Measuring the amplification of attention

An ambiguous motion paradigm, in which the direction of apparent motion is determined by salience (i.e., the extent to which an area is perceived as f igure versus ground), is used to assay the amplification of color by attent ion to color. In the red-green colored gratings used in these experiments, without attention instructions, salience depends on the chromaticity differ ence between colored stripes embedded in the motion sequence and the yellow background. Selective attention to red (or to green) alters the perceived direction of motion and is found to be equivalent to increasing the physica l redness (or greenness) by 25-117%, depending on the observer and color, W hereas attention to a color drastically alters the salience of that color, it leaves color appearance unchanged. A computational model, which embodies separate, parallel pathways for object perception and for salience, accoun ts for 99% of the variance of the experimental data.