The varied findings and approaches reported reveal that contemporary comparative research on mental development is in a phase of differentiation and integration. Far from being global and fused, this comparative study is a flowering field of diverse disciplinary approaches, empirical phenomena, scholarly topics, and theoretical perspectives. It focuses on the comparative phylogeny, ontogeny, and history of mentation-most notably on the comparative onset and offset ages, velocity, extent, sequencing, organization of thought, symbol, and value development. The world's leading authorities on the subject discuss the implications of the study of evolution for our models of the ontogenetic origins, development, and history of mentation, as well as determine the constraints that evolution imposes on mental development. Bringing the current interest in primate cognition to bear on studies of cognitive development in humans, this book will be of interest cognitive developmentalists, primatologists and comparitive psychologists.