Clever Hans was a horse which lived in Germany in the late 1800s, that was able to ‘solve’ mathematical problems, indicating the answer by tapping his hoof. He seemed to be able to grasp mathematical concepts and respond to the voice of humans. He was paraded around Germany and people were amazed by his apparent talent, but the show turned out to be a fraud. It turned out that Hans was able to perceive very subtle human movements, and when prompted by his owner he would start or to stop tapping with his hoof.