Fearful facial expressions enhance our perception

Show someone a piece of rotting food and their reaction will be visibly similar the world over. Their eyes will close, their noses will wrinkle and their mouths will tighten, all part of a universal expression of disgust. Darwin himself was struck by the universal nature of human facial expressions - from the busiest of cities to the most isolated of villages, smiles and frowns are recognisable, done in the same way and carry the same meaning.