Clever Hans

Skeptics and Tests

Hans had his skeptics, who believed that von Osten was tricking the public. To prove that he [Page 151]was not, von Osten allowed skeptics to question Hans in his absence. All indications were that von Osten was convinced that Hans was capable of inner speech and independent thought. He also believed that Hans was capable of experiencing and showing emotion. Von Osten offered these emotional states as the explanation when Hans failed to produce the correct answer to a question. The evidence was strong enough that most doubters came to believe that Hans was an exceptional horse.

However, there was a persistent skeptic who was still not convinced—an experimental psychologist named Oskar Pfungst. Pfungst was not satisfied with the evidence that Hans was a wonder horse. He set up several experiments to discover how the horse was able to answer the many questions presented, and whether he was really capable of independent thought. Von Osten was open to allowing the experiments, because he was convinced that Hans was answering the questions.

During the initial experiments, different persons were used to ask Hans the questions. Even without von Osten present, it appeared as though the horse was able to correctly answer the questions. After several experiments were conducted, Pfungst noticed a theme. When Hans's audience did not know the answer to the question, Hans's accuracy severely decreased. Pfungst then had one person whisper a number in Hans's ear, and then a different person would whisper another number in his other ear. Then, Hans was asked to add the two numbers together. Neither questioner knew what number the other had whispered, thus neither knew the answer. Hans either could not produce an answer, or would just continue endlessly tapping.

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