Richard E. Mayer is an American educational psychologist who has made significant contributions to theories of cognition and learning, especially as they relate to problem solving and the design of educational multimedia. Mayer's best known contribution to the field of educational psychology is multimedia learning theory, which posits that optimal learning occurs when visual and verbal materials are presented together simultaneously. He is the year 2000 recipient of the E. L. Thorndike Award for career achievement in educational psychology, and the winner of 2008 Distinguished Contribution of Applications of Psychology to Education and Training Award from the American Psychological Association. He was ranked #1 as the most productive educational psychologist in the world for 1991-2001 (Contemporary Educational Psychology, vol. 28, pp. 422–430). He is the author of more than 390 publications including 23 books, such as Multimedia Learning: Second Edition (2009), Learning and Instruction: Second Edition (2008), E-Learning and the Science of Instruction: Second Edition (with R. Clark, 2008), and the Cambridge Handbook of Multimedia Learning (editor, 2005). He received a PhD in psychology from the University of Michigan (1973), and served as a Visiting Assistant Professor of Psychology at Indiana University from 1973-1975. Mayer is Professor of Psychology at the University of California, Santa Barbara (UCSB) where he has served since 1975.