- Francis Galton (1822-1911) : Francis Galton one of the great scientist who was keenly interested in the measurement of individual differences, as influenced by his cousin, Charles Darwin. Galton was convinced that intellectual ability is inherited, and therefore recommended Eugenics, or the selective breeding of humans. He was the first to attempt to systematically measure intelligence, to use a questionnaire to gather data, to use a word-association test, to study mental imagery, to define and use the concepts of correlation and median, and to systematically study twins.