Also cows are very smart animals, also sheeps which are ables to recognize themselves in a mirror, pigs even know how to play simple video games with a joystick. Certainly many animals are considerably more intelligent than previously thought. Crows and parrots not only know how to repeat words, but also understand their meaning, they are, together with the great apes, the only ones who allow an intelligible conversation, although with the apes only through sign language, since they lack of a phonetic apparatus necessary to be able to articulate words.