Magnitude Processing in Developmental Dyscalculia : A Heterogeneous Learning Disability with Different Cognitive Profiles

Abstract

Developmental dyscalculia (DD) is a learning disability that is characterized by severe difficulties with acquiring age-appropriate mathematical skills that cannot be attributed to insufficient education, language skills, or motivation. The prevalence rate is estimated at 3-6%, meaning that a substantial portion of the population struggles to learn mathematics to such a large degree that it affects overall well-being and academic prospects. However, our understanding of the etiology of DD is incomplete and there are competing hypotheses regarding the characteristics of DD and its underlying causal factors. The purpose of the current thesis is to contribute to our understanding of DD from the perspective of cognitive psychology and cognitive neuroscience. To this end, we identify children with DD to identify the cognitive determinants of DD that hamper their ability to learn basic mathematics. It is believed that human beings are endowed with an innate ability to represent numerosities, an ability phylogenetically shared with other species.We investigate whether the purported innate number system plays a role in children with DD insofar as failures in this system may undermine the acquisition of symbolic representations of number. Although some researchers believe DD is a monolithic learning disability that is genetic and neurobiological in origin, the empirical support for various hypotheses suggests that DD may be shaped by heterogeneous characteristics and underlying causes. The present thesis, and the studies presented therein, provides support for the notion that DD is indeed heterogeneous. We identify at least two subtypes of DD that are characterized by specific deficits in number processing, and one subtype that could more aptly be labelled as a mathematical learning disability, the causal factors of which are likely limited to deficits in non-numerical abilities. In addition, we locate candidate neurocognitive correlates that may be dysfunctional in DD.

Numeracy deficits scrutinized: Evidences of primary developmental dyscalculia.

“…In the present study, the scores of children in the ND group showed specific deficits in the calculation system (Vukovic & Siegel, 2010). However, DD is a heterogeneous disorder, and individual differences must be considered because deficits may vary according to the stage of development (Haase et al, 2012; Mazzocco & Räsänen, 2013; Skagerlund, 2016; Skagerlund & Träff, 2016b). For example, in the present sample, some of the children presented deficits in the contextual estimation task, number comprehension system, and positioning of numbers on an analogue scale (i.e., number line), whereas other children presented deficits in reading number tasks that are related to number production and oral comparisons that correspond to number comprehension, but these children presented average performance on other subtests of the Zareki-R. Heterogeneous profiles must be carefully considered in terms of follow-up and rehabilitation (Ribeiro & Santos, 2017; Santos et al, 2017; Skagerlund, 2016; Skagerlund & Träff, 2016b).…”

“…Studies of numerical cognition in children with DD have found that a major difficulty for such children involves the assessment of number magnitude using Arabic symbols compared with nonsymbolic numerosity per se (Lafay, St-Pierre, & Macoir, 2016; Rousselle & Noël, 2007; Silva & Santos, 2011). It is important to identify the cognitive profile of ND in individual child because such deficits can vary widely, even within a DD group (Skagerlund, 2016). Such identification can help establish the most appropriate intervention for each case based on different diagnostic profiles (Santos, Silva, Paula, von Aster, & Dellatolas, 2017) to strengthen the functioning of numerical cognition systems (Haase et al, 2012; Haase, Júlio-Costa, & Santos, 2015; Menon, 2016; Silva et al, 2015).…”

Number Line Estimations, Place Value Understanding and Mathematics Achievement

“…Two basic stones of mathematics are number and shape. In other words, at the core, mathematics is mainly about establishing relationships between spatial structures and quantities (Skagerlund, 2016). In fact, at the early stages, doing/learning mathematics is considered to be a quantification process.…”

“…This skill is vital and very important for survival of the animals, for example, in foraging and hunting. They require the apprehension first, and then perhaps discrimination, of one or more sets of vital objects in the immediate surroundings (Skagerlund, 2016). Similarly, ANS is even more important for human being.…”

“…It may facilitate children's early understanding of numbers such as assigning values to countable quantities, and later the acquisition of other number related concepts (Chu, vanMarle, & Geary, 2015). In fact, accumulating evidence persistently shows that the ANS acuity and later mathematics performance are strongly related (Skagerlund, 2016).…”