-Three main types of Optical Illusion- 1.Literal optical illusions are those illusions that create images that are different from the objects that make them. 2.Physiological illusions are presumed to be the effects on the eyes or brain of excessive stimulation of a specific type 3. Cognitive illusions are assumed to arise by interaction with in-built assumptions or ‘knowledge’ of the world, leading to “unconscious inferences”, an idea first suggested in the 19th century.
