Visual illusions

• Size constancy

  When we look down from a great height, such as the top of the building or the window of a plane, the people on the ground look like ants. Our brains know they aren't really ant size they are just far away. This is size constancy. Our brain perceives object and people are being of a constant size even though the size of the image they produce on our retina our changes with distance.
• Misinterpreted depth cues

  Depth queues that help us perceive distance. Once we have worked out (using depth cues) that something is far away. Our brain uses the rule of size constancy. Things in the distance which appears smaller than they should be are scaled up by our brain to make them look normal size. However, sometimes our brain perceives distance when it's not actually there. Some illusions like the Ponzo illusion, fool the brain into perceiving distance and we apply the rule of size constancy when it should not be used. In other words we misinterpret the depth cute.
• Ambiguity

  Not all types of illusion are distortion illusions such as the Ponzo illusion and Muller Lyer illusion. There are other types of illusions that trick the brain for quite different reasons. An ambiguous figure is when there are 2 possible interpretations of the same image and the brain can decides which one it chooses. Ambiguity means something is unclear or could have more than one meaning. Visual illusions that use ambiguity include the Necker cube, Rubin's vase and the duck rabbit.
• Fiction

  Fiction refers to a visual illusion when the person starts to perceive something in the image is not actually there. The image or stimulus may suggest a certain aspect of a figure is present whether in reality it exists or not. An example of this is the Kanizsa triangle.