19 Famous Psychologists and Their Theories

Famous psychologists
(Last Updated On: September 2, 2021)

Some of the most famous psychologists in history made important contributions to our understanding of the human mind and behavior. Some of these thinkers were also philosophers, educators, and therapists. While some became lightening rods for controversy, all of these thinkers had an impact on the field of psychology.

Learn more about some influential thinkers in psychology including their lives, their theories, and their major contributions to psychology.

Wilhelm Wundt

If you’ve ever taken an introductory psychology class, then you have probably spent at least a little time learning about Wilhelm Wundt. This German psychologist, physician and philosopher is best known for establishing the first psychology lab in Liepzig, Germany, officially marking the beginning of psychology as a field of science distinct from philosophy and physiology. In addition to being considered one of the founders of contemporary psychology, Wundt is also frequently referred to as the father of experimental psychology.

Originally a professor of physiology, Wundt wanted to apply the same experimental methods used in science to the study of the human mind. Wundt also had an influence on his students, including Edward Titchener who went on to establish a school of thought known as structuralism. Structuralism focused on studying human consciousness by breaking it down to the smallest possible elements.

Alfred Adler

Alfred Alder was an Austrian psychiatrist who is often considered one of the most influential thinkers in psychology. He became one of the most prominent members of the Vienna Psychoanalytic Society after Sigmund Freud extended an invitation, but he later became the first major figures to break away from Freud’s ideas. He developed a perspective that he called Individual Psychology. Adler had a major influence on other psychologists including Karen Horney, Carl Rogers, and Abraham Maslow.

William James

The philosopher and psychologist William James is widely regarded as the father of American psychology. Among his famous accomplishments was the publication of the 1200-page text, The Principles of Psychology, which quickly became a classic. Thanks to his teachings and writings, he helped establish psychology as a science. James also contributed to functionalism, pragmatism, and influenced many students of psychology during his 35-year teaching career.

Edward Thorndike

Edward Thorndike was an American psychologist who was associated with the school of thought known as functionalism along with other thinkers including Harvey Carr, James Rowland Angell and John Dewey. Thorndike is often called the father of modern day educational psychology and published several important texts on the subject.

Among his many accomplishments include being elected president of the American Psychological Association in 1912. In 1917, he was also one of the first psychologists to become a member of the National Academy of Sciences. Thorndike is also well-known for the puzzle box experiments he performed with cats, his concept of the law of effect, and his contributions to the field of educational psychology.

Sigmund Freud

No list of famous psychologists would be complete without an appearance by the eminent Sigmund Freud. Freud is often identified as one of psychology’s most famous psychologists, but he is also seen as one of the most notorious. While his ideas were often controversial, his concept of the unconscious mind has had a deep and lasting influence on psychology. His work gave rise to the field of psychoanalysis, which continues to be used in various forms as a treatment method to this day. Other important theories that he introduced include the id, the ego, the superego, psychosexual development, and the death instincts.

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Hugo Münsterberg

Hugo Münsterberg was a German psychologist and early pioneer of applied fields including industrial-organizational, forensic and clinical psychology. Münsterberg was studying medicine but after meeting Wilhelm Wunt, he turned his interest to the field of psychology.

William James later invited Münsterberg to take over the psychology lab at Harvard University, where he remained for three years before returning to Europe. He also served as the president of the American Psychological Association and taught a number of other prominent psychologists including Mary Whiton Calkins and Edward C. Tolman.

Münsterberg died on December 16, 1916 after suffering a massive cerebral hemorrhage right before he was set to deliver the opening remarks of a lecture at Harvard’s Radcliffe Institute for Advanced Study.

James McKeen Cattell

James McKeen Catell helped established psychology as a legitimate science and became the first psychology professor in the United States. Cattell started out studying English literature, but developed an interest in the field of psychology after meeting German psychologist Wilhelm Wundt. Cattell traveled to Germany to become Wundt’s assistant and later published the first psychology dissertation by an American.

After returning to the U.S., Cattell held a number of teaching positions and was influential in the formation of several major publications including The Journal of Science and The Psychological Review. In addition to helping advance psychology in the United States, Cattell also influenced other prominent psychologists including Edward L. Thorndike.

Mary Whiton Calkins

Mary Whiton Calkins is perhaps best-known as the first woman president of the American Psychological Association, but she made many more contributions to the field as well. Her experiences represent the difficulty and discrimination faced by many women in the early days of psychology. Despite fulfilling the requirements of a doctoral degree and receiving unanimous approval from a thesis committee that included William James, Josiah Royce and Hugo Munsterberg, Harvard refused to grant Calkins her degree because she was a woman.

Regardless of this, Calkins went on to have a successful and influential career in psychology. She invented the paired-associate technique, contributed to dream research, advocated self psychology, and wrote more than 100 professional papers on topics in both psychology and philosophy.

Mamie Phipps Clark

Mamie Phipps Clark was a pioneering female psychologist who is known for her important research on race and self-concept. Her work with her husband, psychologist Kenneth Clark, played a pivotal role in the Supreme Court’s ruling that segregation was unconstitutional in the famous Brown vs. the Board of Education case. While she is often overlooked or mentioned only in passing in psychology textbooks, her contributions to psychology are simply too important to ignore.

Anna Freud

Anna Freud was the youngest of Sigmund Freud’s six children. While she began her career influenced by the theories of her father, she was far from living in his father’s shadow. She made important contributions of her own to psychology, including founding child psychoanalysis, and summarizing the ego’s defense mechanisms in her book The Ego and the Mechanisms of Defense (1936).

Lev Vygotsky

Lev Vygotsky has only become one of the most famous psychologists in recent years. He is considered a seminal thinker in psychology, and much of his work is still being discovered and explored today. While he was a contemporary of Skinner, Pavlov, Freud and Piaget, his work never attained their level of eminence during his lifetime. Part of this was because his work was often criticized by the Communist Party in Russia, and so his writings were largely inaccessible to the Western world. His premature death at age 38 also contributed to his obscurity.

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Despite this, his work has continued to grow in influence since his death, particularly in the fields of developmental psychology and educational psychology. He is best known for his sociocultural theory and his concepts of the zone of proximal development and guided practice.

John Bowlby

John Bowlby was a British psychologist perhaps best known for developing attachment theory. His research on attachment and child development left a lasting impression on psychology, education, child care and parenting. Researchers extended his research to develop clinical treatment techniques and prevention strategies. His work also influenced other eminent psychologists, including his colleague Mary Ainsworth who also made major contributions to attachment theory.

Harry Harlow

American psychologist Harry Harlow is known for his infamous social isolation research conducted on rhesus monkeys during the late 1950s and early 1960s. At his primate lab located at the University of Wisconsin-Madison, Harlow performed a series of experiments in which infant monkeys were raised by surrogate “mothers.”

In different variations of the experiments, some of the mother monkeys were made entirely of wire while others were covered in a soft terrycloth. At the time, some researchers suggested that feeding was force behind the mother-child bond. The main idea behind this was that children love their caregivers because they provide food. What Harlow and his fellow researchers found was that the vital factor underlying an infant’s love for its mother was contact comfort. The infant monkeys in Harlow’s experiments preferred the soft terrycloth mothers over the wire mothers, even when the latter served as the source of food.

Harlow’s experiments played an important role in changing our understanding of attachment, but they were also extremely controversial. The experiments were both shocking and cruel, particularly his later experiments that involved placing young monkeys in total social isolation. Most of his experiments are considered unethical by today’s standards and the nature of his research contributed to concern and ethical regulations over how laboratory animals are treated.

Stanley Milgram

Stanley Milgram’s name is forever associated with his famous obedience experiment that demonstrated just how far people will go to obey and authority figure. During his graduate years, he had spent some time working as a research assistant for psychologist Solomon Asch. As you might remember, Asch conducted a series of experiments that demonstrated how people conform in social groups. The researcher helped spark and interest in the topic of obedience and conformity, ultimately leading Milgram to perform his controversial experiment.

An additional interesting bit of trivia: Milgram and psychologist Philip Zimbardo (of the Stanford Prison Experiment fame) were high school classmates.

Raymond Cattell

Raymond Cattell was an American psychologist whose work influenced psychology in a number of different ways. Not only did he introduce the concepts of fluid and crystallized intelligence, he is also well-known for his 16-factor model of personality. Perhaps his greatest achievement was his work pioneering the use of factor analysis and multivariate analysis. In one 2002 review, Cattell was ranked as the 16th most eminent psychologist of the twentieth-century.

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Edward B. Titchener

Edward B. Titchener was an influential figure in the formative years of psychology. As one of Wundt’s students, Titchener is perhaps best remembered for establishing the school of thought known as structuralism. This early viewpoint in psychology focused on breaking down human consciousness into the smallest possible elements. Researchers utilized a method known as introspection, which involved having trained observers describe the mental processes that occurred when they were presented with different stimuli.

Titchener is also known for coining the term empathy and for supervising the graduate studies of Margaret Floy Washburn, the first woman to earn a Ph.D. in Psychology. While Titchener served as a powerful force in psychology, the school of thought he helped establish did not survive long following his death in 1927.

Clark L. Hull

Despite facing considerable adversity, Clark Leonard Hull managed to overcome struggles with his health and finances in order to become one of the most important American psychologists of the 20th-century. His early life was marked by bouts of illness, including a severe case of typhoid fever. After polio left him paralyzed in his left leg, Hull decided to switch his career ambitions from engineering to psychology. While he found it necessary to halt his education several times due to lack of money, he eventually earned his Ph.D. and embarked on a long career as a teacher and researcher.

Hull is best remembered for his influence on behaviorism and his drive-reduction theory, but is also notable for his research on hypnosis and his emphasis on rigorous scientific methods.

George Kelly

George Kelly grew up poor and never actually graduated high school. Despite those obstacles, he went on to earn a doctorate in psychology and become an influential personality theorist. During the Great Depression, he set out to do something useful with his skills and started a traveling clinic that offered psychological services to people throughout his home state of Kansas.

During this time, he also formulated his personal construct theory of personality. According to Kelly, the differences between people result from the differing ways that they interpret and predict events in the world around them. He believed that we act much like scientists, forming hypotheses and conducting “experiments” to test our ideas about the world.

Ivan Pavlov

Ivan Pavlov had a major influence on psychology and is usually included in lists of famous psychologists, yet he actually wasn’t a psychologist at all. Pavlov was a Russian physiologist whose research on conditioned reflexes influenced the rise of behaviorism in psychology. Pavlov’s experimental methods helped move psychology away from introspection and subjective assessments towards more objective measurements of behavior. His most famous contribution was his discovery of classical conditioning, which continues to play a major role in our understanding of psychology and behavior to this day.

Final Thoughts On the Influence of These Famous Psychologists

This list represents just a sampling of some of the famous psychologists who have an a major impact on the field. In addition to historical figures, contemporary psychologists continue to leave their mark on the science of psychology.