filling in

In vision, filling-in phenomena are those responsible for the completion of missing information across the physiological blind spot, and across natural and artificial scotomata. There is evidence calling for similar mechanisms of completion also in normal visual analysis. Classical demonstrations of perceptual filling-in involve images stabilized on the retina either by means of special lenses, or under certain conditions of steady fixation. If a stimulus is entirely stabilized, its colour and lightness fade until they are no longer seen and the area fills in with the colour and lightness of the surrounding region. A famous example of fading under steady fixation is the Troxler's fading. When steadily fixating the central dot for many seconds, the peripheral annulus will fade and will be replaced by the colour or texture of the background. Since the adapted region is actively filled-in with background colour or texture, the phenomenon cannot be fully explained by local processes such as adaptation.
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