With respect to pure developmental dyscalculia, domain-general causes are unlikely as they should not impair ones ability in the numerical domain without also affecting other domains such as reading.Two competing domain-specific hypotheses about the causes of developmental dyscalculia have been proposed – the magnitude representation (or number module deficit hypothesis) and the access deficit hypothesis. Magnitude representation deficit
Dehaenes "number sense" theory suggests that approximate numerosities are automatically ordered in an ascending manner on a mental number line. The mechanism to represent and process non-symbolic magnitude (e.g., number of dots) is often known as the "approximate number system" (ANS), and a core deficit in the precision of the ANS, known as the "magnitude representation hypothesis" or "number module deficit hypothesis", has been proposed as an underlying cause of developmental dyscalculia.In particular, the structural features of the ANS is theoretically supported by a phenomenon called the "numerical distance effect", which has been robustly observed in numerical comparison tasks. Typically developing individuals are less accurate and slower in comparing pairs of numbers closer together (e.g., 7 and 8) than further apart (e.g., 2 and 9). A related "numerical ratio effect" (in which the ratio between two numbers varies but the distance is kept constant, e.g., 2 vs. 5 and 4 vs. 7) based on the Webers law has also been used to further support the structure of the ANS.
Dyscalculics may have a difficult time adding numbers in a column format because their mind can mix up the numbers, and it is possible that they may get the same (wrong) answer twice due to their mind processing the problem incorrectly. Dyscalculics can have problems determining differences in different coins and their size or giving the correct amount of change and if numbers are grouped together, it is possible that they cannot determine which has less or more. If a dyscalculic is asked to choose the greater of two numbers, with the lesser number in a larger font than the greater number, they may take the question literally and pick the number with the bigger font. Adults with dyscalculia have a tough time with directions while driving and with controlling their finances, which causes difficulties on a day-to-day basis. College students or other adult learners
College students particularly may have a difficult time due to the fast pace and change in difficulty of the work they are given. As a result of this, students may develop much anxiety and frustration. After dealing with their anxiety for a long time, students can become averse to math and try to avoid it as much as possible, which may result in lower grades in math courses. (That said, students with dyscalculia can also do exceptionally well in writing, reading, and speaking.) Causes
Both domain-general and domain-specific causes have been put forth.