The document discusses several influential theories and definitions of intelligence from prominent psychologists throughout history. It describes Alfred Binet and Theodore Simon's Binet-Simon Scale from the 1890s, which aimed to measure intellectual development in children. It also discusses Charles Spearman's two-factor theory distinguishing between general intelligence ("g") and specific abilities ("s"). Additionally, it outlines Lewis Terman's revision of the Binet-Simon test called the Stanford-Binet Individual Intelligence Test in 1906 and Edward Thorndike's stimulus response theory from 1903 measuring intelligence through completion, arithmetic, vocabulary, and direction tests.