Distant background information strongly affects lightness perception in dynamic displays.

Lightness perception is strongly dependent on context, including the relative luminance of the adjacent surfaces, spatial configuration, and luminance contrast. The latter, local luminance contrast, is thought to be processed in relatively early stages of visual processing and has been shown to play a crucial role in lightness perception. However, more global processing, such as perceptual grouping of surfaces, can also have an effect on lightness perception. An unresolved question, which we will address in this paper, is how global and local processes interact. We used a static gray disk embedded in a temporally modulated in luminance ring, which gives rise to a lightness effect dependent on local luminance contrast. We manipulated global image information by presenting the stimulus on backgrounds of different luminances. Surprisingly, the induction effect was greatly attenuated at a background luminance equal to that of the disk. We show that this finding cannot be explained by common lightness induction models. However, it is consistent with an effect of grouping on lightness perception and demonstrates how processes that are dependent on local edge information can be overridden by global image information.