Two Dyscalculia Subtypes With Similar, Low Comorbidity Profiles: A Mixture Model Analysis

Area of Science:

• Developmental Psychology
• Educational Psychology
• Neuroscience

Background:

• Previous research has struggled to establish robust subtypes of dyscalculia using either top-down or bottom-up approaches.
• Identifying distinct subtypes is crucial for understanding the heterogeneity of dyscalculia and tailoring interventions.
• A comprehensive approach considering a wide range of cognitive and mathematical skills is needed.

Purpose of the Study:

• To explore and identify subtypes of dyscalculia using a mixture model analysis.
• To investigate subtypes based on a broad range of variables including intelligence, reading fluency, working memory, attention, and mathematical skills.
• To determine the robustness of identified subtypes across different diagnostic assessments.

Main Methods:

• A mixture model analysis was conducted on a sample of 174 elementary school children with dyscalculia (mathematical abilities: percentile rank <10; IQ > 70).
• The sample comprised two subsamples assessed using different diagnostic tests focusing on calculation (HRT 1-4) or basic numerical capacities (ZAREKI-R).
• Variables included intelligence, reading fluency, working memory, attention, and various mathematical skills.

Main Results:

• Convincing evidence for two subtypes of dyscalculia was found: a slightly impaired subtype and a strongly impaired subtype.
• Subtypes differed most significantly in mathematical abilities; attention difficulties emerged as a key distinguishing factor.
• No substantial differences in intelligence, working memory, or reading fluency were observed between subtypes.

Conclusions:

• The findings support the existence of two distinct subtypes of dyscalculia, with comorbid attention difficulties being a relevant consideration.
• Interventions for children with dyscalculia should consider the potential presence of a subtype with significant attention problems.
• The identified subtypes appear robust, regardless of the specific diagnostic test used for dyscalculia assessment.