Understanding Number Line Estimation in Williams Syndrome and Down Syndrome.
V Simms, A Karmiloff-Smith, E Ranzato and 1 others
PMID 31705420WHAT IT FOUND
When compared at the same mental age, people with Williams syndrome, Down syndrome and typical development placed numbers on lines with similar accuracy.
Williams scores tracked number familiarity, while Down scores tracked visuo-spatial skills on the 0-10 scale.
Key findings
01There was no significant group difference in number line estimation accuracy or linearity on the 0-10 or 0-100 scale, and Bayesian analysis supported the null.
02Number line estimation performance was significantly associated with mathematical achievement in all groups.
03In Williams syndrome, number familiarity predicted number line errors on both scales; in Down syndrome, visuo-spatial skills predicted errors on the 0-10 scale.
STILL TO COME
How it was doneWhat they foundWhat it means for OTsWhat it means for SLPs
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What it does not show
The typically developing group was significantly younger than the Williams and Down syndrome groups (mean age 74.0 months, 244.7 months and 258.4 months), even though they were matched on mental age or IQ. Some analyses included fewer participants than the recruited groups, and one participant was excluded from 0-100 analyses after answering only three of 13 items. The study assessed participants in one testing session and did not record the strategies they used on the number line task, so it cannot explain how similar scores were reached. Bayesian evidence for the null group difference was only anecdotal to moderate. The Williams and Down syndrome groups had wide age ranges, from 8;00 to 52;25 years and 8;06 to 49;17 years, so the findings may not apply to all ages.
The easy way to misread this
Do not conclude that a similar number line score means the same underlying skill in Williams syndrome and Down syndrome. The groups had similar errors, but number familiarity predicted errors in Williams syndrome, while visuo-spatial skills predicted errors on the 0-10 scale in Down syndrome.