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

distance were generally more accurate than estimates for items with a large interdigit distance
(18.77% vs. 13.38% error, respectively). Finally, the influence of the covariate (i.e.,
individual CFT-1 T-values) also reached significance [F(1, 222) = 4.93, p < 0.05].
More specific under- and/or overestimation in German-speaking children
Directly testing whether the hypothesis that German-speaking children’s under-
/overshoot should be more pronounced revealed that the difference in relative estimation
accuracy between items provoking underestimation and items provoking overestimation was
stronger in German- than in Italian-speaking children [t(224) = 1.70, p < .05, tested onesided].
As can be observed from Figure 5B this meant that relative under-/overestimations
were indeed more pronounced in German-speaking children.
To sum up, we did not find significant performance differences between Italian and
Austrian children for items with a small digit distance, whereas reliable differences were
present for items with large inter-digit distances. This indicated language-specific differences
only for those items where inversion errors would lead to a large deviance between the
misunderstood and the actual value of the to-be-estimated number. This interpretation is
further corroborated by the finding that German-speaking children exhibited a more
pronounced estimation performance difference between items either provoking under- or
overestimation of the given number in the expected direction. Taken together, this
corroborates our general interpretation that the poorer performance of German-speaking
children on the number line estimation task seems to be influenced by the German number
word system being less transparent regarding the retention of the place-value structure of the
Arabic number system.
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