At the turn of the 20th century, a famous horse named Clever Hans toured Germany. The horse stunned crowds as his trainer demonstrated the animal's alleged ability to understand German, tell time and even solve math problems.
But when an independent team investigated Clever Hans, they concluded his act was a fraud. It turned out that the horse actually just responded to subconscious body-language cues from his trainer and couldn't really comprehend human language or perform arithmetic feats.
