Mental additions and verbal-domain interference in children with developmental dyscalculia.

Peters et al. (2013) watched kids with developmental dyscalculia do mental addition. Half the problems were written flat across the page. Half were stacked up-and-down.

The team added a verbal twist. While the child solved each problem, they also had to repeat nonsense words. This extra talking job tested how much the brain juggles words and numbers at once.

Kids with dyscalculia got more wrong answers when the problem lay flat. The side-by-side look ate up their verbal working memory. Turning the same problem upright helped accuracy, even when they still had to chatter nonsense words.

The damage was the same whether or not the child also had dyslexia. The layout, not the reading trouble, drove the drop.

Jou et al. (2023) seems to say the opposite. They gave kids with dyslexia reading pages that also ran across the page. Adding a small picture doubled how many kids finished the passage. Flat layout hurt math here, but helped reading there.

The clash melts away when you look at the task. Math needs the brain to hold and move digits inside the head. Reading only needs the eyes to sweep left-to-right. A sideways page overloads the math workspace, yet gives the reading eyes a clear track.

Kaltner et al. (2014) backs the idea that kids with developmental disorders have tight brain space. They saw dyslexic children slow down when they had to mentally flip letters. Extra visual demand, extra time—same pattern C et al. found with numbers.

If you teach math to a child with dyscalculia, turn the worksheet vertical before you hand it over. One quick flip spares working memory for the actual math, not for holding the row of digits in place. You can keep the word problems or stories horizontal—reading is fine that way. Start Monday: print two versions of the next practice sheet and watch which one the child finishes faster.