Peter F. Drucker has been Clarke Professor of Social Science and Management at Claremont Graduate School in California since 1971.Maureen Cox is Reader in Psychology at the University of York. She has published eight books including Visual Order: The Nature and Development of Pictorial Presentation (edited with N. H. Freeman, Cambridge, 1985), The Child's Point of View: The Development of Cognition and Language, 2nd edition (1991), Children's Drawings (1992), and Teaching Young Children to Draw (with G. Cooke and D. Griffin, 1998).