In the preschool years, children acquire the ability to understand what other people think and feel (Theory of Mind). They also become able to think and act much more flexibly. This book summarises research on the developmental relation between theory of mind and executive functioning and presents several studies examining this parallel developmental progress as exemplified by correlations between the false belief task (Wimmer & Perner, 1983) and the Dimensional Change Card Sorting task (DCCS task; Frye, Zelazo, & Palfai, 1995). These studies show that young children have particular problems to think differently about one and the same thing. Furthermore, a short training study is described showing that both theory of mind and flexibility can be trained. Providing a comprehensive theoretical and experimental account of important developmental advances in the preschool years, the book will be of great interest to both students and researchers in developmental psychology.