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
Table of Contents
- How does the Afterimage Illusion work?
- Versions of the Afterimage Illusion
- Illusions like the Afterimage Illusion
- Discovery of the Afterimage Illusion
- References and Resources
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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:
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.
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 Neon Color Spreading illusion refers to the visual phenomenon where an area of color appears to spread or “bleed” beyond its intended boundaries.
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.
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 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.
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.
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.
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.
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.