Using color to code quantity in spatial displays

Participants made simple and complex judgments in 2 experiments that examin ed the use of color to code quantity in spatial displays. The coding assign ments were chosen to evaluate the principle of perceptual linearity in colo r space. In Experiment 1, participants compared all possible pairs of color s used to represent magnitudes. Comparisons were made most rapidly with a s cale that varied only brightness (B) and most accurately with a scale that covaried hue (H) with saturation (S) and brightness (H+S+B scale). In Exper iment 2, clusters were identified fastest with the H+S+B scale, followed by brightness and bipolar scales, whereas a nonlinear, hue-only scale was slo west and produced the least accurate judgments. Coding assignments close to perceptual linearity were best for both simple and complex judgments in da ta visualization. However, hue conferred an advantage if the task involved segregation or classification.