Charles Edward Spearman, FRS was an English psychologist known for work in statistics, as a pioneer of factor analysis, and for Spearman's rank correlation coefficient. He also did seminal work on models for human intelligence, including his theory that disparate cognitive test scores reflect a single general intelligence factor and coining the term g factor.

Wilhelm Maximilian Wundt was a German physiologist, philosopher, and professor, one of the fathers of modern psychology. Wundt, who distinguished psychology as a science from philosophy and biology, was the first person ever to call himself a psychologist.