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

y Studies 5 and 6 of the current thesis. Against the background of the findings suggesting a
disruption of the mental number line by hemi-spatial neglect (e.g., Zorzi, Priftis, & Umltà,
2002; Priftis, Zorzi, Meneghello, Marenzi, & Umltà, 2006) and the suggested existence of
multiple number lines (i.e., one for each power level: units, tens, etc, see Nuerk et al., 2001;
Nuerk & Willmes, 2005 for a more detailed discussion) the question comes up in how far
hemi-spatial neglect affects place-value attributes of the to-be-processed numbers. In Study 5
the number bisection task was employed to evaluate the consequences of hemi-spatial neglect
on the processing of place-value information. Thereby, using a task for which a crucial
influence of place-value knowledge on task performance is known (see Nuerk et al., 2002) to
assess place-value influences in neuropsychologically relevant group of participants to
increase our knowledge on the generalizability of decomposed processing of two-digit
numbers. In Study 6 the same task is again employed to evaluate possible neural correlates of
place-value processing in particular. Wood and colleagues (2006b) were able to narrow down
specific processes of place-value integration as reflected by the compatibility effect in twodigit
magnitude comparison to a small area within the intraparietal sulcus. Thus, it was
hypothesized that place-value processing as required in the number bisection task should lead
to specific neural activation at a comparable site. Thereby, converging evidence for specific
neural processing related to place-value representations would be provided from a different
task, again corroborating the notion of decomposed processing of tens and units to be a quite
general characteristic of multi-digit number processing.
Finally, the interpretation of empirical evidence should be guided by theoretical
considerations, possibly formalized by a theoretical model. Nuerk and Willmes (2005, see
also Nuerk et al., 2001 for first sketches and Knops, 2006 for further specifications) provided
such a model of decomposed processing for the case of two-digit number comparison.
Moreover, in recent years, a growing number of studies tried to implement the constraints of
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