Dyscalculia
The term dyscalculia is derived from the Greek words 'dys calculus', meaning bad method for calculations. Dyscalculia symptoms are associated with difficulties with mathematics, problems that have lasted for a long time and don't seem to subside.
Similarly to the term dyslexia, the word dyscalculia refers to severe and persistent problems with learning of certain educational skills. Problems with learning and fluently applying math knowledge, that are not caused by a lack of intelligence or teaching. This definition, like the definition of dyslexia, describes only the problems and provides no explanation about it or the causes of dyscalculia.
In the first years of education, the basic skills of arithmetic are practised intensively with the purpose of automatizing those. A pupil knows that 4 and 5 makes 9 and utilizes that knowledge to do sums like 14 and 5 or 14 and 15. The same goes for simple subtraction, multiplication and division sums. These skills are programmed in the long-term memory and are called up if nescessary without further thought. There is no need for taking extra efforts to do simple sums and parts of calculations. This is useful, because it is the pupil's basis for more complex sums.
Children with dyscalculia are unable to acquire these basic skills and to fluently apply those. They have a limited "suitability for mathematics" compared to their understanding of mathematics and calculations, resulting in various arithmetic problems.
Research
Using an internationally standardized testing method for developmental dyscalculia (NUCALC or Zareki) 112 dyslexic children ranging from 7 to 11 years old were tested. These children were tested on various numerical skills, such as basic arithmetic, counting, reading and writing numbers, comparing and determining numbers.With the standards, provided by the NUCALC-test, an overlap between dyslexia and dyscalculia of 31% was shown. Dyslexic children that have problems with numerical skills were compared to dyslexic children that don't have these numerical problems. The results were compared to the results of other studies.
Unfortunately, dyscalculia is barely treatable, there are close to no ways of treatment.