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

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eliable main effect <strong>of</strong> compatibility was present in <strong>the</strong> RT data produced by <strong>the</strong> hybrid model<br />

[F(1, 39) = 1.24, p = .27, see Figure 3, Panel D]. This indicated that modelled RTs for<br />

compatible comparisons were not reliably faster than RTs for incompatible comparisons (501<br />

ms vs. 505 ms, respectively). Also, <strong>the</strong> interaction <strong>of</strong> compatibility and unit distance was not<br />

statistically reliable [F(1, 39) < 1]. In line with this, separate analyses for comparisons with<br />

large and small unit distances did not reveal <strong>the</strong> expected dissociation: nei<strong>the</strong>r for<br />

comparisons with a large unit distance [F(1, 9) = 1.38, p = .27] nor for comparisons with a<br />

small unit distance [F(1, 29) < 1] a reliable compatibility effect was found. This means that<br />

<strong>the</strong> hybrid model could not account for <strong>the</strong> compatibility effect as observed for comparisons<br />

to a fixed standard. Problem size as incorporated by a covariate did not exhibit a reliable<br />

<strong>influence</strong> in any ANCOVA [F(1, 39) = 1.85, p = .18; large unit distance: F(1, 9) = 3.44, p =<br />

.10; small unit distance: F(1, 29) < 1].<br />

Regression<br />

<strong>The</strong> only reliable predictor incorporated into <strong>the</strong> final regression model for <strong>the</strong> RT data<br />

modelled by <strong>the</strong> hybrid model was overall distance between <strong>the</strong> to-be-compared <strong>number</strong>s [adj.<br />

R 2 = .46, R = .69, F(1, 38) = 37.56, p < .001]. Looking at <strong>the</strong> beta weight showed that reaction<br />

times increased as <strong>the</strong> distance between <strong>the</strong> two <strong>number</strong>s decreased [constant = 533.22; B = -<br />

2.03; b = - .69, t = 6.13, p < .001].<br />

Rerunning <strong>the</strong> regression analysis with incorporation <strong>of</strong> <strong>the</strong> two reliable predictors as<br />

identified by Moeller et al. (2009b) did result in a statistically reliable model without<br />

considerable loss <strong>of</strong> predictive power [adj. R 2 = .42, R = .67, F(2, 41) = 16.39, p < .001].<br />

However, inspection <strong>of</strong> <strong>the</strong> beta weights showed that only <strong>the</strong> <strong>influence</strong> <strong>of</strong> <strong>the</strong> predictor<br />

logarithmic overall distance was significant [constant = 575.50; B = -62.72; b = - .66, t = 5.62,<br />

p < .001] while unit distance did not predict item RT reliably [B = - .43; b = - .11, t = 0.95, p<br />

= .35].<br />

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