Is the spontaneous speech of 7-year-old cochlear implanted children as intelligible as that of their normally hearing peers?

Objectives: Studies on speech intelligibility usually focus on either individual words, sentences or longer sequences of speech. Since these different kinds of speech samples can be judged using different methodologies, a difference in the reported intelligibility scores can either be due to the difference in the type of sample or methodology. The present study compares the speech intelligibility of seven-year-old children with a cochlear implant (CI) with that of their normally hearing (NH) peers. The first aim is to compare the intelligibility of short sentences and longer sequences of speech using the same methodology. Secondly, it has been suggested that i.a. advances in CI technology and changes in candidacy criteria may have had a positive influence on the intelligibility of children with CI. In order to assess this issue, the intelligibility of seven-year-olds implanted ten years apart will be compared. Method: The speech of two cohorts of early implanted children with CI (n = 16) and NH peers (n = 16), matched on several criteria but implanted in different years, was collected. More specifically, short and longer samples were selected from recordings of a wordless picture book retelling. Both types of samples were judged on a visual analogue scale by 105 inexperienced listeners. Results: The results showed that the intelligibility of children with CI was lower than that of their NH peers. Moreover, longer samples were significantly more intelligible than short samples for both groups. No significant effect was found between the two cohorts of children with CI. However, the intelligibility of three out of four children with CI was found to be on a par with that of their NH peers, indicating a large amount of variability between subjects. Conclusion: Listeners ascribed higher intelligibility to longer samples than to short samples, despite the fact that both types were extracted from the same recordings and listeners followed the same judgement procedure. The amount of context thus facilitated speech decoding. No effect of the calendar year of implantation was found, suggesting that e.g., the evolution in CI technology did not have a significant impact on CI users' intelligibility after six years of device use.