Color Illusions

Trompe-L’œil

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Trompe-l'œil Capri

Trompe-l’œil is a French term that means “trick the eye.”

It refers to a style of art that uses realistic depictions of three-dimensional objects to create the illusion of depth and a life-like appearance.

Trompe-l’œil paintings and murals are often used to create the illusion of an extended space or to make a room appear larger than it actually is.

Trompe-l'œil Capri
Trompe-L’œil

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How does Trompe-L’œil work?

Trompe-l’œil works by creating the illusion of three-dimensional objects and space on a flat surface. The artist uses techniques such as perspective, shading, and texturing to create a highly realistic representation of the objects and to create the illusion of depth.

The techniques used in Trompe-l’œil take advantage of the way that the human visual system processes images. Our brains use cues such as size, shading, and perspective to determine the distance and depth of objects in our visual field. In Trompe-l’œil, the artist carefully manipulates these cues to create the illusion of depth and to make the objects appear to be physically present.

For example, in a Trompe-l’œil painting, the artist might use linear perspective to create the illusion of receding space. Objects that are closer to the viewer will appear larger, while objects that are further away will appear smaller. The artist will also use shading and texturing to create the illusion of depth and to make the objects appear more lifelike.

Trompe-l’œil works by tricking the brain into perceiving the two-dimensional image as a three-dimensional object, creating an illusion that is both fascinating and convincing. This is why Trompe-l’œil remains one of the most popular forms of visual illusion, and why it continues to be used today in various forms of art and design.

The technique of Trompe-l’œil has a long history, dating back to ancient Greece and Rome, and has been used throughout the centuries in various forms of art, including painting, sculpture, and architecture. In Trompe-l’œil, the artist uses a variety of techniques, such as perspective, shading, and texturing, to create the illusion of depth and to make the objects appear to be physically present.

Trompe-l’œil is often used in interior design, particularly for creating the illusion of an extended space or for creating a decorative feature on a wall or ceiling. It is also used in theatrical design, where it can be used to create the illusion of a larger stage or to create a realistic backdrop.

Trompe-l’œil is a popular art form that continues to be used today, and it remains one of the most fascinating and intriguing forms of visual illusion.

Versions of Trompe-L’œil

The following are some examples of Trompe-L’œil


Trompe-l'œil Copenhagen Zoo



Trompe-l'œil venice




Trompe-l'œil



Illusions like Trompe-L’œil

Trompe-l’œil is a type of optical illusion that creates the illusion of three-dimensional objects and space on a flat surface.

It falls under the category of visual perception illusions, which manipulate the way that the brain processes images to create an illusion that is different from reality. Trompe-l’œil is unique in that it uses realistic depictions of three-dimensional objects to create a highly convincing illusion of depth and physical presence.

Trompe-l’œil is often considered a form of representational art, as it creates a representation of three-dimensional objects. However, it is also a form of illusion, as the objects are not actually present in physical space, but are instead a two-dimensional representation that tricks the brain into perceiving them as three-dimensional.

Overall, Trompe-l’œil can be classified as a type of optical illusion, visual perception illusion, and representational art, depending on the context and the focus of the discussion.

Some similar illusions are as follows:

Forced perspective is a technique used in photography, architecture, and other visual arts to manipulate the perception of the size and distance of objects.

It creates the illusion of a larger or smaller object, or of one that is closer or farther away, by carefully controlling the angles, proportions, and placement of objects in the scene.

Forced Perspective
Forced Perspective

The Ponzo illusion is a type of visual illusion in which a pair of parallel lines, or a horizontal bar, appear to be of different lengths based on the presence of a converging or diverging set of lines, often resembling the converging parallel lines of a road or railway track, placed above and below them.

Ponzo illusion
The Ponzo Illusion

The Ebbinghaus illusion: This illusion is similar to the Delboeuf illusion but in this case the central circle appears larger when surrounded by smaller circles and smaller when surrounded by larger circles.

Ebbinghaus Illusion

The Delboeuf illusion is a perceptual illusion in which the perceived size of a circle is affected by the size of the surrounding circles.


The Occlusion illusion is a visual illusion where an object that is partially obscured by another object appears to be farther away than it actually is. This illusion is caused by the brain’s interpretation of the relative depth of the objects based on their relative size and position. This phenomenon is based on the visual cues that the brain uses to perceive depth, such as relative size, position, and overlap.

The occlusion 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

The moon illusions involves the perception of the Moon appearing larger when it is near the horizon compared to when it is high in the sky.

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.

All these illusions demonstrate that the perceived size of an object can be influenced by the context in which it is presented, and that the brain uses the size of the surrounding objects as a reference point to judge the size of the central object.


Discovery of Trompe-L’œil

The exact origin of Trompe-l’œil as an art form is unclear, but it is thought to have been developed and popularized in ancient Greece and Rome. The technique was used in various forms throughout the centuries, and it was later adopted and refined by Renaissance artists in Italy.

It is difficult to attribute the discovery of Trompe-l’œil to a single individual, as the technique has a long history and has been used by many artists and cultures over the centuries. However, some of the most famous Trompe-l’œil artists from the Renaissance include Italian painters such as Andrea Pozzo, Giuseppe Maria Crespi, and Pietro da Cortona. These artists used Trompe-l’œil to create highly realistic murals and frescoes that adorned the ceilings and walls of churches, palaces, and private residences.

Overall, while no one person can be credited with discovering Trompe-l’œil, the art form has a rich and fascinating history that has been shaped and influenced by many artists and cultures over the centuries.

References and Resources

Check out our complete list of illusions.

Silencing

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Sliencing

Silencing is a visual phenomenon where objects that change in luminance, hue, size, or shape appear to stop changing when they move. They “freeze” in place.

This illusion can be created through various means, such as flashing lights, or rapidly moving a stimulus back and forth.


Sliencing
Silencing – Once the dots start to move they appear to “freeze” in place even though the colors and hues continue to change


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How does Silencing work?

The Silencing Illusion works by exploiting the way our visual system processes motion.

Our visual system is sensitive to the rate at which an object changes position, and it tends to perceive objects as “stopped” or “frozen” when the rate of change in their position slows down or it can only handle so many sensory inputs at once, quieting or silencing some while others dominate.

Versions of Silencing

The following is a video that demonstrates Silencing:




Illusions like Silencing

The following are some illusions that are related to Silencing

Troxler’s fading, 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.



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 Silencing

t was discovered by Jordan Suchow and George Alvarez.

Jordan Suchow is an Associate Professor of Psychological and Brain Sciences at Dartmouth College. He is a researcher in the field of vision science and his research focuses on the perception of motion and the neural mechanisms underlying visual processing.

Dr. Suchow’s work has contributed to our understanding of how the brain processes visual information and how different aspects of visual processing, such as attention and prediction, influence the perception of motion. He has published several research papers in prestigious journals, and he has received numerous awards and grants for his work.

Overall, Dr. Jordan Suchow is a well-respected researcher in the field of vision science, and his work has helped to advance our understanding of how we perceive the world around us.

George A. Alvarez is an Associate Professor of Psychological and Brain Sciences at Harvard University. He is a researcher in the field of cognitive neuroscience and his research focuses on the neural mechanisms underlying visual perception and attention.

Dr. Alvarez’s work has made important contributions to our understanding of how the brain processes visual information, including the role of attention in shaping our perceptions of the world. He has published numerous research papers in prestigious journals and has received numerous awards and grants for his work.

Overall, Dr. George A. Alvarez is a well-respected researcher in the field of cognitive neuroscience, and his work has helped to advance our understanding of how the brain processes visual information and shapes our perceptions of the world.

References and Resources

Check out our complete list of illusions.

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Anamorphic Street Art

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Anamorphic street art

Anamorphic street art is a form of street art that uses optical illusion to create a three-dimensional image when viewed from a specific angle.

Anamorphic street art is often created by distorting the image, so that when it is viewed from a specific viewpoint, the image appears to be three-dimensional and in full perspective.

It is often seen as a way of transforming urban spaces into playful, interactive environments.

Anamorphic street art
Anamorphic Street Art



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How does Anamorphic Street Art?

Anamorphic street art works by manipulating the way our eyes perceive the image.

The artist distorts the image in such a way that it appears to be in the correct perspective when viewed from a specific viewpoint, typically at a specific angle or from a certain distance.

The use of perspective and forced-perspective techniques tricks the viewer’s eye into perceiving a three-dimensional image where there is actually only a flat surface.

The result is an optical illusion that creates the illusion of depth and volume, making the image appear to pop out of the wall or floor.

To create an anamorphic street art piece, the artist needs to carefully plan the placement of the artwork and the viewpoint from which it will be viewed to ensure the illusion is successful.

Versions of Anamorphic Street Art

The following are other examples of Anamorphic Street Art



Phantograms



Phantograms




Phantograms



Illusions like Anamorphic Street Art

Anamorphic Street Art are a form of stereograms, which are images that use the difference between the left and right eye views to create the illusion of depth and 3D objects.

Anamorphic street art is a type of perspective illusion that creates the illusion of a three-dimensional image on a two-dimensional surface by manipulating the way our eyes perceive the image.

The image is distorted in such a way that when viewed from a specific angle or distance, it appears to be in correct perspective and the illusion of depth and volume is created.

The illusion is achieved by using techniques such as forced perspective and manipulation of perspective, which trick the viewer’s eye into perceiving the image as three-dimensional.

Some related illusions include the following:

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.


Phantograms are 3D images that appear to float in space and can be viewed without special glasses or other aids. The term “Phantogram” is derived from the Greek words “phaneros,” meaning “visible,” and “gramma,” meaning “something written or drawn.”

Phantograms are created by taking two photos of an object from slightly different angles and then printing the images on a flat surface, such as a piece of paper or card. The two images are then viewed together, and the slight differences in perspective create the illusion of depth and the appearance of a floating 3D object.


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.



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.


Color constancy
Color Constancy


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).



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 Anamorphic Street Art

The origin of anamorphic street art is not well documented, and it’s unclear who created the first piece of anamorphic street art.

However, the use of anamorphosis in art dates back to the Renaissance, where artists such as Leonardo da Vinci and Albrecht Dürer used the technique to create illusions of depth in their drawings and paintings.

In the modern era, street artists around the world have been inspired by these earlier techniques and have started incorporating anamorphic illusions into their street art, turning urban spaces into interactive, playful environments.

Some well-known street artists who have used anamorphic techniques in their work include Eduardo Sanson, Eduardo Relero, and Felipe Pantone, among others.

References and Resources

Check out our complete list of illusions.

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Phantograms

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Phantograms

Phantograms are 3D images that appear to float in space and can be viewed without special glasses or other aids. The term “Phantogram” is derived from the Greek words “phaneros,” meaning “visible,” and “gramma,” meaning “something written or drawn.”

Phantograms are created by taking two photos of an object from slightly different angles and then printing the images on a flat surface, such as a piece of paper or card. The two images are then viewed together, and the slight differences in perspective create the illusion of depth and the appearance of a floating 3D object.

Phantograms can be created using specialized software or by hand and can be viewed by simply holding the printed image at the correct angle and looking at it with both eyes. They have been used in a variety of applications, including art, advertising, and education.

3D street art is one of the most well known types of Phantogram. Both 3D street art and Phantograms use the principle of perspective to create the illusion of depth and a three-dimensional appearance. 3D street art, also known as anamorphic street art, is created by painting an image on a flat surface in such a way that it appears to be three-dimensional when viewed from a specific angle.


Phantograms
3D Street Art – Phantogram Example



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How do Phantograms work?

Phantograms are 2D images that create the illusion of a 3D object or scene when viewed from a specific angle.

They work by manipulating the spatial relationship between the foreground and background elements in an image.

The foreground elements are arranged to converge towards a vanishing point and are distorted to give the illusion of depth, while the background elements are left undistorted.

When viewed from the intended angle, the image appears to pop out from the flat surface.

The effect is created by the interaction between the visual information in the image and the brain’s perception of depth and perspective.

Versions of the Phantograms

The following are other examples of Phantograms including a few 3D street examples and a classic image of a phantogram with chess pieces.



Phantograms



Phantograms




Phantograms





Illusions like Phantograms

Phantograms are a form of stereograms, which are images that use the difference between the left and right eye views to create the illusion of depth and 3D objects. In other words, phantograms are a type of optical illusion that tricks the brain into perceiving a 2D image as a 3D scene.

Some related illusions include the following:

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.



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.



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.


Color constancy
Color Constancy


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).



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 Phantograms

The origin of phantograms is not attributed to any single person or group.

The technique has been used for many centuries in various forms of art and design, and the basic principles behind phantograms and stereoscopy have been understood and described by artists, scientists, and mathematicians for a long time.

However, the term “phantogram” itself may have been coined more recently and its usage and definition have evolved over time in the field of photography and graphic design.

References and Resources

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Pepper’s Ghost

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Peppers Ghost

Pepper’s Ghost is an optical illusion used in theater and theme parks to create ghostly or translucent apparitions.

The illusion works by reflecting an object, usually a person, onto a transparent sheet (often made of glass or plastic) at a 45-degree angle, making it appear as if the object is floating in the air.

The transparent sheet is carefully positioned between the audience and the stage, making the reflection appear as a transparent ghost-like figure to the audience.

Peppers Ghost
Peppers Ghost

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How does Peppers Ghost work?

Pepper’s Ghost works by using a combination of reflection and perspective to create the illusion of a ghostly or translucent figure. Here’s how it works:

1: A partially transparent sheet of glass or plastic is placed at a 45-degree angle between the audience and the stage.

2: A hidden room or area is created behind the transparent sheet, where the object to be reflected is positioned. This could be a live actor or a physical object.

3: Bright lights are shone on the object, causing its reflection to be visible on the transparent sheet.

4: The audience sees the reflection on the transparent sheet as if it is floating in the air, due to the angle at which the sheet is positioned. The angle also helps to obscure the actual source of the reflection.

5) By carefully controlling the lighting and positioning of the object in the hidden room, the illusion can be made to appear and disappear, or even change appearance, creating a convincing ghostly or translucent effect.

This illusion was popularized by John Henry Pepper, a British scientist and inventor, who first demonstrated the effect in the 19th century.


Versions of Peppers Ghost

The following are some additional images that help show how Peppers Ghost works:

Peppers Ghost 1
If looking through the red rectangle, you see a ghost floating next to the table. The green outline represents the Plexiglas. The room to the left is hidden from the viewer and is a mirror image of the right side


Peppers Ghost 2
If the mirror-image room (left) is darkened, it does not reflect well in the glass. The empty room (top) is brightly lit, making it very visible to the viewer

Peppers Ghost
When the lights in the mirror-image room are raised (with the empty room being dimmed slightly to compensate), the ghost appears out of nowhere


Illusions like Peppers Ghost

Pepper’s Ghost is a reflective illusion. It creates the appearance of a ghostly or translucent figure by reflecting an object onto a transparent sheet and positioning it in such a way that the reflection appears to the audience as if it is floating in the air. The transparent sheet acts as a reflector, and the 45-degree angle at which it is positioned helps to obscure the actual source of the reflection and enhances the illusion.

Some examples other illusions that exploit angles and positioning include:

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.

Kanizsa Triangle Illusion
The Kanizsa Triangle

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

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


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


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 Peppers Ghost

This illusion was popularized by John Henry Pepper, a British scientist and inventor, who first demonstrated the effect in the 19th century.

John Henry Pepper was a British scientist and inventor who lived from 1821 to 1900.

He is best known for popularizing the Pepper’s Ghost illusion, a type of optical illusion that creates the appearance of ghostly or translucent figures using reflections and perspective.

Pepper first demonstrated the effect in a stage show in the 1860s and it quickly became popular as a theatrical effect.

The illusion has since been used in a variety of settings, including theme parks, museums, and haunted houses.

Pepper’s contributions to the field of optics and illusion have earned him a place in the history of entertainment technology.

References and Resources

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McCollough Effect

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McCollough effect

The McCollough effect is a phenomenon of visual perception where an individual perceives a grating (grid of black and white bars) as having color, after prolonged viewing of a colored grating.

The effect is an example of neural adaptation, where the brain adjusts to the stimuli it receives.

Look at each side of the following image for 30 seconds, then turn your gaze to the white grids below. The white horizontal stripes should appear greenish, and the white vertical stripes should look reddish.


McCollough effect
McCollough Effect


McCollough effect
McCollough Effect


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How does the McCollough Effect work?

The McCollough effect works by a process called neural adaptation, which refers to the change in the responsiveness of neurons in the visual cortex to a stimulus over time.

The process occurs when the individual looks at a colored grating pattern, which causes the neurons in the visual cortex to become adapted to the particular hue of the grating.

When the individual then views a grating with a different orientation, the brain continues to perceive the afterimage of the original grating with its hue, leading to a cross-orientation interaction where the grating appears to have a color.

The effect can persist for several minutes to hours, even after the individual stops viewing the grating.

Versions of the McCollough Effect

The following are other examples of the McCollough Effect



McCollough effect




McCollough effect



Illusions like McCollough Effect

The McCollough effect is a type of afterimage illusion.

An afterimage is an optical illusion that occurs when a person looks at a bright image for a short period and then looks away, causing a complementary image to persist for a short time.

The McCollough effect is a specific type of afterimage illusion that involves the perception of color in an image that is actually grayscale.

It results from a change in the responsiveness of neurons in the visual cortex to a stimulus over time, which is known as neural adaptation.

Some related illusions include the following:

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.



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.


Color constancy
Color Constancy


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).


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 McCollough Effect

The McCollough effect was discovered by American psychologist Celeste McCollough in 1965.

Celeste McCollough was an American psychologist and researcher who is best known for discovering the McCollough effect.

She conducted extensive research in the field of perception and color vision and made significant contributions to our understanding of how the visual system processes and represents visual information.

McCollough’s discovery of the McCollough effect helped to further our understanding of the underlying mechanisms of visual perception and how the brain processes and represents visual information.

References and Resources

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Irradiation Illusion

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Irradiation Illusion

The irradiation illusion is an optical illusion where the brightness or perceived size of an object can be altered by the presence of surrounding stimuli.

In this illusion, a small, dark object surrounded by a large, bright area will appear larger and brighter than it actually is.

Conversely, a large, bright object surrounded by a small, dark area will appear smaller and darker than it actually is.


Irradiation Illusion
Irradiation Illusion


Table of Contents


How does the Irradiation Illusion work?

he irradiation illusion works by altering the perceived brightness and size of an object based on the brightness and size of the surrounding stimuli. The brain uses contextual information from the surrounding area to adjust its perception of the brightness and size of objects in a scene.

For example, in the case of a small, dark object surrounded by a large, bright area, the brain assumes that the small, dark object must be closer to the observer and thus appears larger and brighter. This is because the bright surrounding area makes the small, dark object appear as if it is being lit from the front, which gives the illusion of increased size and brightness.

In contrast, in the case of a large, bright object surrounded by a small, dark area, the brain assumes that the large, bright object must be farther away from the observer and thus appears smaller and darker. This is because the small, dark surrounding area makes the large, bright object appear as if it is being lit from behind, which gives the illusion of decreased size and brightness.

The irradiation illusion is thought to be the result of the brain’s attempt to make sense of the visual information it receives and create a coherent perception of the world. The illusion is dependent on the relative brightness and size of the object and the surrounding area, and it can be used to demonstrate how the brain uses contextual information to make judgments about the properties of object


Versions of the Irradiation Illusion


The following are some alternate versions of the Irradiation Illusion:


Irradiation Illusion


Irradiation Illusion


Illusions like the Irradiation Illusion

The irradiation illusion is a type of contextual illusion. It is an optical illusion that occurs when the perceived brightness or size of an object is altered by the presence of surrounding stimuli.

In this illusion, the brain uses information from the surrounding area to adjust its perception of the brightness and size of objects in a scene.

The irradiation illusion is an example of how the brain uses contextual information to form a coherent perception of the world, and it highlights the importance of context in shaping our perception of objects and their properties.

The following are some illusions similar to the Irradiation Illusion.

The Helmholtz Illusion. The square of horizontal lines appears to be taller and narrower than the identical square of vertical lines.

Helmholtz Illusion
Helmholtz 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

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.


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



Discovery of the Irradiation Illusion

The discovery of the irradiation illusion is credited to the psychologist Max Wertheimer, a founder of the Gestalt psychology movement. Wertheimer’s work on the irradiation illusion was part of a broader effort to understand how the brain processes and integrates visual information from different parts of a scene to form a coherent perception of the world.

Wertheimer’s work on the irradiation illusion was groundbreaking in its time, and it helped to establish the principle of perceptual organization, which states that the brain tends to group stimuli into coherent patterns and wholes. Wertheimer’s insights into the role of context in shaping perception had a profound impact on the field of psychology and continue to be widely studied and applied today.

Although Wertheimer is credited with discovering the irradiation illusion, it is likely that the phenomenon was known and described by other scientists before him. Nevertheless, Wertheimer’s contribution to the study of the irradiation illusion and his broader work on perceptual organization have had a lasting impact on the field of psychology, and his legacy continues to be felt today.

Max Wertheimer (1880-1943) was a Czech psychologist and a founder of the Gestalt psychology movement. He is best known for his work on the perception of movement, which demonstrated that the brain processes the visual information it receives as a sequence of snapshots, and that the perception of movement is created by the brain filling in the gaps between these snapshots.

Wertheimer’s work was groundbreaking in its time and had a profound impact on the field of psychology. He showed that the brain does not simply respond to individual stimuli, but rather that it integrates and interprets information from the surrounding environment to create a coherent perception of the world.

Wertheimer’s insights into the role of context in shaping perception and his broader work on perceptual organization helped to establish the principle of perceptual organization, which states that the brain tends to group stimuli into coherent patterns and wholes. This principle has been widely studied and applied in the fields of psychology, cognitive science, and neuroscience, and it continues to play a central role in our understanding of how the brain processes visual information.

Wertheimer was a prolific and influential psychologist, and his work continues to be widely studied and referenced by researchers and students in the field of psychology and related disciplines.

References and Resources

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Filling In

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Filling In

Filling-in, also known as Troxler’s fading, 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.

Filling In
From Wikimedia Commons
After staring at the red dot for several seconds, the blue ring will fade

Table of Contents

How does Filling In work?

Filling-in refers to the visual process by which the brain unconsciously fills in missing or degraded visual information in a scene, based on prior knowledge or expectations. This can lead to the perception of a complete and coherent image even when some parts of the visual input are missing or ambiguous. The brain uses this ability to fill-in gaps in sensory information to create a continuous and stable perception of the visual world.

Troxler’s fading and filling-in are related phenomena in vision. Troxler’s fading is a type of visual adaptation where an unchanging stimulus eventually disappears from consciousness, while filling-in refers to the brain’s ability to “fill in” the background of a visual scene based on prior knowledge or expectations. These two processes are related in that they both involve the brain unconsciously filtering out or adjusting sensory information over time.

Filling-in 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 Filling-in. 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.

Filling-in effect is not limited to visual perception, but can be observed in other senses as well, such as touch and hearing.

Versions of the Filling In

The following are some other examples of Filling in and 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


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



Illusions like Filling In

The following are some illusions that are related to Filling In and 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 Filling In Fading

The phenomenon of filling-in has been studied and documented by many vision researchers, but no single person is credited with discovering it. The concept has been developed and refined over many years by the collective efforts of many scientists in the field of vision research.

Troxler’s Fading 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

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Mirage

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Mirage

A mirage is a type of optical illusion caused by the bending of light in a layer of hot air, which can make distant objects appear to shimmer or float above the ground.

Mirage
Mirage


Table of Contents

How do Mirages work?

A mirage works due to the refraction, or bending, of light as it passes through air of different temperatures.

When light travels from a dense material, like air, to a less dense material, like hot air, it slows down and bends.

This bending of light can cause objects to appear distorted or displaced, creating the illusion of a mirage. The hot air near the ground causes light to be bent and makes objects appear to be in a different location or shape.

Version of the Mirages

The following are a few of the images of mirages:



Mirage



Mirage



Illusions like Mirages

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 Mirages

The phenomenon of mirages has been observed and documented by many cultures throughout history, and as such, no single person is credited with discovering them.

References and Resources

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Benham’s Top

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The Benham’s top illusion is the visual effect created when the top is spun, in which the pattern appears to change colors.

The illusion is caused by the phenomenon of persistence of vision, in which the brain continues to perceive an image for a short period of time after it has disappeared.

As the top spins, the brain perceives the pattern as if it were changing colors due to the persistence of the previous image. This is an optical illusion and the color does not actually change.

Benham's Top
Benham’s Top


Table of Contents


How does Benham’s Top work?

The Benham’s top illusion works by exploiting the phenomenon of persistence of vision. Persistence of vision is a characteristic of the human visual system where an image that is presented for a short period of time is perceived to persist for a fraction of a second longer.

When the Benham’s top is spun, the pattern on the top moves quickly past the viewer’s eyes, and because of persistence of vision, the brain perceives the pattern as if it were changing colors. The pattern on the top is composed of alternating bright and dark colors, and as the top spins, the brain perceives the dark colors as one color and the bright colors as another color, creating the illusion that the top is changing colors.

Additionally, the speed of rotation and the design of the pattern are important factors that affect the illusion. A faster spinning top will make the illusion more pronounced, and a pattern with more distinct colors will be more effective at creating the illusion.

Benham’s top and Fechner color are two different phenomena, but they are related and based on the same principle of persistence of vision.

Benham’s top is a mechanical device that uses a spinning disc with a pattern of alternating bright and dark colors to create the illusion of the disc changing color as it spins. This illusion is created by the brain’s persistence of vision, which makes it perceive the dark and bright colors as different colors.

Fechner color, named after the German psychologist Gustav Fechner, is a similar visual illusion that occurs when a rotating ring with a pattern of alternating colors is viewed. Like Benham’s top, the illusion is created by the brain’s persistence of vision, which makes the viewer perceive the ring as if the colors were blending together.

Both Benham’s top and Fechner color are examples of the persistence of vision phenomenon and how it can create optical illusions.

Versions of the Benham’s Top

The first is the image when still, the second is when it’s spinning:



Benham's Top





Illusions like Benham’s Top

Some related illusions include the following:

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

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 Benham’s Top

Benham’s top was discovered by S.G. Benham, a British scientist and inventor in the late 19th century.

He created the top as an optical toy that demonstrated the phenomenon of persistence of vision, and its ability to create the illusion of color change.

He published his work on the top in 1897 in the scientific journal “Nature“. His invention was popularized as a toy and used in demonstrations of optical phenomena in science education and entertainment shows.

References and Resources

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