Speech perception and vocabulary development in Mandarin-speaking children with cochlear implants

Abstract

Cochlear implants (CIs) are effective in enhancing hearing in people with severe to profound hearing impairment resulting from a loss of sensory function in their cochlea. Increasing numbers of Mandarin-speaking children with hearing impairment are being implanted with CIs in mainland China, and yet, speech perception and vocabulary development in this population have not been well documented. Because of linguistic, social, and economic differences between English-speaking countries and mainland China, it remains uncertain whether Mandarin-speaking children with CIs obtain similar benefits and develop speech perception and vocabulary at similar rates to their English-speaking counterparts and same-aged peers with normal hearing (NH). The aim of this thesis is to investigate speech perception and vocabulary development in Mandarin-speaking children with CIs and the factors influencing those outcomes. Four studies were carried out. In the first two studies, early speech perception and vocabulary development in the first year of these children’s CI use were examined, with the results compared with those from research on English-speaking peers using CIs or same-aged peers with NH. Both of these studies were longitudinal, allowing a determination of how speech perception and vocabulary skills change over time. In the third study, the factors influencing speech perception and vocabulary development in Mandarin-speaking pediatric implantees with a longer duration of CI use (i.e., one to three years) were examined. Finally, the fourth study examined tone and sentence perception in noise in Mandarin-speaking children with one to four years of CI use. The second pair of studies were cross-sectional in nature to ensure sufficiently large samples to obtain inferential statistics (i.e., via structural equation modeling). Taken together, the results of the four studies carried out for this thesis suggest that Mandarin-speaking children benefit from CIs to the same extent as their English-speaking counterparts and develop vocabulary at a faster rate than their same-aged peers with NH, at least during the first year of CI use. In addition, a younger age at implantation, a having a hearing aid trial before implantation, a higher maternal education level (MEL) and a better pre-implant hearing level were all found to contribute significantly to speech perception and vocabulary development in Mandarin-speaking children with CIs. This thesis demonstrates for the first time that Mandarin-speaking children can catch up with their NH peers in speech perception and vocabulary following a longer duration of CI use. In addition, both outcomes can be further improved in these children by administering a hearing aid trial before implantation, ensuring early implantation and empowering families by training mothers with a low MEL in how to interact with their children after implantation. However, the impact of the latter factor requires further verification. The four studies reported herein evaluated speech perception and vocabulary development only in children with fewer than three years of CI use. Hence, a further longitudinal study documenting ongoing speech perception and vocabulary development in these children over a protracted period of time is needed because the rates of advancement in both outcomes may decrease with lengthier CI use.