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Tanner DeLawyer, Steven Buck; Indirect and direct manipulation of saturation modulates the light levels at which brown stimuli can be perceived . Journal of Vision 2014;14(10):87. doi: https://doi.org/10.1167/14.10.87.
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© ARVO (1962-2015); The Authors (2016-present)
Stimuli that appear yellow when brighter than their surroundings will appear brown when they are darker than their surroundings. Past research (Bartleson 1976) has suggested that desaturated stimuli produce more effective browns than those that are fully saturated. The perceived saturation of brown stimuli can be manipulated both indirectly (by changing the size and location of the stimulus) and directly (by changing the amount of blue present in a brown stimulus). We sought to test the effect of stimulus saturation on the perception of brown stimuli quantitatively by varying, both indirectly and directly, the saturation of a test stimulus. Observers freely adjusted the luminance of a constant-chromaticity, 2°-7°-diameter saturated (CIE 10° x=.44, y=.46) or desaturated (CIE 10° x=.36, y=.36) disk, presented with a bright white surround (141 cd/m2, CIE 10° x,y .29,.29) on a CRT monitor. The disk stimulus was presented either at the fovea or at 7° eccentricity of a foveal fixation point. The observers adjusted the luminance until they reached the highest light level at which the stimulus appeared exclusively brown. Thus, the stimulus appeared brown at luminances lower than the boundary and appeared yellow at luminances higher than the boundary. For both foveal and 7° eccentricity conditions, smaller disks allowed the subject to perceive brown at significantly higher light levels than larger disks. Additionally, stimuli presented extra-foveally and desaturated stimuli facilitated perception of brown at significantly higher light levels than foveal stimuli and saturated stimuli. Smaller and eccentric test stimuli are more effective at producing brown than larger or foveal stimuli as are desaturated stimuli. Past research has shown both small stimuli and extra-foveal stimuli are perceived as less saturated than large or foveal stimuli (McKeefry et al. 2007) suggesting all these effects can all be attributed to perceived saturation. Potential nerual mechanisms are under investigation.
Meeting abstract presented at VSS 2014
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