Dyscalculia - Part 2: Core deficit of the Number Module

The number module refers to our innate ability of processing numerical information.

By 김예경 Yekyung Kim, BSc.

There are various causal factors in the development of dyscalculia, one of which is the deficiency of the number module. The number module refers to our innate ability of processing numerical information. When there is a core deficit in the number module, individuals develop dyscalculic traits. 

Dyscalculic individuals struggle with basic numerical operations. For instance, they struggle to understand that 4 is composed of four 1s or that addition and subtraction are inverse operations (e.g., 5 + 3 = 8, thus, 8 – 5 = 3). Such deficiency in processing numerical information could develop into everyday life difficulties.


For example, Samantha Abeel who reported having dyscalculia, said that she could not tell what time it was, calculate money in restaurants or supermarkets, nor understand distances. This made her feel anxious, resulting in sleeping problems.


Thus, it is important for us to acknowledge that dyscalculia is a grave problem that needs to be addressed and researched further in order to support those in need of support. 

How do we know who has a core deficit in the number module? There are several ways for assessing the capacity of the number module, such as dot enumeration. During the dot enumeration task, participants are asked to count how many dots there are on the screen and their speed and accuracy are measured. 


Reeve et al. (2012) conducted a longitudinal study in Australia using dot enumeration, and found that children could be put into three groups depending on their performance. Children in the Slow group were only able to subitize up to two items, the Medium group were able to subitize three, and finally the Fast group could subitize up to four. Furthermore, the performance in dot enumeration predicted the arithmetic operations, such as subtraction and multiplication. The study suggests that dot enumeration allows early assessment of core deficit in the number module and the development of dyscalculia.  


How common is dyscalculia? Studies suggest that the prevalence rates of dyscalculia are around 3.5% to 7% of the population, due to the core deficit in the number module. In conclusion, dysfunctional number module is sufficient to cause a disability in processing numerical information. Although we have mainly focused on the cognitive basis of dyscalculia, other factors interact with the number module during the development of the disorder. For instance, what brain areas are responsible for the number module? Is dyscalculia heritable? We will answer these questions in the next articles.  



Butterworth, B., (2018). Core Deficit of Dyscalculia. Science of Dyscalculia. 1st ed. Routledge. https://doi.org/10.4324/9781315538112