Sander illusion
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The Sander illusion or Sander's parallelogram is an optical illusion described by the German psychologist Friedrich Sander (1889-1971) in 1926. However, it had been published earlier by Matthew Luckiesh in his 1922 book Visual Illusions: Their Causes, Characteristics, and Applications [1].
The diagonal line bisecting the larger, left-hand parallelogram appears to be considerably longer than the diagonal line bisecting the smaller, right-hand parallelogram, but is in fact the same length.
One possible reason for this illusion is that the diagonal lines around the blue lines give a perception of depth, and when the blue lines are included in that depth, they are perceived as different lengths.
[edit] References
- ^ Sander parallelogram n. (2006). A Dictionary of Psychology. Andrew M. Colman. Oxford University Press, 2006.
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