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

seem to be the origin of the performance dissociation between German- and Italian-speaking
children. To briefly recapitulate, the German number word system differs from the Italian one
as far as for all two-digit numbers above 20 (excluding multiples of 10) the order in which
tens and units are spoken is reversed as compared to the order of symbolic digits constituting
a given number (e.g., 27 “siebenundzwanzig” [seven and twenty]). On the other hand, the
Italian number word system is fully transparent on this (e.g., 27 “ventisette” [twenty
seven]). To evaluate the influence of this inversion property of the German number word
system, the used two-digit items (above 20) were distinguished by the interdigit distance
between their constituting digits, thereby, capturing the estimation error resulting from a
misconception of tens and units in this number. For instance, when mixing up tens and units
of the number 27 and consequently trying to locate 72 on the hypothetic number line, this
leads to a larger misplacement upon the mental number-line than mixing up 45 and 54. As
unit-decade integration into the place-value structure of the Arabic number system may be
more difficult in a language with inversion (cf. Nuerk et al., 2005), German-speaking children
should be more likely to may mix up tens and units. Following this argument, we expected
general estimation performance to be driven by particular difficulties of the German-speaking
children for the items with a large interdigit distance as these were especially affected by
inversion errors. Our analyses confirmed the hypothesized language-specific (inversion)
effect: German-speaking children’s estimates were particularly less accurate for items with a
large digit distance, whereas no language difference could be observed for items with a small
digit distance for which estimation errors were almost identical. Taken together, these results
indicate that estimation accuracy of German-speaking children is particularly poor for items
for which inversion plays a major role in the accurate representation of number magnitude. In
summary, these findings suggest that the observed language-specific performance difference
on the 0-to-100 scale can be attributed to the inversion property of German number words.
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