the answer, Hans did, too. Now can you guess?
People gave off very subtle body-language signals the moment Hanss hoof gave the right number of taps. When Hans started tapping the answer to a question, the audience would show sutle signs of tension. Then, when Hans reached the right number, they responded by an expulsion of breath or slight relaxation of muscles. Von Osten had trained Hans to stop tapping at that point and therefore appear to give the right answer.
Hans was using the technique I call Hanss Horse Sense. He watched his audiences reactions very carefully and planned his responses accordingly