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

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<strong>the</strong>m. As could already been inferred from <strong>the</strong> raw correlations <strong>the</strong> data produced by <strong>the</strong><br />

decomposed and <strong>the</strong> hybrid model (Z decomposed = .95; Z hybrid = .78) showed a significantly<br />

better fit to <strong>the</strong> empirical data than <strong>the</strong> holistic model (Z holistic = .001; difference in z-scores:<br />

holistic vs. decomposed = 5.40, holistic vs. hybrid = 4.50; critical difference at <strong>the</strong> .05<br />

significance level = ±1.96). However, <strong>the</strong> difference between <strong>the</strong> model fit <strong>of</strong> <strong>the</strong> strictly<br />

decomposed and <strong>the</strong> hybrid model was not statistically reliable (difference in z-scores = 0.90).<br />

In summary, <strong>the</strong> results pattern for <strong>the</strong> comparisons to a fixed standard only partly<br />

mirrored that observed for comparisons to a variable standard: (i) Again, all current<br />

computational models were able to simulate <strong>the</strong> distance effect. Additionally, (ii) <strong>the</strong><br />

inclusion <strong>of</strong> <strong>the</strong> predictor overall difference in <strong>the</strong> final regression model was also not<br />

necessarily determined by <strong>the</strong> presence <strong>of</strong> a holistic representation. However, (iii) <strong>the</strong><br />

compatibility effect could not be accounted for by <strong>the</strong> two models involving a holistic<br />

representation <strong>of</strong> <strong>number</strong> magnitude, i.e., <strong>the</strong> purely holistic and <strong>the</strong> hybrid model.<br />

Never<strong>the</strong>less, (iv) <strong>the</strong> strictly decomposed model did not perform better than <strong>the</strong> more<br />

complex hybrid model in terms <strong>of</strong> descriptive adequacy. Anyway, <strong>the</strong> data obtained from <strong>the</strong><br />

strictly decomposed as well as <strong>the</strong> hybrid model achieved a satisfactory fit to <strong>the</strong> empirical<br />

data and performed reliably better than <strong>the</strong> holistic model.<br />

DISCUSSION<br />

<strong>The</strong> present study set <strong>of</strong>f to provide a first comparison <strong>of</strong> <strong>the</strong> three currently proposed<br />

modes <strong>of</strong> two-digit <strong>number</strong> magnitude representations (i.e., holistic, strictly decomposed, or<br />

hybrid) using a computational modelling approach. It was expected that all three models<br />

should be able to account for <strong>the</strong> distance effect, whereas only <strong>the</strong> strictly decomposed and<br />

<strong>the</strong> hybrid model, but not <strong>the</strong> holistic model, should successfully simulate <strong>the</strong> unit-decade<br />

compatibility effect. Additionally, when incorporation <strong>of</strong> a predictor representing a measure<br />

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