Fig. 2.

The reaction time results of the number comparison tasks (a and b) and the luminance comparison tasks (c and d). The insets show the hypotheses related to our predictions (see Fig. 1). The inset with the darker silhouette shows the predictions in agreement with the results. The bright bars show the results for stimuli brighter than the background (conditions a, b, and c from Fig. 1), whereas the darker bars show the results for stimuli darker than the background (conditions d, e, and f from Fig. 1). By definition (see the text), C means “congruent” with the best-fitting hypothesis (see insets; i.e., the larger number is darker for the luminance hypothesis, the larger number has the largest unsigned contrast for the contrast hypothesis, etc.), N means “neutral,” and I means “incongruent.” In the number comparison tasks (a, b), the contrast sign manipulation clearly influenced the results, showing opposite congruency effects. This opposite effect was absent in the luminance comparison tasks (c, d), where it is clear that the luminance hypothesis fits our results best. In both the number and luminance comparison tasks, the instruction manipulation did not affect the results; the congruency effects are similar for the larger (a) and darker (b) conditions, when compared with the smaller (b) and brighter (d) instruction conditions, respectively. The error bars present the 95% confidence interval (Loftus & Masson, 1994)