Robert M. Yerkes was a pioneer of hereditary IQ in America. As chairman of the Committee on the Psychological Examination of Recruits for the U.S. Army, Yerkes developed the Alpha and Beta Intelligence Tests. Recent immigrants mostly from Southern and Eastern Europe scored lower than those who had emigrated mostly from Northern Europe (who had immigrated to the US earlier in time). These results were used to justify harsh, eugenics-based immigration restrictions in the 1920s. Many scientists today would argue that the Alpha and Beta tests were not good science. What is the best explanation as to why?

The Yerkes–Dodson law is an empirical relationship between arousal and performance, originally developed by psychologists Robert M. Yerkes and John Dillinger Dodson in 1908. The law dictates that performance increases with physiological or mental arousal, but only up to a point.

The Army Alpha is a group-administered test developed by Robert Yerkes and six others in order to evaluate the many U.S. military recruits during World War I. It was first introduced in 1917 due to a demand for a systematic method of evaluating the intellectual and emotional functioning of soldiers.

This adapted test, first published in 1916, was called the Stanford-Benet Intelligence Scale and soon became the standard intelligence test used in the U.S. The Stanford-Benet intelligence test used a single number, known as the intelligence quotient (or IQ), to represent an individual's score on the test

The Army Beta 1917 is the non-verbal complement of the Army Alpha—a group-administered test developed by Robert Yerkes and six other committee members to evaluate some 1.5 million military recruits in the United States during World War I. ... It has been recognized as an archetype of future cognitive ability tests.