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

None of the participants showed clinical signs of dementia or degenerative processes
and all had good to perfect numerical and mathematical abilities, so that the EC 301 R showed
no sign of acalculia in any one patient. Table 2 summarizes the test results of the NET, EC
301 R and SIDAM. For detailed results of the subtests of the NET (e.g. line crossing: patient
M.M. correctly marked 17 out of 36 lines) and EC 301 R (e.g. dot counting: patient M.M. was
not able to count the presented dots) see Appendix A.
Stimuli and design: 160 triplets of two-digit numbers (ranging from 11 to 99) were
used in this study. The triplets were presented in Arabic notation. Overall distance, problem
size, average parity, parity homogeneity, decade-crossing, the inclusion of decade numbers as
well as tie numbers were matched between the respective stimuli groups.
80 non-bisected triplets were organized in a fully crossed 2 x 2 design incorporating the
factors distance to the arithmetical middle (close vs. far) and size relative to the arithmetical
middle (smaller or larger than the arithmetical middle). Distance to the middle refers to the
distance of the presented middle number to the true arithmetical middle of the interval. In the
triplet 21_22_35, the presented central number 22 has a far distance to the arithmetical middle
(i.e. 28 - 22 = 6) while in 21_27_35, 27 is close to the arithmetical middle (i.e. 28 - 27 = 1).
Size relative to the arithmetical middle refers to the position of the central number in relation
to the arithmetical middle of the given interval. For the triplet 33_34_47 the presented middle
number 34 is smaller than the arithmetical middle 40, while in 21_34_35 the number 34 is
larger than the arithmetical middle 28.
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