- 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.

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