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Frederick Bonato, Joseph Cataliotti; Pictorial and stereoscopic grouping effects on the luminosity threshold. Journal of Vision 2002;2(7):550. doi: 10.1167/2.7.550.
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© ARVO (1962-2015); The Authors (2016-present)
The perception of self-luminous surfaces—that is, surfaces that appear to glow, has seldom been researched. Work in our lab has shown that luminosity perception, like lightness perception, is mediated by perceptual grouping processes that must be cortical in nature. For example, grouping by similarity plays a role. A target that differs in shape from other elements in an array exhibits a lower luminosity threshold than an identical target that shares a similar shape with background elements (Bonato & Cataliotti, 2001). In the current study observers adjusted the luminance of a target until it began to appear self-luminous (luminosity threshold). In one experiment, grouping by similarity was manipulated by embedding a sharp edged target in a Mondrian display whose regions were either sharp-edged or blurred. Results were consistent with our previous research: the target embedded in the blurred Mondrian resulted in the lowest luminosity threshold. However, in another experiment in which the target's perceived location in space was manipulated stereoscopically, the target that appeared to be in front of its background exhibited the highest threshold—a result inconsistent with our earlier work. Collectively, these results suggest that grouping processes affect the luminosity threshold differently in 2-D and 3-D displays. Further experimentation has supported this hypothesis leading us to the following conclusions: 1) in 2-D displays, regions that do not group well with their array result in lower luminosity thresholds, and 2) in 3-D stereoscopic displays, regions that appear isolated in space in front of their array tend to form a separate perceptual framework, resulting in higher luminosity thresholds. Results will be discussed in the context of lightness anchoring and perceived illumination level.
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