Albert Bandura, one of the few icons on our list still living at the time of writing, is responsible for enormous contributions to the fields of psychology and education. Indeed, at 93 years of age (at the time of writing), Bandura is the most cited living psychologist. His greatest contributions have been in the areas of social and personality psychology. 

Sometimes identified as the Father of American psychology, James was the very first educator to offer a psychology course in the U.S. As one of the foremost philosophers and thinkers of the 19th Century, James enjoys a sterling reputation in modern psychology. He is considered one of the founding figures in functional psychology — a counterpoint to structuralism that attributes human behavior to Darwinian impulses of survival and utility.

Jean Piaget was a Swiss psychologist and genetic epistemologist. He is most famously known for his theory of cognitive development that looked at how children develop intellectually throughout the course of childhood.

Piaget was ranked as the second most influential psychologist of the 20th century in one 2002 study.