Rudd M E, 2010, "Spatial attention, illumination frameworks, and grouping by surround similarity in lightness perception" Perception 39 ECVP Abstract Supplement, page 168
Spatial attention, illumination frameworks, and grouping by surround similarity in lightness perception
M E Rudd
Arend and Spehar (1993) showed that lightness matches made with simple displays such as disk-and-ring stimuli are influenced by instructions to imagine the target and matching configurations as belonging to either a single global illumination framework or separate local frameworks. Here I discuss a new lightness grouping effect that occurs only when the subject attends to the global illumination framework [Rudd, 2008 Journal of Vision 8(6):287, 287a]. The likelihood that a subject’s lightness matches will be based on a luminance comparison between the target and its local surround depends on the luminance similarity between the target and match surrounds. This ‘surround similarity effect’ produces lightness assimilation and contrast over different ranges of the target surround luminance. When the subject views the target and matching configurations as belonging to separate local frameworks, the surround similarity effect and assimilation disappear. Thus grouping by surround similarity explains assimilation. The global and local attention results each conform to a simple set of mathematical rules motivated by ecological considerations. Naïve (ie uninstructed) matches are modeled as a mixture of the matches predicted from models based on local edge analysis and global luminance cues. Errors in lightness constancy are explained in terms of a compromise between reliance on the local versus global cues.
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