David W. Johnson is a professor of educational psychology at the University of Minnesota. He is Co-Director of the Cooperative Learning Center. He is the recipient of the 2003 Distinguished Contributions of Applications of Psychology to Education and Training Award from the American Psychologist Association. He held the Emma M. Birkmaier Professorship in Educational Leadership at the University of Minnesota from 1994 to 1997 and the Libra Endowed Chair for Visiting Professor at the University of Maine in 1996-1997. He received his master’s and doctoral degrees from Columbia University. He has authored over 400 research articles and book chapters. He is the author of over 40 books. He is a past editor of the American Educational Research Journal. He is the recipient of numerous awards for outstanding research and teaching from a wide variety of organiza-tions. He is an organizational consultant to schools and businesses and is a psychotherapist. Roger T. Johnson is a professor of curriculum and instruction at the University of Minnesota. He holds his doctoral degree from the University of California in Berkeley. He is the Co-Director of the Cooperative Learning Center. His public school teaching experience includes kindergarten through eighth grade instruction in self-contained classrooms, open schools, nongraded situations, cottage schools, and departmentalized (science) schools. He has consulted with schools throughout the world. He taught in the Harvard-Newton Intern Program as a master teacher. He was a curriculum developer with the Elementary Science Study in the Educational Development Center at Harvard University. For three summers, he taught classes in the British Primary Schools at the University of Sussex near Brighton, England. He has been honored with national awards from numerous organizations. He is the author of numerous research articles, book chapters, and books.