He collaborated with Sigmund Freud from 1907 until their disagreement in 1914 over the importance of sexuality in causing psychological problems. Jung studied myth, religion, and dream symbolism, saw the unconscious as a source of spiritual insight, and distinguished between introversion and extroversion. Jung devised the word-association test in the early 1900s as a technique for penetrating a subject's unconscious mind. He also developed his theory concerning emotional, partly repressed ideas which he termed "complexes". In place of Freud's emphasis on infantile sexuality, Jung introduced the idea of a "collective unconscious" which is made up of many archetypes or "congenital conditions of intuition". Jung was born near Basel and studied there and at Zuerich. He worked at the Burghoelzli Psychiatric Clinic in Zuerich 1902-09. In 1907 he met Freud and became his chief disciple, appointed president of the International Psychoanalytic Association on its foundation 1910. But in 1914 he resigned from the association and set up his own practice in Zuerich. In 1933 he became professor at the Zuerich Federal Institute of Technology. The book that provoked his split with Freud was Wandlungen und Symbole de Libido/The Psychology of the Unconscious 1912. Jung introduced the concept of introverts and extroverts in Psychologische Typen/Psychological Types 1921. This work also contained his theory that the mind has four basic functions: thinking, feeling, sensations, and intuition. Any particular person's personality can be ascribed to the predominance of one of these functions.
