Wilhelm Wundt - Often considered the father of experimental psychology, Wundt established the first psychology laboratory in Leipzig, Germany, in 1879. He is known for his work on introspection and structuralism.

G. Stanley Hall - An American psychologist who founded the first psychology laboratory in the U.S. at Johns Hopkins University. He is also known for his work in developmental psychology and for establishing the American Psychological Association (APA).

William James - A leading figure in American psychology, James is known for his work on functionalism, which focuses on how mental processes help individuals adapt to their environment. His influential book, The Principles of Psychology, is a classic in the field.

Mary Whiton Calkins - An American psychologist who was the first woman to become president of the APA. She made significant contributions to the study of memory and the development of paired-associations technique.

Margaret Floy Washburn - The first woman to earn a Ph.D. in psychology, Washburn made significant contributions to the study of animal behavior and motor theory.

Sigmund Freud - The founder of psychoanalysis, Freud developed theories about the unconscious mind, defense mechanisms, and psychosexual development. His work has had a profound impact on psychology and psychiatry.

John B. Watson - Known for his role in the development of behaviorism, Watson conducted research on classical conditioning and argued that psychology should focus on observable behavior rather than internal mental states.

B.F. Skinner - A prominent behaviorist, Skinner is known for his work on operant conditioning and the use of reinforcement and punishment to shape behavior. He invented the Skinner box to study these principles.

Carl Rogers - A key figure in humanistic psychology, Rogers is known for his person-centered therapy, which emphasizes the importance of a supportive therapeutic relationship and the client’s self-concept.

Ivan Pavlov - Famous for his research on classical conditioning, Pavlov’s experiments with dogs demonstrated how stimuli can be associated with reflexive responses, laying the groundwork for behaviorist theory.

Jean Piaget - A Swiss psychologist known for his work on cognitive development in children. Piaget’s theory of developmental stages outlines how children’s thinking evolves from simple to complex processes.

Charles Darwin - Though primarily known as a naturalist, Darwin’s theory of evolution by natural selection has had significant implications for psychology, influencing the development of evolutionary psychology.

Dorothea Dix - An advocate for the mentally ill, Dix played a crucial role in the reform of mental health care institutions in the United States, working to improve conditions and treatment for individuals with mental illnesses.