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

compatibility effect for large unit distances [16 ms, F(1, 11) = 13.07, p < .01, see Figure 1],
while there was no significant compatibility effect for small unit distances [7 ms, F(1, 27) =
2.34, p = .14], suggesting particular influence of large unit-distances.
Regression: The regression analysis on mean RT corroborated the ANCOVA results.
The multiple correlation was highly predictive (R = .717, adjusted R 2 = .488, p < .001) by
incorporating only two significant predictors: Response latencies became faster with
increasing distance between the logarithms of standard and probe (β = - .599) and increasing
(compatible) unit distance (β = - .413). As unit distance ranges from -6 in incompatible to +6
in compatible trials this result indexed that the compatibility effect is not categorical, but
increases as incompatible unit distance increases. Note that within-decade probes could not be
included in the regression analyses as the (positive or negative) unit distance is defined with
regard to the compatibility of the decade digits’ comparison, for which the decade digits have
to be different.
Figure 1: Means of response latencies for the respective stimulus groups.
Error bars indicate the standard error of the mean (SEM).
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