Developmental Trajectories of Developmental Disorders: Early Diagnosis for an Early Intervention.
Preschool IQ gives only a shaky preview of later ability—plan to re-test and to teach adaptive skills either way.
01Research in Context
What this study did
Sperandini et al. (2026) followed a group of Taiwanese preschoolers who had autism, intellectual disability, or general developmental delay.
They gave the kids IQ tests when they were about three to five years old and again when they reached early elementary age.
The team wanted to see how steady the scores stayed and what might predict any big moves.
What they found
IQ scores were only moderately stable; the correlation between the two time points was 0.73.
Most children stayed in the same range, but a noticeable minority jumped or dropped enough to change IQ labels.
Boys and children who started with higher IQs were the most likely to keep their early rank.
How this fits with other research
Austin et al. (2015) saw the same design in an earlier ASD-only cohort and found even larger IQ gains—9 to 18 points—yet one quarter still met intellectual disability criteria at school entry.
Pathak et al. (2019) widens the lens, showing that higher-IQ and older children with autism often have bigger gaps between IQ and daily-living skills, reminding us that a stable IQ does not promise strong adaptive gains.
Deserno et al. (2017) push the timeline into adulthood and report that the IQ-adaptive gap can keep growing, especially when anxiety or depression is present.
Together these papers form a chain: early IQ shifts, later adaptive shortfalls, and possible adult discrepancies.
Why it matters
For BCBAs, the message is clear: treat early IQ as a rough draft, not a final label.
Keep reassessing both cognition and adaptive skills each year, watch for big jumps or drops, and plan interventions that target daily living even when IQ looks strong.
If you see a sudden slide, screen for emotional comorbidities and adjust goals fast.
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02At a glance
03Original abstract
As part of an ongoing clinical service program for children with developmental delay in an Asian developing country, we analyzed the cognitive attributes of 362 Taiwanese children (average age 48.5+/-12.9 month-old) with uneven/delayed cognitive development as they were assessed repeatedly with average duration of 39.7+/-22.6 months from preschool through early childhood. The objectives were to determine the stability and related factors in cognitive scores of these 362 children belonging to three diagnostic subgroups: 181 children with non-autistic mental retardation (MR), 95 children with autism spectrum disorder (ASD) and 64 children with mixed type developmental language disorder (DLD); and to contribute to the accumulation of data on cognitive outcome in preschool children with developmental delay. Analysis revealed that mean initial cognitive score (IQ1) was 64.9+/-16.9 while mean cognitive measure at follow-up (IQ2) was 72.2+/-19.7. Whole group analysis showed the correlation between IQ1 and IQ2 was moderate (r=0.73, p<0.001). Analysis by a general linear model showed only male gender (beta=4.95, p=0.02, C.I.=0.8-9.1) and IQ1 (beta=0.79, p<0.001, C.I.=0.68-0.90) to be significant predictors of IQ2. There were differences among three groups in IQ1 (p<0.001), IQ2 (p<0.001) and IQ change (p<0.001). Correlation coefficients of IQ1 and IQ2 were 0.6 for ASD group, 0.7 for MR group and 0.4 for DLD group respectively. The greatest proportion of children remained within the same cognitive range for both assessment points, however, it is noted that a substantial minority of children changed IQ ranges drastically from preschool through early childhood. Our results suggest that measurements of cognitive function at preschool age for children with developmental delay were valid in the context of a developing country, and the observed change in cognitive scores during follow-up emphasized the need to interpret the initial results of cognitive tests with caution.
Journal of autism and developmental disorders, 2026 · doi:10.1016/j.ridd.2010.02.011