Acoustic properties of early vocalizations in infants with fragile X syndrome.
Lisa R Hamrick, Amanda Seidl, Bridgette L Tonnsen
PMID 31407873WHAT IT FOUND
In infancy, vocalizations from infants with fragile X syndrome did not show group differences in the measured features.
In fragile X only, pitch, duration, complexity, and volubility related to later language and ASD severity.
Key findings
01The fragile X and low-risk control groups did not differ statistically on infant vocalization features.
02Within the fragile X group, wider infant vocalization duration range was associated with higher later receptive and expressive language.
03Within the fragile X group, higher infant pitch was associated with higher later ASD symptom severity.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The sample was small: 22 infants with fragile X syndrome and 17 low-risk controls, and power analyses were set to detect only large effects. The study treated p-values between .05 and .10 as trends because of the small sample size. Canonical syllable use was rare (5 of 22 infants with fragile X and 5 of 17 low-risk controls), which caused floor effects in complexity ratio. The infants were assessed during a brief, standardized AOSI interaction in the home, so the vocalizations may not represent everyday interaction with familiar partners. Home recordings had noise and required a lower reliability threshold; average reliability was 81%, and complexity agreement was 74% for initial reliability and 75% for project files. The fragile X group was slightly older than the low-risk group at 9 and 24 months, and the fragile X group with ASD was slightly older than the fragile X group without ASD at 24 months. The study did not collect home language data or evaluate nuanced effects of sex and multilingualism. Most vocalization features were not associated with categorical ASD diagnosis, and the ASD association was with continuous symptom severity rather than diagnosis.
Declared interests
This work was supported by NIH grant R01MH090194. The supplied text does not include a separate conflict-of-interest declaration.
The easy way to misread this
Do not read these associations as a diagnostic rule for fragile X syndrome. The group comparison was null, the sample was small, and the ASD finding was limited to higher pitch with continuous symptom severity, not categorical diagnosis.