Karl Ludwig Bühler (May 27, 1879 - October 24, 1963) was a German psychologist and linguist. In psychology he is known for his work in gestalt psychology, and he was one of the founders of the Würzburg tradition of Psychology. In linguistics he is known for his Organon model of communication and his treatment of deixis as a linguistic phenomenon. He was the dissertation advisor of Karl Popper. His wife was the well-known psychologist Charlotte Bühler.

Bühler was born in Meckesheim. In 1899 he started medical school at the University of Freiburg, where he received his doctorate in 1903. He continued working as an assistant, and started taking a second degree in psychology graduating in 1904. In 1906 heworked as an assistant Professor at the University of Freiburg with von Kries, and as an assistant to Oswald Külpe at the Julius-Maximilians-University in Würzburg.

He completed his Habilitation thesis at Würzburg in 1907, with the title "Tatsachen und Probleme zu einer Psychologie der Denkvorgänge" (Facts and problems of a psychology of thought processes). This text became foundational for the Würzburg school in Psychology and sparked heated controversy with Wilhelm Wundt. In 1909 Bühler changed to the University of Bonn, becoming the assistant to Oswald Külpe.

Carl Ransom Rogers (January 8, 1902 – February 4, 1987) was an influential American psychologist and among the founders of the humanistic approach to psychology. Rogers is widely considered to be one of the founding fathers of psychotherapy research and was honored for his pioneering research with the Award for Distinguished Scientific Contributions by the American Psychological Association in 1956.

The person-centered approach, his own unique approach to understanding personality and human relationships, found wide application in various domains such as psychotherapy and counseling (client-centered therapy), education (student-centered learning), organizations, and other group settings. For his professional work he was bestowed the Award for Distinguished Professional Contributions to Psychology by the APA in 1972. Towards the end of his life Carl Rogers was nominated for the Nobel Peace Prize for his work with national intergroup conflict in South Africa and Northern Ireland. In a study by Haggbloom et al. (2002) using six criteria such as citations and recognition, Rogers was found to be the sixth most eminent psychologist of the 20th century and second, among clinicians, only to Sigmund Freud.

Abraham Harold Maslow (April 1, 1908 – June 8, 1970) was an American professor of psychology at Brandeis University, Brooklyn College, New School for Social Research and Columbia University who created Maslow's hierarchy of needs. He stressed the importance of focusing on the positive qualities in people, as opposed to treating them as a 'bag of symptoms.'

Born and raised in Brooklyn, New York, Maslow was the oldest of eight children and was classed as "mentally unstable" by a psychologist. His parents were first generation Jewish immigrants from Russia who were not intellectually oriented but valued education. Maslow's parents immigrated to the U.S. in the beginning of the 1900s in order to flee from Czarist persecution, similar to many European coreligionists and to have a more prosperous life financially.

It was a tough time for Maslow, as he experienced Anti-semitism from his teachers and from other children around the neighborhood. He had various encounters with anti-semitic gangs who would chase and throw rocks at him. Maslow and other optimistic youngsters at the time with his background were in the struggle to overcome such acts of racism and ethnic prejudice in the attempt to establish an idealistic world based on widespread education and monetary justice. The tension outside of his home was also felt within it, he rarely got along with his mother, and eventually developed a strong revulsion to her. He is quoted as saying: {{quote|What I had reacted to was not only her physical appearance, but also her values and world view, her stinginess, her total selfishness, her lack of love for anyone else in the world – even her own husband and children – her narcissism, her Negro prejudice, her exploitation of everyone, her assumption that anyone was wrong who disagreed with her, her lack of friends, her sloppiness and dirtiness...

Stanley Krippner (born October 4, 1932) is an American psychologist, and an executive faculty member and Professor of Psychology at Saybrook University in San Francisco. Formerly, Krippner was director of the Kent State University Child Study Center (of Kent, Ohio), and director of the Maimonides Medical Center Dream Research Laboratory (of Brooklyn, New York).

Krippner is an internationally known humanistic psychologist, having written extensively on dreams, altered states of consciousness, hypnosis, shamanism, dissociation, and parapsychological subjects. Krippner was an early leader in Division 32 of the American Psychological Association, the division concerned with humanistic psychology, serving as President of the division from 1980 - 1981. He also served as president of division 30, the Society for Psychological Hypnosis, and is a Fellow of four APA divisions.

In 2002, Krippner received the American Psychological Association (APA) Award for Distinguished Contributions to the International Advancement of Psychology. Other awards from the APA include the Award for Distinguished Contributions to Professional Hypnosis (2002), Senior Contributor Award (Division 17, Counseling Psychology) (2000), and the Charlotte and Karl Buhler Award (Division 32, Humanistic Psychology) (1992). Krippner also received The International Association for the Study of Dreams (IASD) Lifetime Achievement Award (2006), The Parapsychological Association's Outstanding Career Award (1998), The Dr. J.B. Rhine Award for Life-Time Achievement in Parapsychology (Andhra University, Visakhapatnam, India) (2002), the Pathfinder Award from the Association for Humanistic Psychology (1998), and the University of Georgia Bicentennial Award (1985).