“Filling-in” colour in natural scenes

Our subjective experience of the world as being in full colour across the entire visual field is at odds with the highly fovea-biased distribution of cones in the retina. It is unclear how this percept of “pan-field colour” comes about. We use novel stimuli—“colour chimeras”—to demonstrate a related visual phenomenon in which observers perceive rich colour throughout images with large achromatic regions. This percept appears to critically depend on natural scene statistics. By separately manipulating chromatic and structural content in such images, we demonstrate that both the spatial distribution of colour and the presence of recognizable scene structure contribute to the experience of pan-field colour in these stimuli. Our results suggest that this percept is unlikely to be due to a low-level colour spreading process. Instead, we suggest that mechanisms dependent on natural scenes’ chromatic and luminance statistics provide the basis for the phenomenon.