Difference between revisions of "Grid illusion" - New World Encyclopedia

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[[Category:Politics and social sciences]]
 
[[Category:Politics and social sciences]]
 
[[Category:Psychology]]
 
[[Category:Psychology]]
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[[Category:Illusion]]
  
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[[Image:Grid illusion.svg|thumb|200px|right|An example of the scintillating grid illusion. Dark dots seem to appear and disappear at intersections.]]
  
[[Image:Grid illusion.svg|thumb|256px|right|An example of the Scintillating grid illusion]]
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A '''grid illusion''' is any kind of [[grid]] that deceives a person's vision. The two most common types of grid illusions are '''Hermann grid illusions''' and '''Scintillating grid illusions'''.
A '''grid illusion''' is any kind of [[grid]] that deceives a person's vision. The two most common types of grid illusions are '''Scintillating grid illusions''' and '''Hermann grid illusions'''.
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{{toc}}
==Scintillating grid illusion==
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Illusions such as these, and others, provide a window onto the way the eyes and the brain work together in creating perception. Scientists attempt to peer through this window when they propose hypotheses about how perception is accomplished. Illusions can also help us realize that our own perceptions may be limited or different from those of another person viewing the same thing.
The '''Scintillating grid illusion''' is an [[optical illusion]] when dots seem to appear and disappear at the intersections of two lines crossing each other vertically and horizontally. When a person keeps his or her eyes directly on a single intersection, the dot does not appear. A variation of the Scintillating illusion is the Hermann grid illusion (see section below). In the picture on the right, a person should see white dots turn black and then turning white again very fastThe dots disappear if one is too close or too far from the image.
 
  
==Hermann grid illusion==
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==Discovery==
[[Image:Hermann grid illusion.svg|thumb|202px|left|A Hermann grid illusion. Shape position and color [[contrast (vision)|contrast]] converge to produce the illusion of spots at the intersections.]]
 
The '''Hermann grid illusion''' is an [[optical illusion]] reported by [[Ludimar Hermann]] in [[1870]] while, incidentally, reading [[John Tyndall]]'s ''Sound''. It is very similar to the Scintillating grid illusion.
 
  
Like the Scintillating grid illusion, when looking at a grid of black squares on a white (or light-colored) background, one will have the impression that there are "ghostlike" grey blobs at the intersections of the white lines.  The grey blobs disappear when looking directly at an intersection.
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The '''Hermann grid illusion''' was first reported by [[Ludimar Hermann]] in 1870, who discovered the illusion while reading [[John Tyndall]]'s ''On Sound''. In 1872, [[Ewald Hering]] observed that inverse colors (a black grid on a white background) produced similar results. Because of this, the Hermann grid is often referred to as the "Hermann-Hering" grid.
  
[[Image:White grid illusion.svg|thumb|218px|right|Another type of Hermann grid illusion.]]
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The '''scintillating grid illusion''' is an [[optical illusion]] discovered by Elke Lingelbach in 1994, and is usually considered a variation of the Hermann grid illusion. Lingelbach and colleagues published their findings in a 1995 article entitled "The Hermann grid and the scintillation effect" (''Perception'' 24, supplement, page 89).
  
==Differences between the Scintillating and Hermann grid illusions==
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==Description==
The difference between the Hermann grid illusion and the Scintillating illusion is that Scintillating illusions have dots already in place at the intersection, whereas there are no dots already in place at the intersections of Hermann grid illusions. However, since they are so similar, the two names are commonly switched around.
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The Hermann grid illusion is created with a grid of black squares upon a white background. "Ghostlike" gray figures are perceived at the intersections of the white lines. These figures disappear when one looks directly at an intersection.
  
==The cause of both Scintillating and Hermann grid illusions==
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The scintillating grid illusion is similar in construction. Instead of white bars, however, there are gray bars with white discs inserted at each intersection. When viewers moves their eyes around the image, black dots seem to appear and disappear. The illusion is enhanced by eye movement, and decreased by moving too close or too far away from the image.
The effect of the optical illusion is commonly (and falsely) explained by a neural process called [[lateral inhibition]]. The intensity at a point in the visual system is not simply the result of a single [[sensory receptor|receptor]], but the result of a group of receptors called a [[receptive field]].
 
  
In the center of the receptive field, the receptors act ''excitatory'' on the resulting signal, and the receptors in the surrounding area act ''inhibitory'' on the signal.  Thus, since a point at an intersection is surrounded by more intensity than a point at the middle of a line, the intersection appears darker. In a person's eyes, the nerve cells of the retina associate and interact with each other, which results in the illusion that there are dots, when there really aren't.
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==Explanation==
  
This explanation has recently been successfully challenged by Janos Geier (see the [http://www.michaelbach.de/ot/lum_herGridCurved/index.html interactive counter example]).
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[[Image:White grid illusion.svg|thumb|256px|left|A white-background version of the scintillating grid illusion.]]
  
==References==
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The effect of both optical illusions is commonly explained by a neural process called [[lateral inhibition]]. [[Retina]]l cells in the [[eye]] function as light receptors. If only a single receptor is illuminated, it perceives a larger amount of light than it does when neighboring receptors are also illuminated. The illumination of receptors inhibits the firing of nearby receptors, and the effect is transmitted laterally. In the case of the Hermann grid illusion, the setup of the white bands creates a situation where there is more light surrounding the intersections than there is along the bands between intersections. Thus the region of the intersection is more inhibited, and darker spots appear. The effect is greater when the grid is viewed peripherally, since lateral inhibition works over greater distances in peripheral vision.<ref>[http://psylux.psych.tu-dresden.de/i1/kaw/diverses%20Material/www.illusionworks.com/html/hermann_grid.html"Hermann Grid"] 1997. Illusion Works. Retrieved October 30, 2007.</ref>
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==External links==
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Scientists at [[MIT]]'s Schiller Lab have disputed this widely accepted theory, proposing an alternate type of retinal functioning as an explanation for the illusion. Advocates of such alternative theories argue that the Hermann grid effect is not size dependent, works equally well with contrast reversal, and that there are misconceptions in the function of retinal cells that are assumed by the lateral inhibition theory.<ref>[http://web.mit.edu/bcs/schillerlab/research/A-Vision/A15-4.htm "The Neural Control of Vision"] MIT. Retrieved October 30, 2007.</ref> The proposed alternate theory, called the "S1 simple-cell theory," suggests that the illusion results from reactions within the [[cortex]], not the retinal cells.<ref>[http://web.mit.edu/bcs/schillerlab/research/A-Vision/A15-17.htm "The Neural Control of Vision"] MIT. Retrieved October 30, 2007.</ref>
*[http://www.michaelbach.de/ot/lum_herGrid/index.html Refutation of classical explanation of Hermann Grid Illusion]
 
*[http://mathworld.wolfram.com/ScintillatingGridIllusion.html Scintillating Grid Illusion – Mathworld]
 
*[http://www.josef.org/scintillating.html Giant grid]
 
* [http://eefoof.com/image/10131 Large Hermann Grid Illusion]
 
  
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==Applications==
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Both types of grid illusions, as well as related illusions, are excellent tools that help further the study of [[neuroscience]]. Scientists can use anomalies like perceptual illusions to try to understand more precisely the processes involved in [[vision]] and [[perception]].
  
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==Notes==
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<references />
  
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==References==
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*Baars, Bernard and Nicole Gage. ''Cognition, Brain, and Consciousness: Introduction to Cognitive Neuroscience''. Academic Press, 2007. ISBN 0123736773
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*Fineman, Mark. ''The Nature of Visual Illusion''. Dover Publications, 1996. ISBN 0486291057
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*Ninio, Jacques. ''The Science of Illusions''. Cornell University Press, 2001. ISBN 0801437709
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*Seckel, Al. ''Art of Optical Illusions''. Carlton Books, 2000. ISBN 1842220543
  
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==External links==
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All links retrieved July 17, 2017.
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*[http://mathworld.wolfram.com/ScintillatingGridIllusion.html Scintillating Grid Illusion - Mathworld]
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*[http://www.michaelbach.de/ot/lum-herGrid/index.html Refutation of classical explanation of Hermann Grid Illusion]
  
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Latest revision as of 12:27, 24 January 2023


An example of the scintillating grid illusion. Dark dots seem to appear and disappear at intersections.

A grid illusion is any kind of grid that deceives a person's vision. The two most common types of grid illusions are Hermann grid illusions and Scintillating grid illusions.

Illusions such as these, and others, provide a window onto the way the eyes and the brain work together in creating perception. Scientists attempt to peer through this window when they propose hypotheses about how perception is accomplished. Illusions can also help us realize that our own perceptions may be limited or different from those of another person viewing the same thing.

Discovery

The Hermann grid illusion was first reported by Ludimar Hermann in 1870, who discovered the illusion while reading John Tyndall's On Sound. In 1872, Ewald Hering observed that inverse colors (a black grid on a white background) produced similar results. Because of this, the Hermann grid is often referred to as the "Hermann-Hering" grid.

The scintillating grid illusion is an optical illusion discovered by Elke Lingelbach in 1994, and is usually considered a variation of the Hermann grid illusion. Lingelbach and colleagues published their findings in a 1995 article entitled "The Hermann grid and the scintillation effect" (Perception 24, supplement, page 89).

Description

The Hermann grid illusion is created with a grid of black squares upon a white background. "Ghostlike" gray figures are perceived at the intersections of the white lines. These figures disappear when one looks directly at an intersection.

The scintillating grid illusion is similar in construction. Instead of white bars, however, there are gray bars with white discs inserted at each intersection. When viewers moves their eyes around the image, black dots seem to appear and disappear. The illusion is enhanced by eye movement, and decreased by moving too close or too far away from the image.

Explanation

A white-background version of the scintillating grid illusion.

The effect of both optical illusions is commonly explained by a neural process called lateral inhibition. Retinal cells in the eye function as light receptors. If only a single receptor is illuminated, it perceives a larger amount of light than it does when neighboring receptors are also illuminated. The illumination of receptors inhibits the firing of nearby receptors, and the effect is transmitted laterally. In the case of the Hermann grid illusion, the setup of the white bands creates a situation where there is more light surrounding the intersections than there is along the bands between intersections. Thus the region of the intersection is more inhibited, and darker spots appear. The effect is greater when the grid is viewed peripherally, since lateral inhibition works over greater distances in peripheral vision.[1]

Scientists at MIT's Schiller Lab have disputed this widely accepted theory, proposing an alternate type of retinal functioning as an explanation for the illusion. Advocates of such alternative theories argue that the Hermann grid effect is not size dependent, works equally well with contrast reversal, and that there are misconceptions in the function of retinal cells that are assumed by the lateral inhibition theory.[2] The proposed alternate theory, called the "S1 simple-cell theory," suggests that the illusion results from reactions within the cortex, not the retinal cells.[3]

Applications

Both types of grid illusions, as well as related illusions, are excellent tools that help further the study of neuroscience. Scientists can use anomalies like perceptual illusions to try to understand more precisely the processes involved in vision and perception.

Notes

  1. "Hermann Grid" 1997. Illusion Works. Retrieved October 30, 2007.
  2. "The Neural Control of Vision" MIT. Retrieved October 30, 2007.
  3. "The Neural Control of Vision" MIT. Retrieved October 30, 2007.

References
ISBN links support NWE through referral fees

  • Baars, Bernard and Nicole Gage. Cognition, Brain, and Consciousness: Introduction to Cognitive Neuroscience. Academic Press, 2007. ISBN 0123736773
  • Fineman, Mark. The Nature of Visual Illusion. Dover Publications, 1996. ISBN 0486291057
  • Ninio, Jacques. The Science of Illusions. Cornell University Press, 2001. ISBN 0801437709
  • Seckel, Al. Art of Optical Illusions. Carlton Books, 2000. ISBN 1842220543

External links

All links retrieved July 17, 2017.

Credits

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