In history, there were many successful psychologists who have made large contributions to the world of psychology. Many of which who are alive, and dead. Three of the most important psychologists are Carl Rogers, Neal Miller, and Kurt Lewin; all in which made a contribution to psychology somehow or another. Carl Ransom Rogers was an influential American psychologist and among the founders of the humanistic approach to psychology. Rogers was widely considered to be one of the founding fathers of psychotherapy research and was honored for his pioneering research with the Distinguished Scientific Contributions by the American Psychological Association in 1956. His theory, as of 1951, was based on nineteen propositions; here are a few to give an idea of the basis of them all: All individuals exist in a continually changing world of experience of which they are the center. A portion of the total perceptual field gradually becomes differentiated as the self, and emotion accompanies and in general facilitates, such goal directed behavior, the kind of emotion being related to the perceived significance of the behavior for the maintenance and enhancement of the organism. All these have to do with the emotions and personality of a person, and how the brain works at perceiving the emotions as well. With the regard to development, Rogers described principles rather than stages. The main issue is the development of a self concept and the progress from an undifferentiated self to being fully differentiated, for instance, self concept. It means gestalt which is available to awareness though not necessarily in awareness. It is a fluid and changing gestalt, a process, but at any given moment it is a specific entity. Rogers took the aspects of how a person perceives their emotions by doing multiple studies, and tests to diagnos their emotional status.