bilgerat
Senior
This illusion, created by the artist Victoria Skye, was one of the top entries in the 2017 Best Illusion of the Year Contest. Believe it or not, the horizontal lines are all perfectly parallel. To prove this to yourself, just squint at the image or look at it from the side. Victoria Skye builds on the previous insights of the famous illusionists Richard Gregory and Akiyoshi Kitaoka, to show that or perception of rectilinear lines is a matter of opinion. You determine whether edges are parallel through a brain circuit that uses the lightness and darkness of edges to help establish the relative orientation of the lines. Presumably this is because your brain relies a lot on shadows to see where objects lie, and how they interact with the surfaces around them. So here, when Skye throws in a series of white/black diamonds at key transitions between surfaces, this causes havoc in the brain circuits, leading to misrepresentation—in perception—of the position and angles of the edges. 
