This ancient optical illusion is a 14,000-year-old puzzle
Your brain might detect familiar details like tusks and fur on the hunting tool, which was unearthed in 1973 at Southern France’s La Montagne Noire. (Duncan Caldwell/)This carved ornament was fixed on a hunting tool more than 14,000 years ago, but the illusion remains. Concentrate on the higher eye-shaped notch on the left side, and a tusk curves below it, revealing a mammoth. Stare at the one lower down, and that pointed tooth becomes a bison’s horn as the beast bows its head. You might recall a similar 19th-century illustration: It’s a duck until the bird’s bill morphs into a pair of rabbit’s ears.The classic rabbit-duck illusion. (from Fliegende Blätter, October 23, 1892/)The rabbit-duck is a type of illusion called an ambiguous figure, and while we can’t know the ancient carver’s intent, this prehistoric knickknack is one too. According to Kyle Mathewson, a cognitive neuroscientist at the University of Alberta,...