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Perceptual Illusions

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Saved by Pooja Patel
on November 25, 2012 at 8:47:25 pm
 

 

PERCEPTUAL ILLUSIONS

One of the most popular illusions in psychology is Ebbinghaus' Tichtener Circles: Which center circle is bigger, the one on the right or the one on the left?


 

         The dictionary definition of a perceptual illusion is, "the perception of something objectively existing in such a way as to cause misinterpretation of its actual nature." While this is true, it is not the only definition of an illusion. An illusion is not always a misinterpretation, but rather it convinces us that the real life version of an object is untrue or false. One important factor to remember is that no two different interpretations of an object of picture can be given at one moment. Besides sensory illusions, there are three types of optical illusions we study: literal, physiological, and cognitive.

          A literal illusion is an image created by smaller images that are in no way related to the larger, overall image created. This is the simplest type of optical illusion which is why it is often the least studied in psychology. Here is an example of a literal illusion: The smaller images (sailboats) make up the underlying, larger image (the bridge).

                                             

          A physiological illusion can occur after prolonged visual stimulation. An afterimage, for example, is a physiological illusion. According to theorists, a viewer's perception may be changed as a result of a physiological imbalance. This imbalance is usually caused by over-active or over-stimulated nerve paths caused by competition between the light and dark receptors in the retina. This competition is essentially what leads to the physiological imbalance. Here is an example of a physiological illusion: Stare at the four black dots in the middle of the image below for thirty seconds, and then look away to a blank (preferably white) wall, and an after-image should appear. What do you see?

                                                        

          A cognitive illusion 

         We have sensory receptors in our brain that detect light, sound, temperature, etc., and most of these receptors are on the surface of our bodies (i.e. eyes, ears, mouth, etc.). There are, however, internal receptors such as those that register pain. Regardless of the type, each receptor is responsible for detecting its own form of energy which is used to transmit signals to the brain. When the brain receives these signals, most of the time it interprets the signals correctly, but when it doesn't, that is what we call a sensory illusion.

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