The Müller-Lyer illusion is an optical illusion used in psychology to study human perception. Here's an explanation of how it works.
Müller-Lyer illusion - Wikipedia
PDF) The Müller-Lyer illusion explained by the statistics of image
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Muller lyer illusion hi-res stock photography and images - Alamy
PDF) Perception of the Müller-Lyer illusion in guppies
The perception of interpersonal distance is distorted by the
How does the Muller-Lyer illusion work? — Brain Stuff
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Muller Lyer Illusion Test report - SUBJECT : EXPERIMENTAL