Gestalt psychology proposes that the whole is greater than the sum of its parts. When elements are placed close together or have similarity, proximity or similarity principles cause us to perceive them as a single, unified whole rather than as separate parts. Continuation principles cause our eyes to follow and connect separate elements in a smooth, continuous line or curve. Closure principles cause us to perceive complete shapes even when elements are incomplete. Figure-ground principles cause us to perceive some elements as foreground figures against a background. Symmetry principles cause us to perceive balanced, symmetrical designs as more ordered and pleasing than asymmetric designs.