Bilateral symmetry is a salient object property.
Faces are naturally suitable to address this question, since they are asymmetric in varying degrees but largely symmetric in frontal views. Two images of a synthetic frontal-view face were displayed side by side. The subjects decided which one was more symmetric. This result held for both upright and inverted faces, suggesting that it is not due to a familiarity effect. Nor is the result due to any artifact of the scale of asymmetry in the interpolation dimension.