Which researcher studied life development of Harvard graduates over a 50-year span?

The researcher who studied the life development of Harvard graduates over a 50-year span is Daniel Levinson. His work focuses on adult development and the life structure of adults across different stages of life. Levinson's research involved intensive interviews and assessments that tracked the lives of men who graduated from Harvard, and he developed a well-regarded theory of adult development that emphasizes how people transition through various life phases, making decisions and facing challenges. His findings contributed significantly to our understanding of adult psychological and emotional growth, emphasizing that development is a continuous process that occurs over a lifetime. The other researchers mentioned have made notable contributions in their fields, but their work is not centered on the longitudinal study of Harvard graduates.