Certain patterns of stripes are judged to be unpleasant to look at. They induce illusions of colour, shape and motion that are sometimes perceived predominantly to one side of fixation. People who suffer frequent headaches tend to report more illusions, and if the pain consistently occurs on the same side of the head the illusions tend to be lateralized. The parameters of the patterns that induce illusions (including their shape, spatial frequency, duty cycle, contrast and cortical representation) closely resemble those that elicit epileptiform electroencephalographic abnormalities in patients with photosensitive epilepsy. The viewing conditions under which such abnormalities are likely to appear are also those under which more illusions are seen.
Some op-art artists create works that evoke shimmering illusions, such as work by Debbie Ayles, and Bridget Riley. Op-art has been studied by researchers in order to investigate the causes of these illusory effects. In particular, Leviant’s illusion ‘Enigma’, has been the centre of scientific debate. There are two types of illusory movement arising from this artwork: circular motion from the rings and shimmering illusions from the radial lines. It has been argued that the shimmering illusion is due to fluctuations in accommodation, the focussing response of the eye. It was also suggested that very small eye movements called microsaccades have an important role to play in the perception of shimmering. Empirical evidence has been found to support this claim in the case of the Enigma illusion, as well as other illusions of motion based on geometric patternsShow less
Motion illusions in Optical Art presented for long durations are temporally distorted Leave a comment
Optical Art (or Op Art) generates specific perceptual responses, having dynamic qualities
which provoke illusions and sensations in the viewer (Rycroft 2005). Some paintings of this
artistic movement use perspective illusions or chromatic tensions that lead to the perception
of a flicker or movement in simple geometrical patterns (Martinez-Conde and Macknik 2010;
Illusion continues to be a major theme in the book, which provides a comprehensive classification system. There are also sections on what babies see and how they learn to see, on motion perception, the relationship between vision and consciousness, and on the impact of new brain imaging techniques.