Fraser's Spiral

Fraser's spiral

An optical illusion named after British psychologist James Fraser, who first studied the illusion in 1908 (Fraser 1908). The illusion is also known as the false spiral, or by its original name, the twisted cord illusion. While the image appears to be a spiral formed by a rope containing twisted strands of two different colors, it actually consists of concentric circles of twisted cords.

The visual distortion is produced by combining a regular line pattern (the circles) with misaligned parts (the differently colored strands). Zöllner's illusion and the café wall illusion are based on a similar principle, like many other visual effects, in which a sequence of tilted elements causes the eye to perceive phantom twists and deviations.

See also

Café Wall Illusion, Spiral, Zöllner's Illusion

This entry contributed by Margherita Barile

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Fraser, J. "A New Visual Illusion of Direction." Brit. J. Psych. 2, 307-320, 1908.Morgan, M. J. and Moulden, B. "The Münsterberg Figure and Twisted Cords." Vision Research 26, 1793-1800, 1986.Pappas, T. "The False Spiral Optical Illusion." The Joy of Mathematics. San Carlos, CA: Wide World Publ./Tetra, p. 114, 1989.Popple, A. V. and Sagi, D. "A Fraser Illusion Without Local Cues?" Vision Research 40, 873-878, 2000. LITE. "Fraser's Spiral.", A. The Art of Optical Illusions. Carlton Books, p. 9, 2002.Varenne, H. "Passages from 'A New Visual Illusion of Direction'."

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Fraser's Spiral

Cite this as:

Barile, Margherita. "Fraser's Spiral." From MathWorld--A Wolfram Web Resource, created by Eric W. Weisstein.

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