PERCEIVED MOTION OF A COLORED SPOT IN A NOISY ACHROMATIC BACKGROUND

It is shown that human observers can use color both for detecting and for discriminating motion. The contributions of chromaticity and lumin ance to the detection and discrimination of motion are investigated wi th a high-contrast, nonisoluminant stimulus. The motion stimulus is a rectangular 'particle' defined by its luminance and chromaticity, whic h moves against a background containing luminance noise. Although the luminance noise is found to make achromatic particles undetectable ove r a large range of luminances, the addition of color to a particle can render it detectable and also enable accurate speed discriminations t o be made. The contributions of both luminance and chromaticity were m easured. The effect of changing the hue angle of the particle as it mo ves was also examined, and it was found that the detectability of moti on is low in that circumstance.