Abstract
Nagy & Cone (Vision Research, 1996) report the asymmetry that search for a more saturated target among less saturated distractors is easier than search for a less saturated target among more saturated distractors. The Saliency Model (Rosenholtz, Perception & Psychophysics, 2001) predicts that this asymmetry is due to the background color of the display relative to the target-distractor colors, and that appropriately changing the background color should reverse the color search asymmetry.
Observers searched for a known target among homogeneous distractors. The stimuli consisted of 0.14 deg. diameter disks at random locations within a 4.25 deg. diameter area. We measured the time for an observer to depress a response button indicating that they had determined whether a target was present. Seven equiluminant target-distractor pairs were used, ranging from unsaturated white to saturated red, with each member of a pair serving as target and distractor in different blocks of trials. Each pair was presentedon both achromatic and red backgrounds of a lower luminance.
With an achromatic background, reaction times were shorter when the target was more saturated than the distractors. When the same stimuli appeared on a red background, the asymmetry reversed. On both
Both the direction and magnitude of a color search asymmetry depend upon the background color. Several models qualitatively predicts these results, including both the Saliency Model and a signal detection theory model in which the viewer observes the color difference between each element and the background, with noise proportional to the magnitude of the difference.
Supported in part by NEI EY12528.