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Why do we see illusions? - Mark Changizi


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Why can’t our extremely complex eyes render simple optical illusions? Surprise, surprise -- it comes back to the brain, which has only evolved to encounter natural stimuli. At TEDYouth 2012, Mark Changizi explains how the brain reckons with optical illusions.

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Mark Changizi is a theoretical neurobiologist aiming to grasp the ultimate foundations underlying why we think, feel, and see as we do. His research focuses on "why" questions, and he has made important discoveries such as why we see in color, why we see illusions, why we have forward-facing eyes, why the brain is structured as it is, why animals have as many limbs and fingers as they do, why the dictionary is organized as it is, why fingers get pruney when wet, and how we acquired writing, language, and music.Silencing is a new illusion that shows it's hard to notice when moving objects change. Silencing demonstrates the tight coupling of motion and object appearance. Simply by changing the retinotopic coordinates—moving the object or the eyes—it is possible to silence awareness of visual change, causing objects that had once been obviously dynamic suddenly to appear static.Since ancient times, humans have known that immediate perception is not a reading of physical reality. Vision is the most creative act that a human being is capable of. Seeing is depicting the world on the living canvas of our mind. As we depict well only what we really know, our mind is both the canvas and the artist. In this creative process, the eyes represent nothing other than a medium with which our mind interprets and reconstructs our near environment. Some illusions teach us to doubt and to question the many appearances of the reality - they are a kind of school of life!An optical illusion (also called a visual illusion) is characterized by visually perceived images that differ from objective reality. The information gathered by the eye is processed in the brain to give a perception that does not tally with a physical measurement of the stimulus source. There are three main types: literal optical illusions that create images that are different from the objects that make them, physiological ones that are the effects on the eyes and brain of excessive stimulation of a specific type (brightness, colour, size, position, tilt, movement), and cognitive illusions, the result of unconscious inferences.Here's a collection of some of the most popular optical illusions on the internet.

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