Target/surround asymmetry in perceptual filling-in.

Four experiments examined how differences in the properties of the target and surround affect the time required for perceptual filling-in. They examined differences in luminance, orientation, spatial frequency, and color. A larger target/surround difference delayed filling-in ('feature difference effect'). Interestingly, exchanging the target and surround properties significantly varied the time ('target/surround asymmetry'). Filling-in was facilitated when the target was brighter and closer to the vertical or horizontal than the surround. Little asymmetry was found in the frequency domain, while significant asymmetry was observed for specific color combinations. These effects are discussed with respect to edge adaptation, feature adaptation, balance of neural activities, and contextual modulation.