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

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unit and decade distance must be processed separately to result in <strong>the</strong> antidromic <strong>influence</strong><br />

just mentioned (see also Nuerk & Willmes, 2005 for a more detailed discussion <strong>of</strong> this point.<br />

Yet, to account for <strong>the</strong> compatibility effect a model is necessary that allows us to<br />

differentiate between processing <strong>the</strong> tens digits and processing <strong>the</strong> unit digits complying with<br />

<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: a strictly decomposed or at least a<br />

hybrid model <strong>of</strong> two-digit <strong>number</strong> representation. In <strong>the</strong> strictly decomposed model <strong>the</strong><br />

magnitudes <strong>of</strong> tens and units are represented separately (possibly on concomitant <strong>number</strong><br />

lines, cf. Verguts & De Moor, 2005; see Nuerk and Willmes, 2005 for a review) and <strong>the</strong><br />

overall magnitude <strong>of</strong> a two-digit <strong>number</strong> is achieved by integrating <strong>the</strong> single digits’ <strong>of</strong> tens<br />

and units magnitudes into <strong>the</strong>ir respective position within <strong>the</strong> <strong>place</strong>-<strong>value</strong> <strong>structure</strong> <strong>of</strong> <strong>the</strong><br />

<strong>Arabic</strong> <strong>number</strong> system (henceforth referred to as <strong>place</strong>-<strong>value</strong> integration, see also Poltrock &<br />

Schwartz, 1984 for an early inclusion <strong>of</strong> <strong>place</strong>-<strong>value</strong> knowledge into <strong>the</strong> decision process in<br />

<strong>number</strong> comparison). <strong>The</strong>reby, <strong>the</strong> <strong>place</strong>-<strong>value</strong> <strong>structure</strong> is a necessary prerequisite for<br />

correctly representing multi-digit <strong>number</strong>s. In <strong>the</strong> hybrid model (cf. Nuerk et al., 2001; Nuerk<br />

& Willmes, 2005) above described decomposed representation is accompanied by a holistic<br />

representation <strong>of</strong> <strong>the</strong> <strong>number</strong>’s overall magnitude, meaning each <strong>number</strong> to be represented as<br />

an integrated entity <strong>of</strong> all its constituting digits without retaining <strong>the</strong> <strong>place</strong>-<strong>value</strong> <strong>structure</strong>.<br />

So, brought up by <strong>the</strong> observation <strong>of</strong> <strong>the</strong> compatibility effect (Nuerk et al., 2001) decomposed<br />

processing <strong>of</strong> tens and units in two-digit <strong>number</strong> comparison and on a broader level <strong>the</strong><br />

possibility <strong>of</strong> an (additional) representation <strong>of</strong> <strong>number</strong> magnitude in terms <strong>of</strong> separate coding<br />

<strong>of</strong> each power level (cf. McCloskey, 1992) had to be considered as an alternative to <strong>the</strong><br />

traditional assumption <strong>of</strong> an analogue holistic representation <strong>of</strong> all <strong>number</strong>s disregarding <strong>the</strong><br />

<strong>place</strong>-<strong>value</strong> <strong>structure</strong> <strong>of</strong> <strong>the</strong> <strong>Arabic</strong> <strong>number</strong> system (cf. Dehaene et al., 1990).<br />

Never<strong>the</strong>less, although <strong>the</strong>re is cumulating evidence for <strong>the</strong> notion <strong>of</strong> decomposed<br />

processing <strong>of</strong> multi-digit <strong>number</strong>s from more and more numerical tasks (see below for a brief<br />

16

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