Henik et al. (2011) explore the cognitive and neural mechanisms underlying Developmental Dyscalculia (DD), a congenital learning disability that impairs the ability to acquire basic arithmetic skills.
Affecting approximately 3–6% of the population, DD is often compared in prevalence to dyslexia. Although traditionally viewed as a domain-specific disorder involving numerical processing deficits, the authors argue for a more nuanced perspective, highlighting the disorder’s heterogeneity and the influence of domain-general cognitive processes.
Cognitive and neural markers of dyscalculia
The authors examine key cognitive features of DD, including subitizing (instantly recognizing small quantities), comparative judgment, and the automaticity of number processing. Individuals with DD often have a reduced subitizing range, struggle with numerical comparisons (especially when numbers are close in value), and show weak or delayed automatic number processing, as measured by tasks like the numerical Stroop effect. The numerical Stroop effect is a psychological phenomenon that occurs when people are asked to compare numerical values or physical sizes of digits, and the irrelevant dimension interferes with or facilitates performance.
At the neural level, research consistently points to the intraparietal sulcus (IPS) as a core area involved in numerical processing. Functional imaging studies show abnormal IPS activity in individuals with DD, and structural differences in this region have been observed in both children and adults with the disorder. However, the IPS is also implicated in non-numerical tasks like spatial attention, and many individuals with DD also show deficits in these areas. This overlap challenges the idea of DD as a purely number-specific disorder.
Toward a multi-factorial model of dyscalculia
Further, the article presents evidence of domain-general impairments in attention, executive functioning, and working memory among individuals with DD. These findings suggest that DD may reflect a combination of numerical and broader cognitive deficits, particularly when comorbid with conditions like ADHD. The authors introduce the concept of Mathematical Learning Disability (MLD) to describe cases with multiple cognitive deficits that go beyond number processing.
In conclusion, the authors argue that DD is best understood through a multi-factorial model that accounts for both domain-specific and domain-general contributions. The complexity of DD, including its varied symptoms and comorbidities, calls for personalized assessment and intervention strategies. Recognizing this heterogeneity is crucial for effective diagnosis, treatment, and further research into the neural and cognitive foundations of numerical learning disabilities.
