Target/surround asymmetry in perceptual filling-in

Four experiments examined how differences in the properties of the target a nd surround affect the time required for perceptual filling-in. They examin ed differences in luminance, orientation, spatial frequency, and color. A l arger target/surround difference delayed filling-in ('feature difference ef fect'). Interestingly, exchanging the target and surround properties signif icantly varied the time ('target/surround asymmetry'). Filling-in was facil itated when the target was brighter and closer to the vertical or horizonta l than the surround. Little asymmetry was found in the frequency domain, wh ile significant asymmetry was observed for specific color combinations. The se effects are discussed with respect to edge adaptation, feature adaptatio n, balance of neural activities, and contextual modulation. (C) 2001 Elsevi er Science Ltd. All rights reserved.