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

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corroborated by a variety <strong>of</strong> observations indexing decomposed processing <strong>of</strong> tens and units<br />

in more complex numerical tasks such as <strong>the</strong> <strong>number</strong> bisection task and even locating a<br />

specific area within <strong>the</strong> intraparietal sulcus associated with processes <strong>of</strong> <strong>place</strong>-<strong>value</strong><br />

integration (cf. Study 5). <strong>The</strong>se imaging results were accompanied by patient data (cf. Study<br />

6) again suggesting separate processing <strong>of</strong> tens and units as well as a representation <strong>of</strong> <strong>place</strong><strong>value</strong><br />

information to be impaired by hemi-spatial neglect in a way previously assumed to be<br />

affect <strong>the</strong> spatial representation <strong>of</strong> <strong>number</strong> magnitude (i.e., <strong>the</strong> mental <strong>number</strong> line) only.<br />

<strong>The</strong>re<strong>of</strong>, we inferred <strong>the</strong> mental <strong>number</strong> line representation <strong>of</strong> <strong>number</strong> magnitude to involve at<br />

least some kind <strong>of</strong> <strong>place</strong>-<strong>value</strong> information. In this vein, <strong>the</strong> results <strong>of</strong> Study 2 imply that<br />

<strong>place</strong>-<strong>value</strong> information is not only an important aspect / cue in basic numerical tasks but also<br />

specifically processed in basic arithmetic such as addition, in particular, when processes <strong>of</strong><br />

<strong>place</strong>-<strong>value</strong> integration are required to calculate <strong>the</strong> correct result as in carry addition<br />

problems. Finally, <strong>the</strong>se conclusions drawn on <strong>the</strong> current empirical data are backed by <strong>the</strong><br />

computational results provided by a neural network model <strong>of</strong> two-digit <strong>number</strong> comparison.<br />

Here, it was found that a strictly decomposed model accounted best for <strong>the</strong> empirical data (cf.<br />

Study 7), <strong>the</strong>reby, indicating no need for an additional holistic representation as proposed by<br />

<strong>the</strong> hybrid model <strong>of</strong> two-digit <strong>number</strong> representation (cf. Nuerk & Willmes, 2005). Taken all<br />

<strong>the</strong>se evidence toge<strong>the</strong>r, an essential role <strong>of</strong> <strong>the</strong> <strong>place</strong>-<strong>value</strong> structuring principle <strong>of</strong> <strong>the</strong> <strong>Arabic</strong><br />

<strong>number</strong> system for <strong>the</strong> adult human representation <strong>of</strong> <strong>number</strong> magnitude seems undisputed.<br />

Never<strong>the</strong>less, recent findings from studies investigating <strong>the</strong> development <strong>of</strong> numerical<br />

competencies reported evidence suggesting an important role <strong>of</strong> <strong>place</strong>-<strong>value</strong> understanding<br />

even for early numerical development. <strong>The</strong> findings from <strong>the</strong> current <strong>the</strong>sis addressing <strong>the</strong><br />

<strong>influence</strong> <strong>of</strong> <strong>the</strong> <strong>place</strong>-<strong>value</strong> <strong>structure</strong> <strong>of</strong> <strong>the</strong> <strong>Arabic</strong> <strong>number</strong> system on <strong>the</strong> development <strong>of</strong><br />

numerical competencies as well as <strong>the</strong> developmental trajectories <strong>of</strong> <strong>place</strong>-<strong>value</strong><br />

understanding will be discussed in <strong>the</strong> following section.<br />

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