The robustness of speech-like vocalization in typically developing infants and infants with autism.
D Kimbrough Oller, Edina R Bene, Hyunjoo Yoo and 7 others
PMID 40088705WHAT IT FOUND
Infants with autism or developmental disabilities produced speech-like sounds at the same high rates as typically developing infants during the first year.
Volubility did not predict later language or cognitive outcomes, so low sound production is not a reliable early marker for these groups.
Key findings
01Volubility rates were high and statistically similar across typically developing, autism, and developmental disability groups throughout the first year.
02The overall rate of speech-like vocalizations in the first year did not significantly predict autism severity or language and cognitive scores at 24 or 36 months.
03While the average rate did not differ by diagnosis, the trajectory of vocalization declined significantly in the autism and developmental disability groups over the year, unlike the stable pattern in typically developing infants.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The DD group was small (n=21), with missing data for 9 infants at the earliest and latest time points, which may affect the reliability of the trajectory findings for this group. SES was measured only by maternal education years, which may not fully capture socioeconomic complexity, and the sample had a higher median education level (18 years) than prior studies that found SES effects. The study focused on English-speaking families in a metropolitan area, limiting generalizability to other linguistic or cultural contexts. Volubility was measured as a raw count of protophones, which the authors acknowledge may be a weak measure because it includes sounds expressing discomfort as well as well-being.
Declared interests
The study was federally funded. The authors declared no conflicts of interest.
The easy way to misread this
Do not interpret the lack of difference in average volubility between groups as evidence that vocal development is identical in all infants. The study found that while the starting rate was similar, the trajectory differed, with ASD and DD infants showing significant declines over the first year that TD infants did not.