Typical Errors Made by Children and Adolescents with Developmental Dyscalculia

Background: Poor numeracy and numerical learning problems are very common in our society and present serious obstacles in daily live, school or professional success. Accordingly, the goal of this study was to identify typical error patterns and problem solving strategies in children and adolescents with developmental dyscalculia (DD). Methods: We have examined 86 participants; half had a diagnosed DD (mean 15.5 years) and were compared to typically developing peers (mean 13.9 years). Numerical skills were tested by the standardized test battery BASIS-MATH 4–8. In addition, intelligence, alertness, spatial working memory, and math anxiety were assessed. Results: Results showed that subtractions, completion, and division are particularly challenging for DD. This applied notably to basic operations with large numbers, crossing tens/hundreds, but also simpler calculation problems. Item analyses revealed 10 calculation problems that differentiated best between groups. Moreover, DD used efficient calculation strategies to a lower extent. Discussion: In summary, basic numerical skills in DD, including those of lower difficulty levels, are clearly limited and even adolescents fail in such tasks. Moreover, we were able to identify 10 numerical tasks that would be particularly meaningful to implement in a DD-screener. Finally, our findings highlight the importance of considering individual problem-solving strategies when evaluating people with DD in a clinical, therapeutic or school setting.