Tuesday, October 30, 2018

Clever Hans

One nurse used to make some wishes on different fingers and ask me to pick a finger. She believed that the wish corresponding to the finger I chose would come true. She never told me what her wishes were and I never asked her about them. I just played along with what she asked me to do. At first, I used to choose a finger randomly but over time, I learnt how to choose the wish she desired the most. She came to believe that I had extra-ordinary clairvoyance and she frequently made me go through this 'choose a finger' routine.

I would look vaguely at her fingers so that she couldn't quite make out which finger I was looking at. So she would bend each finger and ask me which finger I had chosen. I soon noticed that the first finger she bent was often the wish she most desired. Occasionally this guess would be wrong. I could make out from her expression that she was disappointed with my choice. I would quickly indicate that she had misinterpreted my communication and that I had actually meant  another finger.  Overall, my guess was right about 90% of the time. Put my subterfuge down to horse sense.

Over a century ago, a horse from Germany named Clever Hans was known around the world for his inexplicable abilities. Not only could Hans count - something no other animals were said to do - but he could also tell time, identify playing cards, read and spell (in German, of course). In response to a question he would tap with his hooves either to indicate a number or the right option among many given. If Hans was asked what five and two added up to, he would tap seven times; if he was asked what day came after Monday, he would be told to tap once for Tuesday, twice for Wednesday, and so on.

Even rigorous questions of critical skeptics were answered correctly. More than a dozen scientists observed Hans and were convinced there was no signaling or trickery. What was the secret - if indeed there was one? Was it all a hoax or trick? Or was this a truly unique horse? The obvious guess was that this was an elaborate hoax, set up through some means of training between horse and master. It soon became apparent, however, that Hans answered not only his trainer, but co-operated even in the absence of his master with any person he had never seen before.

In 1904, the German board of education set up a commission to determine if the claims made about Hans were genuine. After a thorough examination, they concluded that there was no hoax involved. Finally in 1907, Professor Oscar Pfungst, a biologist and psychologist explained the phenomenon after close study. He found that the horse was unable to answer any question if the questioning person did not know the answer. Furthermore, the horse was unable to answer any question when it could not see the face of his examiner.

It turned out that the horse was an excellent and intelligent observer who could read the almost microscopic signals in the face of his master, thus indicating that it had tapped or was about to tap the correct number or letter and would receive a reward. For example, when Hans was asked to add two and three, the owner or another questioner would lean forward slightly after Hans had tapped the fifth time but before he could tap a sixth. Each time the horse would reach the correct number of taps to provide human-like knowledge about the day of the week, what a word meant or a mathematical answer, his trainer would make subtle movements (sometimes merely a change in facial expression or a shift of stance) that would cue Hans to stop. In the absence of such a signal, he was unable to perform.

The horse was indeed clever, not because he understood human language but because he could perceive very subtle muscle movements. More important, Pfungst discovered that people can unconsciously communicate information to others by subtle movements and that some animals can perceive these unconscious movements. Even Pfungst himself found that he was unable to control these clues as the horse continued to answer correctly when his face was visible to it. Therefore, it is now recommended that during all studies of animal behavior, any face-to-face contact between the examiner and the experimental animal should be strictly avoided.

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