Speech production accuracy in children with Down syndrome

This project explores speech production accuracy in school age children with Down syndrome, its relationships with hearing, language, and reading ability and change in speech production accuracy over time.

Most children and young people with Down syndrome take longer developing clear spoken language and tend to have ongoing speech difficulties. This is frustrating for them and means they are not always understood. The speech sounds in the language vary in difficulty and most children learn them in a predictable order with the easiest first. It takes all children a number of years to develop clear spoken language, but we have little data on how children with Down syndrome progress with speech over time.

This study analysed video recordings of the speech of 50 children with Down syndrome (5-10 years of age at the start) as they completed a standardised articulation test at two time points approximately 21 months apart. The children’s hearing status was recorded, and they also completed a range of measures of language, reading and non-verbal ability.

The study addressed the following questions:

  1. To what extent do children with DS demonstrate speech production difficulties?
  2. How does speech production accuracy relate to other variables including hearing status, and language and reading skills?
  3. Does speech production accuracy change over time?

The speech data showed that most children in this age range were mastering the speech sounds in much the same order as other children but at a much later age; that is, they had mastered most vowel sounds but more of the easy consonant sounds than the later ones. There were considerable individual differences with some children producing most consonants accurately and some very few with the average for the group being around 42-43% of consonants correct at both time points. This means that there was little improvement in their speech production over 21 months though there was a significant correlation with age and evidence that girls were progressing faster than boys.

Hearing data was from parent reports and effect sizes showed some evidence of hearing impairment influencing speech production, but the differences did not reach statistical significance. Speech production accuracy at the first assessment point was significantly related to measures of receptive vocabulary (words understood), phoneme blending and single word reading. This relationship between speech skills and language and reading development needs further longitudinal investigation to learn more about the ways in which they influence each other. The speech and language therapy the children in the study were receiving was not documented but the results do suggest that a therapy focussed on speech development should be assessed as a small number of studies suggest it could be effective in improving speech and possibly language development.


  • The National Lottery
  • Down Syndrome Education International


Burgoyne, K., Buckley, S.J. & R. Baxter. R. (2021) Speech production accuracy in children with Down syndrome: relationships with hearing, language, and reading ability and change in speech production accuracy over time. Journal of Intellectual Disability Research, 65, 1021-1032. https://doi.org/10.1111/jir.12890