How the brain works: Illusions

An optical illusion (also called a visual illusion ) is characterized by visually perceived images that differ from objective reality. Information gathered by the eye is processed by the brain to give a precept that does not tally with a physical measurement of the stimulus source. There are three main types of illusion - literal optical illusions that create images that are different from the objects that make them, physiological illusions that are the effects on the eyes and brain of excessive stimulation of a specific type - movement, brightness, color, tilt, and cognitive illusions where the eye and brain make unconscious inferences.