Performance of young people with Down syndrome on the Leiter-R and British picture vocabulary scales.
In Down syndrome, verbal mental-age scores run higher than non-verbal ones—so name your test when you match mental age.
01Research in Context
What this study did
The team gave two quick tests to 46 young adults with Down syndrome. One test, the BPVS-II, asks kids to point to a picture that matches a spoken word. The other, the Leiter-R, uses colored blocks and cards with no talking.
Both tests give a mental-age score. The researchers wanted to see if the scores matched or if one test always came out higher.
What they found
BPVS-II verbal scores were almost always higher than Leiter-R non-verbal scores. The gap was large enough to change how you would match a child to a typical peer.
Still, both tests did a good job of ranking the adults from lower to higher ability. They just used different rulers.
How this fits with other research
Kraijer et al. (2005) showed the PDD-MRS autism screen works fine in the same Down-syndrome group. Together, the papers tell us we can trust brief tools in this population—if we pick the right domain.
Ivancic et al. (1996) used Rasch math to show that adults with ID see facial emotions in a unique way, not just a slower way. Aznar et al. (2005) add that even basic IQ scores can hide the same kind of difference—verbal and non-verbal skills are not simply high vs low.
Peñuelas-Calvo et al. (2019) found that people with ASD lean on non-verbal IQ for social tests, while typical people lean on verbal IQ. The Down-syndrome pattern looks similar: non-verbal scores may better predict real-life tasks, even when verbal scores look stronger.
Why it matters
If you use mental-age matching in research or program placement, write down which test you used. A child with a BPVS-II mental age of 6 may act more like a young learners on Leiter-R tasks. Match teaching materials to the lower score for non-verbal work and to the higher score for language lessons. Always state the test in your report so the next BCBA knows why the numbers look different.
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02At a glance
03Original abstract
BACKGROUND: The British picture vocabulary scales (BPVS-II) and the Leiter international performance scales (Leiter-R), both restandardised in 1997, are often used in experimental studies to match individuals with intellectual impairment. Both provide a brief measure of mental age, and cover a wide ability range using a simple format. The BPVS-II assesses verbal comprehension and the Leiter nonverbal abilities. The issue is which to choose. People with Down syndrome (DS), for example, have particular problems in language and so the BPVS may provide an underestimation of ability. METHOD: The present study investigated this by comparing the performance of 46 young people with DS (21 females, 25 males, mean age 19 years 10 months) on the BPVS-II (verbal mental age - VMA) and the Leiter-R brief IQ (nonverbal mental age - NVMA). RESULTS: Contrary to expectations VMAs were significantly higher than NVMAs (6 years 6 months and 5 years 2 months, respectively). There was a significant correlation of 0.61 between the VMA and NVMA, and both discriminated participants at all levels of ability. However, the Leiter-R brief IQ scores provided poor discrimination at the bottom end of the IQ range (IQ 36). CONCLUSION: Both the BPVS-II and the Leiter-R provide mental age equivalent scores that are useful for plotting developmental progress, although absolute mental ages may differ.
Journal of intellectual disability research : JIDR, 2005 · doi:10.1111/j.1365-2788.2005.00643.x