Théodore Simon was a French psychologist born on April 9, 1873, and is best known for his work in the field of intelligence testing. He collaborated with Alfred Binet to develop the first practical intelligence test, known as the Binet-Simon scale, which aimed to identify children needing special educational support. This scale laid the groundwork for modern intelligence testing. Simon continued to refine and promote intelligence testing throughout his career. He contributed to the understanding of cognitive development and the assessment of mental abilities. His work has had a lasting impact on psychology, education, and the evaluation of learning disabilities.