Convex hull test of the linear separability hypothesis in visual search

Area of Science:

• Visual perception
• Color science
• Human vision

Background:

• Visual search for a target color among distractors is significantly influenced by the spatial arrangement of colors in CIE (x, y) space.
• Previous research indicated search difficulty when a target's chromaticity is not linearly separable from two distractor chromaticities.

Purpose of the Study:

• To investigate if the linear separability effect in visual search extends beyond the two-distractor case.
• To examine how target color placement relative to a set of distractors impacts search performance.

Main Methods:

• Conducted visual search experiments with varying numbers of distractor colors.
• Analyzed search performance based on whether the target color was inside or outside the convex hull defined by distractor colors.
• Varied stimuli to include chromaticity alone and combined luminance-chromaticity conditions.

Main Results:

• Search performance was hindered when the target color was placed inside the convex hull of the distractor colors.
• This effect persisted regardless of whether linear separability was based on chromaticity alone or a combination of luminance and chromaticity.
• Placing the target outside the convex hull generally facilitated easier search.

Conclusions:

• The linear separability effect in visual search is not limited to two distractors and applies to more complex color configurations.
• The spatial relationship of a target color to the set of distractor colors, defined by a convex hull, is a critical factor in visual search efficiency.
• Findings have implications for understanding color perception and designing visual displays.