Yerkes, Robert Mearns (yûr`kēz), 1876–1956, American psychologist, b. Bucks co., Pa., grad. Harvard (B.A. 1898; Ph.D.1902). He taught (1902–17) at Harvard, served (1919–24) on the National Research Council, and held a post as professor of psychobiology at Yale (1924–44). He also founded (1929) and directed the Yale Laboratories of Primate Biology (renamed the Yerkes Laboratories of Primate Biology in 1942) at Orange Park, Fla. He is known for his work in comparative psychology, the experimental study of animal behavior, and his research in psychobiology. His works include The Mental Life of Monkeys and Apes (1916, repr. 1979), The Mind of a Gorilla (2 parts, 1926–27), The Great Apes (with Ada Yerkes, 1929), and Chimpanzees (1943).