Fraser spiral illusion
The Fraser spiral illusion is an optical illusion that was first described by the British psychologist Sir James Fraser (1863–1936) in 1908.[1]
The illusion is also known as the false spiral, or by its original name, the twisted cord illusion. The overlapping black arc segments appear to form a spiral; however, the arcs are a series of concentric circles.
The visual distortion is produced by combining a regular line pattern (the circles) with misaligned parts (the differently colored strands).
The illusion is augmented by the spiral components in the checkered background. It is a unique illusion, where the observer can verify the concentric strands manually.[3] When the strands are highlighted in a different colour, it becomes obvious to the observer that no spiral is present.[4]
See also
- Op-art
- Mathematics and art
References
- ^ Fraser J (1908) A New Visual Illusion of Direction. British Journal of Psychology 2:307–320
- ISBN 978-0-521-72876-8.
- ISBN 9781134575985.
- ^ See Bach, Michael. "Fraser Illusion". Visual Phenomena & Optical Illusions. Archived from the original on 2011-11-02. Retrieved 2005-06-11.
External links
- Fraser's Spiral from MathWorld
- Bach, Michael. "Fraser Illusion". Visual Phenomena & Optical Illusions. Archived from the original on 2011-11-02. Retrieved 2005-06-11. An interactive Fraser Spiral