Proximity judgments in color space: Tests of a Euclidean color geometry

Sophie M. Wuerger, Laurence T. Maloney, John Krauskopf

Research output: Contribution to journalArticlepeer-review


We describe two tests of the hypothesis that human judgments of the proximity of colors are consistent with a Euclidean geometry on color matching space. The first test uses proximity judgments to measure the angle between any two intersecting lines in color space. Pairwise estimates of the angles between three lines in a plane were made in order to test the additivity of angles. Three different color proximity tasks were considered. Additivity failed for each of the three proximity tasks. Secondly, we tested a prediction concerning the growth of the variability of judgments of similarity with the distance between the test and reference stimuli. The Euclidean hypothesis was also rejected by this test. The results concerning the growth of variability are consistent with the assumption that observers use a city-block metric when judging the proximity of colored lights.

Original languageEnglish (US)
Pages (from-to)827-835
Number of pages9
JournalVision research
Issue number6
StatePublished - Mar 1995


  • Color geometry
  • Color similarity
  • Euclidean geometry
  • Salience of colors

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems


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