Roger N. Shepard, Professor of Psychology at Stanford University, is a particularly appropriate recipient for a prize dedicated to the “Theoretical Foundations of Human Cognition”. Throughout his research career, Roger Shepard has been searching for theoretical foundations of a science of the mind. His work attempts to specify such foundations in the form of universal laws formulated in an explicit mathematical manner, derivable from first principles, and which apply to human and to animal behaviour under a variety of tasks and stimulus sets. His endeavour to combine mathematical and physical modelling with quantified psychological experimentation has resulted in extraordinary advances in psychology. His work has opened up new research avenues in domains as varied as visual and auditory perception, mental imagery, representation, learning, and generalization. It is no exaggeration to state that several generations of psychologists have been influenced by the imagination and rigor that he has brought to psychological investigation. Indeed, many of the research paradigms that he has invented, from multidimensional scaling to mental rotation or guided apparent motion, continue to play a central role in current psychological investigations.