Trajectories of cognitive development in toddlers with language delays.
Toddlers whose words stay flat and nonverbal scores also lag are four times more likely to receive an ASD diagnosis by preschool.
01Research in Context
What this study did
Seiverling et al. (2018) watched 350 late-talking toddlers every 6 months until age 4. They split the kids into hidden groups based on how their verbal and nonverbal scores moved over time.
All children started with language delays. The team wanted to see which paths led to an autism label and which did not.
What they found
Four clear paths showed up. One group stayed low in both talking and thinking. Another group stayed low in talking but grew in puzzles and blocks.
The low-talking/low-thinking path carried a 4-to-1 chance of later ASD. Kids who caught up in words usually landed in simple delay, not autism.
How this fits with other research
Van Hanegem et al. (2014) mapped autism severity paths in the same age range. Both studies used hidden-group math, giving us a matched pair of severity and cognitive maps.
Reichard et al. (2019) followed autistic children to age 8. They saw the word gap stay flat but not widen, matching Laura's finding that slow growth, not loss, is the signal.
Kuang et al. (2025) took the idea to preterm babies. Their model flagged low-risk infants with a large share accuracy, showing the same trajectory tool works even before toddlerhood.
Why it matters
If you test a late talker today, chart both word and nonverbal scores over two or three visits. A flat word line plus low nonverbal scores should move ASD screening up your list. A child who climbs in puzzles while words lag may still need help, but the label could be broader delay. Track, don't snapshot.
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02At a glance
03Original abstract
BACKGROUND: Toddlers with early language delays (LD) are at risk for developmental difficulties, including autism spectrum disorder (ASD). However, little is known about early cognitive skill acquisition in this population. AIMS: To explore heterogeneity in cognitive development in toddlers with significant LD (n = 30) or typical development (n = 61), and how this relates to 36-month outcomes (ASD, non-ASD delays, or no delays). METHODS: Growth mixture modeling of nonverbal and verbal mental age (NVMA, VMA) scores from the Mullen Scales of Early Learning was conducted with data from 18, 24 and 36 months. RESULTS: A two-class NVMA solution was selected (Age Appropriate, 82%, Delayed, 18%); class membership was related to the no delay outcome, and although the proportion of toddlers with ASD in the Age-Expected class was 17% compared to 50% of toddlers with non-ASD delays, this difference was not statistically significant. The best-fitting model for VMA included three classes: Age Appropriate (66%), Delay Catch-Up (23%), Delayed (11%); class assignment differed by outcome. Children in the Delay Catch-Up class were more likely to have non-ASD delays compared to ASD, while the reverse was true in the Delayed class. CONCLUSIONS: Cognitive development in toddlers with LD is heterogeneous, and delayed verbal trajectories relate to later ASD diagnosis.
Research in developmental disabilities, 2018 · doi:10.1016/j.ridd.2018.04.005