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.

Granville Stanley Hall was a pioneering American psychologist and educator who earned the first doctorate in psychology awarded in the United States of America at Harvard College in the nineteenth century. His interests focused on human life span development and evolutionary theory. Hall was the first president of the American Psychological Association and the first president of Clark University. A Review of General Psychology survey, published in 2002, ranked Hall as the 72nd most cited psychologist of the 20th century, in a tie with Lewis Terman. .