Automatic spatial association for luminance.

In the present study, we investigated whether luminance and the side of response execution are associated, showing a SNARC-like effect (faster responses with the left hand for dark stimuli, and vice versa for light stimuli). A total of 30 participants were tested in two experiments. In Experiment 1, the association between space and the luminance of chromatic stimuli was directly tested (brightness discrimination). In Experiment 2, the same spatial association was tested indirectly (hue discrimination). The results showed that participants responded faster with their left hand to hues with lower luminance, and with their right hand to hues with higher luminance, in either the direct or the indirect task. The consistency of this association in both tasks demonstrates the automaticity of the SNARC-like effect for luminance.