Numerical distance effect in developmental dyscalculia

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Abstract

Children in third and fourth grades suffering from developmental dyscalculia (DD) and typically developing children were asked to compare numbers to a standard. In two separate blocks, they were asked to compare a number between 1 and 9 to 5, or a two-digit number between 10 and 99 to 55. In the single-digit comparisons, DD children were comparable to the control group in reaction time but showed a difference in error rates. In the two-digit number comparisons, DD children presented a larger distance effect than the controls. In addition, they were more influenced by the problem size than controls were. Assuming an analog representation of quantities, this suggests that quantities are less differentiated in those with DD than in typically developing children.

Section snippets

Participants

Twenty-nine children were selected from 600 third or fourth grade children from 5 state elementary schools in Beer-Sheva, Israel. Thirteen (11 female) were diagnosed with DD, while the 16 controls had no learning disabilities. The mean age of the DD group was 9-5 with a SD of 0.9 months. The diagnostic test for DD was based on the Israeli Ministry of Education curriculum (for details see Mark-Zigdon, Ashkenazi, & Henik, in preparation).

Teachers were asked to report children with major

Results

RTs that were shorter than 200 ms and longer than 5500 ms were excluded from the analysis. In the one-digit block, an analysis of variance (ANOVA) was conducted for RT and error rate. For the two-digit block, a regression analysis was conducted for RT and error rate.

Discussion

In summary, first in single-digit comparisons, DD participants presented a numerical distance effect comparable to the control participants in RT. They also showed a distance effect in the error rates whereas the controls showed no such error-rate effect. Second, DD participants presented a larger numerical distance effect in two-digit comparisons tasks compared to the control group in the RT analysis. Third, DD participants were more influenced by the size of the compared number than the

Acknowledgements

We would like to thank Hans-Christoph Nuerk for his very constructive comments and help with the statistical analysis. This research was supported by the Israel Science Foundation, Grant 122/05.

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