Delayed development of basic numerical skills in children with developmental dyscalculia.

Area of Science:

• Cognitive psychology
• Developmental psychology
• Neuroscience

Background:

• Children with developmental dyscalculia (DD) exhibit deficits in basic numerical skills.
• Conflicting evidence exists on whether these deficits are qualitatively different or a developmental delay compared to typically developing (TD) children.
• Competing hypotheses include general numerosity representation (Approximate Number System, ANS), object tracking (Object Tracking System, OTS), or symbol access (Access Deficit, AD) impairments.

Purpose of the Study:

• To determine if DD basic numerical skill deficits represent a developmental delay or a qualitative deviation.
• To investigate if these deficits stem from impairments in core cognitive systems (ANS, OTS, AD).

Main Methods:

• Tested 480 children (68 DD, 412 TD) across 2nd, 3rd, and 4th grades.
• Utilized various basic numerical skill paradigms: subitizing, counting, magnitude comparison, number sets, and number line estimation.
• Compared mathematical profiles of 4th-grade DD children with 2nd-grade TD children.

Main Results:

• DD children's basic numerical skill impairments indicated a specific developmental delay, except for dot enumeration.
• Results corroborated when comparing 4th-grade DD children to 2nd-grade TD children, suggesting developmental delay.
• Specific numeracy deficits in DD children supported the ANS deficit hypothesis over AD and OTS.

Conclusions:

• Children with DD experience a developmental delay in basic numerical skills, not a qualitatively distinct deficit.
• The findings support the hypothesis of an Approximate Number System (ANS) deficit as a primary cause of numerical difficulties in DD.
• Interventions should consider addressing the developmental delay and potential ANS impairments in children with dyscalculia.