Mathematical skills in children with dyslexia

• The DD group scored poorly on number fact retrieval, problem solving, calculation.
• The DD group showed adequate conceptual understanding and approximate arithmetic.
• The findings are consistent with the Triple-code model.
• DD children have impaired verbal–phonological number codes.
• DD children have intact magnitude representations and visual-Arabic number codes.

The mathematical performance of 17 children with developmental dyslexia (DD) was assessed and compared to a control group to examine whether difficulties related to reading and phonological processing affect the development of mathematical skills. The DD group performed worse than the controls on number fact retrieval, multi-step arithmetic problem solving, and multi-digit calculation, whereas their scores on tasks tapping approximate arithmetic and conceptual understanding (i.e., place value, calculation principles) were equal to the controls. In view of the Triple-code model, the findings demonstrate that children with DD have problems with tasks depending on verbal–phonological number codes but have no problems with tasks depending on analogue magnitude representations or visual-Arabic number codes.