The World’s Oldest Optical Illusion

 In the October 1892 issue of the German humor magazine Fliegende Blätter, an image depicting an optical illusion appeared. Was the image a sketch of a rabbit's head, or was it a duck's head? Both images seemed to go back and forth from being a duck to becoming a rabbit. Half a century later, the image reappeared in Ludwig Wittgenstein's 1953 book Philosophical Investigations, where the famous philosopher used the example to illustrate how certain data can be interpreted in more than one way. Over the next seventy years, the duck-rabbit illusion would appear countless times in books, magazines, and websites.

Throughout human history, artists have used various techniques to deceive viewers, such as creating the impression of depth in flat frescoes by using clever combinations of brushstrokes and shadows, also known as the trompe-l'oeil effect. Is known. Some evidence suggests that even Paleolithic artists, who decorated cave walls with paintings of horses and bison, cleverly manipulated the rock's natural reliefs to add a sense of volume and depth to their artwork. Used. Particularly noteworthy are the prehistoric artefacts found in the cave of Font-de-Gaume in France.

Prehistorian Duncan Caldwell, who has surveyed the Palaeolithic art of several caves in France, has found that throughout the cave of Font-de-Gaume there appear carvings and images of woolly mammoths and bison that often share some lines or other features. , creating overlapping images. It can be read first as one animal, then as another, much like the duck-rabbit confusion. Caldwell says he found mammoth-bison pairs appearing so frequently throughout the cave that it cannot be mere coincidence. Indeed, Caldwell also found a small statue that was carved to depict a bison on one side and a mammoth on the other. Caldwell believes that the physical similarities between the two animal figures make them ideal candidates for prehistoric artists to superimpose their respective images in a single illustration.

Another dramatic example of the mammoth-bison confusion appears on a carving of a spear thrower from the site of Canacoué. In this piece, both the mammoth and the bison are shown sharing the same outline. Furthermore, there are two small details, as Caldwell sees it, that allow the entire image to be read as either of the two species, and seeing one makes the other "disappear".

This carving of a spear thrower has an image that can be viewed in two different ways. The eyes above and below the crescent, which serve as both a mammoth tusk (for the upper eye) and a bison's horn (for the lower eye), are highlighted in red in the photo on the right. Images courtesy of Duncan Caldwell

Hawley writes that it is difficult to think of any other reason than that the delicately carved figures were deliberately made, and not merely accidental markings. Details of the animal's body, including its teeth/horns, long hair and legs, are realistically rendered, reflecting the artistic ability of its creator.

However, it is possible that the image is of just one mammoth and not a mammoth-bison combo, especially since some pieces of the spear thrower are missing. In the book Mammoths: Giants of the Ice Age, authors Adrian Lister and Paul Bunn propose that the mammoth's torso may have rotated backwards in the lower-left part of the carving, causing the lower "eye" to be the folded end of the mammoth's torso. Will become. ,

Another example of an early optical illusion can be found in the Airavatesvara Temple in the South Indian state of Tamil Nadu. This fallacy is beyond doubt.

This bas-relief clearly shows two animals sharing the same head. Depending on which creature you focus on, you should see an elephant or a bull. The temple was built by the Chola emperor Rajaraja II in the 12th century, making it the oldest verified optical illusion in the world.