Difference or delay? A comparison of Bayley-III Cognition item scores of young children with and without developmental disabilities.
Guttman errors on the Bayley-III can flag kids whose thinking path differs from the test order, not just kids who are slow.
01Research in Context
What this study did
Visser et al. (2017) looked at how toddlers with developmental delay answer Bayley-III Cognition items. They compared each item response to kids without delays.
The team counted Guttman errors. A Guttman error happens when a child misses an easy item but passes a harder one. Lots of these errors can signal a test problem or a different learning path.
What they found
Kids with severe delays showed more Guttman errors. The errors were not random; they clustered at the low end of the scale.
The pattern looked like a true difference in thinking style, not just a slower version of typical growth.
How this fits with other research
Eussen et al. (2016) also used the Bayley-III in toddlers, but they asked a different question. They showed that low scores before 3.5 years predict later language and cognition in autism. Linda’s work adds: when the score looks odd, dig into the item errors; they may tell you why the number is low.
Morrison et al. (2017) compared parent report to direct testing in the same age group. They found parents and testers mostly agreed. Linda’s study reminds us that even during direct testing, the item order can mislead if the child’s development is qualitatively different.
La Valle et al. (2025) showed strong agreement between Vineland-3 and Mullen scores in Down syndrome. Linda’s paper widens the lens: agreement can look fine at the total-score level while still hiding item-level quirks in other delays.
Why it matters
If you give the Bayley-III and the cognition score feels off, run the Guttman error printout. A pile of easy misses means the child may need tasks taught in a different order, not just more time. Shift your teaching sequence to match the child’s true skill profile instead of the test’s stair-step order.
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02At a glance
03Original abstract
The "difference or delay paradigm" focuses on the question of whether children with developmental disabilities (DD) develop in a way that is only delayed, compared to typically developing children, or also qualitatively different. The current study aimed to examine whether qualitative differences exist in cognitive development of young children with and without DD on the basis of item scores on the Dutch Bayley-III Cognition scale. Differential item functioning was identified for 15 of the 91 items. The presence of DD was related to a higher number of Guttman errors, hinting at more deviation in the order of skill development. An interaction between group (i.e., with or without DD) and developmental quotient appeared to predict the number of Guttman errors. DD was related to a higher number of Guttman errors for the whole range of developmental quotients; children with DD with a small developmental quotient had the highest number. Combined, the results mean that qualitative differences in development are not to be excluded, especially in cases of severe developmental disabilities. When using the Bayley-III in daily practice, the possibility needs to be taken into account that the instruments' assumption of a fixed order in skill development does not hold.
Research in developmental disabilities, 2017 · doi:10.1016/j.ridd.2017.09.022