The American psychologist Louis Leon Thurstone (1887-1955) was universally heralded as the most renowned psychometrician of his time. He led the way in mental measurement and testing through quantitative methods.

Louis Leon Thurstone, whose original family name was Thünström, was born on May 29, 1887, in Chicago. He attended school in various places in the United States as well as in Stockholm. In high school, at Jamestown, N.Y., he experimented with musical composition; mastered three typewriter keyboards; wrote a letter, published by Scientific American, on a problem of diversion of water from Niagara Falls; invented a method of trisecting an angle; and developed a talent for sketching into a lifelong hobby of photography. At Cornell University, from which he received an engineering degree, Thurstone designed a patented motion picture projector that was later demonstrated in the laboratory of Thomas Edison, with whom Thurstone worked briefly...