Decomposed but Parallel Processing of Two-Digit Numbers in 1st Graders

S. Pixner1, 2, #, K. Moeller2, 3, #, *, J. Zuber2, 3, H.-C. Nuerk2, 3
1 Department for Child and Adolescent Psychiatry, University Ulm, Ulm, Germany
2 Department of Psychology, Paris-Lodron University Salzburg, Salzburg, Austria
3 Department of Psychology, Eberhard Karls University, Tuebingen, Germany

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© 2009 Pixner et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: ( This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the Eberhard Karls University Tuebingen, Department of Psychology, Friedrichstrase 21, 72072 Tuebingen, Germany; E-mail:
Both authors contributed equally to this manuscript and should be considered as shared first authors


It has been suggested that decomposed processing of two-digit numbers develops from sequential (left-to-right) to parallel with age (Nuerk et al., 2004). However, task demands may have provoked sequential processing as a specific rather than a universal processing style. In the current study a standard unit-decade compatibility effect observed in two-digit number magnitude comparison indicated that first graders were already able to process the single digit magnitudes of tens and units separately and in parallel. Consequently, previous findings of sequential processing may be specific for stimulus characteristics in which such a processing style is useful. It is concluded that even first graders seem to be able to adapt their individual processing styles depending on stimulus properties. More generally, this suggests that the manner by which children process two-digit numbers is strategically adaptive rather than fixed at a particular developmental stage.

Keywords: Children’s number processing, magnitude comparison, compatibility effect.