What is an optical illusion? An optical illusion is like a “magic picture”. An optical illusion fools your brain into thinkingsomething about a picture that isn’t necessarily true. Tounderstand optical illusions, it is helpful to understand how theeye works.The colored circle on your eye is called the iris. Thesmaller black circle within the iris is called the pupil. The pupillets light into the eye. When you look at an image, light isreflected off the image and through the pupil of your eye to alens behind the iris. The lens projects the image upside downand backwards to the retina in at the back of the eyeball. Theupside down and backwards picture is then carried to yourbrain by nerves in the retina. Once the picture is in your brain, itis turned right side up so it can be seen correctly and so thebrain can understand what you are seeing.An optical illusion is a special picture made to fool theeye. The optical illusion doesn’t make sense, so when thenerves carry the image to the brain the brain has a hard timecomprehending the image. When a person sees an opticalillusion, they often have to look more than once so their braincan understand the image.There are several different types of optical illusions. Infigure A, the side lines make it appear as if the central lines arenot equal in length, when in fact, they are. The side lines leadthe eye either outwardly or inwardly. This is called Muller-Lyerillusion. In figure B, the three concentric circles with bites takenout of them is an example of closure. Even though there is notriangle drawn in this picture, the mind unconsciouslycompletes the triangle that seems to be formed by the bitestaken out of the circles. The Necker Cube, figure C, seems to“flip-flop”, creating the image that the dot is in the front of thecube and then the cube “flip-flops”, and then the dot is in theback of the cube. In the Ponzo illusion, figure ...
