Approximate additions and working memory in individuals with Down syndrome Carmen Belacchi a, *, Maria Chiara Passolunghi b , Elena Brentan c , Arianna Dante c , Lara Persi a , Cesare Cornoldi c a Department of Human Sciences, University of Urbino ‘‘Carlo Bo’’, Italy b Department of Life Sciences, University of Trieste, Italy c Department of General Psychology, University of Padova, Italy 1. Introduction When teaching and supporting cognitively impaired individuals, it is crucial to examine to what extent they can learn not only formal mathematics, an area where they typically have severe difficulties (Buckley, 1985; Pieterse & Treloar, 1981), but also intuitive mathematics, which may help them to adapt to the demands of the environment. Intellectually disabled individuals frequently have to make decisions based on estimating the numerosity of sets, and particularly the numerosity resulting from the sum of successively presented sets. For instance, they may have taken Research in Developmental Disabilities xxx (2014) xxx–xxx ARTICLE INFO Article history: Received 1 December 2013 Received in revised form 26 January 2014 Accepted 28 January 2014 Available online xxx Keywords: Mathematical skills Down syndrome Working memory ABSTRACT There is some evidence that individuals with Down syndrome (DS) may have a poorer mathematical performance and a poorer working memory (WM) than typically developing (TD) children of the same mental age. In both typical and atypical individuals, different aspects of arithmetic and their relationships with WM have been largely studied, but the specific contribution of WM to the representation and elaboration of non-symbolic quantities has received little attention. The present study examined whether individuals with DS are as capable as TD children matched for fluid intelligence of estimating numerosity both of single sets and of added sets resulting when two sequentially presented sets are added together, also considering how these tasks related to verbal and visuospatial WM. Results showed that the DS group’s performance was significantly worse than the TD group’s in numerosity estimation involving one set, but not when estimating the numerosity resulting from the addition. Success in the addition task was related to success in the working memory tasks, but only for the group with DS; this applied especially to the visuospatial component, which (unlike the verbal component) was not impaired in the group with DS. It is concluded that the two numerosity tasks involve different processes. It is concluded that the arithmetical and working memory difficulties of individuals with DS are not general, and they can draw on their WM resources when estimating the numerosity of additions. ß 2014 Elsevier Ltd. All rights reserved. * Corresponding author. Tel.: +390722305813. E-mail address: carmen.belacchi@uniurb.it (C. Belacchi). G Model RIDD-2204; No. of Pages 9 Please cite this article in press as: Belacchi, C., et al. Approximate additions and working memory in individuals with Down syndrome. Research in Developmental Disabilities (2014), http://dx.doi.org/10.1016/j.ridd.2014.01.036 Contents lists available at ScienceDirect Research in Developmental Disabilities http://dx.doi.org/10.1016/j.ridd.2014.01.036 0891-4222/ß 2014 Elsevier Ltd. All rights reserved.