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Carrie L. Paras, Daniel Kaping, Michael A. Webster; Adaptation and the perception of facial symmetry. Journal of Vision 2004;4(8):440. doi: https://doi.org/10.1167/4.8.440.
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Symmetry is an important dimension of facial configuration. We examined how the perception of symmetry is affected by prior adaptation to faces. Stimuli were frontal-view images of faces presented on a monitor. Observers adjusted the distortions in test faces varied with a 2AFC staircase until they appeared normal or symmetric, after adapting for 2 min to a face that was distorted or asymmetric. In one set of experiments, we measured perceived configuration after adaptation to asymmetric distortions (e.g. expansions or contractions on one side of the face or along oblique axes). These induced large negative aftereffects in the appearance of the original face, comparable to the effects found for symmetric distortions. In a second task, we asked whether the asymmetries that occur in actual faces are large enough to induce adaptation. Stimuli in this case were morphs between a face image and its mirror image. Prior adaptation to the mirror image causes the original face to appear highly asymmetric, and we use the nulling staircase to quantify the shift in the image within the morph series that appears most symmetric. In the final task, we measured the effects of adaptation to distortions in a half-face image on the appearance of the same or complementary half image. This adaptation showed partial transfer to the complementary half, suggesting either some degree of positional invariance and/or perceptual completion of the face. However, these aftereffects were not clearly different for half faces split along the vertical or horizontal midline. These results suggest that facial asymmetries are a configural property that can be strongly influenced and perhaps normalized by adaptation, but do not point to a privileged role of the axis of symmetry for the adaptation. Supported by EY-10834
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