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

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esponse latencies increased as distance between <strong>the</strong> logarithms <strong>of</strong> <strong>the</strong> <strong>number</strong>s decreased and<br />

absolute problem decreased. As for <strong>the</strong> ANOVA results no indication <strong>of</strong> an <strong>influence</strong> <strong>of</strong> unitdecade<br />

compatibility was observed in <strong>the</strong> regression analysis on RT data modelled by <strong>the</strong><br />

holistic model.<br />

Table 4: Predictors included in <strong>the</strong> final regression model for <strong>the</strong> holistic data<br />

Predictor B b t sign.<br />

Change in<br />

R 2<br />

Raw<br />

correlation<br />

Partial<br />

correlation<br />

Constant 566.18 - 40.46 < .001 - - -<br />

Problem size - .85 - .38 4.39 < .001 .25 - .55 - .13<br />

Diff Log - 90.63 - .36 2.28 < .05 .09 .02 - .35<br />

Finally, <strong>the</strong> regression analysis incorporating only <strong>the</strong> two predictors found to reliably<br />

predict item RT by Moeller et al. (2009b) was predictive as well. However, <strong>the</strong> descriptive<br />

adequacy was considerably reduced as compared to <strong>the</strong> stepwise regression model [adj. R 2 =<br />

.16, R = .45, F(2, 41) = 5.13, p < .01]. Closer inspection <strong>of</strong> <strong>the</strong> beta weights revealed that only<br />

<strong>the</strong> <strong>influence</strong> <strong>of</strong> logarithmic overall distance on item RT was significant [constant = 543.12; B<br />

= -29.84; b = - .42, t = 2.99, p < .01], whereas no reliable <strong>influence</strong> <strong>of</strong> unit distance could be<br />

observed [B = 0.49; b = .17, t = 1.22, p = .23]. Item RT increased as <strong>the</strong> logarithmic distance<br />

between <strong>the</strong> to-be-compared <strong>number</strong>s decreased. Taken toge<strong>the</strong>r, <strong>the</strong> current analyses again<br />

indicate that <strong>the</strong> compatibility effect is hard to reconcile with <strong>the</strong> notion <strong>of</strong> a purely holistic<br />

representation <strong>of</strong> <strong>number</strong> magnitude.<br />

Decomposed model<br />

ANCOVA<br />

For <strong>the</strong> interrelation <strong>of</strong> modelled and empirical RT it was observed that predicting<br />

empirical RT by <strong>the</strong> model data yielded a R 2 <strong>of</strong> .54 indicating a shared variance <strong>of</strong> 54% [r =<br />

.74; F(2, 70) = 82.89, p < .001]. Fur<strong>the</strong>rmore, <strong>the</strong> ANCOVA on <strong>the</strong> RT data produced by <strong>the</strong><br />

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