The sixty-something math instructor stood proudly with a black, slouch hat covering his thinning white hair.
To his left, stood the pupilan impressive Russian trotting horse.
Not only could Hans count, he could perform arithmetic far beyond the fundamentals.
How much is 2/5 plus 1/2?, von Osten would ask.
Hans would answer with nine taps followed by another ten to indicate that the answer was 9/10.
What is the square root of sixteen?
Hans would make four taps.
What are the factors of 28?
Hans would tap consecutively 2, 4, 7, 14, 28.
Hans could even pick up cleverly worded questions: I have a number in mind.
I subtract 9, and have 3 as a remainder.
What is the number I had in mind?.
In the number 365287149, I place a decimal point after the 8.
How many are there now in the hundreds place?
von Osten would press on.
Hans would reply promptly with five taps.
Clever Hans intelligence wasnt just limited to arithmetic.
Clever Hans shows a number on the footboard.
Hans also gave evidence of excellent memory, and apparently carried the entire yearly calendar in his head.
The versatility of Hans in other directions was baffling.
By some estimates, Hans mental development was similar to a child of 13 or 14 years.
Naturally, Hans aroused curiosity among many psychologists, zoologists and experts in various other fields.
This was a time when studies on animal cognition and their mental processes were few and far between.
The general consensus was that animals were incapable of exhibiting anthropomorphic intelligence.
This is known as Morgan’s Canon, and it is a fundamental precept of comparative animal psychology.
Clever Hans and Wilhelm von Osten.
Pfungst designed a careful set of experiments and began testing Hans.
To confirm this, Pfungst kept the answers hidden from the questioner.
At once, Hans accuracy dropped.
Clever Hans demonstrating his arithmetic skills.
Thereupon I did likewise.
Hans was asked to add the two.
Every such test was immediately repeated with the result known to the experimenters.
Oskar Pfungst wrote:
The usual distance was one-quarter to one-half meter.
This holds for all tests hitherto described.
Every test Pfungst conducted, Hans failed miserably.
Clever Hans before an audience in 1904.
As soon as the final, correct tap was made, the tension was suddenly released.
This provided a cue for Hans that he should stop tapping.
Pfungst asked his subjects to concentrate upon a particular number.
Pfungst would then tap out the answers solely by observing the body language of his human subjects.
But his intelligence, by no means, approached that of a human.
Clever Hans in 1910.
This is known today as the Clever Hans Effect.
Despite Pfungsts expose, Clever Hans never stopped being a sensation.
His owner, von Osten continued making tours throughout Germany drawing crowds wherever he put up a show.
von Osten never charged a dime for these exhibitions.
He genuinely believed in Clever Hans unmatched intelligence.
His fate is unknown, but some believe that Hans was killed in action in 1916.
References:# Oskar Pfungst, Clever Hans (The horse of Mr.
