Optical Illusions

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  • Topic: Optical illusion, Illusion, Perception
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  • Published : February 5, 2013
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Rachel Hahn
Cheryl Blackwell
Seminar
November 2012
Optical Illusions
An illusion is the distorted perception of a stimulus. They are not to be confused with hallucinations, which are false perceptions when there is no presence of a stimulus, in contrast, illusions are the misinterpretation of a true sensation (Illusion Wikipedia). Illusions are mundane phenomena, and are experienced by nearly everyone in similar ways where hallucinations are a personal experience and are typically limited to people who are mentally ill or under the influence of certain drugs (Hallucination Wikipedia). Some illusions occur automatically because it is in our biological nature to perceive things in a particular way, for example objects that are farther away appear smaller than closer objects. Other illusions can be shown by displaying certain visual tricks that we know will cause an illusion because we have knowledge of how our bodies interpret stimuli (Illusion Wikipedia). Illusions give us an understanding as to how our brain organizes and translates stimuli. They help explain and support the Laws of Perceptual Organization defined in Gestalt Psychology. These laws explain how we visualize the world around us and will later be talked about in more detail (Gleitman, Gross and Reisberg). There are more illusions than just optical; they can occur with all of your senses such at auditory illusions (sound) and tactile illusions (touch) (Illusion Wikipedia). Optical illusions are however the most notorious and understood; there are various different kinds of optical illusions and in my research I looked closely at the boundary extension illusion, the moon illusion, motion illusion, and autokinetic illusions, which are all optical illusions. I also researched many supported theories and explanations of why illusions occur.

We do not just “receive” visual information, we interpret it. The interpretation is an essential part of our perception and aids us in perceiving the world around us correctly. The role of interpretation becomes especially clear when we misinterpret the information that is around us and end up misperceiving the world (Gleitman, Gross and Reisberg).Gestalt Psychology, which is the idea that when we see things we have the biological tendency to organize them into certain ways that make sense to us, is a very good explanation of why we see some optical illusions. There are six fundamental principles in Gestalt Psychology that explain how we visually organize things. The first principle is similarity, this is the idea that we group together objects that are similar to one another. Figure 1.1 demonstrates similarity, because we group the circles together and the squares together we see a “t” made of squares rather than seeing the picture as columns or rows. The second principle is proximity, it explains that when objects are close together we tend to pair them apart and when they are separated we see them individually. Because of the principle of proximity when you look at figure 1.2 you will see one big square rather than nine individual squares, but if these squares were separated we would see them exclusively. The third principle is good continuation, it is the notion that we are apt to see contours continue smoothly along their original course (Gleitman, Gross and Reisberg). Figure 1.3 exhibits good continuation because instead of seeing four lines meeting in the middle we see two crossed lines. The fourth Gestalt principle is closure; we perceive contours that don’t actually exist. When figures have gaps we illusively close those gaps by perceiving that the contours continue along their original path. In figure 1.4 we form a panda bear even though there are no actual contours that physically exist making a panda. The fifth principle is simplicity, stating that we translate images into our mind in the simplest way possible. In figure 1.5 you see two rectangles that are crossed instead of seeing a single 12-sided...
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