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Illusory Contours

Page history last edited by Frances Shaffell 6 years, 8 months ago








     Illusory contours are edges that are not physically present in a stimulus but are perceived when one views the stimulus.The first illusory contour was depicted by a researcher named Schumann in 1900. He noted that a central "white rectangle with sharply defined contours appears, which objectively are not there." Research on illusory contours did not really begin to progress again until over fifty years later when "Kanizsa's Square" came into the picture in 1955. Most of these stimuli use what are called nonaligned inducers (also referred to as "pacmen") to give the illusion of edges that are not present. These nonaligned inducers do not present perceptual contours, they simply imply that perceptual contours were once present. The "Kanizsa Square" image uses four "pacmen inducers" placed with the openings facing inward to give the illusion of a missing square. Many studies have been performed to test which areas of the brain respond to the stimuli and, more exclusively, to the illusory contours in the stimuli. One of these studies used an fMRI (or functional magnetic resonating image) to give the researchers a better look inside the brain to find out which portions of the brain register the image and react to the "missing picture". All of the test subjects showed a predominate activation in the right hemisphere of their brains. Another study tested whether or not the brightness of the inducers has anything to do with how quickly one reacts to the illusory contour in a stimulus. The researchers found that reaction rates are approximately the same whether the inducers are bright in contrast to the background or are simply a few shades lighter.











1. http://www.pnas.org/content/92/14/6469.full.pdf

     - This link provides an article with information about the fMRI study on the activated areas of the brain during the presentation of illusory contour stimuli.


2. http://www.sciencedirect.com/science/article/pii/0042698996000624

     - This link is to an article that describes multiple experiments performed with illusory contours and the accuracy with which a subject can discriminate between the physically present stimuli and the illusory contours.


3. http://www.cns.nyu.edu/~shapley/Publications/rubin-naka-shap96.pdf

     - Follow this link for an article on a study which determines the perception of illusory contours by the brain.


4. http://journals.cambridge.org/action/displayAbstract;jsessionid=793B79F71961F9A6709C61EE708FEE04.journals?fromPage=online&aid=4616232

     - This link takes one to an abstract on an article that discusses top-down and bottom-up feedback recognition.


5. http://download.springer.com/static/pdf/863/art%253A10.3758%252FBF03199279.pdf?


     - This link is to an article that discusses the depth of an image with illusory contours and how one might perceive a stimuli with illusory contours included in it.


6. http://download.springer.com/static/pdf/590/art%253A10.3758%252FBF03203054.pdf?auth66=1385167155_9c03c2e548ee9c2e51267fc0c99ef089&ext=.pdf

     - This link provides the article with the information on the effect of the brightness of an image on the illusory contours perceived.


7. http://www.sciencedirect.com/science/article/pii/S0896627302011480#

     - This link can be followed to an article about more fMRI results from subjects viewing illusory contours.


8. http://download.springer.com/static/pdf/445/art%253A10.3758%252FBF03210970.pdf?auth66=1385167359_c3bad8471a0c5022a5c092b2f812a53b&ext=.pdf  

     - The article that this link takes one to gives the history of illusory contours and much of the research that accompanies the founding of illusory contours.


9. http://cercor.oxfordjournals.org/content/10/7/663.full.pdf+html

     - This link takes one to an article on the way that the human brain reacts to moving illusory contours.


10. http://download.springer.com/static/pdf/561/art%253A10.1007%252Fs00359-002-0306-x.pdf?auth66=1385167571_d5f44c55a6f157b16b08694079dc947b&ext=.pdf

     - This particular link is to an article that discusses how animals perceive illusory contours and the differences and similarities between the perception of illusory contours by humans.

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