Intelligibility in Context Scale: Growth Curves for Typically Developing English-Speaking Children Between Ages 2;6 and 9;11.
Jennifer U Soriano, Tristan J Mahr, Paul J Rathouz and 1 others
PMID 37390405WHAT IT FOUND
Typically developing children's parent-rated intelligibility scores rise slowly with age, reaching a ceiling of 5 by 6;6.
Children aged 6 and older scoring below 4 warrant a comprehensive speech evaluation, while younger children scoring 3 or 4 may just need monitoring.
Key findings
01The median ICS composite score for typically developing children reached the maximum score of 5 just before the age of 6;6.
02Children in the lowest percentiles (5th and 10th) had ICS composite scores ranging between 3.23 and 4.45 across the entire age span of 2;6 to 9;11.
03Parents consistently rated their own understanding of their child's speech as higher than their rating of strangers' understanding, though this gap narrowed as children aged.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The data was cross-sectional, meaning it compared different children at different ages rather than tracking the same children over time, which limits how confidently we can describe individual growth patterns. The sample was drawn from the Upper Midwest of the United States and was relatively homogeneous in race, ethnicity, and socioeconomic status, so these norms may not apply to children from other regions or backgrounds. The study did not compare ICS parent ratings with objective measures of speech intelligibility (like transcription), so it is unclear how well parent perception aligns with actual acoustic intelligibility.
Declared interests
The study was funded by the National Institute on Deafness and Other Communication Disorders (Grant R01DC05104 and R01DC010814). No other conflicts of interest were reported.
The easy way to misread this
Do not interpret the lack of scores below 3 in this normative sample as evidence that young children are always intelligible to strangers. The ICS relies on parent perception, which is often more generous than objective transcription measures. A score of 3 in a 3-year-old is within the lower range of typical development, whereas a score of 3 in a 7-year-old is a significant red flag.