Developmental dyscalculia and basic numerical capacities: a study of 8 – 9-year-old students Karin Landerl a,b , Anna Bevan a , Brian Butterworth a, * a Institute of Cognitive Neuroscience, University College London, 17 Queen Square, London WC1N 3AR, UK b Department of Psychology, University of Salzburg, Salzburg, Austria Received 21 March 2003; revised 17 September 2003; accepted 13 November 2003 Abstract Thirty-one 8- and 9-year-old children selected for dyscalculia, reading difficulties or both, were compared to controls on a range of basic number processing tasks. Children with dyscalculia only had impaired performance on the tasks despite high-average performance on tests of IQ, vocabulary and working memory tasks. Children with reading disability were mildly impaired only on tasks that involved articulation, while children with both disorders showed a pattern of numerical disability similar to that of the dyscalculic group, with no special features consequent on their reading or language deficits. We conclude that dyscalculia is the result of specific disabilities in basic numerical processing, rather than the consequence of deficits in other cognitive abilities. q 2004 Published by Elsevier B.V. Keywords: Dyscalculia; Numerical processing; Intelligence; Working memory; Arithmetic development 1. Introduction Mathematics is a complex subject, involving language, space and quantity. Much research into the development of mathematical skills has focused upon relatively basic numerical abilities, such as arithmetic or counting (Bisanz, 1999a), but even at such early levels many complex abilities are involved. These include transcoding between spoken number words and Arabic numerals, relating these to semantic representations of set size (“numerosity”), reasoning about relative set sizes (if 1 is added to 2, the result should be 3); and understanding the relations between set size and counting order. 0022-2860/$ - see front matter q 2004 Published by Elsevier B.V. doi:10.1016/j.cognition.2003.11.004 Cognition 93 (2004) 99–125 www.elsevier.com/locate/COGNIT * Corresponding author. Fax: þ 44-71-580-1100. E-mail address: b.butterworth@ucl.ac.uk (B. Butterworth).