B.F. Skinner- Skinner believed that the only scientific approach to psychology was one that studied behaviors, not internal mental processes. He denied the existence of a mind as a thing separate from the body, but he did not deny the existence of thoughts, which he regarded simply as private behaviors to be analyzed according to the same principle as publicly observed behaviors. B. F. Skinner was one of the most influential of American psychologists. A radical behaviorist, he developed the conditioning idea that behavior is determined by its consequences, be they reinforcements or punishments, which make it more or less likely that the behavior will occur again.

Jean Piaget- Jean Piaget's work had a profound influence on psychology, especially our understanding children's intellectual development. His research contributed to the growth of developmental psychology, cognitive psychology, genetic epistemology, and education reform. Albert Einstein once described Piaget's observations on children's intellectual growth and thought processes as a discovery "so simple that only a genius could have thought of it."

Sigmund Freud- When people think of psychology, many tend to think of Freud. His work supported the belief that not all mental illnesses have physiological causes and he also offered evidence that cultural differences have an impact on psychology and behavior. His work and writings contributed to our understanding of personality, clinical psychology, human development, and abnormal psychology.

Albert Bandura- Bandura's work is considered part of the cognitive revolution in psychology that began in the late 1960s. His social learning theory stressed the importance of observational learning, imitation, and modeling. "Learning would be exceedingly laborious, not to mention hazardous, if people had to rely solely on the effects of their own actions to