Forty Children, No Control Group

What the research found

This is a small study, and the authors say so themselves. They call it a pilot. Forty Spanish-speaking children took part, aged between six and eleven. Twenty had a diagnosis of dyslexia, a difficulty that centres on reading. Twenty had a diagnosis of dyscalculia, a difficulty that centres on numbers. There was no third group of typically developing children to serve as a baseline. That single fact shapes everything the study can and cannot say.

The researchers were interested in working memory. This is the mental workspace that holds information for a few seconds while you use it, such as keeping the start of a sentence in mind until you reach the end. They measured it in several ways. One task asked children simply to recall a list of words. Another asked them to hold words in mind and sort them by meaning, for instance picking out the modes of transport from a longer list. A third used verbal analogies, which ask a child to complete patterns such as “hand is to glove as foot is to...”.

On the simplest task, plain recall of a word list, the two groups scored almost the same. The dyslexia group averaged 3.65 words and the dyscalculia group 4.05, a gap that was not statistically meaningful (p = 0.356). In other words, the raw capacity to hold a short list was similar in both.

The differences appeared once the tasks required children to work with meaning, not just store words. On the sorting task, the dyscalculia group averaged 7.00 against the dyslexia group’s 3.35 (p < 0.001). On verbal analogies the gap was wider still: 19.70 for the dyscalculia group against 5.65 for the dyslexia group (F = 18.87, p < 0.001). The pattern in reading comprehension ran the same way. Children with dyslexia scored lower on general reading comprehension, 9.70 against 12.95 (p < 0.01). Interestingly, they did better than the dyscalculia group on texts that carried mathematical content, 4.90 against 2.00.

The authors also report a very strong link, within the dyslexia group, between the meaning-based memory tasks and reading comprehension (r = 0.955, p < 0.01). A correlation that high in a group of twenty children should be read with caution, but it points in a sensible direction: the children who struggled most with holding and manipulating meaning also struggled most with understanding what they read.

What this means for you and your child

The honest headline is modest. This study suggests that dyslexia and dyscalculia are not the same difficulty wearing different labels. Children in the two groups performed differently, and each group had its own areas of relative strength. The child with dyslexia found reading harder but coped better with mathematical text; the child with dyscalculia found number work harder but handled verbal reasoning more easily. That is a useful reminder that a diagnosis describes a profile, not a general level of ability.

It is also worth noticing where the two groups were alike. Basic word-list recall was similar. The gaps opened up only when children had to do something with the words they were holding. If your child has dyslexia, this fits a common picture: the bottleneck is often less about how much can be held in mind and more about processing meaning under load. Reading is a demanding version of exactly that.

Be careful, though, about what a study like this can prove. With forty children and no comparison group of typically developing readers, we cannot say how either group compares with the average child. We cannot say that weak working memory causes poor comprehension. The strong correlation the authors found is consistent with that idea, but it is equally consistent with poor comprehension and weak verbal memory both flowing from a shared underlying difficulty. Correlation, especially in a group this small, is a signpost, not a verdict. A single pilot in one language cannot settle the question.

The practical takeaway is therefore cautious rather than prescriptive. If your child has a diagnosis, it is reasonable to expect their comprehension difficulties to travel with difficulties in holding and reworking language in the moment, and to build support around that: shorter chunks, time to consolidate, and checking understanding rather than assuming it. But these are sensible teaching habits that good practice already recommends. This study gently supports them; it does not, on its own, license strong claims about mechanism or about what will work for any individual child.

We would treat these numbers as a promising early signal that deserves a larger, controlled study. The direction of the findings is plausible and consistent with the wider literature. The evidence here is simply too small, and too preliminary, to carry more weight than that.