Profiles of vocalization change in children with autism receiving early intervention.
Vocal growth in early autism intervention is jagged, not linear—track the speech-to-nonspeech ratio often and expect dips.
01Research in Context
What this study did
Trembath et al. (2019) tracked how vocal sounds changed in preschoolers with autism during a full early-intervention program. They recorded every sound the kids made for ten months and labeled each one as speech or nonspeech.
The team wanted to see if the ratio of real words to babbles, cries, or squeaks would climb in a straight line as therapy went on.
What they found
The ratio did not rise steadily. It went up, down, and flat across months, even though the kids were in the same high-quality program.
Children who entered with stronger language or thinking scores showed the biggest final jump in their speech-to-nonspeech ratio.
How this fits with other research
Schertz et al. (2016) pooled many early-ABA trials and found small but steady language gains. David’s wobbly line seems to clash, yet the meta-average hides the same ups and downs seen when you graph each child every month.
Abdi et al. (2023) got huge vocabulary leaps in minimally verbal kids after only sixteen sessions. Their short burst of change makes David’s long, bumpy ride look slow, but both agree: kids who start with more skills profit most.
Shams et al. (2025) ran an eight-week oral-language block and saw clear expressive growth. The quick win fits inside David’s longer story—early spikes can happen, yet the full ratio may still wobble for months.
Why it matters
Stop waiting for a smooth upward curve. Plot speech-to-nonspeech ratios at least every four weeks; celebrate jumps, but don’t panic over dips. Use the baseline language score to set realistic end-points, and keep parents in the loop so they see progress even when the graph zig-zags.
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02At a glance
03Original abstract
Children with autism spectrum disorder (ASD) commonly present with comorbid language impairment, negatively impacting their learning and participation across settings. Addressing these needs requires a detailed understanding of their communication trajectories. In this study, we used the language environment and analysis (LENA) system to examine possible changes in children's (a) vocalizations and (b) ratio of speech to nonspeech vocalizations over a 10-month period. Data for 23 children with ASD (17M, 6F; ages 32-67 months) were analyzed, including monthly 3-hr in-class recordings and standardized measures of language, cognition, and ASD characteristics. Using hierarchical generalized linear models, we found significant time-trends for child vocalizations (P ≤ 0.001) and the vocalization ratio (P = 0.02), reflecting a waxing and waning pattern. Children with higher expressive language scores (Mullen scales of early learning, Vineland adaptive behavior scales - 2nd Ed.) and nonverbal cognition (Mullen scales of early learning), and fewer ASD characteristics (social communication questionnaire) demonstrated greater increases in the vocalization ratio over time (P values 0.04-0.01). Children with greater language and cognition difficulties were the most vocal, but produced a higher proportion of nonspeech vocalizations. The results demonstrate that significant fluctuations, as opposed to linear increases, may be observed in children with ASD receiving intervention, highlighting the value of assessment at multiple time-points. In addition, the findings highlight the need to consider both the quantity (vocalization counts) and quality (ratio of speech to nonspeech vocalizations) when interpreting LENA data, with the latter appearing to provide a more robust measure of communication. Autism Research 2019, 12: 830-842. © 2019 International Society for Autism Research, Wiley Periodicals, Inc. LAY ABSTRACT: In this study, we examined possible changes in speech and nonspeech vocalizations in 23 children with autism attending a comprehensive early intervention program over a 10-month period. Contrary to our expectation, we observed a waxing and waning pattern of change in children's vocalizations over time, rather than a steady increase. We also found evidence to suggest that looking at the quality of children's vocalizations (i.e., the ratio of speech to nonspeech vocalizations) provides a more accurate picture of children's development than simply looking at the quantity (i.e., how frequently they vocalize).
Autism research : official journal of the International Society for Autism Research, 2019 · doi:10.1002/aur.2075