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

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Study 6 examined <strong>the</strong> <strong>influence</strong> <strong>of</strong> <strong>the</strong> disruption <strong>of</strong> <strong>the</strong> mental <strong>number</strong> in neglect<br />

patients – as first reported by Zorzi, Priftis, and Umiltà (2002) – on <strong>the</strong> processing <strong>of</strong> <strong>place</strong><strong>value</strong><br />

information. Zorzi and co-workers (2002; see also Zorzi, Priftis, Meneghello, Marenzi,<br />

& Umiltà, 2006) observed that, when asked to indicate <strong>the</strong> midpoint <strong>of</strong> a numerical interval,<br />

patients’ perceived midpoints <strong>of</strong> <strong>the</strong> intervals were mis<strong>place</strong>d to <strong>the</strong> right (reporting 7 as being<br />

midway between 1 and 9) similarly to <strong>the</strong>se patients impairments in line bisection. In <strong>the</strong><br />

present study, interest was paid to <strong>the</strong> question whe<strong>the</strong>r neglect-related deficiencies also affect<br />

<strong>the</strong> processing <strong>of</strong> <strong>place</strong>-<strong>value</strong> information as conceptualized by decade crossings in a<br />

verification version <strong>of</strong> <strong>the</strong> <strong>number</strong> bisection task (e.g., 23_26_29 vs. 25_28_31; see also Study<br />

5). Results showed that neglect patients’ performance for triplets crossing a decade boundary<br />

was significantly worse than performance <strong>of</strong> <strong>the</strong> control group. Fur<strong>the</strong>rmore, neglect patients<br />

were particularly impaired when <strong>the</strong> decade crossing occurred between <strong>the</strong> first and <strong>the</strong><br />

second <strong>number</strong> <strong>of</strong> <strong>the</strong> triplet ra<strong>the</strong>r than when <strong>the</strong> decade crossing occurred between <strong>the</strong><br />

second and <strong>the</strong> third <strong>number</strong> (e.g., 28_31_34 vs. 25_28_31). <strong>The</strong>se results denote that not<br />

only <strong>the</strong> processing <strong>of</strong> <strong>number</strong> magnitude information but also <strong>the</strong> representation <strong>of</strong> <strong>the</strong> <strong>place</strong><strong>value</strong><br />

<strong>structure</strong> <strong>of</strong> <strong>the</strong> <strong>Arabic</strong> <strong>number</strong> system is impaired in neglect patients.<br />

Section 5: A computational model <strong>of</strong> <strong>place</strong>-<strong>value</strong> integration in two-digit <strong>number</strong><br />

comparison<br />

Finally, Study 7 provided first computational evidence helping to differentiate<br />

between three different representational formats <strong>of</strong> two-digit <strong>number</strong>s (i.e., holistic, strictly<br />

decomposed, or hybrid). Particular attention was paid to <strong>the</strong> dissociation <strong>of</strong> <strong>the</strong> strictly<br />

decomposed and <strong>the</strong> hybrid model as <strong>the</strong>re is currently no empirical data that allows<br />

distinguishing between <strong>the</strong>se two assumptions. To pursue <strong>the</strong>se issues three computational<br />

models were programmed realizing an ei<strong>the</strong>r holistic, decomposed or hybrid representation <strong>of</strong><br />

two-digit <strong>number</strong> magnitude. In both <strong>the</strong> comparison <strong>of</strong> a given <strong>number</strong> to a fixed as well as a<br />

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