Color Illusions

Color Constancy

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Color constancy

A color constancy illusion is a type of visual illusion in which a color appears to be different when viewed in different contexts.

For example, the same patch of color may appear lighter or darker when viewed against different backgrounds, or may appear to change color when viewed under different lighting conditions.

These illusions are thought to be caused by the way the human visual system processes color information, and can have important implications for fields such as graphic design and color science.

Color constancy
Color Constancy


Table of Contents


How does the Color Constancy work?

Color constancy illusions are thought to be caused by the way the human visual system processes color information. The human eye and brain work together to perceive color, and the perception of color is influenced by a variety of factors including the surrounding colors, lighting conditions, and the physical characteristics of the object being viewed.

One theory is that these illusions occur because the human visual system uses surrounding colors to interpret the color of an object. When the surrounding colors are different, the same object can appear to have a different color. This is known as the “Simultaneous Contrast” illusion.

Another theory is that the human visual system uses the lighting conditions to interpret the color of an object, and this can lead to illusions. For example, an object may appear to be one color in natural daylight and another color under artificial light. This is known as the “Metamerism” illusion.

Additionally, the physical characteristics of the object being viewed can also influence the perception of color. For example, the texture, surface finish, and gloss of an object can all affect how it reflects light and how it appears to the observer. This is known as the “Interference” illusion.

Overall, color constancy illusions are the result of the complex interaction between the human visual system and the physical and environmental factors that influence the perception of color.

Versions of the Color Constancy

The following are other examples of the Color Constancy:



Color constancy



Color constancy



Illusions like Color Constancy

Some related illusions include the following:

The Checker Shadow Illusion is created by a checkerboard pattern composed of squares with different luminance values, the squares that are not directly illuminated by the light source appear darker than the illuminated squares, creating the illusion of shadows.

Edelson-Checker_shadow_illusion
Checker Shadow Illusion


The simultaneous contrast illusion is a visual effect that occurs when the perception of a color is affected by the colors of the surrounding area.

The illusion creates the appearance of a change in the color of an object, even though the actual color of the object remains constant.


Simultaneous Contrast Effect
The center green dot is the same on both sides, but the surrounding color changes the perception


The Neon Color Spreading illusion refers to the visual phenomenon where an area of color appears to spread or “bleed” beyond its intended boundaries.

Neon Color Spreading
From Wikimedia Commons


The Bezold Effect: This illusion is created by placing two or more colors next to each other, and the way they appear to change when they are close to one another.  

Bezold_Effect
from Wikimedia Commons


The Cornsweet illusion is a classic example of a brightness illusion, which is an illusion in which two areas that are physically the same brightness appear to be different in brightness.

Cornsweet illusion
Cornsweet illusion

The Chubb illusion is based on the perception of brightness and can be observed when a small bright patch is surrounded by a larger dark area, the small bright patch will appear brighter than the same patch surrounded by a bright area.

Chubb Illusion

White’s illusion is a visual phenomenon in which two identical gray bars are placed on a background of alternating black and white stripes.

The gray bars appear to be different shades of gray, with the one on the white stripes appearing lighter than the one on the black stripes.

In the image below, both gray bars have the exact same color.

White's Illusion
White’s Illusion

The Watercolor Illusion: This illusion is created by the way the brain perceives edges of an object. When an object is surrounded by a colored halo, the object appears to have a different color than it actually does.

Watercolor 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


Discovery of the Color Constancy

The concept of color constancy, which refers to the ability of the human visual system to perceive the colors of objects as constant despite changes in the lighting conditions, was first described by the German physiologist Ewald Hering in the late 19th century.

Hering proposed the opponent-process theory of color vision, which posits that the human visual system processes color information through three pairs of opponent channels: red-green, blue-yellow, and black-white. According to this theory, the visual system uses the relative activity of these opponent channels to perceive color, which allows it to maintain color constancy despite changes in the lighting conditions.

Hering’s theory of color vision and color constancy has been influential in the field of color science and continues to be studied by researchers in the fields of psychology, neuroscience, and computer vision.

wald Hering was a German physiologist and psychologist who lived from 1834 to 1918. He is best known for his work on the physiology of the senses and the physiology of the nervous system. He was one of the first to study the physiology of the senses in a systematic manner, and he made important contributions to the understanding of color vision and color constancy.

Hering was a professor of physiology at the University of Prague and later at the University of Würzburg. He was a leading figure in the field of physiology in the late 19th century, and his work on the physiology of the senses was widely recognized and influential.

One of his key contributions was his opponent-process theory of color vision, which he proposed in 1878. This theory posits that the human visual system processes color information through three pairs of opponent channels: red-green, blue-yellow, and black-white. This theory has been very influential in the field of color science and is still widely accepted today.

In addition to his contributions to color science, Hering also made important contributions to the field of psychology, particularly in the areas of perception, memory, and attention.

References and Resources

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The Pinna Illusion

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Pinna Original

The Pinna Illusion is created by displaying a pattern of light and dark bars on a computer screen. The pattern appears to rotate, even though it is actually stationary.

The Pinna Illusion is similar to the Pinna-Brelstaff illusion, but it is created by the interaction between light and dark regions of the image, rather than bars.

Pinna Original
Pinna Illusion


Table of Contents

How does the Pinna Illusion work?

The Pinna illusion is a visual illusion that was discovered by Bruno Pinna, a cognitive scientist and researcher in the field of visual perception. The illusion is created by displaying a pattern of light and dark regions on a computer screen. The pattern appears to rotate, even though it is actually stationary.

The illusion works by exploiting the way our visual system processes information about motion. The brain uses a variety of cues, such as the relative motion of different parts of an image, to perceive motion. The Pinna illusion takes advantage of these cues by presenting an image that tricks the brain into perceiving rotation where there is none.

The illusion is created by the interaction between the light and dark regions of the image, which creates a sense of depth. The brain interprets the light and dark regions as if they were three-dimensional objects, and it uses the relative motion of the different parts of the image to perceive motion. The brain is tricked into perceiving rotation because the light and dark regions create the illusion of three-dimensional shapes that are moving relative to each other.

The Pinna illusion is one of the most powerful examples of kinetic illusions, and it is still not fully understood how it works. Some scientists have suggested that it may be related to the way the visual system processes information about the relative depth of different parts of an image, but more research is needed to fully understand the underlying mechanism of this illusion.

Version of the Pinna Illusion

The following are some alternate versions of the Pinna Illusion:

pinna-brelstaff illusion



pinna-brelstaff illusion



pinna-brelstaff illusion



Illusions like the Pinna Illusion

Kinetic illusions are visual illusions that involve motion. They work by exploiting the way our visual system processes information about motion. The brain uses a variety of cues, such as the relative motion of different parts of an image, to perceive motion.

Kinetic illusions take advantage of these cues by presenting images in a way that tricks the brain into perceiving motion where there is none, or perceiving motion in a different direction than what is actually happening

Some similar illusions are below:

The Fraser spiral illusion is an optical illusion that is characterized by the appearance of a spiral pattern made up of concentric circles.

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


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 barber pole illusion is an optical illusion that is characterized by the appearance of a spiral pattern on a vertically striped pole.


The Bezold Effect: This illusion is created by placing two or more colors next to each other, and the way they appear to change when they are close to one another.  

Bezold_Effect
from Wikimedia Commons


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


Discovery of the Pinna Illusion

The Pinna Illusion is a visual illusion that was discovered by Bruno Pinna, a cognitive scientist and researcher in the field of visual perception.

Bruno Pinna is an Italian psychologist, known for his research in visual perception and his discovery of the Pinna illusion. He is currently a full professor of psychology at the University of Cagliari, Italy.

Pinna’s research focuses on the study of visual perception, in particular, the way in which the brain processes visual information and how it is influenced by the context of the visual environment. He is best known for his discovery of the Pinna illusion, which demonstrates the role of context and the importance of the visual cues provided by the surrounding environment in our perception of an object.

Pinna has published numerous papers on visual perception and the Pinna illusion in scientific journals, and he is considered a leading expert in the field of visual perception. He is also a member of various scientific societies and has been invited to give lectures and presentations on his research at conferences and universities around the world.

References and Resources

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Pinna-Brelstaff Illusion

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pinna-brelstaff illusion

The Pinna-Brelstaff Illusion is a visual illusion that demonstrates the role of context and the importance of the visual cues provided by the surrounding environment in our perception of an object. It is an adaptation of the original Pinna illusion.

The illusion is created by displaying a pattern of light and dark bars on a computer screen. The pattern appears to rotate, even though it is actually stationary.

pinna-brelstaff illusion
Pinna-Brelstaff Illusion


Table of Contents

How does the Pinna-Brelstaff Illusion work?

The Pinna-Brelstaff illusion is a kinetic illusion that involves the perception of motion in a still image. It was discovered by two researchers, Bruno Pinna and Tim Brelstaff in 2001. The illusion is created by displaying a pattern of light and dark bars on a computer screen. The pattern appears to rotate, even though it is actually stationary.

The illusion is created by the interaction between the light and dark bars, which creates a sense of depth, and the way that the brain processes information about motion. The brain interprets the light and dark bars as if they were three-dimensional objects, and it uses the relative motion of the different parts of the image to perceive motion. The brain is tricked into perceiving rotation because the light and dark bars create the illusion of three-dimensional shapes that are moving relative to each other.

This illusion can be explained by the theory of “perception of relative motion” the brain relies on the relative motion of the parts of an image to perceive motion. The light and dark bars creates the illusion of 3D shapes that are moving relative to each other, this creates the perception of rotation.

Version of the Pinna-Brelstaff Illusion

The following are some alternate versions of the Pinna-Brelstaff Illusion:



pinna-brelstaff illusion



pinna-brelstaff illusion



Illusions like the Pinna-Brelstaff Illusion

Kinetic illusions are visual illusions that involve motion. They work by exploiting the way our visual system processes information about motion. The brain uses a variety of cues, such as the relative motion of different parts of an image, to perceive motion.

Kinetic illusions take advantage of these cues by presenting images in a way that tricks the brain into perceiving motion where there is none, or perceiving motion in a different direction than what is actually happening

Some similar illusions are below:

The Fraser spiral illusion is an optical illusion that is characterized by the appearance of a spiral pattern made up of concentric circles.

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


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 barber pole illusion is an optical illusion that is characterized by the appearance of a spiral pattern on a vertically striped pole.


The Bezold Effect: This illusion is created by placing two or more colors next to each other, and the way they appear to change when they are close to one another.  

Bezold_Effect
from Wikimedia Commons


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


Discovery of the Pinna-Brelstaff Illusion

It was discovered by two researchers, Bruno Pinna and Tim Brelstaff in 2001.

Bruno Pinna is an Italian psychologist, known for his research in visual perception and his discovery of the Pinna illusion. He is currently a full professor of psychology at the University of Cagliari, Italy.

Pinna’s research focuses on the study of visual perception, in particular, the way in which the brain processes visual information and how it is influenced by the context of the visual environment. He is best known for his discovery of the Pinna illusion, which demonstrates the role of context and the importance of the visual cues provided by the surrounding environment in our perception of an object.

Pinna has published numerous papers on visual perception and the Pinna illusion in scientific journals, and he is considered a leading expert in the field of visual perception. He is also a member of various scientific societies and has been invited to give lectures and presentations on his research at conferences and universities around the world.

References and Resources

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Moving Color Contrast

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Perhaps one of the coolest examples of how color contrast illusions can work. If interested, a deep dive on the simultaneous contrast illusion follows.

A Deep Dive on the Simultaneous Contrast Illusion

The simultaneous contrast illusion is a visual effect that occurs when the perception of a color is affected by the colors of the surrounding area.

The illusion creates the appearance of a change in the color of an object, even though the actual color of the object remains constant.

Simultaneous Contrast Effect
The center green dot is the same on both sides, but the surrounding color changes the perception


Table of Contents

How does the Simultaneous Contrast Illusion work?

The simultaneous contrast illusion is a visual effect that occurs when the perception of a color is affected by the colors of the surrounding area. The illusion creates the appearance of a change in the color of an object, even though the actual color of the object remains constant.

The effect is caused by the way the human visual system processes color. When the eyes are fixated on a point, the visual system tends to average the color of the surrounding area. This can cause the visual system to perceive the color of an object as being different from its actual color, depending on the colors of the surrounding area. For example, a gray square placed on a white background will appear lighter than the same gray square placed on a black background, even though the gray square is the same color in both cases.

The simultaneous contrast illusion can be used in art and design to create the illusion of depth or movement, as well as to make certain elements stand out. It is also used in fields such as vision science and cognitive psychology, to understand how visual perception works.

In summary, the simultaneous contrast illusion is a visual effect that occurs when the perception of a color is affected by the colors of the surrounding area, creating the appearance of a change in the color of an object, even though the actual color of the object remains constant.

Versions of the Simultaneous Contrast Illusion

The following is an alternate version of the Simultaneous Contrast Illusion:



Simultaneous Contrast Effect




Simultaneous Contrast Effect



Simultaneous Contrast Effect



Simultaneous Contrast Effect


Illusions like the Simultaneous Contrast Illusion

Color illusions work by exploiting the way that the human visual system processes color and light. The human eye is able to detect light in the visible spectrum, which consists of different wavelengths of light that correspond to different colors. The brain then interprets this information to create our perception of color. However, the way the brain perceives color is not always a perfect representation of the physical reality.

There are several factors that can influence the way that the visual system processes color and light, which can lead to the perception of illusions. These factors include:

Contrast: The way that the brain perceives color can be influenced by the surrounding colors and patterns. High-contrast borders around an area of color can cause the brain to interpret the color as spreading or “bleeding” beyond the actual boundaries of the object.

Lighting conditions: The way that the brain perceives color can also be affected by the lighting conditions. For example, when an object is viewed in bright light, the eye’s color receptors may become fatigued, causing the brain to perceive colors differently than they actually are.

Color adaptation: The brain adapts to the colors that we see over time, which can influence the perception of color. For example, if an individual looks at a red object for an extended period of time, the brain will adapt to the red, and when that person looks at a white object, it will appear to have a pinkish hue.

Color constancy: The brain is able to adjust the perception of color based on the context in which it is viewed. This can create illusions where the same color appears to be different depending on the surrounding colors.

Shape use: Some illusions like the Hermann grid illusion or the Cafe Wall illusion, use specific patterns and shapes to manipulate the perception of color and shape.

Some related illusions include the following:

The Neon Color Spreading illusion refers to the visual phenomenon where an area of color appears to spread or “bleed” beyond its intended boundaries.

Neon Color Spreading
From Wikimedia Commons

The Bezold Effect: This illusion is created by placing two or more colors next to each other, and the way they appear to change when they are close to one another.  

Bezold_Effect
from Wikimedia Commons

The Mach Band Illusion: This illusion is created by the way the brain perceives edges of an object. When an object has a gradient of color, the edges of the object appear to be darker or lighter than they actually are.

Mach Bands Animation
From Wikimedia Commons

The Chevreul Illusion: This illusion is created by the way the brain perceives edges of an object. When the edges of an object are surrounded by a contrasting color, the edges appear to be a different color than they actually are. Chevreul’s illusion is similar to Mach bands, but they work in different ways. Chevreul’s illusion is an effect on the perception of hue, while Mach bands is an effect on the perception of brightness.

chevreul

The Hermann Grid Illusion: This illusion is created by the way the brain perceives intersections of lines. When the intersections of a grid of lines are viewed, small gray dots appear at the intersections, even though they are not actually there.



Hermann Grid

The Watercolor Illusion: This illusion is created by the way the brain perceives edges of an object. When an object is surrounded by a colored halo, the object appears to have a different color than it actually does.

Watercolor Illusion


The Ishihara Illusion: This illusion is created by the way the brain perceives colors. When a color is surrounded by a contrasting color, the brain perceives the color to be different than it actually is.

Ishihara Plate 9
From Wikimedia Commons

The flash lag illusion is a visual illusion that is based on the perception of the temporal relationship between a moving object and a flash of light. The illusion occurs when a moving object is followed by a sudden flash of light, and the perceived location of the flash appears to be behind the actual location of the object.

Flash Lag
From Wikimedia Commons

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


Discovery of the Simultaneous Contrast Illusion

The illusion is named after Michel Eugène Chevreul, a French chemist and physicist, who first described it in 1839 in his book “The Laws of Contrast of Colors”.

Michel Eugène Chevreul (1786-1889) was a French chemist and physicist who made significant contributions to the field of color theory. He is best known for his work on the nature of color, and the relationship between colors, which he described in his book “The Laws of Contrast of Colors” (1839). He was one of the first to study the perception of color, and the effect of surrounding colors on the perception of a given color. He is particularly known for the discovery of the Chevreul Illusion, a visual effect that creates the appearance of movement or “flicker” in a pattern of alternating light and dark bands.

Chevreul’s work on color perception had a significant influence on the development of color theory, and continues to be studied in fields such as art, design, and psychology. He was also a researcher in other scientific fields such as soap-making and oils, and he developed a method for the analysis of fats and oils, which was widely used in the food industry. He was a professor of chemistry in Paris and a member of the French Academy of Sciences

References and Resources

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Persistence of Vision

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Persistence of Vision

Persistence of vision is the phenomenon by which the brain continues to perceive an image even after the image is no longer present.

This occurs because the cells in the retina, called rods and cones, take a brief period of time to “reset” after being stimulated.

As a result, when an image is removed, these cells continue to send signals to the brain for a short period of time, creating the illusion that the image is still present.

Persistence of vision is the scientific explanation behind the afterimage illusion, as well as the illusion of motion in moving pictures such as films and animations.

Persistence of Vision
Persistence of Vision


Table of Contents


How does the Persistence of Vision work?

Persistence of vision works by the way our eyes and brain process visual information. When light enters our eyes, it is absorbed by cells in the retina called rods and cones. These cells then send electrical signals to the brain, which interprets these signals as visual information. The brain is able to process images very quickly, and can hold onto an image for a brief period of time even after it is no longer present. This is known as the “persistence of vision.”

When we watch a movie or animation, for example, the images are presented to us in rapid succession. The brain combines these images and interprets them as a single, continuous image, creating the illusion of motion. This is due to persistence of vision.

Similarly, when we see a light being turned on and off quickly, the brain combines these images and interprets them as a single, continuous light. This is also due to persistence of vision.

Persistence of vision also plays a role in other visual phenomena, such as afterimages, optical illusions and other types of illusions, as well as in some cases of visual hallucinations.

It’s worth noting that persistence of vision is not a unique property of human vision, many animals have this ability as well.

Versions of the Persistence of Vision

There are many examples of persistence of vision in everyday life. Some of these include:

Moving pictures: When we watch films or animations, the rapid succession of still images creates the illusion of motion. This is due to persistence of vision.

Flickering lights: When we see a light being turned on and off quickly, it can create the illusion of a continuous glow. This is also due to persistence of vision.

Spin art: When a spinning object is decorated with different colors, the colors appear to blend together and create new colors. This is due to persistence of vision.

Fireworks: The bright trails left by fireworks are caused by persistence of vision, as the brain continues to see the light even after the firework has exploded.

Afterimages: When we look at a bright light, or an image for an extended period of time, and then look away, we can see an afterimage of that image or light. This is also caused by persistence of vision.

The following are some other examples of Persistence of Vision

Persistence of Vision
Fireflies at Night – Persistent Light Trail


Persistence of Vision
Sparkler at Night – Persistent Tail


Persistence of Vision




After Image afterimage


After Image afterimage





Illusions like Persistence of Vision

Some related illusions include the following:

Afterimage Illusion

The afterimage illusion is a type of visual illusion in which an image continues to appear in the observer’s visual field after the original stimulus has been removed.


After Image afterimage

The Checker Shadow Illusion is created by a checkerboard pattern composed of squares with different luminance values, the squares that are not directly illuminated by the light source appear darker than the illuminated squares, creating the illusion of shadows.

Edelson-Checker_shadow_illusion
Checker Shadow Illusion


The simultaneous contrast illusion is a visual effect that occurs when the perception of a color is affected by the colors of the surrounding area.

The illusion creates the appearance of a change in the color of an object, even though the actual color of the object remains constant.


Simultaneous Contrast Effect
The center green dot is the same on both sides, but the surrounding color changes the perception


The Neon Color Spreading illusion refers to the visual phenomenon where an area of color appears to spread or “bleed” beyond its intended boundaries.

Neon Color Spreading
From Wikimedia Commons


The Bezold Effect: This illusion is created by placing two or more colors next to each other, and the way they appear to change when they are close to one another.  

Bezold_Effect
from Wikimedia Commons


The Cornsweet illusion is a classic example of a brightness illusion, which is an illusion in which two areas that are physically the same brightness appear to be different in brightness.

Cornsweet illusion
Cornsweet illusion

The Chubb illusion is based on the perception of brightness and can be observed when a small bright patch is surrounded by a larger dark area, the small bright patch will appear brighter than the same patch surrounded by a bright area.

Chubb Illusion

The Watercolor Illusion: This illusion is created by the way the brain perceives edges of an object. When an object is surrounded by a colored halo, the object appears to have a different color than it actually does.

Watercolor 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


Discovery of the Persistence of Vision

The phenomenon of persistence of vision, has been known for centuries.

The ancient Greeks and Romans were aware of the phenomenon, and it was also described by the ancient Chinese and Arab scholars.

The earliest scientific study of afterimages was done by the German scientist Hermann von Helmholtz in the 19th century.

He published a book in 1867 titled “Handbook of Physiological Optics” which gave a detailed explanation of the phenomenon, including the theory that afterimages were caused by the retina’s sensitivity to light.

This study is considered as one of the earliest and most comprehensive explanations of the effect.

References and Resources

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Afterimage Illusion

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After Image afterimage

The afterimage illusion is a type of visual illusion in which an image continues to appear in the observer’s visual field after the original stimulus has been removed.

This can occur due to the persistence of neural activity in the visual system, and can take the form of a positive afterimage (an image that is the same color as the original stimulus) or a negative afterimage (an image that is the opposite color of the original stimulus).

Afterimage illusions can be caused by a variety of factors, including the duration and intensity of the original stimulus, and the observer’s individual visual characteristics.

Stare at the image below for 30 seconds and then look to a white surface

After Image afterimage
Afterimage illusion


Table of Contents


How does the Afterimage Illusion work?

The afterimage illusion occurs when an image is viewed for a prolonged period of time and then removed, causing a negative image to appear in the viewer’s mind.

This happens because the cells in the retina, called rods and cones, become fatigued from being stimulated by the same image for a prolonged period.

When the image is removed, these cells continue to send signals to the brain, creating the illusion of a negative image. The phenomenon is also known as a persistence of vision.

Persistence of vision is the phenomenon by which the brain continues to perceive an image even after the image is no longer present. This occurs because the cells in the retina, called rods and cones, take a brief period of time to “reset” after being stimulated. As a result, when an image is removed, these cells continue to send signals to the brain for a short period of time, creating the illusion that the image is still present.

Persistence of vision is the scientific explanation behind the afterimage illusion, as well as the illusion of motion in moving pictures such as films and animations.

Negative vs. Positive Afterimages

A negative afterimage is an optical illusion that occurs when an image is viewed for a prolonged period of time and then removed, causing a reversed or “negative” version of the image to appear in the viewer’s mind.

This happens because the cells in the retina, called rods and cones, become fatigued from being stimulated by the same image for a prolonged period. When the image is removed, these cells continue to send signals to the brain, creating the illusion of a negative image.

The colors in the afterimage are also typically the opposite or complementary colors of the original image viewed. For example, if the original image was red, the afterimage will be green.

A positive afterimage is an optical illusion that occurs when an image is viewed for a prolonged period of time, and then removed, causing a similar version of the image to appear in the viewer’s mind, but with different colors.

This happens because the cells in the retina, called rods and cones, become fatigued from being stimulated by the same image for a prolonged period. When the image is removed, these cells continue to send signals to the brain, creating the illusion of a positive image.

The colors in the afterimage are also typically the similar colors of the original image viewed, but with different intensity or brightness.

Versions of the Afterimage Illusion

The following are an alternate versions of the Afterimage Illusion:



After Image afterimage



After Image afterimage



After Image afterimage
Stare at the center of a single circle for 30 seconds then divert to a white surface. Experiment with the different colors.






Illusions like the Afterimage Illusion

Some related illusions include the following:

The Checker Shadow Illusion is created by a checkerboard pattern composed of squares with different luminance values, the squares that are not directly illuminated by the light source appear darker than the illuminated squares, creating the illusion of shadows.

Edelson-Checker_shadow_illusion
Checker Shadow Illusion


The simultaneous contrast illusion is a visual effect that occurs when the perception of a color is affected by the colors of the surrounding area.

The illusion creates the appearance of a change in the color of an object, even though the actual color of the object remains constant.


Simultaneous Contrast Effect
The center green dot is the same on both sides, but the surrounding color changes the perception


The Neon Color Spreading illusion refers to the visual phenomenon where an area of color appears to spread or “bleed” beyond its intended boundaries.

Neon Color Spreading
From Wikimedia Commons


The Bezold Effect: This illusion is created by placing two or more colors next to each other, and the way they appear to change when they are close to one another.  

Bezold_Effect
from Wikimedia Commons


The Cornsweet illusion is a classic example of a brightness illusion, which is an illusion in which two areas that are physically the same brightness appear to be different in brightness.

Cornsweet illusion
Cornsweet illusion

The Chubb illusion is based on the perception of brightness and can be observed when a small bright patch is surrounded by a larger dark area, the small bright patch will appear brighter than the same patch surrounded by a bright area.

Chubb Illusion

White’s illusion is a visual phenomenon in which two identical gray bars are placed on a background of alternating black and white stripes.

The gray bars appear to be different shades of gray, with the one on the white stripes appearing lighter than the one on the black stripes.

In the image below, both gray bars have the exact same color.

White's Illusion
White’s Illusion

The Watercolor Illusion: This illusion is created by the way the brain perceives edges of an object. When an object is surrounded by a colored halo, the object appears to have a different color than it actually does.

Watercolor 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


Discovery of the Afterimage Illusion

The phenomenon of afterimages, also known as persistence of vision, has been known for centuries.

The ancient Greeks and Romans were aware of the phenomenon, and it was also described by the ancient Chinese and Arab scholars.

The earliest scientific study of afterimages was done by the German scientist Hermann von Helmholtz in the 19th century.

He published a book in 1867 titled “Handbook of Physiological Optics” which gave a detailed explanation of the phenomenon, including the theory that afterimages were caused by the retina’s sensitivity to light.

This study is considered as one of the earliest and most comprehensive explanations of the afterimage effect.

References and Resources

Check out our complete list of illusions.

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Binocular Rivalry

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Binocular rivalry

Binocular rivalry is a phenomenon that occurs when slightly different images are presented to each eye simultaneously.

The brain is unable to fuse the two images into a single, coherent image, and instead alternates between perceiving one image and then the other.

This can cause the perceived image to flicker or change back and forth between the two images.

Binocular rivalry
Binocular Rivalry


Table of Contents


How does Binocular Rivalry work?

Binocular rivalry occurs when slightly different images are presented to each eye simultaneously. The brain receives input from each eye, but is unable to fuse the two images into a single, coherent image. Instead, it alternates between perceiving one image and then the other.

The exact mechanism by which the brain alternates between the two images is not fully understood, but it is thought to involve neural competition between the two eyes’ input at the level of the primary visual cortex. This competition is thought to be mediated by inhibitory interactions between neurons that are sensitive to the different images.

It’s also been proposed that the alternation between the two images is not purely random, but rather depends on the features of the images, such as their contrast, spatial frequency, and semantic meaning.

Binocular rivalry can be used to study the neural mechanisms of visual perception, depth perception and binocularity. It has been used to investigate the role of attention, top-down processing and adaptation in the perception of rivaling stimuli.

It’s important to note that binocular rivalry is different from binocular summation, which is the phenomenon that occurs when the visual information from the two eyes is combined to produce a single, more robust image.

Difference Between Monocular Rivalry and Binocular Rivalry

Monocular rivalry and binocular rivalry are similar in that they both involve the perception of conflicting images, but they differ in the way the images are presented to the eyes.

Monocular rivalry occurs when different images are presented to each eye simultaneously. In this case, the brain receives input from each eye, but is unable to process both images at the same time, so it alternates between perceiving one image and then the other.

Binocular rivalry, on the other hand, occurs when the same image is presented to both eyes, but the images are slightly different in some way, such as a small shift in position or a slight change in contrast. In this case, the brain is unable to fuse the two images into a single, coherent image, and instead alternates between perceiving one image and then the other.

The neural mechanisms that underlie monocular and binocular rivalry are thought to be similar, but the specific processes that lead to the perception of the rivaling images may differ. Monocular rivalry is often used to study visual perception and the brain, while binocular rivalry is used to study the neural mechanisms of depth perception, stereopsis and binocularity.

Versions of the Binocular Rivalry

The following are an alternate versions of the Binocular Rivalry:



Binocular rivalry






Binocular rivalry
An image demonstrating binocular rivalry. If you view the image with red-cyan 3D glasses, the text will alternate between Red and Blue
From Wikimedia Commons



Binocular rivalry
Binocular rivalry. If you view the image with red-cyan 3D glasses, the angled Warp and weft will alternate between the Red and the Blue lines.
From Wikimedia Commons



Illusions like Bionocular Rivalry

Binocular rivalry is a type of perceptual illusion. Perceptual illusions are those that involve the brain’s interpretation of sensory input and can include visual, auditory, and other types of illusions.

In the case of monocular rivalry, the brain is interpreting the input from each eye differently, leading to the perception of an image that is different from the physical image presented to the eye.

Some related illusions include the following:

Monocular rivalry is a phenomenon that occurs when different images are presented to each eye simultaneously. The brain is unable to process both images at the same time, so it alternates between perceiving one image and then the other.

The Checker Shadow Illusion is created by a checkerboard pattern composed of squares with different luminance values, the squares that are not directly illuminated by the light source appear darker than the illuminated squares, creating the illusion of shadows.

Edelson-Checker_shadow_illusion
Checker Shadow Illusion

The simultaneous contrast illusion is a visual effect that occurs when the perception of a color is affected by the colors of the surrounding area.

The illusion creates the appearance of a change in the color of an object, even though the actual color of the object remains constant.

Simultaneous Contrast Effect
The center green dot is the same on both sides, but the surrounding color changes the perception

The Neon Color Spreading illusion refers to the visual phenomenon where an area of color appears to spread or “bleed” beyond its intended boundaries.

Neon Color Spreading
From Wikimedia Commons

The Bezold Effect: This illusion is created by placing two or more colors next to each other, and the way they appear to change when they are close to one another.  

Bezold_Effect
from Wikimedia Commons

The Chubb illusion is based on the perception of brightness and can be observed when a small bright patch is surrounded by a larger dark area, the small bright patch will appear brighter than the same patch surrounded by a bright area.

Chubb Illusion


The Chevreul Illusion: This illusion is created by the way the brain perceives edges of an object. When the edges of an object are surrounded by a contrasting color, the edges appear to be a different color than they actually are. Chevreul’s illusion is similar to Mach bands, but they work in different ways. Chevreul’s illusion is an effect on the perception of hue, while Mach bands is an effect on the perception of brightness.

chevreul

White’s illusion is a visual phenomenon in which two identical gray bars are placed on a background of alternating black and white stripes.

The gray bars appear to be different shades of gray, with the one on the white stripes appearing lighter than the one on the black stripes.

In the image below, both gray bars have the exact same color.

White's Illusion
White’s Illusion

The Cornsweet illusion is a classic example of a brightness illusion, which is an illusion in which two areas that are physically the same brightness appear to be different in brightness.

Cornsweet illusion
Cornsweet illusion

The Watercolor Illusion: This illusion is created by the way the brain perceives edges of an object. When an object is surrounded by a colored halo, the object appears to have a different color than it actually does.

Watercolor 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


Discovery of Binocular Rivalry

The phenomenon of binocular rivalry has been known for centuries, and has been observed and described by many scientists and philosophers. However, it wasn’t until the late 19th and early 20th centuries that the phenomenon began to be studied systematically.

One of the first scientists to study binocular rivalry in a systematic way was the psychologist Joseph Jastrow. He published several articles in the late 19th century describing the phenomenon of binocular rivalry and the different ways it can manifest.

In the early 20th century, the psychologist Edgar Rubin made significant contributions to the study of binocular rivalry and is often credited with introducing the term “binocular rivalry” to describe the phenomenon. He published several articles describing his findings on binocular rivalry, and his work on the topic is still widely cited today.

Other scientists like the physiologist and psychologist Ludimar Hermann, who in 1870 proposed that the perception of one eye’s image is suppressed by the other eye’s image, also contributed to the understanding of binocular rivalry.

Overall, many scientists have contributed to the discovery and understanding of binocular rivalry and it’s still an active area of research.

References and Resources

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Monocular Rivalry

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Monocular Rivalry

Monocular rivalry is a phenomenon that occurs when different images are presented to each eye simultaneously.

The brain is unable to process both images at the same time, so it alternates between perceiving one image and then the other.

This can cause the perceived image to flicker or change back and forth between the two images.

Monocular Rivalry
Monocular Rivalry


Table of Contents


How does Monocular Rivalry work?

Monocular rivalry occurs when different images are presented to each eye simultaneously.

The brain receives input from each eye, but is unable to process both images at the same time, so it alternates between perceiving one image and then the other.

The exact mechanism by which the brain alternates between the two images is not fully understood.

It is thought to involve inhibitory processes in the visual cortex, which suppress the perception of one image while allowing the perception of the other.

This inhibition can occur at different levels of the visual system, from the retina to the higher-level visual areas of the brain.

It’s also been proposed that the alternation between the two images is not purely random, but rather depends on the features of the images, such as their contrast, spatial frequency, and semantic meaning.

Monocular rivalry can be used to study the neural mechanisms of visual perception and how the brain interprets and constructs visual information.

Difference Between Monocular Rivalry and Binocular Rivalry

Monocular rivalry and binocular rivalry are similar in that they both involve the perception of conflicting images, but they differ in the way the images are presented to the eyes.

Monocular rivalry occurs when different images are presented to each eye simultaneously. In this case, the brain receives input from each eye, but is unable to process both images at the same time, so it alternates between perceiving one image and then the other.

Binocular rivalry, on the other hand, occurs when the same image is presented to both eyes, but the images are slightly different in some way, such as a small shift in position or a slight change in contrast. In this case, the brain is unable to fuse the two images into a single, coherent image, and instead alternates between perceiving one image and then the other.

The neural mechanisms that underlie monocular and binocular rivalry are thought to be similar, but the specific processes that lead to the perception of the rivaling images may differ. Monocular rivalry is often used to study visual perception and the brain, while binocular rivalry is used to study the neural mechanisms of depth perception, stereopsis and binocularity.

Versions of the Monocular Rivalry

The following are an alternate versions of the Monocular Rivalry:



Monocular Rivalry


Monocular Rivalry



Illusions like the Monocular Rivalry

Monocular rivalry is a type of perceptual illusion. Perceptual illusions are those that involve the brain’s interpretation of sensory input and can include visual, auditory, and other types of illusions.

In the case of monocular rivalry, the brain is interpreting the input from each eye differently, leading to the perception of an image that is different from the physical image presented to the eye.

Some related illusions include the following:

The Checker Shadow Illusion is created by a checkerboard pattern composed of squares with different luminance values, the squares that are not directly illuminated by the light source appear darker than the illuminated squares, creating the illusion of shadows.

Edelson-Checker_shadow_illusion
Checker Shadow Illusion

The simultaneous contrast illusion is a visual effect that occurs when the perception of a color is affected by the colors of the surrounding area.

The illusion creates the appearance of a change in the color of an object, even though the actual color of the object remains constant.

Simultaneous Contrast Effect
The center green dot is the same on both sides, but the surrounding color changes the perception

The Neon Color Spreading illusion refers to the visual phenomenon where an area of color appears to spread or “bleed” beyond its intended boundaries.

Neon Color Spreading
From Wikimedia Commons

The Bezold Effect: This illusion is created by placing two or more colors next to each other, and the way they appear to change when they are close to one another.  

Bezold_Effect
from Wikimedia Commons

The Mach Band Illusion: This illusion is created by the way the brain perceives edges of an object. When an object has a gradient of color, the edges of the object appear to be darker or lighter than they actually are.

Mach Bands Animation
From Wikimedia Commons

The Chubb illusion is based on the perception of brightness and can be observed when a small bright patch is surrounded by a larger dark area, the small bright patch will appear brighter than the same patch surrounded by a bright area.

Chubb Illusion


The Chevreul Illusion: This illusion is created by the way the brain perceives edges of an object. When the edges of an object are surrounded by a contrasting color, the edges appear to be a different color than they actually are. Chevreul’s illusion is similar to Mach bands, but they work in different ways. Chevreul’s illusion is an effect on the perception of hue, while Mach bands is an effect on the perception of brightness.

chevreul

White’s illusion is a visual phenomenon in which two identical gray bars are placed on a background of alternating black and white stripes.

The gray bars appear to be different shades of gray, with the one on the white stripes appearing lighter than the one on the black stripes.

In the image below, both gray bars have the exact same color.

White's Illusion
White’s Illusion

The Cornsweet illusion is a classic example of a brightness illusion, which is an illusion in which two areas that are physically the same brightness appear to be different in brightness.

Cornsweet illusion
Cornsweet illusion

The Watercolor Illusion: This illusion is created by the way the brain perceives edges of an object. When an object is surrounded by a colored halo, the object appears to have a different color than it actually does.

Watercolor 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


Discovery of Monocular Rivalry

The phenomenon of monocular rivalry has been known for centuries, and has been observed and described by many scientists and philosophers. However, it wasn’t until the late 19th and early 20th centuries that the phenomenon began to be studied systematically.

One of the first scientists to study monocular rivalry in a systematic way was the physiologist and psychologist Franz Christian Boll who in 1833 described the phenomenon of rivaling perceptions in his book “On the physiological causes of the illusion of colors”.

Later, in the late 19th century, the psychologist Joseph Jastrow made detailed observations of monocular rivalry, and published several articles describing his findings.

In the early 20th century, the psychologist Edgar Rubin made significant contributions to the study of monocular rivalry, and is often credited with introducing the term “monocular rivalry” to describe the phenomenon. He published several articles describing his findings on monocular rivalry, and his work on the topic is still widely cited today.

Overall, many scientists have contributed to the discovery and understanding of monocular rivalry and it’s still a active area of research.

References and Resources

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Cornsweet Illusion

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Cornsweet illusion

The Cornsweet illusion is a classic example of a brightness illusion, which is an illusion in which two areas that are physically the same brightness appear to be different in brightness.

The Cornsweet illusion is created by a gradual change in brightness between two areas, such as a transition from a dark area to a light area. The brain interprets the transition as a difference in brightness, even though the two areas are physically the same brightness.

Cornsweet illusion
Cornsweet illusion


Table of Contents


How does the Cornsweet Illusion work?

The Cornsweet illusion works by taking advantage of the way our visual system processes visual information. The visual system is more sensitive to changes in brightness at the borders of an object than to the brightness of the object itself.

In the Cornsweet illusion, there is a gradual change in brightness between two areas, such as a transition from a dark area to a light area. The brain interprets the transition as a difference in brightness, even though the two areas are physically the same brightness.

The way it works is that the visual system is sensitive to edges and it tends to exaggerate the brightness difference at the border between two adjacent regions. The brain tends to perceive the brightness of one area based on the brightness of the adjacent area, which causes the illusion of a difference in brightness.

Additionally, the visual system is sensitive to the relative brightness of an area, rather than its absolute brightness. The brain compares the relative brightness of an area to the surrounding areas, this causes the brain to perceive the brighter area as less bright and the darker area as brighter, than they actually are.

The Cornsweet illusion is important in the field of visual perception and cognitive psychology because it provides insight into how the brain processes visual information and how it interprets brightness. It also plays a role in areas such as computer graphics and image processing, where it is used to create the illusion.

Versions of the Cornsweet Illusion

The following are an alternate versions of the Cornsweet Illusion:



Cornsweet illusion
Both Sides are the Same Color


Cornsweet illusion
Both Sides are the Same Color


Cornsweet illusion
Both Sides are the Same Color






Illusions like the Cornsweet Illusion

The Cornsweet illusion is a type of visual illusion known as a brightness illusion. A brightness illusion is an illusion in which two areas that are physically the same brightness appear to be different in brightness.

Brightness illusions are important in the field of visual perception and cognitive psychology because they provide insight into how the brain processes visual information and how it interprets brightness. They also play a role in areas such as computer graphics and image processing, where they are used to create the illusion of depth and texture.

Some related illusions include the following:

The Checker Shadow Illusion is created by a checkerboard pattern composed of squares with different luminance values, the squares that are not directly illuminated by the light source appear darker than the illuminated squares, creating the illusion of shadows.

Edelson-Checker_shadow_illusion
Checker Shadow Illusion

The simultaneous contrast illusion is a visual effect that occurs when the perception of a color is affected by the colors of the surrounding area.

The illusion creates the appearance of a change in the color of an object, even though the actual color of the object remains constant.

Simultaneous Contrast Effect
The center green dot is the same on both sides, but the surrounding color changes the perception

The Neon Color Spreading illusion refers to the visual phenomenon where an area of color appears to spread or “bleed” beyond its intended boundaries.

Neon Color Spreading
From Wikimedia Commons

The Bezold Effect: This illusion is created by placing two or more colors next to each other, and the way they appear to change when they are close to one another.  

Bezold_Effect
from Wikimedia Commons

The Mach Band Illusion: This illusion is created by the way the brain perceives edges of an object. When an object has a gradient of color, the edges of the object appear to be darker or lighter than they actually are.

Mach Bands Animation
From Wikimedia Commons

The Chubb illusion is based on the perception of brightness and can be observed when a small bright patch is surrounded by a larger dark area, the small bright patch will appear brighter than the same patch surrounded by a bright area.

Chubb Illusion


The Chevreul Illusion: This illusion is created by the way the brain perceives edges of an object. When the edges of an object are surrounded by a contrasting color, the edges appear to be a different color than they actually are. Chevreul’s illusion is similar to Mach bands, but they work in different ways. Chevreul’s illusion is an effect on the perception of hue, while Mach bands is an effect on the perception of brightness.

chevreul

White’s illusion is a visual phenomenon in which two identical gray bars are placed on a background of alternating black and white stripes.

The gray bars appear to be different shades of gray, with the one on the white stripes appearing lighter than the one on the black stripes.

In the image below, both gray bars have the exact same color.

White's Illusion
White’s Illusion

The Watercolor Illusion: This illusion is created by the way the brain perceives edges of an object. When an object is surrounded by a colored halo, the object appears to have a different color than it actually does.

Watercolor 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


Discovery of the Cornsweet Illusion

The Cornsweet illusion is a visual illusion that was first described by Tom Cornsweet in 1960.

Tom Cornsweet was an American psychologist, known for his work in visual perception. He was a Professor of Psychology at the University of California, Berkeley, and a Fellow of the American Psychological Association. He is best known for his research on the physiology of visual perception and for his descriptions of visual phenomena such as the Cornsweet illusion.

Cornsweet published several papers on various topics related to visual perception, including the perception of brightness, color, and contrast. He is known for his work in the field of visual perception and cognitive psychology, he also worked on the perception of brightness and color, and on the perception of visual illusions.

He was a pioneering researcher in the field of visual perception, and his work continues to be influential in the field today. The Cornsweet illusion, which is named after him, is still widely used in the study of visual perception and cognitive psychology, as well as in areas such as computer graphics and image processing.

Cornsweet passed away in the late 90s, but his contributions to the field of visual perception and cognitive psychology are still widely recognized and respected today.

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Autostereograms

by
autostereogram Shark

An autostereogram is a type of image that appears to be a flat 2D image when viewed normally, but when viewed with a special technique, it appears to be a 3D image with depth and perspective.

Autostereograms are created by repeating a pattern of repeating elements, such as random dots, in such a way that the repeating elements at different depths in the image align with each other when viewed with the special technique. This creates the illusion of a 3D image.

The image below appears as a 2 dimensional flat image, but when viewed using one of the techniques mentioned below, a 3 dimensional shape appears.

autostereogram Shark
Autostereograms – Can You Spot the Hidden Shark?


Table of Contents

How does an Autostereogram work?

Autostereograms specifically are an example of a stereoscopic illusion, which is a type of optical illusion that creates the perception of depth and three dimensions in an image that is actually flat.

They are also known as “single image random dot stereograms (SIRDS)”.

To better see the 3D image in an autostereogram, there are a few techniques that can be used:

Wall-eyed or cross-eyed viewing: This technique involves diverging your eyes outward so that the left eye is focused on the right side of the image and the right eye is focused on the left side of the image. This can take some practice to get used to, but it is the most common way to view autostereograms.

Parallel viewing: Instead of crossing or diverging your eyes, you can also try to focus your eyes on a distant point in the room, while keeping them parallel to the image.

Focusing on a specific point: Some autostereograms have a “sweet spot” or a small dot or line that indicates where to focus your eyes. By focusing on that point, it may be easier to see the 3D image.

Viewing distance: The optimal viewing distance varies from person to person, but generally, the farther away from the image, the easier it is to see the 3D image.

Relaxation: It’s important to be relaxed while trying to see the 3D image, as tension in your eyes and face can make it harder to see the image.

It’s important to note that not everyone can see the 3D image in an autostereogram, and that’s normal. It depends on the individual’s visual perception and the structure of the image.

Versions of Autostereograms

The following are some alternate Autostereograms:



autostereograms-dolphins.jpg
Can you see the Dolphins?



autostereograms - two dinosaurs.gif
Can you see the two dinosaurs?



autostereograms-kangaroo.jpg
Can you see the Kangaroo?



Illusions like Autostereograms

Autostereograms specifically are an example of a stereoscopic illusion, which is a type of optical illusion that creates the perception of depth and three dimensions in an image that is actually flat. They are also known as “single image random dot stereograms (SIRDS)”.

Some related illusions are below:

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


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 barber pole illusion is an optical illusion that is characterized by the appearance of a spiral pattern on a vertically striped pole.


The Bezold Effect: This illusion is created by placing two or more colors next to each other, and the way they appear to change when they are close to one another.  

Bezold_Effect
from Wikimedia Commons


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


Discovery of Autostereograms

The invention of the autostereogram is credited to Dr. Bela Julesz, a Hungarian-born cognitive scientist and psychologist.

He first described the concept in his 1981 paper “Stereograms and the Brain” and later published a book “Textons, the elements of texture perception” which explained the theory behind autostereograms in detail.

He called them Random-Dot Stereograms (RDS) and was awarded a Turing award in 1995 for his contributions in this field of visual perception.

He also developed a computer program that could generate autostereograms, which allowed for the creation of more complex and realistic 3D images.

The term “Autostereogram” is derived from his original term “Random-Dot Stereograms (RDS)”.


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