Instability of delay classification and determination of early intervention eligibility in the first two years of life.
Bayley-III scores swing so much under age two that one test is not enough to lock in early-intervention eligibility.
01Research in Context
What this study did
Laugeson et al. (2014) watched Bayley-III scores in babies under two years. They wanted to see if the label 'developmental delay' stayed the same over time.
The team gave the Bayley-III more than once to the same infants. They tracked who got flagged for early-intervention services at each age.
What they found
The delay label jumped around. Many babies scored 'delayed' one month and 'typical' the next.
Because the scores swung so much, the test missed kids who really needed help and flagged kids who did not. The Bayley-III alone was too shaky for big decisions before age two.
How this fits with other research
Capio et al. (2013) saw the same dance in preterm toddlers. About 15 percent switched delay status between 8 and 20 months, a direct match to A et al.'s warning.
Kuang et al. (2025) flipped the problem sideways. They used the same shaky Bayley-III numbers in a computer model. The model could spot very preterm infants at low ASD risk with 93 percent certainty, showing that patterns, not single scores, hold value.
Velikos et al. (2015) add a snapshot view: at just one time point, preterm infants already score low. Taken together, the papers agree the Bayley-III is sensitive to medical risk, but single-point labels are unreliable.
Why it matters
If you screen an infant once and write 'eligible' or 'not eligible' based only on the Bayley-III, be ready to re-test. Use the first score as a yellow flag, not a stop sign. Pair it with parent input, medical history, and later re-checks. Document that delay status can flip until at least 24 months so teams do not freeze services too early or deny them too late.
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02At a glance
03Original abstract
The purpose of this study was to determine the effectiveness of the Bayley Scales of Infant Development, Third Edition (Bayley-III) to track development and classify delays in low- and high-risk infants across the first two years of life. We assessed cognitive, language, and motor development in 24 low-risk full-term and 30 high-risk preterm infants via seven assessments performed between 3 and 24 months corrected age. The Bayley-III resulted in highly unstable delay classifications, low sensitivities, and poor positive predictive values across time. The results highlight that early intervention professionals, researchers, and policy makers should: (1) emphasize clinical opinion and prevalence of risk factors rather than standardized assessment findings when classifying delays and determining eligibility for services, and (2) develop more effective developmental assessments for infants and young children.
Research in developmental disabilities, 2014 · doi:10.1080/09362830701796784