Sheep (Ovis aries)
Because sheep blindly run away when they are panicked, people believe that they are “unintelligent”. However, researchers from the University of Illinois have proved that sheep intelligence level is only a little below pig intelligence (but how to put pigs on such a list? :)) and equal to the rest of horned farm animals.
These inconspicuous animals can recognize specific human and sheep faces, and they remember them for many years; on the basis of face expressions they can also guess the current emotional state, and the best method to train them is the clicker training which is about associating a “click” sound with a positive response and reward for the response.