Some species of animals are especially clever at detecting human body language, both voluntary and involuntary. There is the instance of a horse called Hans, who seemed to be able to add, subtract, multiply, divide, work with fractions and do other intellectual tasks. If you asked him a question, Hans would reply by tapping his foot till the correct
Han’s abilities amazed the world, but a formal investigation showed that the horse was not really calculating the answers, but was responding to the questioner’s body language. As the horse’s taps approached the right answer, the questioner’s posture and facial expression