Longitudinal changes in articulation rate and phonetic phrase length in children with speech delay.

This study examined long-term changes in articulation rate (the pace at which speech segments are produced) and phonetic phrase length in the conversational speech of two groups of children with speech delay (SD) of unknown origin. Initial testing for both groups occurred at preschool age, with follow-up testing conducted for the Early Follow-Up Group (n = 17) at age 9 years and for the Late Follow-Up Group (n = 36) at age 12-16 years. At follow-up testing both groups produced significantly faster articulation rates (measured in both syllables per second and phones per second) and significantly longer phonetic phrases (measured in both syllables and phones) than at initial testing. Articulation rates at both test times were also judged to be similar to published values from typically developing children of similar ages when measured in syllables per second. However, findings for rate in phones per second suggested that at least at initial testing the children were articulating speech at a slower rate than their typically developing peers. This latter finding, however, may have been an artifact of the high frequency of errors--such as cluster reduction and final consonant deletion--observed in the initial samples. It would appear, therefore, that children with SD of unknown origin may start out with slower than normal articulation rates but eventually catch up to their typically developing peers.