguistic system based on input from an implant. Thus, it is of clinical and scientific importance to determine whether cochlear implants facilitate the development of English language skills. The English language skills of prelingually deaf children with cochlear implants were measured before and after implantation. We found that the rate of language development after implantation exceeded that expected from unimplanted deaf children (p < .001) and was similar to that of children with normal hearing. Despite a large amount of individual variability, the best performers in the implanted group seem to be developing an oral linguistic system based largely on auditory input obtained from a cochlear implant.

Fig. 1

Language age as a function of chronological age for the 23 cochlear implant users whose data are shown in Figure 2, prior to implantation (black circles), and for the 113 unimplanted deaf children (white circles) in a previous study (Svirsky, in press). The dashed line shows a linear regression of the expressive language scores by chronological age. The mean values for children with normal hearing fall on the solid diagonal line, where language age is equal to chronological age.

Fig. 2

Average language age as a function of chronological age for the 23 cochlear implant (CI) subjects before implantation and at three intervals after implantation (black circles). The white circles represent the expressive language growth predicted for these same children, had they not received cochlear implants. The solid diagonal line illustrates language growth expected of an average normal-hearing child.

Fig. 3

Average gains in language age for each 6-month period during the first 2.5 years postimplant for the cochlear implant users. The number of children evaluated at each interval (N) is shown below the x-axis. Also shown are gains expected from normal-hearing children and from unimplanted, profoundly deaf subjects.

Fig. 4

Individual data measuring changes in language abilities for cochlear implant (CI) users between 2 and 2.5 years postimplant. The two black lines under the diagonal indicate −1 and −2 standard deviations below the mean for the normal-hearing population.

Fig. 5

Language quotient, or the ratio between language age and chronological age, as a function of speech perception performance for children who had used a cochlear implant for 2 years. White and black circles represent users of total communication (TC) and oral communication (OC), respectively. The lines in the graph show the best-fitting regression functions, and the insets show the correlations between speech perception and language quotient for the two groups.