Robert Mearns Yerkes

Robert Yerkes ( 26 of maypole of 1876 – 3 of February of 1956 ) was a psychologist , ethologist and primatologist American known for his work in the field of intelligence test and comparative psychology . Yerkes was a pioneer in the comparative study of the intelligence of humans and primates, and the social behavior of gorillas and chimpanzees . Along with John D. Dodson, he developed the Yerkes-Dodson law , describing sexual arousal in behavior.

Studies and start of its race

Robert Yerkes was born in Breadysville , Pennsylvania , near Ivyland . He grew up on a farm where he developed his vocation for medicine. With the financial help of an uncle he attended Ursinus College between 1892 and 1897. After graduation he received an offer from Harvard University to do biology work. Between the doctor’s job in Philadelphia or going to Harvard, he chose the latter.

At Harvard Yerkes became interested in animal behavior to such an extent that he abandoned all medical practice to engage in comparative psychology . In 1902 he obtained his doctorate in psychology.

His beginnings were greatly influenced by the debts he must have incurred to pay for his studies. After graduating from Harvard, he was employed as an instructor and assistant professor of comparative psychology, and supplemented his income during the summers of many years teaching general psychology at Radcliffe College. He also developed other complementary work as director of psychological research at the Boston Psychopathic Hospital .

In 1907 Yerkes published his first book “The Dancing Mouse” . Among his friends at this time was future behavioral scholar John Watson , with whom he collaborated and exchanged ideas.

Intelligence tests

In 1917 Yerkes acted like president of the Association of North American Psychology, that under his direction initiated several programs dedicated to the war effort during the first World War . As head of the committee for psychological recruitment examinations, he developed the Alpha and Beta intelligence tests, the second of which was non-verbal, which was applied to more than one million soldiers during the war.

The test finally led to the conclusion that recent immigrants, especially those from southern and eastern Europe scored considerably less than the first waves of immigration in northern Europe, and was used as one of the eugenic causes for increasing immigration restrictions. The results were then heavily criticized because they clearly measured the degree of culture acquired, as they relate directly to the years of stay in the United States .

National Research Council

Immediately after World War I he worked as an employee of the United States National Research Council, where he conducted research on sexual issues. His research allowed him to establish relationships with members of the Rockefeller Foundation , later useful to raise funds for his project on chimpanzees.

Pioneer of primatology

Yerkes had a long history of fascination with chimpanzees. He spent time observing them in Cuba in the colony of Madame Abreu in the early 1920s, and returned from the determined trip to observe primates in their natural habitat. He began by acquiring two copies, Chim and Panzee, to a zoo . He took them to his house, where they slept in a bedroom and ate with cutlery at a small table. Chim was especially wonderful for Yerkes, and a summer that the monkey and Yerkes spent together was immortalized in his book “Almost Human”. 1

In 1924 Yerkes was appointed professor of psychobiology, a field in which he was a pioneer, at Yale University . He founded the Yale Primate Biology Laboratory in New Haven , then the Anthropoid Breeding and Experiment Station in Orange Park, Florida , with funds from the Rockefeller Foundation.


  • 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
  • 1916. The mental life of monkeys and apes
  • 1917a. The Binet version versus the point scale method of measuring intelligence. Journal of Applied Psychology 1, 111-122
  • 1917b. How can we discover the children who need special care. Mental Hygiene 1, 252-259
  • 1920. Army mental test (mit C. Yoakum)
  • 1921. Psychological examination in the United States Army Memoirs of the National Academy of Sciences, Bd. 15 (Herausgeber)
  • 1925. Almost human. The Century Co., New York
  • 1925. Chimpanzee intelligence and its vocal expressions (mit B. Learned)
  • 1927. The mind of a gorilla
  • 1929. The great apes (mit Ada Watterson Yerkes)
  • 1932. Yale Laboratories of Comparative Psychobiology . Baltimore: Johns Hopkins Press
  • 1941. Man power and military effectiveness: the case for human engineering. J. of Consulting Psychology 5, 205-209
  • 1943. Chimpanzees: A laboratory colony


  1. Back to top↑ Robert Yerkes, 1924, Almost Human .