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

versions the strictly decomposed as well as the hybrid model assumes that processing of tens
and units (and overall magnitude) works in perfect parallelism not allowing for any temporal
gradient possibly delaying the processing of e.g., the units. At the moment the present
computational models are not capable to account for such an effect of attentional modulation
or any temporal specifications in the processing of the single representations. Again, future
studies are required to investigate whether such processes indeed contribute to the processing
of two-digit magnitude.
Taken together, it has to be noted that there are a number of questions still to be
answered regarding both the implementation of processing specificities of the individual
models as well as more general processing characteristics. Nevertheless, the current study
indicated that computational modelling is a valuable tool for distinguishing between different
models of two-digit number magnitude representation as it successfully discriminated
between three theoretical models taking into account their capability to simulate standard
effects observed in two-digit number comparison.
CONCLUSIONS
The aim of the present study was to provide first computational evidence for
evaluating the validity of three current models of number magnitude representation: the
holistic (e.g., Dehaene et al., 1990), the strictly decomposed (cf. Verguts & de Moor, 2005),
and the hybrid model (e.g., Nuerk & Willmes, 2005). In particular, we were interested in
distinguishing between the strictly decomposed and the hybrid model as there is currently no
empirical way to discern the two models. The computational results were informative: As
expected, the holistic model could not account for the compatibility effect whereas the
decomposed and the hybrid model did. Moreover, a measure of overall distance between the
to-be-compared numbers was the most important predictor of item RT even though the strictly
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