Processing multi-digit numbers: a translingual eye-tracking study
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The present study aimed at investigating the underlying cognitive processes and language specificities of three-digit number processing. More specifically, it was intended to clarify whether the single digits of three-digit numbers are processed in parallel and/or sequentially and whether processing strategies are influenced by the inversion of number words with respect to the Arabic digits [e.g., 43: dreiundvierzig (“three and forty”)] and/or by differences in reading behavior of the respective first language. Therefore, English- and German-speaking adults had to complete a three-digit number comparison task while their eye-fixation behavior was recorded. Replicating previous results, reliable hundred-decade-compatibility effects (e.g., 742_896: hundred-decade compatible because 7 < 8 and 4 < 9; 362_517: hundred-decade incompatible because 3 < 5 but 6 > 1) for English- as well as hundred-unit-compatibility effects for English- and German-speaking participants were observed, indicating parallel processing strategies. While no indices of partial sequential processing were found for the English-speaking group, about half of the German-speaking participants showed an inverse hundred-decade-compatibility effect accompanied by longer inspection time on the hundred digit indicating additional sequential processes. Thereby, the present data revealed that in transition from two- to higher multi-digit numbers, the homogeneity of underlying processing strategies varies between language groups. The regular German orthography (allowing for letter-by-letter reading) and its associated more sequential reading behavior may have promoted sequential processing strategies in multi-digit number processing. Furthermore, these results indicated that the inversion of number words alone is not sufficient to explain all observed language differences in three-digit number processing.
KeywordsCompatibility Effect Number Word Reading Behavior Unit Digit Orthographic Consistency
Julia Bahnmueller and Stefan Huber were supported by the Leibniz-Competition Fund (SAW-2014-IWM-4) providing funding to Elise Klein. Korbinian Moeller and Hans-Christoph Nuerk were principal investigators at the LEAD Graduate School [GSC1028], a project of the Excellence Initiative of the German federal and state governments.
Compliance with ethical standards
All procedures performed in this study were in accordance with the ethical standards of the ethics committee of the Department of Psychology, University of York (UK) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Conflict of interest
The authors declare that they have no actual or potential conflicts of interest concerning this work.
Informed consent was obtained from all individual participants included in the study.
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