Developmental Dyscalculia (DD) is characterised by impairments in learning basic arithmetic facts, processing numerical magnitude and performing accurate and fluent calculations. These difficulties are quantifiably below what is expected for an individual’s chronological age, and are not caused by poor educational or daily activities or by intellectual impairments.
Dyscalculia often occurs in association with other developmental disorders such as dyslexia or ADHD/ADD. Co-occurrence is generally assumed to be a consequence of risk factors that are shared between disorders, for example, working memory. However, it should not be assumed that all dyslexics have problems with mathematics, although the percentage may be very high, or that all dyscalculics have problems with reading and writing. This latter rate of co-occurrence may well be a much lower percentage.