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AbstractDyscalculia, or mathematics learning disorders, is currently known to be heterogeneous (Wilson & Dehaene, ). While various profiles of dyscalculia coexist, a general and persistent hallmark of this math learning disability is the difficulty in memorizing arithmetic facts (Geary, Hoard & Hamson, ; Jordan & Montani, ; Slade & Russel, ). Arithmetic facts are simple arithmetic problems that are solved by direct retrieval from memory. Recently, De Visscher and Noël () showed hypersensitivity‐to‐interference in memory in an adult suffering from a specific deficit of arithmetic facts storage. According to the authors, arithmetic facts share many features. The overlapping of these features between arithmetic facts may provoke interference. Consequently, learners who are hypersensitive‐to‐interference could have considerable difficulties in storing arithmetic facts. The present study aims at testing this new hypothesis on fourth‐grade children who are learning multiplication tables. Among 101 children that were assessed, 23 low arithmetic facts learners were selected because of their low score in arithmetic facts fluency (controlling for processing speed). Twenty‐three control children were selected, matched for classroom, gender, and age. In addition to a subtest of global reasoning, these participants were given a multiplication production task and a memorization task of low‐ and high‐interference associations. The results show that children with low arithmetic fluencies experience hypersensitivity‐to‐interference in memory compared with children with typical arithmetic fluencies.

in summary, dyscalcullia is a disorder that can occur in different forms and is most likely to be caused by multiple causes. Indeed, dyscalculity may be the consequence of a basic digital deficit, in particular a difficulty in building an accurate representation of the number. But dyscalcullia may also be linked to a deficit in general cognitive factors. In this chapter we have shown that a very high sensitivity to interference may be linked to a difficulty in encoding arithmetic facts in the long term. Evaluation and rehabilitation work should take account of this heterogeneity. ; En résumé, la dyscalculie est un trouble qui peut se présenter sous différentes formes et qui, très probablement, relève de causes multiples. En effet, la dyscalculie peut être la conséquence d'un déficit numériques de base, en particulier, une difficulté à construire une représentation exacte du nombre. Mais la dyscalculie peut également être liée à un déficit au niveau de facteurs cognitifs généraux. Dans ce chapitre, nous avons montré qu'une très grande sensibilité à l'interférence pouvait être liée à un difficulté à encoder les faits arithmétiques en mémoire à long terme. Le travail d'évaluation et de rééducation devrait prendre en compte cette hétérogénéité.

Numerous studies have tried to identify the core deficit of developmental dyscalculia (DD), mainly by assessing a possible deficit of the mental representation of numerical magnitude. Research in healthy adults has shown that numerosity, duration, and space share a partly common system of magnitude processing and representation. However, in DD, numerosity processing has until now received much more attention than the processing of other non-numerical magnitudes. To assess whether or not the processing of non-numerical magnitudes is impaired in DD, the performance of 15 adults with DD and 15 control participants was compared in four categorization tasks using numerosities, lengths, durations, and faces (as non-magnitude-based control stimuli). Results showed that adults with DD were impaired in processing numerosity and duration, while their performance in length and face categorization did not differ from controls' performance. Our findings support the idea of a nonsymbolic magnitude deficit in DD, affecting numerosity and duration processing but not length processing.