The Jastrow illusion is an optical illusion where two identical figures are placed next to each other. Although they are both exactly the same size, one appears to be larger.
The study of perceptual illusions like the Jastrow illusion helps scientists to investigate the various mechanisms involved in the visual perception of objects, and thus increases our understanding of how our minds function in informing us about the environment. This type of illusion also is reminds us that human nature has endless creativity and appreciation for novelty.
The Jastrow illusion is named for the American psychologist Joseph Jastrow, who discovered the illusion in 1889. Jastrow is also well known for his "duck-rabbit" ambiguous figure in which the the object's identification switches back and forth from that of a duck to that of a rabbit.
The Jastrow illusion is a size illusion where two curved shapes of identical measurements are placed next to each other. When viewing the two shapes, one looks significantly larger than the other. When the positions of the two shapes are reversed, the impression of which is the larger is also reversed.
Scientists are not yet certain what causes one figure in the Jastrow illusion to appear larger than the other. Similar effects have been noted by a number of researchers using a variety of geometric shapes, including trapezia, parallelograms, and lozenges.
The fact that the shorter side of one figure is next to the longer side of the other somehow tricks the brain into perceiving one shape as longer and the other as shorter, although it is unclear exactly why this is so.
Artists utilize the illusory effects, such as in Jastrow's illusion, to introduce complex and interesting effects in their works.
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