Robert Mearns Yerkes, PhD, (May 26 1876 – February 3 1956 (aged 79)) was a psychologist, ethologist, and primatologist best known for his work in intelligence testing and in the field of comparative psychology. Yerkes was a pioneer in the study both of human and primate intelligence and of the social behavior of gorillas and chimpanzees. Along with John D. Dodson, Yerkes developed the Yerkes-Dodson law relating arousal to performance.
Education and early career
Growing up on a farm in rural Pennsylvania, Robert Yerkes wanted to leave the hard life of the rural farmer and become a physician. With the financial help of an uncle, Yerkes attended Ursinus College from 1892 to 1897. Upon graduating he received an offer from Harvard University to do graduate work in Biology. Faced with a choice of Harvard or medical training in Philadelphia, he chose to go to Harvard.
At Harvard, Yerkes became interested in animal behavior, so much so that he put off further medical training to study comparative psychology. He earned his PhD in the Psychology Department in 1902.
His early career was strongly influenced by the debts Yerkes incurred paying for school. Upon his graduation from Harvard, he took up a position with the school as an instructor and Assistant Professor in Comparative Psychology. He had to supplement his income during the summer for several years by teaching general psychology at Radcliffe College. Another part-time job he took on was being the director of psychological research at the Boston State Psychopathic Hospital in Boston, Massachusetts.
In 1907, Yerkes published his first book, The Dancing Mouse. Among his friends during this time was DNA pioneer John Watson, with whom he exchanged ideas and collaborated. He was also a member of the Wicht Club (1903 - 1911).
In 1917, Yerkes served as president of the American Psychological Association (APA). Under his urging, the APA began several programs devoted to the war effort in World War I. As chairman of the Committee on the Psychological Examination of Recruits, he developed the Army's Alpha and Beta Intelligence Tests, the first nonverbal group tests, which were given to over 1 million United States soldiers during the war. The test ultimately concluded that recent immigrants (especially those from Southern and Eastern Europe) scored considerably lower than older waves of immigration (from Northern Europe), and was used as one of the eugenic motivations for harsh immigration restriction. The results would later be criticized as very clearly only measuring acculturation, as the test scores correlated nearly exactly with the number of years spent living in the US.
National Research Council
Immediately after World War I, Yerkes worked as a paid officer for the United States National Research Council (NRC) and took the helm of the NRC Committee for Research in Problems of Sex. The Committee for Research in Problems of Sex helped Yerkes establish close relationships with officers from Rockefeller philanthropic foundations. These relationships later helped him to solicit substantial funds for his chimpanzee projects.
Yerkes had a long and storied fascination with the study of chimpanzees. He had spent time observing chimpanzees in Cuba at Madame Abreu's colony in the early 1920s, and had returned from the trip determined to raise and observe chimps on his own. He began by purchasing two chimpanzees, Chim and Panzee, from a zoo. He brought the two chimps home, where they lived in a bedroom and ate with a fork at a miniature table. Chim was a particular delight for Yerkes, and the summer that chimp and psychologist spent together is memorialized in Almost Human (1924). 
In 1924, Yerkes was hired as a professor of psychobiology, a field he pioneered, at Yale University. He founded the Yale University Laboratories of Primate Biology in New Haven, followed by his Anthropoid Breeding and Experiment Station in Orange Park, Florida with funds from the Rockefeller Foundation. After his death, the lab was moved to Emory University in Atlanta, Georgia and is now called the Yerkes National Primate Research Center. The primate language Yerkish was developed there.
- 1907, The Dancing Mouse, A Study in Animal Behavior
- 1911, Introduction to Psychology
- 1911, Methods of Studying Vision in Animals (with John B. Watson)
- 1914, Outline of a Study of the Self
- 1915, A Point Scale for Measuring Mental Ability (with co-authors)
- Emory.edu - 'Innovation and Science: The History of Yerkes', Yerkes National Primate Research Center
- Indiana.edu - 'Robert Mearns Yerkes (1876-1956) American Comparative Psychologist', Indiana University
- IPFW.edu - 'Intelligence Tests' (historical overview)
- Karoo.net - 'A Nation of Morons' (critique of the Army Alpha Intelligence Test), Stephen Jay Gould
- YorkU.ca - 'Autobiography of Robert Mearns Yerkes', Robert Yerkes, York University (1930)
- Works by Robert Yerkes at Project Gutenberg
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