Speech rate, rate-matching, and intelligibility in early-implanted cochlear implant users

Abstract

An important speech-language outcome for deaf people with cochlear implants is speech intelligibility-how well their speech is understood by others, which also affects social functioning. Beyond simply uttering recognizable words, other speech-language skills may affect communicative competence, including rate-matching or converging toward interlocutors' speech rates. This initial report examines speech rate-matching and its relations to intelligibility in 91 prelingually deaf cochlear implant users and 93 typically hearing peers age 3 to 27 years. Live-voice spoken sentences were repeated and later transcribed by multiple hearing listeners. Speech intelligibility was calculated as proportions of words correctly transcribed. For speech rate-matching measures, speech rates (syllables/s) were normalized as percentages faster or slower than examiners' speech rates. Cochlear implant users had slower speech rates, less accurate and less consistent rate-matching, and poorer speech intelligibility than hearing peers. Among cochlear implant users, speech rate and rate-matching were correlated with intelligibility: faster talkers and better rate-matchers were more intelligible. Rate-matching and intelligibility improved during preschool, with cochlear implant users delayed by about a year compared to hearing peers. By school-age, rate-matching and intelligibility were good overall, but delays persisted for many cochlear implant users. Interventions targeting rate-matching skills are therefore warranted in speech-language therapy for this population.

FIG. 1.

Normalized speech rate for (a) preschool samples by testing time and (b) older samples. CI.1 = CI, time 1, etc., black dots = means, black bands = medians, boxes = quartiles 2-3, notches = 95% confidence intervals, horizontal line at 0 = SLP rate, shading = “on-target” range within 10% of SLP rates.

FIG. 2.

Distance from SLP rate for (a) preschool samples by testing time and (b) older samples. CI.1 = CI, time 1, etc., black bands = medians, boxes = quartiles 2-3, notches = 95% confidence intervals, shading = “on-target” range within 10% of SLP rates.

FIG. 3.

Rank-ordered individual participants' intelligibility scores, CI (gray) overlaid on TH (white), (a) preschool mean intelligibility by testing time, (b) older perfect-sentence intelligibility. Reference lines at 70% indicate good performance.