William Stern was a German psychologist and philosopher, born on April 29, 1871, and known for his contributions to the field of intelligence testing. He introduced the concept of the intelligence quotient (IQ) in 1912, which became a standard measure for assessing cognitive abilities. Stern's work laid the foundation for future psychological assessments and research on intelligence. In addition to his work on intelligence, Stern was also interested in personality psychology and the development of psychological measurement. He emphasized the importance of understanding individual differences and the role of environment in shaping personality. His ideas have influenced various areas of psychology and education.