The Ebbinghaus illusion or Tichener circles is an optical illusion of relative size perception and it’s been created for the experimental psychology, showing us the importance in the existence of separate pathways in the brain for perception and action.
What to see?
You can see two images showing a circle in the middle surrounded by other circles. You will easily notice that some of these circles are bigger and some are smaller. But what about the one in the middle? If the circles surrounding the middle one are enlarged then it will look smaller and if they are decreased the middle circle will seem bigger.
For the same illusion there is another explanation. Another factor is the distance between the middle circle and the surrounding ones. If the surrounding circles are near to the central circle it appears larger, while if they are far away it appears smaller. This kind of illusion has shown the way the brain perceives and acts in different means.
How does it work?
This illusion if we may call it like this is actually the basis for an experiment. This Titchener Circles illusion was used in a study to investigate the functional dissociation of the dorsal visual-motor and ventral perceptual system. For this to be possible the scientist used two-dimensional and three-dimensional targets. It was discovered that even if the depth is important for the dorsal visual-motor system it’s not necessary