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

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executing <strong>the</strong> carry by updating <strong>the</strong> decade digit <strong>of</strong> <strong>the</strong> result by <strong>the</strong> decade digit <strong>of</strong> <strong>the</strong> unit<br />

sum. Increased activation at similar sites associated with decade crossing triplets may thus<br />

implicate processes <strong>of</strong> unit decade integration to require executive / attentional as well as<br />

working memory resources supplementing <strong>the</strong> more demanding processing <strong>of</strong> magnitude<br />

information in <strong>the</strong>se triplets. More particularly, this indicated that <strong>the</strong> structural organizing<br />

<strong>place</strong>-<strong>value</strong> principle <strong>of</strong> <strong>the</strong> <strong>Arabic</strong> <strong>number</strong> system requires specific processing. Thus,<br />

processing <strong>place</strong>-<strong>value</strong> information is not an inherent aspect <strong>of</strong> <strong>number</strong> magnitude<br />

representation but may involve different magnitude-based as well as more general cognitive<br />

processes. Moreover, which <strong>of</strong> <strong>the</strong>se processes are actually performed or not may also depend<br />

on <strong>the</strong> task to be performed. While in <strong>number</strong> magnitude comparison tens and units seem to<br />

be encoded and processed in parallel (cf. Moeller et al., 2009a) performance in a more<br />

complex task such as <strong>the</strong> <strong>number</strong> bisection task was suggested to involve quite different basic<br />

numerical processes including bottom-up processing <strong>of</strong> specific stimulus characteristics as<br />

well as top-down mediated processes <strong>of</strong> e.g., plausibility evaluations (cf. Moeller, Fischer,<br />

Nuerk, & Willmes, 2009c).<br />

Eye-tracking evidence on <strong>place</strong>-<strong>value</strong> processing in mental addition<br />

As described currently, Moeller and colleagues (2009a; 2009c) were able to evaluate<br />

processing characteristics for numerical tasks. <strong>The</strong> authors chose <strong>the</strong> eye-tracking<br />

methodology to differentiate between different processing strategies (Moeller et al., 2009a) or<br />

<strong>the</strong> temporal specificities <strong>of</strong> different numerical processes (Moeller et al., 2009c). <strong>The</strong><br />

evaluation <strong>of</strong> participants’ eye fixation behaviour while engaged in a given task seems to be a<br />

valid tool to distinguish between different basic numerical processes because <strong>of</strong> two general<br />

assumptions about eye fixations: (i) According to <strong>the</strong> eye mind assumption (e.g., Rayner &<br />

Pollatsek, 1989) <strong>the</strong> fixation location <strong>of</strong> <strong>the</strong> eyes serves as a reliable indicator <strong>of</strong> what part <strong>of</strong><br />

a stimulus is processed at <strong>the</strong> moment. And (ii) <strong>the</strong> immediacy assumption (e.g., Rayner &<br />

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