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Robert Yerkes Biography

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Robert Yerkes

Robert Yerkes

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  • robert yerkes
  • intelligence testing
  • comparative psychology

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Robert Yerkes was born May 26, 1876.


He died on February 3, 1956.

Early Life:

Robert Yerkes grew up on a farm in Breadysville, Pennsylvania. He attended Ursinus College originally intending to become a medical doctor. After graduating in 1897, Harvard University offered him a spot doing graduate work in biology. During his studies at Harvard, he took an interest in animal behavior and began studying comparative psychology. In 1902, Yerkes earned his Ph.D. in Psychology.
After graduating, Yerkes took a number of positions to pay the debts he had acquired while completing his education. He started as an assistant professor at Harvard teaching comparative psychology and taught courses in general psychology during the summer at Radcliffe College. He also took a part-time job as the director of psychological research at the Boston Psychopathic Hospital in Boston, Massachusetts.


In 1917, he was elected president of the American Psychological Association. After the U.S. entered World War I, Yerkes urged the APA to get involved in contributing psychological expertise to the war effort. A number of committees were formed, including one designed to measure intelligence in order to identify Army recruits who were particularly suited for special positions.
The work of the committee, which included psychologists such as Lewis Terman, Henry Goddard, and Walter Bingham, led to the development of the Army Alpha and Army Beta tests. The tests had been administered to approximately two million men by the time the war was over.
The tests are important in psychology history because they were the first group intelligence tests and helped popularize the concept of intelligence testing. The results of the tests were also used by eugenicists to advocate harsher immigration laws, since recent immigrants tended to score lower on the tests. While Yerkes suggested that the tests measure only native intelligence, the questions themselves clearly indicated that education and training had an impact on the results.

Contributions to Psychology:

Robert Yerkes contributed greatly to the field of comparative psychology. He founded the first primate research laboratory in the United States and served as its director from 1929 until 1941. The lab was later renamed the Yerkes National Primate Research Center.

His work with John D. Dodson led to the development of what is known as the Yerkes-Dodson Law. This law states that performance increases with arousal, but only up to a certain point. When arousal levels become to high, performance actually decreases.

While his use of eugenics to interpret the results of his intelligence tests was incorrect, his work in the field of intelligence testing also left a lasting mark on psychology.

Selected Publications by Robert Yerkes:

Yerkes, R. M., Bridges, J. W., & Hardwick, R. S. (1915). A point scale for measuring mental ability. Baltimore: Warwick & York.

Yerkes, R. M. (1916/1979). The mental life of monkeys and apes: a study of ideational behavior. Delmar, NY: Scholars' Facsimiles and Reprints.

Yerkes, R. M. (Ed.) (1921) Psychological examining in the United States Army. Memoirs of the National Academy of Sciences, 15, 1-890.

Yerkes, R. M. (1941). Man-power and military effectiveness: the case for human engineering. Journal of Consulting Psychology, 5, 205-209.

Yerkes, R. M. (1943, 1971). Chimpanzees: A laboratory colony. New York: Johnson Reprint Corporation.


Fancher, R. E. (1985). The intelligence men: Makers of the IQ controversy. New York: W. W. Norton & Company.

McGuire, F. (1994). Army alpha and beta tests of intelligence. In R. J. Sternberg (Ed.), Encyclopedia of intelligence (Vol 1, pp. 125-129.) New York: Macmillan.

Murchison, Carl. (Ed.) (1930). History of Psychology in Autobiography (Vol. 2, pp. 381-407). Republished by the permission of Clark University Press, Worcester, MA.

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