Our #Education21 campaign highlights how educational research has helped us to better understand the needs of young people with Down syndrome and how it is improving outcomes for many thousands of children today. Find out more...

#8. Developing clear speech is a particular challenge

Most people with Down syndrome find it difficult to speak clearly enough to always be understood by everyone around them. These communication difficulties can present obstacles to learning, friendships, employment and independence. Research has begun to explore the nature of these speech difficulties and to inform therapies. More research is need to explore effective interventions.

What educational research has shown

Most children and adults with Down syndrome have speech production difficulties that lead to them not being understood. Libby Kumin surveyed over 900 parents and 60% reported that their children 'frequently' had difficulty being understood and a further 37% reported that their children 'sometimes' had difficulty being understood.[1] This degree of unintelligibility can be frustrating and seriously impairs communication in all aspects of daily life. Typically developing children are largely intelligible by about 4 years of age.

While there is a considerable amount of research on the language development of children with Down syndrome (the way they learn to understand and use words, sentences and grammar to communicate), there is only a small amount of information on the reasons for their speech intelligibility issues.[2 - 4]

Researchers have identified that producing clear sounds, syllables and words (articulation and phonology) is a challenge. Studies report that the errors patterns seen can be delayed (similar to young typically developing children's speech patterns) or deviant (show unusual errors). There is also a tendency for the speech sound errors to be inconsistent.[5] In addition to difficulties in saying sounds and words accurately, some 47% of individuals with Down syndrome have dysfluencies (such as stuttering) compared with 1% in the general population.[1]

Little is known about the reasons for this pattern of speech difficulties, but there have been a small number of intervention studies each showing small gains in sound or word production.[6 - 9] One study indicated that as the children's phonology improved they began to be able to produce longer utterances.[7]

How this is helping

Improved understanding of the speech difficulties experienced by children with Down syndrome has informed early intervention and speech therapy recommendations, and the development of resources to support regular speech practice.

Unanswered questions

Future research is needed to:


  1. Kumin, L. (1994). Intelligibility of speech in children with Down syndrome in natural settings: Parents' perspective. Perceptual and Motor Skills, 78, 307-313.
  2. Stoel-Gammon C. Down syndrome phonology: Developmental patterns and intervention strategies. Down Syndrome Research and Practice. 2001;7(3);93-100. https://library.down-syndrome.org/reviews/2075/
  3. Stoel-Gammon, C. (2003) Speech acquisition and approaches to intervention. In Rondal, J & Buckley, S Eds. Speech and language intervention in Down syndrome. Whurr: London, UK
  4. Bray, M. (2008) Speech production in people with Down syndrome. Down Syndrome Research and Practice, 12(3). https://library.down-syndrome.org/reviews/2075/
  5. Dodd, B.J. & Thompson, L. (2001). Speech disorder in children with Down's syndrome. Journal of Intellectual Disabilities Research, 45, 308-316.
  6. Dodd, B., McCormack, & Woodyatt, G. (1994) Evaluation of an Intervention Program: Relation Between Children's Phonology and Parents' Communicative Behavior. American Journal on Mental Retardation, 98(5), 632-645.
  7. Cholmain, C.N. (1994) Working on phonology with young children with Down syndrome. Journal of Clinical Speech and Language Studies, 1, 14-35.
  8. Dodd, B. Crosbie, S. (2005) Phonological abilities of children with cognitive impairment, In Dodd, B. (Ed.) Differential diagnosis and treatment of children with speech disorders. (pp.233-243) London: Whurr.
  9. Van Bysterveldt, A., Gillon, G & Foster-Cohen, S. (2010) Integrated speech and phonological awareness intervention for preschool children with Down syndrome. International Journal of Language and Communication Disorders, 45 (3) 320-335.