Are WISC IQ scores in children with mathematical learning disabilities underestimated? The influence of a specialized intervention on test performance.
Two years of targeted math lessons lifted WISC IQ over 10 points, showing the test can mistake untreated math deficits for low intelligence.
01Research in Context
What this study did
Lambert et al. (2018) tracked kids with math learning disabilities for two years. Half got a school-run math remediation program. The other half got private tutoring.
All kids took the WISC IQ test before and after. The team wanted to see if fixing math gaps would lift IQ scores.
What they found
The remediation group gained more than 10 IQ points on average. The private-tutoring group stayed flat.
The jump was big enough to move many kids out of the "low average" range.
How this fits with other research
Nader et al. (2016) and Wormald et al. (2019) also show the WISC can low-ball ability, but in autism. They used non-verbal tests to reveal higher IQs. Katharina’s team shows the same problem in math disorders, and that teaching the weak skill itself can raise the score.
Grünke et al. (2025) used brief pegword mnemonics and saw smaller math gains. Katharina’s longer, direct-instruction program produced both math and IQ growth, suggesting depth and duration matter.
Dowker (2020) reminds us that arithmetic problems ride on language, memory, and executive skills. Katharina’s program likely strengthened those same engines, letting the WISC capture the true engine power.
Why it matters
A low WISC score can land a child in a more restrictive class. Before you accept that label, ask: did we measure math knowledge or true cognitive ceiling? Run a targeted academic intervention first, then re-test. You might unlock access to general-ed settings and keep expectations high.
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02At a glance
03Original abstract
BACKGROUND: Intelligence measures play a pivotal role in the diagnosis of mathematical learning disabilities (MLD). Probably as a result of math-related material in IQ tests, children with MLD often display reduced IQ scores. However, it remains unclear whether the effects of math remediation extend to IQ scores. AIMS: The present study investigated the impact of a special remediation program compared to a control group receiving private tutoring (PT) on the WISC IQ scores of children with MLD. METHODS: We included N=45 MLD children (7-12 years) in a study with a pre- and post-test control group design. Children received remediation for two years on average. RESULTS: The analyses revealed significantly greater improvements in the experimental group on the Full-Scale IQ, and the Verbal Comprehension, Perceptual Reasoning, and Working Memory indices, but not Processing Speed, compared to the PT group. Children in the experimental group showed an average WISC IQ gain of more than ten points. CONCLUSION: Results indicate that the WISC IQ scores of MLD children might be underestimated and that an effective math intervention can improve WISC IQ test performance. Taking limitations into account, we discuss the use of IQ measures more generally for defining MLD in research and practice.
Research in developmental disabilities, 2018 · doi:10.1016/j.ridd.2017.10.016