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The influence of the place-value structure of the Arabic number ...

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system and <strong>the</strong> ordinality <strong>of</strong> <strong>the</strong> mental <strong>number</strong> line, respectively) <strong>of</strong> <strong>the</strong> von Aster and Shalev<br />

(2007) model as it is a general ordering principle <strong>of</strong> <strong>the</strong> <strong>Arabic</strong> <strong>number</strong> systems and was also<br />

shown to <strong>influence</strong> <strong>the</strong> development <strong>of</strong> a spatial mental <strong>number</strong> line representation (cf.<br />

Moeller et al., 2009b; Study 3). This interpretation is corroborated by <strong>the</strong> authors’ description<br />

<strong>of</strong> typical impairments <strong>of</strong> children with dyscalculia for each <strong>of</strong> <strong>the</strong> four developmental stages.<br />

For stage three, transcoding errors related to <strong>the</strong> inversion property <strong>of</strong> e.g., <strong>the</strong> German<br />

<strong>number</strong> word system are mentioned, clearly tapping <strong>place</strong>-<strong>value</strong> processing. Never<strong>the</strong>less, <strong>the</strong><br />

authors did not specify <strong>the</strong> issue <strong>of</strong> <strong>place</strong>-<strong>value</strong> representations within <strong>the</strong> context <strong>of</strong> <strong>the</strong>ir<br />

model <strong>of</strong> <strong>number</strong> acquisition. Moreover, even when considering o<strong>the</strong>r <strong>the</strong>oretical<br />

conceptualizations <strong>of</strong> numerical development and developmental dyscalculia, in particular,<br />

<strong>the</strong> <strong>influence</strong> <strong>of</strong> e.g., insufficient <strong>place</strong>-<strong>value</strong> understanding is widely neglected. In line with<br />

Karmil<strong>of</strong>f-Smith’s developmental <strong>the</strong>ory (1996; 1998), Rubinsten and Henik (2009)<br />

suggested different underlying deficits and <strong>the</strong>ir interactions to determine developmental<br />

dyscalculia and/or ma<strong>the</strong>matical learning disorders. Amongst o<strong>the</strong>rs, <strong>the</strong> authors proposed<br />

deficits in magnitude/quantity processing, working memory, attentional resources, and<br />

executive functioning to be relevant for ma<strong>the</strong>matics impairments, but again did not<br />

specifically address processing <strong>of</strong> <strong>place</strong>-<strong>value</strong> information.<br />

Taken toge<strong>the</strong>r, <strong>the</strong>re is so far no comprehensive <strong>the</strong>ory <strong>of</strong> numerical development,<br />

ei<strong>the</strong>r typical or atypical, explicitly considering <strong>place</strong>-<strong>value</strong> understanding to be a relevant and<br />

necessary step in emerging numerical cognition. Taking into account <strong>the</strong> finding obtained in<br />

<strong>the</strong> current <strong>the</strong>sis, in particular <strong>the</strong> longitudinal <strong>influence</strong> <strong>of</strong> early <strong>place</strong>-<strong>value</strong> understanding<br />

on later arithmetic performance it would be desirable to fur<strong>the</strong>r conceptualize <strong>the</strong><br />

developmental impact <strong>of</strong> <strong>place</strong>-<strong>value</strong> knowledge by explicitly incorporating it into a model <strong>of</strong><br />

numerical development such as <strong>the</strong> model by von Aster and Shalev (2007). Within this<br />

framework, implementing a representation <strong>of</strong> <strong>the</strong> Place-<strong>value</strong> <strong>structure</strong> <strong>of</strong> <strong>the</strong> <strong>Arabic</strong> <strong>number</strong><br />

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