Speech Development Between 30 and 119 Months in Typical Children I: Intelligibility Growth Curves for Single-Word and Multiword Productions.
Katherine C Hustad, Tristan J Mahr, Phoebe Natzke and 1 others
PMID 34491793WHAT IT FOUND
Children speak more clearly in sentences than in single words.
Average kids hit 90% clarity in sentences by age 5, but lower-performing peers may not until age 7. Single-word clarity lags behind, requiring more precise sound production.
Key findings
01Multiword utterances are consistently more intelligible to unfamiliar listeners than single words from age 4 onward, with a stable advantage of about 5% for average children.
02Children in the 5th percentile for development reach 90% intelligibility for multiword utterances at about 7 years of age, two years later than average children.
03Intelligibility growth rates are similar across development levels, but lower-performing children experience their steepest growth later than average peers.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study used a cross-sectional design, so it compares different children at different ages rather than tracking the same children over time. The sample consisted only of typically developing children from the upper midwestern United States, mostly from educated, middle-class families. Intelligibility was measured in a quiet laboratory setting with unfamiliar listeners, which likely underestimates how well children are understood in everyday life with familiar listeners and context. The data does not include children with speech disorders, so it does not validate cut-points for identifying clinical impairment.
Declared interests
The study was funded by grants from the National Institute on Deafness and Other Communication Disorders and the National Institute of Child Health and Human Development. No commercial conflicts of interest are reported.
The easy way to misread this
Do not use these percentiles to diagnose speech disorders in children with known developmental delays. The data comes from typically developing children, and children with conditions like cerebral palsy may have different growth patterns and timelines.