Title: Development of speech intelligibility between 30 and 47 months in typically developing children: A cross sectional study of growth
Legend: Left – Growth curve and quantiles for single-word intelligibility. Right – Growth curve and quantiles for multi-word intelligibility.
Citation: Hustad, K.C., Mahr, T.J., Natzke, P., & Rathouz, P.J. (in press). Development of speech intelligibility between 30 and 47 months in typically developing children: A cross sectional study of growth. Journal of Speech, Language, and Hearing Research.
Abstract: Purpose – We sought to establish normative growth curves for intelligibility development for the speech of typical children as revealed by objectively-based orthographic transcription of elicited single word and multiword utterances by naïve listeners. We also examined sex differences, and we compared differences between single word and multiword intelligibility growth. Method – 164 typically developing children (92 girls; 72 boys) contributed speech samples for this study. Children were between the ages of 30 and 47 months, and analyses examined one-month age increments between these ages. Two different naïve listeners heard each child and made orthographic transcriptions of child-produced words and sentences (n = 328 listeners). Average intelligibility scores for single word productions and multiword productions were modeled using linear regression which estimated normal-model quantile age trajectories for single and multiword utterances. Results- We present growth curves showing steady linear change over time in one-month increments from 30 to 47 months for 5th, 10th, 25th, 50th, 75th, 90th, and 95th percentiles. Results showed that boys did not differ from girls and that prior to 35 months of age single words were more intelligible than multiword productions. Starting at 41 months of age, the reverse was true. Multiword intelligibility grew at a faster rate than single word intelligibility. Conclusions –Children make steady progress in intelligibility development through 47 months and only a small number of children approach 100% intelligibility by this age. Intelligibility continues to develop past the fourth year of life. There is considerable variability among children with regard to intelligibility development.
About the Lab: Katherine Hustad is professor of Communication Sciences and Disorders. Her research examines speech and language development in children with cerebral palsy, with a focus on improving treatment decision-making, clinical outcomes, and quality of life. Visit the Wisconsin Intelligibility, Speech, and Communication (WISC) Lab for more information. https://kidspeech.wisc.edu/