Optical Illusions

It is amazing to discover the degree to which our conscious experience of the world can differ from the physical reality. Although some perceptual distortions are only slight deviations from physical reality some can be a quite complex and surprising.
  Such distortions in the form of disagreements between percept and reality are quite common. We call them illusions and they occur in predictable circumstances for normal observers. The term illusion is drawn from Latin root were its meaning is „to mock”. And illusions do mock us for our unthinking reliance on the validity of our sensory impressions Illusions can be found in all the sensory systems though the most of them are related to our vision and are called visual or optical illusions.
Visual illusions are partly based on our cognition. For example the way you look at an object can affect how you see it. Sometimes there are two images in the same picture, but you can only see one at a time so your brain chooses one when it deals with too much information.
Cognitive visual “illusions” rely on stored knowledge about the world (depth, rabbits, human) and are also under some degree of conscious control (we can generally reverse the perception at will). Some of the visual illusions can be divided into three groups:
Ambiguous illusions
Paradox illusions
Distorting illusions.…