Near the beginning of the 20th century, a retired schoolteacher and devoted horse man, Mr. von Osten, believing in the intellectual potential of horses, spent 4 years tutoring Hans, a horse. At the end of the 4th year Clever Hans could answer just about any question put to him in spoken or written German. He even had the uncanny ability to answer questions in languages he had never been taught, whether von Osten was present or not. Several prominent scientists studied Hans and concluded what von Osten believed was true. Psychologist Oskar Pfungst is the man responsible for uncovering the truth. Hans communicated with hoof taps and head movements. When posed a question requiring a yes answer, those in the audience would make subtle nodding gestures and Hans would do the same, then be rewarded. When posed a question requiring taps, Hans would start tapping when the audience looked at his feet and stop tapping when they looked up, and would again be rewarded. Pfungst reported even after isolating the signal he found it difficult to keep himself from giving Hans the answer. Even though Hans didn't know the capital of North Korea, he was still one clever animal.