The Phenomenology of Attention. 2. Brightness and Contrast

The effect of attention on perceived brightness and contrast was investigated in eight experiments. Attention was manipulated by engaging observers in an attention-demanding concurrent task (letter detection) or by directing attention to a location with a peripheral cue. In all of the dual-task manipulations, attention reduced the variability of responses. However, attention did not affect the brightness of stimuli, nor did it affect the amount of simultaneous brightness contrast. Results with peripheral location cues were similar; however, the effect of attention in these experiments could be attributed to nonperceptual factors. The metaphorical "spotlight" of attention reduces observers' uncertainty about the brightness of a stimulus, but it does not "illuminate" in terms of brightness or contrast.