Freud and Jung are the two most well-known psychologists of the twentieth century, but they're certainly not the only ones. Here, in brief, are some of the other major players in the world of psychology.

Alfred Adler

Alfred Adler (1870–1937) was another of Freud's students who learned much from the maestro, but, like many others, differed with him on the sex issue. Adler believed that feelings of inferiority rather than sexuality were the main motivating unconscious force in people. In fact, he was the guy who coined the phrase “inferiority complex.”People basically felt inferior, and much of psychological energy was spent finding ways to compensate for these feelings and strive for perfection. He researched and wrote about family dynamics and the role that birth order plays in personality development. He also got people off the Freudian couch and preferred the patient and doctor to sit face to face. This created a sense of equality and made the therapist less of an imposing authority figure.

William James

The Father of American Psychology is William James (1842–1909), brother of the novelist Henry James. His two-volume Principles of Psychology was the bible for a generation of American psychologists. His approach was Functionalist, proposing that the important purpose of psychological study was to examine the functions of the conscious. This involved studying selected subjects over a lengthy period of time, which consisted of observation and tests and was called longitudinal research. James was influenced by Darwin's theory of evolution. It was James and his research that took psychology out of the philosophical realm and placed it in the laboratory. He wrote many books, one of which, The Varieties of Religious Experience, influenced the founders of Alcoholics Anonymous.

Jean Piaget

Jean Piaget's (1896–1980) main claim to fame is the work he did with children. After years of working in schools and interviewing thousands of children, the Swiss psychologist identified four stages of childhood development.

• The sensorimotor stage, from birth to age two, involves the mastering of motor controls and learning to deal with the physical world.

• In the preoperational stage, from ages two to seven, the child focuses on verbal skills and communication.

• In the concrete operational stage, children begin to deal with numbers and other complex concepts.

• Logic and reason evolve in the formal operational stage.