This one today was one of the 2010 Optical Illusion Contest finalists. The only reason it didn’t win, was because of spectacular Magnet-Like Slopes that competed at the same time. Anyway, despite its relatively simple nature, the effect it holds is more than entertaining. Here’s what you have to do to understand the illusion: observe the 4 little moving dots. As they move further away one from another (expand – if you wish), and when their path crosses bigger circle’s surface – the ghostly contours appear. It seems as if the smaller dots represented a corners of an expanding and shrinking square. In reality, there are no contours present, and they were only placed here by our brain who struggles to interpret the animation. It is well known that the visual system will often generate illusory contours and surfaces in order to fill-in this missing information. It is widely believed that the visual system does this in order to provide the best overall explanation of the images that form in our eyes.
