r cognitive abilities can not influence your perceptions. For any given retinal image, there is an infinite variety of possible three-dimensional structures that can lead to it. Our visual system, however, usually settles for the correct interpretation (Introduction to Perception [Online]). It is when a mistake is made in the interpretation that an illusion occurs. Perceptual illusions are anything that may seem to cause something to become perceptually confusing. These illusions have a distinct manner of confusing our normal perceptual processes. The Muller-Lyer Illusion and the Ponzo Illusion may be the two most commonly studied perceptual illusions in psychology. Stephen R. Jackson states in his Feb. 2000 article in Journal of Experimental Psychology that appropriate indications such as linear perspective and relative size can exert a powerful effect on the perception of objects. The illusory effects such as those of the Muller-Lyer and Ponzo illusions demonstrate this fact (Jackson 2000).In the Muller-Lyer Illusion (fig. 1), there are two objects, both having one line and two lined triangles at their ends. When the objects are placed parallel to each other, the line from the top object looks longer than the line from the lower object. Why does it appear to be longer when the two are actually the same length? This has to do with the direction of the two triangles or arrows at the end of the lines. On the lower figure, the open ends of the triangles are facing inward, causing the line to appear shorter than it is. And on the upper figure, the open ends of the triangles are facing outward, causing the line to appear longer than it actually is (Online. Retrieved on October 11, 2000 at http://www.epsychlopedia.net/concepts/sensationAndPerception/index.php?id=sensandperc8).The Ponzo Illusion (fig 2) has four lines. There are two horizontal lines parallel to each other and two diagonal lines approaching each other on either s...
