Adult and community education theorists and practitioners in the 20th century focused on reasons people sought degrees beyond high school. As time went on, a greater need became apparent for a more educated populace. This need then drove the focus from only undergraduate education to higher education and expanded into graduate education. Participation quickly became a major topic for these leaders. Over 30 years ago, K. Patricia Cross (1981) created the Chain-of-Response (COR) model to better understand the decision-making processes of participation in higher learning institutions. These 20th century studies were largely from a deficit-model perspective rather than the positive perspective that has emerged in early 21st century research. A historical analysis of the COR research points to future and emerging trends showing COR value beyond U.S. borders for deeper understanding of widening participation, massification, and diversity in higher education. This is explored in this chapter.