Clever Hans

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Hans was a horse owned by Wilhelm von Osten. Hans was said to have been taught to add, subtract, multiply, divide, work with fractions, tell time, keep track of the calendar, #classify #compare *differentiate #evaluate between musical tones, and read, spell, and understand German. Hans would answer questions by tapping his hoof. Von Osten #demonstrated *exhibited #showed #viewed Hans throughout Germany. | The great public interest in Clever Hans led the German board of education to appoint a commission to #criticize *investigate #research #weigh von Osten’s scientific claims. This commission #assumed *concluded #confirmed #reasoned in September 1904 that no tricks were involved in Hans’s performance. The commission passed the evaluation to Oskar Pfungst. | Pfungst found that the horse could get the correct answer even if von Osten himself did not ask the questions, #cancelling #leaving_out #prohibiting *ruling_out the possibility of fraud. However, the horse gave the right answer only when the questioner knew what the answer was and the horse could see the questioner. He #detected #identified *observed #recognized that when von Osten knew the answers to the questions, Hans got 89 percent of the answers correct, but when von Osten did not know the answers to the questions, Hans answered only six percent of the questions correctly. | Pfungst then examined the #attitude *behaviour #nature #performance of the questioner in detail, and showed that as the horse’s taps approached the right answer, the questioner’s posture and facial expression changed in ways that were #coherent *consistent #equal #matching with an increase in tension, which was released when the horse made the final, correct tap. This provided a cue that the horse could use to tell it to stop tapping. The social #articulation *communication #conversation #transmission systems of horses may depend on the *detection #disclosure #finding #uncovering of small postural changes, and this would explain why Hans so easily picked up on the cues given by von Osten, even if these cues were subconscious.