Through a series of precise experimental manipulations of perception in human subjects, Farshad Moradi and his colleagues have gained new insight into the process. They have found that identifying a face depends on actually seeing it, as opposed to merely having the image of the face fall on the retina.

In one set of experiments, the researchers took advantage of a phenomenon called "binocular rivalry" to present face images to subjects in circumstances under which the retinal input would remain perceptually invisible.

In such binocular rivalry experiments, a different image is presented simultaneously to each eye. Since the visual system can only pay attention to one image at a time, the other remains "invisible"--suppressed from visual awareness. The researchers found that in such experiments the recognition of the face depended on actually perceiving it. In contrast, they found, such lower-level "aftereffects" as recognizing the orientation of the face were not affected by lack of visual awareness.

"Thus, the competition between incompatible or interfering visual inputs to reach awareness is resolved before those aspects of information that are exploited in face identification are processed," wrote the researchers.

In further experiments, they also explored whether face recognition was affected by suppressing awareness of the face image with distracting tasks such as memorizing images or sounds--a phenomenon called "inattentional blindness." The researchers found that the requirement to pay attention to visual distractors, but not auditory distractors, eliminated the face recognition. Thus, they found, since auditory distractors didn't reduce face recognition, such recognition is not affected by
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Contact: Heidi Hardman
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Cell Press
5-Jan-2005