Explicit and Implicit Preference for Symmetry Across Object Categories

Symmetry affects aesthetic judgements, and it has been extensively studied at least for faces and abstract objects. We examined the role of bilateral symmetry on aesthetic judgements across different types of stimuli. It is important to test if symmetry is equally effective in the context of objects expected to be symmetrical, e.g., faces, and objects that are almost never symmetrical, e.g., landscapes. We used the following categories: angular shapes, smooth shapes, landscapes, flowers, female faces, and male faces. We selected these image categories considering their differing degrees of curvature, familiarity to the viewer, and tendency to be perceived as ensembles, as opposed to standalone objects. We also included blobs, manipulating landscapes into blurry tessellated patterns featuring patches of color, to remove familiarity while preserving the appearance of ensembles. For each item in these categories, images were modified to obtain perfect bilateral symmetry. We collected both explicit ratings and implicit measures of symmetry preference. For landscapes, there was a clear preference for the non-symmetrical (original) version. We observed a dissociation between explicit and implicit measures. Implicit measures demonstrated positive associations for all categories.