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Carrie L Paras, Jill A Yamashita, Maria L Simas, Michael A Webster; Face perception and configural uncertainty in peripheral vision. Journal of Vision 2003;3(9):822. doi: 10.1167/3.9.822.
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© ARVO (1962-2015); The Authors (2016-present)
A face presented in the periphery can appear to change over time (the “multiple face effect,” Simas, Perception, 2000). We explored how this instability varies with retinal eccentricity and its relationship to threshold sensitivity for facial configurations. Observers judged the appearance of a frontal-view face image (approximately 4-deg in width) while fixating at eccentricities ranging from 0 to 32 deg (relative to the midpoint of the face). In one task, the static face image was shown for 4 min and subjects responded whenever it appeared to change. In a second task, a set of 3 faces were shown in succession (for 1 sec each) while observers responded which of the 3 was distorted (by a local expansion). The magnitude of the distortion was varied in a staircase to determine the discrimination threshold. Face images appeared stable for eccentricities up to 2 deg (over which fixation remained at a point on the face), but beyond this the frequency of perceived changes increased monotonically up to 16 deg. This pattern roughly paralleled the increases in configural thresholds with increasing eccentricity, suggesting that the instability reflects spatial uncertainty in the facial configuration. To explore why the changes appear as well-defined faces (rather than simply uncertain) we repeated the face change task for a triplet of Gabor patches (forming an eyes and nose configuration). With peripheral viewing these also changed in appearance over time and appeared more as a face-like configuration than when viewed directly. This suggests that face perception in the periphery may depend on a “perceptual completion” of impoverished and thus labile sensory information.
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