Robert Yerkes was an American psychologist born on May 26, 1876, and he is best known for his work in comparative psychology and intelligence testing. He played a significant role in the development of the Yerkes-Dodson Law, which describes the relationship between arousal and performance. Yerkes also contributed to the field of animal behavior, studying various species to understand their cognitive abilities. In addition to his research, Yerkes was a prominent figure in the establishment of the American Psychological Association and served as its president. He was involved in the creation of the first large-scale intelligence tests for the U.S. military during World War I, known as the Army Alpha and Beta tests. His work has had a lasting impact on psychology and education.