title: Influence of stimulus size on revealing non-cardinal color mechanisms.
abstract: Multiple studies have shown that performance of subjects on a number of visual tasks is worse for non-cardinal than cardinal colors, especially in the red-green/luminance (RG/LUM) and tritan/luminance (TRIT/LUM) color planes. Inspired by neurophysiological evidence that suppressive surround input to receptive fields is particularly sensitive to luminance, we hypothesized that non-cardinal mechanisms in the RG/LUM and TRIT/LUM planes would be more sensitive to stimulus size than are isoluminant non-cardinal mechanisms. In Experiment 1 we tested 9-10 color-normal subjects in each of the three color planes (RG/TRIT, RG/LUM, and TRIT/LUM) on visual search at four bull's-eye dot sizes (0.5°/1°, 1°/2°, 2°/4°, and 3°/6° center/annulus dot diameter). This study yielded a significant main effect of dot size in each of the three color planes. In Experiment 2 we tested the same hypothesis using noise masking, at three stimulus sizes (3°, 6° and 9° diameter Gabors), again in all three color planes (5 subjects per color plane). This experiment yielded, in the RG/TRIT plane, a significant main effect of stimulus size; in the RG/LUM plane, significant evidence for non-cardinal mechanisms only for the 9° stimulus; but in the TRIT/LUM plane no evidence for non-cardinal mechanisms at any stimulus size. These results suggest that non-cardinal mechanisms, particularly in the RG/LUM color plane, are more sensitive to stimulus size than are non-cardinals in the RG/TRIT plane, supporting our hypothesis.
authors.affiliation: Department of Psychology, Wabash College, 301 West Wabash Avenue, Crawfordsville, IN 47933, USA. Electronic address: guntherk@wabash.edu.
authors.forename: Karen L
authors.initials: KL
authors.lastname: Gunther
authors.affiliation: Department of Psychology, Wabash College, 301 West Wabash Avenue, Crawfordsville, IN 47933, USA.
authors.forename: Colin O
authors.initials: CO
authors.lastname: Downey
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D003118:Color Perception / Q000502:physiology*; D015350:Contrast Sensitivity / Q000502:physiology; D005260:Female; D006801:Humans; D008029:Lighting; D008297:Male; D010470:Perceptual Masking / Q000502:physiology; D010775:Photic Stimulation / Q000379:methods; D012684:Sensory Thresholds; D012858:Size Perception / Q000502:physiology*; D055815:Young Adult
keywords: Color space; Non-cardinal color; Stimulus size