The Müller-Lyer illusion is a visual perception illusion that consists of two lines of equal length, with arrows at each end pointing either inward or outward. The line with the inward-pointing arrows appears shorter than the line with the outward-pointing arrows, even though they are actually the same length. This illusion is often used in research on visual perception and the neural basis of perception. The classic Müller-Lyer illusion is depicted below.
Visual artist G. Sarcone has created a series of Müller-Lyer adaptations that create the illusion of motion. The following is a simple version.
Table of Contents
- How does the Standard Müller-Lyer Illusion work?
- Dynamic Sarcone Versions of the Müller-Lyer Illusion
- Illusions like the Müller-Lyer Illusion
- Discovery of the Müller-Lyer Illusion
- References and Resources
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How does the Standard Müller-Lyer Illusion work?
The Müller-Lyer illusion works by exploiting the brain’s tendency to interpret the visual information it receives in the context of other visual information. In the case of the Müller-Lyer illusion, the brain interprets the lines with inward-pointing arrows as being part of a concave shape, and the lines with outward-pointing arrows as being part of a convex shape. This interpretation leads the brain to perceive the lines with inward-pointing arrows as being shorter than they actually are, and the lines with outward-pointing arrows as being longer than they actually are.
This illusion is thought to be caused by the visual system’s use of depth cues, such as the size and angle of the arrowheads, to infer the three-dimensional structure of the lines. The visual system uses these cues to perceive the lines as being part of a 3D figure and not just a 2D representation. The perception of depth and distance are affected by the context of the arrowheads, which fool the visual system into perceiving the lines as if they were in different distances and therefore different sizes.
Another explanation of the illusion is based on the concept of “Gestalt grouping” where the brain organizes different elements in a scene into groups based on certain rules such as proximity, similarity, and continuity. The arrowheads in the Müller-Lyer illusion creates a sense of continuation and proximity between the lines and the arrowheads which leads to the perception of the lines as being different in length.
Dynamic Sarcone Versions of the Müller-Lyer Illusion
Illusions like the Müller-Lyer Illusion
There are many other visual perception illusions that work in similar ways to the Müller-Lyer illusion. Some examples include:
The Poggendorff illusion: This illusion is similar to the Müller-Lyer illusion, but instead of arrowheads, it uses a diagonal line that intersects two parallel lines. The brain perceives the diagonal line as being tilted, causing the parallel lines to appear as if they are not parallel.
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.
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.
The Kanizsa triangle: This illusion is created by placing Pac-Man-like shapes around an invisible triangle. The brain perceives the triangle as if it were a real, visible triangle.
The Zöllner illusion: This illusion involves parallel lines with diagonal lines intersecting them. The brain perceives the lines as if they were not parallel and that the diagonal lines are converging.
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.
Ponzo illusion: This illusion involves the perception of an object appearing larger or smaller depending on the size of the surrounding context.
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.
All these illusions are based on the brain’s perception of visual context, depth cues, and grouping rules. These illusions help to understand how the brain interprets visual information and how it can be deceived.
Discovery of the Müller-Lyer Illusion
The Müller-Lyer illusion is a visual perception illusion that was first described by Franz Carl Müller-Lyer in 1889.
Franz Carl Müller-Lyer (1857-1916) was a German sociologist, psychologist, and philosopher. He is best known for his work on visual perception and the Müller-Lyer illusion, which is named after him. He studied at the University of Heidelberg and later at the University of Leipzig, where he received his Ph.D. in 1879.
In 1882, he published a book “Visual illusions: their causes, characteristics, and applications,” in which he described and illustrated the Müller-Lyer illusion, which is considered one of the most famous illusions in the field of psychology. He also wrote several books on the topic of social psychology, including “The People of Primitive Societies” and “The Social Order.”
Müller-Lyer was also a social reformer and advocated for better housing and living conditions for the working class. He was also interested in the relationship between society and the individual and his work aimed to bridge the gap between the social sciences, such as sociology and psychology.
Müller-Lyer died in 1916 in Munich, Germany. His work on the Müller-Lyer illusion and his contributions to the field of social psychology are still widely studied today.
References and Resources
Check out our complete list of illusions.
Sarcone, Gianni A. “Dynamic Müller-Lyer Illusion.” From Sarcone’s Studio — A Sarcone & Waeber Web Resource. http://giannisarcone.com/Muller_lyer_illusion.html