Café Wall Illusion

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Cafe Wall Illusion

The Cafe Wall Illusion is a geometric optical illusion that is created by the alignment of parallel lines in a checkerboard pattern. The parallel lines appear to be tilted or slanted, even though they are actually straight.

This illusion is caused by the interaction of the lines with the edges of the squares in the checkerboard pattern, which creates the illusion of depth and perspective.

Cafe Wall Illusion
The Café Wall Illusion

Table of Contents


How does the Café Wall Illusion work?

The Cafe Wall Illusion works by creating the illusion of depth and perspective through the interaction of parallel lines and the edges of the squares in the checkerboard pattern. The parallel lines in the pattern create the illusion of rows of bricks that appear to be slanted, even though they are actually straight. The edges of the squares in the pattern also play a role in creating the illusion by creating the perception of shadows and highlights on the “bricks.”

The way the lines and edges interact with each other creates a conflict in the brain between the perception of the lines as straight and the perception of the rows as tilted. The brain resolves this conflict by interpreting the rows as slanted, which creates the illusion of depth and perspective. Additionally, the alternating light and dark rows also contribute to the illusion, as the brain perceives them as different depths of the wall.

The illusion is also affected by the viewer’s distance from the image, as the perceived tilt of the lines changes as the viewer moves closer or farther away. This is because the angle of the lines changes relative to the viewer’s perspective, which changes the way the lines and edges interact with each other.

Versions of the Café Wall Illusion

The following are some alternate versions of the Café Wall Illusion:

Cafe-Wall-Illusion-Building-Wikimedia-Source
From Wikimedia Commons
Cafe-Wall-Illusion-Original-Cafe-with-Richard-Gregory-Wikimedia-Source.
Original Cafe with-discoverer Richard Gregory from Wikimedia Commons
Cafe-Wall-Illusion-Blue-and-Black
Cafe-Wall-Illusion-Orange-and-Black


Cafe-Wall-Illusion-Red-and-Blue.
Cafe-Wall-Illusion-Purple-Yellow-and-Black


Illusions like the Café Wall Illusion

The following are some illusions similar to the Café Wall Illusion.

The Rotating Snakes is a peripheral drift illusion that consists of a grid of shapes, with some of them appearing to be rotating or undulating. The illusion is created by the interaction of the shapes with the neural processing of the visual system.

Rotating Snakes Autokinetic effect


The Moiré pattern illusion: This illusion is created by superimposing two similar patterns on top of each other, such as a grid of lines or circles. The resulting pattern appears to be moving or changing.

Moiré_pattern
From Wikimedia Commons


The Scintillating Grid Illusion, in which a grid of black and white squares appears to pulsate or “breathe” when viewed from the periphery of the image.

Simultaneous Contrast Illusion


The Zöllner illusion is a visual illusion in which parallel lines appear to be angled due to the presence of intersecting lines.

The illusion is often used to study the brain’s perception of shape and spatial relationships. It is considered one of the most powerful and striking examples of a geometrical-optical illusion. The perception of the illusion can be explained by the brain’s tendency to group lines together based on their similarity in direction and spacing, which can lead to an overestimation of the angle between the parallel lines.

Zöllner illusion


The Müller-Lyer illusion: This illusion involves lines with arrowheads at the ends, which can make a line appear longer or shorter depending on the direction of the arrowheads.

müller-lyer illusion



The Poggendorff illusion is a visual illusion in which the brain perceives a diagonal line as being interrupted by an object, even though the line is actually continuous. The illusion is created by the misalignment of two parallel lines that are intersected by a third line at a certain angle.

Poggendorff illusion transparent gray bar



The Orbison illusion is an illusion of movement that is created when stationary, parallel lines are placed on a background of radiating lines. The parallel lines appear to be moving in the direction of the radiating lines, even though they are actually stationary. This illusion is thought to be caused by the interaction between the parallel lines and the radiating lines, which creates an illusion of movement in the brain.

Orbison Illusion



The Wundt illusion is an optical illusion produces an inversed effect compared to the Hering Illusion. The vertical lines are both straight, but they may look as if they are curved inwards.

Wundt Illusion



Discovery of the Café Wall Illusion

The Cafe Wall Illusion was first described by the British psychologist Richard Gregory in the 1970s.

Gregory was a cognitive psychologist who made significant contributions to the field of visual perception, including the discovery of the Cafe Wall Illusion.

He published his findings on the illusion in the journal “Nature” in 1973. Gregory was also known for his work on the perception of illusory contours and the perception of the Necker cube, which is another famous optical illusion.

References and Resources

Check out our complete list of illusions.

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Sarcone Müller-Lyer Illusion

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muller-lyer-illusion-blue-lines-sharp-angle

The Müller-Lyer illusion is a visual perception illusion that consists of two lines of equal length, with arrows at each end pointing either inward or outward. The line with the inward-pointing arrows appears shorter than the line with the outward-pointing arrows, even though they are actually the same length. This illusion is often used in research on visual perception and the neural basis of perception. The classic Müller-Lyer illusion is depicted below.

müller-lyer illusion
The Müller-Lyer Illusion

Visual artist G. Sarcone has created a series of Müller-Lyer adaptations that create the illusion of motion. The following is a simple version.

Dynamic_muller_lyer2B Sarcone


Table of Contents


How does the Standard Müller-Lyer Illusion work?

The Müller-Lyer illusion works by exploiting the brain’s tendency to interpret the visual information it receives in the context of other visual information. In the case of the Müller-Lyer illusion, the brain interprets the lines with inward-pointing arrows as being part of a concave shape, and the lines with outward-pointing arrows as being part of a convex shape. This interpretation leads the brain to perceive the lines with inward-pointing arrows as being shorter than they actually are, and the lines with outward-pointing arrows as being longer than they actually are.

This illusion is thought to be caused by the visual system’s use of depth cues, such as the size and angle of the arrowheads, to infer the three-dimensional structure of the lines. The visual system uses these cues to perceive the lines as being part of a 3D figure and not just a 2D representation. The perception of depth and distance are affected by the context of the arrowheads, which fool the visual system into perceiving the lines as if they were in different distances and therefore different sizes.

Another explanation of the illusion is based on the concept of “Gestalt grouping” where the brain organizes different elements in a scene into groups based on certain rules such as proximity, similarity, and continuity. The arrowheads in the Müller-Lyer illusion creates a sense of continuation and proximity between the lines and the arrowheads which leads to the perception of the lines as being different in length.


Dynamic Sarcone Versions of the Müller-Lyer Illusion

Sarcone_Sinusoiral_Muller_Lyer_Illusion
Courtesy of Wikimedia Commons
Sarcones_Pulsating_Star_Dynamic_Muller-Lyer_illusion
Courtesy of Wikimedia Commons


Muller_courbes_sinusB

MullerLyer_star_kaleidoscope


Muller_lyer_zig-zag


Muller_lyer_smooth


Illusions like the Müller-Lyer Illusion

There are many other visual perception illusions that work in similar ways to the Müller-Lyer illusion. Some examples include:

The Poggendorff illusion: This illusion is similar to the Müller-Lyer illusion, but instead of arrowheads, it uses a diagonal line that intersects two parallel lines. The brain perceives the diagonal line as being tilted, causing the parallel lines to appear as if they are not parallel.

Poppendorff Illusion Lines


The Ebbinghaus illusion: This illusion involves circles of different sizes, but with the same-sized circles placed close to each other. The brain perceives the smaller circles as being larger when they are placed next to larger circles.

Ebbinghaus Illusion


The T illusion: This illusion involves a T-shaped figure with a horizontal bar and a vertical bar. The brain perceives the vertical bar as being longer than the horizontal bar, even though they are the same length.

T Illusion


The Kanizsa triangle: This illusion is created by placing Pac-Man-like shapes around an invisible triangle. The brain perceives the triangle as if it were a real, visible triangle.

Kanizsa Triangle Illusion


The Zöllner illusion: This illusion involves parallel lines with diagonal lines intersecting them. The brain perceives the lines as if they were not parallel and that the diagonal lines are converging.

Zöllner illusion


Moon illusion: This illusion involves the perception of the Moon appearing larger when it is near the horizon compared to when it is high in the sky.

Moon Illusion


Ponzo illusion: This illusion involves the perception of an object appearing larger or smaller depending on the size of the surrounding context.

Ponzo Illusion


The Café Wall Illusion is a visual illusion that is created by a grid of alternating light and dark horizontal and vertical lines. The lines appear to be bent or tilted, even though they are actually straight.

Cafe Wall Illusion


All these illusions are based on the brain’s perception of visual context, depth cues, and grouping rules. These illusions help to understand how the brain interprets visual information and how it can be deceived.

Discovery of the Müller-Lyer Illusion

The Müller-Lyer illusion is a visual perception illusion that was first described by Franz Carl Müller-Lyer in 1889.

Franz Carl Müller-Lyer (1857-1916) was a German sociologist, psychologist, and philosopher. He is best known for his work on visual perception and the Müller-Lyer illusion, which is named after him. He studied at the University of Heidelberg and later at the University of Leipzig, where he received his Ph.D. in 1879.

In 1882, he published a book “Visual illusions: their causes, characteristics, and applications,” in which he described and illustrated the Müller-Lyer illusion, which is considered one of the most famous illusions in the field of psychology. He also wrote several books on the topic of social psychology, including “The People of Primitive Societies” and “The Social Order.”

Müller-Lyer was also a social reformer and advocated for better housing and living conditions for the working class. He was also interested in the relationship between society and the individual and his work aimed to bridge the gap between the social sciences, such as sociology and psychology.

Müller-Lyer died in 1916 in Munich, Germany. His work on the Müller-Lyer illusion and his contributions to the field of social psychology are still widely studied today.

References and Resources

Check out our complete list of illusions.

Sarcone, Gianni A. “Dynamic Müller-Lyer Illusion.” From Sarcone’s Studio — A Sarcone & Waeber Web Resource. http://giannisarcone.com/Muller_lyer_illusion.html


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Troxler’s Fading

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Lilac-Chaser_Troxlers Fading

Troxler’s fading, also known as Troxler’s effect, is a phenomenon in which a stationary visual stimulus eventually disappears from perception, even though it is still present in the visual field.

This occurs because the human visual system adapts to constant stimuli and eventually stops responding to them.

Lilac-Chaser_Troxlers Fading
From Wikimedia Commons
After staring at the cross for several seconds, the dots fade away

Table of Contents

How does Troxler’s Fading work?

Troxler’s fading occurs because of the way the human visual system processes information. The visual system is constantly receiving a flood of information from the eyes, and it must filter out the most important information in order to make sense of the world. One way it does this is by adapting to constant stimuli, so that they no longer capture our attention.

When a visual stimulus is presented in the same location for a prolonged period of time, the neurons in the brain that respond to that stimulus become less responsive, and eventually stop responding altogether. This is known as neural adaptation. As a result, the stimulus disappears from perception, even though it is still present in the visual field.

In addition to neural adaptation, other mechanisms such as lateral inhibition and surround suppression also play a role in Troxler’s fading. Lateral inhibition refers to the process by which the activation of one neuron in the visual system can inhibit the activity of neighboring neurons, which could lead to reduced perception of a stimulus. Surround suppression refers to the phenomenon where the presence of a stimulus in the surround of the fixation point can suppress perception of the stimulus at the fixation point.

Troxler’s fading effect is not limited to visual perception, but can be observed in other senses as well, such as touch and hearing.

Versions of the Troxler’s Fading

The following are some other examples of the Troxler’s Fading

Troxler-Fading
From Wikimedia Commons
After staring at the cross for several seconds, colors fade away



Toxler-Fading-Blue-Circle-Red-Dot
From Wikimedia Commons
After staring at the dot for several seconds, the colored ring fades away



Illusions like Troxler’s Fading

The following are some illusions that are related to Troxler’s Fading

The Phi phenomenon is the illusion of movement created by the rapid succession of static images or light sources.

It is the perceptual phenomenon that explains how the human brain perceives motion when presented with a sequence of still images or light sources that are displayed in rapid succession.

Magni-phi-phenomonon.
From Wikimedia Commons


The Rotating Snakes is a peripheral drift illusion that consists of a grid of shapes, with some of them appearing to be rotating or undulating. The illusion is created by the interaction of the shapes with the neural processing of the visual system.

Rotating Snakes Autokinetic effect


The Moiré pattern illusion: This illusion is created by superimposing two similar patterns on top of each other, such as a grid of lines or circles. The resulting pattern appears to be moving or changing.

Moiré_pattern
From Wikimedia Commons

The Scintillating Grid Illusion, in which a grid of black and white squares appears to pulsate or “breathe” when viewed from the periphery of the image.

Simultaneous Contrast Illusion



The Hermann Grid Illusion, in which the intersections of a white grid on a black background appear to be gray, even though they are actually the same color as the background.

Hermann-Grid Illusion


The Zöllner Illusion, in which parallel lines appear to be tilted or bent when intersected by diagonal lines.

Zöllner illusion


The Fraser Spiral Illusion, in which a pattern of short, curved lines appears to form a spiral.

Fraser-spiral-illusion.



The Hering Illusion, in which two straight lines appear to be curved due to the presence of surrounding lines.

Hering Illusion


The Café Wall Illusion is a visual illusion that is created by a grid of alternating light and dark horizontal and vertical lines. The lines appear to be bent or tilted, even though they are actually straight.

Cafe Wall Illusion



These illusions are usually caused by the way our eyes process visual information and the way the brain interprets it. They can also be caused by the interaction of different visual elements, such as lines and angles, in the image. They are often used in research on visual perception and the neural basis of perception.

Discovery of Troxler’s Fading

The effect is named after the Swiss physician and philosopher Ignaz Paul Vital Troxler, who first described it in 1804.

Ignaz Paul Vital Troxler was a Swiss physician and philosopher, born in 1780 and died in 1866. He was a physician in a Swiss hospital, and is most well-known for describing the phenomenon of Troxler’s fading, also known as Troxler’s effect, in 1804.

He first described this phenomenon in his doctoral thesis, in which he observed that a stationary visual stimulus, such as a fixed point, eventually disappears from perception even though it is still present in the visual field. He explained this phenomenon as being due to the adaptation of the retina to constant stimulus.

Troxler also made contributions to other fields, such as philosophy, psychology, and pedagogy. He published a number of papers on these subjects, and his ideas were well-received by his contemporaries.

He was also a professor at the University of Basel, where he taught anatomy and physiology.

References and Resources

Check out our complete list of illusions and check out this Cool version of Troxler’s fading

Phi Phenomenon

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Magni-phi-phenomonon.

The Phi phenomenon is the illusion of movement created by the rapid succession of static images or light sources.

It is the perceptual phenomenon that explains how the human brain perceives motion when presented with a sequence of still images or light sources that are displayed in rapid succession.

Magni-phi-phenomonon.
Phi Phenomenon
From Wikimedia Commons

Table of Contents

How does the Phi Phenomenon work?

The Phi phenomenon works by taking advantage of the way the human visual system processes information. The brain is able to perceive motion when it receives a series of still images or light sources that are displayed in rapid succession. This happens because the brain is able to fill in the gaps between the images or light sources and create the illusion of continuous movement.

When the brain receives a series of still images or light sources that are displayed in rapid succession, it processes them as if they were a single moving image. This is because the brain is able to fill in the gaps between the images or light sources and create the illusion of continuous movement. The brain does this by comparing the images or light sources to each other and determining the direction and speed of the motion.

The rate at which the images or light sources are displayed is also important in creating the illusion of motion. If the images or light sources are displayed too slowly, the brain will not be able to perceive motion. If they are displayed too quickly, the brain will not be able to process the information and the motion will appear choppy or jerky.

In summary, The Phi phenomenon is a perceptual illusion of movement created by the rapid succession of static images or light sources, works by the way the human visual system processes information, fills in the gaps between the images or light sources and creates the illusion of continuous movement, and the rate at which the images or light sources are displayed is also important in creating the illusion of motion.

Versions of the Phi Phenomenon Effect

The following are some other examples of the Phi Phenomenon

Phi Phenomenon Black Bars
From Wikimedia Commons



Phi_Phenomenon Yellow Circles
From Wikimedia Commons



Illusions like the Phi Phenomenon

The following are some illusions that are related to the Phi Phenomenon

Troxler’s fading, also known as Troxler’s effect, is a phenomenon in which a stationary visual stimulus, such as a dot or a shape, disappears from perception after a certain period of time.

Lilac-Chaser_Troxlers Fading
From Wikimedia Commons


The Rotating Snakes is a peripheral drift illusion that consists of a grid of shapes, with some of them appearing to be rotating or undulating. The illusion is created by the interaction of the shapes with the neural processing of the visual system.

Rotating Snakes Autokinetic effect


The Moiré pattern illusion: This illusion is created by superimposing two similar patterns on top of each other, such as a grid of lines or circles. The resulting pattern appears to be moving or changing.

Moiré_pattern
From Wikimedia Commons

The Scintillating Grid Illusion, in which a grid of black and white squares appears to pulsate or “breathe” when viewed from the periphery of the image.

Simultaneous Contrast Illusion



The Hermann Grid Illusion, in which the intersections of a white grid on a black background appear to be gray, even though they are actually the same color as the background.

Hermann-Grid Illusion


The Zöllner Illusion, in which parallel lines appear to be tilted or bent when intersected by diagonal lines.

Zöllner illusion


The Fraser Spiral Illusion, in which a pattern of short, curved lines appears to form a spiral.

Fraser-spiral-illusion.



The Hering Illusion, in which two straight lines appear to be curved due to the presence of surrounding lines.

Hering Illusion


The Café Wall Illusion is a visual illusion that is created by a grid of alternating light and dark horizontal and vertical lines. The lines appear to be bent or tilted, even though they are actually straight.

Cafe Wall Illusion



These illusions are usually caused by the way our eyes process visual information and the way the brain interprets it. They can also be caused by the interaction of different visual elements, such as lines and angles, in the image. They are often used in research on visual perception and the neural basis of perception.

Discovery of the Phi Phenomenon

The autokinetic effect was first described by German psychologist Max Wertheimer in 1912.

Max Wertheimer (April 15, 1880 – October 12, 1943) was a German psychologist, a founding member of the Gestalt school of psychology, and one of the key figures in the development of cognitive psychology.

He studied at the Charles-Ferdinand University in Prague and later at the University of Frankfurt where he got his PhD in Psychology. He then worked at the University of Berlin, the Psychological Institute of the University of Frankfurt, and the Psychological Institute of the University of Würzburg.

Wertheimer is best known for his work on the perception of movement, specifically the “phi phenomenon” and the “autokinetic effect.” He observed that when a series of lights are presented in rapid succession, they create the illusion of movement, even though each light is stationary. He also observed that when a single point of light is presented in a dark room, people perceive it as moving, even though it is stationary. These observations led Wertheimer to propose the idea that the mind organizes sensory information in patterns, rather than simply responding to individual stimuli.

His work on the “Gestalt” psychology influenced other researchers and also artists and designers, as it pointed out the importance of the context and the whole in the understanding of the perception.

References and Resources

Check out our complete list of illusions.

Autokinetic Effect

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Autokintetic effect

The autokinetic effect is an optical illusion in which a small, stationary point of light appears to move in the dark. The effect is caused by the visual system’s inability to accurately judge the distance of the point of light, which leads to the perception of movement.

It is similar to the concept of “kinetic depth effect” in which the visual system can’t determine the depth of a single point, and so it is perceived as moving.

Autokintetic effect
Autokinetic Effect

Table of Contents

How does the Autokinetic Effect work?

The autokinetic effect is a phenomenon in which a stationary point of light in a dark room appears to move, even though it is actually still. This effect is thought to be caused by the way the brain processes visual information.

When the visual system is presented with a single point of light in a dark environment, it has difficulty determining the light’s relative motion because there are no other visual cues to compare it to. As a result, the brain perceives the light as moving, even though it is not.

The autokinetic effect has been used in research to study perception and cognition, particularly in regards to the perception of movement. It has also been used to study the effects of factors such as attention, arousal, and cognitive set on the perception of movement.

The effect can be reduced by providing additional visual cues, such as adding more lights or providing a reference point.

In aviation, the autokinetic effect can be a problem when pilots are trying to determine the relative motion of a light in the sky. The effect can cause a stationary light, such as a star or a light on a stationary aircraft, to appear to be moving.

This can lead to confusion and disorientation for pilots, particularly when flying at night or in low-visibility conditions.

To counter the autokinetic effect, pilots use various visual cues, such as the horizon, other lights in the sky, or the movement of other aircraft, to help determine the relative motion of a light.

Additionally, aircraft instrumentation, such as radar and navigation systems, can also be used to help pilots accurately determine the position and movement of other aircraft.

Versions of the Autokinetic Effect

The following are some other examples of the Autokinetic effect:

Autokintetic-example-heart


Autokintetic-example
Autokintetic-example-thumbnail black and white
Autokintetic-example-three
Autokintetic-example
Autokintetic-example
Autokintetic-example circles black and white



Illusions like the Autokinetic Effect

The following are some illusions that are related to the Autokinetic effect.


The Rotating Snakes is a peripheral drift illusion that consists of a grid of shapes, with some of them appearing to be rotating or undulating. The illusion is created by the interaction of the shapes with the neural processing of the visual system.

Rotating Snakes Autokinetic effect


The Moiré pattern illusion: This illusion is created by superimposing two similar patterns on top of each other, such as a grid of lines or circles. The resulting pattern appears to be moving or changing.

Moiré_pattern
From Wikimedia Commons

The Scintillating Grid Illusion, in which a grid of black and white squares appears to pulsate or “breathe” when viewed from the periphery of the image.

Simultaneous Contrast Illusion



The Hermann Grid Illusion, in which the intersections of a white grid on a black background appear to be gray, even though they are actually the same color as the background.

Hermann-Grid Illusion


The Zöllner Illusion, in which parallel lines appear to be tilted or bent when intersected by diagonal lines.

Zöllner illusion


The Fraser Spiral Illusion, in which a pattern of short, curved lines appears to form a spiral.

Fraser-spiral-illusion.



The Hering Illusion, in which two straight lines appear to be curved due to the presence of surrounding lines.

Hering Illusion


The Café Wall Illusion is a visual illusion that is created by a grid of alternating light and dark horizontal and vertical lines. The lines appear to be bent or tilted, even though they are actually straight.

Cafe Wall Illusion



These illusions are usually caused by the way our eyes process visual information and the way the brain interprets it. They can also be caused by the interaction of different visual elements, such as lines and angles, in the image. They are often used in research on visual perception and the neural basis of perception.

Discovery of the Autokinetic Effect

The autokinetic effect was first described by German psychologist Max Wertheimer in 1912.

He observed the effect while conducting experiments on visual perception in which he presented participants with a single point of light in a dark room. He found that participants consistently reported that the light appeared to move, even though it was actually stationary.

Max Wertheimer (April 15, 1880 – October 12, 1943) was a German psychologist, a founding member of the Gestalt school of psychology, and one of the key figures in the development of cognitive psychology.

He studied at the Charles-Ferdinand University in Prague and later at the University of Frankfurt where he got his PhD in Psychology. He then worked at the University of Berlin, the Psychological Institute of the University of Frankfurt, and the Psychological Institute of the University of Würzburg.

Wertheimer is best known for his work on the perception of movement, specifically the “phi phenomenon” and the “autokinetic effect.” He observed that when a series of lights are presented in rapid succession, they create the illusion of movement, even though each light is stationary. He also observed that when a single point of light is presented in a dark room, people perceive it as moving, even though it is stationary. These observations led Wertheimer to propose the idea that the mind organizes sensory information in patterns, rather than simply responding to individual stimuli.

His work on the “Gestalt” psychology influenced other researchers and also artists and designers, as it pointed out the importance of the context and the whole in the understanding of the perception.

References and Resources

Check out our complete list of illusions.

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Rotating Snakes

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Rotating Snakes Autokinetic effect

The rotating snakes is a peripheral drift illusion that consists of a grid of shapes, with some of them appearing to be rotating or undulating. The illusion is created by the interaction of the shapes with the neural processing of the visual system.

Rotating Snakes Autokinetic effect
A Version of Rotating Snakes


Table of Contents


How does the Rotating Snakes Illusion work?

Rotating snakes is a type of peripheral drift illusion.

Peripheral drift illusions refer to a group of optical illusions where an object or pattern appears to be moving even though it is stationary. These illusions are often characterized by a perceived movement in the peripheral vision, hence the name.

Peripheral drift illusions work by exploiting the way the visual system processes information from the peripheral vision. Our eyes have a higher density of receptors, called rods, in the peripheral vision than in the central vision, and these receptors are more sensitive to movement. The peripheral vision also has a lower resolution and is less sensitive to details than the central vision.

Because of these characteristics, the visual system tends to perceive movement in the peripheral vision more easily than in the central vision. In a peripheral drift illusion, the visual elements of the illusion, such as lines or angles, are arranged in such a way that they create the illusion of movement in the peripheral vision.

Another mechanism that can cause peripheral drift illusions is the way that the brain interprets visual information. The brain uses context and prior experience to make sense of visual information, and this can lead to perceptual errors. For example, in the café wall illusion, the brain interprets the angled lines as the edges of a 3D object, which creates the illusion of movement.

In summary, peripheral drift illusions exploit the characteristics of the peripheral vision, such as sensitivity to movement and lower resolution, and the way the brain interprets visual information to create the illusion of movement in stationary images.

Versions of the Rotating Snakes Illusion

The following are some alternate versions of the Rotating Snakes illusion and some other examples of peripheral drift illusions



Cafe Wall Variant with Peripheral drift
From Wikimedia Commons

Peripheral drift illusion jelly bean
From Wikimedia Commons



Peripheral drift illusion
From Wikimedia Commons


Illusions like the Rotating Snakes Illusion

Peripheral drift illusions refer to a group of optical illusions where an object or pattern appears to be moving even though it is stationary. These illusions are often characterized by a perceived movement in the peripheral vision, hence the name.

Some illusions like Rotating Snakes and peripheral drift illusion include:

The Moiré pattern illusion: This illusion is created by superimposing two similar patterns on top of each other, such as a grid of lines or circles. The resulting pattern appears to be moving or changing.


Moiré_pattern
From Wikimedia Commons


The Scintillating Grid Illusion, in which a grid of black and white squares appears to pulsate or “breathe” when viewed from the periphery of the image.

Simultaneous Contrast Illusion



The Hermann Grid Illusion, in which the intersections of a white grid on a black background appear to be gray, even though they are actually the same color as the background.

Hermann-Grid Illusion


The Zöllner Illusion, in which parallel lines appear to be tilted or bent when intersected by diagonal lines.

Zöllner illusion


The Fraser Spiral Illusion, in which a pattern of short, curved lines appears to form a spiral.

Fraser-spiral-illusion.



The Hering Illusion, in which two straight lines appear to be curved due to the presence of surrounding lines.

Hering Illusion


The Café Wall Illusion is a visual illusion that is created by a grid of alternating light and dark horizontal and vertical lines. The lines appear to be bent or tilted, even though they are actually straight.

Cafe Wall Illusion



These illusions are usually caused by the way our eyes process visual information and the way the brain interprets it. They can also be caused by the interaction of different visual elements, such as lines and angles, in the image. They are often used in research on visual perception and the neural basis of perception.


Discovery of the Rotating Snakes Illusion


The most famous variant of the rotating snakes illusion was created by Akiyoshi Kitaoka.

Akiyoshi Kitaoka is a Japanese psychologist and professor at Ritsumeikan University, known for his research and popularization of visual illusions.

He has published numerous papers and books on the topic, and has created many original illusions, such as the Rotating Snakes illusion and the “Rainbow” illusion.

He is considered one of the leading experts on visual perception and the cognitive processes that underlie it.

Kitaoka has a personal website called “Akiyoshi’s Illusion Pages” in which he displays his research and creations of illusions.

He has won several awards for his work, including the Award for Outstanding Research on Visual Perception from the Japanese Society for Visual Perception.


References and Resources

Check out our complete list of illusions.

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Kanizsa Triangle

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Kanizsa Triangle Illusion

The Kanizsa triangle is a visual illusion that was first described by the Italian psychologist Gaetano Kanizsa in 1955. The illusion consists of a white equilateral triangle that appears to be surrounded by three Pac-Man-like shapes, which are black and have white crescents facing inwards.

The three Pac-Man-like shapes are actually made up of three partially-overlapping circles with white edges that create the illusion of a triangle.

The Kanizsa triangle is an example of an “amodal completion” illusion, in which the brain fills in missing information to complete an object or shape. In this case, the brain completes the triangle by connecting the three white crescents of the circles together. The illusion is thought to occur because the brain is wired to perceive objects as whole and complete, even when they are not fully present in the visual field.

Kanizsa Triangle Illusion
The Kanizsa Triangle

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How does the Kanizsa Triangle work?

The Kanizsa triangle illusion works by exploiting the way our brain processes visual information. The brain tends to group together similar elements in an image to form a coherent whole, a process called “Gestalt grouping” . In the case of the Kanizsa triangle, the brain groups the three partially-overlapping circles with white edges together and interprets them as the edges of a triangle, even though the triangle is not physically present.

Another aspect that is thought to contribute to the illusion is the way the brain uses “Amodal completion” to perceive objects. Amodal completion refers to the brain’s ability to fill in missing information to complete an object or shape. In this case, the brain fills in the missing parts of the triangle by connecting the three white crescents of the circles together, creating the illusion of a complete white equilateral triangle.

Additionally, the visual cues of the overlapping circles and the angles of the white crescents contribute to the perception of the triangle as well, making it look as if the triangle is emerging from behind the circles, even though it is not physically present.

Overall, the Kanizsa triangle works by exploiting the brain’s ability to group together similar elements and fill in missing information to create the illusion of a complete, non-existent triangle.


Versions of the Kanizsa Triangle

The following are some alternate versions of the Kanizsa Triangle:

Kanizsa-Star
Source: Wikimedia Commons
Reification-Examples-Kanizsa
Source: Wikimedia Commons


Kanizsa-Square
Kanizsa-Triangle-colorful


Illusions like the Kanizsa Triangle

Illusory contour illusions are a type of visual illusion in which the brain perceives contours or edges that are not physically present in an image.

These illusions can be created by using a variety of visual cues, such as shading, texture, or the arrangement of simple shapes, to create the illusion of a more complex shape. Some examples of illusory contour illusions include:

The Muller-Lyer illusion: an illusion in which two lines of the same length appear to be of different lengths due to the presence of arrowheads at the ends of the lines.

müller-lyer illusion



The Poggendorff illusion: an illusion in which two lines that are parallel in reality appear to be skewed or converging due to the presence of a third shape in the foreground.

Poggendorff illusion transparent gray bar



The Café Wall illusion: an illusion in which the lines that form a tiled wall appear to be skewed or distorted due to the presence of contrasting colored tiles.

Cafe Wall Illusion



The Zöllner illusion: an illusion in which parallel lines appear to be skewed or converging due to the presence of intersecting lines at an angle.

Zöllner illusion


All these illusions work by exploiting the way the brain processes visual information and the way it interprets the relationship between different elements in an image. Illusory contours are thought to be created by the activity of neurons that respond selectively to edges and contours in the visual field, which can be influenced by different visual cues.


Discovery of the Kanizsa Triangle

The Kanizsa triangle is a visual illusion that was first described by the Italian psychologist Gaetano Kanizsa in 1955.

Gaetano Kanizsa (1913-1993) was an Italian psychologist and neuropsychologist, known for his research in the field of visual perception and his contributions to the understanding of visual illusions. He is most famous for his work on amodal completion, which refers to the brain’s ability to fill in missing information to complete an object or shape, and for his description of the Kanizsa triangle, one of the most famous and studied amodal completion illusion.

He was a professor of Psychology at the University of Trieste in Italy, and his research focused on the relationship between perception and reality. He also developed the concept of “subjective contours” which refers to the ability of the brain to perceive contours that are not physically present in an image, and was a pioneer in the field of neuropsychology. His work has had a significant impact on the field of cognitive psychology and has influenced the work of many researchers in the field of visual perception.

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Orbison Illusion

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Orbison Illusion

The Orbison illusion is a visual illusion in which a two dimensional shape such as a square or circle, when surrounded by a pattern of radiating lines, appear to be distorted or flattened.

The illusion is an example of an “inductive illusion,” in which the surrounding context of an image can affect the perception of the central image.

Orbison Illusion
The Orbison Illusion

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How does the Orbison Illusion work?

The illusion is an example of an “inductive illusion,” in which the surrounding context of an image can affect the perception of the central image. The exact neural mechanism behind the illusion is not well understood.

Inductive illusions are a type of visual illusion in which the perception of an image is influenced by the surrounding context. The surrounding context can be made up of other images, patterns, or shapes, and it can affect the perception of the central image in various ways. The exact neural mechanism behind inductive illusions is not well understood, but it is thought to involve the way the brain processes visual information. Some theories suggest that the brain uses prior knowledge and expectations to interpret the image, which can lead to the illusion.

One theory is that the brain uses a process called “gestalt grouping” to organize visual information. This process involves grouping together similar elements in an image to form a coherent whole. In an inductive illusion, the surrounding context can influence how the brain groups the elements of the central image, leading to the illusion.

Another theory is that the brain uses a process called “top-down processing” to interpret visual information. This process involves using prior knowledge and expectations to interpret an image, rather than relying solely on the visual information present in the image. In an inductive illusion, the surrounding context can influence the expectations and assumptions that the brain makes about the central image, leading to the illusion.

It is likely that multiple mechanisms are at play and it is possible that different illusions may have different underlying neural mechanisms.

Versions of the Orbison Illusion

The following are some alternate versions of the Orbison Illusion:

Orbison-illusion-Circles

Orbison-illusion-Circles-Red-on-Blue


Illusions like the Orbison Illusion

The following are some illusions similar to the Orbison Illusion

The Hering illusion is a visual illusion that involves the perception of curved lines as being bowed inwards or outwards. In the illusion, the red lines appear to curve. In realty, the red lines are perfectly straight.

Hering Illusion


The Zöllner illusion is a visual illusion in which parallel lines appear to be angled due to the presence of intersecting lines.

The illusion is often used to study the brain’s perception of shape and spatial relationships. It is considered one of the most powerful and striking examples of a geometrical-optical illusion. The perception of the illusion can be explained by the brain’s tendency to group lines together based on their similarity in direction and spacing, which can lead to an overestimation of the angle between the parallel lines.

Zöllner illusion


The Müller-Lyer illusion: This illusion involves lines with arrowheads at the ends, which can make a line appear longer or shorter depending on the direction of the arrowheads.

müller-lyer illusion


The Poggendorff illusion is a visual illusion in which the brain perceives a diagonal line as being interrupted by an object, even though the line is actually continuous. The illusion is created by the misalignment of two parallel lines that are intersected by a third line at a certain angle.

Poggendorff illusion transparent gray bar




Discovery of the Orbison Illusion


This illusion is named after the American psychologist William Orbison, who first described it in 1939.


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Wundt Illusion

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Wundt Illusion

The Wundt illusion is a visual illusion in which two lines that are parallel appear to be converging or diverging. It is believed to be caused by the brain’s tendency to perceive the angles of lines in relation to other lines or shapes in the visual field. The Wundt illusion produces a similar, but inverted effect to the Hering Illusion

Wundt Illusion
The Wundt Illusion

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How does the Wundt Illusion work?

The Wundt illusion is a visual illusion that involves the perception of curved lines as being bowed inwards or outwards. The illusion is often used to study the perception of depth and the role of the visual system in shaping our perception of the world.

The Wundt illusion is thought to be caused by the brain’s perception of angles in relation to other lines or shapes in the visual field. When two parallel lines are presented with converging or diverging lines around them, the brain interprets the angles of the parallel lines in relation to these surrounding lines, which leads to the perception of the parallel lines as converging or diverging.

The illusion also can be caused by the context of the lines, as the position of the lines on the visual field, the color, the length, and the width of the lines also play a role in the perceived illusion.

The perception of the illusion is thought to be caused by the brain’s tendency to perceive the lines as being farther away or closer based on their spacing. The lines that are closer together are perceived as being farther away, while the lines that are farther apart are perceived as being closer. This leads to the perception of the lines as curved, when in reality they are straight.

The Wundt illusion is used to demonstrate the role that context and surrounding plays in shaping our perception of reality. It also highlights how the brain uses depth cues such as relative size, distance, and position to perceive the 3D world around us.

Versions of the Wundt Illusion

The following are some alternate versions of the Wundt Illusion:

Hering-Illusion-alternate-version-square-background
Red Lines Appear to Bend
Hering-Illusion-alternate-version-square-background-removed
With background removed,
red lines are perfectly straight
Hering-Illusion-alternate-version-circle-background
Red Lines appear to bend
Hering-Illusion-alternate-version-circle-background-removed
With background removed,
red lines are perfectly straight


Illusions like the Wundt Illusion

The following are some illusions similar to the Wundt Illusion

The Hering illusion is an optical illusion produces an inversed effect compared to the Wundt Illusion. The vertical lines are both straight, but they may look as if they are curved inwards.

Hering Illusion


The Zöllner illusion is a visual illusion in which parallel lines appear to be angled due to the presence of intersecting lines.

The illusion is often used to study the brain’s perception of shape and spatial relationships. It is considered one of the most powerful and striking examples of a geometrical-optical illusion. The perception of the illusion can be explained by the brain’s tendency to group lines together based on their similarity in direction and spacing, which can lead to an overestimation of the angle between the parallel lines.

Zöllner illusion


The Müller-Lyer illusion: This illusion involves lines with arrowheads at the ends, which can make a line appear longer or shorter depending on the direction of the arrowheads.

müller-lyer illusion


The Poggendorff illusion is a visual illusion in which the brain perceives a diagonal line as being interrupted by an object, even though the line is actually continuous. The illusion is created by the misalignment of two parallel lines that are intersected by a third line at a certain angle.

Poggendorff illusion transparent gray bar


The Orbison illusion is an illusion of movement that is created when stationary, parallel lines are placed on a background of radiating lines. The parallel lines appear to be moving in the direction of the radiating lines, even though they are actually stationary. This illusion is thought to be caused by the interaction between the parallel lines and the radiating lines, which creates an illusion of movement in the brain.

Orbison Illusion


Discovery of the Wundt Illusion


This illusion is named after the German psychologist Wilhelm Wundt, who first described it in the late 19th century.

Wilhelm Wundt (1832-1920) was a German physician, psychologist, and philosopher who is considered to be the father of experimental psychology.

He established the first psychological laboratory in Leipzig, Germany in 1879, where he conducted research on a wide range of topics including perception, sensation, attention, and consciousness.

He is also known for his work on the structure of the mind and his development of introspection as a method of psychological research.

Wundt’s work laid the foundation for the development of psychology as an independent scientific discipline, and his laboratory was the model for many other psychological laboratories that were established throughout Europe and the United States.

He also wrote several influential books, such as “Principles of Physiological Psychology” which was considered a groundbreaking work in the field of psychology.

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Titchener Circles Illusion

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Ebbinghaus Illusion

The Ebbinghaus illusion (also known as Titchener circles) is a perceptual illusion in which the perceived size of a central circle is affected by the size of the surrounding circles. The central circle appears smaller when surrounded by larger circles, and larger when surrounded by smaller circles.

Ebbinghaus Illusion
The Ebbinghaus (Titchener Circles) Illusion


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How does the Titchener Circles Illusion work?

The Titchener Circles illusion works by exploiting the way our brain processes visual information. Our brain is constantly trying to make sense of the visual information it receives by making comparisons and judgments about the size, shape, and position of objects in our environment. In the case of the Ebbinghaus illusion, the brain is making a comparison between the size of the central circle and the size of the surrounding circles.

When the surrounding circles are larger than the central circle, our brain perceives them as being farther away and thus the central circle appears smaller in comparison. When the surrounding circles are smaller than the central circle, our brain perceives them as being closer and the central circle appears larger in comparison.

Additionally, the brain also takes into account the proximity of the surrounding circles to the central circle. So, if the surrounding circles are placed in close proximity to the central circle, it will appear smaller than when they are placed farther away.

This illusion is thought to be caused by a neural mechanism in the brain called contextual modulation, which modifies the visual perception of an object based on the context in which it is presented. The Ebbinghaus illusion is a classic example of how context can affect perception and highlights the complex nature of visual processing in the brain.

Versions of the Titchener Circles Illusion


The following are some alternate versions of the Titchener Circles Illusion

Ebbinghaus Illusion Alternate Version with Lines
Ebbinghaus-Illusion-Alternate-Version
Ebbinghaus Illusion Alternate Version Circle
Ebbinghaus Illusion Alternate Version Titchener Circle

Illusions like the Titchener Circles Illusion

The Titchener Circles illusion is a type of size-contrast illusion. A size-contrast illusion is a type of visual illusion in which the perceived size of an object is affected by the size of the surrounding objects. The Ebbinghaus illusion specifically is related to relative size, where the perception of the size of the central circle changes depending on the size of the surrounding circles. Size-contrast illusions occur due to the way that the visual system processes relative size information in a scene, and the Ebbinghaus illusion is a classic example of this type of illusion.

There are many other examples of size-contrast illusions in addition to the Titchener Circles illusion. Here are a few examples:

The Delboeuf illusion is similar to the Titchener Circles illusion, but instead of circles, it uses two concentric circles or rings. The central ring appears larger or smaller depending on the size of the surrounding ring.

Delboeuf Illusion
delboeuf illusion with food.


The Poggendorff illusion is another size-contrast illusion in which a straight line appears to be bent or angled, due to the presence of intersecting lines or shapes in the background.

Poppendorff Illusion Lines

The Zöllner illusion is another size-contrast illusion in which a group of diagonal lines appear to be distorted or bent due to the presence of intersecting lines.

Zöllner illusion


The Müller-Lyer illusion is a classic example of size-contrast illusion, in which two lines of equal length appear to be different due to the presence of arrowheads or fins at the end of the lines.

müller-lyer illusion

All of these illusions rely on the way the visual system processes relative size information, and they all highlight the complexity and malleability of visual perception.


Discovery of the Ebbinghaus / Titchener Circles Illusion

This illusion is named after German psychologist Hermann Ebbinghaus, who first described it in the late 19th century. The illusion is thought to be caused by the way the brain processes relative size information in visual scenes.

Hermann Ebbinghaus (1850-1909) was a German psychologist who is best known for his pioneering research on memory and forgetting. He was one of the first researchers to systematically study memory as a psychological process and his work laid the foundation for the field of experimental psychology. Ebbinghaus conducted a series of experiments in which he memorized lists of nonsense syllables and then tested his own memory at various intervals to measure the rate of forgetting.

He also developed the first standardized memory test, called the “memory drum”, which consisted of a rotating drum with lists of words or syllables that could be presented to participants at different intervals. He used these tests to study the effects of different factors, such as repetition and interference, on memory retention.

Ebbinghaus also made significant contributions to the understanding of memory processes, such as the spacing effect, which states that spaced practice is more effective than massed practice in enhancing memory retention.

Ebbinghaus’s work was groundbreaking in the field of psychology and is still widely cited today. The Ebbinghaus illusion, the size-contrast illusion that bears his name, was discovered by him in 1885 but is not as well-known as his memory research.


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