An
optical illusion (also called a
visual illusion) is characterized by
visually perceived images that differ from objective reality. The information gathered by the eye is processed in the brain to give a
perception that does not tally with a physical measurement of the stimulus source. There are three main types: literal optical illusions that create images that are different from the objects that make them, physiological illusions that are the effects of excessive stimulation of a specific type (brightness, colour, size, position, tilt, movement), and
cognitive illusions, the result of
unconscious inferences. Pathological visual illusions arise from a pathological exaggeration in physiological
visual perception mechanisms causing the aforementioned types of illusions.
