Perceptual selectivity and the fate of unemphasized information in a stimulus complex.

The potential role of selectivity in visual perception was investigated for stimuli containing multiple components. Primary interest centered on the role of prior emphasis on the perceptual processing of one component, relative to the perceptual fate of the remaining components in the stimulus, and whether unemphasized components fared less well than those same components on an uninstructed trial. On each trial, a face, scrambled face, or single-component stimulus was briefly presented, followed by a patterned mask and a forced choice test of each of the components teye, nose, mouth). On a cued trial, the subject was instructed to emphasize one component, although all three components were subsequently tested; on an uncued trial, no prior instructions were given. The results indicated that identification of an emphasized stimulus component was enhanced, but only at the detriment of the remaining components; that is, components were perceived more accurately on an uncued trial than unemphasized components on a cued trial. Although face and scrambled face stimuli were perceived unequally, the effectiveness of prior instructions was equivalent. Surprisingly, the overall identifiability of the components within a stimulus was independent of prior instructions, and suggested that a finite capacity is available for perceptual analysis.