O’Hare et al. explore the nature, development, and neurological basis of developmental dyscalculia (DD) in children.
Compared to the well-studied domain of dyslexia, DD remains poorly understood and under-researched. Its diagnosis is challenging due to wide variability in children’s mathematical ability, unclear developmental trajectories of mathematical skills, and a lack of clear diagnostic criteria.
The authors outline a framework for evaluating children’s mathematical development:
- Counting: True number understanding begins with active object counting, not just rote recitation.
- Quantity (number concept): The grasp of numerical quantity develops more slowly than verbal number sequences.
- Number and symbol recognition: Learning to connect quantity with number symbols is crucial and typically begins around age 4–5.
- Calculation: If a child can perform basic number operations at age level but performs poorly on standardized arithmetic tests without intellectual or educational explanation, DD may be present.
The article discusses two broad types of DD observed in children, linked to different brain hemisphere dysfunctions:
- Left hemisphere dysfunction (lexical-syntactical dyscalculia): Children with this profile struggle with recognizing and writing number symbols and operator signs, sequencing digits, and manipulating multi-digit numbers. They often have comorbid dyslexia, dysgraphia, and right-left disorientation, resembling developmental Gerstmann syndrome. Their understanding of numerical quantity is relatively intact, but symbol manipulation and arithmetic operations are impaired.
. - Right hemisphere dysfunction (spatial-quantitative dyscalculia): These children understand numeric symbols but lack an internal concept of numerical quantity. They rely on concrete objects for basic calculations and often exhibit constructional dyspraxia, visual-spatial difficulties, and left-side motor issues. Their literacy is typically intact, but math-related learning is severely impaired. This form may reflect organic brain dysfunction and is associated with a poorer prognosis.
The article also highlights parallels with acquired dyscalculia in adults, where damage to specific brain regions causes distinct patterns of numerical impairment. For instance, parietal lobe damage can result in number alexia or anarthmetria.
The authors conclude that pure DD is rare in children of normal intelligence and is often accompanied by other neurodevelopmental or neurological conditions. Accurate diagnosis requires multidisciplinary assessment. Tailored interventions, such as symbol-based software for left-hemisphere cases or verbal support tools for right-hemisphere cases, may help bypass deficits and support learning.
