Language affects symbolic arithmetic in children: The case of number word inversion

• Response times are higher for sums when adding units leads to a decade change (carry-effect).
• Number word inversion: sequence of tens and units in words is inverted compared to Arabic notation.
• 7- to 9-year-old children were tested on a symbolic addition task.
• Larger carry effect for number word inversion and larger verbal working memory.
• Language of instruction is an important factor in children’s mathematical education.

Specific language influences have been observed in basic numerical tasks such as magnitude comparison, transcoding, and the number line estimation task. However, so far language influences in more complex calculations have not been reported in children. In this translingual study, 7- to 9-year-old German- and Italian-speaking children were tested on a symbolic addition task. Whereas the order of tens and units in Italian number words follows the order of the Arabic notation, the order is inverted in German number words. For both language groups, addition problems were more difficult when a carry operation was needed, that is, when a manipulation within the place-value structure of the Arabic number system was particularly important. Most important, this carry effect was more pronounced in response latencies for children speaking German, a language with inverted verbal mapping of the place-value structure. In addition, independent of language group, the size of the carry effect was significantly related to verbal working memory. The current study indicates that symbolic arithmetic and the carry effect in particular are modulated by language-specific characteristics. Our results underline the fact that the structure of the language of instruction is an important factor in children’s mathematical education and needs to be taken into account even for seemingly nonverbal symbolic Arabic tasks.