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

epresentation of number magnitude. In a number line estimation task Moeller and co-workers
(2009b) found that children’s estimates of the spatial position of a given number upon a
hypothetical number line were accounted for best by a two-linear function with a break point
at 10. From this data, Moeller et al. (2009b) concluded that children’s early mental number
line representation seems to differentiate between single- and two-digit numbers. In Study 3
of the present thesis we were able to show that this influence of the structuring principle of the
Arabic number system exhibits its influence on the development of the spatial representation
of number magnitude occurs not only in German-speaking children (cf. Moeller et al., 2009b)
but also in Italian-speaking children, thereby suggesting it to be a rather general principle.
Nevertheless, we also found evidence for a specific influence of the structure of the
languages’ number word systems. This was possible because unlike in German number words
the order of tens and units in Italian number words corresponds to the left-to-right order of
e.g., tens and units in symbolic notation. Base on this difference in the number word systems
of German and Italian we hypothesized the estimates of German-speaking children to be less
accurate as they were more prone to confuse tens and units because of their antidromic order
in verbal and symbolic notation. The results confirmed our hypothesis: The estimates of
Italian-speaking children were reliably more precise as those of their German-speaking
counterparts. Even more interestingly, the finding that this advantage was specifically driven
by the mislocalizing of items for which the confusion of tens and units leads to a large
deviation between the correct position of the number and the actually marked position (e.g.,
82 as compared to 65). Taken together, these results indicate that there is a rather general
influence of the place-value structuring principle of the Arabic number system on the
development of the spatial representation of number magnitude which is valid independent of
cultural influences as long as the Arabic number system is used. However, the data also imply
that this influence is moderated by the language specific attributes such as the number word
system. When the order of tens and units in a language’s number word system does not
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