The Expression of the Emotions in Man and Animals
Darwin's basic points were: a single origin for the entire human species, and universal human expressions. Also, there are obvious links between the way human emotions are shown and the way other mammals show their emotions. Our emotional displays are adapted from a more basic set of emotional displays common to many mammals. The emotional displays are inherited, automatic and are difficult to control with our conscious mind. They are operated by the more ancient unconscious mind. Modern research has shown that it is extremely difficult to avoid giving signs of our emotions.