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

et al., 2006). However, we hypothesize that the effect of decade crossing might be altered by
neglect. Neglect patients may have particular difficulties with triplets in which a decade
boundary is crossed: in such decade-crossing triplets, not only perception and representation
of the units is required, but in addition the decade digits, which are perceptually and perhaps
mentally on the neglected left side within a two-digit number, need to be processed. This can
be accounted for by a deeper magnitude and base-ten processing required to correctly classify
these triplets (Nuerk et al., 2002; Wood, Nuerk, & Willmes, 2006). More specifically, the
impact of decade crossing should be more pronounced for those triplets that involve a decade
crossing between the first and the central number as deeper magnitude evaluation on the left
of a given numerical interval is needed.
In summary, neglect patients should be particularly affected (i) in triplets involving
central numbers smaller than the arithmetical middle of the interval (which are presumably
located on the left of the mental numerical interval) and (ii) in triplets crossing a decade
boundary; they should not be affected by (iii) general distance properties or (iv)
multiplicativity.
MATERIALS AND METHODS
Participants: Eighteen German-speaking participants took part in this study.
Participants were pooled into three groups of 6 persons matched for age, gender, education
and time post-lesion (4 males/2 females each, see Table 1): a patient group including 6
patients with right-sided lesions who suffered from left-sided neglect; a patient control group
involving 6 patients with right-sided lesions but no clinical signs of neglect; and a healthy
control group of 6 participants with no history of neurological or psychological illness. In all
cases of stroke, (patient group and patient control group) lesions were confirmed by either
MRI or CT. However, one patient (patient control group) was tested four years post-lesion
and could not be matched for the parameter time post-lesion.
208