Home > Psychologists and Their Theories > Yerkes, Robert Mearns - Introduction

Introduction

1876–1956

AMERICAN COMPARATIVE PSYCHOLOGIST, RESEARCHER

HARVARD UNIVERSITY, Ph.D., 1902

Robert Mearns Yerkes was a leading figure in comparative psychology, a branch of psychology that studies animal behavior and often makes comparisons from species to species. The ultimate goal is to find general principles that may sometimes shed light on human behavior. Yerkes published several books on the subject. Among them was The Great Apes: A Study of Anthropoid Life, an influential book he coauthored with his wife, Ada Watterson Yerkes. He also started the first U.S. scientific journal devoted solely to the study of animal behavior. In 1929, Yerkes founded the Yale Laboratories of Primate Biology, the first laboratory for nonhuman primate research in the United States. The laboratory was later renamed the Yerkes National Primate Research Center.

Early in his career as an animal researcher, Yerkes also worked with John Dodson to develop the Yerkes-Dodson law. This law originally related the strength of a stimulus to the speed of avoidance learning in mice. It has since been used, however, to explain the effect of arousal on human performance. The basic idea is that there is an optimal level of arousal for the best performance on any task, and this level depends upon the task's difficulty.

In addition, Yerkes played a major role in the rise of human intelligence testing. During World War I, he headed a committee that developed the first group intelligence tests, which were used to assess Army recruits. These tests, known as the Army Alpha and

Beta tests, captured the public's interest. After the war, when Yerkes and others promoted the use of group tests in the general population, they found a ready market. Their tests became the forerunners of standardized tests such as the SAT.

The Alpha and Beta tests had been given to some 1,750,000 Army recruits during the war. Afterward, this huge trove of data was studied intensely. Yerkes's own analyses led him to controversial conclusions about apparent racial and ethnic differences in intelligence. They also raised alarms about a supposed decline in the nation's brainpower. These conclusions have since been refuted on several grounds; at the time, however, they fueled much social debate and helped lead to laws limiting immigration.