Adler, Alfred (1870-1937), an Austrian psychiatrist, developed important theories concerning the motivation of human behavior. According to Adler, the major force of all human activity is a striving from a feeling of inferiority toward perfection. Adler at first referred to this force as an aggressive drive. He later called the force a striving for superiority. Adler termed his school of thought individual psychology. Today, it is often referred to as Adlerian psychology.