Dissociation between exact and approximate addition in developmental dyslexia.
Kids with dyslexia can estimate fine but stall on exact mental addition—so teach facts with minimal language load.
01Research in Context
What this study did
Yang et al. (2016) compared exact and approximate addition in kids with dyslexia.
They gave both groups short mental-addition problems. Some needed the exact sum. Others only needed a quick estimate.
The study used a quasi-experimental design. All children were matched for age and IQ.
What they found
Kids with dyslexia scored far lower on exact addition. Their approximate answers were just as good as peers.
The gap stayed even when the sums were small. This shows a clear split between precise and ball-park number skills.
How this fits with other research
Belacchi et al. (2014) saw the same split in Down syndrome. Exact math lagged, but estimation stayed intact.
Wang et al. (2012) looked at inhibition. Dyslexic kids struggled most with word tasks, not number tasks. Together these papers hint that the exact-addition weakness is tied to language systems, not to number sense.
Foti et al. (2015) meta-analysis backs this up. Reading disabilities drag down many school skills, but the hit to exact math is especially large.
Why it matters
When you test a learner with dyslexia, check both exact and approximate skills. If estimation is solid, teach exact facts through language-light methods: dot arrays, number lines, or fact-family songs. Skip long word problems until the exact facts are fluent.
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02At a glance
03Original abstract
Previous research has suggested that number sense and language are involved in number representation and calculation, in which number sense supports approximate arithmetic, and language permits exact enumeration and calculation. Meanwhile, individuals with dyslexia have a core deficit in phonological processing. Based on these findings, we thus hypothesized that children with dyslexia may exhibit exact calculation impairment while doing mental arithmetic. The reaction time and accuracy while doing exact and approximate addition with symbolic Arabic digits and non-symbolic visual arrays of dots were compared between typically developing children and children with dyslexia. Reaction time analyses did not reveal any differences across two groups of children, the accuracies, interestingly, revealed a distinction of approximation and exact addition across two groups of children. Specifically, two groups of children had no differences in approximation. Children with dyslexia, however, had significantly lower accuracy in exact addition in both symbolic and non-symbolic tasks than that of typically developing children. Moreover, linguistic performances were selectively associated with exact calculation across individuals. These results suggested that children with dyslexia have a mental arithmetic deficit specifically in the realm of exact calculation, while their approximation ability is relatively intact.
Research in developmental disabilities, 2016 · doi:10.1016/j.ridd.2016.05.018