The differential influence of decades and units on multidigit number comparison

Abstract

What role do the magnitudes of the constituent digits play in three-digit number comparison (e.g., choosing the larger one of two numbers)? The present study addressed this question by examining compatibility effects between hundred and decade digits and between hundred and unit digits. For example, the number pair 372–845 is hundred–decade incompatible because the larger number contains the smaller decade digit, but hundred–unit compatible because the larger number contains the larger unit digit. We obtained significant effects of hundred–decade and hundred–unit compatibility on number comparison times. However, the effect of hundred–unit compatibility was largely restricted to the hundred–decade-compatible condition. These results suggest that place-value information, through decomposition, is automatically taken into account when multidigit numbers have to be compared. Implications of our findings for models of number processing are discussed.

Acknowledgments

This work was supported by Grant MRTN–CT–2003–504927 of the European Community. We wish to thank Marc Brysbaert, Tom Hope, Etienne Korvorst, H.-C. Nuerk, Klaus Willmes, and two anonymous reviewers for their helpful comments and suggestions on an earlier version of this manuscript.

Notes

¹ It could be argued that presenting two vertically aligned numbers for comparison may promote compatibility effects that would be absent with other presentation formats, simply because hundred, decade, and unit digits of each number are directly above one another. However, Nuerk et al. (2004) demonstrated the persistence of number compatibility effects in an experiment for which number pairs were arranged on a diagonal, rather than a vertical, dimension.