The development of speech production abilities in children with Down syndrome

Since impairments in articulation are common in the population with Down syndrome, it was hypothesized that deficits in speech timing would also occur. Acoustic analysis was used to investigate speech timing in two groups of children with Down syndrome (DS), with mean ages of 7;0 and 12;0 years, and two control groups of age-matched normal (N) children. Acoustic measurements were made of 12 CVC (consonant-vowel-consonant) syllables to determine initial consonant closure duration, voice onset time, and vowel and word duration. Maximum syllable repetition rates were also determined via acoustic analysis. Temporal variability for each of the segments and maximum syllable repetition rates were calculated. Substitution analyses of single-word articulation testing provided general information about articulatory accuracy. Statistically significant differences between DS and N groups were evident for temporal variability, articulatory accuracy and syllable repetition rate, but not for segment duration. Selected speech timing and maximum syllable repetition rate measures emerged as successful predictors of single-word articulatory accuracy in multiple regression analyses. The use of acoustic analysis to examine the speech timing of children with DS, in conjunction with traditional articulation and maximum syllable repetition rate assessments, provides a more complete and integrated profile of the speech production skills of this population than has been previously available.