HUMANS and certain other species find symmetrical patterns more attractive than asymmetrical ones. These preferences may appear in response to biological signals(1-3), or in situations where there is no obvious signalling context, such as exploratory behaviour(4,5) and human aesthetic response to pattern(6-8). It has been proposed(9,10) that preferences for symmetry have evolved in animals because the degree of symmetry in signals indicates the signaller’s quality. By contrast, we show here that symmetry preferences may arise as a by-product of the need to recognize objects irrespective of their position and orientation in the visual field. The existence of sensory biases for symmetry may have been exploited independently by natural selection acting on biological signals and by human artistic innovation. This may account for the observed convergence on symmetrical forms in nature and decorative art(11).