Final answer:
The MI co-founder who made the statement about people being the experts on themselves and the role of the helper in MI is William R. Miller. Abraham Maslow is known for his hierarchy of needs, while Carl Rogers developed the theory of the self-concept.
Step-by-step explanation:
The co-founder of Motivational Interviewing (MI) who stated that "People are the undisputed experts on themselves. No one has been with them longer or knows them better than they do themselves. In MI, the helper is a companion who typically does less than half of the talking" is William R. Miller. Motivational Interviewing is a collaborative, goal-oriented style of communication with particular attention to the language of change. It is designed to strengthen personal motivation for and commitment to a specific goal by eliciting and exploring the person's own reasons for change within an atmosphere of acceptance and compassion.
Abraham Maslow is most well-known for proposing his hierarchy of needs, which is a theoretical framework in psychology, while Carl Rogers developed the theory of the self-concept and was a major contributor to humanistic psychology. Both Maslow and Rogers have influenced many scholars and are celebrated for their unique contributions to psychology, particularly in relation to the study of the self and personal growth.