Number-processing skills in adults with dyslexia.

Area of Science:

• Cognitive psychology
• Neurodevelopmental disorders
• Educational psychology

Background:

• Developmental dyslexia is a neurodevelopmental disorder primarily affecting reading.
• Understanding numerical cognition in dyslexia is crucial for targeted interventions.
• Previous research presents mixed findings on numerical abilities in individuals with dyslexia.

Purpose of the Study:

• To investigate basic numerical skills and arithmetic abilities in adults with developmental dyslexia.
• To differentiate between intact basic number processing and specific arithmetic deficits.
• To explore the role of verbal coding versus nonverbal magnitude representation in numerical difficulties.

Main Methods:

• Participants with and without dyslexia performed exact and approximate calculations.
• Basic numerical tasks included counting, symbolic number comparison, and the spatial-numerical association of response codes (SNARC).
• Visuospatial tasks (mental rotation, visual search) were included to assess non-numerical cognitive functions.

Main Results:

• Adults with dyslexia showed marginal impairment in counting and significant slowness in exact addition and multiplication.
• No significant differences were found in basic number processing tasks like symbolic number comparison or approximate addition.
• Performance on subtraction and approximate addition tasks was similar between groups.

Conclusions:

• Basic number processing appears intact in adults with developmental dyslexia.
• Difficulties in arithmetic are primarily linked to the verbal coding system, not deficits in nonverbal magnitude representation or spatial cognition.
• Findings suggest a specific impact of dyslexia on the verbal aspects of numerical processing and arithmetic.