The sad story of Kluge Hans, the horse that calculated – 12/19/2023 – Marcelo Viana

Some 120 years ago, one of the biggest celebrities in world science was Kluge Hans (John Smart, in German), the horse who, according to his owner, knew how to add, subtract, multiply, divide, operate with fractions, tell the time and calculate days of the week.

The owner, mathematics professor and amateur horse trainer Wilhelm von Osten, exhibited Hans publicly, without charging admission, much to the astonishment of the audience. For example, when Von Osten asked “if the eighth day of the month is a Tuesday, what date does the following Friday fall on?” Hans responded by stamping his hoof on the ground 11 times.

Skeptics said it was fraud, that Von Osten passed the answers to the animal through signals. But Hans got it right even when the owner was away and the questions were asked by someone else. The legend of the horse he calculated kept growing.

Given public interest, Germany’s education authority created a commission of 13 experts to investigate the phenomenon. In addition to the psychologist Carl Stumpf, who presided over it, it included a veterinarian, a circus manager, a cavalry officer, several teachers and the director of the Berlin zoo. In September 1904 the report came out, which cleared Von Osten of any trickery.

So, biologist and psychologist Oskar Pfungst decided to test the horse’s abilities under different conditions: using other people to question Hans; isolating the questioner and the horse from the audience; varying whether Hans could see the questioner or not; and even whether the questioner knew the answers or not.

In this way, he confirmed that it did not matter who asked the questions, which proved that there was no bad faith on Von Osten’s part. On the other hand, Pfungst found that Hans only answered correctly when he could see the questioner and he knew the answers! In some subconscious way, the questioner passed the answers to the horse… And this happened even when it was Pfungst himself who was questioning!

The discovery brought poor Hans into disrepute, which was very unfair: even though he was unable to calculate, Hans was a remarkable animal, with an extraordinary ability to read human facial expressions and body language, better than we can ourselves. We are capable.

Von Osten was not convinced by Pfungst’s conclusions and continued exhibiting his phenomenon until his death in 1909. From then on, Hans passed through several owners and ended up being enlisted to serve in the First World War. His record ends in 1916, when, it is believed, he “was killed in action or eaten by starving soldiers.”

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