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Subitizing and Visual Counting in Dyscalculia

Burkhart Fischer, Christine Gebhardt, and Klaus Hartnegg

Center of Neuroscience
Optomotor Laboratory
University of Freiburg

The ability of recognizing the number of briefly presented items without actually counting is called subitizing (from lat. subito = suddenly). Adult subjects can subitize 3 to 4 items. For greater numbers the subjects begin a counting process, which needs increasingly more time as the number of items increase. For children there exits a long lasting development of accuracy and speed of subitizing and counting, which lasts up to the adult age of 18 years.

This study tests the hypothesis that children with difficulties in acquiring basic arithmetic skills exhibit developmental deficits in subitizing and/or counting. Altogether, 219 control and 156 subjects with dyscalculia in the age range of 7 to 17 years were given a visual counting task, in which 1 to 9 items were presented for 100 ms. The subjects had to press a digit key on a numerical keyboard to indicate the number of items they had seen. Percentages of correct responses and response times were recorded.

The analysis shows systematic differences between control and dyscalculia children. The percentage of dyscalculia children performing below the 16-percentile of the age matched controls was estimated between 40% and 78% increasing with age.

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