The Mosaic Illusion on the floor of the Siena Doumo L Sugano |
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Faculty of Human Science, Takachiho University, OR, Japan
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| The authors of this paper discovered a new geometrical optical illusion in a chain of mosaics, laid between the 14th and 16th centuries, on the floor of the Duomo in Siena, Italy. Our study shows that these previously unidentified perceptual phenomena exist and result from an unstable background which contributes to this type of geometrical optical illusion. The Gothic style mosaics consist of inlaid pieces which surround the icon often identified as the Imperial Eagle, located at the third composition from the entrance. These mosaics are composed of successive 'Mach book' figures (see E. Rubin (1921)), defined as two-dimensional shapes which look three-dimensional without a background (see Mach (1883)). The same perceptual phenomenon is also found in the mosaic inlay of what is referred to as the Wheel of Fortune at the fifth composition from the entrance. These mosaics are shaped as parallelograms and consist of white and brown mosaics. Because of the unstable background, these patterns can appear as either a stairway ascending to the right with white steps or as a stairway ascending to the left with alternating brown steps. No previous studies (Mach (1883) among others) have referred to these geometric optical illusions in the Duomo. |
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