Speech Development Between 30 and 119 Months in Typical Children III: Interaction Between Speaking Rate and Intelligibility.
Tristan J Mahr, Paul J Rathouz, Katherine C Hustad
PMID 39680790WHAT IT FOUND
Faster habitual speech predicted slightly lower intelligibility in young children, but the effect was small.
At age 4, a faster rate by 0.5 syllables per second lowered intelligibility by 3 to 5 percentage points. By age 6, this difference dropped to 1 to 2 percentage points.
Key findings
01After adjusting for age, children with faster habitual speaking rates had lower expected intelligibility than peers of the same age, particularly in longer utterances.
02For 4-year-olds, an increase in speaking rate of 0.5 syllables per second predicted a decrease in intelligibility of 3 to 5 percentage points for five- to seven-word utterances.
03The negative effect of speaking rate on intelligibility was negligible for 6-year-olds, with a decrease of only 1 to 2 percentage points for the same rate increase.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study was observational and did not manipulate speaking rate, so it cannot prove that slowing speech causes improved intelligibility. The sample lacked diversity, with 87% White children from middle or upper-middle socioeconomic backgrounds. Speech was elicited in a structured sentence repetition task, which may not reflect natural, spontaneous speech. Pausing behavior was excluded from the speaking rate measure, limiting the understanding of how pauses affect intelligibility.
Declared interests
The authors declared no conflicts of interest. The study was funded by the National Institute on Deafness and Other Communication Disorders and the National Institute of Child Health and Human Development.
The easy way to misread this
Do not conclude that instructing a child to speak more slowly will reliably improve their intelligibility. This study observed habitual rates and found only small associations, and it did not test whether deliberate rate changes produce the predicted effects.