Early Predictors of Later Expressive Language in Boys With Fragile X Syndrome.
Heather Fielding-Gebhardt, Steven F Warren
PMID 30715922WHAT IT FOUND
Early consonant diversity predicted later vocabulary size in boys with Fragile X Syndrome, but this link depended heavily on autism symptom severity.
Boys with high autism symptoms and low early consonant counts had the smallest later vocabularies, while high consonant counts buffered this effect.
Key findings
01The interaction between early consonant inventory and concurrent autism symptom severity significantly predicted later number of different words, with consonant inventory having a small effect size and autism symptom severity having a large effect size.
02Boys with above-average early consonant inventories produced a larger number of different words regardless of their autism symptom severity level, suggesting a buffering effect.
03Intentional communication and nonverbal IQ at Time 1 were not significant predictors of later expressive language ability in the final model.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The sample size was small (36 boys), which limits statistical power. Expressive language was measured only by number of different words in a 15-minute structured interaction, which may not reflect broader language ability. Autism symptom severity was measured at Time 2 (concurrent with outcome), not Time 1, so the study could not determine if early autism severity interacted with early consonant inventory. The study included boys who were nonverbal at Time 2, which increases heterogeneity but may affect the interpretation of predictive models. Videotaped interactions may have influenced child talkativeness due to social anxiety.
Declared interests
Research supported by the National Institute of Health (Extramural). No other conflicts of interest were declared.
The easy way to misread this
Do not interpret this study as evidence that increasing consonant inventory will definitively improve later vocabulary. The study is observational and cannot prove causation, and the effect of consonant inventory was small compared to the large effect of autism symptom severity.