Robert Mearns Yerkes was an American psychobiologist who was a principal developer of comparative psychology in the United States.
Yerkes was born in Breadysville, Pennsylvania on May 26, 1876. He graduated from Ursinus College and later got a Ph.D. at Harvard University in 1902. He then served first as instructor and later as professor of psychology there until 1917. He then taught at the University of Minnesota from 1917 until 1919. He was placed in charge of psychological testing for the armed forces when the United States entered World War I. He was chairman of the research information service of the National Research Council until 1924. He then spent the next two decades as a professor of psychology at Yale University.
His early studies of the behavior of invertebrates evolved into work with the lower mammals. In 1907 he wrote his first book, The Dancing Mouse. Yerkes helped establish the use of mice and rats as standard laboratory subjects in psychological testing.
In 1915 he became interested in the psychological testing of humans and made great contributions to the development of multiple-choice testing and a widely used point scale for measuring human mental ability.
In 1929 he organized the Yerkes Laboratories of Primate Biology, Inc., at Orange Park, Florida.
He was an authority on experimental primate psychology. In 1916 he wrote The Mental Life of Monkeys and Apes; The Mind of a Gorilla in 1927, and Chimpanzees: A Laboratory Colony in 1943.
In 1944 he retired from teaching at Yale.
He died on February 3, 1956 in New Haven, Connecticut.