The oldest and simplest method, then, of describing differences in personali

The oldest and simplest method, then, of describing differences in personality was to classify people according to types. Such a system is called a Typology.
    A famous example of this method was set forth in Greece about the year 400 B.C. A physician named Hippocrates theorized that there were four fluids, or humors, in the body: blood, yellow bile(胆汁), black bile, and phlegm(粘液). Corresponding to each humor, there existed a definite type of personality.
    A person in whom all four humors were in perfect balance had a harmonious personality. If a person had too much blood, he was cheerful and optimistic. Someone with too much yellow bile was irritable and easily angered. Too much black bile made a person depressed and pessimistic. An oversupply of phlegm caused a human being to be slow and unfeeling.
    Other features of people, such as their faces and figures, have also been used to classify personality. Today, however, personality theories and classifications may also include factors such as heredity, the environment, intelligence, and emotional needs.