Sunday, July 1, 2007

Horse sense

'Clever Hans' was a horse who lived in Germany, early in the twentieth century. He could read, solve mathematical problems, and answer questions on world political affairs - or so it seemed.

Hans would answer all mathematical questions by tapping his leg. If you asked him '3 plus 4', he would tap seven times. Non-mathematical questions (such as 'is London the capital of Britain?') would be answered by shaking or nodding the head. Hans could even answer questions written on blackboards.

Finally Hans' secret was discovered. He was highly sensitive to the reactions of people around him, especially his master Osten. When a mathematical question was asked, people would look at Hans' foot. So he would start tapping. When he reached the right number of taps, people would react in some way, without being aware of it. They would nod slightly, or relax, or smile. Hans would then stop tapping. Hans was able to pick up similar cues for non-mathematical questions. No one knows how he learnt this trick.

The most amazing thing is that even after people became aware of the horse's method, they could still not stop sending out these little clues, no matter how hard they tried!