Sofie Loyens is an Assistant Professor in the Department of Psychology of Erasmus University Rotterdam, the Netherlands. Her research areas are conceptions of learning, constructivist learning and problem-based learning, conceptual change, motivation, and approaches to learning and study strategies. At Erasmus University, she coordinates the Educational Psychology course as well as the internships for Master's students.
Some of her recent publications include:

• Loyens, S. M. M., Rikers, R. M. J. P., & Schmidt, H. G. (2007). The impact of students' conceptions of constructivist assumptions on academic achievement and dropout. Studies in Higher Education, 32, 581-602.
• Loyens, S. M. M. (2007). Students' conceptions of constructivist learning. Doctoral dissertation. Rotterdam: Optima Grafische Communicatie.
• Loyens, S. M. M., Rikers, R. M. J. P., & Schmidt, H. G. (2007). Students' conceptions of distinct constructivist assumptions. European Journal of Psychology of Education, 12, 179-199.
• Schmidt, H. G., Loyens, S. M. M., Van Gog, T., & Paas, F. (2007). Problem based learning is compatible with human cognitive architecture: Commentary on Kirschner, Sweller, and Clark (2006). Educational Psychologist, 42, 91-97.

Dr. Mueller is Professor of Educational Research and of Public Policy and Public Administration at The George Washington University, Washington, DC, and former Chair of the Department of Educational Leadership. He is the co-editor of Structural Equation Modeling: A Second Course (2006, Information Age Publishing) and author of Basic Principles of Structural Equation Modeling: An Introduction to LISREL and EQS (1996, Springer-Verlag), among other writings. He is past chair of the American Educational Research Association's special interest group on SEM, serves on the editorial boards of several methodological and applied research journals, and conducts regular SEM training sessions for national and international audiences.